the month in snapshots

when we're sick, all we wanna do is snuggle

she looks pretty good in Chloe's old duck onesie

she digs wearing blocks on her head

she's in a great mood... after naps.

an evening at the Shawnee Woods Haunted Trail!

just a few candid shots courtesy of the wife

she's full of laughter!

she loves to be thrown

sister love!

Halloween! Chloe did her makeup all by herself!
(except the eyes, which Ash helped with)

the year in books [XXI]

This year I read a number of books set against the naturalistic theory of evolution (i.e. origin of species by unguided natural forces). These books highlighted the apparent design and fine-tuning of our universe, the mathematical improbabilities (some mathematicians would call them 'impossibilities') of life originating randomly and then evolving randomly, and a host of other difficulties that the naturalistic theory of evolution has yet to overcome. Most fascinating to me was the static nature of the fossil record: fossil creatures show up fully formed, fully functional, and perfectly designed for their intermediates; 'transitional fossils' are transitional only from a subjective point-of-view. These were great books that highlight the difficulties of our current understanding of evolution, but none of them endorse the 'Answers in Genesis' approach to cosmology. I tend towards Old Earth Creationism or Theistic Evolution (in which 'evolution' is a guided process).

the year in books [XX]

I picked up Leviathan Wakes a few months ago because I'd heard great things about it. Good science fiction can be hard to find, so the Expanse Series is a goldmine. The first book had me hooked, and I've been plowing through them with wild abandon. The Expanse is set apart from most other science fiction books because it's gritty, raw, and it looks at a possible future in which humanity remains explicitly human. Science fiction books - at least those set in the far future - tend to take on a utopian atmosphere, in which humankind has made leaps and bounds and has transcended into a higher consciousness. Not so with The Expanse: we're still just a bunch of scared, foolish, stupid hairy apes trying to make sense of the world as we satisfy our more banal natures. There are nine novels set in the Expanse universe, along with a handful of novellas (I include the first six of each here). If you're into science fiction, this series is a no-brainer. Five big-ass stars!

The Ichthyosaurs

Ichthyosaurs (‘fish lizards’) thrived during the Mesozoic, appearing around 250 mya and surviving (at least in one species) until the Upper Mesozoic. Ichthyosaurs are one of the most notable Mesozoic reptiles, seconded only by the plesiosaurs of Loch Ness fame. Ichthyosaurs resembled modern fish and dolphins and ranged from one to over fifty feet in length (one species reached nearly seventy feet long). Unlike nothosaurs, their limbs were fully transformed into flippers that could contain a wide array of fingers. Some species had a dorsal fin, and most used a more vertical tail fin for powerful propulsive strokes. Ichthyosaurs had short necks, and later species had stiff trunks. The vertebral column, made of simplified disc-like vertebrae, continued into the lower lobe of the tail fin. Ichthyosaurs had pointed heads and large eyes, which would’ve been useful when diving. Ichthyosaurs were warm-blooded, breathed air, and bore live young.

Temnodontosaurus was a beast

Typical ichthyosaurs had bony rings protecting their eyes, suggesting that they may have hunted at night or at great depths – and their large eyes would’ve been useful for such hunting. Temnodontosaurus, with eyes twenty-five centimeters in diameter, could probably see objects as deep as 1600 meters (one mile!) down. Shockingly, Opthalmosaurus, with even larger eyes, may have been able to go deeper than a mile into the ocean depths. The only living animals with similarly large eyes are the giant and colossal squids. Despite having such robust eyes, they likely had poor hearing, given the nature of their middle ear bones. They may have made up for bad hearing with an acute sense of smell, or they may have possessed electro-sensory organs like those seen in modern sharks, rays, and dolphins; these adaptations could explain the grooves in ichthyosaur palates. Further evidence of deep diving has been the presence of bone necrosis in about twenty percent of Jurassic and Cretaceous remains. Quick ascent from great depths can cause decompression sickness, which can be seen in the resulting bone necrosis. Because this bone necrosis is rare in Triassic species, some paleontologists have argued that the Triassic forms didn’t take to diving like their descendants. Other scientists argue that the lack of bone necrosis doesn’t indicate a lack of deep diving but a lack of rapid ascension: in the Jurassic and Cretaceous, ichthyosaurs were face-to-face with monstrous, fast-moving predators – such as mosasaurs and plesiosaurs – that could attack them in the depths and force them to make a rapid ascent (resulting in the accumulation of bone necrosis). Triassic ichthyosaurs, lacking such predators and dominating the marine food web, could afford to lazily and luxuriously ascend to the surface to breathe. A flaw in this theory is that modern diving animals show bone necrosis not from an accumulation of rapid ascents but as the general degeneration caused by a diving lifestyle. 

a feeding frenzy

Ichthyosaurs were carnivorous and adapted to a variety of lifestyles. Species with pointed snouts were designed for grabbing smaller animals; some forms with protruding jaws may have used their pointy snouts to slash prey like modern swordfish. Early ichthyosaurs were durophagous: their flat convex teeth were designed for crushing shellfish; other early ichthyosaurs may have been suction-feeders, sucking animals into their mouths by quickly opening their short jaws (recent studies, however, indicate that those species thought to be ‘suction feeders’ were more likely ‘ram feeders’ who gathered food by constantly swimming forward with a mouth wide-open). Preserved gut contents tell us that most ichthyosaurs fed on cephalopods (such as squid); others fed on fish and even smaller ichthyosaurs. Some ichthyosaurs were apex predators with large, bladed teeth and adaptations for killing large prey. Ichthyosaurs weren’t averse to scavenging and would eat drowned animals swept out to sea: in 2003 a specimen of the Cretaceous Platypterygius had eaten fish, a turtle, and a land bird. Ichthyosaurs hunted – and were hunted. During the Triassic they had to evade sharks and other ichthyosaurs. In the Jurassic they were hunted by the marine crocodylomorphs and the plesiosaurs (in 2009 a plesiosaur specimen was found with an ichthyosaur embryo in its gut). Another discovery, this one of a large ichthyosaur close to thirty feet long, showed a tail that had been recently bitten off; researchers theorized, given the presence of an ammonite shell in its throat region, that the ichthyosaur was ambushed and attacked, likely by a pliosaur (known from the same habitat), which severed its tail. The ichthyosaur, stripped of its means of locomotion, sank to the depths and drowned (ichthyosaurs, remember, were air-breathers).

an ichthyosaur is about to become a predator's lunch

a pod of dolphin-like ichthyosaurs

Gregarious behavior – or social behavior indicative of a social lifestyle – has been assumed. The assumption comes easy, given ichthyosaurs’ resemblance to dolphins who have a rich social life. Fossil evidence of such behavior, however, isn’t super strong. Though there is evidence of social dimorphism in some species, it isn’t the case across the board (social dimorphism, or slight variations between males and females of the same species, is usually a good indicator of gregarious behavior). Social behavior has also been argued by the fact that ichthyosaurs gave birth to live young who would likely need to be raised to adulthood. Some scientists point to the fossilized remains of an ichthyosaur with bite marks to the snout region as further evidence of gregarious behavior. Analyses of the healed bite marks indicate that they were made by another ichthyosaur of the same species; perhaps these were two males fighting over mates? 

Ichthyosaurs likely emerged during the Triassic (though some scientists speculate, given the sudden diversity of Triassic ichthyosaurs, that they may have emerged as far back as the Upper Permian). It’s believed that ichthyosaurs, like modern whales and dolphins, developed from terrestrial land-animals that returned to the sea. While dolphins and whales evolved from land mammals, ichthyosaurs evolved from land reptiles (though a minority of scientists argue that they came from land amphibians). Because there are so many dissimilarities between the earliest ichthyosaurs and their hypothesized ancestor, ichthyosaur origins continue to be hotly debated. What is generally known (or believed) is that the ichthyosaurs, despite sharing the Mesozoic oceans first with nothosaurs and then with plesiosaurs, comes from a wholly different lineage than those two Sauropterygian groups (the mosasaurs, who coexisted with ichthyosaurs for a time, also had a unique lineage from aquatic lizards). A boom to ichthyosaur origins took place in 2014 when a small basal ichthyosauriform from the Early Triassic was found in China; this creature had characteristics suggesting a semi-aquatic rather than fully-aquatic lifestyle, and it’s been hailed as a missing ‘transitional link’ between land-dwelling reptiles and ‘true’ ichthyosaurs.

Utatsusaurus

The earliest ichthyosaurs emerged in the Olenekian and Anisian stages of the early Triassic (at least according to most scientists). These early forms include Chaohusaurus, Grippia, and Utatsusaurus. Their diversity suggests an earlier origin than the fossil record has told us, which is why some scientists place their emergence as far back as the Late Permian (though most hold to an Early Triassic emergence due to the fact that the Permian-Triassic Extinction rendered the oceans anoxic and would’ve likely killed off any ichthyosaurs with a Permian start-date). These early ichthyosaurs looked more like finned lizards than the fish- and dolphin-like species of the later Mesozoic. Their bodies were elongated and they likely propelled themselves through the water by undulating their entire trunk. Their pectoral girdles and pelves were robustly built, and their vertebrae possessed the interlocking processes used to support the body against the force of gravity (all of which are seen in terrestrial animals). That they weren’t semi-aquatic is evidenced in the fact that their limbs had been completely transformed into flippers. These, like later ichthyosaurs, were likely warm-blooded and viviparous (giving birth to live young). Because these early ichthyosaurs, despite their variations, have such a distinct built when compared to later ichthyosaurs, some paleontologists class them as ‘proto-ichthyosaurs’ and classify them as the Ichthyopterygia. 

a pair of Cymbospondylus

These Early Triassic forms gave rise to ‘true ichthyosaurs’ sometime around the early Middle Triassic. These ichthyosaurs, like their predecessors, displayed a wide range of variation. There was Cymbospondylus, for example, which resembled a thirty-foot sea-serpent, compared to the more ‘proper’ (albeit smaller) Mixosaurus. The Mixosauria were fish-like with a pointed skull, a shorter trunk, a more vertical tail fin, a dorsal fin, and short flippers. Mixosauria’s sister group, Merriamosauria, diversified into the large and classic-looking Shastasauria and the dolphin-like Euichthyosauria. Euichthyosaurs had more narrow front flippers with a reduced number of fingers, and they include species such as Californosaurus and Toretocnemus. Then there were the Parvipelvia, who had a reduced pelvis (hence the name), and they included species such as Hudsonelpidia and Macgowania. 

the wide-bellied Shonisaurus hanging with smaller ichthyosaurs

In the Late Triassic, the Shastosaurs reached epic sizes. Shonisaurus was fifty feet long; Himalayasaurus was thirty feet long; and Shastasaurus sikanniensis may have reached up to seventy feet in length (if this is correct, it was the largest marine reptile known). It was during the Late Triassic that ichthyosaurs reached the peak of their diversity, dominating numerous ecological niches. Some were top predators while others fed on smaller prey. Some may have specialized as suction or ram feeders. Towards the end of the Late Triassic, variability began to decline. The giant species disappeared, perhaps due to increased competition by sharks, ray-finned fishes, and the emerging plesiosaurs.

After the Triassic-Jurassic Extinction, plesiosaurs had a head-start in diversification and overwhelmed the ecological niches that ichthyosaurs had dominated – but this didn’t mean ichthyosaurs were squeezed out entirely. There were still many large ichthyosaurs that reached up to thirty feet in length. Because most early ichthyosaur discoveries were species from the Jurassic, some of these early Jurassic species have become household names, such as Ichthyosaurus. Nevertheless, the ichthyosaurs of the Early Jurassic weren’t as varied as they had been in the Late Triassic; they didn’t grow as large, and suction/ram feeders and durophagous species (those who subsisted on shellfish) disappeared. Early Jurassic ichthyosaurs were streamlined, dolphin-like forms. An odd-ball of the time was the Thunnosauria, a group of ichthyosaurs that adapted thunniform locomotion, propelling themselves with the end of the tail only, which had a vertical tail fin. Another odd-ball group were the Eurhinosauria, who were specialized forms with very elongated and pointy snouts. The fossil record gets shady in the Middle Triassic, which isn’t necessarily problematic (the Middle Jurassic tends to have a spotty fossil record). When we get to the Late Jurassic, there are indications that a further decrease in diversity took place in the shadows of the Middle Jurassic. All ichthyosaurs belonged to an off-branching line of the thunnosaurs, the Opthalmosauria. The most famous of these Late Jurassic ichthyosaurs was Opthalmosaurus; these had monstrous eyes and likely hunted in dark, deep water. 

the wide-eyed Opthalmosaurus

Though ichthyosaurs had worldwide distribution in the Cretaceous, there is an apparent continuation of decreasing diversity. For decades it was believed all fossils referred to a single genus, Platypterygius. Traditionalists have placed ichthyosaur extinction in the Early Cretaceous about 95 million years ago, making them the first to go among the other Mesozoic reptiles such as the plesiosaurs and the mosasaurs. Two theories emerged to explain their disappearance: first, maybe they were just unlucky; second, perhaps they just didn’t have what it took to compete with other Cretaceous aquatic animals, such as the mosasaurs and plesiosaurs. Fast-swimming and highly-evasive ray-finned fishes could dominate feeding grounds and easily escape their more cumbersome ichthyosaur predators, and the ambush strategies of the mosasaurs were superior to those of the ichthyosaurs. Or perhaps, some argue, they became too specialized: the more specialized a creature becomes, the more at risk it is of extinction, as environments are in a continual state of flux. ‘Evolutionary stagnation’ has been the death-knell for many species throughout our planet’s history. But maybe, some paleontologists speculate, we got it all wrong. Recent scientists have argued that fragmentary remains attributed to Platypterygius may in fact represent more diverse species. In 2012 it was shown that at least eight ichthyosaur lineages spanned the Jurassic-Cretaceous boundary; why would all but one go extinct? The next year, 2013, a thunnosaurian ichthyosaur, Malawania, was discovered. These discoveries have led many scientists to postulate that ichthyosaurs didn’t decline in the Early Cretaceous but actually diversified as more coastlines opened up due to the plodding but continuous break-up of the continents.

Nevertheless, ichthyosaurs did die out well before their Mesozoic counterparts. Recently this has been viewed as a two-stage process. The first extinction event eliminated two of the three ichthyosaur ‘feeding guilds’: the ‘soft-prey specialists’ and the ‘generalists,’ leaving only an apex predator group. The second extinction event took place during the Cenomian-Turonian boundary event (in the early stages of the Upper Cretaceous). This ‘anoxic event,’ in which the oceans suffered a decrease in available oxygen, led to the demise and eventual wipe-out of the apex ichthyosaurs. Though Platypterygius survived into the later Cretaceous, it disappeared around 93 million years ago, well before the mosasaurs and plesiosaurs (both of whom would meet their maker in the Cretaceous-Tertiary Extinction). This two-stage process of ichthyosaur demise is attributed not to competition in the ocean but to environmental factors, such as changes in migration, food availability, and birthing grounds. Concurrent with the ichthyosaur demise was a variety of other marine extinctions, hinting at ecological factors: microplankton, ammonites, and reef-building bivalves suffered greatly. When the ichthyosaurs disappeared, mosasaurs diversified into larger forms that filled the ecological niches left vacant. 

The Plesiosaurs

Most grade school children can identify a plesiosaur if they see one, even if they incorrectly call it a dinosaur (no dinosaurs, to our knowledge, became aquatic). Plesiosaurs were marine reptiles that thrived during the Mesozoic Era; though living in tandem with terrestrial dinosaurs, they were not dinosaurs themselves. Plesiosaurs first appeared in the Triassic Period around 200 million years ago; they diversified and thrived in the Jurassic and Cretaceous before going extinct at the Cretaceous-Tertiary Extinction Event (known in parlance as the K-T Event) some sixty-six million years ago. Over a hundred species have been discovered, giving paleontologists a fantastic window through which to study them and the world they inhabited.

Attenborosaurus flaunting its tail fluke

Plesiosaurs generally had flat bodies and short tails, and their limbs had evolved into four long flippers. The flippers were powered by strong muscles attached to wide bony plates formed by the shoulder girdle and pelvis. All four limbs were used to propel the animal through the water by up-and-down movements; the flippers gave plesiosaurs a ‘flying movement’ through the water, and their tails likely served for directional control (in contrast with ichthyosaurs and the Cretaceous mosasaurs, who used their tails for propulsion). One species of plesiosaur, Attenborosaurus, had a vertical tail fin that would be difficult to fossilize; a possibility of a tail fluke, at least in some species, has been confirmed by recent studies on the caudal neural spines of multiple plesiosaurs. Plesiosaurs were reptiles; as such they breathed air with lungs rather than gills. Oddly enough for reptiles, they gave birth to live young and were likely warm-blooded. Recent computer simulations indicate that plesiosaurs could swim up to 1.8 km/hr if they were cold-blooded and 5.4 km/hr if warm-blooded; thus they were far slower than modern whales, twenty percent slower than the most advanced ichthyosaurs, but five percent faster than the Cretaceous mosasaurs (this speed benefit, however micro, would be helpful, as we have fossilized clues that mosasaurs liked to dine on plesiosaurs). Plesiosaurs come in two main morphological types: the ‘plesiomorph’ build consisted of long necks and small heads; these ‘plesiosaurs’ were relatively slow and fed on small sea animals. The ‘pliosauromorph’ build consisted of short necks and long heads; these ‘pliosaurs’ were the top marine predators, fast hunters of large prey. The Plesiosauria group reflects these morphological types in the group’s subdivision into the long-necked Plesiosauroidea and the short-necked Pliosauridea. 

Plesiosaurs belonged to the Sauropterygia, a group that consists of marine reptiles with terrestrial origins. At some point shortly after the Permian-Triassic extinction, some land-loving reptiles began returning to the sea. An early thread of sauropterygians broke into two branches during the Late Triassic: the Pistosauria and the Nothosauridae (it’s worth noting that many scientists believe that the Nothosaur lineage gave rise to the plesiosaurs rather than the plesiosaurs and nothosaurs arising from a common ancestor). Those creatures belonging to Pistosauria became more adapted to marine life than their nothosaur cousins; the pistosaurs sported stiffened vertebral columns and hands and feet that turned into full-fledged flippers (unlike the nothosaurs, whose hands half-assed the aquatic lifestyle by evolving webbing between the fingers and toes). At some point the pistosaurs became warm-blooded and viviparous (giving birth to live young). The earliest pistosaurians were coastal animals, but later developments enabled some to split off into the wider ocean. This was made possible by reinforced shoulder girdles, flatter pelvises, stiffer joints, shorter tails, and more pointed plesiosaurs. These ‘deep ocean’ pistosaurs are known as the plesiosaurs. Though nothosaurs likely stuck to the coasts, plesiosaurs lived a little more dangerously by venturing deeper into the oceans. Plesiosaurs started off small (one of the earliest plesiosaurs, Thalassiodracon, was only six feet long) but bloomed big by the end of the Cretaceous (Mauisaurus reached fifty-five feet in length). 

the titanic Mauisaurus

Several species of plesiosaur show up in early Jurassic fossil beds, hinting that they diversified as early as the Late Triassic. Plesiosaurs in the early Jurassic were at most sixteen feet long, but by the cusp of the Middle Jurassic they were more numerous and some species developed longer necks (some species reached up to thirty-three feet in length). In the Middle Jurassic, behemoth pliosaurs evolved: they had large heads and short necks, and included such forbidding species as Liopleurodon (which reached up to forty feet and clocked in around twenty-five tons) and Simolestes. Their skulls could reach up to ten feet long (the early Cretaceous Kronosaurus would have a head twelve feet long!), and their bodies could span up to sixty feet in length. Most would’ve weighed around ten tons. These pliosaurs had large, conical teeth and were the apex predators of the day.

Pliosaurus - a.k.a. Predator X - hunting in a Mesozoic ocean

In the Early Cretaceous, small plesiosaurs with stunted necks radiated; but later on in the Early Cretaceous, the elasmosaurs appeared. These infamous plesiosaurs are famous for being among the longest of their kind, reaching up to fifty feet in length due to their long necks that contained as many as seventy-six vertebrae, more than any other known vertebrate. It’s no surprise that half of Elasmosaurus’ length was in its neck and head alone! The pliosaurs, such as the monstrous Pliosaurus funkei (known as ‘Predator X’), shared the ocean with them. The aforementioned Pliosaurus was fifty feet long and weighed around forty-five tons; most notably, its jaws could produce a bite force of 33,000 psi, perhaps the largest bite of any animal in earth’s history. At the beginning of the Late Cretaceous, the ichthyosaurs became extinct; it’s theorized that a new type of plesiosaur, the Polycotylidae, evolved to fill their vacant niches. These plesiosaurs had short necks and peculiarly elongated heads with narrow snouts (reminiscent of the late great ichthyosaurs). Elasmosaurs continued to abound, but all plesiosaurs – of both morphological types – went extinct after the K-T event.

a pliosaur snags himself a plesiosaur buffet

The diet of the big-headed, short-necked pliosaurs is pretty straightforward: they were apex predators, at the top of their food chains, perfectly designed to ambush and pursue prey of all sizes. Their teeth could pierce any soft-bodied prey, especially fish, and their skull structure and jaws were suited for grabbing and shearing their prey. They had great eyesight, and they could reach greater speeds than their plesiosaur counterparts. The diet – and hunting methods – of the long-necked, small-headed plesiosaurs is a different matter entirely. Though it’s generally accepted that they dined on shellfish, bony fish, and hard-bodied cephalopods – their jaws and teeth could pierce tough shells, and some specimens have been found with cephalopod shells in their stomach areas – there’s a lot of contention about how they used their necks. When a creature evolves such a long neck – whether it’s a modern giraffe or a Jurassic sauropod – the question is, “Why?” What purpose did it serve in the plesiosaur’s life? Some have speculated that they used their necks to intercept fast-moving fish, but computer models show that the neck couldn’t move very fast through water due to skin friction. Others have speculated that plesiosaurs rested on the seafloor and used their head to ‘sweep around’ for prey, or that they would swim to the surface and plunge their necks downwards in search of a meal. These last two theories assume that the neck was flexible, but we now know plesiosaur necks were actually quite rigid with limited vertical movement; and so we return to the age-old question, “What’s the point?” As to this, there’s limited agreement. Some scientists wonder if the long neck enabled the plesiosaur to surprise schools of fish before the sight or pressure-wave of the body could alert them; or perhaps they were bottom feeders, using their stiff necks to plough the seafloor and eat benthos (marine organisms living in the ‘benthic zone’ close to the seafloor); or perhaps they were plankton feeders, filtering plankton like modern whales? One species of plesiosaur, Aristonectes, had hundreds of teeth which it could use to sieve small crustaceans from the water. All this is conjecture; what is known is that plesiosaurs weren’t adapted to catching large, fast-moving prey. An interesting twist is that some plesiosaur remains have been found with gastrolith stones in their stomach; the size of the stones indicate they were swallowed on purpose, and it’s believed that the gastroliths may have helped to break down cephalopods in a muscular gizzard. 

a plesiosaur on the prowl for shellfish

One of the strangest things about the plesiosaurs is that they gave birth to live young. Up until the tail end of the 1900s it was believed that plesiosaurs crawled up onto the beach to lay their young. This was a good assumption: they were reptiles, after all, and laying eggs is kind of a reptile thing. Some paleontologists, however, questioned the assumption: first of all, plesiosaur limbs didn’t retain functional elbow or knee joints, which would be needed for the creature to raise itself to lay eggs; secondly, it’s hard to imagine titanic plesiosaurs being able to survive crawling onto dry land to deposit eggs. Scientists knew that ichthyosaurs (also marine reptiles) bore live young, evidenced by fossilized embryos; it wasn’t until 1987, however, that the fossil of a pregnant Polycotylus was unearthed showing that it gave birth to a single large juvenile. This hinted that plesiosaurs, like modern whales, gave birth to live young and operated by a k-strategy for survival, in which they bore less progeny but made up for it by practicing paternal care. 

a Polycotylus giving birth

The Placodonts

armored Henodus placodonts in a Late Triassic sea. They may look like sea turtles,
but they're of an entirely different stock.

If a walrus and a turtle somehow found a way to mate, their offspring would probably look like a placodont. The first placodont fossils were discovered in 1830 and misidentified as belonging to pycnodont fishes; it wasn’t until Richard Owen came along that it was realized that Placodus actually belonged to a new group of reptiles. Today placodonts are classified as members of Sauropterygia, which also includes nothosaurs and plesiosaurs. Placodonts are unique among their sauropterygian brethren in possessing armor. Though the earliest placodonts were scantily-clad and resembled modern marine iguanas, the later developments looked like overripe turtles with a bony carapace that extended over the body and (in some cases) even partly down the length of the tail.

Placodonts – both armored and unarmored – showed up in the early Triassic. Because of the overall lizard-like body plan (and particularly the feet that still have toes), it’s believed they evolved from Permian lizards. Their immediate ancestors were probably beach-combing lizards that learned to dig in the sand and mud to unearth buried shellfish, and they may have raided tidal pools for shellfish or crustaceans. Ancestral placodonts probably started out with teeth similar to larger land-dwelling reptiles, but over successive generations evolution may have favored those with teeth better suited to a diet of shellfish. Those with forward-facing teeth would’ve had an easier go plucking shellfish out of rocky crevices in tidal pools, and those with robust rounded back teeth could’ve crushed the shells without worrying too much about dental ‘wear and tear.’ Evolutionists speculate that near-constant exposure to water – not to mention moving through it in the search for food – would’ve promoted adaptations like webbing between the toes to foster better marine movement while retaining the ability to move overland in search of various tidal pools.

an unarmored Placodus

Placodonts were relatively small creatures; most ranged between three and six feet long, and the largest clocked in around nine feet in length. In general terms they were short-limbed, robust animals that seem designed for life in shallow, near-shore environments. Their dense bones and (for some) armored plates made them negatively buoyant – like modern sea-cows, they wasted no effort in plodding along the seafloor in search of shellfish. Their small size and lack of a specialized marine body type indicates they were likely semi-aquatic in the sense that they could’ve clumsily lumbered onto the land to rest, breed, and escape marine predators. Placodonts come in two types – armored and unarmored – and the unarmored types had strong, square-shaped bodies; short, largely immobile necks; long, tapering tails; and thick, heavy ribs. Their upper limb bones were slender, and their hands and feet were short and weak. Their pectoral and pelvic girdles were located more underneath the body than to the side, and their vertebral column was weak; this meant they weren’t great at supporting their weight when on land, but they were able to use their limbs for steering and propulsion. It’s likely that their hands and feet were webbed. Armored placodonts tended to have broad, flattened bodies with low neural spines (unlike their unarmored counterparts) and short, paddle-like limbs. 

All placodonts, both armored and unarmored, had robust skulls and rounded, flattened teeth in their jaws. The build of skull and muscle attachments indicate that placodonts pulled their jaw backwards as it closed, perfect for crushing shells against a battery of crushing teeth at the back of their jaws. Most placodonts – with the exception of a few advanced armored types – had protruding teeth at the front of the jaws designed for plucking shelled invertebrates from the thickest parts of the seafloor. Those types without these protruding teeth would’ve been relegated to fishing food from mud or sand. Placodonts fed by pitting mollusks between their enormous teeth, crushing the shell, spitting out the shelly parts, and swallowing the soft parts. Because of this feeding style, placodonts have often been regarded as reptilian analogues of walruses; now, however, we know that walruses don’t crush their mollusk prey, as once believed, but use a tremendous amount of suction to remove the soft parts from the shell. Though placodonts and walruses may have had similar diets, they had radically different means of getting to the ‘meat’ of their prey. Though it’s generally believed that placodonts fed exclusively on bivalves, some scientists have postulated that some species may have fed on crustaceans; others that they could’ve eaten brachiopods (but though brachiopods were abundant in placodont environments, they were nutritionally bankrupt). 

a placodont feeds along a shallow Triassic seafloor

Because placodonts lacked flippers or propulsive tails, they would’ve been slow-moving and prone to predation by marine reptiles (such as ichthyosaurs and nothosaurs) as well as sharks. Large predatory fish called phytosaurs, and even early pterosaurs, may have preyed on placodonts. The earliest placodonts showed up in the early Triassic in tandem with primitive ichthyosaurs that were ravaging the oceans, and semi-aquatic nothosaurs lived along the coasts, competing with the placodonts in their home environment (sharks were growing bigger and meaner, too). Most paleontologists believe placodonts developed extensive armor carapaces as a means of defense against predators (one scientist, though, postulated that the carapaces were hydrodynamic adaptations to promote better aquatic movement; this must be rejected, however, because placodonts lack any other such features; any hydrodynamic benefits were a byproduct, rather than a cause, of the armored evolution). The presence of predators necessitated a type of defense, and just as turtles developed armored shells to protect them on land, so, too, did placodonts evolve carapaces to protect them at sea. A fully-grown armored placodont would’ve been a difficult meal for most predators; the common nothosaur, for example, had needle-like teeth designed for soft-bodied prey like fish. Such teeth would’ve easily broken on placodont armor (later types of nothosaurs, such as Simosaurus, may have been able to break through the armor with its blunt-shaped teeth). Fully-grown placodonts may have been able to live with only occasional threats from predators, but it would’ve been a different story for juveniles – as attested by the remarkable fossil remains of two juvenile Cyamodus placodonts in the stomach area of Lariosaurus, a small nothosaur. This fascinating discovery tells us two important things: first, not only were juveniles small enough to be swallowed, their shells may have been quite soft at this young stage (a feature commonly seen in modern shelled animals); second, the fact that two juveniles were found in the same predator before either of them could be digested indicates they were eaten at about the same time. This indicates that large numbers of Cyamodus were active at the same time, which further suggests that Cyamodus (and, by extension, placodonts in general) had an r-strategy for survival: large numbers of young were raised, but they had to fend for themselves absent parental care (like modern sea turtles). Though we don’t know the breeding and nesting habits of placodonts, one can easily envisage a Triassic beach in which thousand of baby placodonts scurry from their sandy nests and dodge pterosaurs on their lurch for the sea – and those that made it to the waters would then have to fend against carnivorous fish, nothosaurs, ichthyosaurs, sharks, and all hosts of predatory creatures. Juvenile mortality would’ve been high, but those few armored placodonts that made it to adulthood would reach a point where they could live and feed without much threat of an untimely demise in a predator’s stomach. The armored carapace may not have been the only line of defense: some paleontologists speculate that placodonts could’ve burrowed into the seafloor like modern rays to escape predators. The exposed carapace of armored placodonts would still be a tough nut to crack.

the unarmored Placodus with a row of scutes along its back

Placodonts have been divided into two major groups: the Placodontoidea and the Cyamodontoidea. The former, sometimes called ‘the unarmored placodonts,’ were less modified than cyamodontoids and retained a typically long reptilian body and a relatively tall and narrow skull. Though they lacked an extensive covering of armor plates, they did have armored scutes growing atop their neural spines, giving them an appearance similar to the modern marine iguana. Only two placodontoid genera have been recognized: Paraplacodus and Placodus. The first was described in 1931 and has only one species, but the other – Placodus – is one of the best known and most common of all placodonts, and this genera has numerous species attested to throughout the whole of the Triassic. It seems even without an armored carapace, these placodonts were able to hold their own. Placodus had three robust, spatulate, forward-point teeth, and it was large (up to nine feet), bulky, and had a long tail. A row of scutes ran along the tops of its neural spines.

Cyamodus

The Cyamodontoids, or ‘the armored placodonts,’ had reduced or absent front teeth and (most poignantly) developed a turtle-like carapace composed of interlocking scutes (though only one of the three sub-groups, the Cyamodontids, had a plastron, or ‘under-shell’, protecting their bellies). Cyamodontoids are generally divided into three families: the Cyamodontidae, the Placochelyidae, and the Henodontidae. The Cyamodontids are represented by only one genus, Cyamodus, which has six species (and which we met earlier in the belly of the nothosaur). Cyamodus had a short skull with a reduced snout and incredibly wide and enormous temporal fenestrae (openings in the heart-shaped skull). The number of teeth different species to species, but all had two projecting front teeth (unlike the placochelyids). They had a broad, flattened body with a carapace of hexagonal to subcircular osteoderms. The carapace covered much of the neck and virtually the entire span of the forelimbs, and a separate armored plate covered the hips and base of the tail. The tail was short and covered in osteoderms (as were parts of the limbs). In 1993 a pair of scientists speculated that, because of its more strongly developed teeth, stronger limbs, and deeper body, Cyamodus was less bottom-dependant and more mobile than the placochelyids, perhaps even living in rougher waters or a more rocky environment.

Psephoderma 

The Placochelyids have two genera: Placochelys and Psephoderma. These two types were united by notably triangular skulls, pointed rostra, and extensive carapaces. Both only had two pairs of front teeth (but they differed in number and placement of back teeth) and both lacked a plastron (a continuous armor shield on the underside of the body, as seen in modern turtles). Likely unable to pull prey from rocky substrates, and because they had flattened bodies and long, slim tails, they have been viewed as reptilian ray mimics that may have hidden in the seafloor to escape predators. Placochelys only has one species, and it has a wider, stronger skull than Psephoderma. It was well-suited for crushing hard-shelled prey, but it seems poorly designed for pulling prey from rocks. Some scientists have speculated that placochelyids may have had a horny beak, but this is pure speculation. Psephoderma had a slim and elongate rostrum and only reached around four feet. It had a notably flattened body covered by a carapace of interlocking hexagonal osteoderms and a caudal plate covering the pelvis and base of its long, slim tail.

The Henodontidae consists of only one genus, Henodus from the Upper Triassic. It was discovered in southern Germany in what was thought to be a semi-enclosed brackish or possibly freshwater lagoon. Henodus is the only placodont known to have inhabited a non-marine environment. Though it was assumed for decades that Henodus had completely lost its front teeth, a Henodus species with front teeth was discovered in the 1990s. Like the Placochelyids, Henodus lacked a plastron. It’s been theorized that the extreme variation seen in Henodus is due to isolation: Henodus became isolated in this ancient German lagoonal basin; free of predators and with a limited diversity of prey, it became super-specialized for foraging in the soft sediment of the lagoon floor. 

a Henodus relaxes on the shoreline after a hard day of eating mollusks

The Nothosaurs

Nothosaurs seem adapted for a life like that of modern seals: catching food in water but coming ashore on rocks and beaches to sleep, mate, and hang out. Nothosaurs averaged around ten feet in length, and they had long bodies with long tails and long necks capped with elongated, flattened heads that were small in relation to their bodies. Paddle-like webbed feet helped them propel through the water, and they had tapered jaws filled with sharp, outward-pointing teeth that indicate a diet of fish and squid. 

an artist's rendition of Nothosaurus

Nothosaurus was the heavyweight of its namesake clade, the Nothosaurs; most species reached up to thirteen feet long, but some reached up to sixteen to twenty-three feet in length. Nothosaurus had long, webbed toes and may have even sported a fin on its tail – the webbed feet, slender body, and long tail (with or without a fin) helped steer it gracefully through the water. Nothosaur trackways found in China in 2014 have been interpreted as paddle impressions left as the animals dug into soft Triassic seabed with rowing motion of paddles, churning up hidden creatures doomed for the nothosaur’s stomach.

Nothosaurs consist of two suborders: Pachypleurosauria (small, primitive nothosaurs) and Nothosauria (which includes Nothosauridae and Simosauridae). Though the nothosaurs were adapted to a semi-aquatic lifestyle, their forebears the pachypleurosaurs don’t seem to share this trait; though in outward appearance they looked dead-on like nothosaurs, they were, in the first instance, much smaller (ranging from as little as seven inches to three feet in length), and, in the second instance, their pitiful limb girdles would’ve made moving around on land quite the exhausting experience. The semi-aquatic lifestyle seems to have evolved with the rise of the nothosaurs in the mid-Triassic. Though it’s generally accepted that nothosaurs proper evolved from the pachypleurosaurs, this isn’t wholly certain; some cladistics put these two groups as sister clades (making them more like ‘cousins’ than ‘mother-daughter’). Nothosaurs differed from their sister-clade Simosauridae in that Simosaurus had a different dental get-up: whereas Nothosaurs had sharp teeth geared towards eating fish and squid, Simosaurus had blunt teeth adapted for eating hard-shelled organisms like ammonites and clams. Most paleontologists believe that an off-branch of the nothosaurs evolved into the wholly marine plesiosaurs, which replaced them at the end of the Triassic Period; other scientists speculate that another branch of the Nothosaurs evolved into the pliosaurs of the Jurassic and Cretaceous periods. 

a pod of Nothosaurs on the prowl (or at play?)

The Triassic Period: A Snapshot

The Triassic Period

250 mya - 200 mya

In 1834 Freidrich von Alberti named the Triassic Period after a particular series of distinct rock layers found throughout Germany and northwest Europe. The series consisted of red beds capped by marine limestone followed by a series of mud and sandstone called the Trias. The Triassic Period marks the beginning of the Mesozoic Era (which lasted from 250 to 65 mya), an era that saw the disintegration of Pangaea (the supercontinent formed during the Permian) and the evolution of life favoring the Reptiles over the Mammals (this is why the Mesozoic is often called ‘The Age of Reptiles’). The biggest change wrought in the Mesozoic was the rise of the dinosaurs, who were perhaps the most successful kind of animal in all of evolutionary history. Dinosaurs came from small, humble beginnings, appearing in the mid- to late-Triassic; at their genesis they played second fiddle to other creatures, and they wouldn’t begin their rise to dominance until the early Jurassic.

At the dawn of the Triassic, the supercontinent Pangaea covered nearly a quarter of the planet's surface. Pangae-like supercontinents have formed numerous times in earth’s history, and geologists speculate that the formation of these continents cycles on a timescale of about every five hundred million years. The early Triassic supercontinent was shaped like a distorted Pac-Man, and this Pac-Man's gaping mouth was the Tethys Sea, a massive bay of the vast global Panthalassa Ocean, which stretched pole-to-pole and was twice the width of the modern-day Pacific Ocean. Islands, seamounts, and volcanic archipelagos were scattered throughout Panthalassa along the Triassic equator. Pangaea would begin splitting apart in the late Triassic, and by the mid- to late-Jurassic, the Tethys bay would become a waterway cutting straight through the heart of Pangaea (the southern piece of Pangaea would be known as Gondwana, the northern as Laurasia). The changing of Pangaea came about due to plate tectonics. The earth's crust is divided into broad, rigid plates that are constantly (albeit slowly) on the move. These plates move atop firmer layers of mantle, and when the plates interact the result is earthquakes, mountain ranges, and volcanoes. As the Tethys Sea began to weasel its way through the heart of Pangaea, the result would've been a constant litany of volcanic eruptions along the shifting plates. It's speculated that this geological activity of the late Triassic is responsible for the Triassic-Jurassic Extinction Event.

Speaking of extinctions, just as the end of the Triassic would be marked by an extinction, so, too, was its beginning. The Triassic began in the wake of the Permian-Triassic Extinction. This ‘Great Dying’ was the ‘mother of mass extinctions’: 90-95% of the world's marine life and 70% of terrestrial vertebrates perished. Insects, the hardiest of the planet's creatures, suffered, too. This was the worst extinction in world history, so much so that one Permian creature –Lystrosaurus – has been called the Permian/Triassic ‘Noah’ simply because it made it through to the other side (it originated in the late Permian and is seen in early Triassic rock). The creatures that survived the extinction struggled to eek out an existence in an eerie post-apocalyptic world: the climate was unusually dry with vast areas of desert, and the temperatures flashed between extremely hot and very cold. The sea levels were low and anoxic (lacking in oxygen); water may have lacked oxygen just ten to twenty meters below the water's surface. Because the deep oceans were anoxic, the shallow waters were unaerated. The air, consequentially, was anoxic as well. Carbon dioxide in the atmosphere vaulted to record levels due to extreme volcanic activity. This volcanism resulted in early Triassic forests – vestiges of the late Permian -  devastated by forest fires spawned by lava flows; even far beyond the volcanoes, acid rains mixed with ash fell in black droplets, suffocating even the hardiest plant life and making life a rather gray and bleak affair for the surviving animals. As if this weren't inhospitable enough, radiation levels were unusually high (probably caused by ill-timed cosmic forces). 

It would take more than one million years before normal ecosystems, coral reefs, and large animals recovered from the extinction's fall-out. Things became pleasant (or at least readily survivable) by then: oxygen returned to about 80% of its modern level, carbon dioxide was at a comfortable setting around six times what we're used to, and the temperatures stabilized for an average warmth of about one hundred degrees Fahrenheit. Nevertheless, the Triassic remained a harsh world underscored by deserts. Temperatures were hot during the summer and cold in the winter with cyclic megamonsoons caused by Panthalassa's ocean currents. Deserts of dry, red rock devoid of vegetation stretched throughout Pangaea's interior, sand dunes scoured the beaches, and vast mountain ranges that had risen with Pangaea's creation in the Permian (such as the Appalachians in the eastern United States) began to look wilted and weathered-down. The Triassic world lacked ice caps, and its polar regions were moist and temperate (a suitable climate for plants and animals). Spiders, centipedes, millipedes, and scorpions survived from the Permian, and newer groups of beetles flourished (grasshoppers made their debut appearance in the Triassic); the Triassic also witnessed the genesis of primitive frogs, turtles, and mammals. Animal diversity was limited, since species had to cross an entire continent of deserts to find an environment favorable towards adaptation; because of the supercontinent’s vast interior deserts, most Triassic animals probably stuck to the supercontinent’s shorelines.

inland Pangaea of the Triassic was mostly desert

The arid badlands of the Pangaean interior stood in stark contrast to its perimeters: near the water, richly-vegetated pockets of plant life emerged. Conifers, gingkoes, ferns, and cycads flourished. Horsetails took root in the wettest regions. Monkey-puzzle trees, tree ferns, and modern-day club mosses painted the forests green. These forests, however, lacked flowering plants or grasses (they hadn't developed yet). Moisture from the ocean, particularly from the growing Tethys Sea, resulted in massive low-pressure cells that produced titanic monsoon rains in the coastal regions; cross-equatorial ‘megamonsoons’ were further aggravated by the strong contrast between Pangaea and the global ocean. The end of the Triassic saw climates becoming seasonal with alternating warm-cool and wet-dry cycles, and Pangaea had been steadily marching southward, producing drier and warmer climates. The stabilization of the climate did much for the Panthalassa Ocean, and a variety of new reptiles evolved, some of which would become legendary for the Mesozoic Era.

although the Pangaean interior was mostly desert, the coastal regions were humid
and were host to an array of vibrant lifeforms

~  Triassic Marine Life  ~

Shellfish, thick-scaled fish, and marine reptiles have become iconic for the Triassic ocean. Ammonites survived the Permian-Triassic extinction and thrived in the Triassic. Because fossil fish from this period are uniform, it indicates that few families survived the extinction. Stony corals emerged for the first time, and reefs sprouted along Pangaea's coasts and throughout the Tethys Sea. A variety of marine reptiles would call these coral reefs home, and perhaps the most famous of them all are the nothosaurs. 

an artist's rendition of a Lothosaurus

Nothosaurs averaged about ten feet in length and had a long body with a long tail. Their webbed, paddle-like feet powered them through the water. Their necks were long, the head elongated and flattened and small in relation to its body. Nothosaurs had jaws filled with sharp, outward-pointing teeth. It's speculated that nothosaurs lived a lot like modern-day seals, catching their food (likely fish and squid) in the water but spending their resting time on the beaches. Newly-discovered impressions in China indicate that nothosaurs may have dug into the seabed by paddling in rowing motions, churning up food burrowed in the seabed. 

an artist's rendition of Triassic placodonts

Another type of marine reptile, the placodonts, looked like barrel-bodied lizards with a superficial resemblance to modern-day marine iguanas. Triassic placodonts were relatively small, but as carnivorous marine reptiles such as nothosaurs and plesiosaurs began to develop, placodonts responded by developing bony plates on their backs to protect themselves while foraging for food. By the late Triassic, some placodonts looked less like modern-day iguanas and more like modern-day sea turtles. Weighted down with so much armor, placodonts probably lived in shallow waters rather than in the deep ocean. Their diet likely consisted of bivalves, brachiopods, and other marine invertebrates.

A contemporary of the nothosaurs and placodonts were the newly-arrived plesiosaurs. Appearing in the late Triassic and becoming dominant in the Jurassic Period, the plesiosaurs thrived until their decimation at the Cretaceous-Paleogene Extinction. Plesiosaurs have become the fiercest Mesozoic ‘monsters of the deep,’ but in their earliest days in the late Triassic, they were but weak shadows of what they would become. Plesiosaurs had broad, flat bodies and short tails. Their limbs had evolved into long flippers. These flippers made a flying motion through the water. All plesiosaurs breathed air, bore live young, and may have been warm-blooded. Some plesiosaurs had extremely long necks and small heads; these plesiosaur behemoths became the titans of the plesiosaur family. They would've been slow and fed on small sea animals, and many would fall prey to the Black Sheep of the plesiosaur families, those with short necks and massive heads that became the apex hunters of the Mesozoic Oceans. 

plesiosaurs along the shoreline with a prowling rauisuchian

Plesiosaurs shared the ocean with another type of marine reptile, the ichthyosaurs: literally meaning ‘fish lizards,’ these animals varied from three to nearly fifty feet in length and resembled modern whales and dolphins. Their limbs had evolved into flippers (some replete with digits and fingers) and some species had a dorsal fin. Their heads were pointed and the jaws lined with teeth. Conical-shaped teeth were designed to catch smaller prey; bladed teeth were designed to go after the bigger animals. Their eyes were humongous (useful for diving deep), and their necks were short (some later species had almost no neck at all). Ichthyosaurs (like plesiosaurs) were air-breathing, bore live young, and were probably warm-blooded. Ichthyosaurs showed up in the Triassic and excelled; but the arrival of the plesiosaurs added a new blood of competition in the ocean, and ichthyosaurs began to dwindle, being replaced by the plesiosaurs in the late Jurassic and Cretaceous Periods. And through all of this, sharks kept doing their thing.

ichthyosaurs frolicking in the Tethys Sea

~  Triassic Life in the Skies  ~

nesting Preondactylus

As terrestrial reptiles turned to the sea, so terrestrial reptiles turned to the air. These ‘winged reptiles’ are the earliest vertebrates known to have acquired the power of flight, predating the avian dinosaurs by millions of years. The pterosaurs dominated the empty skies in the Triassic and clung to them throughout the Mesozoic; the avian dinosaurs, though late starters, survived the Cretaceous-Paleogene Extinction whereas the pterosaurs did not. Pterosaur wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a lengthened fourth finger. The earliest species had long, fully toothed jaws and long tails; later forms had a reduced tail and some lacked teeth. Though many paintings and artwork of pterosaurs portray them as leathery-winged lizards, we know many of them had furry coats made up of hair-like filaments called pyncofibers; many of them, like the early Preondactylus, were covered in this hair-like material.

the odd-looking Longisquama

Flying reptiles dominated Triassic skies, squeezing out their Permian forebears, the avicephalians. It’s important to note than the avicephalians weren’t capable of powered flight; they were more or less gliders. They were sparse through the Permian and barely made it into the Triassic before being outdone by the pterosaurs. They had light bones, bird-like skulls, and some had toothless beaks. They had prehensile tails like modern chameleons or monkeys. Longisquama had elongated scales; as to their function, scientists don’t know. Some speculate they acted as ‘pseudo-feathers’ forming ‘wings’. That the avicephalians never attained large populations is attested by the fact that under a dozen species are known from both the Permian and Triassic.

~  The (Stunted) Rise of Mammals  ~

a rather risque size comparison of a tantalizing model and
Lisowicia, a Late Triassic herbivorous dicynodont

As reptiles dominated the ocean and the skies, so, too, they dominated on land. We would be remiss, however, not to give credit where credit is due: the shape of our world depends upon the survival of a shrew-like creature in a dry and dangerous world of tyrants big and small. The therapsids of the Permian nearly went extinct, but their early Triassic hold-outs continued on their dark journey towards mammalian-hood. The earliest true mammals evolved in the Triassic, and they were unimpressive: most were less than a few inches in length. They were mainly herbivores or insectivores, and they may have been partially arboreal and nocturnal. Most laid eggs despite having fur and suckling their young. They had three ear bones like modern mammals, but their jaws had a mixture of mammalian and reptilian characteristics.

an artist's rendition of a feisty cynodont

Life wasn’t easy for the early mammals (called ‘protomammals’), and the stakes were high: the Triassic witnessed a life-and-death struggle for dominance between them and the reptiles. Had the protomammals – led by the dicynodonts and cynodonts – won out, they and their descendants would’ve likely characterized the Mesozoic; as it were, however, the reptiles won fair and square, and they came to dominate the Mesozoic Era. Though it seemed for a moment that the herbivorous protomammals would seize the laurels, the herbivorous reptiles squeezed them off-stage as they developed advanced limb muscles able to sustain a heavier size and diet. Predatory cynodonts dominated their niche in the early Triassic: with sleek profiles, elongated bodies, and slender limbs – all of which promoted rapid movement – the cynodonts were a force to be reckoned with (and their mammal-like faces and wolf-like teeth made them fierce indeed). These carnivorous cynodonts, however, were outdone by the expanding reptilian archosaurs, and by the mid-Triassic cynodonts had contracted to small and medium-sized predators and herbivores. They simply couldn’t compete with the evolving archosaurs, some of whom reached proportions similar to modern-day wolves, lions, and polar bears. The mammals would need to wait for a miraculous (or apocalyptic) intervention to retake center stage.

~  The Age of Reptiles  ~

a spattering of Triassic animals

The Mesozoic has been called ‘The Age of Reptiles’ since reptiles dominated the three major ecosystems: water, earth, and air. Our tiny mammalian ancestors scavenged for a living in a land caught by two opposing types of land reptiles: the rhynchosaurs and archosaurs. The rhynchosaurs were stocky-bodied, herbivorous reptiles sporting powerful beaks. They were abundant throughout most of the Triassic but were supplanted by the archosaurs during the mid-late Triassic. Over the course of the Triassic, certain archosaurs became erect. They were adapted to the dry, arid atmosphere of the early Triassic, evolving elevated metabolisms and avian breathing systems so that they could be continuously active in the humid, oxygen-depleted world in which they lived. The archosaurs laid the groundwork for modern crocodiles, but they're known best for the most successful archosaur of them all: the dinosaur.

The dinosaurs – or ‘terrible lizards’ – acquired an erect gait, so that the legs could be postured directly beneath the animal (like in modern elephants). This made dinosaurs efficient: it took less energy to keep its body off the ground and it avoided Carrier's Constant, since they could run and breathe at the same time. Other distinguishing characteristics have to do with muscle locations and orientations on various bones, the shape of the joints connecting the bones to the pelvis, the particularity of their ankle joints, and some details relating to the skull. The earliest dinosaurs included Coelophysis and Plateosaurus.

The dinosaurs appeared in the mid to late Triassic, and they lived in vibrant ecosystems filled with creatures much bigger (and scarier) than them. Because dinosaurs weigh heavier in popular thought than their Triassic counterparts, an image of a Late Triassic teeming with dinosaurs has become commonplace – but it is an image rooted in fantasy rather than reality. Studies of Triassic fossil beds and trackways show that while dinosaurs emerged during the mid-late Triassic, they were never dominant. They were always relegated to the sidelines. Dinosaurs first appear in southern Pangaea and began to diversify around 230-220 mya, but they remained clustered in the humid belts of Pangaea. In the arid belts closer to the equators, dinosaurs were rare if present at all (it seems that they couldn’t handle the heat). Triassic amphibians and reptiles flourished in the interior, and in the exterior they remained dominant.

early dinosaurs defend their kill against a rauisuchian

Paleontologist Steve Brusatte, who has done a lot of work in Triassic studies, notes in his The Rise and Fall of Dinosaurs that dinosaurs ‘didn’t just sweep across Pangaea the moment they originated, like some infectious virus. They were geographically localized, held in place not by physical barricades but by climates they couldn’t endure. For many millions of years, it looked as if they might remain provincial rubes, stuck in one zone in the south of the supercontinent, unable to break free – an aging high school football hero of faded dreams, who could have been something if only he’d been able to get out of his tiny hometown.” (Brusatte, pp. 59-60) This was the status quo for most of the Triassic, but in the last few million years, things began to change. Change didn’t happen at once but in two stages. First, in the humid regions, the dominant large plant-eaters (the rhynchosaurs and dicynodonts) began to dwindle, even disappearing in places; scientists don’t know why, but regardless of the reasons, the herbivorous dinosaurs – particularly the prosauropods – were able to fill the niches left vacant. In the humid areas of Pangaea, dinosaurs rose to comprise thirty percent of the ecosystem whereas the previous heavyweights dropped down to twenty percent. At the very end of the Triassic, at around 215 mya, dinosaurs began migrating into the drier regions; though scientists aren’t sure why, the best guess is that climate change – caused by the slow rifting of Pangaea (to be addressed shortly) – blurred the stark boundaries between the arid interior and humid exterior. The arid regions, where only the bravest (or most foolish) dinosaurs dared to tread, became manageable.

For most of the Triassic, dinosaurs were on the ecosystem’s fringes. Dinosaur diversity was stunted compared to that of their comrades. Morphological diversity – how much a type of creature shows differences between species – has been used as a barometer of an animal’s ‘fitness.’ The idea is that ‘better’ types of creatures will be able to better adapt and evolve, whereas less ‘worthy’ creatures will not. The result is that some types of animals have a lot of morphological diversity while others don’t. A 2008 study of Triassic animals found that dinosaurs had little diversity compared to their counterparts. Paleontologist Steve Brusatte (who did the project) reports that ‘All throughout the Triassic, the pseudosuchians were significantly more morphologically diverse than dinosaurs. They filled a larger spread of the map, meaning they had a greater range of anatomical features, which indicated that they were experimenting with more diets, more behaviors, more ways of making a living. Both groups were becoming more diverse as the Triassic unfolded, but the pseudosuchians were always outpacing the dinosaurs. Far from being superior warriors slaying their competitors, dinosaurs were being overshadowed by their crocodile-line rivals during the 30 million years they coexisted during the Triassic.” (pp. 80-81)

an early dinosaur and a Postosuchus face off

Dinosaurs, then, were surrounded by other creatures – such as the phytosaurs, who resembled gigantic crocodiles but aren’t to be confused with the modern crocodile's ancestors (though they lived in the Triassic, they were smaller, moving with the speed and agility of a greyhound and resembling reptilian wolves). The aetosaurs were large, armored herbivorous reptiles preyed upon by the ornithosuchians, which resembled titanic crocodiles with double rows of armored plates running along their backs. The biggest and baddest Triassic carnivores were the rauisuchians, the fear and dread of the earliest dinosaurs. Like dinosaurs, rauisuchians had an erect gait with their legs oriented beneath them in a pillar-erect posture. The rauisuchians lived through most of the Triassic but died out in the Triassic-Jurassic Extinction. Their absence would give the earliest theropod dinosaurs room to grow into even larger carnivores than the rauisuchians could muster.

Rauisuchian dominance came to an end with the Triassic-Jurassic Extinction Event. The Tethys Sea was beginning to cut through Pangaea due to the shifting of tectonic plates, and the supercontinent would soon split in half between Laurasia to the north and Gondwana to the south. This great wrenching wouldn't be accomplished until the Jurassic, but the Triassic suffered the birth pangs: volcanic eruptions unlike anything the world has seen before or since (except for when the planet was boiling in its own stew) scarred the atmosphere. Oxygen depleted and carbon dioxide increased exponentially. Though nowhere near as destructive as the extinction that preceded it, the Triassic-Jurassic extinction hit the ocean especially hard: all marine reptiles except ichthyosaurs, nothosaurs, and plesiosaurs died out. Even invertebrates such as brachiopods, gastropods, and mollusks suffered. Twenty-two percent of marine families and half of marine genera went extinct. On land, the dinosaurs' predatory rivals went extinct along with some of the earlier dinosaurs. But the hardier and more adaptive dinosaurs survived into the Jurassic where they would flourish.

~  The Archosaurs: A Closer Look  ~

The archosaurs’ living relatives include birds and crocodiles (the latter of which appeared in the early Triassic, almost identical to modern crocodilians). Archosaurs are ‘diapsid amniotes’: they are ‘diapsid’ because they have ‘two arches’ (or holes, called temporal fenestrae) in each side of their skulls, in front of the eyes and the jaw; and they are ‘amniotes’ because they lay eggs on land (as opposed to fishes and amphibians, which lay eggs in water) or retain the fertilized egg in the mother (as is the case with mammals). Archosaurs first evolved around 300 mya during the late Carboniferous, and they diversified like wildfire: all crocodiles, lizards, snakes, turtles, birds, non-avian dinosaurs, and pterosaurs are classified as archosaurs. Some diapsids have lost one hole in the skull (such as lizards), and snakes lost both holes; they remain archosaurs, however, because of their ancestry.

Distinguishing characteristics of archosaurs, aside from being amniotes, include (as aforementioned) two fenestrae on each side of the head, teeth set in sockets, and a prominent ridge on the femur called the fourth trochanter. Some later archosaurs (such as snakes and lizards) don’t have all these characteristics, but their descent from archosaurs keeps them ‘in the family.’ The double fenestrae on each side of the skull lightened the skull’s weight, enabling archosaurs to develop larger skulls with larger jaws. The fourth trochanter provided a site for the attachment of muscles on the femur; these stronger muscles allowed for the development of an erect gait, seen most vividly in the dinosaurs.
Archosaurs made leaps and bounds in the Permian and diversified like mad in the Triassic. They became erect, giving them a distinct edge against their rivals, the mammal-like reptilian synapsids; their dominance, however, began before they got their legs truly beneath them. They adapted to the desert landscape and arid atmosphere of the Triassic, developing elevated metabolisms and avian breathing systems so that they could be active in the hot, oxygen-deprived world in which they lived. Many scientists believe several archosaurs may have had four-chambered hearts like modern birds and crocodiles, enabling them to be more active due to better oxygenation. The archosaur clade has generally been divided into two further clades: pseudosuchia (which includes modern crocodilians and their extinct relatives) and avemetatarsalia (which includes modern birds and their extinct relatives). Archosaurs still walk – and fly! – among us today. Most archosaurs were and continue to be predators; however, some archosaurs, such as the aetosaurs, were herbivores, as were some crocodilians such as Simosuchus.

The pseudosuchians – the first off-branching clade of the archosaurs – includes all reptiles closer to crocodiles than to birds. A distinguishing characteristic is that their feet bones resemble those of a crocodile (as opposed to the feet of the avemetatarsalians, which resemble those of birds). The pseudosuchians have been further divided into more particular clades: the phytosaurs, the aetosaurs, the ornithosuchians, the erythrosuchids, the rauisuchians, and the crocodylomorphs.

a phytosaur sunbathing beside a stream

Phytosaurs were large, semi-aquatic archosaurs that lived in the Late Triassic. They were long-snotted and heavily armored, resembling modern crocodiles in size, appearance, and lifestyle. Though they were deadly carnivores, their name implies that they were plant-eaters; this is because the first fossils were thought to belong to an herbivore. Paleontologists believe phytosaurs came around before the archosaurs split between crocodile- and bird-like forms.

an artist's rendition of an aetosaur

The aetosaurs were medium- to large-sized archosaurs, heavily armored and herbivorous. They had small heads, upturned snouts, erect limbs, and bodies covered by plate-like scutes. Unlike the phytosaurs who enjoyed a good swim, aetosaurs were wholly terrestrial. It’s speculated that many species burrowed for their food, and there’s evidence that some (if not all) aetosaurs made nests.

Another type of pseudosuchian, ornithosuchians, were able to walk on their hind legs like many dinosaurs; these ‘bird-crocodiles’ would’ve spent most of their time on all fours, reserving bipedal locomotion for quick bursts of speed. Ornithosuchians, such as the name-sake Ornithosuchus, had a double row of armored plates that ran along their backs.

an Ornithosuchus in bipedal stance

The erythrosuchids lived from the early to the middle Triassic Period. These archosaurs were unusually large with outsized, deep heads that had a ‘step’ in the jaw due to the tip of the lower jaw rising above the tip of the upper jaw. These were the first archosaurs to develop a triradiate pelvic girdle consisting of three bones: the ischium, ilium, and pubis. These were the biggest, strongest, and most dangerous predators of the early Triassic. They’ve been dubbed the ‘Crimson Crocodiles’ since being discovered in the red rock of Triassic bone-beds. Some reached up to half a ton in weight and were armed with three-feet-long, dinosaur-like heads filled with saw-edged teeth.

a pair of erythrosuchids sparring over a kill

The rauisuchians were large Triassic archosaurs with an erect gait later seen in dinosaurs (but it was a matter of convergent evolution; the rauisuchians did not evolve from, or to, dinosaurs). Though a dinosaur’s hip socket faces outward and its femur connects to the side of the hip, a rauisuchians’ hip socket faces downward to form a shelf of bone under which the femur connects. This posture has been called a ‘pillar-erect’ posture. Rauisuchians lived through most of the Triassic but were eliminated in the Triassic-Jurassic extinction event; their demise gave theropod dinosaurs the space needed to become the dominant terrestrial predators of the Mesozoic.

a quartet of rauisuchians

Last on our list of pseudosuchians are the crocodylomorpha. These were the ancestors of modern-day crocodiles, but they looked remarkably different from what we’re used to. These were small, lightly-built, active terrestrial animals. The earliest members of this group saw action in the Triassic and lasted until the Late Jurassic. The earliest ‘crocodiles’, such as Hesperosuchus, were built like greyhounds and resembled reptilian wolves, but as the Mesozoic plodded on, the crocodiles diversified to become larger and open to new ideas: some later crocodylomorphs became semi-aquatic, like crocodiles today. The largest of these crocodylomorphs, Sarcosuchus, lived in the late Cretaceous; it was during the late Cretaceous that the earliest ‘modern’ crocodiles evolved.

a Sarcosuchus has a theropod dinosaur for a snack

The pseudosuchians continue today with the crocodiles; the other branch of archosaurs, avemetatarsalia, continues today with birds. This group includes all archosaurs more closely related to birds than crocodiles. The name of this group means ‘bird metatarsals,’ hinting at the distinguishing characteristic of these archosaurian feet, but the group also goes by other names, such as Pan-Aves, Ornithisuchia, and Ornithodira. Members of avemetatarsalia include pterosaurs, dinosauromorphs, dinosauria, and birds.

Pterosaurs, as mentioned above, were the flying reptiles of the Mesozoic. Their remains have been found from the late Triassic to the end of the Cretaceous, and they’re the earliest vertebrates known to have evolved powered flight (the avian dinosaurs, which would pave the way to birds, didn’t come until later on in the Mesozoic).  Pterosaurs didn’t have feathers; their wings were formed by a membrane of skin and muscle stretching from the ankles to a dramatically lengthened fourth finger. Early pterosaurs had long, fully toothed jaws and long tails; later forms had a reduced tail and some even lacked teeth. Many had furry coats of hair-like filaments known as pyncofibers that covered their bodies and parts of their wings.

a group of Coelophysis at a watering hole

Dinosauromorpha includes dinosaurs and other closely related animals. They appeared in the Middle Triassic around 240 mya; true dinosaurs, belonging to the clade dinosauria, made their debut around 230 mya. Though dinosaurs diversified in the later Triassic, they weren’t the dominant creatures; though many later Triassic dinosaurs reached large proportions, the top-tier Triassic predators were pseudosuchians. This changed after the Triassic-Jurassic extinction event; from this point on, through the Jurassic and Cretaceous Periods, the dinosaurs diversified and dominated the landscape. Their dominance ended with the Cretaceous-Paleogene extinction event 65 mya, which wiped out up to 75% of earth’s plant and animal life. The last major clade of avemetatarsalia are the birds, which evolved from theropod dinosaurs. Due to their small size, ability to keep warm with feathery insulation, and lacking bigger predators, most were able to not only survive the Cretaceous-Paleogene extinction event but also to thrive in the Cenozoic. Thousands of bird species continue today, a testament to the ingenuity and ongoing success of the dinosaurs. One could even say, with a hint of truth, that dinosaurs still rule the world.

~  Triassic Plant Life  ~

Triassic Colorado, ca 225 million years ago

The northern half of Pangaea was dominated by ginkgo and tree-fern forests, and the forest floor was carpeted by ferns. Heading south towards the equator, where it was drier and the deserts began, these lush northern forests disintegrated into patchier and thinner forests built mostly of conifers and cycads. Rivers and coastlines sported highly fertile areas, much as the modern Euphrates waters the deserts of the Middle East. Near these waterways, dense vegetation grew up with ferns and horsetails sprouting along the ground and interspersed with groves of cycads, reed-ferns, ginkgos, and conifers. This general sketch is derived from fossilized plant life from the Triassic, but it’s unfortunate that floral fossils are rare. Nevertheless, paleontologists have been able to give us a glimpse into Triassic plant life.

Triassic plant life generally fell into two categories: spore-bearing plants and seed-bearing ones. Spore-bearing pteridophytes rely on the wind for spreading their spores; when windblown spores land in moist settings, they’re able to germinate; when sperm is reproduced, the sperm ‘swims’ in search of eggs formed in nearby germinated plants. Because this method of reproduction is inefficient (not to mention laborious!), most spore-bearing plants sprout new branches from a single underground stem so that one reproductive event can generate an entire field of plants. Spore-bearing plants are dependent upon moist conditions for reproduction; thus spore-bearing plants couldn’t meander far from bodies of water – quite a disadvantage in the arid ecosystems of the Triassic. Seed-bearing plants (called gymnosperms) freed plants from the restrictions imposed by spore reproduction. Gymnosperms were able to radiate away from water sources and colonize drier terrain; and because the spore-bearing plants couldn’t compete, gymnosperms were able to multiply as if on steroids.

The four major groups of gymnosperms alive today are cycads, ginkgos, conifers, and angiosperms; of these four, only one – the ‘flowering plants’, or angiosperms – were absent in the Triassic. Cycads were evergreen plants with short, stout trunks and long, pinnate leaves that look like those of modern palms; ginkgo trees have characteristic, fan-shaped leaves, and only one species remains alive today; and conifers are woody plants with seeds born in cones and leaves that usually take the form of needles (modern conifers include redwoods, pines, junipers, firs, cypresses, and cedars). We will examine some spore-bearing plants of the Triassic (such as ferns and horsetails) before looking at the gymnosperm newcomers. However, we would be remiss if we failed to mention the lycopods, one of the most primitive types of plants with descendants still around today.

an artist's rendition of Lepidodendron in various
cycles of its life; from Carboniferous Period

The spore-bearing lycopods are the oldest living vascular plant division, having appeared on the scene 410 mya in the Silurian Period. They flourished in the Carboniferous Period, reaching proportions hard to imagine today. It’s difficult to picture modern lycopods – such as club mosses – reaching to the heavens, but Lepidodendron grew up to one hundred feet tall and could have a trunk three feet in diameter. Unlike modern trees, leaves grew out of the entire surface of the trunk and branches, falling off as the plant grew, eventually leaving only a small cluster of leaves at the top.  These lycopod trees comprised vast forests during the Carboniferous, but they began to get squeezed out as more advanced plants (such as ferns, horsetails, and conifers) developed in the Permian. Lycopods were able to regain a foothold in the wake of the Permian-Triassic extinction event, spreading like kudzu in the early Triassic. Their resurgence, however, was brief, and the Mesozoic landscape was soon dominated by the rising gymnosperms.

Ferns, such as we have today, existed in the Triassic, and they reproduce by spores rather than seeds. Ferns have stems and leaves, and most have fiddleheads, furled fronds that unroll into a new frond. Ferns appeared in the late Devonian Period, but their diversification skyrocketed in the early Cretaceous, and in the latter part of that same period, the ‘Great Fern Radiation’ resulted in the emergences of many modern fern families. Another spore-bearing plant of the Triassic was the horsetail, also known as snake grass or scouring-rush. Modern horsetails are considered ‘living fossils’ because they’ve undergone few changes since their genesis in the Devonian or Carboniferous Period. Triassic horsetails grew along the waterways, and scientists speculate they could have reached up to one hundred feet in height. Though horsetails would’ve been a decent source of nutrients for Triassic herbivores, they have an adaptation that dissuades consumption: special cells ‘drink up’ silica from the soil, and the silica ‘armors’ the horsetail stem with row upon row of glass-hard micro-lumps. An herbivore would quickly learn that horsetails erode their teeth down to the gum-line, but the less intelligent (or more laissez-faire) may not have cared. Horsetails have a backup protection system: because they grow from roots buried underground, the stem could be eaten to the ground and the horsetail would continue re-growing from underground.

Glossopteris grow above a bed of ferns in the early Triassic

Now we turn to the seed-bearing gymnosperms of the Triassic, paying special attention to seed ferns (not to be confused with their spore-bearing counterparts), cycads, ginkgos, conifers, and the infamous monkey puzzle trees. Seed ferns evolved in the late Devonian and flourished during the Carboniferous and Permian. They declined during the Mesozoic and had all but disappeared by the end of the Cretaceous (a few species carried on into the early Cenozoic). Seed ferns carried their seeds in their fronds with distinctive glandular hairs. Some seed ferns are called ‘tree ferns’ because they had a trunk elevating the fronds above ground level. There were at least three major species of seed ferns that have been readily fossilized from the Triassic. The first, Glossopteris, had tongue-shaped leaves and grew to about twelve feet tall, tapering upwards like a Christmas tree. Its limbs were probably widely-spaced to take advantage of the low-angle sunlight at high latitudes. They had large, broad leaves fell to the ground at the end of summer; Glossopteris leaves are often found in dense accumulations from autumnal leaf banks. This deciduous tree went extinct with the Triassic-Jurassic extinction event (but some paleobotanists argue that it all but disappeared at the end of the Permian). Glossopteris, so prevalent in the Permian, was outdone by another seed fern called Dicroidium. This seed fern spread like a plague over Triassic Pangaea. Dicroidium’s leaves resembled those of modern ferns, except they were forked, giving the appearance of two leaves joined at the base. Like Glossopteris they were deciduous trees, leaving their leaves seasonally. Dicroidium flourished in all Triassic environments, from heath and woodlands to broad-leafed forest. In some locales it’s the only plant present in the Triassic fossil-beds. A third seed fern, Psaronius, lacked Dicroidium’s success but is notable in that it could grow up to thirty feet tall.

a rauisuchian wanders among a grove of cycads

Another type of Triassic gymnosperm was the cycads, seed plants that emerged in the Carboniferous Period. They’re still around today, but only sparsely compared to their prevalence in the Mesozoic. Most cycads have a stout and woody trunk with a crown of large, hard, stiff, evergreen leaves. Their leaves are usually pinnate (arranged in a feather-like pattern) and grow in a rosette form from the top of the trunk. Cycads have a cylindrical trunk; as the trunk grows, the leaves – which are generally the same size or larger than the trunk – sprout only from the top, so that cycads are marked by a crown of leaves at their top. Some cycads’ trunks are buried underground, giving the cycad an appearance like a forest-hugging fern. Cycads reproduce by a cone sprouting from the top of the trunk in the middle of the leaves. Cycads are slow growers and can live up to a thousand years. They are only distantly related to palms and ferns, despite their obvious similarities. During the Triassic and Jurassic Periods, cycads comprised twenty percent of the earth’s plant life (paleobotanists sometimes refer to the Triassic-Jurassic as the Age of the Cycads). Cycads formed the ground cover of the Mesozoic: these primitive cycads were stumpy, with round or barrel-like stems, or they had tall, slender trunks topped by a tuft of palm-like leaves. Though cycads never reached the height of Triassic conifers, some could rise up to five to ten feet in height. Common Triassic cycads include Leptocycas, Cycas, Zamia, Dioon, Bowenia, Stangeria, and Microcyas. Similar in appearance to cycads – with thick woody trunks and tough, palm-like leaves – were the Bennettitaleans; these plants resembled cycads but differed in the arrangement of their stoma. Bennettitaleans appeared in the Triassic, but they could never compete with the cycads, and they dwindled to extinction at the end of the Cretaceous with the rise of the flowering plants.

a modern 'maidenhair' ginkgo tree, a 'living fossil' dating back to the Triassic

Another type of seed-bearing plant, ginkgos, appeared in the Permian Period. They flourished in the Jurassic but waned in the Triassic; they went all but extinct in the Pliocene. We say ‘almost’ because there is an exception: Ginkgo biloba, the ‘maidenhair tree,’ considered a ‘living fossil’ since its undergone very little change from its emergence in the Permian. This tree grows in the wild only in China, and it can reach 65 to 115 feet tall (some have even reached over 160 feet in height). The maidenhair has an angular crown and long, erratic branches; it’s deep-rooted and resistant to wind and snow damage. Young maidenhairs are tall and slender and sparsely branched; the crown becomes broader as the tree ages. The maidenhair leaves are fan-shaped with veins radiating out into the leaf blade; every autumn the leaves turn a bright yellow before falling. One can envisage a Triassic dinosaur standing under the branches of a maidenhair and thus capture an accurate image from the past.

a modern 'monkey puzzle tree' rises above the forest canopy in Brazil

Conifers, which dominate much of our present world, emerged during the early Triassic and crawled to dominance through the Mesozoic. The eight conifer families that exist today are represented in Triassic-era fossils. Conifers are typified by a pyramidal growth in many species, along with needle- or scale-like and often waxy leaves. Conifers have a pollen tube that delivers sperm directly to the eggs, making them more reproductively advanced than other Triassic seed-bearing plants. Conifers excelled in the Triassic’s drier climate, especially in the arid interior. Examples of Triassic conifers include Mataia and Rissikia, though the most common was Araucarioxylon. This last conifer could reach up to hundred feet in height and measured more than two feet in diameter. Their fossilized bark is often scoured by boreholes made by ancient beetles. Araucarioxylon was the dominant tree in the northern hemisphere, where its trunks reached high above the cycads and ginkgoes; in the south, Araucarioxylon were common, but the warmer, wetter climate forced them to compete for space with other plants. An honorable mention is the Araucaria, or monkey puzzle tree. These evergreen conifers emerged during the Triassic and have lasted to the present day. Modern monkey puzzle trees are considered ‘living fossils.’ They can reach between 100-250 feet in height. Their horizontal, spreading branches grow in whorls and are covered with leathery- or needle-like leaves. In some species the leaves are narrow and awl-shaped, barely overlapping; but in others they are broad and flat, overlapping broadly. Some paleontologists believe that the long necks of sauropod dinosaurs evolved specifically to browse the foliage of the tallest money puzzle trees; their global distribution in vast forests during the Jurassic makes it likely that they were the major high energy food source for adult sauropods. 

~  The Triassic-Jurassic Extinction Event  ~

The ‘dividing line’ between the Late Triassic and the Early Jurassic is an extinction event caused by the supercontinent Pangaea ripping apart. Pangaea was created during the Permian as earth’s tectonic plates crunched together (the Appalachian Mountains were created by this ancient event). One of earth’s most recent mountain ranges, the Himalayas, were created long after the Mesozoic by the collision of India with the southern edge of the Eurasian plate; scientists speculate that the rising Himalayas disrupted global air circulation, creating monsoons and helping to nudge the earth into a prolonged phase of cooling and drying that culminated in the Cenozoic Ice Ages. The earth’s crust is divided into broad, rigid, and constantly moving plates that float on firmer layers of mantle. When the plates interact, the result is geological activity (think earthquakes, growing mountain ranges, and volcanoes). The drifting and interacting of tectonic plates is called ‘continental drift.’ On the ocean floor are mid-oceanic ridges where new sea floor is being created; where sea floor is being destroyed, the result is ocean trenches (as an aside, the oldest known ocean floor dates back to the Jurassic Period). The pattern of these ridges and trenches reveal a pattern of gargantuan ‘plates’ that behave like lumbering, slow-moving conveyor belts carrying the continents around the earth’s surface. The process is driven by convection currents in the mantle that are created by the intense heat running through our planet’s core. Earth’s tectonic plates move at a snail’s pace of about four centimeters (1.6 inches) each year, about the same rate as the growth of human fingernails. Over the vast spans of geological time, the plates move about twenty-five miles every million years.

The plates were moving in the Late Triassic just as they’re moving now; but as the Permian saw the formation of the supercontinent Pangaea, the Late Triassic saw the genesis of its breakup. As Pangaea began to split (the upper portion would become ‘Laurasia’ and the southern portion ‘Gondwana’), it stretched at the seams, creating ‘rift basins.’ The shallow bowls of stretched earth were often filled with water, creating lakes and rivers; many would seasonally dry out, resulting in fantastic ‘bone beds’ for future paleontologists. As the stretching intensified, the ripping began. Pangaea ruptured along the modern-day U.S. eastern seaboard (the Palisades in New York are remnants of this split), and the rift basins were inundated by volcanic lava flows. There would be four cycles of mass eruptions before Pangaea finally split down the middle, and the process took about half a million years. These volcanic ‘pulses’ weren’t meager little things: they sent tsunamis of lava surging across the Late Triassic landscape. This is no exaggeration, as some of the lava flows reached up to three thousand feet in thickness. These lava tsunamis could’ve buried the Empire State Building twice over.

Three million square miles of central Pangaea were buried by lava, and the effect on climate was catastrophic. Survival wasn’t just a matter of hoofing it away from the split; the split itself initiated a domino-effect of rising greenhouse gases that makes today’s climate change scare look like amateur hour. The climate change would wipe out thirty percent of earth’s species and help the emergent dinosaurs break out of their slump and diversify into the dominant creatures of the Mesozoic. The intense volcanism spewed carbon dioxide, a ‘greenhouse gas’ (so-called because it warms the planet), into the atmosphere. As the oceans warmed due to the increased carbon dioxide, clathrates melted; clathrates are chunks of ice buried in the seafloor in which methane is trapped, and when clathrates melt, the trapped methane – another greenhouse gas – is released. The unchained methane piggybacked on the carbon dioxide, and the greenhouse gases in the atmosphere tripled within a few tens of thousands of years. The planet’s temperature warmed at a nauseating pace, and life struggled to keep tempo. The ocean became more acidic, resulting in the collapse of marine food webs; shellfish were particularly hard-hit. The climate became more variable: periods of intense heat were followed by rapid cooling, megamonsoons became far more severe, and coastal regions became wetter while interior regions became drier. The hotter temperatures led to the death of ninety-five percent of plant life; herbivores suffered from the lack of food, and the carnivores that preyed upon them suffered in turn. Most reptiles, amphibians, and early mammals died out.

Late Triassic trackways (in which we catch glimpses of the footprints of ancient creatures) tell the grim story. Before the volcanic deluge, dinosaurs made up twenty percent of the trackways; afterwards, they’re pretty much the only tracks left – and they diversify like mad. Historian Steve Brusatte notes, “After some of the largest volcanic eruptions in Earth history desecrated ecosystems, dinosaurs became more diverse, more abundant, and larger. Completely new dinosaur species were evolving and spreading into new environments, while other groups of animals went extinct. As the world was going to hell, dinosaurs were thriving, somehow taking advantage of the chaos around them.” (97) He continues, “Somehow dinosaurs were the victors. They endured the Pangaean split, the volcanism, and the wild climate swings and fires that vanquished their rivals.” (98) No one knows why this was the case, but the Jurassic was theirs for the taking. “Was there something special about dinosaurs that gave them an edge over the pseudosuchians and other animals that went extinct? Did they grow faster, reproduce quicker, have a higher metabolism, or move more efficiently? Did they have better ways of breathing, hiding, or insulating their bodies during extreme heat and cold snaps?” (98) The answers aren’t forthcoming, but what is known is that the Jurassic would play host to a menagerie of creatures wholly different from the period that preceded it. The Jurassic was a warmer planet than it had been in the Triassic. Storms were more intense, and wildfires lighted with ease. New types of ferns and ginkgoes replaced the broadleaf conifers of the Late Triassic. And most of the life-forms that called the Triassic home weren’t around to see it.

The supersalamander amphibians? They were gone.

The piglike dicynodonts? Gone.

The beaked rhynchosaurs? Gone.

The long-snouted phytosaurs, the tank-like aetosaurs, and the apex-predator rauisuchians were gone, gone, GONE.

And the pseudosuchians? They were almost wiped out. The only traces of them were a few types of primitive creatures that would eventually evolve into modern alligators and crocodiles, but they would never again enjoy the success they’d claimed in the Triassic.