the reformation: one year

It's officially been one year since I started working to get back in shape. I've hit my goal of 160 pounds, which is thirty pounds lost (woohoo!), and it feels good to fit back into clothes I optimistically kept when I 'outgrew' them three years ago. It hasn't been an easy journey, and there's been plenty of mess-ups. Over the months I've had to constantly tweak my diet and exercise regimens as I become more knowledgeable in healthy living. I still have a lot of work to do (my belly and 'back fat' are rather stubborn, which is a pretty common theme), and I'm excited to see more changes in the months ahead. Here's a 'before and after' from November of last year to late October of this year (190 pounds to 160 pounds):

This month I'm doing a harsh cut and joining a 'pull-up bar' challenge. Basically this means I'm going low carb (less than 130 grams a day max) and high protein (around 140 grams a day) and focusing mostly on exercises that involve a pull-up bar. I'm also trying to work more on my legs (though they're getting better, I've still got that 'chicken leg' syndrome going on) and on my forearms (I've had a hard time building them up, probably because I have a small wrist; there's a correlation between forearm strength and wrist size). The forearm is a big deal, because I've gotten to where I can lift pretty heavy in bicep curls, but my forearms are threatening to blow out even before my biceps feel strained. We'll see how it goes! I'm hoping to get down to 145 by the turn of the new year, which would put me solidly in the NOT overweight category.

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