Dino of the Week: Isaberrysaura

Type Species: Isaberrysaura mollensis

Classification: Dinosauria – Ornithischia – Thyreophora – Stegosauria 

Time Period: Middle Jurassic

Location: South America (Argentina) 

Diet: Herbivore 

Isaberrysaura was an early stegosaur of South America that had yet to be regulated to fully quadrupedal locomotion. It grew to sixteen to twenty feet in length, making it slightly longer than its Laurasian contemporary Lexovisaurus. Its teeth were heterodont (of different types), and similarities in dentition with modern iguanas indicates that Isaberrysaura may have been omnivorous. We know for certain that it ate plants, because the type specimen was discovered with its stomach contents fossilized for science’s delight. Within the rib cage, a mass of fossilized seeds was discovered, the first preserved meal uncovered in a basal ornithischian. Two types of seeds were present: the largest were preserved in three layers (an outer fleshy sarcotesta, the sclerotesta, and an inner layer that may have been the nucellus); these larger seeds belonged to a cycad of the Zamiineae family. The origin of the smaller seeds are unknown. Because the cycad seeds were swallowed whole, rather than chewed, we can infer that they were in the first stages of digestion in Isaberrysaura’s gut. Scientists speculate that its gut contained enzyme-producing bacteria that aided in the digestion of the tougher seed material.