Plateosaurus

Plateosaurus — Plateosaurus (meaning ’flat lizard’) is a genus of plateosaurid prosauropod dinosaur that lived during the Norian and Rhaetian stages of the Late Triassic period, around 216 to 199 million years ago in what is now Europe. There are two currently recognized species, P. engelhardti and P. longiceps, although others have been assigned in the past.

Discovered in 1834 and described three years later, Plateosaurus was one of the first dinosaurs formally named, although not one of the three genera originally used to define Dinosauria, because at the time it was poorly known and impossible to identify as a dinosaur. Plateosaurus were bulky bipedal herbivores which had small skulls on long necks, sharp plant-crushing teeth, powerful limbs, and large thumb claw on each ’hand’ probably used for defense and feeding.

The skull of Plateosaurus was deeper than that of Coelophysis — i.e. a stronger, deeper head than most prosauropods, although still small and narrow compared to the size of its body. It had four sets of fenestrae (skull openings); these openings were for the naris and orbit as well as an infratemporal fenestra at the back of the skull and an antorbital fenestra between the eye and nose. It had a long snout and many small, leaf-shaped, socketed teeth and the low-slung hinge of its lower jaw, which give the muscles greater leverage. These features suggest that it fed exclusively on plants. Its eyes were directed to the sides, rather than the front, providing all-round vision to watch for predators. Some fossil skeletons have preserved sclerotic rings.

Plateosaurus had numerous small teeth in both the upper and lower jaw, five to six on the premaxilla, twenty four to thirty on the maxilla, and twenty one to twenty eight on the dentary. These teeth had serrated, leaf-shaped crowns suitable for digestion of plant material. It is thought Plateosaurus had narrow cheek pouches which kept food from spilling out when it ate.

Plateosaurus was the largest known dinosaur of its time, reaching 6 to 10 meters in length and up to an estimated 700 kg in mass. A member of the group of early herbivores known as prosauropods, it was more powerfully built than that of similar animals such as Anchisaurus. Plateosaurus had a long neck, composed of around nine cervical vertebrae, a stocky body and a pear-shaped torso. It had a long tail composed of at least forty caudal vertebrae which served to counterbalance the front-heavy body and long neck.

Plateosaurus was an obscure dinosaur up until the past century, with very scant material known and few detailed studies. Over time, new discoveries and researches have given researchers more information about its locomotion, feeding mechanisms and metabolism.

The small leaf-shaped teeth of Plateosaurus indicate it was an herbivore, one of the first large dinosaurs that browsed in tall vegetation like conifers and cycads, supported by its long neck. Like its relative Massospondylus, it might have swallowed gastroliths (gizzard stones) to digest food because of the lack of cheek teeth.