Thecodontosaurus antiquus (Riley & Stuchbury 1836) Norian, Late Triassic ~ 218 mya, ~1.8 m in length was a plant eating dinosaur at the base of the sauropodomorpha, not far from ancestral theropoda. Derived from a sister to Daemonosaurus, Thecodontosaurus was ancestral to later prosauropods and sauropods, the largest of all land animals.
Distinct from Daemonosaurus, the skull of the short rostrum Massosondylus (on the left, substituting for the skull-less Thecodontosaurus) had a reduced premaxillary post-narial process, like all dinosaurs. The naris was larger. The teeth, while still long, were shorter and the serrations were larger and fewer. The premaxilla carried four teeth. The maxilla was shallower and straighter. The lateral temporal fenestra was shorter. The The mandible was deeper anteriorly. No fangs erupted from the mandible.
A few more cervicals were present.
The scapula and coracoid were more gracile, the humerus was more robust, and the forearm was shorter. Three fingers were well-developed with large claws and two were mere vestiges.
The pelvis was longer and the pubis was deeper.
Massospondylus kaalae was a short-snouted basal sauropodomorph with fangs that likely was more closely related to Daemonosaurus and Heterodontosaurus. All three had a short round snout and long fangs, among other shared traits. Another species, Massospondylus carinatus, had a longer skull with a relatively shorter dentary that might have once had a predentary bone, as in Lesothosaurus and Silesaurus. |
