Eodromaeus murphi (Martínez et al 2011; Late Triassic, 230 mya, PVSJ 560 1.2m), nests with Barberensuchus and Eoraptor in the large reptile tree at the very base of the Phytodinosauria. It was a generalized, basal dinosaur with a small head, long-ish neck, long torso, and relatively large forlimbs.
Closely related to basal theropods, like Tawa, Eodromaeus has these distinct traits:
- lateral rostral shape: convex and smoothly curved (also in ancestral Herrerasaurus and Gracilisuchus)
- premaxilla/maxilla angle 25–45º
- naris shape in lateral view almost round (not longer than tall or taller than long)
- postfrontal has no contact with the upper temporal fenestra
- opisthotic oriented laterally without posttemporal fenestrae
- palatal teeth (only on basalmost taxa)
- maxillary tooth depth ≤ 2x width in lateral view
- last maxillary tooth at mid orbit (also in Herrerasaurus)
- olecranon process present (convergent in Buriolestes)
- metacarpals 2 and 3 align with m1.1 (except Eodromaeus)
- acetabulum laterally oriented (no ventral deflection, as in basal theropods)
- femoral head with neck and offset (appears later in theropods)
- penultimate manual phalanges not the longest in each series
- loss of pubic boot (likely plesiomorphic because outgroups to Herrerasaurus do not have a pubic boot).
Eodromaeus had a taller rounder rostrum, shorter teeth, a higher coronoid process, a longer dorsal region with more robust dorsal vertebrae, reduced gastralia, a more robust pectoral girdle and forelimb with shorter, less raptorial fingers, a deeper pubis and ischium with more robust hind limbs. The shorter teeth and larger belly together with the more robust limbs and back are traits seen in a wide variety of herbivores, even if only transitional at this early stage. |
