The Hanson Formation of the Central Transantarctic Mountains has yielded a diverse Early Jurassic
terrestrial fauna, which includes the nearly complete theropod dinosaur, Cryolophosaurus ellioti, and a fragmentary
basal sauropodomorph dinosaur. The Hanson Formation dinosaurs are important for understanding early dinosaur
evolution because: 1) they preserve a mosaic of morphological traits that render them useful for interpreting poorly
known parts of the dinosaur evolutionary tree; 2) they are from the Early Jurassic, a critical period in early dinosaur
evolution about which knowledge is scant; and 3) they are the only known Early Jurassic dinosaurs from Antarctica,
making them particularly valuable for understanding patterns of biotic interchange during this time. Recent research
suggests that Cryolophosaurus belongs to a geographically widespread clade of mid-sized, Early Jurassic theropods
with cranial crests that includes Dilophosaurus wetherilli, ‘Dilophosaurus’ sinensis, and Dracovenator, and renders
Coelophysoidea sensu lato non-monophyletic. The Antarctic sauropodomorph represents a distinct taxon that is a
member of a similarly diverse massospondylid clade. This taxon shares a number of features with more derived
sauropodomorphs, and provides additional evidence for the paraphyly of Prosauropoda. The phylogenetic relationships
of the Antarctic dinosaurs are also consistent with a pattern of worldwide faunal homogeneity between Early Jurassic
continental biotas. Furthermore, these analyses support a “ladder-like” arrangement for basal theropod and basal
sauropodomorph phylogeny, suggesting that these groups passed through “coelophysoid” and “prosauropod” stages of
morphological organization early in their respective evolutionary histories.
