Arizonasaurus
| Arizonasaurus | |
|---|---|
| |
| Model, Museum am Löwentor, Stuttgart | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Clade: | Pseudosuchia |
| Clade: | Paracrocodylomorpha |
| Clade: | †Poposauroidea |
| Family: | †Ctenosauriscidae |
| Genus: | †Arizonasaurus Welles, 1947 |
| Species | |
| |
Arizonasaurus was a ctenosauriscid archosaur from the Middle Triassic (243 million years ago).[1] Arizonasaurus is found in the Middle Triassic Moenkopi Formation of northern Arizona. A fairly complete skeleton was found in 2002 by Sterling Nesbitt. The taxon has a large sailback formed by elongated neural spines of the vertebrae. The type species, Arizonasaurus babbitti, was named by Samuel Paul Welles in 1947.
Discovery and naming
The type species, Arizonasaurus babbitti, was named by Samuel Paul Welles in 1947 on the basis of a few teeth and a maxilla, labelled as specimen UCMP 36232.[2] A fairly complete skeleton was found in 2002 by Sterling Nesbitt.[3]
Description
Arizonasaurus had a sail made of tall neural spines. This sail was similar to those of other basal archosaurs, such as other ctenosauriscids like Ctenosauriscus, Lotosaurus, Bromsgroveia, and Hypselorhachis.[4]
Arizonasaurus is described from two
Below is a list of characteristics found by Nesbitt in 2005 that distinguish Arizonasaurus:[4]
- a deep fossa hidden from view on the posteroventral edge of the upward-pointing process of the maxilla;
- and a tongue-groove attachment between the pubis and the ilium.
Classification
Arizonasaurus was closely related to
Below is a phylogenetic cladogram simplified from Butler et al. in 2011 showing the cladistics of Archosauriformes, focusing mostly on Pseudosuchia:[5]
| Poposauroidea |
| ||||||||||||||||||||||||||||||||||||||||||
Biogeography
Arizonasaurus is from the middle Triassic Moenkopi Formation of northern Arizona. The presence of a poposauroid in the early Middle Triassic suggests that the divergence of birds and crocodiles occurred earlier than previously thought. Ctenosauriscids from the Middle Triassic allow the distribution of Triassic faunas to be more widespread, now in Europe, Asia, North America and Africa. The fauna of the Moenkopi Formation represents a stage transitional fauna between the faunas of older and younger age.[3]
References
External links
- Artistic rendering of Arizonasaurus babbitti
- Nesbitt, S.J. (2005). "Osteology of the Middle Triassic pseudosuchian archosaur Arizonasaurus babbitti". Historical Biology. 8 (1): 19–47. S2CID 84326151.
- Initial description of complete skeleton by Sterling Nesbitt in Royal Society Biology Letters[permanent dead link]
- Braincase of Arizonasaurus babbitti