Ankylosphenodon
From Wikipedia, the free encyclopedia
| Ankylosphenodon Temporal range: | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Rhynchocephalia |
| Suborder: | Sphenodontia |
| Infraorder: | Eusphenodontia |
| Clade: | Neosphenodontia |
| Family: | Sphenodontidae |
| Genus: | †Ankylosphenodon Reynoso, 2000[1] |
| Species | |
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Ankylosphenodon is an extinct genus of sphenodontian known from multiple specimens recovered from the Early Cretaceous deposits of the Tlayúa Formation, near Tepexi de Rodriguez, Mexico.[1] It is likely part of a sphenodontid lineage that also includes Eilenodon and Toxolophosaurus, though has similarities to the sapheosaur clade. Its skeleton is pachyostotic (thickened) skeleton, believed to be an adaptation for a semi-aquatic lifestyle. Its teeth appear to have grown continuously, like in rodents.
Discovery and formal description
Ankylosphenodon is known from multiple specimens recovered from the Tlayúa Formation, a vertebrate-rich Lagerstätte near Tepexi de Rodriguez, in Central Mexico. The holotype (IGM 7441) is a partial skeleton, consisting of a skull, the left forelimb, and the front half of the presacral vertebral column. Another specimen, IGM 7443, preserves most of the right forelimb and the rear half of the body, minus the tail.[1] All specimens were recovered from the Tlayúa Quarry, which, represents the Middle Member of the Tlayúa Formation,[2] a Lagerstätte rich in vertebrate fossils.[3] On collection, the specimens were transported to the Geological Institute of the National Autonomous University of Mexico. In 2000, Víctor-Hugo Reynoso formally described the genus. The generic name comes from Sphenodon, the generic name of the modern tuatara, and the Greek ἀγκύλος (ankylos), meaning "fused" or "bent", referring to the thickening of its ribs and vertebrae.[1]
Classification
The strict consensus tree in Reynoso's paper on Ankylosphenodon recovers it as part of a small, unnamed clade within Sphenodontidae, one that also includes Eilenodon and Toxolophosaurus. Similarities with sapheosaurs were noted, though were ascribed to convergence.[1] However, Sebastian Apesteguía, in 2005, suggested that it was in fact a sapheosaur.[4]
