| Tepexisaurus | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Infraorder: | Scincomorpha |
| Genus: | †Tepexisaurus Reynoso & Callison, 2000 |
| Type species | |
| †Tepexisaurus tepexii Reynoso & Callison, 2000 | |
Tepexisaurus is agenus of extinctscincomorph lizard from theEarly Cretaceous (lateAlbian)Tlayúa Formation, aLagerstätte nearTepexi de Rodríguez, CentralMexico. One species,T. tepexii, is known. It was likely related toScincidae (skinks),Cordylidae (girdled lizards), andParamacellodus.
Theholotype ofTepexisaurus (IGM 7466), a well-preserved skeleton with a disarticulated head/neck and part of the tail missing, was recovered from the Tlayúa Quarry, nearTepexi de Rodríguez in Central Mexico. The specific locality in which it was discovered, represent the MiddleMember of theTlayúa Formation,[1] aLagerstätte rich in vertebrate fossils. The depositional environment of the Middle Member was a shallowlagoon fringed by apeneplain.[2] On collection, the specimen was transported to the Geological Institute of theNational Autonomous University of Mexico. In 2000, it was formally described by Victor-Hugo Reynoso and George Callison. Thegeneric name derives from Tepexi de Rodríguez and the Latinsaurus ("reptile").[1]
In their paper describingTepexisaurus, Reynoso and Callison performed severalphylogenetic analyses. The strict consensus tree they recovered nestedTepexisaurus withinScincomorpha, as thesister taxon of a clade includingCordylidae,Paramacellodus, andScincidae.[1]
The skull length ofTepexisaurus' holotype, measured from the tip of thepremaxilla to theoccipital condyle, is 2.33 cm (0.92 in). The total length of the holotype, as preserved, is around 18.6 cm (7.3 in).[1]
Tepexisaurus' snout measured about one-third of its total skull length. Due to the manner in which the holotype was preserved, many details of the skull are obscured. It is not known whether thepremaxillae are fused. The parietal bones bear two crest-like processes that form part of the braincase wall. Their ends are swollen, similar to the condition seen incordylids.Tepexisaurus' teeth arepleurodont, the typical condition among squamates, and closely resemble those of the EuropeanparamacellodidBecklesius. The teeth of the mandible were long and peg-like. The overall morphology of themandible resembles extantxantusiids. Most of the presacral vertebral column (thecervical anddorsal vertebrae) is preserved, as are twosacral vertebrae, though only six caudal vertebrae are present. Soft tissue traces indicate that the rest of the tail wasautotomised.[1]
The palaeoenvironment of the Tlayúa Formation, from which all specimens ofTepexisaurus are known, was likely a shallow coastallagoon.[3] It may have formed part of an island, though a connection to the North American mainland cannot be ruled out.[2] A certain degree of influence from freshwater environments is indicated by the presence of fossils fromcrocodilians and freshwater turtles.[2]