Pumiliopareiasauria
| Pumiliopareiasaurians Temporal range: Middle Permian-Late Permian, 260–252 Ma | |
|---|---|
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| Life restoration of Anthodon | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Procolophonomorpha |
| Family: | †Pareiasauridae |
| (unranked): | †Pumiliopareiasauria Jalil and Janvier, 2005 |
| Genera | |
Pumiliopareiasaurians are a group of pareiasaurid reptiles.These are the dwarf pareiasaurs, the most highly derived, the heavily armoured, and turtle-like of the group, that only appear at the end of the Permian. Anthodon and Pumiliopareia share numerous and striking postcranial traits with turtles.
Origin of turtles
The idea that turtles are actually highly derived pareiasaurs was strongly argued on cladistic grounds by Michael Lee in a series of innovative papers (Lee, 1993, 1995, 1997, 2001 ), and supported by Jalil & Janvier (2005). Thus, pareiasaurs had turtle-like cranial features, and it is not hard to imagine dermal ossicles and scutes, embedde din the skin or attached to the skull, vertebrae, progressively evolving into bony plates,and finally fusing into a turtle shell. There is also a progressive morphological sequence, showing pareiasaurs becoming progressively more heavily armoured and then, after a series of giant forms, progressively smaller. Pareiasaurs evolving into turtles also has a coolness factor rather like dinosaurs evolved into birds. The question of a pareiasaur origin for turtles and tortoises is a lot more controversial, and, unlike dinosaurs to birds, there are some strong rivals. deBraga & Rieppel, (1997) argue that pareiasaur scutes are not homologous with the turtle shell and show that many features of turtles, especially the limbs, suggest sauropterygia and lepidosauromorph relationships. Meanwhile, molecular phylogeny consistently places turtles among the archosaurs. Recently the eunotosaur ancestry hypothesis has been revived. None of these hypotheses is without controversy, but if pareiasaurs are not turtle ancestors, rather than evolving into turtles, pareiasaurs were evolving parallel to them. As such, pareiasaurs would represent "prophetic forms" rather than true ancestors.
External links
- Elginiidae and Pumiliopareiasauria at Palaeos