The Rise And Fall Of Anapsids

In the Permian period they were well established and diverse, showing a wide range of body types, diets and lifestyles. This even included some small aquatic varieties called Mesosaurs. The middle of the Permian was the golden age for the anapsid reptiles. They were spread worldwide and in great numbers, but after this they started to decline.

The massive extinction event at the Permian / Triassic boundary wiped out all but one group of the parareptiles, that being the Procolonophoidea, but these did not see out the Triassic.

Parareptiles

This group is increasingly being referred to as the para-reptilia. This is because they were not related to the other main groups of reptiles that gave rise to modern forms. The name means "parallel to other reptiles" and does not imply that these creatures are not reptiles themselves.

The evolutionary relationships between the parareptile groups has been heavily studied in recent years. Scientists have determined that these animals do indeed represent a single family of animals. They know this because all parareptiles share certain features of the skull that are not seen in other groups.

Family Relations

The diagram below shows the most accepted version of the relationships of groups of these reptiles. Click on areas of interest to learn more about groups or species.

	Anapsid ancestor (s)
Millerettidae	Procolophonia	Bolosauridae	Acleistorhinus
		Nyctiphruretia (?)	Lanthosuchidae
	Hallucicrania	Procolophonoidea
	Pareiasauria	Owenettidae	Procolophonidae
turtles (?)	Bradysaurus	Velosauria	Scutosaurus

Are Turtles Anapsids?

You don't have to dig around in the literature for very long at all before this question pops up. From the analysis papers I've read, turtles do indeed fit into the parareptile grouping. They share many skull features with parareptiles. Not only that, but the enigmatic hooked fifth metatarsal that has drawn many to suggest they are diapsid reptiles has been shown to give no cause to split turtles away from the parareptilia. Also, studies of the embryological development of turtles further supports this view.

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