EureptiliaThe name eureptilia means "true reptiles". This does not mean that scientists consider Anapsids to be "false reptiles", but rather that the eureptilia are the ones that gave rise to those reptiles still living today.
As with all the major groupings, these reptiles started off as small, non-descript lizard like creatures. The skeleton to the right belonged to a creature named Thuringothyris mahlendorffae. They were probably insectivorous, and it is highly likely that they resembled creatures such as the Australian Eastern blue-tongue lizard (seen below) in both appearance and behavior. That particular creature is about a foot long and lives in the leaf litter, eating insects and other invertebrates.
When these creatures and the animals that were to evolve into the anapsids split and became separate populations, there were very few differences in their structure. The SkullThe skulls of early eureptiles are very similar to those of early anapsid reptiles. Neither have any openings in the outer layer of the skull save for the eye and nose holes. There is also little difference in the layout of the different bones that make up the skulls. While openings in the skull behind the eyes and the arrangement of the bones is important for classifying the descendants of the early eureptiles, those features cannot be relied on here. The TeethOne feature of almost all modern reptiles is the similarity of their teeth. While the teeth along the jaw may vary in size and quantity, they all have essentially the same shape and proportions. This is also true of the early eureptiles. At the same time, the anapsids were to be found with a variety of tooth structures, as shown in the bipedal Bolosaurus. The Hind FootThis is the smoking gun that pins these creatures as the ancestors of living reptiles. All living reptiles and extinct descendents of this group share a hooked fifth metatarsal in the rear feet. Early eureptiles show this feature, whereas otherwise very similar reptiles that gave rise to the parareptilia did not have it. Vast RadiationThe primitive ancestral eureptiles can be seen as the trunk of a very thick and heavily branched bush. All modern forms of reptiles and birds have come from them, with the possible exception of turtles. Consider the vast range of forms, sizes and lifestyles in their living descendents, not to mention extinct forms such as the dinosaurs and phytosaurs. It is easy to be awestruck by the potential of what at first glance appears to be just a stumpy little lizard in the undergrowth. Return from Eureptilia to Reptile Evolution or return to the Reptiles home page. |
