Nycteroleterids Temporal range:
Middle Permian,
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Adult and juvenile skulls of Macroleter (= Tokosaurus) | |
Life restoration of Emeroleter | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | † Parareptilia |
Order: | † Procolophonomorpha |
Clade: | † Pareiasauromorpha |
Family: | †
Nycteroleteridae Romer, 1956 |
Genera [1] | |
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Nycteroleteridae is a family of procolophonian parareptilians (extinct early reptiles) from the Middle to Late Permian of Russia and North America. They are sometimes classified as a sister group to pareiasaurids (but see Classification). The group includes the genera Macroleter, Bashkyroleter, "Bashkyroleter" mesensis, Nycteroleter, Emeroleter, and probably Rhipaeosaurus. They were carnivorous, and occasionally ate insects. [1] The group was most common in European Russia, with only a few fossils in North America. One fossil has also been found in Africa, but this is the only one from Gondwana. [2]
Nycteroleteridae is sometimes considered a sister group to the Pareiasauridae, but Bayesian inference suggests that it was in fact paraphyletic, with Rhipaeosaurus a basal member of the Pareiasauridae and other members of the Nycteroleteridae as outgroups. This is supported by the appearance of Rhipaeosaurus' skull and teeth - it had tricuspid teeth and multiple horns on the skull, resembling a pareiasaur but smaller and with a longer tail. For this reason it is often seen as intermediate between more primitive nycteroleterids and more advanced pareiasaurids such as Scutosaurus. [2]
As discussed above, Nycteroleteridae technically includes all pareiasaurs as well as the five given genera. Within the five genera mentioned, there seems to be a smooth gradient of form from Macroleter to Rhipaeosaurus. Where Macroleter has no horns, Emeroleter has a few small horns, and Rhipaeosaurus' horns are quite large. [2]
However, there are some characteristic features of the Nycteroleteridae. They have a deeply incised otic notch, post parietal bones that enter the pineal opening, regular circular pits in the skull, and a row of palatal teeth from the interpterygoid vacuity to the edge of the choana. [2]
Examination of the nycteroleterids' middle ear bones and comparison with living amniotes showed that they probably had efficient impedance-matching hearing. This suggests that they may have been active at night or in dim-light environments. They are thought to have been carnivorous or insectivorous, but Rhipaeosaurus may have been an omnivore. [2]