Nycteroleterids Temporal range: Middle Permian, 264–259.1 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
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]
See text

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]

Classification

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]

Subdivisions

• Subfamily † Nycteroleterinae
  • †Nycteroleter
  • †Emeroleter
• Unassigned subfamily
  • †Bashkyroleter
    • † Bashykroleter mesensis
  • †Macroleter
  • †Rhipaeosaurus

Features

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, postparietal 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]