| Orthopus | |
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| Genus: | Orthopus |
Orthopus is an extinct genus of non-mammalian synapsids. It is based on a partial humerus that closely resembles Estemmenosuchus, in the limited comparisons possible.
Synapsids are a group of animals that includes mammals and every animal more closely related to mammals than to the other members of the amniote clade, such as reptiles and birds. Unlike other amniotes, they have a temporal fenestra, an opening low in the skull roof behind each eye, leaving a bony arch beneath each; this accounts for their name. Primitive synapsids are usually called pelycosaurs or pelycosaur-grade synapsids. This informal term consists of all synapsids that are not therapsids, a monophyletic, more advanced, mammal-like group. The non-mammalian synapsids were described as mammal-like reptiles in classical systematics, but this misleading terminology is no longer in use as synapsids as a whole are no longer considered reptiles. They are now more correctly referred to as stem mammals or proto-mammals.
Sauropsida is a clade of amniotes, broadly equivalent to the class Reptilia. Sauropsida is the sister taxon to Synapsida, the clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles," all synapsids are more closely related to mammals than to any modern reptile. Sauropsids, on the other hand, include all amniotes more closely related to modern reptiles than to mammals. This includes Aves (birds), which are now recognized as a subgroup of archosaurian reptiles despite originally being named as a separate class in Linnaean taxonomy.
James Allen Hopson is an American paleontologist and professor at the University of Chicago. His work has focused on the evolution of the synapsids, and has been focused on the transition from basal synapsids to mammals, from the late Paleozoic through the Mesozoic Eras. He received his doctorate at Chicago in 1965, and worked at Yale before returning to Chicago in 1967 as a faculty member in Anatomy, and has also been a research associate at the Field Museum of Natural History since 1971. He has also worked on the paleobiology of dinosaurs, and his work, along with that of Peter Dodson, has become a foundation piece for the modern understanding of duckbill crests, social behavior, and variation.
Admetophoneus is a dubious genus of non-mammalian synapsid from Russia. Its type and only species is Admetophoneus kargalensis.
Calleonasus is an extinct genus of non-mammalian synapsid from the Anisian Donguz Formation of Russia.
Driveria is an extinct genus of non-mammalian synapsids the Lower Permian of San Angelo Formation, Texas.
Cromptodon is an extinct genus of cynodonts from the Triassic of Cerro Bayo de Portrerillos, Cerro de las Cabras Formation, Argentina, South America. It is known only from PVL 3858, a mandible.
Cryptocynodon is an extinct genus of non-mammalian synapsid from the Cistecephalus Assemblage Zone of the Beaufort Group in South Africa,
Eurychororhinus is an extinct genus of non-mammalian synapsid.
Emyduranus is an extinct genus of non-mammalian synapsid from the Permian Cistecephalus Assemblage Zone and the Teekloof Formation of the Beaufort Group, South Africa.
Elatosaurus is an extinct genus of non-mammalian synapsid.
Ictidostoma is an extinct genus of non-mammalian synapsids known from the Tropidostoma Assemblage Zone.
Koupia is an extinct genus of non-mammalian synapsid.
Lanthanostegus is an extinct genus of non-mammalian synapsids from the Capitanian Tapinocephalus Assemblage Zone, Koonap Formation of South Africa.
Notosyodon is an extinct genus of non-mammalian therapsids. The holotype PIN 2505/1, consists of a partial skull preserving the orbital, occipital, and basicranial regions. Other remains include PIN 2505/2, a right lower incisor, and PIN 2505/3, a left upper postcanine, found associated with the holotype and PIN 2608/1, the anterior half of a left dentary found on the right bank of the Donguz River, near Dolmatovskii Farm, Sol-Iletsk District, Orenburg Region, Russia.
Nitosaurus is an extinct genus of non-mammalian synapsids.
Rhinodicynodon is an extinct genus of non-mammalian synapsid of the Middle Triassic (Anisian) Donguz Formation of European Russia.
Trichasaurus is an extinct genus of non-mammalian synapsids.
Synostocephalus is an extinct genus of non-mammalian synapsid.
Leontosaurus is an extinct genus of non-mammalian synapsids from the Dicynodon Assemblage Zone, Balfour Formation of South Africa. It contains the single species L. vanderhorsti.
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