''Rhipaeosaurus'' is an
extinct genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of
nycteroleterid parareptile known from an articulated skeleton from the mid
Middle Permian of
European Russia. It contained a single
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
, ''Rhipaeosaurus tricuspidens''.
A
bayesian analysis suggests that it is more closely related to
pareiasaurs than to the other nycteroleterids, due to skull and tooth features. For this reason, "Nycteroleteridae" may be a
grade rather than a
clade, unless redefined to exclude ''Rhipaeosaurus''.
Description
''Rhipaeosaurus'' is around a meter long, larger than any other "nycteroleterids" and closer in size to later pareiasaurs. Postcranial remains were similar to ''
Macroleter'', though the limbs were more robust and the ankle bones were unfused.
The teeth were flattened and tricuspid (possessing three
cusps), seemingly intermediate in form between the one- or two-cusped teeth of earlier nycteroleterids and the multi-cusped teeth of pareiasaurs.
Many components of the partial skull and skeleton (which was originally fairly complete) had been lost or degraded between 1940 and 2012, obscuring most aspects of its anatomy.
History
''Rhipaeosaurus'' was first described in 1940, from a fairly complete skeleton found in the
Ural Mountains of Russia. The name 'Rhipaeosaurus' comes from 'Ῥιπαεος' 'Rhipaeos, a range of mountains in
Greek mythology
A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities of ...
thought to be the Urals, and '', meaning 'lizard'. 'Tricuspidens' refers to its three-cusped teeth.
''Rhipaeosaurus
taxonomic history has been full of difficulties. At first it was placed in its own
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
, the Rhipaeosauridae, and considered the type species. Other taxa, such as ''
Parabradysaurus
''Parabradysaurus'' is an extinct genus of estemmenosuchid dinocephalians. It is known from a few serrated teeth that indicate this animal was like herbivorous.
See also
* List of therapsids
This list of therapsids is an attempt to create a co ...
'' and ''
Leptoropha,'' later joined it in this family. However, when more remains of these additional taxa were found, they were determined not to be rhipaeosaurids at all. ''Parabradysaurus'' was found to be an
estemnosuchid, more closely related to
mammals, and ''Leptoropha'' was identified as a
seymouriamorph amphibian. ''Rhipaeosaurus''
's status as a parareptile is still considered relatively stable, either as a basal nycteroleterid or a transitional taxon between other "nycteroleterids" and pareiasaurus.
References
External links
The Paleobiology Database
Permian reptiles of Europe
Pareiasauromorphs
Fossil taxa described in 1940
Prehistoric reptile genera
{{paleo-reptile-stub