''Nikkasaurus'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
therapsid
Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...
s first named and described by
Ivakhnenko.
Description
''Nikkasaurus'' was a small therapsid, with a
skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
about 5 cm long. The
eye
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
s had large
orbits
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...
and
sclerotic rings
Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are b ...
, and the head was tilted back, as with all therapsids. The skull looks superficially similar to those of the
pelycosaurs
Pelycosaur ( ) is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term ''mammal-like reptile'' had been used, and pelycosaur was considered an order, but this is no ...
, in particular members of
Varanopidae
Varanopidae is an extinct family of amniotes that resembled monitor lizards and may have filled a similar niche, hence the name. Typically, they are considered synapsids that evolved from an ''Archaeothyris''-like synapsid in the Late Carbonifer ...
.
Biology
''Nikkasaurus'' was probably mainly
insectivorous
A robber fly eating a hoverfly
An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects.
The first vertebrate insectivores were ...
, and possibly
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
.
Systematics
The only known species is the type species ''N. tatarinovi'', described by MF Ivahnenko in 2000, from the
Middle Permian
The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0. ...
Mezen River Basin. ''Nikkasaurus'' is possibly a relic of a more ancient stage of
therapsid development.
[M. F. Ivakhnenko. 2008. Podklass Ophiacomorpha. In M. F. Ivakhnenko and E. N. Kurochkin (eds.), Iskopaemye pozvonotchnye Rossii i sopredel'nykh stran: Iskopaemye reptilii i ptitsy, Tchast' 1 ossil vertebrates of Russia and adjacent countries: Fossil reptiles and birds, Part 1 GEOS, Moscow 95-100]
See also
*
List of therapsids
This list of therapsids is an attempt to create a comprehensive listing of all genera that have ever been included in the Therapsida excluding mammals and purely vernacular terms. The list includes all commonly accepted genera, but also genera tha ...
References
* Kemp, Thomas Stainforth (2005). ''The Origin and Evolution of Mammals''. .
Prehistoric therapsid genera
Guadalupian synapsids of Europe
Guadalupian genus first appearances
Guadalupian genus extinctions
Permian Russia
Fossils of Russia
Fossil taxa described in 2000
{{paleo-therapsid-stub