''Cynognathus'' 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 nom ...

of large-bodied cynodontian

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 that lived in the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma an ...

. It is known from a single species, ''Cynognathus crateronotus''. ''Cynognathus'' was a long

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

closely related to mammals and had a southern hemispheric distribution.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have so far been recovered from

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Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

, and

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

Description

''Cynognathus'' was a heavily built animal, and measured around in snout-to-vent body length. It had a particularly large head, up to in length, with wide jaws and sharp teeth. Its hindlimbs were placed directly beneath the body, but the forelimbs sprawled outwards in a more reptilian fashion. This form of double (erect/sprawling) gait is also found in some primitive mammals alive today. Possible

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

of ''C. crateronotus'' include an extremely elongated postorbital bar and sectorial postcanine teeth with two serrated cusps distal to a recurved apex.

Discovery and naming

During 1888 and 1889, the British paleontologist

Harry Govier Seeley Harry Govier Seeley (18 February 1839 – 8 January 1909) was a British paleontologist. Early life Seeley was born in London on 18 February 1839, the second son of Richard Hovill Seeley, a goldsmith, and his second wife Mary Govier. When his fat ...

visited southern Africa. In 1889, near

Lady Frere Lady Frere (officially Cacadu) is a small town in Chris Hani District Municipality in the Eastern Cape province of South Africa. The town was renamed to Cacadu in 2017 after changes to the country's colonial names. Cacadu, meaning “bulrush wat ...

, at a location where earlier Alfred Brown had discovered a tooth, Seeley excavated a skull and partial postcranial skeleton of a cynodontian. In 1894, Seeley named the genus ''Cynognathus'' with as

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

''Cynognathus crateronotus''. Simultaneously, he named three other species in the genus: ''Cynognathus berryi'', honouring James Berry who had assisted in the excavations, ''Cynognathus platyceps'', the "flat jaw", and ''Cynognathus leptorhinus'', the "slender nose". The generic name ''Cynognathus'' is derived from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''kyon'' and ''gnathos'', meaning "dog jaw". In 1895, Seeley published a more comprehensive description of these finds. Fossil material probably belonging to the genus has been given several different names over the years. Generic synonyms include ''Cistecynodon'', ''Cynidiognathus'', ''Cynogomphius'', ''Karoomys'', ''Lycaenognathus'', ''Lycochampsa'' and ''Lycognathus''. Opinions vary as to whether all remains belong to the same species. The genera ''Karoomys'' and ''Cistecynodon'' are known only from tiny juveniles. Species-level synonyms of ''Cynognathus crateronotus'' include ''Cistecynodon parvus'', ''Cynidiognathus broomi'', ''Cynidiognathus longiceps'', ''Cynidiognathus merenskyi'', ''Cynognathus berryi'', ''Cynognathus minor'', ''Cynognathus platyceps'', ''Cynogomphius berryi'', ''Karoomys browni'', ''Lycaenognathus platyceps'', ''Lycochampsa ferox'', ''Lycognathus ferox'', and ''Nythosaurus browni''.

Distribution

Fossils have been found in the

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ex ...

, the Puesto Viejo Formation,

Fremouw Formation The Fremouw Formation is a Triassic-age rock formation in the Transantarctic Mountains of Antarctica. It contains the oldest known fossils of tetrapods from Antarctica, including synapsids, reptiles and amphibians. Fossilized trees have also been ...

, in

Lesotho Lesotho ( ), officially the Kingdom of Lesotho, is a country landlocked as an enclave in South Africa. It is situated in the Maloti Mountains and contains the highest mountains in Southern Africa. It has an area of over and has a population ...

and

. ''Cynognathus'' lived between the

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...

and the

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic) ...

(Middle Triassic). This genus forms a '' Cynognathus Assemblage Zone'' in the Beaufort Group of the

Karoo Supergroup The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a peri ...

.Stratigraphic and sedimentological investigation of the contact between the Lystrosaurus and the Cynognathus assemblage zones (Beaufort group: Karoo supergroup). J Neveling - Bulletin of the Council for Geoscience, 2004

Classification

Seeley in 1894/1895 placed ''Cynognathus'' in a separate family Cynognathidae, within the Cynodontia. ''Cynognathus'' is presently the only recognized member of the family Cynognathidae. Later a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

Cynognathia Cynognathia ("dog jaw") is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus '' Cynognathus'' and the herbivorous traversodontids. Cynognathians can be identified by several ...

was named after the genus, within the Eucynodontia.

Paleobiology

The

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

was equipped with differentiated teeth that show this animal could effectively process its food before swallowing. The presence of a

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medi ...

in the mouth indicates that ''Cynognathus'' would have been able to breathe and swallow simultaneously. The possible lack of belly ribs, in the stomach region, suggests the presence of an efficient

diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

: an important muscle for mammalian breathing. Pits and canals on the bone of the snout indicate concentrations of

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the ...

s and blood vessels. In mammals, such structures allow hairs (

whiskers Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarse ...

) to be used as sensory organs.

Description

Discovery and naming

Distribution

Classification

Paleobiology

See also

References

Further reading