''Cynognathus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of large-bodied

cynodontia Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ances ...

n therapsids that lived in the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

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

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

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 preserve ...

s have so far been recovered from

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

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

, and

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

Description

''Cynognathus'' was a heavily built animal, and measured around in snout-to-vent body length and up to in total 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. There has been controversy about whether the forelimbs were also held upright or sprawled outwards in a reptilian fashion, but recent studies suggest

cynodonts Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ances ...

typically held their front legs in a posture between these two extremes. A study of living mammals concluded that "upright posture" in mammals is a myth based on the posture of mammal species specialized for fast running, such as dogs, hares, and antelopes; modern mammals that are not specialized for running often hold their forelimbs in a semi-sprawled posture. 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 ...

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 fa ...

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 water ...

, 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 International_Code_of_Zoological_Nomenclature, 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 spe ...

''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

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''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 ''Cynidiognathus'', ''Cynogomphius'', ''Karoomys'', ''Lycaenognathus'', ''Lycochampsa'' and ''Lycognathus''. Opinions vary as to whether all remains belong to the same species. The genus ''Karoomys'' is known only from a tiny juvenile. Species-level synonyms of ''Cynognathus crateronotus'' include ''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 Khoemana (also known as !Orakobab or Korana) word is a semidesert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its extent is ...

, the Puesto Viejo Formation,

Fremouw Formation The Fremouw Formation is a Triassic-age rock formation in the Transantarctic Mountains of the Ross Depenency of Antarctica. It contains the oldest known fossils of tetrapods from Antarctica, including synapsids, reptiles and amphibians. Fossiliz ...

, in

Lesotho Lesotho, formally the Kingdom of Lesotho and formerly known as Basutoland, is a landlocked country in Southern Africa. Entirely surrounded by South Africa, it is the largest of only three sovereign enclave and exclave, enclaves in the world, t ...

and

. ''Cynognathus'' lived between the

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

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 The ''Cynognathus'' Assemblage Zone is a tetrapod biozone utilized in the Karoo Basin of South Africa. It is equivalent to the Burgersdorp Formation, the youngest Lithostratigraphy, lithostratigraphic Geological formation, formation in the Beauf ...

'' 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 per ...

Classification

Seeley in 1894/1895 placed ''Cynognathus'' in a separate family Cynognathidae, within the

Cynodontia Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ances ...

. ''Cynognathus'' is presently the only recognized member of the family Cynognathidae. Later a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

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 or omnivorous gomphodonts such as traversodontids. Cynogn ...

was named after the genus, within the

Eucynodontia Eucynodontia ("true dog teeth") is a clade of cynodont therapsids including mammals and most non-mammalian cynodonts. The oldest eucynodonts are known from the Early Triassic and possibly Late Permian. Eucynodontia includes two major subgroups, ...

. ''Cynognathus crateronotus'' in a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

after Stefanello ''et al''. (2023):

Paleobiology

In the Karoo Basin in what is now South Africa, ''Cynognathus'' lived in open environments with warm, dry summers and cool, wet winters, similar to today's Western Cape region but more arid. Individuals grew rapidly and continuously. Their hunting habits were largely unaffected by the changing seasons. The

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

was equipped with differentiated teeth, with fangs in the front for seizing prey and wider teeth in the rear of the jaw suitable for cutting meat; these 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 med ...

in the mouth indicates that ''Cynognathus'' would have been able to breathe and swallow simultaneously. All these adaptations are consistent with maintaining a regular, high basal metabolic rate ("

warm-blooded Warm-blooded is a term referring to animal species whose bodies maintain a temperature higher than that of their environment. In particular, homeothermic species (including birds and mammals) maintain a stable body temperature by regulating ...

"), as in modern mammals. 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 that allows mammals to breathe equally well when they are walking, running, or holding still. 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). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

s and blood vessels. In mammals, these structures support special sensory hairs (

whiskers Whiskers, also known as vibrissae (; vibrissa; ) are a type of stiff, functional hair used by most therian mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser as ta ...

), so it is likely ''Cynognathus'' had whiskers as well.

Description

Discovery and naming

Distribution

Classification

Paleobiology

See also

References

Further reading