Temporal range: Early - Middle Triassic, 251–237 Ma
PreꞒ
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
Life restoration of Trirachodon berryi in a burrow
Skull of Langbergia in dorsal view
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Synapsida
Clade:
Therapsida
Clade:
Cynodontia
Clade:
†Neogomphodontia
Family:
†Trirachodontidae Crompton, 1955
Genera
†Beishanodon
†Cricodon
†Guttigomphus
†Impidens
†Langbergia
†Sinognathus
†Trirachodon
Trirachodontidae is an extinct, possibly paraphyletic[1] family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids appeared during the Early Triassic soon after the Permian-Triassic extinction event and quickly spread over a wide geographic area in a comparatively brief amount of time from 250 to 237 million years ago.
Trirachodontids have wide skulls and short, narrow snouts. Two large holes called temporal fenestrae run along the back of the head and have a uniformly large width. Trirachodontids also have two large canine teeth and smaller cusped postcanines. Most of the features that distinguish trirachodonts from other cynodonts are found in their dentition.[2]
Trirachodontids lived in semi-arid environments with seasonal rainfall. The bone structure of trirachodontids suggests that they grew quickly in seasons with high rainfall and slowly in less favorable seasons.[3] One trirachodontid, Trirachodon, has been found in association with complex burrow systems. These burrows were probably used by many individuals to hide from predators, raise young, or stay warm.
Two subfamilies of trirachodontids are recognized: Trirachodontinae from Africa and Sinognathinae from China. Below is a cladogram from Gao et al. (2010) showing the phylogenetic relationships of trirachodontids:[2]
Cynognathia
Cynognathus
Gomphodontia
Diademodon
Trirachodontidae
Trirachodontinae
Trirachodon
Langbergia
Cricodon
Sinognathinae
Beishanodon
Sinognathus
Traversodontidae
The cladogram above shows a monophyletic Trirachodontidae, but multiple studies have found the family to be paraphyletic with respect to the family Traversodontidae.[1][4] Below is a cladogram from Hendrickx et al. (2020), who also recovered the members of the subfamily Trirachodontinae as a basal polytomy within the clade Neogomphodontia:[1]
Cynognathia
Cynognathus
Gomphodontia
Diademodontidae
Diademodon
Titanogomphodon
Neogomphodontia
Langbergia
Trirachodon
Sinognathinae
Beishanodon
Cricodon
Sinognathus
Traversodontidae
Trirachodontidae
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Trirachodontidae is an extinct, possibly paraphyletic family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids...
cynognathian cynodonts that includes the families Diademodontidae, Trirachodontidae, and Traversodontidae. Gomphodonts are distinguished by wide and closely...
Most phylogenetic analyses place it as the sister taxon to the family Trirachodontidae, and both groups are placed in the cynognathian clade Gomphodontia...
group, which traditionally included the families Diademodontidae, Trirachodontidae, Traversodontidae, and Tritylodontidae. More recently, tritylodontids...
Zambia: patterns of tooth replacement and a systematic review of the Trirachodontidae". Journal of Vertebrate Paleontology. 37 (sup1): 39–64. Bibcode:2017JVPal...
Zambia: patterns of tooth replacement and a systematic review of the Trirachodontidae". Journal of Vertebrate Paleontology. 37 (sup1): 39–64. Bibcode:2017JVPal...
also study the phylogenetic relationships of members of the family Trirachodontidae. A study on the musculature, posture and range of motion of the forelimb...
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