Temporal range: Late Triassic (Carnian), 233.23–0 Ma
PreꞒ
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
Skull of Kayentatherium wellesi
Gaur
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Synapsida
Clade:
Therapsida
Clade:
Cynodontia
Clade:
Probainognathia
Clade:
Prozostrodontia Liu and Olsen, 2010
Subgroups
†Agudotherium?
†Alemoatherium
†Santacruzgnathus[1]
†Therioherpeton
†Prozostrodontidae[2]
†Prozostrodon
†Pseudotherium
†Dromatheriidae
†Tritheledontidae
Mammaliamorpha
Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade containing Prozostrodon brasiliensis, Tritylodon langaevus, Pachygenelus monus, and Mus musculus (the house mouse). Prozostrodontia is diagnosed by several characters, including:
Reduced prefrontal and postorbital bones, with the disappearance of a strut of bone called the postorbital bar separating the eye socket from the temporal region
Unfused symphysis between the dentary bones in the lower jaw
The presence of a small hole within the eye socket called the sphenopalatine foramen
A long sagittal crest extending to the rearmost part of the lambdoidal crest at the back of the skull
Neural spines of the dorsal vertebrae angled backward
A convex-shaped iliac crest and a reduced posterior iliac spine on the hip
An acetabular notch on the ischium (a groove in the hip socket)
The position of a small projection called the lesser trochanter close to the head of the femur[3]
Prozostrodontia includes tritylodontids, which have traditionally been placed within the more primitive cynodont group Cynognathia as distant mammal relatives. It also includes Tritheledontidae, which has long been placed close to mammals. Most previous studies considered Tritheledontidae a valid monophyletic grouping, meaning it was a true clade including all the descendants of a single common ancestor, but Liu and Olsen (2010) found Tritheledontidae to be a paraphyletic series of basal prozostrodontians. Below is a cladogram from Liu and Olsen (2010) showing the phylogenetic position of Prozostrodontia:[3]
Cynodontia
Procynosuchus
Galesaurus
Thrinaxodon
Platycraniellus
Eucynodontia
Cynognathia
Cynognathus
Gomphodontia
Diademodon
Langbergia
Trirachodon
Sinognathus
Traversodontidae
Pascualgnathus
Luangwa
Scalenodon angustifrons
Scalenodon hirschoni
Massetognathus
Exaeretodon
Probainognathia
Ecteninion
Chiniquodon
Probainognathus
Prozostrodontia
Prozostrodon
Therioherpeton
Riograndia
Pachygenelus
Tritylodontidae
Oligokyphus
Kayentatherium
Tritylodon
Bienotherium
Brasilodon
Mammalia
Adelobasileus
Sinoconodon
Morganucodon
^Martinelli, A. G.; Eltink, E.; Da-Rosa, Á. A. S.; Langer, M. C. (2017). "A new cynodont from the Santa Maria formation, south Brazil, improves Late Triassic probainognathian diversity". Papers in Palaeontology. 3 (3): 401–423. Bibcode:2017PPal....3..401M. doi:10.1002/spp2.1081.
^Stefanello, M.; Martinelli, A. G.; Müller, R. T.; Dias-da-Silva, S.; Kerber, L. (2023). "A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts". Journal of Mammalian Evolution. 30 (2): 299–317. doi:10.1007/s10914-022-09648-y.
^ abLiu, J.; Olsen, P. (2010). "The Phylogenetic Relationships of Eucynodontia (Amniota: Synapsida)". Journal of Mammalian Evolution. 17 (3): 151. doi:10.1007/s10914-010-9136-8.
Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected...
Zone of Brazil. Probainognathids were closely related to the clade Prozostrodontia, which includes mammals and their close relatives. Members of Probainognathidae...
the head of the femur is one of the defining characteristics of the Prozostrodontia, which is the clade of cynodonts including mammals and their closest...
symphysis is one of the main synapomorphies (shared derived features) of Prozostrodontia. At the rear end of the dentary, behind the tooth row, a somewhat tall...
for facial nerves connected whiskers in extant mammals indicate the Prozostrodontia, small immediate ancestors of mammals, presented whiskers similar to...
the two genera forming the clade Prozostrodontidae at the base of Prozostrodontia. A cladogram from that study is shown below: Wallace, Rachel V. S.;...
double-rooted teeth, indicate that the animal was an early member of Prozostrodontia, a group that includes mammals and their close relatives. The holotype...
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