Scalenodon

Last updated

Scalenodon
Temporal range: Middle Triassic
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Family: Traversodontidae
Genus: Scalenodon
Crompton, 1955
Species
  • S. angustifrons(Parrington, 1955 [originally Trirachodon angustifrons]) (type)
  • S. boreusTatarinov, 1973
  • S. ribeiroaeMelo, Martinelli & Soares, 2017
  • ?S. attridgeiCrompton, 1972
  • ?S. charigiCrompton, 1972

Scalenodon is an extinct genus of traversodontid cynodonts from the Middle Triassic of Africa and possibly Russia. The type species S. angustifrons was named in 1946 and several other species were named in the following years. Most of the species from Africa are now thought to belong to different genera than Scalenodon.

History and species

The first fossils belonging to Scalenodon were found in the Manda Formation of Zambia and assigned to Trirachodon angustifrons in 1946. [1] In 1955, the species was given its own genus, Scalenodon. [2] In 1963, a second species called S. drysdalli was named from the Ntawere Formation in the Luangwa Valley of Zambia. Later that year S. drysdalli was placed in its own genus, Luangwa . [3] Three additional species, S. attridgei, S. charigi, and S. hirschoni, were named from the Manda Formation in 1972. In 1973, a Russian species of Scalenodon was named S. boreus. S. boreus is known from the southern Ural Mountains of Orenburg Oblast. [4]

A 2003 analysis of traversodontid relationships did not find the species of Scalenodon from the Manda Formation to form a single clade, meaning that many were not referable to the genus. The study suggested that S. hirschoni had more in common with other traversodontids like Luangwa . S. attridgei was viewed as a possible synonym of S. charigi, which was also found to be only distantly related to S. angustifrons. [5] S. hirschsoni was placed in its own genus, Mandagomphodon , in 2013. [6]

S. angustifrons and S. boreus remain valid species of Scalenodon. While S. angustifrons is known from partial skulls, teeth, and a lower jaw, S. boreus is known only from two upper postcanine teeth.

Related Research Articles

<i>Abrictosaurus</i> Extinct genus of dinosaur from the early Jurassic of southern Africa

Abrictosaurus is a genus of heterodontosaurid dinosaur that lived during the Early Jurassic in what is now in parts of southern Africa such as Lesotho and South Africa. It was a bipedal herbivore or omnivore and was one of the most basal heterodontosaurids. It was approximately 1.2 metres (3.9 ft) long and weighed between 0.68 and 3 kilograms.

<span class="mw-page-title-main">Cynognathia</span> Clade of cynodonts

Cynognathia 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 synapomorphies including a very deep zygomatic arch that extends above the middle of the orbit.

<span class="mw-page-title-main">Traversodontidae</span> Extinct family of cynodonts

Traversodontidae is an extinct family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and eastern North America. Traversodonts first appeared in the Middle Triassic and diversified in the Late Triassic before going extinct at the end of the epoch. The family Traversodontidae was erected by Friedrich von Huene in 1936 for cynodonts first found in São Pedro do Sul in Paleorrota, Brazil.

<i>Cherninia</i> Extinct genus of amphibians

Cherninia is an extinct genus of mastodonsaurid temnospondyl. The type species, Cherninia denwai, is known from the Denwa Formation of India. It is based on a massive skull, ISI A 54, which was originally considered a species of Parotosuchus in 1998 before being given its own genus in 2001.

<i>Luangwa</i> (cynodont) Extinct genus of cynodonts

Luangwa is an extinct genus of traversodontid cynodonts. The species Luangwa drysdalli was discovered 1963 in the valley of the Luangwa river in Zambia, Africa. Luangwa lived in the Triassic period 240 Million years ago.

Sangusaurus is an extinct genus of large dicynodont synapsid with two recognized species: S. edentatus and S. parringtonii. Sangusaurus is named after the Sangu stream in eastern Zambia near to where it was first discovered + ‘saur’ which is the Greek root for lizard. Sangusaurus fossils have been recovered from the upper parts of the Ntawere Formation in Zambia and of the Lifua Member of the Manda Beds in Tanzania. The earliest study considered Sangusaurus a kannemeyeriid dicynodont, but more recent phylogenetic analyses place Sangusaurus within the stahleckeriid clade of Dicynodontia. Until recently, little work had been done to describe Sangusaurus, likely due to the fact that only four incomplete fossil specimens have been discovered.

Rechnisaurus is an extinct genus of dicynodont from the Middle Triassic (Anisian) Yerrapalli Formation of India. It contains a single species, Rechnisaurus cristarhynchus.

<i>Trirachodon</i> Extinct genus of cynodonts

Trirachodon is an extinct genus of cynodonts. Fossils have been found in the Cynognathus Assemblage Zone of the Beaufort Group in South Africa and the Omingonde Formation of Namibia, dating back to the Early and Middle Triassic.

Langbergia is an extinct genus of trirachodontid cynodont from the Early Triassic of South Africa. The type and only species L. modisei was named in 2006. Langbergia was found in the Burgersdorp Formation in the Beaufort Group, a part of the Cynognathus Assemblage Zone. The closely related trirachodontids Trirachodon and Cricodon were found in the same area.

Santacruzodon is an extinct genus of cynodonts which existed in Brazil during the Triassic period. The type species is Santacruzodon hopsoni.

Neotrirachodon is an extinct genus of therapsids which existed in Russia during the Middle Triassic period. Its type and only species is Neotrirachodon expectatus.

Variodens is an extinct genus of trilophosaur. Fossils have been found from the Emborough Quarries in the Mendip Hills of Somerset, England. These fossils have been uncovered from a Late Triassic fissure fill within Carboniferous-age limestone. The type and only known species is V. inopinatus, named in 1957.

<i>Andescynodon</i> Extinct genus of cynodonts

Andescynodon is a genus of traversodontid cynodonts from the Middle Triassic of Argentina. Fossils are known from the Cerro de las Cabras and Cacheutá Formations. Andescynodon is one of the most basal traversodontids. Another traversodontid called Rusconiodon has also been identified from the Cerro de las Cabras Formation but is now considered a junior synonym of Andescynodon.

Arctotraversodon is an extinct genus of traversodontid cynodonts from the Late Triassic of Canada. Fossils first described from the Wolfville Formation in Nova Scotia in 1984 represented the first known traversodontid from North America. The type and only species is A. plemmyridon and is represented by teeth and several dentary bones.

Boreogomphodon is an extinct genus of traversodontid cynodonts from the Late Triassic of the eastern United States. Fossils have been found from the Turkey Branch Formation in Virginia.

<span class="mw-page-title-main">Manda Formation</span>

The Manda Formation is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the earliest dinosauromorph archosaurs. The formation is often considered to be Anisian in age according to general tetrapod biochronology hypotheses and correlations to the Cynognathus Assemblage Zone of South Africa. However, some recent studies cast doubt to this age, suggesting that parts deposits may actually be younger (Carnian) in age.

Mandagomphodon is an extinct genus of traversodontid cynodonts from the Middle Triassic Lifua Member of the Manda Beds of Ruhuhu Valley, Tanzania. The type species Mandagomphodon hirschsoni was named by Crompton in 1972 as a species referable to Scalenodon. Later studies, including a 2003 phylogenetic analysis of traversodontid relationships, did not find the species of Scalenodon from the Manda Formation to form a single clade, meaning that many were not referable to the genus. The study suggested that S. hirschsoni had more in common with other traversodontids like Luangwa. S. attridgei was viewed as a possible synonym of S. charigi, which was also found to be only distantly related to S. angustifrons. Therefore, a new generic name Mandagomphodon was erected for S. hirschsoni by James A. Hopson in 2013.

<i>Cricodon</i> Extinct genus of cynodonts

Cricodon is an extinct genus of trirachodontid cynodonts that lived during the Early Triassic and Middle Triassic periods of Africa. A. W. Crompton named Cricodon based on the ring-like arrangement of the cuspules on the crown of a typical postcanine tooth. The epithet of the type species, C. metabolus, indicates the change in structure of certain postcanines resulting from replacement.

<i>Aleodon</i> Extinct genus of cynodonts

Aleodon is an extinct genus of cynodonts that lived from the Middle to the Late Triassic. Relatively few analyses have been conducted to identify the phylogenetic placement of Aleodon, however those that have place Aleodon as a sister taxon to Chiniquodon. Two species of Aleodon are recognized: A. brachyramphus which was discovered in Tanzania, and A. cromptoni which was discovered most recently in Brazil.

The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls.

References

  1. Parrington, F.R. (1946). "On the cranial anatomy of cynodonts". Proceedings of the Zoological Society of London. 116 (2): 181–197. doi:10.1111/j.1096-3642.1946.tb00116.x.
  2. Crompton, A.W. (1955). "On some Triassic cynodonts from Tanganyika". Proceedings of the Zoological Society of London. 125 (3–4): 617–669. doi:10.1111/j.1096-3642.1955.tb00620.x.
  3. Brink, A.S. (1963). "Two cynodonts from the Ntawere Formation in the Luangwa valley of Northern Rhodesia". Palaeontologia Africana. 8: 77–96.
  4. Tatarinov, L.P. (1973). "Cynodonts of Gondwanan habit in the Middle Triassic of the USSR". Paleontological Journal. 2: 200–205.
  5. Abdala, F. & Ribeiro, A.M. (2003). "A new traversodontid cynodont from the Santa Maria Formation (Ladinian-Carnian) of southern Brazil, with a phylogenetic analysis of Gondwanan traversodontids". Zoological Journal of the Linnean Society. 139 (4): 529–545. doi: 10.1111/j.1096-3642.2003.00096.x .
  6. James A. Hopson (2013). "The traversodontid cynodont Mandagomphodon hirschsoni from the Middle Triassic of the Ruhuhu Valley, Tanzania". In Christian F. Kammerer; Kenneth D. Angielczyk; Jörg Fröbisch (eds.). Early Evolutionary History of the Synapsida. Vol. in press. Springer. ISBN   978-94-007-6840-6.