Lumkuia

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Lumkuia
Temporal range: Anisian, 247.2–242.0  Ma
Lumkuia.jpg
Life restoration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Probainognathia
Family: Lumkuiidae
Hopson and Kitching, 2001
Genus: Lumkuia
Hopson and Kitching, 2001
Species:
L. fuzzi
Binomial name
Lumkuia fuzzi
Hopson and Kitching, 2001

Lumkuia is an extinct genus of cynodonts, fossils of which have been found in the Cynognathus Assemblage Zone of the Beaufort Group in the South African Karoo Basin that date back to the early Middle Triassic. It contains a single species, Lumkuia fuzzi, which was named in 2001 on the basis of the holotype specimen BP/1/2669, which can now be found at the Bernard Price Institute in Johannesburg, South Africa. The genus has been placed in its own family, Lumkuiidae. Lumkuia is not as common as other cynodonts from the same locality such as Diademodon and Trirachodon . [1]

Contents

Discovery and naming

The holotype and only known specimen of Lumkuia, BP/1/2669, was found by Paul Reubsamen near the Lumku Mission in the Eastern Cape province, close to the small town of Lady Frere. It was collected from rocks belonging to the subzone B of the Cynognathus Assemblage Zone. It consists of a well-preserved skull, part of the shoulder girdle (including the left scapulocoracoid, the left and a partial right clavicle, and the interclavicle), 10 dorsal vertebrae with ribs, 8 caudal (tail) vertebrae, and a nearly complete left forelimb. The specimen was stored in the fossil collection of the Bernard Price Institute of Johannesburg, where it was originally listed as a juvenile of Trirachodon , a basal member of Gomphodontia. However, in 1988 the American palaeontologist James A. Hopson noted several traits that it shared with Probainognathus and the chiniquodontids, members of a more mammal-like clade of cynodonts that would later be named Probainognathia. [2]

In 2001 Hopson, joined by James W. Kitching, formally described the specimen as the new taxon Lumkuia fuzzi. The generic name comes from the Lumku Mission, near which the holotype was found. The specific name honours the South African palaeontologist Alfred W. "Fuzz" Crompton. Hopson and Kitching gave the skull a detailed description, but the postcranial elements were described only in superficial terms. In 2022 the specimen, including the postcranium, was given a more comprehensive redescription by Julien Benoit and colleagues, based on data gained from synchrotron X-ray computed tomography. [2]

Description

The postcanines are similar to those of the later chiniquodontids, but the secondary palate is quite short in comparison, and the genus lacks the angulation of the ventral cranial margin seen in chiniquodontids. [2] Lumkuia can be seen as more derived than other contemporary cynodonts such as Cynognathus with the crowns of its teeth high and narrow and having inwardly curving tops.

Classification

Eucynodontia
Probainognathia

Lumkuia

Ecteninion

Probelesodon

Chiniquodon

Aleodon

Probainognathus

Pachygenelus

Morganucodon

Cynognathia

Cladogram after Hopson & Kitching (2001) [2]

Lumkuia was first described in 2001 by the palaeontologists Hopson and Kitching, who considered it to be the most basal member of Probainognathia; [2] this placement has been supported by several later studies. [3] [4] [5] A 2010 phylogenetic analysis by Liu and Olsen, and multiple later analyses based on the same data matrix, have instead placed it outside the clade formed by Cynognathia and Probainognathia. [3] However, during a 2022 redescription of Lumkuia, new anatomical characters found during the study were incorporated into the Liu & Olsen (2010) matrix, which led to Lumkuia being unambiguously recovered as a basal probainognathian. [3] Before the discovery of Lumkuia, the earliest known probainognathians were from younger strata in Africa and South America that were deposited in the late Middle and Late Triassic. [6] [7] [8] [9] [10] [11] [12]

Related Research Articles

<span class="mw-page-title-main">Therapsid</span> Clade of tetrapods including mammals

A therapsid is a member of the clade Therapsida which is a major group of eupelycosaurian synapsids that includes mammals and 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 underneath the body, as opposed to the sprawling posture of many reptiles and salamanders.

<span class="mw-page-title-main">Cynodont</span> Clade of therapsids

Cynodonts are eutheriodont therapsids that first appeared in the Late Permian, and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ancestors and close relatives (Mammaliaformes), having evolved from advanced probainognathian cynodonts during the Late Triassic.

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

Eucynodontia 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, Cynognathia and Probainognathia.

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

Probainognathidae is an extinct family of insectivorous cynodonts which lived in what is now South America during the Middle to Late Triassic. The family was established by Alfred Romer in 1973 and includes two genera, Probainognathus from the Chañares Formation of Argentina and Bonacynodon from the Dinodontosaurus Assemblage Zone of Brazil. Probainognathids were closely related to the clade Prozostrodontia, which includes mammals and their close relatives.

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

Probainognathus meaning “progressive jaw” is an extinct genus of cynodonts that lived around 235 to 221.5 million years ago, during the Late Triassic in what is now Argentina. Together with the genus Bonacynodon from Brazil, Probainognathus forms the family Probainognathidae. Probainognathus was a relatively small, carnivorous or insectivorous cynodont. Like all cynodonts, it was a relative of mammals, and it possessed several mammal-like features. Like some other cynodonts, Probainognathus had a double jaw joint, which not only included the quadrate and articular bones like in more basal synapsids, but also the squamosal and surangular bones. A joint between the dentary and squamosal bones, as seen in modern mammals, was however absent in Probainognathus.

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

Ecteninion is an extinct genus of meat-eating cynodonts that lived during the Late Triassic (Carnian) in South America. The type species Ecteninion lunensis was named by R.N. Martinez, C.L. May, and C.A. Forster in 1996. E. lunensis is known from a nearly complete skull of about 11 centimetres (4.3 in) in length. It was found in the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina. It has been interpreted as a basal eucynodont. The holotype is in the collection of the Universidad Nacional de San Juan.

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

Chiniquodon is an extinct genus of carnivorous cynodonts, which lived during the Late Triassic (Carnian) in South America and Africa. Chiniquodon was closely related to the genus Aleodon, and close to the ancestry of mammals.

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

Massetognathus is an extinct genus of plant-eating traversodontid cynodonts. They lived during the Triassic Period about 235 million years ago, and are known from the Chañares Formation in Argentina and the Santa Maria Formation in Brazil.

<i>Cynognathus</i> Assemblage Zone Biozone which correlates to the Burgersdorp Formation of the Beaufort Group

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 lithostratigraphic formation in the Beaufort Group, which is part of the fossiliferous and geologically important Karoo Supergroup. The Cynognathus Assemblage Zone is the youngest of the eight biozones found in the Beaufort Group, and is considered to be late Early Triassic (Olenekian) to early Middle Triassic (Anisian) in age. The name of the biozone refers to Cynognathus crateronotus, a large and carnivorous cynodont therapsid which occurs throughout the entire biozone.

<i>Chanaresuchus</i> Extinct genus of reptiles

Chanaresuchus is an extinct genus of proterochampsid archosauriform. It was of modest size for a proterochampsian, being on average just over a meter in length. The type species is Chanaresuchus bonapartei was named in 1971. Its fossils were found in from the early Carnian-age Chañares Formation in La Rioja Province, Argentina. Chanaresuchus appears to be one of the most common archosauriforms from the Chañares Formation due to the abundance of specimens referred to the genus. Much of the material has been found by the La Plata-Harvard expedition of 1964-65. Chanaresuchus is the most well-described proterochampsid in the subfamily Rhadinosuchinae.

The Chañares Formation is a Carnian-age geologic formation of the Ischigualasto-Villa Unión Basin, located in La Rioja Province, Argentina. It is characterized by drab-colored fine-grained volcaniclastic claystones, siltstones, and sandstones which were deposited in a fluvial to lacustrine environment. The formation is most prominently exposed within Talampaya National Park, a UNESCO World Heritage Site within La Rioja Province.

Cromptodon is an extinct genus of cynodonts from the Triassic of Cerro Bayo de Portrerillos, Cerro de las Cabras Formation, Argentina, South America. It is known only from PVL 3858, a mandible.

<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.

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

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 after the farm where the holotype was found, Langberg 566. 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.

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

Gomphodontia is a clade of cynognathian cynodonts that includes the families Diademodontidae, Trirachodontidae, and Traversodontidae. Gomphodonts are distinguished by wide and closely spaced molar-like postcanine teeth, which are convergent with those of mammals. Other distinguishing characteristics of gomphodonts include deep zygomatic arches, upper postcanines with three or more cusps spanning their widths and lower postcanines with two cusps spanning their widths. They are thought to have been herbivorous or omnivorous. Gomphodonts first appeared in the Early Triassic and became extinct at the end of the Late Triassic. Fossils are known from southern Africa, Argentina and southern Brazil, eastern North America, Europe, China, and Antarctica.

Titanogomphodon is an extinct genus of diademodontid cynodonts from the Middle Triassic Omingonde Formation of Namibia. It is known from a single partial skull that was described in 1973 from the Omingonde Formation. The type and only species is Titanogomphodon crassus. At about 40 centimetres (16 in), the skull of Titanogomphodon was significantly larger than that of its closest relative, Diademodon. Its teeth are similar to those of another group of cynodonts called Traversodontidae, but the similarities are likely the result of convergent evolution. Aside from its larger size, Titanogomphodon differs from Diademodon in having a bony projection on the postorbital bar behind the eye socket.

<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.

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

Bonacynodon is an extinct genus of cynodonts that lived in what is now southern Brazil during the Triassic period. The genus is monotypic, containing only the type species Bonacynodon schultzi. B. schultzi is known from two specimens, consisting of two partial skulls and some badly preserved parts of the postcranium. Both specimens were recovered from the Pinheiros-Chiniquá Sequence, part of the Santa Maria Supersequence of the Paraná Basin. This sequence preserves a faunal association known as the Dinodontosaurus Assemblage Zone, which contains numerous other species of cynodonts, dicynodonts and reptiles. Bonacynodon was a small, likely insectivorous cynodont, whose length has been estimated at around 30 centimetres (12 in). It can be distinguished from other cynodonts by its large, serrated (saw-like) canine teeth. Together with the genus Probainognathus of Argentina, it made up the family Probainognathidae, one of the earliest-diverging lineages of the clade Probainognathia. It was a fairly close relative of mammals, the only group of cynodonts alive today.

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

Santacruzgnathus is an extinct genus of small cynodonts from the Late Triassic (Carnian) Santacruzodon Assemblage Zone of Brazil. It contains one species, S. abdalai. Santacruzgnathus is known from a single partial lower jaw with four postcanine teeth, only one of which is well-preserved. Some features of the specimen, including the slender shape of the jaw and the incipiently double-rooted teeth, indicate that the animal was an early member of Prozostrodontia, a group that includes mammals and their close relatives.

References

  1. Fernando Abdala, P. John Hancox and Johann Neveling (2005). Cynodonts from the Uppermost Burgersdorp Formation, South Africa, and Their Bearing on the Biostratigraphy and Correlation of the Triassic Cynognathus Assemblage Zone. Journal of Vertebrate Paleontology25(1):192-199.
  2. 1 2 3 4 5 Hopson, J. A. and Kitching, J. W. (2001). A probainognathian cynodont from South Africa and the phylogeny of non-mammalian cynodonts. Bulletin of the Museum of Comparative Zoology156(1):5-35
  3. 1 2 3 Benoit, J.; Nxumalo, M.; Norton, L. A.; Fernandez, V.; Gaetano, L. C.; Rubidge, B.; Abdala, F. (2022). "Synchrotron scanning sheds new light on Lumkuia fuzzi (Therapsida, Cynodontia) from the Middle Triassic of South Africa and its phylogenetic placement". Journal of African Earth Sciences: 104689. doi:10.1016/j.jafrearsci.2022.104689.
  4. Martínez, R. N.; Fernandez, E.; Alcober, O. A. (2013). "A new non-mammaliaform eucynodont from the Carnian-Norian Ischigualasto Formation, Northwestern Argentina". Revista Brasileira de Paleontologia. 16: 61–76. doi: 10.4072/rbp.2013.1.05 .
  5. Ruta, M.; Botha-Brink, J.; Mitchell, S. A.; Benton, M. J. (2013). "The radiation of cynodonts and the ground plan of mammalian morphological diversity". Proceedings of the Royal Society B: Biological Sciences. 280 (1769): 20131865. doi:10.1098/rspb.2013.1865. PMC   3768321 . PMID   23986112.
  6. Romer, A. S. (1969). The Chañares (Argentina) Triassic reptile fauna V. A new chiniquodontid cynodont, Probelesodon lewisi- cynodont ancestry. Breviora333:1–24.
  7. Romer, A. S. (1970). The Chañares (Argentina) Triassic reptile fauna VI. A chiniquodontid cynodont with an incipient squamosaldentary jaw articulation. Breviora344:1–18
  8. Martínez, R. N. and Forster, C. A. (1996). The skull of Probelesodon sanjuanensis, Sp. Nov., from the Late Triassic Ischigualasto Formation of Argentina. Journal of Vertebrate Paleontology16:285–91.
  9. Martínez, R. N., May, C. L. and Forster, C. A. (1996). A new carnivorous cynodont from the Ischigualasto Formation (Late Triassic, Argentina), with comments on eucynodont phylogeny. Journal of Vertebrate Paleontology16:271–84.
  10. Romer, A. S. (1969). The Brazilian Triassic cynodont reptiles Belesodon and Chiniquodon. Breviora332:1–16
  11. Hopson, J. A. (1995). Patterns of evolution in the manus and pes of non-mammalian therapsids. Journal of Vertebrate Paleontology15:615–39.
  12. Rubidge, B. S. and Sidor, C. A. (2001). Evolutionary patterns among Permo-Triassic theraspids. Annual Review of Ecology and Systematics32:449-480.