Oligokyphus
Oligokyphus Temporal range:
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Life restoration of O. triserialis | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Synapsida |
Clade: | Therapsida |
Clade: | Cynodontia |
Family: | †Tritylodontidae |
Genus: | †Oligokyphus Hennig, 1922 |
Type species | |
Oligokyphus triserialis Hennig E, 1922
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Species | |
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Synonyms | |
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Oligokyphus ("few cusps") is an extinct genus of herbivorous tritylodontid cynodont known from the Late Triassic to Early Jurassic of Europe, Asia and North America.
Discovery and naming
Oligokyphus was named by Edwin Hennig in 1922 on the basis of two teeth from Württemberg, Germany. The name of the genus is derived from Greek ὀλιγος "few" and κυφος "hump", and is a calque of Paucituberculata, the group in which Oligokyphus was initially classified, from Latin into Greek.[1] Like Tritylodon, Oligokyphus was originally classified as a mammal. Hennig initially recognized two species, which he named Oligokyphus triserialis and Oligokyphus biserialis based on the number of rows of cusps, though he acknowledged this distinction as provisional.[2]
The next discoveries of Oligokyphus were made in the United Kingdom. The German paleontologist Walter Georg Kühne traveled to the United Kingdom in 1938 with the goal of collecting early mammal specimens. The outbreak of World War II led to Kühne's internment on the Isle of Man, during which time he prepared and studied the collected material.[3] Kühne initially identified the specimens as Tritylodon. His discovery that the specimens lacked the dentary-squamosal jaw joint, at the time viewed as the defining characteristic of mammals, led him to conclude that tritylodontids were "mammal-like reptiles", though he recognized that they were close to the origin of mammals.[4] Kühne's detailed description of the material was published in 1956, and made Oligokyphus the best-known tritylodontid. Kühne regarded two different size classes of adult as being present. Though he acknowledged the differences could be due to sexual dimorphism, he proposed that they represented two distinct species, which he named Oligokyphus major and Oligokyphus minor.[5] In 1985, the genus was reported from the Early Jurassic Kayenta Formation in the United States.[6] In 1994, the species O. lufengensis was described from the Lower Jurassic Lufeng Formation of China.[7] In 2015, indeterminate remains of the genus were described from the McCoy Brook Formation of eastern Canada, dating to the latest Triassic (Rhaetian).[8]
Description
Oligokyphus were relatively small tritylodontids, with a skull up to 90 mm long and an estimated body mass of 3.4 kg.[9] There may have been some sexual dimorphism in size.[10]
Skull and jaw
The teeth of the upper and lower jaw contain bump rows that fit together perfectly in order to maintain an accurate bite. Oligokyphus had a face similar to that of modern mammals, although there were differences in the cheekbones and eye sockets. It had a bony secondary
The teeth were different from those of related cynodonts; there were no canine teeth, and unusually large, rodent-like
While the postcanines in non-mammalians, such as Oligokyphus, are difficult to differentiate from canines, the lower postcanines of Oligokyphus (also considered to be pre-molars) are defining from other Tritylodonts. On lower postcanine teeth of Trityldonts, two cusps can be found per row; however, Oligokyphus have two rows with three cusps in each row.[11] These cusps, specific to Oligokyphus Tritylodonts, allowed for a well-fitting bite that was particularly good at shredding plant material dense in fiber. The foremost incisors are similar to those of today's rodents, extremely intensified and enlarged. The typical location of canine teeth is left empty with Oligokyphus. Instead, a gap is inserted in this area of the jaw as Oligokyphus lack the teeth commonly known as canines.[12]
Cladistics/phylogeny
Oligokyphus is in the family Tritylodontidae. The family is named after the shape of their teeth. Tritylodontidae means "three knob teeth". The members of this family were all small to medium-sized advanced synapsids with combined specialized structures for herbivorous eating. The first Tritylodont was found in South Africa in upper Jurassic rocks. It was first thought to be one of the earliest mammals. This classification has since been adjusted. These non-mammals became progressively more mammal-like. They are now classified as the closest relatives to the mammals and this is supported by their high, flat, crested jaw, large zygomatic arches, well developed secondary palate, and specialized dentition.
There have also been comparisons between the
Paleoecology
Habitat
Oligokyphus were small tetrapod, terrestrial animals. They have long been considered as mammaliomorphs, a link between earlier
A definitive radiometric dating of the area preserved in the formation where Oligokyphus lived has not yet been made, and the available stratigraphic correlation has been based on a combination of radiometric dates from vertebrate fossils, magnetostratigraphy and pollen evidence.[13] It has been surmised that the Kayenta Formation was deposited during the Sinemurian and Pliensbachian stages of the Early Jurassic Period or approximately 199 to 182 million years ago.[14] This formation is part of the Glen Canyon Group that includes formations not only in northern Arizona but also parts of southeastern Utah, western Colorado, and northwestern New Mexico. The formation was primarily deposited by rivers. During the Early Jurassic period, the land that is now the Kayenta Formation experienced rainy summers and dry winters. By the Middle Jurassic period it was being encroached upon from the north by a sandy dune field that would become the Navajo Sandstone.[15] The animals here were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes.
Paleofauna
North America
Oligokyphus lived beneath the feet of dinosaurs, such as the theropods
References
- ^ Hennig 1922, p. 215.
- ^ Hennig 1922, p. 231.
- ^ Savage 1993, p. 1028.
- ^ Kühne 1943.
- ^ Kühne 1956, p. 98.
- ISSN 0272-4634.
- ISSN 0272-4634.
- ISSN 0008-4077.
- ^ Gaetano, Abdala & Govender 2017, pp. 2, 4.
- ^ Kühne 1956, pp. 97–98.
- ^ Trevor Dykes. "JURASSIC CYNODONTS; Tritylodontidae, an internet directory". Archived from the original on 2010-04-23. Retrieved 8 June 2012.
- ^ ISBN 0-486-40568-0
- ^ J. M. Clark and D. E. Fastovsky. 1986. Vertebrate biostratigraphy of the Glen Canyon Group in northern Arizona. The Beginning of the Age of the Dinosaurs: Faunal change across the Triassic-Jurassic boundary, N. C. Fraser and H.-D. Sues (eds.), Cambridge University Press 285–301
- ^ Padian, K (1997) Glen Canyon Group In: Encyclopedia of Dinosaurs, edited by Currie, P. J., and Padian, K., Academic Press.
- ^ S2CID 32010827.
- ^ Gay, R. 2010. Kayentavenator elysiae, a new tetanuran from the early Jurassic of Arizona. Pages 27–43 in Gay, R. Notes on early Mesozoic theropods. Lulu Press (on-demand online press).
- PMID 20926438.
- ^ Tykoski, R. S., 1998, The Osteology of Syntarsus kayentakatae and its Implications for Ceratosaurid Phylogeny: Theses, The University of Texas, December 1998.
- ^ S2CID 35607107.
- ^ a b Lucas, S. G.; Heckert, A. B.; Tanner, L. H. (2005). "Arizona's Jurassic fossil vertebrates and the age of the Glen Canyon Group". In Heckert, A. B.; Lucas, S. G. (eds.). Vertebrate paleontology in Arizona. Bulletin. Vol. 29. Albuquerque, NM: New Mexico Museum of Natural History and Science. pp. 95–104.
- ^ .
- ^ Curtis, K.; Padian, K. (1999). "An Early Jurassic microvertebrate fauna from the Kayenta Formation of northeastern Arizona: microfaunal change across the Triassic-Jurassic boundary". PaleoBios. 19 (2): 19–37.
- ^ a b Luttrell, P. R., and Morales, M. 1993. Bridging the gap across Moenkopi Wash: a lithostratigraphic correlation. Aspects of Mesozoic geology and paleontology of the Colorado Plateau. Pages 111–127 in Morales, M., editor. Museum of Northern Arizona, Flagstaff, AZ. Bulletin 59.
- ^ Hamblin, A. H., and Foster, J. R. 2000. Ancient animal footprints and traces in the Grand Staircase-Escalante National Monument, south-central Utah. Pages 557–568 in Sprinkel, D. A., Chidsey, T. C. Jr., and Anderson, P. B. editors. Geology of Utah's parks and monuments. Utah Geological Association, Salt Lake City, UT. Publication 28.
- .
Works cited
- Abdala, Fernando; Maria Claudia Malabarba (30 August 2007). "Enamel microstructure in Exaeretodon, a Late Triassic South American traversodontid (Therapsida: Cynodontia)". Revista Brasileira de Paleontologia. 10 (2): 71–78. .
- Gaetano, Leandro C.; Abdala, Fernando; Govender, Romala (2017-02-16). "The postcranial skeleton of the Lower Jurassic Tritylodon longaevus from southern Africa". Ameghiniana. 54 (1): 1–35. S2CID 131866292.
- Johnson R. Haas. "the late Paleozoic land faunas" (PDF). GEOS 2000 Evolution of Life. Western Michigan University. Archived from the original (PDF) on 18 February 2012. Retrieved 8 June 2012.
- Hennig, Edwin (1922-07-18). "Die Säugerzähne des württembergischen Rhät–Lias-Bonebeds" [The mammal teeth of the Rhaeto-Liassic bonebeds of Württemberg]. Neues Jahrbuch für Geologie und Paläontologie. Beilage-Band 46 (2): 181–267.
- Kühne, W. G. (1943-09-01). "The dentary of Tritylodon and the systematic position of the Tritylodontidae". Annals and Magazine of Natural History. 10 (69): 589–601. ISSN 0374-5481.
- Kühne, Walter Georg (1956-11-09). The Liassic therapsid Oligokyphus. .
- Savage, Robert J. G. (1993). "Vertebrate fissure faunas with special reference to Bristol Channel Mesozoic faunas". Journal of the Geological Society. 150 (6): 1025–1034. S2CID 131591906.
- Hans-Dieter Sues (1986). "Dinnebitodon Amarall, a New Tritylodontid (Synapsida) from the lower Jurassic of Western North America". Journal of Paleontology. 60 (1986): 758–762. S2CID 131801988.
External links
- Paleontology portal
- M. Alan Kazlev. "Tritylodontidae-Oligokyphus". Kheper – transformation – evolution – metamorphosis. Retrieved 8 June 2012.
- Michael R. Long. "Oligokyphus". Picture library. Natural History Museum (London). 001460. Archived from the original on 3 March 2016. Retrieved 8 June 2012.
- "Specimen account. Catalog Number: V83672". Berkeley Natural History Museums. Archived from the original on 12 December 2012. Retrieved 8 June 2012.