This article relies largely or entirely on a single source .(January 2021) |
Kalaallitkigun Temporal range: | |
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Jaw diagram in lingual (internal) view, preserved areas in blue | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Synapsida |
Clade: | Therapsida |
Clade: | Cynodontia |
Clade: | Mammaliaformes |
Order: | † Haramiyida |
Genus: | † Kalaallitkigun Sulej et al., 2020 |
Species: | †K. jenkinsi |
Binomial name | |
†Kalaallitkigun jenkinsi Sulej et al., 2020 | |
Kalaallitkigun is an extinct genus of haramiyidan mammaliaforms from the Late Triassic of Greenland. It contains a single species, Kalaallitkigun jenkinsi, which was described in 2020 from a partial dentary (lower jaw) found in the Fleming Fjord Formation. More specifically, it was found in the mid-late Norian (~215 Ma) Carlsberg Fjord beds of the Ørsted Dal Member. It is the oldest of several mammaliaform species discovered in the Late Triassic sediments of Greenland. It is also the oldest mammaliaform with double-rooted teeth, and its pattern of tooth cusps help to clarify the evolution of haramiyidan teeth relative to their morganucodont-like ancestors. [1]
The holotype and only known specimen consists of a partial dentary preserving two teeth: the first premolariform (pm1) and second molariform (m2). Empty alveoli (sockets) for three more premolariforms and two more molariforms are also present in the preserved portion of the jaw. This gives a total number of four premolariforms and three molariforms, similar to Haramiyavia . The front of the dentary is broken off, so the shape and number of incisor and canine teeth are unknown. The thinnest portions of the posterior dentary are also not preserved. [1]
The dentary was relatively large, with proportionally small teeth. The meckelian groove, a furrow on the lingual (internal) surface of the dentary, widens towards the rear and merges with the postdentary trough (the groove which hosts the postdentary bones). The postdentary trough slopes upwards and is divided from the overlying coronoid fossa via a strong ridge. Unlike Morganucodon and earlier cynodonts, there is no groove on the inner surface directly under the molariform teeth. The masseteric fossa (on the outer rear surface of the dentary) is voluminous but shifted back past the level of the last molariform. The preserved premolariform tooth is single-rooted and simple, with a larger cusp at the front and a much smaller one at the back. [1]
The molariform m2 is intermediate in structure between the triconodont pattern seen in taxa such as Morganucodon (with large triangular cusps in a single row) and the specialized two-row pattern found in the more derived euharamiyidans. Like haramiyidans, there are two parallel rows of cusps separated by a median furrow. The four labial (outer/cheek side) cusps are homologous to the four main cusps of morganucodonts (from front to back: b, a, c, and d), with cusp a being the largest and cusp c as the second-largest. They can also be homologized to cusps b1 to b4 of Haramiyavia. In contrast to other haramiyidans (but like morganucodonts), the labial cusps of Kalaallitkigun are significantly larger than the cusps on the lingual (inner/tongue) side of the tooth. Cusp a in particular is large enough that it restricts the median furrow and divides the space into two basins. [1]
In the lingual tooth row, there are four small cusps (e', g, g', and i'). These cusps are homologous to cusps a1 to a4 of Haramiyavia. Cusp g, though still small, is the largest cusp in the lingual row, lying inwards from cusps a and c. Two additional small cusps are present in the tooth: cusps e (at the front tip) and i (the rear tip). The holotype of Kalaallitkigun is the oldest mammaliaform fossil with two roots per tooth, a condition which occurs in all molariforms and the last premolariform in the fossil, according to the shape of tooth sockets. The splitting of the root probably helped to reduce stresses at the crown-root boundary of the tooth. [1]
Ferugliotherium is a genus of fossil mammals in the family Ferugliotheriidae from the Campanian and/or Maastrichtian period of Argentina. It contains a single species, Ferugliotherium windhauseni, which was first described in 1986. Although originally interpreted on the basis of a single brachydont (low-crowned) molar as a member of Multituberculata, an extinct group of small, rodent-like mammals, it was recognized as related to the hypsodont (high-crowned) Sudamericidae following the discovery of additional material in the early 1990s. After a jaw of the sudamericid Sudamerica was described in 1999, these animals were no longer considered to be multituberculates and a few fossils that were previously considered to be Ferugliotherium were assigned to unspecified multituberculates instead. Since 2005, a relationship between gondwanatheres and multituberculates has again received support. A closely related animal, Trapalcotherium, was described in 2009 on the basis of a single tooth.
Ferugliotheriidae is one of three known families in the order Gondwanatheria, an enigmatic group of extinct mammals. Gondwanatheres have been classified as a group of uncertain affinities or as members of Multituberculata, a major extinct mammalian order. The best-known representative of Ferugliotheriidae is the genus Ferugliotherium from the Late Cretaceous epoch in Argentina. A second genus, Trapalcotherium, is known from a single tooth, a first lower molariform, from a different Late Cretaceous Argentinean locality. Another genus known from a single tooth, Argentodites, was first described as an unrelated multituberculate, but later identified as possibly related to Ferugliotherium. Finally, a single tooth from the Paleogene of Peru, LACM 149371, perhaps a last upper molariform, and a recent specimen from Mexico, may represent related animals.
Allotheria is an extinct clade of mammals known from the Mesozoic and early Cenozoic. Shared characteristics of the group are the presence of lower molariform teeth equipped with longitudinal rows of cusps and enlarged incisors. Typically, the canine teeth are also lost. Allotheria includes Multituberculata, Gondwanatheria, and probably Haramiyida, although some studies have recovered haramiyidans to be basal mammaliaforms unrelated to multituberculates. Allotherians are often placed as crown group mammals, more closely related to living marsupials and placentals (Theria) than to monotremes or eutriconodonts, though some studies place the entirety of Allotheria outside of crown Mammalia.
Eozostrodon is an extinct morganucodont mammaliaform. It lived during the Rhaetian stage of the Late Triassic. Eozostrodon is known from disarticulated teeth from South West England and estimated to have been less than 10 cm (3.9 in) in head-body length, slightly smaller than the similar-proportioned Megazostrodon.
Docodonta is an order of extinct Mesozoic mammaliaforms. They were among the most common mammaliaforms of their time, persisting from the Middle Jurassic to the Early Cretaceous across the continent of Laurasia. They are distinguished from other early mammaliaforms by their relatively complex molar teeth. Docodont teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a mortar-and-pestle. This is a case of convergent evolution with the tribosphenic teeth of therian mammals. There is much uncertainty for how docodont teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "symmetrodonts", namely Woutersia, Delsatia.
Prozostrodon is an extinct genus of probainognathian cynodonts that was closely related to mammals. The remains were found in Brazil and are dated to the Carnian age of the Late Triassic. The holotype has an estimated skull length of 6.7 centimetres (2.6 in), indicating that the whole animal may have been the size of a cat. The teeth were typical of advanced cynodonts, and the animal was probably a carnivore hunting reptiles and other small prey.
Gobiconodon is an extinct genus of carnivorous mammals belonging to the family Gobiconodontidae. Undisputed records of Gobiconodon are restricted to the Early Cretaceous of Asia and North America, but isolated teeth attributed to the genus have also been described from formations in England and Morocco dating as far back as the Middle Jurassic. Species of Gobiconodon varied considerably in size, with G. ostromi, one of the larger species, being around the size of a modern Virginia opossum. Like other gobiconodontids, it possessed several speciations towards carnivory, such as shearing molariform teeth, large canine-like incisors and powerful jaw and forelimb musculature, indicating that it probably fed on vertebrate prey. Unusually among predatory mammals and other eutriconodonts, the lower canines were vestigial, with the first lower incisor pair having become massive and canine-like. Like the larger Repenomamus there might be some evidence of scavenging.
Morganucodonta is an extinct order of basal Mammaliaformes, a group including crown-group mammals (Mammalia) and their close relatives. Their remains have been found in Southern Africa, Western Europe, North America, India and China. The morganucodontans were probably insectivorous and nocturnal, though like eutriconodonts some species attained large sizes and were carnivorous. Nocturnality is believed to have evolved in the earliest mammals in the Triassic as a specialisation that allowed them to exploit a safer, night-time niche, while most larger predators were likely to have been active during the day.
Kuehneotherium is an early mammaliaform genus, previously considered a holothere, that lived during the Late Triassic-Early Jurassic Epochs and is characterized by reversed-triangle pattern of molar cusps. Although many fossils have been found, the fossils are limited to teeth, dental fragments, and mandible fragments. The genus includes Kuehneotherium praecursoris and all related species. It was first named and described by Doris M. Kermack, K. A. Kermack, and Frances Mussett in November 1967. The family Kuehneotheriidae and the genus Kuehneotherium were created to house the single species Kuehneotherium praecursoris. Modeling based upon a comparison of the Kuehneotherium jaw with other mammaliaforms indicates it was about the size of a modern-day shrew between 4 and 5.5 g at adulthood.
Brasilodon is an extinct genus of small, mammal-like cynodonts that lived in what is now Brazil during the Norian age of the Late Triassic epoch, about 225.42 million years ago. While no complete skeletons have been found, the length of Brasilodon has been estimated at 12 centimetres (4.7 in). Its dentition shows that it was most likely an insectivore. The genus is monotypic, containing only the species B. quadrangularis. Brasilodon belongs to the family Brasilodontidae, whose members were some of the closest relatives of mammals, the only cynodonts alive today. Two other brasilodontid genera, Brasilitherium and Minicynodon, are now considered to be junior synonyms of Brasilodon.
Asilisaurus ; from Swahili, asili, and Greek, σαυρος is an extinct genus of silesaurid archosaur. The type species is Asilisaurus kongwe.Asilisaurus fossils were uncovered in the Manda Beds of Tanzania and date back to the early Carnian, making it one of the oldest known members of the Avemetatarsalia. It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of Asilisaurus has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians.
Mitredon is an extinct genus of cynodonts which existed in the Fleming Fjord Formation of Greenland during the Rhaetian age of the Late Triassic epoch. The type and only species is Mitredon cromptoni.
LACM 149371 is an enigmatic fossil mammalian tooth from the Paleogene of Peru. It is from the Santa Rosa fossil site, which is of uncertain age but possibly late Eocene or Oligocene. The tooth is poorly preserved and may have been degraded by acidic water or because it passed through a predator's digestive tract. Its largest dimension is 2.65 mm. It is triangular in shape and bears six cusps that surround the middle of the tooth, where there are three basins (fossae). Crests connects the cusps and separate the fossae. The microscopic structure of the enamel is poorly preserved.
Trapalcotherium is a fossil mammal from the Cretaceous of Argentina in the family Ferugliotheriidae. The single species, T. matuastensis, is known from one tooth, a first lower molar. It is from the Allen Formation, which is probably Maastrichtian in age, and was first described in 2009. The tooth bears two rows of cusps, one at the inner (lingual) side and the other at the outer (labial) side, which are connected by transverse ridges separated by deep valleys. This pattern is reminiscent of Ferugliotherium, a gondwanathere mammal from similarly aged deposits in Argentina, and Trapalcotherium is therefore recognized as a member of the same family Ferugliotheriidae. Ferugliotheriidae is one of two families of gondwanatheres, an enigmatic group without close relationships to any living mammals.
Alemoatherium is an extinct genus of prozostrodontian cynodont which lived in the Late Triassic of Brazil. It contains a single species, A. huebneri, named in 2017 by Agustín Martinelli and colleagues. The genus is based on UFSM 11579b, a left lower jaw (dentary) found in the Alemoa Member of the Santa Maria Formation, preserving the late Carnian-age Hyperodapedon Assemblage Zone. Alemoatherium was among the smallest species of cynodonts found in the rich synapsid fauna of the Santa Maria Formation. Its blade-like four-cusped postcanine teeth show many similarities with those of dromatheriids, an obscure group of early prozostrodontians.
Arisierpeton is an extinct genus of synapsids from the Early Permian Garber Formation of Richards Spur, Oklahoma. It contains a single species, Arisierpeton simplex.
Kwanasaurus is an extinct genus of silesaurid dinosauromorph reptiles from the Late Triassic of Colorado. It is known from a single species, Kwanasaurus williamparkeri. Kwanasaurus had a deeper, stronger skull and greater specialization for herbivory compared to other silesaurids. It also possessed many unique characteristics of the snout, ilium, and lower part of the femur. It was described along with new specimens of Dromomeron from the Eagle Basin, the northernmost extent of the Chinle Formation.
Bocaconodon is an early mammaliaform genus that lived during the Pliensbachian of Mexico. The type and only species, Bocaconodon tamaulipensis, was named and described in 2008. It is known from a single specimen, a partial right dentary bone preserving two nearly complete molar teeth and the rear portion of a third molar. The specimen was found at the Huizachal Canyon locality, "a Pliensbachian floodplain siltstone in the La Boca Formation".
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.
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.