Tapinocaninus Temporal range: | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Synapsida |
Clade: | Therapsida |
Suborder: | † Dinocephalia |
Family: | † Tapinocephalidae |
Subfamily: | † Tapinocanininae |
Genus: | † Tapinocaninus Rubidge, 1991 |
Species: | †T. pamelae |
Binomial name | |
†Tapinocaninus pamelae Rubidge, 1991 | |
Tapinocaninus (Greek for "humble"- tapino, and "canine"- caninus) is an extinct genus of therapsids in the family Tapinocephalidae, of which it is the most basal member. Only one species is known, Tapinocaninus pamelae (meaning "Pamela's humble canine"). The species is named in honor of Rubidge's mother, Pamela. [1] Fossils have been found dating from the Middle Permian (Wordian age).
Tapinocaninus fossils were first found in the Eodicynodon Assemblage Zone of the Karoo deposits, in the Lower Beaufort Beds in Beaufort West. Five specimens are known, four found at Modderdrift farm and one found on Swartgrond farm. A holotype (NMQR 2987) and four paratypes (NMQR 2985, 2986, 3097 and ROZ K95). [1]
Two specimens were found by the director of the Bernard Price Institute for Paleontological Research (now the Evolutionary Studies Institute), Professor Bruce Rubidge. Three were found by John Nyaphuli of the National Museum Bloemfontein in the same sandstone. The excavation and preparation of NMQR 2986 the holotype NMQR 2987 was a large undertaking due to the large size of the specimens, and this process took place from 1985 to 2005. Air scribe machinery was used to prepare the specimens, along with manual tools such as a hammer and chisel in areas where matrix was more abundant. [1] [2]
Prior to the discovery of the Tapinocaninus, the Anteosaurinae were believed to be the most primitive dinocephalian, and the Tapinocephaline were believed to be the most derived dinocephalian of South Africa. When comparing features of Tapinocaninus to those discussed of Tapinoceohalinae through a cladistic analysis, Rubidge et al. (1991) found that a synapomorphy of the two were the expanded heels on the incisor teeth. [3] Thus, after its discovery, Tapinocaninus is considered the most primitive Tapinoceohaline. [1]
This species is known from several skulls, as most specimens found were lacking of the post cranial skeleton. It was a large animal, measuring 2.5m in length from snout to ilium. [2] With classic regression formulas using the circumference of the humerus and femur bones, researchers approximated that they averaged a body mass of 892.63Kg for the taxon (nearly 2,000lbs). [4] Tapinocaninus were also the largest therapsids from the Guadalupian. [5]
The skull roof and postorbital bar of Tapinocaninus shows pachyostotic thickening, which is consistent with other tapinocephaline dinocephalians. The skull roof is majorly composed of the frontal, which extends between the orbital and temporal fenestre. The external naris is bordered dorsally, anteriorly, and anteroventrally by the premaxilla bone. The maxilla forms a majority of the lateral area of the face, and it is swollen to allow room for the root of the canine tooth. [6] The temporal openings are relatively large, and subsequently, Tapinocaninus has a narrow intertemporal region, which is considered a primitive feature of Tapinocephalinae. The temporal fenestra are bordered ventrally and posteriorly by the squamosal, and dorsally by the postorbital. The squamosal and postorbital touch along the temporal opening, which is a feature commonly found in tapinocephalids. [7] Additionally, these taxon have a thin snout, sloping occipital, relatively small quadratojugal, prominent stapedial foramen, and relatively anterior position of the quadrate. [1]
The palate of Tapinocaninus has narrow vomers with a crest between them that surrounds the internal nares. The premaxilla that overlies the maxilla anteriorly and ventrally, and the maxilla contacts both the palatine and pterygoid medially. Over half the length of the palate is the pterygoid, and it has lateral flanges that extend ventrally and transversally. Additionally, the pterygoid touches the basisphenoid behind the interpterygoid vacuity. [1]
The vertebrae of Tapinocaninus are distinguished by their laterally facing fovea at the base of the neural spine. This feature is primitive for therapsids, another ancestral trait for this clade also includes the presence of intercentra in between the cervical vertebrae. Tapinocaninus have 36 vertebrae, 8 cervicals, 20 dorsals, 5 lumbars, 2 sacrals and 7 caudals. They have a long neural spine that extends all the way to the caudal vertebrae. [2] Their vertebral structure suggests that tapinocaninus had very short tails similar to anomodonts, but in contrast to anteosaurids. [8] The presence of only two sacral vertebrae in Tapinocaninus differs from other therapsids, such as Moschops which has three. [9]
There are ribs present along the entire vertebral column. In the cervical region, the ribs are shortened and flat. The longest ribs are present in the mid-dorsal region, and dorsal ribs 11-15 are barrel shaped to accommodate the large digestive system of Tapinocaninus. In the caudal region, the ribs are again shortened, in addition to being dorsoventrally flattened, posteriorly directed, and not fused to the caudal vertebrae [2]
The pectoral girdle of Tapinocaninus has a prominent scapula, with an enlarged dorsal end. The glenoid is straight, ventral facing, and thickened to comprise the coracoids and scapula. A ridge runs diagonally from the posterior dorsal end of the glenoid to the anterior end of the scapula, and this limits the movement of the clavicle over the scapula. The scapula also flares to connect with the anterior coracoid, which is a round, large bone. [2]
The pelvic girdle of the holotype NMQR 2987 is partially preserved, and the other specimens are also lacking of a complete structure. However, parallel grooves are found on the surface of the ischium, which suggest that they may have been connected by tissue. [9]
Three humeri were retained from various specimens of Tapinocaninus, although the right humerus of the holotype is the most complete, and well described in research. The bone has a narrow center and widens at the ends, with the proximal end larger than the distal. The deltopectoral crest flares and makes up a large portion of the length of the bone. The distal end of the humerus has a small entepicondyle and a larger ectepicondyle with fossa separating the two. [2] Tapinocaninus differs from Ulemosaurus and Moschops in that it has an entepicondylar foramen while the latter two taxon have ectepicondylar and entepicondylar foramen. [3] [10]
The holotype NMQR 2987 has both the left and right femora present. This specimen shows that the femur is more slender than the humerus. The femur is the same width at the proximal and distal ends, and it is flattened anteroposteriorly. Similar to other tapinocephalids, Tapinocaninus has a medially inflected femoral head. At the distal end of the femur, there are lateral and medial condyles, and the lateral condyle is slightly larger in size. [2]
Although there is currently no specimen with perfectly preserved teeth, the dental description for Tapinocaninus has been drawn from various skulls (NMQR 2984, NMQR 2986, NMQR 2987, ROZ K95).This dinocephalian has a heterodont dentition, consisting of incisors, canines and post canines. There are a maximum of five incisor teeth present in the premaxilla, all of which display talon and heel morphology. A singular canine is the first tooth in the maxilla bone, it is curved backward, and does not have a heel. Following the canine is the post canine teeth, characterized by pointed crowns and small, lingually situated heels. The dentition indicates that these animals were likely an herbivore or omnivore. [1]
Researchers suggest the forelimb posture of Tapinocaninus to be “intermediate” between sprawling and an upright posture. It is suggested that they are more upright standing than sphenacodonts, but more sprawled than theriodont theraspids. Their intermediate posture is can be explained by their long bones, in addition to the shape and positioning of the humerus and medially inflected femur. This postural stance would also be more supportive of the Tapinocaninus’ larger body size. [2] Additionally, the presence of intercentra only in the anterior dorsal vertebrae and medial directed zygapophyses in Tapinocaninus suggests that they had less undulatory locomotion in when compared to sphenacodonts. [11]
Heterodont dentition indicates that the teeth are morphologically differentiated by shape. [12] In Tapinocaninus, this includes incisors, canines, and post canines, all of which have different shapes which allows for a variety of functions. Tapinocaninus was likely an herbivore or a carnivore. [1]
The Eodicynodon Assemblage Zone is in the southwestern part of the Karoo Basin, and it is the lowest biozone of the Beaufort Group, under the Eosimops-Glanosuchus Subzone of the Tapinocephalus Assemblage Zone. The lower boundary lies at a stratigraphic horizon between the Ecca Group (Waterford Formation) and the Beaufort Group (Abrahamskraal Formation), which researchers Rubidge and Oelofsen considered to be a paleoshoreline. [13] It was named by Rubudge in 1995 after the most common therapsid present in the area, the Eodicynodon oosthuizeni. The lower boundary is set by the first appearance of Eodicynodon oosthuizeni in the zone, and the upper boundary by the first appearance of Eosimops newtoni, a dicynodont. Laterally, the biozone runs from Laingsburg to the south of Rietbron. [14]
The zone is identified by the existence of Eodicynodon oosthuizeni, a dicynodont, along with Tapinocaninus pamelae and Australosyodon nyaphulii, two types of dinocephalians. Tapinocaninus fossils account for approximately 10% of all tetrapod fossils found in this biozone. The thickness of this biozone ranges from 320 to 1100m, with the maximum thickness occurring at the Prince Albert Road station, and gradually thinning to the east and west of this point. The biozone is made up of siltstones, sandstones, and mudstones. Fossils of tetrapods are rare in this area, however, there are copious impressions of equisetalian and Glossopteris stems and leaves on the mudrock surfaces. When found, therapsid fossils are typically well preserved in the mud rock strata, and dinocephalians found in fine-grained sandstone. [14]
Dinocephalians are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.
Moschops is an extinct genus of therapsids that lived in the Guadalupian epoch, around 265–260 million years ago. They were heavily built plant eaters, and they may have lived partly in water, as hippopotamuses do. They had short, thick heads and might have competed by head-butting each other. Their elbow joints allowed them to walk with a more mammal-like gait rather than crawling. Their remains were found in the Karoo region of South Africa, belonging to the Tapinocephalus Assemblage Zone. Therapsids, such as Moschops, are synapsids, the dominant land animals in the Permian period, which ended 252 million years ago.
Thrinaxodon is an extinct genus of cynodonts, including the species T. liorhinus which lived in what are now South Africa and Antarctica during the Late Permian - Early Triassic. Thrinaxodon lived just after the Permian–Triassic mass extinction event, its survival during the extinction may have been due to its burrowing habits.
Robertia is an extinct genus of small herbivorous dicynodonts from the Middle to Late Permian of South Africa, between 260 and 265 million years ago. It is a monospecific genus, consisting of the type-species R. broomiana, which was classified by Lieuwe Dirk Boonstra in 1948 and named in honor of Robert Broom for his study of South African mammal-like reptiles.
Jonkeria is an extinct genus of dinocephalians. Jonkeria was a large and omnivorous animal, from the Tapinocephalus Assemblage Zone, Lower Beaufort Group, of the South African Karoo.
Anteosaurus is an extinct genus of large carnivorous dinocephalian synapsid. It lived at the end of the Guadalupian during the Capitanian age, about 265 to 260 million years ago in what is now South Africa. It is mainly known by cranial remains and few postcranial bones. Measuring 5–6 m (16–20 ft) long and weighing about 600 kg (1,300 lb), Anteosaurus was the largest known carnivorous non-mammalian synapsid and the largest terrestrial predator of the Permian period. Occupying the top of the food chain in the Middle Permian, its skull, jaws and teeth show adaptations to capture large prey like the giants titanosuchids and tapinocephalids dinocephalians and large pareiasaurs.
The Tapinocephalus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the middle Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately 2,000 metres (6,600 ft), occur from Merweville and Leeu-Gamka in its southernmost exposures, from Sutherland through to Beaufort West where outcrops start to only be found in the south-east, north of Oudshoorn and Willowmore, reaching up to areas south of Graaff-Reinet. Its northernmost exposures occur around the towns Fraserburg and Victoria West. The Tapinocephalus Assemblage Zone is the second biozone of the Beaufort Group.
The Eodicynodon Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately 620 metres (2,030 ft), occur south-east of Sutherland, north of Prince Albert, and south-east of Beaufort West. The Eodicynodon Assemblage Zone is the lowermost biozone of the Beaufort Group.
Eodicynodon is an extinct genus of dicynodont therapsids, a highly diverse group of herbivorous synapsids that were widespread during the middle-late Permian and early Triassic. As its name suggests, Eodicynodon is the oldest and most primitive dicynodont yet identified, ranging from the middle to late Permian and possessing a mix of ancestral anomodont/therapsid features and derived dicynodont synapomorphies.
Styracocephalus platyrhynchus is an extinct genus of dinocephalian therapsid that existed during the mid-Permian throughout South Africa, but mainly in the Karoo Basin. It is often referred to by its single known species Styracocephalus platyrhynchus. The Dinocephalia clade consisted of the largest land vertebrates and herbivores during the early to mid-Permian. This period is often also referred to as the Guadalupian epoch, approximately 270 to 260 million years ago.
Paraburnetia is an extinct genus of biarmosuchian therapsids from the Late Permian of South Africa. It is known for its species P. sneeubergensis and belongs to the family Burnetiidae. Paraburnetia lived just before the Permian–Triassic mass extinction event.
Lobalopex is an extinct genus of biarmosuchian therapsids. It was alive during the Late Permian and has only been found in the Teekloof Formation in South Africa. The only known species of the genus is Lobalopex mordax. Lobalopex is part of the clade of Burnetiamorpha, which have fossil specimens located in multiple areas of Africa and Russia.
Biseridens is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an eotitanosuchian in 1997, another well-preserved skull was found in the Qingtoushan Formation in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts.
Moschognathus is an extinct genus of dinocephalian therapsid in the family Tapinocephalidae. The genus includes only the type species M. whaitsi, named by palaeontologist Robert Broom in 1914. It was a short-snouted tapinocephalid, closely related to and resembling the well-known genus Moschops, but its skull is less thickened overall has a relatively longer and shallower snout by comparison. Indeed, Moschognathus has typically been regarded as a junior synonym of Moschops since 1969 after Lieuwe Dirk Boonstra sunk Moschognathus into Moschops, albeit retained as its own doubtfully valid species. However, researchers in the 21st century have expressed doubt over this synonymy and suggested that Moschognathus is a distinct taxon after all, including first by Christian Kammerer in a 2009 Ph.D. thesis and formally in 2015 by Alessandra D. S. Boos and colleagues in 2015. Moschognathus has since began to re-enter scientific literature of dinocephalians as a valid name and treated distinct from Moschops.
Pachydectes is an extinct genus of biarmosuchian therapsids from the Middle Permian of South Africa known from a single skull. The etymology of the name Pachydectes is derived from the Greek word pakhus, meaning "thick" or "thickened", and dektes, meaning "biter". In conjunction this name is representative of the unique pachyostotic bone present above the maxillary canine tooth found in the skull of the specimen. There is only one known species within the genus, Pachydectes elsi which is named in honor of the person who discovered the fossil.
Platycraniellus is an extinct genus of carnivorous cynodonts from the Early Triassic. It is known from the Lystrosaurus Assemblage Zone of the Normandien Formation in South Africa. P. elegans is the only species in this genus based on the holotype specimen from the Ditsong National Museum of Natural History in Pretoria, South Africa. Due to limited fossil records for study, Platycraniellus has only been briefly described a handful of times.
Criocephalosaurus is an extinct genus of tapinocephalian therapsids that lived in Southern Africa during the Guadalupian epoch of the Permian. They are the latest surviving dinocephalians, extending past the Abrahamskraal Formation into the lowermost Poortjie Member of the Teekloof Formation in South Africa. They are also regarded as the most derived of the dinocephalians, alongside Tapinocephalus, and the most abundant in the fossil record.
The Abrahamskraal Formation is a geological formation and is found in numerous localities in the Northern Cape, Western Cape, and the Eastern Cape of South Africa. It is the lowermost formation of the Adelaide Subgroup of the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup. It represents the first fully terrestrial geological deposits of the Karoo Basin. Outcrops of the Abrahamskraal Formation are found from the small town Middelpos in its westernmost localities, then around Sutherland, the Moordenaarskaroo north of Laingsburg, Williston, Fraserburg, Leeu-Gamka, Loxton, and Victoria West in the Western Cape and Northern Cape. In the Eastern Cape outcrops are known from Rietbron, north of Klipplaat and Grahamstown, and also southwest of East London.
Ictidosaurus was a therapsid genus found in the Abrahamskraal Formation of South Africa, which lived during the middle Permian period. Fossils of the type species were found in the Tapinocephalus, and the base of the Eodicynodon assembly zones, of the Karoo Basin. Older classifications of the species, along with many other specimens found in the Iziko South African Museum archives, were originally classified within therocephalian family names, in this case the Ictidosauridae, which has been reclassified as belonging to the Scylacosauridae. The type species is I. angusticeps.
Nyaphulia is an extinct genus of dicynodont therapsid from the middle Permian of South Africa, containing only the type species N. oelofseni. The generic name is in honour of John Nyaphuli of the National Museum of Bloemfontein, who contributed extensively to South African palaeontology and discovered the holotype specimen of Nyaphulia in 1982. Nyaphulia was initially named as a second species of the basal dicynodont Eodicynodon by Professor Bruce Rubidge in 1990 as E. oelofseni, named after his mentor in palaeontology and geology Dr. Burger Oelofsen.
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