Scylacops Temporal range: Late Permian; 259.0 to 254.0 Ma | |
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Skull in lateral, dorsal, and ventral views | |
Scientific classification ![]() | |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Therapsida |
Family: | † Gorgonopsidae |
Subfamily: | † Gorgonopsinae |
Genus: | † Scylacops Broom, 1913 |
S. capensis and S. bigendens | |
Type species S. capensis |
Scylacops (meaning "face that tears") is an extinct genus of Gorgonopsia. It was first named by Broom in 1913, [1] and contains two species, S. bigendens, and S. capensis. Its fossils have been found in South Africa and Zambia. It is believed to be closely related to the Gorgonopsian Sauroctonus progressus. Scylacops was a moderately sized Gorgonopsid. [2]
Scylacops is an carnivorous therapsid, existing from 259.0 to 254.0 Ma. S. bigendens was first described by Brink and James Kitching in 1953, although its original description was Sycocephalus bigendens. [3]
According to the paleobiology database Scylacops specimens have been found in the following locations in South Africa; Uitsspansfontein at Beaufort West, Dunedin, Wellwood, and Sondagsriviershoek. Scylacops is also known from Zambia. [2]
Although there have been multiple alignments for Scylacops within Gorgonopsidae starting with Broom's original declaration that Scylacops is “allied with Gorgonops torous,” morphological similarities point to it as a close relative of Sauroctonus progressus. [1] [2] Battail & Surkov described Gorgonopsinae a subfamily of Gorgonopsidae. However, now only Rubidgeinae is recognized as a sub-family of Gorgonopsidae. [4] Because Battail & Surkov diagnosed Scylacops as Gorgonopsinae, a description of Gorgonopsinae is warranted. Gorgonopsinae is diagnosed by a thin zygomatic arch, a ventrally extended edge of posterior cranial roof, an often present preparietal and a post temporal fossa oriented horizontally. [2] Because of the research and analysis of Battail & Surkov, a phylogeny which includes Scylacops as sister Sauroctonus to can be inferred.
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Phylogeny of Gorgonopsia according to Bendel et al. 2018 [5] |
Because of Scylacops’ relationships in the Therapsid clade. Broom describes the key morphological differences between Gorgonopsia and Therocephalia. Gorgonopsia have a broad parietal region vs a narrow one in Therocephalians. Gorgonopsians have a preparietal while Therocephalians do not. Gorgonopsians have a large post frontal while Therocephalians have a small one. Gorgonopsians have a single true vomer while Therocephalians have a pair of prevomers. Gorgonopsians have strong mandible symphysis while Therocephalians have loosely articulated jaws. Gorgonopsians have an angular with a deep grove while they are perforated in Therocephalians. [1]
Analysis showing cyclical growth in cortical fibrolamellar bone tissue in Scylacops and gorgonopsians as a whole is one reason they are considered more distantly related to crown Mammilla. Early–Middle Triassic non-mammalian cynodonts Cynognathus and Early Jurassic Tritylodon exhibit rapid, sustained growth and are placed closer to crown Mammilla. [6]
A Lateral view diagnoses include a large septomaxilla, a large prefrontal which meets the post- frontal and shuts out the frontal from the orbital margin, and the increased forward extension of the zygomatic portion of the squamosal. Dorsal view diagnoses include a large frontal which does not reach the orbital margins, behind the frontal is a large postfrontal bounded by the prefrontal, the frontal, the parietal, and the postorbital. [1] Scylacops has 5 incisors 1 canine and 3 molars. [3] Scylacops has a similar occipital region to Lycaenops ornatus, another gorgonopsian discovered by Broom in 1920. Its occipital region is described with the following characteristics. The interparietal is a large broad bone between the parietal and supraoccipital. The interparietal is entirely on the occipital face. Below it lies a large broad supraoccipital forming the upper margin of the foramen magnum. The interparietal articulates inferiorly with the exoccipital and the opisthotic with the tabular forming the outer portion of the occiput. Above the interparietal is articulation with the parietal and the squamosal. As part of the articulation with the quadrate is a long process lying against the squamosal externally and the opisthotic internally. The exoccipitals are small and form the lateral walls of the foramen magnum. [7]
Battail & Surkov describe Scylacops as the closest overall morphological relative to the Russian gorgonopsine Sauroctonus progressus. Battail & Surkov diagnose S. progressus by small orbits, a skull narrow posteriorly, infraorbital and temporal widths are very narrow, the postorbital bar widens ventrally with transverse flanges of pterygoids, and has 4-6 upper post canine teeth. Like Scylacops it is considered a medium-sized gorgonopsid. [2] Scylacops SAM-PK-10188 from the Iziko South African Museum has measurements as follows; Humerus 100 mm, Radii 83.25 mm, Ulna 99 mm, Femur 174.8 mm, Fibula, 96.67 mm. [8]
Therapsids have quick osteogenesis in the cortical fibrolamellar bone tissue. Analysis of Scylacops sp. specimen SAM-PK-10188 from Dunedin shows a cyclical and zonal growth pattern. This cyclical growth is a strong effect of Scylacops’ environment. Scylacops’ cortical fibrolamellar bone tissue shows a phylogenic relationship between Scylacops and the gorgonopsid from the Rubidgeinae sub-family Aelurognathus . However, there is a clear distinction between the two. Scylacops was distinctly cyclical with intermediate growth, where periods of fast growth were interrupted by periods of slow growth or halting of growth. Aelurognathus sustained fast growth early in ontogeny only to be interrupted at a later stage of growth. [8]
SAM-PK-10188’s histology shows wide zones separated by annuli and LAGs. These wide zones are composed of a woven-fibered bone matrix with mainly longitudinally oriented channels and osteonal deposits forming primary osteons and fibrolamellar bone tissue. The outer cortical periphery is irregular with few channels opening subperiosteally. The longitudinally oriented channels in this region show few osteonal deposits and are larger than well-developed primary osteons. Organization of primary osteons varies depending on the element and even locally within the same section. The medullary cavity in all the elements are lined by endosteally lamellated bone the extent of which varies depending on the position and type of element. Secondary reconstruction is prevalent in the inner cortex resulting in enlarged resorption cavities. [8]
Stratigraphy of the Karoo Supergroup in the Karoo Basin | ||||
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Period | Group | Formation west of 24°E | Formation east of 24°E | Assemblage Zone |
Jurassic | Drakensberg | Hiatus | Drakensberg | |
Stormberg | Clarens | |||
Triassic | Elliot | |||
Molteno | ||||
Beaufort | ||||
Burgersdorp | Cynognathus | |||
Katberg | Lystrosaurus | |||
Balfour | ||||
Permian | Dicynodon | |||
Teekloof | ||||
Cistecephalus | ||||
Middleton | ||||
Tropidostoma | ||||
Pristerognathus | ||||
Abrahams-Kraal | Abrahams-Kraal | |||
Tapinocephalus | ||||
Eodicynodon | ||||
Ecca | Waterford | Waterford | ||
Tierberg / Fort Brown | Fort Brown | |||
Laingsburg / Ripon | Ripon | |||
Collingham | Collingham | |||
Whitehill | Whitehill | |||
Prince Albert | Prince Albert | |||
Carboniferous | Dwyka | Elandsvlei | Elandsvlei | |
References: Rubidge (2005), [9] Selden and Nudds (2011). [10] |
The Cistecephalus zone is regarding the biostratigraphy of a genus of burrowing dicynodont from the late Permian of South Africa. [11] The strata assigned to the zone is made from gray-green, bluish-green, purple and reddish mudstone with lenticular sandstone and siltstone beds. Fossils mostly are found in mudstone horizons lasting several miles. The Uitsspansfontein locality in Beaufort west is characterized by a low relief and small exposures covering strata immediately below the Cistecephalus band. [12] Beaufort biostratigraphy is made up of five zones, the Daptocephalus, Cistecephalus, Tropidostoma, Pristerognathus and Tapinocephalus. The Cistecephalus zone has an age range of around 257 to 255 ma. Beaufort West is lithographically siliciclastic. The Geologic age in which Scylacops lived across all sites, is the Wuchiapingian, Late Permian. [13]
Parts of the upper Cistecephalus zone may be referenced as Endothiodon zone due to many endothiodont specimens found by Broom and Von Huene directly above the recognized Cistecephalus zone. However, there is no lithological distinction between the two rock beds. They both consist of the same identical gray-green and bluish-green and purple mudstone and shale sediments, interbedded with lenticular sandstone and siltstones. Kitching proposes that the varied color of mudstones and lenticular sandstones are not reliable markers of separation as they do not follow a consistent stratigraphical plane but are sporadic across the Beaufort series. [12]
The only location outside of South Africa where Scylacops has been found is the Madumabisa Mudstone formation in the Drysdall and Kitching locality 3–4, Upper Luangwa Valley, Zambia. It has a mudstone Lithography, and is geologically in the Wuchiapingian. [14]
Therapsida is a major group of eupelycosaurian synapsids that includes mammals and their ancestors. 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. The earliest fossil attributed to Therapsida used to be Tetraceratops insignis from the Lower Permian. However in 2020, a new study has found that Tetraceratops is not actually a true Therapsid, but should be considered to be a member of the more ancient Sphenacodontia from which the therapsids evolved.
Gorgonopsia is an extinct group of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw.
Dinogorgon is a genus of gorgonopsid from the Late Permian of South Africa and Tanzania. The generic name Dinogorgon is derived from Greek, meaning "terrible gorgon", while its species name rubidgei is taken from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. The type species of the genus is D. rubidgei.
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 Cistecephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in South Africa. This biozone has outcrops located in the Teekloof Formation north-west of Beaufort West in the Western Cape, in the upper Middleton and lower Balfour Formations respectively from Colesberg of the Northern Cape to east of Graaff-Reinet in the Eastern Cape. The Cistecephalus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Late Permian in age.
Euchambersia is a genus of therocephalian therapsid that lived during the Late Permian, approximately 255 million years ago, in what is now South Africa. The genus contains a single species, Euchambersia mirabilis, named by paleontologist Robert Broom in 1931 from a skull missing the lower jaws; a second skull, belonging to an immature individual, was later described. It is a member of the family Akidnognathidae, which historically has also been referred by as the synonymous Euchambersiidae.
Sauroctonus is an extinct genus of therapsids. Sauroctonus progressus was a large gorgonopsid that lived in the Late Permian epoch before the Permian-Triassic extinction event that wiped out many life forms on Earth. Its fossils have been found in the Usili Formation of Tanzania and the Sokolki Assemblage Zone of the Volga Basin of Russia.
Moschorhinus is an extinct genus of therocephalian in the family Akidnognathidae, with only one species: M. kitchingi. It was a carnivorous, lion-sized synapsid which has been found in the Late Permian to Early Triassic of the South African Karoo Supergroup. It had a broad, blunt snout which bore long, straight canines. It appears to have replaced the gorgonopsids ecologically, and hunted much like a big cat. While most abundant in the Late Permian, it survived a little after the Permian Extinction, though these Triassic individuals had stunted growth.
Aelurognathus is an extinct genus of gorgonopsian therapsids from the Permian of South Africa.
Rubidgea is a genus of gorgonopsid from the upper Permian of South Africa and Tanzania, containing the species Rubidgea atrox. The generic name Rubidgea is sometimes believed to be derived from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. However, this generic name was actually erected in honor of Rubidge's paternal grandfather, Sydney Rubidge, who was a renowned fossil hunter. Its species name atrox is derived from Latin, meaning “fierce, savage, terrible”. Rubidgea is part of the gorgonopsian subfamily Rubidgeinae, a derived group of large-bodied gorgonopsians restricted to the Late Permian (Lopingian). The subfamily Rubidgeinae first appeared in the Tropidostoma Assemblage Zone. They reached their highest diversity in the Cistecephalus and Daptocephalus assemblage zones of the Beaufort Group in South Africa.
Theriognathus is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, known from fossils from South Africa, Zambia, and Tanzania. Theriognathus has been dated as existing during the Late Permian. Although Theriognathus means mammal jaw, the lower jaw is actually made up of several bones as seen in modern reptiles, in contrast to mammals. Theriognathus displayed many different reptilian and mammalian characteristics. For example, Theriognathus had canine teeth like mammals, and a secondary palate, multiple bones in the mandible, and a typical reptilian jaw joint, all characteristics of reptiles. It is speculated that Theriognathus was either carnivorous or omnivorous based on its teeth, and was suited to hunting small prey in undergrowth. This synapsid adopted a sleek profile of a mammalian predator, with a narrow snout and around 1 meter long. Theriognathus is represented by 56 specimens in the fossil record.
Aelurosaurus is a small, carnivorous, extinct genus of gorgonopsian therapsids from the Mid Permian to Late Permian of South Africa. It was discovered in the Karoo Basin of South Africa, and first named by Richard Owen in 1881. It was named so because it appeared to be an ancestor for cat-like marsupials, but not yet a mammal itself. It contains five species, A. felinus, A. whaitsi, A. polyodon, A. wilmanae, and A.? watermeyeri. A. felinus, the type species, is generally well described with established features, while the other four species are not due to their poorly preserved holotypes.
Clelandina is an extinct genus of rubidgeine gorgonopsian from the Late Permian of Cistecephalus Assemblage Zone of South Africa. It was first named by Broom in 1948. The type and only species is C. rubidgei. It is relatively rare, with only four known specimens.
Eriphostoma is an extinct genus of gorgonopsian therapsids known from the Middle Permian of Tapinocephalus Assemblage Zone, South Africa. It has one known species, Eriphostoma microdon, and was first named by Robert Broom in 1911. It is the oldest known gorgonopsian and among the smallest and most basal members of the clade.
Aulacephalodon is an extinct genus of medium-sized dicynodonts, or non-mammalian synapsids, that lived during Permian period, about 299-252 million years ago. Individuals of Aulacephalodon are commonly found in the Lower Beaufort Group of the Karoo Supergroup of South Africa and Zambia. Rising to dominance during the Late Permian, Aulacephalodon were the dominant terrestrial vertebrate herbivores until they became extinct during the Triassic. No living relatives of Aulacephalodon exist today. Two species have been named, the type species, A. bainii, and a second species, A. peavoti. However, debate exists among paleontologists if A. peavoti is a true member of the genus Aulacephalodon. Therefore, a majority of the information known about Aulacephalodon is in reference to discoveries about A. bainii.
Silpholestes is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species Silpholestes jackae was named by South African paleontologist Robert Broom in 1948 from the Cistecephalus Assemblage Zone.
Polycynodon is an extinct genus of therocephalians from the Late Permian of South Africa. It is known from the Cistecephalus Assemblage Zone. The type species was first described as Octocynodon elegans by South African paleontologist Robert Broom in 1940, but the name Octocynodon was preoccupied by a genus of labrid fish first described in 1904. Along with John T. Robinson, Broom instated Polycynodon as a replacement name for O. elegans in 1948. Polycynodon is classified in Baurioidea, although its relationship to other baurioid therocephalians is uncertain.
Pelictosuchus is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. It is classified in the family Akidnognathidae. The type species Pelictosuchus paucidens was named by South African paleontologist Robert Broom in 1940 from the Dicynodon Assemblage Zone.
Rubidgeinae is an extinct subfamily of gorgonopsid therapsids known only from Africa. They were among the largest gorgonopsians, and their fossils are common in the Cistecephalus and Daptocephalus assemblage zones of the Karoo Basin. They lived during the Late Permian, and became extinct at the end of the Permian.
Bulbasaurus is an extinct genus of dicynodont that is known from the Lopingian epoch of the Late Permian period of what is now South Africa, containing the type and only species B. phylloxyron. It was formerly considered as belonging to Tropidostoma; however, due to numerous differences from Tropidostoma in terms of skull morphology and size, it has been reclassified the earliest known member of the family Geikiidae, and the only member of the group known from the Tropidostoma Assemblage Zone. Within the Geikiidae, it has been placed close to Aulacocephalodon, although a more basal position is not implausible.