Scylacops

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Scylacops
Temporal range: Late Permian; 259.0 to 254.0 Ma
The Osteology of the Reptiles p53.png
Skull in lateral, dorsal, and ventral views
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Gorgonopsia
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]

Contents

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]

Systematics

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.

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 shows cyclical growth in cortical fibrolamellar bone tissue in Scylacops. Early–Middle Triassic non-mammalian cynodonts Cynognathus and Early Jurassic Tritylodon exhibit rapid, sustained growth and are placed closer to crown Mammalia. [6]

Description/morphology

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]

Sauroctonus progressus Sauroctonus progressus09.jpg
Sauroctonus progressus

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]

Histology

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]

Aelurognathus tigriceps Aelur tigriceps1DB.jpg
Aelurognathus tigriceps


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

Stratigraphy of the Karoo Supergroup in the Karoo Basin
Period Group Formation west of 24°EFormation 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]

See also

Related Research Articles

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<i>Gorgonops</i> Extinct genus of therapsids

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<i>Inostrancevia</i> Extinct genus of therapsids

Inostrancevia is an extinct genus of large carnivorous therapsids which lived during the Late Permian in what are now Siberia, Russia and Southern Africa. The first-known fossils of this gorgonopsian were discovered in the Northern Dvina, where two almost complete skeletons were exhumed. Subsequently, several other fossil materials were discovered in various oblasts, and these finds will lead to a confusion about the exact number of valid species in the country, before only three of them were officially recognized: I. alexandri, I. latifrons and I. uralensis. More recent research carried out in South Africa has discovered fairly well-preserved remains of the genus, being attributed to the species I. africana. An isolated left premaxilla suggests that Inostrancevia also lived in Tanzania during the earliest Lopingian age. The whole genus is named in honor of Alexander Inostrantsev, professor of Vladimir P. Amalitsky, the paleontologist who described the taxon.

<i>Dinogorgon</i> Extinct genus of therapsids

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.

<i>Tapinocephalus</i> Assemblage Zone

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<i>Cistecephalus</i> Assemblage Zone

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<i>Rubidgea</i> Extinct genus of therapsids

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<i>Theriognathus</i> Extinct genus of therapsids from late Permian South Africa and Tanzania

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<i>Clelandina</i> Extinct genus of therapsids

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<i>Bulbasaurus</i> Extinct genus of dicynodonts

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<i>Nochnitsa</i> Extinct genus of therapsids

Nochnitsa is an extinct genus of gorgonopsian therapsids who lived during an uncertain stage of the Permian in what is now European Russia. Only one species is known, N. geminidens, described in 2018 from a single specimen including a complete skull and some postcranial remains, discovered in the red beds of Kotelnich, Kirov Oblast. The genus is named in reference to Nocnitsa, a nocturnal creature from Slavic mythology. This name is intended as a parallel to the Gorgons, which are named after many genera among gorgonopsians, as well as for the nocturnal behavior inferred for the animal. The only known specimen of Nochnitsa is one of the smallest gorgonopsians identified to date, with a skull measuring close to 8 cm (3.1 in) in length. The rare postcranial elements indicate that the animal's skeleton should be particularly slender.

Phorcys is an extinct genus of gorgonopsian that lived during the Middle Permian period (Guadalupian) of what is now South Africa. It is known from two specimens, both portions from the back of the skull, that were described and named in 2022 as a new genus and species P. dubei by Christian Kammerer and Bruce Rubidge. Phorcys was recovered from the lowest strata of the Tapinocephalus Assemblage Zone (AZ) of the Beaufort Group, making it one of the oldest known gorgonopsians in the fossil record—second only to fragmentary remains of an indeterminate specimen from the older underlying Eodicynodon Assemblage Zone. The generic name is from Phorcys of Greek mythology, the father of the Gorgons from which the gorgonopsians are named after, and refers to its status as one of the oldest representatives of the group.

References

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  5. Bendel, Eva-Maria. “Cranial anatomy of the gorgonopsian Cynariops robustus based on CT- reconstruction.” PLoS ONE 13.11 (2018): 1-37.
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