Dinogorgon

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.

Dinogorgon Temporal range: Late Permian ~259–254 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype skull of D. rubidgei
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Therapsida
Family:	†Gorgonopsidae
Tribe:	†Rubidgeini
Genus:	†Dinogorgon Broom 1936
Type species
†Dinogorgon rubidgei Broom 1936
Synonyms
Dinogorgon quinquemolaris Huene 1950 Dinogorgon oudebergensis Brink & Kitching 1953 Prorubidgea robusta Brink & Kitching 1953 Rubidgea quinquemolaris Gebauer 2007

Dinogorgon is part of the gorgonopsian subfamily Rubidgeinae, a derived group of large-bodied gorgonopsians restricted to the Late Permian (Lopingian). The Rubidgeinae subfamily first appeared in the Tropidostoma Assemblage Zone, and reached their highest diversity in the Cistecephalus and Daptocephalus assemblage zones of the Beaufort Group in South Africa[1][2][3][4].

History of discovery

Holotype of D. quinquemolaris, a synonym of D. rubidgei

The type species of Dinogorgon rubidgei was discovered on Wellwood farm, a farm owned by the grandfather of Bruce Rubidge, Sidney H. Rubidge, outside of Graaff-Reinet. The fossil was likely recovered by Haughton himself sometime in the 1930s or 1940s, and were only described by British paleonologist, Sidney H. Haughton, and James Kitching between 1953 and 1965[5][6][7].

Description

Dinogorgon was one of the smaller species of rubidgeinae, with the largest specimens only measuring at 2m (6.6 ft). Nevertheless, it was still a formidable predator, and likely preyed on reptiles and smaller therapsids[8][9]. Like more derived rubidgeines, Dinogorgon had a number of bosses on its skull, likely to reduce the stresses caused by struggling prey. Its snout was deep but narrow, similar to Aelurognathus[10], but narrower than Rubidgea and Clelandina. It had 4 to 5 upper and lower postcanine teeth, which further distinguishes it from Rubidgea[11][12]. Three subspecies are currently recognised in the genus: D. rubidgei, D. quinquemolaris, and D. pricei.

Classification

Restoration of D. rubidgei

The Rubidgeinae are a subfamily of derived gorgonopsids that have only been found in Africa. They are composed of six genera and 17 species. The Rubidgeinae are closely related to their sister group, the Inostranceviinae, which have only been found in Russia. Out of the gorgonopsian clade, the systematics of the Rubidgeinae are the best resolved due to their distinctive character traits. The systematics of other gorgonopsian subfamilies remain chaotic due to a high degree of cranial homomorphism between taxa, making it difficult to distinguish different taxa effectively[13][14][15][16][17].

Dinogorgon shares many characteristics with Rubidgea and Clelandina, which has led some authors to synonymize them. All three are now considered to be part of the same tribe, Rubidgeini, rather than the same genus. The cladogram below (Kammerer et al. 2016) displays currently accepted systematic relationships of the Gorgonopsia.

Gorgonopsia	Aloposaurus       Cyonosaurus       Aelurosaurus   Gorgonopsidae   Scylacognathus       Eoarctops     Gorgonops       Njalila       Lycaenops       Arctognathus       Dinogorgon   Rubidgeinae   Aelurognathus       Rubidgea       Sycosaurus     Clelandina

Correlation

Numerous therapsid species, including rubidgenae gorgonopsids, are used as biostratigraphic markers in other African basins, such as the Upper Madumabisa Mudstone of Zambia, the Usili Formation of Tanzania, and the Chiweta Beds of Malawi[18].

References

1. Viglietti, P.A., Smith, R.M., Angielczyk, K.D., Kammerer, C.F., Fröbisch, J. and Rubidge, B.S. (2016-10-10). "The Daptocephalus Assemblage Zone (Lopingian), South Africa: a proposed biostratigraphy based on a new compilation of stratigraphic ranges". Journal of African Earth Sciences. 113: 153–164. Bibcode:2016JAfES.113..153V. doi:10.1016/j.jafrearsci.2015.10.011.CS1 maint: multiple names: authors list (link)
2. Nicolas, Merrill; Rubidge, Bruce S. (2010). "Changes in Permo-Triassic terrestrial tetrapod ecological representation in the Beaufort Group (Karoo Supergroup) of South Africa". Lethaia. 43 (1): 45–59. doi:10.1111/j.1502-3931.2009.00171.x. ISSN 1502-3931.
3. Kammerer, Christian F. (2015). "Cranial osteology of Arctognathus curvimola, a short-snouted gorgonopsian from the Late Permian of South Africa". Papers in Palaeontology. 1 (1): 41–58. doi:10.1002/spp2.1002. ISSN 2056-2802.
4. Kammerer, Christian F.; Smith, Roger M. H.; Day, Michael O.; Rubidge, Bruce S. (2015). "New information on the morphology and stratigraphic range of the mid-Permian gorgonopsian Eriphostoma microdon Broom, 1911". Papers in Palaeontology. 1 (2): 201–221. doi:10.1002/spp2.1012. ISSN 2056-2802.
5. Broom, Robert. "20. On a New Family of Carnivorous Therapsids from the Karroo Beds of South Africa." In Proceedings of the Zoological Society of London, vol. 108, no. 3, pp. 527-533. Oxford, UK: Blackwell Publishing Ltd, 1938.
6. Kitching, J.W., 1953. Studies on new specimens of the Gorgonopsia.
7. Haughton, S. H. (1965-12-01). "The Rubidge Collection of fossil Karroo vertebrates". ISSN 0078-8554. Cite journal requires |journal= (help)
8. Cruickshank, A. R. I. (1973). "THE MODE OF LIFE OF GORGONOPSIANS". ISSN 0078-8554. Cite journal requires |journal= (help)
9. Jenkins, Ian; Valkenburgh, Blaire Van (2002-10-01). "Evolutionary Patterns in the History of Permo-Triassic and Cenozoic Synapsid Predators". The Paleontological Society Papers. 8: 267–288. doi:10.1017/S1089332600001121. ISSN 1089-3326.
10. Norton, Luke Allan (2013-02-01). Relative growth and morphological variation in the skull of Aelurognathus (therapsida: gorgonopsia) (Thesis thesis).
11. Kemp T. S.; Parrington Francis Rex (1969-09-04). "On the functional morphology of the gorgonopsid skull". Philosophical Transactions of the Royal Society B: Biological Sciences. 256 (801): 1–83. Bibcode:1969RSPTB.256....1K. doi:10.1098/rstb.1969.0036.
12. Martins, Rui M. S.; Fröbisch, Jörg; Polcyn, Michael J.; Fernandez, Vincent; Araujo, Ricardo M. (2017-02-21). "Aspects of gorgonopsian paleobiology and evolution: insights from the basicranium, occiput, osseous labyrinth, vasculature, and neuroanatomy". PeerJ. 5: e3119. doi:10.7717/peerj.3119. PMC 5390774. PMID 28413721.
13. Kermack, Doris M.; Kermack, Kenneth A. (1984), Kermack, Doris M.; Kermack, Kenneth A. (eds.), "Dentitions, Tooth-Replacement and Jaw Articulation", The Evolution of Mammalian Characters, Springer US, pp. 66–88, doi:10.1007/978-1-4684-7817-4_5, ISBN 9781468478174
14. Sigogneau, D. (1968). "On the classification of the Gorgonopsia". ISSN 0078-8554. Cite journal requires |journal= (help)
15. Sigogneau-Russell, D., 1989. Theriodontia 1: Phthinosuchia, Eotitanosuchia, Gorgonopsia.
16. Gebauer, Eva V. I. (2014), "Re-assessment of the Taxonomic Position of the Specimen GPIT/RE/7113 (Sauroctonus parringtoni comb. nov., Gorgonopsia)", in Kammerer, Christian F.; Angielczyk, Kenneth D.; Fröbisch, Jörg (eds.), Early Evolutionary History of the Synapsida, Vertebrate Paleobiology and Paleoanthropology, Springer Netherlands, pp. 185–207, doi:10.1007/978-94-007-6841-3_12, ISBN 9789400768413
17. Kammerer, Christian F. (2016-01-26). "Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)". PeerJ. 4: e1608. doi:10.7717/peerj.1608. ISSN 2167-8359. PMC 4730894. PMID 26823998.
18. Parrington, F. R. (1974). "A new genus of gorgonopsid from East Africa". Annals of the South African Museum. 64: 47–52.