Bullacephalus

Bullacephalus; Temporal range: Late Permian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Suborder:	† Biarmosuchia
Family:	† Burnetiidae
Genus:	† Bullacephalus ; Rubidge and Kitching, 2003
Species:	†B. jacksoni
Binomial name
	†Bullacephalus jacksoni; Rubidge and Kitching, 2003

Last updated January 09, 2024

Bullacephalus is an extinct genus of biarmosuchian therapsids belonging to the family Burnetiidae. The type species B. jacksoni was named in 2003. It is known from a relatively complete skull and lower jaw, discovered in the Late Permian Tapinocephalus Assemblage Zone of the Beaufort Group of South Africa.^[1] This genus of therapsida lived during the Late Permian period, approximately 250 million years ago. The name Bullacephalus comes from the Latin words "bullatus," meaning "bossed" or "knobbed," and "cephalus," meaning "head." This name refers to the distinctive bony knob on the top of the therapsid's skull, which contributes to the history of this genus. This stem based taxon includes Ictidorhinus or Hippasaurs. Bullacephalus can even be characterized as having a, “skull moderately to greatly pachyostotic; swollen boss present above the postorbital bar formed by the postfrontal and postorbital; deep linear sculpturing of the snout; exclusion of the jugal from the lateral temporal fenestra” (Day et al., 2016).^[2] These Therapsids have spongy bone skull roof, palatal process of premaxilla are long, diverticulum of naris adding them to the Burnetiamorph. Furthermore, the discovery of Bullacephalus has helped to refine the taxonomic classification of therapsids. Prior to its discovery, there was uncertainty regarding the relationship between different groups of therapsids, particularly the Burnetiamorpha and the Biarmosuchia. However, the distinctive features of Bullacephalus suggest that it is a member of the Burnetiamorpha, and provides a bridge between this group and the Biarmosuchia. The discovery of Bullacephalus has also highlighted the importance of continued exploration and excavation in areas that have yielded few therapsid fossils. The Beaufort Group of South Africa, where Bullacephalus was discovered, has been an important site for therapsid fossils, but much of the area remains unexplored. Further discoveries in this region and other areas around the world may provide new insights into the evolution and diversification of therapsids, as well as other groups of extinct animals. These discoveries will also help to refine our understanding of the history of life on Earth and the processes that have shaped the diversity of organisms that exist today.

Geological/paleoenvironmental information and historical information and discovery

This species is known from a complete skull and lower jaw that was discovered during the fieldwork of the Lower Beaufort group in the southern Karoo of South Africa. The Beaufort Group rocks in South Africa are well-known for their abundant Permo-Triassic therapsid fossils, which have allowed for biostratigraphic subdivision of the group into eight assemblage zones. In 1993, during fieldwork for biostratigraphic research in the lower Beaufort Tapinocephalus Assemblage Zone, a well-preserved skull of a medium-sized therapsid was discovered. The skull shares similarities with representatives of the Burnetiidae, a clade of basal therapsids that has only two known genera, Burnetia and Proburnetia, each represented by only one specimen. The newly discovered skull provides important new information about this enigmatic group of therapsids and their phylogenetic position within the Therapsida.^[3] While the limited amount of fossil material available has made it difficult to determine the exact relationships between Bullacephalus and other therapsids, its placement within the Burnetiamorpha suborder has shed some light on its evolutionary history. The Burnetiamorpha were a group of therapsids that appeared during the late Permian period and were widespread across Gondwana, the southern supercontinent that included present-day Africa, South America, Australia, India, and Antarctica. Bullacephalus is one of the most enigmatic members of this group, and its discovery has raised questions about the biogeography and evolutionary history of the Burnetiamorpha. (Liu, J., Rubidge, B., & Li, J., 2009).^[4] Further research into the morphology, phylogenetics, and ecology of Bullacephalus and other Burnetiamorpha will likely continue to yield insights into the evolution of therapsids and the complex history of life on Earth.

Taxonomy

Despite the limited amount of fossil material available, Bullacephalus has generated considerable interest among paleontologists due to its unique morphology and uncertain taxonomic classification. It is a part of the Burnetiamorpha suborder. Currently, the Burnetiamorpha comprise nine genera: Bullacephalus, Burnetia, Lemurosaurus, Lobalopex, Lophorhinus, Paraburnetia, and Pachydectes from South Africa. (Kruger et al., 2015).^[5] Some researchers have suggested that Bullacephalus are a type of Therapsida: Biarmoschia, related to the successful tetrapod Anomadontia helping researchers understand the basic morphology. This specific therapsid could be distinguished by the short snout, septomaxilla, and has a short facial exposure between nasal and maxilla, along with many other skull characteristics. Its unique morphology, particularly its short snout and septomaxilla, have led researchers to speculate about its feeding habits and ecological niche.

Description and paleobiology

The specimen of Bullacephalus is a moderately complete skull and lower jaw, with some missing anterior portions of the snout and lower jaw and badly weathered left side and skull roof posterior to the pineal foramen. The temporal opening is situated posteroventral to the orbit, and three pachyostosis bony bosses are present on the skull, similar to Burnetia and Proburnetia, but with a different appearance. The premaxilla is not preserved, but the remaining portion of the maxilla forms most of the side of the snout, exhibiting a rugose surface anteriorly and reaching the dorsal limit below the dorsomedially positioned nasal boss. The paired nasals do not have a large exposure on the skull roof, and the anterior portion is not preserved. The prefrontal is a large bone forming the anterodorsal and dorsal margins of the orbit, and above the orbit, it forms a prominent supraorbital boss, thinning anteriorly and extending to the lateral side of the skull as far as the nasal boss. The lacrimal has a large exposure anterior to the orbit, with a prominent rectangular fossa on its anterodorsal side bordering the prefrontal dorsally and the maxilla anteriorly. The zygomatic arch is thick and poorly defined, with unclear sutural contacts between the elements. The postorbital is narrow when viewed from the side, and its sutural borders are unclear.^[6] The moderately complete skull and lower jaw of Bullacephalus provide valuable information about its morphology and classification. The position of the temporal opening, posteroventral to the orbit, is a common feature among therapsids, and the presence of three pachyostosis bony bosses is a distinguishing characteristic of Burnetiamorpha. The rugose surface of the anterior portion of the maxilla suggests that Bullacephalus may have had a powerful bite. The nasal boss and the prominent supraorbital boss of the prefrontal are also notable features of Bullacephalus' skull, which may have served as attachment points for powerful jaw muscles. The rectangular fossa on the anterodorsal side of the lacrimal is another interesting feature of Bullacephalus' skull. This fossa may have been a site of attachment for the lacrimal gland. Alternatively, it may have been a site of attachment for muscles that control the opening and closing of the eye.The poor definition of the zygomatic arch and the unclear sutural borders of the postorbital are areas where further study is needed. These features may provide additional clues about the evolutionary relationships between Bullacephalus and other therapsids. Despite the missing anterior portions of the snout and lower jaw, the moderately complete skull and lower jaw of Bullacephalus are still valuable specimens for understanding the morphology and classification of this unique therapsid. Further study of Bullacephalus and other Burnetiamorpha will undoubtedly shed more light on the evolutionary history of therapsids and the complex ecosystems in which they lived.

Related Research Articles

Biarmosuchia is an extinct clade of non-mammalian synapsids from the Permian. Biarmosuchians are the most basal group of the therapsids. They were moderately-sized, lightly built carnivores, intermediate in form between basal sphenacodont "pelycosaurs" and more advanced therapsids. Biarmosuchians were rare components of Permian ecosystems, and the majority of species belong to the clade Burnetiamorpha, which are characterized by elaborate cranial ornamentation.

<span class="mw-page-title-main">Anteosauridae</span> Extinct family of therapsids

Anteosauridae is an extinct family of large carnivorous dinocephalian therapsids that are known from the Middle Permian of Asia, Africa, and South America.These animals were by far the largest predators of the Permian period, with skulls reaching 80 cm in length in adult individuals, far larger than the biggest gorgonopsian.

Anteosaurus is an extinct genus of large carnivorous dinocephalian synapsid. It lived at the end of the Guadalupian during the Capitanian stage, 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.

Burnetiidae is an extinct family of biarmosuchian therapsids that lived in the Permian period whose fossils are found in South Africa and Russia. It contains Bondoceras, Bullacephalus, Burnetia, Mobaceras, Niuksenitia, Paraburnetia and Proburnetia.

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.

Lemurosaurus is a genus of extinct biarmosuchian therapsids from the Late Permian of South Africa. The generic epithet Lemursaurus is a mix of Latin, lemures “ghosts, spirits”, and Greek, sauros, “lizard”. Lemurosaurus is easily identifiable by its prominent eye crests, and large eyes. The name Lemurosaurus pricei was coined by paleontologist Robert Broom in 1949, based on a single small crushed skull, measured at approximately 86 millimeters in length, found on the Dorsfontein farm in Graaff-Reinet. To date, only two skulls of the Lemurosaurus have been discovered, so body size is unknown. The second larger, more intact, skull was found in 1974 by a team from the National Museum, Bloemfontein.

Styracocephalus platyrhynchus (Greek for "spiked-head") 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.

Burnetia is an extinct genus of biarmosuchian therapsids in the family Burnetiidae, from the Late Permian of South Africa. Burnetia is known so far from a single holotype skull lacking the lower jaws described by South African paleontologist Robert Broom in 1923. Due to erosion and dorsoventral crushing, features of the skull are hard to interpret. Stutural lines are further distorted by the unusual shape of the skull roof, including many bosses and protuberances.

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.

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

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.

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

Ictidorhinus is an extinct genus of biarmosuchian therapsids. Fossils have been found from the Dicynodon Assemblage Zone of the Beaufort Group in the Karoo Basin, South Africa and are of Late Permian age. It had a short snout and proportionally large orbits. These characteristics may be representative of a juvenile animal, possibly of Lycaenodon. However, these two genera are not known to have existed at the same time, making it unlikely for Ictidorhinus material to be from a juvenile form of Lycaenodon.

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

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.

Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.

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

Herpetoskylax is an extinct genus of biarmosuchians which existed in South Africa. The type species is Herpetoskylax hopsoni. It lived in the Late Permian Period.

Blattoidealestes is an extinct genus of therocephalian therapsid from the Middle Permian of South Africa. The type species Blattoidealestes gracilis was named by South African paleontologist Lieuwe Dirk Boonstra from the Tapinocephalus Assemblage Zone in 1954. Dating back to the Middle Permian, Blattoidealestes is one of the oldest therocephalians. It is similar in appearance to the small therocephalian Perplexisaurus from Russia, and may be closely related.

Lycideops is an extinct genus of therocephalians from the Late Permian of South Africa. The type species is Lycideops longiceps, named in 1931 by South African paleontologist Robert Broom. Fossils of Lycideops come from the Dicynodon Assemblage Zone of the Beaufort Group. Lycideops is a member of the family Lycideopidae. Like other lycideopids, Lycideops has a long snout.

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 Aulacephalodon, although a more basal position is not implausible.

Abdalodon is an extinct genus of late Permian cynodonts, known by its only species A. diastematicus.Abdalodon together with the genus Charassognathus, form the clade Charassognathidae. This clade represents the earliest known cynodonts, and is the first known radiation of Permian cynodonts.

Leucocephalus is a genus of biarmosuchian belonging to the family Burnetiidae dating to the Wuchiapingian. It was found in the Tropidostoma Assemblage Zone of the Main Karoo Basin of South Africa. It is a monotypic taxon which contains one only species, Leucocephalus wewersi. The genus name Leucocephalus is derived from Greek. Leucos, meaning white; kephalos, meaning skull, as the Leucocephalus skull discovered was unusually pale. The species epithet wewersi comes from the farm employee who found the skull, Klaus ‘Klaasie’ Wewers.

References

1. 1. Day, M. O., Smith, R. M., Benoit, J., Fernandez, V., & Rubidge, B. S. (2018). A new species of burnetiid (Therapsida, Burnetiamorpha) from the early wuchiapingian of South Africa and implications for the evolutionary ecology of the family Burnetiidae. Papers in Palaeontology, 4(3), 453–475. https://doi.org/10.1002/spp2.1114
  2. Day, M., Rubidge, B., & Abdala, F. (2016). A new mid-permian burnetiamorph therapsid from the main Karoo Basin of South Africa and a phylogenetic review of Burnetiamorpha. Acta Palaeontologica Polonica, 61. https://doi.org/10.4202/app.00296.2016
  3. Kruger, A., Rubidge, B. S., Abdala, F., Chindebvu, E. G., & Jacobs, L. L. (2015). lende chiweta, a new therapsid from Malawi, and its influence on Burnetiamorph phylogeny and biogeography. Journal of Vertebrate Paleontology, 35(6). https://doi.org/10.1080/02724634.2015.1008698
  4. Sidor, C. A., & Welman, J. (2003). A second specimen oflemurosaurus pricei(therapsida: Burnetiamorpha). Journal of Vertebrate Paleontology, 23(3), 631–642. https://doi.org/10.1671/0272-4634(2003)023[0631:assolp]2.0.co;2
  5. Sidor, C. A., Hopson, J. A., & Keyser, A. W. (2004). A new burnetiamorph therapsid from the Teekloof Formation, Permian, of South Africa. Journal of Vertebrate Paleontology, 24(4), 938–950. https://doi.org/10.1671/0272-4634(2004)024[0938:anbtft]2.0.co;2
  6. Kammerer, C., & Sidor, C. (2020). A new burnetiid from the mid-permian of zambia and a reanalysis of Burnetiamorph Relationships (project). MorphoBank Datasets. https://doi.org/10.7934/p3785
  7. Rubidge, B. S., & Kitching, J. W. (2003). A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa. Palaeontology, 46(1), 199–210. https://doi.org/10.1111/1475-4983.00294
  8. Liu, J., Rubidge, B., & Li, J. (2009). A new specimen of biseridens qilianicus indicates its phylogenetic position as the most basal anomodont. Proceedings of the Royal Society B: Biological Sciences, 277(1679), 285–292. https://doi.org/10.1098/rspb.2009.0883
  9. SIDOR, Christian. (2003). The Naris and palate of Lycaenodon longiceps (Therapsida: BIARMOSUCHIA), with comments on their early evolution in the Therapsida. Journal of Paleontology, 77(5), 977–984. https://doi.org/10.1666/0022-3360(2003)077<0977:tnapol>2.0.co;2
  10. Smith, R. M., Rubidge, B. S., & Sidor, C. A. (2006). A new burnetiid (Therapsida: Biarmosuchia) from the Upper Permian of South Africa and its biogeographic implications. Journal of Vertebrate Paleontology, 26(2), 331–343. https://doi.org/10.1671/0272-4634(2006)26[331:anbtbf]2.0.co;2

↑ Rubidge, B.S.; Kitching, J.W. (2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294.
↑ Day, Michael; Rubidge, Bruce; Abdala, Fernando (2016). "A new mid-Permian burnetiamorph therapsid from the Main Karoo Basin of South Africa and a phylogenetic review of Burnetiamorpha". Acta Palaeontologica Polonica. 61. doi: 10.4202/app.00296.2016 . ISSN 0567-7920.
↑ Rubidge, Bruce S.; Kitching, James W. (January 2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294. ISSN 0031-0239.
↑ Liu, Jun; Rubidge, Bruce; Li, Jinling (2009-07-29). "A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 285–292. doi:10.1098/rspb.2009.0883. ISSN 0962-8452. PMC 2842672 .
↑ Kruger, Ashley; Rubidge, Bruce S.; Abdala, Fernando; Chindebvu, Elizabeth Gomani; Jacobs, Louis L. (2015-10-29). "Lende chiweta, a new therapsid from Malawi, and its influence on burnetiamorph phylogeny and biogeography". Journal of Vertebrate Paleontology. 35 (6): e1008698. doi:10.1080/02724634.2015.1008698. ISSN 0272-4634.
↑ Rubidge, Bruce S.; Kitching, James W. (January 2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294. ISSN 0031-0239.

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[RK03-1] Rubidge, B.S.; Kitching, J.W. (2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294.

[2] Day, Michael; Rubidge, Bruce; Abdala, Fernando (2016). "A new mid-Permian burnetiamorph therapsid from the Main Karoo Basin of South Africa and a phylogenetic review of Burnetiamorpha". Acta Palaeontologica Polonica. 61. doi: 10.4202/app.00296.2016 . ISSN 0567-7920.

[3] Rubidge, Bruce S.; Kitching, James W. (January 2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294. ISSN 0031-0239.

[4] Liu, Jun; Rubidge, Bruce; Li, Jinling (2009-07-29). "A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 285–292. doi:10.1098/rspb.2009.0883. ISSN 0962-8452. PMC 2842672 .

[5] Kruger, Ashley; Rubidge, Bruce S.; Abdala, Fernando; Chindebvu, Elizabeth Gomani; Jacobs, Louis L. (2015-10-29). "Lende chiweta, a new therapsid from Malawi, and its influence on burnetiamorph phylogeny and biogeography". Journal of Vertebrate Paleontology. 35 (6): e1008698. doi:10.1080/02724634.2015.1008698. ISSN 0272-4634.

[6] Rubidge, Bruce S.; Kitching, James W. (January 2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294. ISSN 0031-0239.

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