Platycraniellus

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Platycraniellus
Temporal range: Early Triassic
~252–247  Ma
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Epicynodontia
Genus:† Platycraniellus
van Hoepen, 1917
Species:
†P. elegans
Binomial name
†Platycraniellus elegans
van Hoepen, 1917
Synonyms

Platycranion, Platycranion elegans

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 (formerly known as the Transvaal Museum). Due to limited fossil records for study, Platycraniellus has only been briefly described a handful of times. [1]

Contents

Platycraniellus has been recognized as basal cynodonts, characterized by the broad temporal region of the skull and a short snout. Based on its phylogenetic position, Platycraniellus has a variety of morphologies similar to the sister taxon of Thrinaxodon , a relatively well-studied taxon. [1] [2]  

History of discovery

Platycraniellus elegans was discovered in the Lystrosaurus Assemblage Zone in the Free State Province of South Africa. The holotype (TM25) was first described by van Hoepen in 1916 and originally named Platycranionelegans, but this was potentially a printing error in the first publication. The following year, van Hoepen renamed the specimens Platycraniellus elegans. [1]

Originally, Platycraniellus elegans was classified as a member of the Galesauridae, a family which contained species with both incomplete and complete osseous secondary palates, by Hoposon, Kitching, and Brink. [3] [4] Later, this feature was used to classify the taxon into two families: Galesauridae and Thrinaxodontidae. Galesauridae is the name given to a taxon with incomplete secondary palates, whereas Thrinaxodontidae is the name given to a taxon with complete secondary palates. Platycraniellus elegans is now considered to be Thrinaxodontidae. [1] A larger specimen (NMQR 860) was originally referred to as Platycraniellus elegans by Brink, [4] however recent studies have considered this specimen to be Galesaurus planiceps by Hopson and Kitching [3] as well as Abdala. [1] Therefore, the holotype specimen is the only fossil record of Platycraniellus at this moment.

Description

Skull

The holotype specimen is generally in great condition; however, there are some significant damages caused by immature preparation techniques back then. In the dorsal view, the skull is broad in shape with a wide temporal region and two large lateral temporal fenestrae relative to the orbits. A short snout is one of the main characteristics of this group. The premaxilla has an anterior premaxillary foramen and a developed ascending process, which is damaged dorsally. The narrow septomaxilla is present in the nasal region but less developed in other species such as Thrinaxodon. The maxilla region contains a series of nutritive foramina and an infraorbital foramen with an anterior and ventral orientation. The nasal bone is wider where it contacts the lacrimal and prefrontal bones. The orbits face forward and outward. The parietal foramen extends back along the parietal bar and is at the center of the sagittal crest. The robust zygomatic arch is the main reason why the skull is so wide. Similar to Thrinaxodon , Progalesaurus, and Chiniquodon, the squamosal in the zygomatic portion extends anteriorly to the base of the postorbital bar. The jugal extends back along the zygomatic arch. [1] [2]

In ventral view, Platycraniellus has a complete osseous secondary palate similar to Thrinaxodon. The palate extends to the penultimate postcanine with the same length as the snout and shows a remarkably broad and short palatal process of the palatine at the posterior margin. A huge incisive foramen is present and reaches the posterior margin of the upper canine. At the base of the pterygoid process, the tiny quadrangular ectopterygoid is present. The quadrate is slightly convex anteriorly and contacts with the quadrate ramus of the pterygoid, which reaches posteriorly under the epipterygoid. This feature also appears in other basal cynodonts, such as Thrinaxodon and Galesaurids. The quadrate lateral condyle is less developed than the medial condyle in this group. Other similarities of skull morphology with Thrinaxodon are the development of the quadrate and the quadratojugal. The epipterygoid is greatly enlarged anteroposteriorly. Well-developed interorbital vacuity and a large trigeminal foramen are present. The frontal is distinguished dorsally and lacks contact with palatine. The transverse fronto-nasal suture on the roof of the skull is one of the primitive skull morphologies presented in this group. A deeply concave occipital plate is present and overhung by the occipital ridges. [1] [2]

The coronoid process in the dentary is highly mature. The overall angle of the dentary is slightly prominent, but the lateral crest on the right side is low. While the angular in lateral view is well-developed as well as concave laterally. The right reflected lamina has a sturdy strong base preserved in the holotype specimen.

Dentition

Unfortunately, almost all dentition in the holotype was damaged by grinding. Based on the roots of upper dentition, there appear to have four incisors, one canine, and roughly six or seven postcanines. Eight teeth are present in the dentary. Only a few crowns are preserved, which are four upper right postcanines and one lower postcanine. Compared to the postcanines, the smooth canine exhibits some faint longitudinal striations and is relatively large. [1] [2] Having simple first and second postcanine with other groups, such as the Progalesaurus and Galesaurus , Platycraniellus’s dentition exhibits a prominent curved tip with a convex front edge and a solitary cusp at the back. [5]

Postcranial

Apart from the skull, a small portion of the humerus is preserved and attached to the skull, which is the diaphysis and bottom part of the bone. Therefore, only the dorsal view of the element can be described. The deltopectoral crest is clearly defined and perpendicular to the long axis of the bone. The bottom part of the bone is notably wide, with a laterally expanded entepicondyle and a trochlea that create a triangular groove. Visible striations and scars infer the muscle attachment points on both epicondyles. A large entepicondylar foramen can be observed in this specimen. [1] [2]

Classification

Platycraniellus is the sister group of Eucynodontia and belongs to the Epicynodontia clade, which is a subdivision of the larger Cynodontia clade. Thrinaxodon is placed as the successive outgroup of these two groups. Notably, the Cynodontia clade, which Platycraniellus is a member of, was crucial in the evolution of all mammals, including Morganucodon . Cynodontia is considered the third radiation of synapsids and includes mammals as its living member. [1]

Cynodontia

Procynosuchus

Dvinia

Epicynodontia

Cynosaurus

Galesaurus

Progalesaurus

Thrinaxodon

Platycraniellus

Eucynodontia

Cynognathia

Probainognathia

Paleobiology

Lifestyle

The masseteric fossa on the dentary preserved in Platycraniellus [1] represents higher bite force since this feature allows more masseteric muscle attaches to the lower jaw and provides greater strength for biting, chewing, or crushing. [6] [7] This feature also allows more efficient and powerful jaw movements. [8] Together with the multi-cusps dentition, Platycraniellus is suggested to be a carnivore, a predominantly meat-eating animal similar to Thrinaxodon.

Metabolism

The complete osseous secondary palate which divides the nasal cavity from the rest of the mouth would have given Platycraniellus the ability to breathe while processing food at the same time. [1] This feature allows Platycraniellus to maximize their time for processing food, reduce digestion time, and eventually gain more energy for mobile activity. Therefore, Platycraniellus is suggested to have a highly mobile lifestyle which required an active metabolic rate. [9]

Based on the phylogeny and the close relationship with Thrinaxodon , Platycraniellus potentially contains a diaphragm due to the separation of dorsal vertebrae into thoracic and lumbar regions seen in Thrinaxodon. [10] The diaphragm would allow Platycraniellus to overcome Carrier's constraint, whereby reptiles can’t breathe while running. This adaptation could support high-speed movements which required a high metabolic rate as well. [9] [11] Therefore, considering both cranial and postcranial morphologies, Platycraniellus probably is an endotherm.

Paleoenvironment

The Lystrosaurus Assemblage Zone is named after the abundance of L. declivis and L. murrayi fossil records, two relatively small-sized dicynodonts, including the Palingkloof member of the Upper portion of the Balfour Formation. This biozone is a significant biozone that contains evidence of the survival and recovery from the end-Permian mass extinction (EPME) and marks the Permian-Triassic boundary with the Daptocephalus Assemblage Zone underneath. [12]

This boundary is determined by a change in the sedimentary rock types, indicating a shift in the fluvial environment. The Daptocephalus Assemblage Zone has meandering, high-sinuosity river channels made up of greenish-gray siltstones and mudstones. [13] [14] [15]  While the Palingkloof Member shows meandering river channels in reddish-brown and maroon-colored rocks, indicating arid and warm conditions. [16] [17] The overlying Katberg Formation has braided, low-sinuosity river channels composed of coarse-grained sandstones interspersed with reddish-brown siltstones and mudstones. [17] [13] [12] The dominance of sandstones in the Lystrosaurus Assemblage Zone suggests a more arid climate with shallow, braided rivers that seasonally dried up and frequently flooded their banks, resulting in the presence of crevasse-splays.

There is also evidence of erosion and die-offs of plant ecosystems, indicated by conglomerates and a gap in coal deposits. Mudstone and siltstone outcrops are less common, mainly found in the lower sections of the Palingkloof Member and in the uppermost section of the Burgersdorp Formation, and nodule conglomerates comprising pedogenic nodules and intrabasinal clasts are also present. [18] [19]

Paleoecology

The Lystrosaurus Assemblage Zone contains a variety of vertebrates, ranging from amphibians, archosauromorphs, therocephalians, eosuchians, to cynodonts. Based on the abundance of fossil records in each group, the calculation appeals to an irregular ratio between herbivores and carnivores. As the general trend infers an overall increase in the abundance of prey relative to the predators from Eodicynodon to Lystrosaurus Assemblage Zone. This disequilibrium is thought to be an environmental response to the temperature increase. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Cynodont</span> Clade of therapsids

Cynodonts are eutheriodont therapsids belonging to the clade Cynodontia that first appeared in the Late Permian, and extensively diversified after the Permian–Triassic extinction event. Cynodonts occupied a variety of ecological niches, both as carnivores and as herbivores. Mammals are cynodonts, as are their extinct ancestors and close relatives (Mammaliaformes), having evolved from advanced probainognathian cynodonts during the Late Triassic. All other cynodont lines went extinct, with the last known non-mammaliaform cynodont group, the Tritylodontidae, having its youngest records in the Early Cretaceous.

<i>Cynognathus</i> Extinct genus of cynodonts

Cynognathus is an extinct genus of large-bodied cynodontian therapsids that lived in the Middle Triassic. It is known from a single species, Cynognathus crateronotus. Cynognathus was a predator closely related to mammals and had a southern hemispheric distribution. Fossils have so far been recovered from South Africa, Argentina, Antarctica, and Namibia.

<i>Thrinaxodon</i> Extinct genus of cynodonts of Early Triassic South Africa

Thrinaxodon is an extinct genus of cynodonts, including the species T. liorhinus which lived in what are now South Africa and Antarctica during the 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.

<i>Galesaurus</i> Extinct genus of cynodonts from the Triassic of South Africa

Galesaurus is an extinct genus of carnivorous cynodont therapsid that lived between the Induan and the Olenekian stages of the Early Triassic in what is now South Africa. It was incorrectly classified as a dinosaur by Sir Richard Owen in 1859.

<i>Ericiolacerta</i> Extinct genus of therapsid from the #REDIRECT early Triassic

Ericiolacerta is an extinct genus of small therocephalian therapsids from the early Triassic of South Africa and Antarctica. Ericiolacerta, meaning "hedgehog lizard", was named by D.M.S. Watson in 1931. The species E. parva is known from the holotype specimen which consists of a nearly complete skeleton found in the Lystrosaurus Assemblage Zone within the Katberg Formation of the Beaufort Group in South Africa, and from a partial jaw found in the Lower Triassic Fremouw Formation in Antarctica. Ericiolacerta was around 20 centimetres (7.9 in) in length, with long limbs and relatively small teeth. It probably ate insects and other small invertebrates. The therocephalians – therapsids with mammal-like heads – were abundant in Permian times, but only a few made it into the Triassic. Ericiolacerta was one of those. It is possible that they gave rise to the cynodonts, the only therapsid group to survive into post-Triassic times. Cynodonts gave rise to mammals.

<i>Daptocephalus</i> Assemblage Zone

The Daptocephalus 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 upper Teekloof Formation west of 24°E, the majority of the Balfour Formation east of 24°E, and the Normandien Formation in the north. It has numerous localities which are spread out from Colesberg in the Northern Cape, Graaff-Reniet to Mthatha in the Eastern Cape, and from Bloemfontein to Harrismith in the Free State. The Daptocephalus Assemblage Zone is one of eight biozones found in the Beaufort Group and is considered Late Permian (Lopingian) in age. Its contact with the overlying Lystrosaurus Assemblage Zone marks the Permian-Triassic boundary.

<i>Lystrosaurus</i> Assemblage Zone

The Lystrosaurus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the upper Adelaide and lower Tarkastad Subgroups of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. This biozone has outcrops in the south central Eastern Cape and in the southern and northeastern Free State. The Lystrosaurus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Early Triassic in age.

<i>Tropidostoma</i> Assemblage Zone

The Tropidostoma Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the lower Teekloof 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 240 metres (790 ft), occur from east of Sutherland through to Beaufort West and Victoria West, to areas south of Graaff-Reinet. Its northernmost exposures occur west/north-west of Colesberg. The Tropidostoma Assemblage Zone is the fourth biozone of the Beaufort Group.

<i>Moschorhinus</i> Genus of synapsid from late Permian and early Triassic South Africa

Moschorhinus is an extinct genus of therocephalian synapsid in the family Akidnognathidae with only one species: M. kitchingi, which has been found in the Late Permian to Early Triassic of the South African Karoo Supergroup. It was a large carnivorous therapsid, reaching 1.5 m (4.9 ft) in total body length with the largest skull comparable to that of a lion in size, and had a broad, blunt snout which bore long, straight canines.

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

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.

<i>Broomistega</i> Extinct genus of temnospondyl amphibian from the early Triassic

Broomistega is an extinct genus of temnospondyl amphibian in the family Rhinesuchidae. It is known from one species, Broomistega putterilli, which was renamed in 2000 from Lydekkerina putterilli Broom 1930. Fossils are known from the Early Triassic Lystrosaurus Assemblage Zone of the Beaufort Group in the Karoo Basin of present-day South Africa, a region that had been an enclave of Gondwana. Specimens of B. putterilli were once thought to represent young individuals of another larger rhinesuchid such as Uranocentrodon, but the species is now regarded as a paedomorphic taxon, possessing the features of juvenile rhinesuchids into adulthood.

Cynosaurus is an extinct genus of cynodonts. Remains have been found from the Dicynodon Assemblage Zone in South Africa. Cynosaurus was first described by Richard Owen in 1876 as Cynosuchus suppostus. Cynosaurus has been found in the late Permian period. Cyno- is derived from the Greek word kyon for dog and –sauros in Greek meaning lizard.

<i>Progalesaurus</i> Extinct genus of cynodonts

Progalesaurus is an extinct genus of galesaurid cynodont from the early Triassic. Progalesaurus is known from a single fossil of the species Progalesaurus lootsbergensis, found in the Lystrosaurus Assemblage Zone of the Balfour Formation. Close relatives of Progalesaurus, other galesaurids, include Galesaurus and Cynosaurus. Galesaurids appeared just before the Permian-Triassic extinction event, and disappeared from the fossil record in the Middle-Triassic.

<i>Lumkuia</i> Extinct genus of cynodonts

Lumkuia is an extinct genus of cynodonts, fossils of which have been found in the Cynognathus Assemblage Zone of the Beaufort Group in the South African Karoo Basin that date back to the early Middle Triassic. It contains a single species, Lumkuia fuzzi, which was named in 2001 on the basis of the holotype specimen BP/1/2669, which can now be found at the Bernard Price Institute in Johannesburg, South Africa. The genus has been placed in its own family, Lumkuiidae. Lumkuia is not as common as other cynodonts from the same locality such as Diademodon and Trirachodon.

<i>Langbergia</i> Extinct genus of cynodonts

Langbergia is an extinct genus of trirachodontid cynodont from the Early Triassic of South Africa. The type and only species L. modisei was named in 2006 after the farm where the holotype was found, Langberg 566. Langbergia was found in the Burgersdorp Formation in the Beaufort Group, a part of the Cynognathus Assemblage Zone. The closely related trirachodontids Trirachodon and Cricodon were found in the same area.

<i>Abdalodon</i> Extinct genus of cynodonts

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.

<span class="mw-page-title-main">Balfour Formation</span> Geological formation in the Beaufort Group of South Africa

The Balfour Formation is a geological formation that is found in the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup in South Africa. The Balfour Formation is the uppermost formation of the Adelaide Subgroup which contains all the Late Permian-aged biozones of the Beaufort Group. Outcrops and exposures of the Balfour Formation are found from east of 24 degrees in the highest mountainous escarpments between Beaufort West and Fraserburg, but most notably in the Winterberg and Sneeuberg mountain ranges near Cradock, the Baviaanskloof river valley, Graaff-Reniet and Nieu Bethesda in the Eastern Cape, and in the southern Free State province.

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

Thliptosaurus is an extinct genus of small kingoriid dicynodont from the latest Permian period of the Karoo Basin in KwaZulu-Natal, South Africa. It contains the type and only known species T. imperforatus. Thliptosaurus is from the upper Daptocephalus Assemblage Zone, making it one of the youngest Permian dicynodonts known, living just prior to the Permian mass extinction. It also represents one of the few small bodied dicynodonts to exist at this time, when most other dicynodonts had large body sizes and many small dicynodonts had gone extinct. The unexpected discovery of Thliptosaurus in a region of the Karoo outside of the historically sampled localities suggests that it may have been part of an endemic local fauna not found in these historic sites. Such under-sampled localities may contain 'hidden diversities' of Permian faunas that are unknown from traditional samples. Thliptosaurus is also unusual for dicynodonts as it lacks a pineal foramen, suggesting that it played a much less important role in thermoregulation than it did for other dicynodonts.

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

Ufudocyclops is an extinct genus of stahleckeriid dicynodont from the Middle Triassic of South Africa. It was found in the Burgersdorp Formation, part of the uppermost Cynognathus Assemblage Zone of the Beaufort Group in the Karoo Basin. The type and only known species is U. mukanelai. It was a large, beaked herbivore like other Triassic dicynodonts, lacking tusks, and is mostly characterised by unique features of the skull. It is known from three specimens, two of which were previously referred to the Tanzanian dicynodont Angonisaurus. The separation of Ufudocyclops from Angonisaurus indicates that the Middle Triassic fauna of the Beaufort Group in South Africa was not part of a larger shared fauna with those of the Manda Beds in Tanzania, as was previously supposed, and suggests that they were separated as more localised faunas, possibly by geographic barriers or in time. Ufudocyclops then would have been a unique part of the uppermost Cynognathus Assemblage Zone in South Africa. It is also the oldest known member of the family Stahleckeriidae, and implies that the family was already diversifying in the Middle Triassic alongside other kannemeyeriiforms, not just in the Late Triassic after other families died out.

Vetusodon is an extinct genus of cynodonts belonging to the clade Epicynodontia. It contains one species, Vetusodon elikhulu, which is known from four specimens found in the Late Permian Daptocephalus Assemblage Zone of South Africa. With a skull length of about 18 centimetres (7.1 in), Vetusodon is the largest known cynodont from the Permian. Through convergent evolution, it possessed several unusual features reminiscent of the contemporary therocephalian Moschorhinus, including broad, robust jaws, large incisors and canines, and small, single-cusped postcanine teeth.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Abdala, Fernando (2007). "Redescription of Platycraniellus Elegans (therapsida, Cynodontia) from the Lower Triassic of South Africa, and the Cladistic Relationships of Eutheriodonts". Palaeontology. 50 (3): 591–618. Bibcode:2007Palgy..50..591A. doi: 10.1111/j.1475-4983.2007.00646.x . S2CID   83999660.
  2. 1 2 3 4 5 Haughton, Sidney Henry (1924). "On cynodontia from the middle Beaufort beds of Harrismith, Orange Free State". Annals of the Transvaal Museum. 11 (1): 74–92. doi:10.1144/gsl.jgs.1924.080.01-04.03. S2CID   129976752.
  3. 1 2 Hopson, J.A.; Kitching, J.W. (1972). "A revised classification of cynodonts (Reptilia; Therapsida)". University of the Witwatersrand.
  4. 1 2 Brink, A.S. (1954). "Note on a new Platycraniellus skull". Navorsinge van die Nasionale Museum: Researches of the National Museum. 1 (5): 127. doi: 10.5962/bhl.part.12338 .
  5. ↑ Van den Brandt, M.; Abdala, N.F. (2018). "Cranial morphology and phylogenetic analysis of Cynosaurus suppostus (Therapsida, Cynodontia) from the Upper Permian of the Karoo Basin, South Africa". Palaeontologia Africana. 52: 201–221. hdl:10539/24254.
  6. ↑ Walker, W.F. Jr. (1987). "Functional Anatomy of the Vertebrates. An Evolutionary Perspective". Philadelphia: Saunders College Publishing.
  7. ↑ Abdala, F.; Damiani, R. (2004). "Early development of the mammalian superficial masseter muscle in cynodonts". Palaeontologica Africana. 40: 23–29.
  8. ↑ Crompton, A.W.; Luo, Z. (1993). "Relationships of the Liassic mammals Sinoconodon, Morganucodon oehleri, and Dinnetherium". Mammal Phylogeny: Mesozoic Differentiation, Multituberculates, Monotremes, Early Therians, and Marsupials: 30–44.
  9. 1 2 Benton, M.J. (2021). "The origin of endothermy in synapsids and archosaurs and arms races in the Triassic". Gondwana Research. 100: 261–289. Bibcode:2021GondR.100..261B. doi: 10.1016/j.gr.2020.08.003 . S2CID   222247711.
  10. 1 2 Norihiro, O.; Takeshi, S.; Tomomi, S.; Hidenori, N. (2010). "Emergence of mammals by emergency: exaptation". Genes to Cells. 15.
  11. ↑ Hillenius, W.J.; Ruben, J.A. (2004). "The evolution of endothermy in terrestrial vertebrates: Who? When? Why?". Physiological and Biochemical Zoology. 77 (6): 1019–1042. doi:10.1086/425185. PMID   15674773. S2CID   29300018.
  12. 1 2 Botha, J.; Smith, R.M.H. (2020). "Biostratigraphy of the Lystrosaurus declivis Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa". South African Journal of Geology. 123 (2): 207–216. Bibcode:2020SAJG..123..207B. doi:10.25131/sajg.123.0015. S2CID   225856179.
  13. 1 2 Viglietti, P.A.; Smith, R.M.; Rubidge, B.S. (2018). "Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction". Journal of African Earth Sciences. 138: 102–111. Bibcode:2018JAfES.138..102V. doi:10.1016/j.jafrearsci.2017.11.010.
  14. ↑ Viglietti, Pia A.; Smith, Roger M.H.; Angielczyk, Kenneth D.; Kammerer, Christian F.; Fröbisch, Jörg; Rubidge, Bruce S. (January 2016). "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. ISSN   1464-343X.
  15. ↑ Smith, R.M.H. (August 1995). "Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions". Palaeogeography, Palaeoclimatology, Palaeoecology. 117 (1–2): 81–104. Bibcode:1995PPP...117...81S. doi:10.1016/0031-0182(94)00119-s. ISSN   0031-0182.
  16. ↑ Hiller, N.; Stavrakis, N. (1984). "Permo-Triassic fluvial systems in the southeastern Karoo basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 45 (1): 1–21. Bibcode:1984PPP....45....1H. doi:10.1016/0031-0182(84)90106-8.
  17. 1 2 Viglietti, P.A.; Smith, R.M.; Compton, J.S. (2013). "Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 392: 9–21. Bibcode:2013PPP...392....9V. doi:10.1016/j.palaeo.2013.08.015.
  18. ↑ Smith, R.M.; Both-Brink, J. (2014). "Anatomy of a mass extinction: sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 396: 99–118. Bibcode:2014PPP...396...99S. doi:10.1016/j.palaeo.2014.01.002.
  19. ↑ Smith, R.M. (1995). "Smith, R. M. (1995). Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions". Palaeogeography, Palaeoclimatology, Palaeoecology. 117 (1–2): 81–104. Bibcode:1995PPP...117...81S. doi:10.1016/0031-0182(94)00119-S.
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