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62-548: † Dicynodon schroederi Toerien, 1953 † Broilius antjiesfonteinensis Toerien, 1953 Robertia is an extinct genus of small herbivorous dicynodonts from the Middle to Late Permian of South Africa, between 260 and 265 million years ago. It is a monospecific genus, consisting of the type-species R. broomiana, which was classified by Lieuwe Dirk Boonstra in 1948 and named in honor of Robert Broom for his study of South African mammal-like reptiles. Robertia had characteristic caniniform tusks and few, small teeth on

124-702: A foreland basin that was being formed from the rising of the Gondwanide mountains in the south. The Gondwanides were the result of crustal uplift that had previously begun to take course due to tectonic activity. The pressure of the growing Gondwanides mountain chain caused the formation of the Karoo Basin where the deposits of the Pristerognathus Assemblage zone, and all other succeeding assemblage zone deposits, were deposited over tens of millions of years. Vertebrate fossils are most commonly found in

186-447: A backward-angled orientation for clearance of the abdomen from the ground. Robertia had either two or three sacral vertebrae. The vertebral column was flexible, the pre-zygapophyses being flat and wide and articulating horizontally with the post-zygapophyses. The tail is only slightly muscular and is about one-eighth the length of the body. Robertia and other dicynodonts had a particularly specialized jaw. A forward-backward motion of

248-527: A characteristic intertemporal region and pineal foramen located in the pre-parietal. Reexamining over a hundred skulls in the South African Museum designated Dicynodon jouberti , L.D. Boonstra separated out new taxa that fell outside the group. Robertia was characterized by Boonstra in 1948. The fossil specimens were discovered in the lower part of the Tapinocephalus Zone in the west part of

310-568: A dicynodont, and the name Cryptodontia is no longer used. Thomas Henry Huxley revised Owen's Dicynodontia as an order that included Dicynodon and Oudenodon . Dicynodontia was later ranked as a suborder or infraorder with the larger group Anomodontia, which is classified as an order. The ranking of Dicynodontia has varied in recent studies, with Ivakhnenko (2008) considering it a suborder, Ivanchnenko (2008) considering it an infraorder, and Kurkin (2010) considering it an order. Many higher taxa, including infraorders and families, have been erected as

372-458: A large mammal, probably a diprotodontid . With the decline and extinction of the kannemeyerids, there were to be no more dominant large synapsid herbivores until the middle Paleocene epoch (60 Ma) when mammals , distant descendants of cynodonts , began to diversify after the extinction of the non-avian dinosaurs. Dicynodontia was originally named by the English paleontologist Richard Owen . It

434-524: A large variety of ecotypes, including large, medium-sized, and small herbivores and short-limbed mole-like burrowers. Only four lineages are known to have survived the Great Dying ; the first three represented with a single genus each: Myosaurus , Kombuisia , and Lystrosaurus , the latter being the most common and widespread herbivores of the Induan (earliest Triassic ). None of these survived long into

496-711: A means of classifying the large number of dicynodont species. Cluver and King (1983) recognised several main groups within Dicynodontia, including Eodicynodontia (containing only Eodicynodon ), Endothiodontia (containing only Endothiodontidae ), Pristerodontia ( Pristerodontidae , Cryptodontidae , Aulacephalodontidae , Dicynodontidae , Lystrosauridae , and Kannemeyeriidae ), Kingoriamorpha (containing only Kingoriidae ), Diictodontia ( Diictodontidae , Robertiidae , Cistecephalidae , Emydopidae and Myosauridae ), and Venyukoviamorpha . Most of these taxa are no longer considered valid. Kammerer and Angielczyk (2009) suggested that

558-422: A narrow groove along its midline runs between the nasals. Robertia has two, large caniniform tusks and about three, small irregularly placed maxillary teeth posteromedial to the tusks. The anterior edge of the tusks also have a sharp edge. Anteromedial to the tusks, the maxilla bears a sharp edge. A sharp palatal notch and a maxillary notch are located behind the rear edge of the maxilla and upper anterior region of

620-471: A new genus, “Bidental.” Skull specimens were referred to Sir Richard Owen at the British Museum of Natural History , who placed them under the designation Dicynodon in the 1840s. Comparable specimens, but without tusks were placed in a new genus Oudenodon. As more of these mammal-like specimens were discovered during the early twentieth century, hundreds of species began to be described and amassed under

682-457: A pair of enlarged maxillary caniniform teeth, analogous to the tusks present in some living mammals. In the earliest genera, they were merely enlarged teeth, but in later forms they independently evolved into ever-growing teeth like mammal tusks multiple times. In some dicynodonts, the presence of tusks has been suggested to be sexually dimorphic . Some dicynodonts such as Stahleckeria lacked true tusks and instead bore tusk-like extensions on

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744-612: A pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typically toothless beak, unique amongst all synapsids . Dicynodonts first appeared in Southern Pangaea during the mid-Permian , ca. 270–260 million years ago, and became globally distributed and the dominant herbivorous animals in the Late Permian , ca. 260–252 Mya. They were devastated by the end-Permian Extinction that wiped out most other therapsids ca. 252 Mya. They rebounded during

806-458: A skull in 2003. This suggested to indicate that dicynodonts survived into the Cretaceous in southern Gondwana . The dicynodont affinity of these specimens was questioned (including a proposal that they belonged to a baurusuchian crocodyliform by Agnolin et al. in 2010), and in 2019 Knutsen and Oerlemans considered this fossil to be of Plio - Pleistocene age, and reinterpreted it as a fossil of

868-485: A small, fossorial dicynodont whose fossils are especially common in this biozone. The first fossils to be found in the Beaufort Group rocks that encompass the current eight biozones were discovered by Andrew Geddes Bain in 1856. However, it was not until 1892 that it was observed that the geological strata of the Beaufort Group could be differentiated based on their fossil taxa . The initial undertaking

930-504: Is considered to be Middle Permian ( Guadalupian ) in age. The rocks of the Pristerognathus Assemblage Zone are similar to the underlying Tapinocephalus Assemblage Zone although is dominated by multistory sandstone deposits. The sandstones are interspaced with silt -rich greenish-grey mudstones and subordinate reddish-brown mudstone layers. Calcareous nodules , which weather out brown, are often found in

992-577: Is known from the La Belle France cave in South Africa , often conflated with the Dingonek . It may be based on dicynodont fossils. Pristerognathus Assemblage Zone The name of the biozone refers to Pristerognathus polyodon , a medium-sized carnivorous therocephalian therapsid . It is characterized by the presence of this therocephalian species in association with Diictodon feliceps ,

1054-426: Is more pronounced on the dorsal surface and is not offset from the main bone shaft. Well-developed regions of attachment for muscles such as the pubo-ischio-femoralis externus, ventral adductor, femorotibialis, and gastrocnemius provide support for the sprawling gait. The feet also have claws, which are rounder than those of the hand and have a dorsal ridge. The thoracic and lumbar ribs are long and straight, suggesting

1116-497: Is suggested that they preferred stems and rhizomes over leafy vegetation. Their claws may have been utilized for tearing or digging in the search for food. Different times of the year may have called for different selections of food sources in the Permian. It has been suggested that the less developed masticatory system may have led to Robertia ' s selection of certain foods and may have limited its ability to persist in comparison to

1178-459: The Beaufort Group . In the 1950s, Toerien worked to further characterize and refine the species under the Dicynodon designation based on criteria beyond the features of the dorsal skull. Toerien specifically used the presence of a small palatine bone to further classify species. In 1953, he defined the species Dicynodon schroederi , which was later said to be synonymous with Diictodon feliceps in

1240-468: The Dicynodon designation . In 1954, Haughton and Brink alone uncovered 54 dicynodont genera in the Karoo Basin and characterized 111 species under the single genus Dicynodon . Poor extraction and preparation of the Dicynodon type fossils and the minute differences that were used to distinguish its species contributed to the problem. At this point, taxa were described through dorsal or lateral sketches of

1302-475: The Pristerognathus Assemblage Zone. This inconsistency is due to the fact that Rubidge and Angielczyk misidentified Eosimops in this range as Robertia. Robertia has not been identified in other Mid-Permian continental deposits. Scarcity of fossils in the stratigraphic levels before the appearance of Robertia and its close relatives Eosimpos and Diictodon prevents accurate delineation of where members of each genus begin relative to each other. Dipping in

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1364-472: The Triassic but died out towards the end of that period. They were the most successful and diverse of the non-mammalian therapsids, with over 70 genera known, varying from rat-sized burrowers to elephant-sized browsers . The dicynodont skull is highly specialised, light but strong, with the synapsid temporal openings at the rear of the skull greatly enlarged to accommodate larger jaw muscles. The front of

1426-462: The alluvial plains . It is thought that the paleoenvironment of the Beaufort Karoo consisted of large rivers around 350 meters wide and 11 meters deep running into a system of lakes that were no more than 50 meters deep. Late Permian South Africa was likely warm to hot, with average temperatures ranging from 16 to 20 °C and experienced seasonal rainfall, about 50 to 70 cm yearly, disrupting

1488-414: The biarmosuchian Hipposaurus boonstrai are likewise found including some gorgonopsid species. Other dicynodont species found include Endothiodon uniseries and Pristerodon mackayi . Finally, fossils of temnospondyl amphibians such as of Rhinesuchus whaitsi , the fishes Namaichthys and Atherstonia , invertebrate trackways , burrows, and feeding trails such as of Planolites and

1550-399: The mudstone deposits of the Pristerognathus Assemblage Zone, especially within the calcareous nodules . This biozone is characterized by the presence of Pristerognathus polyodon and its other subspecies Pristerognathus baini and Pristerognathus vanderbyli . Pristerognathus fossils are usually found associated with those of Diictodon . The fossils of both these taxa are

1612-412: The mudstone layers. Pinkish chert bands are found in the lowermost mudstone deposits of this biozone. The Pristerognathus Assemblage Zone is also known for containing uranium deposits. The presence of the chert band confirms that there was volcanic activity taking place during the time the rock sediments were deposited. The rocks of the lower Pristerognathus Assemblage Zone were deposited at

1674-490: The 1980s. However, more recent characterization has recognized the species as Robertia broomiana, based on the specimen’s wide intertemporal bar, extensive exposure of the parietals, a narrow postorbital bar, and the presence of postcanine teeth. The South African Karoo Basin expands to about 300,000 km and contains the 145,000 km Beaufort Group of the Late Permian and Early Triassic. The Abrahamskraal Formation of

1736-681: The Beaufort group consists of the Eodicynodon , Tapinocephalus , and Pristerognathus Assemblage Zones , all of which are characterized by the prevalence and high diversity of dicynodonts. Robertia is found in the 1441- meter-thick Tapinocephalus Assemblage Zone in the northern region of the Abrahamskraal Formation. According to Jirah, Robertia ’s range is 200 m below the Teekloof Formation; however, other sources claimed it spans into

1798-469: The British Museum . By this time, many more dicynodonts had been described. In 1859, another important species called Ptychognathus declivis was named from South Africa. In the same year, Owen named the group Dicynodontia. In his Descriptive and Illustrated Catalogue , Owen honored Bain by erecting Bidentalia as a replacement name for his Dicynodontia. The name Bidentalia quickly fell out of use in

1860-575: The English paleontologist Richard Owen named two species of dicynodonts from South Africa: Dicynodon lacerticeps and Dicynodon bainii . Since Bain was preoccupied with the Corps of Royal Engineers, he wanted Owen to describe his fossils more extensively. Owen did not publish a description until 1876 in his Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the Collection of

1922-454: The Permian extinction. A 2024 paper posited that rock art of a superficially walrus-like imaginary creature with downcurved tusks created by the San people of South Africa prior to 1835 may have been partly inspired by fossil dicynodont skulls which erode out of rocks in the area. Dicynodonts have been known to science since the mid-1800s. The South African geologist Andrew Geddes Bain gave

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1984-826: The Triassic. The fourth group was the Kannemeyeriiformes , the only dicynodonts who diversified during the Triassic. These stocky, pig- to ox-sized animals were the most abundant herbivores worldwide from the Olenekian to the Ladinian age. By the Carnian they had been supplanted by traversodont cynodonts and rhynchosaur reptiles. During the Norian (middle of the Late Triassic), perhaps due to increasing aridity, they drastically declined, and

2046-767: The bones are so highly vascularised that they exhibit higher channel densities than most other therapsids. Yet, studies on Late Triassic dicynodont coprolites paradoxically showcase digestive patterns more typical of animals with slow metabolisms. More recently, the discovery of hair remnants in Permian coprolites possibly vindicates the status of dicynodonts as endothermic animals. As these coprolites come from carnivorous species and digested dicynodont bones are abundant, it has been suggested that at least some of these hair remnants come from dicynodont prey. A new study using chemical analysis seemed to suggest that cynodonts and dicynodonts both developed warm blood independently before

2108-535: The boundary of the Tapinocephalus Assemblage Zone , and the extra 300m of rock was subsequently restored to the underlying Tapinocephalus Assemblage Zone . The Pristerognathus Assemblage Zone correlates with the upper Abrahamskraal Formation , the lowermost Teekloof Formation west of 24°E and to the Middleton Formation east of 24°E, Adelaide Subgroup of the Beaufort Group . This biozone

2170-436: The dentary. Robertia is described as “solidly built, barrel-bodied animals.” It had developed postural limb musculature, a trochanter on the femur, diminished pre-acetabular iliac expansion relative to the post-acetabular, an anteriorly expanded pubis, and an abducted femur, which differentiate it from Diictodon. The radius and ulna are thin and about three-quarters the length of the humerus, articulating at right angles to

2232-512: The end of the middle Permian (end-Guadalupian) extinction event, which is currently thought to have been caused by the eruption of the Emeishan Large Igneous Province. The depositional environment of the Pristerognathus Assemblage Zone was likewise similar to the Tapinocephalus Assemblage Zone , having been formed by sedimentary material being deposited by vast, fluvial plains. These fluvial plains flowed northwards from

2294-580: The first description of dicynodonts in 1845. At the time, Bain was a supervisor for the construction of military roads under the Corps of Royal Engineers and had found many reptilian fossils during his surveys of South Africa. Bain described these fossils in an 1845 letter published in Transactions of the Geological Society of London , calling them "bidentals" for their two prominent tusks. In that same year,

2356-533: The following years, replaced by popularity of Owen's Dicynodontia. Dicynodonts first appeared during the Middle Permian in the Southern Hemisphere, with South Africa being the centre of their known diversity, and underwent a rapid evolutionary radiation , becoming globally distributed and amongst the most successful and abundant land vertebrates during the Late Permian . During this time, they included

2418-415: The herbivorous dicynodonts of the time, turning them towards digging for rhizomes below the ground surface. Robertia ’s skull reached a length of 130 mm, large compared to other small dicynodonts. Some specimens have minor grooves on the facial surface. It has a characteristic relatively wide intertemporal region, which exposes the parietal bones in the midline. A low dorsal ridge of the premaxilla with

2480-463: The humerus are expanded. The head of this bone faces slightly medially and dorsally. Robertia has blunt claws on the end of each phalanx, with a protuberance on the undersides. On one fossil specimen, the metacarpal and the phalanges of the longest finger are the same length as the radius. The S-shaped femur similarly articulates in a right-angled, sprawling position. All dicynodonts had a parasagittal hindlimb posture, besides Robertia. The femur head

2542-463: The humerus. The antebrachium was also positioned at a right angle relative to the humerus, indicating a sprawling posture of the forelimb. This suggests the necessity of strong postural muscles, which would prevent collapse under the weight of gravity. The appropriate attachment sites for muscles such as the ventral adductor, biceps, brachialis, coracobrachialis, and pectoralis are accordingly well developed. Characteristic of other dicynodonts, both ends of

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2604-437: The jaws and the anterior notch aligned the vegetation in the mouth, and as the lower jaw moves backward, it pulled the plant matter past the caniniform tusks, cutting it into bite-size pieces. The food was further processed by the dentary blades and the edges of the tusks and crushed on the palatine pad. The horned beak may have allowed small dicynodonts such as Robertia to pick out individual leaves, seeds, and buds, however it

2666-468: The late 1970s. Initially the biozone included the upper 300m of the underlying Tapinocephalus Assemblage Zone due to the disappearance of Dinocephalian fossils in those rock deposits and had been named the Pristerognathus - Diictodon Assemblage Zone. After further research on the rocks of the middle Permian, it was understood that the disappearance of the dinocephalians was not an indication of

2728-444: The lower jaw allowed them to effectively breakdown vegetation. Robertia ’s small, fragile teeth may not have played a direct role in chewing, despite their ability to run along the dentary table. Shredding from movement of the dentary along the caniniform tusks and up past the premaxilla and maxilla occurred as the lower jaw motioned propalinally. The sharp blades of the dentary and along the tusks provide cutting action. The front end of

2790-566: The maxillary and dentary table. Its beak and the propalinal movement of the jaw, as with other dicynodonts, allowed for efficient cutting of plant matter. The solid, barrel-bodied creatures had a sprawling stance with a flexible backbone, which likely gave them a lizard-like appearance as they moved. They were about 15 cm in length. Robertia is a member of the family Pylaecephalidae , which includes other small dicynodont therapsids with tusks such as Diictodon , Prosictodon , and Eosimops . Anomodonts and dicynodont subclade members were

2852-414: The more sophisticated systems of groups such as Emydops and Pristerodon , which may have been more generalist feeders. Robertia had a sprawling gait. The position and rounding of the dorsal articulation area of the femur allowed for a longer stride compared to earlier sprawling animals. The pectoral girdle muscles had a postural function rather than locomotory function and thus provided less thrust than

2914-591: The most common species of the Permian and Triassic periods and were the first fossil vertebrates uncovered in the South African Karoo. The discovery of these animals was especially important as they exhibited mammal-like traits outside of the Mammalia taxon. Keen fossil collector and amateur paleontologist A. G. Bain found the first anomodont in South Africa. Noticing the two prominent canines, he assigned it to

2976-458: The most commonly found; other fossil taxa are markedly more rare. Species diversity dropped off after the end-Guadalupian extinction , which is the reason that this biozone is lacking in species richness . Other taxa that have been found in this biozone include a couple pareiasaur species, namely Bradysaurus , the putative pantestudine Eunotosaurus africanus , and the varanopid pelycosaur Heleosaurus scholtzi . Fossils of

3038-400: The muscles of the hindlimb. The flexibility of the vertebrae allowed for extensive side to side movement as Robertia moved, similar to a modern lizard. Their long hands may have provided a platform of stability, however they may not have been wide enough for proper support. Robertia had a short tail, which may have helped with maneuverability at high speeds and over uneven ground. Robertia

3100-470: The problematic taxonomy and nomenclature of Dicynodontia and other groups results from the large number of conflicting studies and the tendency for invalid names to be mistakenly established. Below is a cladogram modified from Angielczyk et al. (2021): Nyaphulia Eodicynodon Colobodectes Lanthanostegus Pylaecephalidae Eumantellidae Brachyprosopus Endothiodontia Emydopoidea Bidentalia A horned serpent cave art

3162-539: The role of large herbivores was taken over by sauropodomorph dinosaurs. Fossils of an Asian elephant -sized dicynodont Lisowicia bojani discovered in Poland indicate that dicynodonts survived at least until the late Norian or earliest Rhaetian (latest Triassic); this animal was also the largest known dicynodont species. Six fragments of fossil bone discovered in Queensland , Australia, were interpreted as remains of

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3224-462: The same level as the tusks. The dentary shelf does not protrude as much as in Emydops , and the concave dentary tables hold five to six pointed teeth medially. Robertia is one of the pylaecephalids with the most dentary teeth, which occlude with the palatine pad (a ridged region posterolateral to the main secondary palate) upon jaw retraction. A beak is located anterior to the tusks and the outer side of

3286-640: The semi-arid climate. There would have been occasional flash-flooding. Along the Permian Karoo Basin riverbanks, the vegetation included woody deciduous Glossopteris and the bamboo-like Phyllotheca . The lowland areas likely gave rise to a variety of ferns, mosses, and lycopods . This would have formed the basis of Robertia ’s diet. There is some suggestion of the presence of stretches of savanna, but others doubt this, since ferns do not make up modern savannas. The region’s hot, semi-arid climate dependent on intermittent rainfall may have placed pressure on

3348-705: The side of the beak. The body is short, strong and barrel-shaped, with strong limbs. In large genera (such as Dinodontosaurus ) the hindlimbs were held erect, but the forelimbs bent at the elbow. Both the pectoral girdle and the ilium are large and strong. The tail is short. Pentasauropus dicynodont tracks suggest that dicynodonts had fleshy pads on their feet. Mummified skin from specimens of Lystrosaurus in South Africa have numerous raised bumps. Dicynodonts have long been suspected of being warm-blooded animals. Their bones are highly vascularised and possess Haversian canals , and their bodily proportions are conducive to heat preservation. In young specimens,

3410-428: The skull and the lower jaw are generally narrow and, in all but a number of primitive forms, toothless. Instead, the front of the mouth is equipped with a horny beak, as in turtles and ceratopsian dinosaurs . Food was processed by the retraction of the lower jaw when the mouth closed, producing a powerful shearing action, which would have enabled dicynodonts to cope with tough plant material. Dicynodonts typically had

3472-475: The skull, suture patterns, proportions of the skull, and notation of the presence or absence of teeth and tusks. Further studies examining the lower jaw, postcanine teeth, and other characteristics have reduced the large amount of dicynodont taxa into fewer, more valid genera. The new group Pylaecephalinae (later Pylaecephalidae), within which Robertia lies, was established in 1934. Species of this family contains those of Diictodon and its closest relatives, having

3534-440: The strata may have resulted in poor exposure of well defined divisional planes. In addition, many of the best-preserved specimens that can accurately be classified as Robertia were collected without precise location documentation. As a result, the range of Robertia may also extend further than is currently known. Robertia fossil specimens have been uncovered in mudstone and sandstone, which have been formed by river flow across

3596-524: The tusks, respectively. Whether the presence of tusks is a sexual dimorphism in Robertia is questioned, as the best preserved specimens all have tusks, but it is more difficult to determine if they are evident in the poorly preserved fossils. Some studies determined that tusks were variable in Robertia, however more recent accounts have stated they are consistently present across Robertia. The palatines are distinctive, forming an anterior gap and not meeting

3658-413: The vomers. Robertia has smaller palatines compared to close relative Pristerodon , but larger than the palatines of Emydops. The pterygoids are slightly curved and have fairly high, thin triangular-shaped flanges halfway down their length. The interpterygoid vacuities are longer and tear-drop shaped compared to other pylaecephalids. Robertia has a short secondary palate, with the choana anterior and at

3720-411: Was done by Harry Govier Seeley who subdivided the Beaufort Group into three biozones , which he named (from oldest to youngest): These proposed biozones Seeley named were subdivided further by Robert Broom between 1906 and 1909. Broom proposed the following biozones (from oldest to youngest): The Pristerognathus Assemblage Zone as it currently stands was defined by Keyser and Smith in

3782-419: Was erected as a family of the order Anomodontia and included the genera Dicynodon and Ptychognathus . Other groups of Anomodontia included Gnathodontia , which included Rhynchosaurus (now known to be an archosauromorph ) and Cryptodontia , which included Oudenodon . Cryptodonts were distinguished from dicynodonts from their absence of tusks. Although it lacks tusks, Oudenodon is now classified as

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3844-471: Was likely ectothermic . Robertia and its dicynodont relatives have a large pineal foramen on their skull, suggesting a light-sensitive pineal organ was used to track and take advantage of solar intensity cycles. Locating optimal temperatures would have helped in digestion. Dicynodont see " Taxonomy " Dicynodontia is an extinct clade of anomodonts , an extinct type of non-mammalian therapsid . Dicynodonts were herbivores that typically bore

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