''Anomocephalus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of primitive

anomodont Anomodontia is an extinct group of non-mammalian therapsids from the Permian and Triassic periods. By far the most speciose group are the dicynodonts, a clade of beaked, tusked herbivores. Anomodonts were very diverse during the Middle Pe ...

s and belongs to the clade

Anomocephaloidea Anomocephaloidea is a clade of Basal (phylogenetics), basal anomodont therapsids related to the dicynodonts known from what is now South Africa and Brazil during the Middle Permian. It includes only two species, ''Anomocephalus africanus'' (the c ...

. The name is said to be derived from the Greek word ''anomos'' meaning lawless and ''cephalos'' meaning head. The proper word for head in Greek is however κεφαλή (''kephalē'').Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie''. Oxford: Clarendon Press. It is primitive in that it retains a complete set of

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

in both jaws, in contrast to its descendants, the dicynodonts, whose dentition is reduced to only a single pair of tusks (and in many cases no teeth at all), with their jaws covered by a horny beak similar to that of a modern

tortoise Tortoises ( ) are reptiles of the family Testudinidae of the order Testudines (Latin for "tortoise"). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like o ...

. However, they are in no way closely related. Its discovery in 1999 from the earliest terrestrial rocks of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

(from Williston in the

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe Khoemana (also known as !Orakobab or Korana) word is a semidesert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its extent is ...

of the

Northern Cape Province The Northern Cape ( ; ; ) is the largest and most sparsely populated province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley. It includes the Kalahari Gemsbok National Park, part of the Kga ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

) has shown that this group of

herbivores A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

originated in

; not

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...

, as had previously been supposed. It lived 260 million years ago during the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

Period, in

arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

areas with

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s—almost like parts of modern-day

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

Botswana Botswana, officially the Republic of Botswana, is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory part of the Kalahari Desert. It is bordered by South Africa to the sou ...

. It is most closely related to '' Tiarajudens'' from

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Geology and paleoenvironment

''Anomocephalus'' was discovered at the base of the Beaufort Group, which is a geographical stratum that consists of mostly sandstone and shales that have been deposited in the Karoo Basin. The Beaufort Group dominated most of the basin with fluvial sedimentation, which is carried by streams and rivers that were most likely formed by ice masses such as glaciers. The climate at this time during the Mid to

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

became warm and semi-arid with seasonal rainfall. The central region of the basin is thought to have been drained by semi-permanent lakes and fine-grained meander belts.

History and discovery

''Anomocephalus'' was collected from a locality near Williston at the base of the Beaufort Group in the Karoo Basin, which is located within the Northern Cape Province of South Africa. It was discovered during the continued program of B. Rubidge to determine the lateral extent of the '' Eodicynodon'' (an extinct dicynodont therapsid) Assemblage Zone. It was first described by Modesto in 1999 and is known only by a partial skull with distinctive dentition and was preserved in hard mud rock. The discovery of ''Anomocephalus'' and its

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

position provided compelling evidence that

s initially diversified in Gondwana. This conflicts with previous suggestions that anomodonts were freely dispersing between the northern and southern regions of the Late Permian

Pangea Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia (continent), Siberia during the Carboniferous period ...

or that therapsids first evolved in Euramerica and then moved to

when climate became favorable. Additionally, the basal phylogenetic position of ''Anomocephalus'' suggests that herbivory was acquired initially by the anomodonts of Gondwana.

Description

Skull

The

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

contains a deep alveolar portion with room for two teeth and the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

is slightly elongated in comparison to other anomodonts. On the posterior portion of the maxilla, the characteristic anomodont curvature is seen in the

zygomatic arch In anatomy, the zygomatic arch (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...

. The nasal, prefrontal, and lacrimal resemble in both form and position those of other more basal anomodonts. Additionally, the jugal has a greater marginal exposure than other anomodonts and it tapers posteriorly. The dorsal lamella of the quadratojugal more closely resembles dicynodonts than basal anomodonts. The postorbital bone tapers ventrally and is visibly flat and curved. Like in other anomodonts, the

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

is dorsoventrally deep, and the squamosal is triradiate as suggested by the ventral and anterior processes. Anomocephalus and Tiarajudens

Dentition

''Anomocephalus'' possess five upper

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s that have an ovoid-shaped

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

when observed from the occlusal view. The dentition of the maxilla begins as tiny peg-like elements that become buccolingually wide and mesiodistally short. Six teeth are located on the pterygoid/ epipterygoid with four additional empty/damaged alveoli which suggests that there were at least ten teeth that made up the right palatal dentition. These palatal teeth have long, curved roots and the crowns are rectangular with an occlusal basin. There are two ''in situ'' lower incisiforms that are followed by two displaced lower teeth, the second of these teeth is transversally expanded and shows a saddle-like crown just like the palatal teeth. Additionally, there are three posterior lower teeth on the dentary with an unerupted, replacement tooth evident below the last lower tooth, which is evidence of at least a second wave of tooth replacement.

Post-cranial skeleton

Although a post-cranial skeleton was not found with the partial skull of ''Anomocephalus'', its sister taxa '' Tiarajudens eccentricus'' was discovered in 2011 with a partial left pectoral girdle and its left limb, an isolated left

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

with the pes, and foot elements. Of the axial elements, only two fragmentary ribs of parallel margin were found with no clear curvature and the most complete fragment was 8 mm wide and 86 mm long. The

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

that was found with ''T. eccentricus'' is approximately 177 mm in length and displayed well-expanded proximal and distal portions. The radius is 128 mm in length with expanded, flat proximal and distal surfaces, and the ulna is more robust than the radius and slightly longer at 137 mm. The pes showed five partial digits and they were all robust with arthrodial joints between the distal metatarsals and proximal phalanges as well as between the phalanges. Additionally, 15 left and three right gastralia were preserved as long, thin, and delicate bones.

Paleobiology

''Anomocephalus'' exhibits palatal teeth and the morphology of the teeth is consistent with a high-fiber herbivorous diet. Cisneros and colleagues suggested that ''Anomocephalus'' had an incipient propaliny during the occlusions due to the longitudinal dimensions of each facet of the quadrate being twice as large as the transversal dimension. They suggest that this would allow for forward and backward movement of the lower jaw during chewing. Propaliny is also suggested to be linked to improved capability for processing plant material.