''Ictidosaurus'' was a therapsid

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 ...

found in the

Abrahamskraal Formation The Abrahamskraal Formation is a geological formation and is found in numerous localities in the Northern Cape, Western Cape, and the Eastern Cape of South Africa. It is the lowermost formation of the Adelaide Subgroup of the Beaufort Group, a ma ...

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 ...

, which lived during the middle

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.>

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of the type species were found in the ''Tapinocephalus'' (

Capitanian In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian Epoch or Series. The Capitanian lasted between and million years ago. It was preceded by t ...

age, 265.8-260.4 Ma), and the base of the ''Eodicynodon'' (

Wordian In the geologic timescale, the Wordian is an age or stage of the Permian. It is the middle of three subdivisions of the Guadalupian Epoch or Series. The Wordian lasted between and million years ago (Ma). It was preceded by the Roadian and fo ...

age, 268–265.8 Ma) assembly zones, of the

Karoo Basin The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a per ...

. />> Older classifications of the species, along with many other specimens found in the

Iziko South African Museum The Iziko South African Museum, formerly the South African Museum (Afrikaans: Suid-Afrikaanse Museum), is a South African national museum located in Cape Town. The museum was founded in 1825, the first in the country. It has been on its present ...

archives, were originally classified within

therocephalia Therocephalia is an extinct clade of therapsids (mammals and their close extinct relatives) from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their te ...

n family names, in this case the Ictidosauridae, which has been reclassified as belonging to the

Scylacosauridae Scylacosauridae is an extinct family of therocephalian therapsids. Scylacosaurids lived during the Permian period and were among the most basal therocephalians. The family was named by South African paleontologist Robert Broom in 1903. Scylacos ...

.> The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''I. angusticeps''.

Description

Type specimen

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

was of the ''Ictidosaurus angusticeps'' labeled SAM-PK-630 (NMQR 2910), found in the Tapinocephalus assembly zone. /> The skull measured 168 mm from snout to posterior of the left mandible, /> 41 mm across the skull in-between the canines, and 41 mm in height, and has been heavily disturbed by fracturing, reshaping of bone structures, and distortions, with the right side being the most well preserved of the skull. /> /> 16 to 17 teeth were identified on one side, and 10 on the other, with non being palatal. /> The upper

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

consists of six cylindrical

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, one distal tip of a precanine, a large

canine Canine may refer to: Zoology and anatomy * Animals of the family Canidae, more specifically the subfamily Caninae, which includes dogs, wolves, foxes, jackals and coyotes ** ''Canis'', a genus that includes dogs, wolves, coyotes, and jackals ** Do ...

, and 18 lateral convex single cone

postcanine Cheek teeth or postcanines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles). Mammals have multicuspidate molars (three in placentals, four in marsupials, in each jaw quadrant) and p ...

(9 on each side), the first one of which is separated from the canine by

diastema A diastema (: diastemata, from Greek , 'space') is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to ...

. /> Serrations on the teeth can be found on three of the incisors, on the posterior of the canine, and the anterior and posterior of the left side third postcanine tooth, which is in prosses of

tooth eruption Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligament plays an important role in tooth eruption. The first human teeth to appear, the decidu ...

. /> The large number of postcanines is attributed to the length of the skull. /> The nasal process of 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 ...

reaches the level of the posterior borders of the nares. /> The species have many features in common with other early and more primitive Therocephalians, such as serated teeth, three lower incisors, a sloping

mentum The term mentum can refer to several anatomical structures near the mouth of an animal: *The median plate of an insect's labium. *The protruding part of the human chin. *A certain thin projection of the soft parts of the animal, below the mouth, i ...

and lose

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

, but it is set apart by its small marginal maxillary precanine, as well as the 6 upper incisors. />

Known specimens

At present, there are only two collections with this fossil, located in South Africa.> The specimens of these collections, holotype SAM-PK-630 (NMQR 2910) and SAM-PK-77957 (AMNH 5527), both have the anterior portions of their snouts and mandibles in occlusion, making cranial anatomy unknown. /> /> Despite this, the crania have been used for differentiating ''I. angusticeps'' from ''Glanosuchus macrops'' by ''I. angusticeps'' having precanines (confirmed by

CAT-scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

). />

Distribution

The specimens found would have lived during the Permian South Africa, some 265 to 259 Ma. /> The two specimens known are from a

river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...

plain and a terrestrial

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will b ...

, with the type locality being near

Beaufort West Beaufort West (Afrikaans: ''Beaufort-Wes''; Xhosa: ''eBhobhofolo'') is a town in the Western Cape province in South Africa. It is the largest town in the arid Great Karoo region, and is known as the "Capital of the Karoo". It forms part of the ...

(32.3° S, 22.6° E),

Western Cape The Western Cape ( ; , ) is a provinces of South Africa, province of South Africa, situated on the south-western coast of the country. It is the List of South African provinces by area, fourth largest of the nine provinces with an area of , an ...

. /> /> This locality was, during the Permian, positioned at what today is the

Drake Passage The Drake Passage is the body of water between South America's Cape Horn, Chile, Argentina, and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atlantic Ocean (Scotia Sea) with the southeastern part of the Pa ...

(60.0° S, 34.1° W), /> in-between

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

References

{{Taxonbar, from=Q105730442 Scylacosauridae Lopingian synapsids of Africa Permian South Africa Fossils of South Africa Beaufort Group Fossil taxa described in 1903 Taxa named by Robert Broom