''Ictidosaurus'' was a

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

, which lived during the middle

Permian The Permian ( ) is a geologic period and 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 251.9 Mya. It is the last period of the Paleoz ...

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 preserved ...

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 th ...

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 foll ...

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

Karoo Basin The Karoo Supergroup is the most widespread stratigraphy, stratigraphic unit in Africa south of the Kalahari Desert. The group (stratigraphy), supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Pennsylvan ...

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

Iziko South African Museum The Iziko South African 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 site in the Company's Garden since 1897. The museum houses important A ...

archives, were originally classified within

therocephalia Therocephalia is an extinct suborder of eutheriodont therapsids (mammals and their close relatives) from the Permian and Triassic. 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. Scylacosa ...

.> The

type species In 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 species that contains the biological type specimen ...

is ''I. angusticeps''.

Description

Type specimen

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

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-physiolo ...

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, whe ...

s, one distal tip of a precanine, a large canine, and 18 lateral convex single cone

postcanine Cheek teeth or post-canines 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 (plural diastemata, from Greek διάστημα, 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 ...

. />

Serrations Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied pr ...

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 mammal has b ...

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 mentum is an anatomical structure, a projecting feature that is near the mouth of a variety of animals: *In insects, the mentum is the distal part of the labium. The mentum bears the palps, glossae, paraglossae, and/or ligula. *On the huma ...

and lose

symphysis A symphysis (, pl. 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 ...

, 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 Occlusion may refer to: Health and fitness * Occlusion (dentistry), the manner in which the upper and lower teeth come together when the mouth is closed * Occlusion miliaria, a skin condition * Occlusive dressing, an air- and water-tight trauma ...

, 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). />

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 shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, res ...

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 be ...

, with the type locality being near

Beaufort West Beaufort West (Afrikaans: ''Beaufort-Wes''; Xhosa: ''eBhofolo'') 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 Beauf ...

(32.3° S, 22.6° E),

Western Cape The Western Cape is a province of South Africa, situated on the south-western coast of the country. It is the fourth largest of the nine provinces with an area of , and the third most populous, with an estimated 7 million inhabitants in 2020 ...

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

Drake Passage The Drake Passage (referred to as Mar de Hoces Hoces Sea"in Spanish-speaking countries) is the body of water between South America's Cape Horn, Chile and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atla ...

(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 relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

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, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

References

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