Ufudocyclops

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.

Ufudocyclops is a large dicynodont, with the largest specimen reconstructed to have an estimated skull length of 35 centimetres (14 in) and the smaller complete holotype skull at approximately 29 centimetres (11 in) long, and an estimated overall body size similar to that of Kannemeyeria. Only skulls and one partial lower jaw are definitively known, and no postcrania from the body has been identified, but it likely resembled other stahleckeriid dicynodonts with a heavily built body, short tail, and stocky limbs, possibly including upright hind-limbs paired with sprawling forelimbs like other large dicynodonts. Like some other stahleckeriids, Ufudocyclops appears to have lacked the tusks characteristic of many other dicynodonts, and was completely toothless.

The skull of Ufudocyclops superficially resembles Angonisaurus, being relatively tall and notably broad behind the snout, with large, sideways facing eyes and prominent tuskless caniniform processes on the maxilla that project away down and forwards from the snout, flaring out slightly to sides, with blunted tips. The lower surfaces of the maxilla are heavily pitted and rugose, as is the premaxilla and the palate on the roof of the mouth. These textures correspond to the eponymous tortoise-like keratinous beak typical of dicynodonts like Ufudocyclops. The isolated tip of the premaxilla demonstrates that these pits are superficial and do not continue deeper into the bone, as the inner texture of the bone is smooth and tabulate, and so are not foramina.

Like various other dicynodonts, the face is ornamented with bony bosses on the snout around the eyes. The bulbous nasal bones on the top of the snout each sport a single ovoid-shaped boss that overhangs the nostrils and stops just short of the orbits (eye sockets) in front of the eyes. The paired bosses are separated by a 3–7 cm (1–3 in) wide gap of flat, featureless bone between them on top of the snout where the premaxilla and the nasals meet. This is an unusual condition for kannemeyeriiforms, which typically only have a single large boss across the whole surface of the snout. In fact, the bosses are superficially more like those of cryptodonts—a group of Permian dicynodonts unrelated to kannemeyeriiforms—that also had a pair of divided nasal bosses. Similar, but smaller, bosses are found on the prefrontal and postorbital bones, situated around the upper front and back corners of the eyes, respectively. Like the nasal bosses, these two bosses are clearly separated as individual growths, and do not form a continuous rim around the top of the eyes.

The skull of Ufudocyclops is otherwise fairly standard for dicynodonts, however it has some other unique characteristics, such as the form of the jugal bone. In most other dicynodonts the jugal is small and restricted under the eyes, but in Ufudocyclops it extends along much of the lateral (outside) face of the zygomatic arch beneath the eyes and cuts off the maxilla, which usually joins to the squamosal on the zygomatic arch. This unusual setup of the jugal also causes the zygomatic arch to noticeably jut out from the skull under the eyes, compared to other kannemeyeriiforms where it gradually curves out away from the skull. In addition, while most kannemeyeriiforms have the front of the orbits formed only by the jugal and the lacrimal bone, Ufudocyclops also has a very small portion of the maxilla between them too.

Ufudocyclops is also characterised by the unique X-shaped intertemporal bar on the roof of the skull between each temporal fenestra, where the large jaw muscles attached. The bar is broad at the front just behind the eyes and at the back of the skull, while the middle is pinched inwards between the two temporal fenestra, creating the characteristic 'X'-shape. The eponymous pineal foramen on the roof of the skull is also proportionately "enormous" (6 cm (2.4 in) long), implying Ufudocyclops had a very well-developed parietal "third eye". The pineal foramen also has a characteristic depression behind it on the intertemporal bar that is deep and triangular in shape.

The lower jaw of Ufudocyclops is only partially known, and is only known from one of the referred specimens. Most of what is preserved consists of the front half of the mandibles, namely the two dentaries, as well as a splenial and portions of the angulars. The jaws are also missing the tip of the mandibular symphysis at the very front where the two jaw bones are fused, but enough is preserved to suggest the lower beak was somewhat squared off. The dentaries are toothless and covered in pits and grooves like those of the upper jaws, typical of the beaked lower jaws of derived dicynodonts. Additionally, parts of both the articular bones were found attached to the quadrates of the skull. These show the typical dicynodont arrangement with two rounded condyles divided by a ridge between them that allows for the lower jaw to slide backwards and forwards during feeding.

The first specimens of Ufudocyclops (BP/1/5530 and BP/1/5531) were discovered by palaeontologist P. John Hancox while fossil collecting in the southern Karoo Basin near Sterkstroom in the Eastern Cape Province, South Africa in an expedition to assess the stratigraphic range of the dicynodont Kannemeyeria. Together with his colleague Bruce S. Rubidge, the skulls were reported in a research letter to South African Journal of Science in February 1994, where the fossils were recognised as a third distinct genus of dicynodont from the Cynognathus Assemblage Zone (AZ), following Kannemeyeria and Kombuisia. At the time Hancox and Rubidge did not attempt to identify the specimens and simply referred to them as a "tuskless dicynodont". They speculated that large dicynodont postcranial remains from the upper Cynognathus AZ, previously attributed to Kannemeyeria, may have also belonged to their new dicynodont, and that their new dicynodont could be used to further subdivide the Cynognathus AZ above the range of Kannemeyeria.