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.

Description

''Ufudocyclops'' is a large dicynodont, with the largest specimen reconstructed to have an estimated skull length of and the smaller complete holotype skull at approximately 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.

Skull

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" ( 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.

Mandible

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.

History of discovery

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''.

Hancox and Rubidge later briefly described the specimens in August 1996, and then again in more detail in May 2013, referring them both times to the Tanzanian dicynodont ''Angonisaurus'' after favourably comparing their skulls. However, the South African specimens were not identical to the Tanzanian ''A. cruickshanki'', interpreted as either a difference between species, sexual dimorphism, or intraspecific variation between different populations, so Hancox and Rubidge provisionally diagnosed them as ''Angonisaurus'' sp. Nonetheless, they were regarded as the first record of ''Angonisaurus'' outside of the Manda Beds in Tanzania. This was suggested to support a shared Middle Triassic fauna between the uppermost ''Cynognathus'' AZ (now known as the ''Ufudocyclops''–''Cricodon'' Subzone) and the Manda Beds, based on the shared presence of ''Angonisaurus''.

The third and best preserved specimen of ''Ufudocyclops''—BP/1/8208, which would become the type specimen—was not discovered until 2014 and then collected in 2017 as part of a series of joint excavations by the Evolutionary Studies Institute of the University of the Witwatersrand (Johannesburg) and the University of Birmingham (United Kingdom). The skull was found upside down and isolated in a metre thick block of greenish grey fine grained sandstone, alongside the skull of the large cynodont ''Impidens''. The earlier specimens BP/1/5530 and BP/1/5531 were shown to be identical in form to the type specimen of ''Ufudocyclops'', prompting a reinterpretation of the two fossils as specimens of ''Ufudocyclops'', and not ''Angonisaurus'' as originally believed.

The genus ''Ufudocyclops'' was named from the Xhosa word ''ufudo'', meaning "tortoise", in reference to its toothless, tortoise-like beak, and the Ancient Greek ''cyclops'', referring to the very large size of the pineal foramen ("third eye"). The species is named in honour of Mr. Pepson "Pepsi" Mukanela as recognition for his skills in fossil preparation at the Evolutionary Studies Institute, including his work on the holotype, who had recently retired before its publication. The holotype skull is nearly complete, missing only its left temporal arch and the tips of the caniniform processes. The tip of the snout was also accidentally sawed through during excavation, separating the very front face of the premaxilla from the rest of the skull, but nothing was lost during collection. The condition of the skull is good, preserving much of the surface features including sutures on the skull roof and palate, as well as much of the ornamentation with only some wear on the top of the snout and to the back of the skull. The two referred skulls are much more incomplete and disarticulated, with BP/1/5530 consisting of only a partial skull roof and a single caniniform process, while BP/1/5531 also includes pieces of the palate, braincase and lower jaw.

Classification

Initial examinations of the referred specimens BP/1/5530 and BP/1/5531 identified them as belonging to the genus ''Angonisaurus''. This was argued on the basis of a combination of shared features between these specimens and ''Angonisaurus'' thought to be unique to them (although they are now known to be more widespread in Kannemeyeriiformes) rather than shared unique traits. The poor preservation of these specimens made identification difficult, and it wasn't until the discovery of the nearly complete holotype skull that the distinctiveness of ''Ufudocyclops'' could be properly appreciated. Interestingly, while not yet recognised as their own genus, the referred specimens of ''Ufudocyclops'' were correctly determined to belong to the family Stahleckeriidae, contrasting with associations of ''Angonisaurus'' with Shansiodontidae at the time.

''Ufudocyclops'' is distinguished from other kannemeyeriiform dicynodonts, as well as ''Angonisaurus'', by its 'X'-shaped intertemporal bar and deep triangular depression behind the pineal foramen, as well as by the extension of the jugal beneath the eyes and the two distinctly separated nasal bosses.

The relationship of ''Ufudocyclops'' with other dicynodonts was tested phylogenetically by Kammerer and colleagues by combining the data from three other recently updated analyses (Angielcyzk & Kammerer 2017, Angielcyzk ''et al.'' 2018, and Kammerer 2018) and the new information from the holotype of ''Ufudocyclops''. A simplified cladogram, an excerpt from the full analysis, focused on the relationships of ''Ufudocyclops'' within Kannemeyeriiformes is shown below:

Their results were generally similar to previous studies, although notably within Kannemeyeriiformes the family Shansiodontidae was found to be paraphyletic.

''Ufudocyclops'' and ''Stahleckeria

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