Nyaphulia

The holotype specimen of Nyaphulia, NMQR 2913, was discovered in October 1982 by John Nyaphuli from the National Museum in Bloemfontein, South Africa. It was discovered on Botterkraal Farm in the Prince Albert District of Western Cape, South Africa in rocks from the lower Abrahamskraal Formation.^[1][2] This locality belongs to the Eodicynodon Assemblage Zone biozone, which has not been firmly dated but is roughly constrained to between 266.9 and 264.7 million years old during the Wordian stage of the middle Permian period (Guadalupian).^[3][4]

NMQR 2913 consists of a partial skull, lower jaw and unidentifiable bones from the postcranial skeleton.^[1] The specimen was preserved in a calcareous nodule surrounding the skull, which prior to discovery had broken into four separate pieces leading to parts from the middle of the skull being weathered away.^[2] The specimen was prepared both in acid and mechanically by Nyaphuli, and was later described in 1990 by Professor Bruce Rubidge. Rubidge named the specimen the type of a new species of Eodicynodon that he coined Eodicynodon olefseni, after his mentor in South African palaeontology and geology, Dr. Burger Oelefsen.^[2] Since its initial description, the delicate skull has been broken several times and consequently some parts of the skull included in its original description have been lost. The skull has also been taphonomically distorted and damaged by compression during fossilisation, deforming portions of the snout, crushing the palate, and displacing the entire occiput up and to the side.^[1]

NMQR 2913 was digitally re-examined and then redescribed in a 2024 paper by Alienor Duhamel and colleagues after the specimen was previously CT-scanned. These techniques allowed Duhamel and colleagues to describe anatomical features that were previously inaccessible through traditional examination (such as sutures and the internal surface of the skull), and comparisons to the anatomy of Eodicynodon oosthuizeni confirmed that NMQR 2913 is not referable to Eodicynodon. Consequently, they erected the new genus Nyaphulia for "E." oelofseni, named in honour of John Nyaphuli for his extensive work on South African palaeontology in the Karoo, including the discovery of NMQR 2913 itself.^[1]

Like other dicynodonts and early anomodonts, the skull of Nyaphulia has a short snout and large temporal fenestra. The overall shape of its skull is more like those of earlier anomodonts, such as Patranomodon than later dicynodonts, with a slender construction and a rounded—rather than sloping—snout profile. Nyaphulia is notable among dicynodonts for lacking tusks and the associated caniniform processes entirely (the latter still being present even in almost all tuskless dicynodonts), with a level jaw margin like those of earlier anomodonts. However, unlike earlier anomodonts, both the premaxilla and the tip of the dentaries in the upper and lower jaws, respectively, are entirely toothless, suggesting Nyaphulia had a beak like other dicynodonts.^[1]

The premaxillae supporting the beak are paired, unlike all other dicynodonts where they are fused into a single bone—except for Eodicynodon. The palatal surface of the premaxillae extends back somewhat, however, it is short and the bony internal nostrils (choanae) still open near the front of the mouth at the level of the maxillary teeth. As such, Nyaphulia does not have the bony secondary palate found in later dicynodonts (wherein the choanae open further back than the tusks). The nasal processes of the premaxilla that wedge between the nasal bones are relatively long in Nyaphulia compared to Eodicynodon and Patranomodon. The septomaxilla—a bone found in the nose unique to synapsids in the fossil record—is also exposed on the lateral surface of the snout, unlike most later dicynodonts where it is restricted to within the nostril opening. The exposure is thin and tapers back to meet the lacrimal, running between the nasals above and the maxilla below.^[1]

The squamosal is incomplete and missing the entire zygomatic arch, however the preserved portion encompassing the rear of the temporal fenestra is curved forward and down and the ventral process beneath the zygomatic arch is slender and fairly straight. This resembles the condition in Patranomodon and other early anomodonts, rather than being thicker and folded back as in later dicynodonts. Like other anomodonts, Nyaphulia has a preparietal bone. However, it unusually does not form part of the border of the pineal foramen, which in Nyaphulia is rimmed entirely by the parietals. The orbital region of Nyaphulia is poorly preserved, missing most of the jugal bone, but what is preserved indicates that the orbits are not as rounded as those Eodicynodon and are more similar to those of Patranomodon. The postorbital bar is thin compared to Eodicynodon.^[1]

The palate of Nypahulia is characteristic of dicynodonts. The transverse flange of the pterygoid bone is directed anteriorly as in later dicynodonts, rather than laterally to the side as in earlier anomodonts and other therapsids. The transverse flange also has a very prominent and bulbous palatal keel, developed more strongly than in other dicynodonts apart from Eodicynodon. By contrast, the shape of the parabasisphenoid flooring the braincase is more like that of Patranomodon and earlier anomodonts.^[1]

Unlike the paired premaxillae, the dentary tips of the lower jaw are fused into a single element at their symphysis. Like later dicynodonts, the dentary tip is toothless with flat dentary tables on either side and a prominent lateral dentary shelf above the mandibular fenestra. This shelf would have served as an attachment point for the forward slip of jaw musculature that allowed dicynodonts to pull the lower jaw backwards to chew. Like some other dicynodonts, the dentary tip is curved upwards and so appears hooked from the side.^[2] Unlike Eodicynodon but like other dicynodonts, it lacks a coronoid eminence on the rear of the lower jaw.^[1]

The teeth of Nyaphulia are homodont and consist entirely of small, peg-like teeth slanted forwards in the jaw. This is unlike most other therapsids but similar to other early anomodonts such as Patranomodon and Galeops. As preserved, each maxilla has at least three teeth, potentially up to six (although some of these may be replacement teeth), and the dentaries at least eight teeth each. The maxillary teeth are placed entirely behind the openings for the nostrils (equivalent to the position of the tusks in Eodicynodon), and the dentary teeth are similarly far back from the dentary tips, leaving the jaw tips toothless. Rubidge (1990) reported nutrient foramina at the dentary tip, associated with a keratinous covering, though Duhamel et al. (2024) did not identify them.^[1][2]