Njalila

Research history

Njalila was originally described in 1950 by the German palaeontologist Friedrich von Huene on the basis of two skulls collected from the Usili Formation (formerly known as K6 or the Kawinga Formation), located in the Ruhuhu Basin of southern Tanzania. The two specimens in question are now catalogued as GPIT/RE/7118 (the holotype specimen) and GPIT/RE/7119 in the palaeontological collection of the University of Tübingen. Furthermore, Sigogneau (1970) only considered the holotype of D. quadrata from Malawi to belong to Aelurognathus, and she did not consider two additional specimens referred to D. quadrata by von Huene in 1950 from Tanzania (GPIT/RE/7120 and GPIT/RE/7121 Nonetheless, Sigogneau was cautious in the referral of "D." nasuta to Arctognathus,

The genus name Njalila was first proposed for "D." nasuta in 2007 by the German palaeontologist Eva Gebauer in her unpublished PhD thesis, in which it was named after the Njalila River, a tributary of the Ruhuhu River in Tanzania. In an article published in early 2026, Gebauer and her German colleague Michael W. Maisch formally redescribed the fossils of this taxon. In doing so, they officially established and diagnosed the genus Njalila as the valid and available name for "D." nasuta, in the new combination N. nasuta.

Also in her 2007 thesis, Gebauer proposed the existence of a second species of the genus Njalila, "N. insigna", based on another Tanzanian skull that had previously been referred to the South African gorgonopsian Scylacops capensis (MZC 885). She distinguished "N. insigna" from N. nasuta by the presence of thicker arches between its skull openings, a posteriorly wider skull, and a slightly more rounded snout profile. The specific epithet of this proposed taxon is a Latin term meaning "remarkable" or "conspicuous", in reference to the differences noted between it and N. nasuta. However, in their 2026 publication, Gebauer and Maisch did not follow this interpretation, instead cautiously referring the specimen to N. cf. nasuta.

Description

Njalila is only known by its skull and jaws, which measured roughly 18 cm in length (mid-sized for a gorgonopsian) and had a relatively short and compact snout. Compared with similarly short-snouted gorgonopsians (such as Arctognathus and Eriphostoma) the skull is not as wide at the rear, with only weakly flaring zygomatic arches and little constriction of the snout behind the canines. As such, its skull appears much more straight-sided when viewed from above, and is also generally wider than it is tall. Similarly, the profile of the skull along the top of the snout is also largely straight, although the tip is characteristically turned up in a sharp point above the nostrils, which were positioned far-forwards on the snout. The snout is also distinctive for its unusual 'pinched' appearance. The nasal bones along the top of the snout are broad, but are constricted along the middle. Furthermore, the septomaxilla (a small bone found in and around the nostrils of therapsids) bulges strongly outwards under and behind the nostrils but then rapidly hollows out just behind them on either side, giving the bridge of the nose the pinched appearance.

Behind the snout, the roof of the skull is distinctly concave with the rims of the orbits above the eyes noticeably raised above it. The orbits themselves are proportionately large and rounded, and face laterally out to the sides. The temporal fenestra, a hole in the skull behind the eye socket for jaw muscle attachment, is also very large. Subsequently, the bony arches surrounding and separating these openings (e.g. the suborbital arch, postorbital bar) are proportionately slender and thin. The parietal foramen ("third eye" opening) on top of the skull is large and surrounded by a raised boss of bone, and is positioned at the very back of the skull right above the occiput. The occiput itself (the back face of the skull) is tall and roughly rectangular in shape, slightly concave and only gently sloping.

As in other gorgonopsians, Njalila has large blade-like caniniform teeth. The incisor teeth (five in each premaxilla), however, are smaller than those of related gorgonopsians, and it only had four to five small postcanine teeth. The jawline of the maxilla in the upper jaw is notably convex, with a much more exaggerated curve of the toothrow than in other gorgonopsians except for Arctognathus. This exaggerated curvature is due to the post-canine teeth being housed in a raised bony flange of the maxilla behind the canines. The maxilla also has an unusual groove over the postcanine teeth, starting shallowly above the first postcanine and running down to the edge of the bone behind the 5th postcanine, deepening along its length. Like other gorgonopsians Njalila also possessed palatal teeth, three on each palatine and two on each pterygoid bones, with only weakly developed bosses supporting them. The vomer on the roof of the mouth is very broad at the front, but narrows rapidly to a constricted splint halfway down its length. This more resembles the vomer of the derived rubidgeines than the narrower vomer of earlier gorgonopsians. The vomer sports three ridges, one down its middle and two running along each edge.

The dentary bone of the lower jaw is comparatively slender, with a sloping mandibular symphysis that nonetheless bears the characteristic 'chin' of gorgonopsians. The reflected lamina of the angular bone towards the back of the jaw is only moderately ridged, in comparison to other gorgonopsians.

Classification

The phylogenetic relationships of Njalila were first analysed by Gebauer in her unpublished 2007 PhD thesis in the first computerised phylogenetic analysis of gorgonopsians ever conducted. Gebauer found Njalila as a member of the family Gorgonopsidae, which in her classification excluded the most basal genera of gorgonopsians in her tree that she regarded as plesiomorphic (i.e. representing the ancestral condition) for the group. Within Gorgonopsidae, Njalila was a relatively derived member but outside of the clade including the giant Rubidgeinae and Inostrancevia, occupying part of an evolutionary grade between them and more ancestral gorgonopsids. The results of Gebauer (2007) are depicted in the cladogram below.

The analysis of Gebauer (2007) was the first major attempt to perform a phylogenetic analysis of gorgonopsians; however, its results have not been borne out by subsequent independent analyses. Namely, Kammerer (2016) regarded Gebauer's analysis as "unsatisfactory", citing that many of the characters used by her analysis were based upon skull proportions that are variable within taxa, both individually and ontogenetically (i.e. traits that change through growth). As an example of a potential problem created by this, he highlighted the basal position of Aloposaurus (a wastebasket taxon of various immature gorgonopsians) compared to the stratigraphically older and morphologically basal Eoarctops (now a junior synonym of Eriphostoma) being found in a relatively more derived position.

Since a 2018 study authored by Kammerer and his Russian colleague Vladimir Masyutin, gorgonopsians have been divided into two subgroups of African and Russian origin, with the exception of the basal genera Nochnitsa and Viatkogorgon. In their 2026 publication, Gebauer and Maisch recovered Njalila within the African clade, where it is identified as a potential sister taxon to Arctognathus, although this result is only weakly supported in their analysis.

Paleoecology

All known fossil specimens of Njalila have come from the Usili Formation, Ruhuhu Basin, southern Tanzania.

Njalila was contemporary with many other gorgonopsians. These include Cyonosaurus, Gorgonops, Inostrancevia, Lycaenops, "Sauroctonus" parringtoni, Scylacops and the rubidgeines Aelurognathus, Dinogorgon, Rubidgea, Ruhuhucerberus and Sycosaurus The other theriodonts present are represented by the therocephalians Silphictidoides and Theriognathus as well as by the cynodont Procynosuchus.

The most numerous tetrapods in the formation are the dicynodonts, among which are Compsodon, Daptocephalus, Dicynodon, Dicynodontoides, Endothiodon, Euptychognathus, Geikia, Katumbia, Kawingasaurus, Oudenodon, Pristerodon, Rhachiocephalus and an indeterminate cryptodont. An undetermined biarmosuchian similar to Burnetia is also known. Therapsids are not the only tetrapods present in the Usili Formation. Indeed, sauropsids such as the archosauromorph Aenigmastropheus and the pareiasaurs Anthodon and Pareiasaurus are known. The only temnospondyl recorded is Peltobatrachus.

Notes

References

References

1. Huene, Friedrich von. (1950). "Die Theriodontier des ostafrikanischen Ruhuhu-Gebietes in der Tübinger Sammlung". [[Neues Jahrbuch für Geologie und Paläontologie]].
2. Sigogneau-Russell, Denise. (1970). "Révision systématique des gorgonopsiens sud-africains". [[French National Centre for Scientific Research.
3. (1955). "On the cranial anatomy of some gorgonopsids and the synapsid middle ear". [[Blackwell Publishing Ltd]].
4. Kemp, Tom S.. (1969). "On the Functional Morphology of the Gorgonopsid Skull". [[Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences]].
5. Sigogneau-Russell, Denise. (1968). "On the classification of the Gorgonopsia". Palaeontologia Africana.
6. (2026). "''Njalila'' gen. nov. (Therapsida, Gorgonopsia): a new genus for ''Dixeya nasuta'' von Huene, 1950 from the Late Permian Usili Formation of the Ruhuhu Basin, SW Tanzania". [[Neues Jahrbuch für Geologie und Paläontologie]] – Abhandlungen.
7. Gebauer, Eva V. I.. (2007). "Phylogeny and Evolution of the Gorgonopsia with a Special Reference to the Skull and Skeleton of GPIT/RE/7113". [[University of Tübingen.
8. (2015). "New information on the morphology and stratigraphic range of the mid-Permian gorgonopsian ''Eriphostoma microdon'' Broom, 1911". [[Papers in Palaeontology]].
9. Kammerer, Christian F.. (2016). "Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)". [[PeerJ]].
10. (2018). "Gorgonopsian therapsids (''Nochnitsa'' gen. nov. and ''Viatkogorgon'') from the Permian Kotelnich locality of Russia". [[PeerJ]].
11. (2024). "Earliest evidence of ''Inostrancevia'' in the southern hemisphere: new data from the Usili Formation of Tanzania". [[Journal of Vertebrate Paleontology]].
12. (2023). "The mandible of ''Compsodon helmoedi'' (Therapsida: Anomodontia), with new records from the Ruhuhu Basin, Tanzania". Palaeontologia Africana.
13. (2014). "The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence". [[PLOS ONE]].