Njalila

Last updated

Njalila
Temporal range: Late Permian
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade:† Gorgonopsia
Genus:† Njalila
Gebauer & Maisch, 2026
Species:
†N. nasuta
Binomial name
†Njalila nasuta
Synonyms

Njalila is an extinct genus of gorgonopsian (predatory therapsids, related to modern mammals) that lived during the Late Permian of East Africa, known from fossils found in what is now Tanzania. The type and only species, Njalila nasuta, was originally named as a species of the gorgonopsian genus Dixeya (now considered either a junior synonym of Aelurognathus or a incertae sedis ) in 1950. The taxon was subsequently recognised as distinct from Dixeya and other gorgonopsians following repeated revisions of gorgonopsian taxonomy during the rest of the 20th century, but it did not receive its own genus name until 2007. However, because this name was first proposed in a PhD thesis, it remained a nomen nudum until its formal validation through an official publication in 2026. With a skull reaching up to 18 centimetres (7.1 in) in length, Njalila is a medium-sized gorgonopsian characterised by a distinctive straight snout profile with an upturned and "pinched" nose. The fossil record of the Usili Formation where it was discovered shows that Njalila was contemporaneous with many other gorgonopsians, including much larger representatives such as Inostrancevia and rubidgeines.

Contents

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. [1] 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. [2] [3] Von Huene regarded these specimens as representatives of a second species of the genus Dixeya, a taxon previously erected in 1927 by the South African palaeontologist Sidney H. Haughton to include its type species D. quadrata. [1] In 1970, French paleontologist Denise Sigogneau-Russell re-assigned the type species of Dixeya (D. quadrata) to the genus Aelurognathus (as Ae. quadrata) in her systematic revision of gorgonopsian taxonomy, thus synonymising the two genera. However, she did not consider D. nasuta to belong to Aelurognathus, instead tentatively referring the species to Arctognathus as Arctognathus? nasuta. [4] 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 [5] : 147 ) to belong to the same species. Instead, she suggested that they may also be referable to Ar.? nasuta—in addition to three other Tanzanian specimens (MZC 876, MZC 886, and MZC 887 [5] : 148 ) referred to D. quadrata by British palaeontologist Francis Rex Parrington in 1955. [6] [7] Nonetheless, Sigogneau was cautious in the referral of "D." nasuta to Arctognathus, [4] and had previously acknowledged that it was not a resolved matter, especially as—in her opinion— that the roof of the skull of this species was not well preserved enough for comparison. [8]

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. [5] : 139–156  However, because the International Code of Zoological Nomenclature does not recognize theses as valid published works, Njalila was therefore regarded as a nomen nudum ("naked name", i.e. it was not available as a valid genus name). [3] In 2015, the American paleontologist Christian F. Kammerer likewise acknowledged that "D." nasuta probably represents a single taxon that does not belong to Arctognathus, while remaining cautious about its taxonomic placement. He considered that further study of the material and more rigorous phylogenetic analyses were required, and recommended provisionally leaving its taxonomy open under the designation "Dixeya" nasuta until the issue could be resolved. [2] 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. [3]

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. [5] : 156  However, in their 2026 publication, Gebauer and Maisch did not follow this interpretation, instead cautiously referring the specimen to N. cf. nasuta. [3]

Description

Njalila is only known by its skull and jaws, which measured roughly 18 centimetres (7.1 in) 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. [5] : 151–152  [6]

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. [6] 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. [2] The occiput itself (the back face of the skull) is tall and roughly rectangular in shape, slightly concave and only gently sloping. [5] : 151–152 

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. [5] : 151–152  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. [2] 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. [6] 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. [2]

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. [5] : 151–152 

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. [5] : 242–244  [a]

Gorgonopsia

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. [10] [11]

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 . [11] 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. [3]

Paleoecology

Life restoration of a gorgonopsian hunting a herd of dicynodonts, based after the Usili Formation Usili Formation.png
Life restoration of a gorgonopsian hunting a herd of dicynodonts, based after the Usili Formation

All known fossil specimens of Njalila have come from the Usili Formation, Ruhuhu Basin, southern Tanzania. [2] [3] This formation, dating from the Upper Permian, is known to provide a fairly considerable number of fossils of various tetrapods. During this period, this formation would have been an alluvial plain which would have had numerous small meandering streams passing through well-vegetated floodplains. The basement of this formation would also have housed a generally high phreatic zone. [12]

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 [b] [13] [12] [10] The other theriodonts present are represented by the therocephalians Silphictidoides and Theriognathus as well as by the cynodont Procynosuchus . [12]

The most numerous tetrapods in the formation are the dicynodonts, among which are Compsodon , [14] 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 [15] and the pareiasaurs Anthodon and Pareiasaurus are known. The only temnospondyl recorded is Peltobatrachus . [12]

Notes

  1. ↑ Two genera cited in this cladogram, i. e. Scylacognathus and Eoarctops, have been synonymized with Eriphostoma since a 2015 paper. [9]
  2. ↑ Historically, much higher numbers of gorgonopsians were reported from the Usili Formation, [12] but most of them turned out to be junior synonyms of other genera. [10]

References

  1. 1 2 Huene, Friedrich von (1950). "Die Theriodontier des ostafrikanischen Ruhuhu-Gebietes in der Tübinger Sammlung" [The theriodonts of the East African Ruhuhu area in the Tübingen collection]. Neues Jahrbuch für Geologie und Paläontologie . 92 (1): 47–136.
  2. 1 2 3 4 5 6 Kammerer, Christian F. (2015). "Cranial osteology of Arctognathus curvimola, a short-snouted gorgonopsian from the Late Permian of South Africa". Papers in Palaeontology . 1 (1): 41–58. doi: 10.1002/spp2.1002 . S2CID   128905169.
  3. 1 2 3 4 5 6 Gebauer, Eva V. I.; Maisch, Michael W. (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. doi:10.1127/njgpa/1296. S2CID   284654153.
  4. 1 2 Sigogneau-Russell, Denise (1970). Révision systématique des gorgonopsiens sud-africains[Systematic review of South African gorgonopsians]. Paris: Éditions du Centre national de la recherche scientifique. pp. 97–102. OCLC   462558622.
  5. 1 2 3 4 5 6 7 8 9 Gebauer, Eva V. I. (2007). Phylogeny and Evolution of the Gorgonopsia with a Special Reference to the Skull and Skeleton of GPIT/RE/7113 (PDF) (PhD). Eberhard-Karls University of Tübingen. Archived from the original on 2012-07-22.
  6. 1 2 3 4 Parrington, Francis R. (1955). "On the cranial anatomy of some gorgonopsids and the synapsid middle ear". Proceedings of the Zoological Society of London . 125 (1). Blackwell Publishing Ltd: 1–40. doi:10.1111/j.1096-3642.1955.tb00589.x.
  7. ↑ Kemp, Tom S. (1969). "On the Functional Morphology of the Gorgonopsid Skull" (PDF). Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences . 256 (801): 1–83. Bibcode:1969RSPTB.256....1K. doi:10.1098/rstb.1969.0036. JSTOR   2416882. S2CID   58926603. Archived from the original (PDF) on 2012-10-19.
  8. ↑ Sigogneau-Russell, Denise (1968). "On the classification of the Gorgonopsia" (PDF). Palaeontologia Africana. 11: 33–46. hdl: 10539/16116 . S2CID   62840625.
  9. ↑ Kammerer, Christian F.; Smith, Roger M. H.; Day, Michael O.; Rubidge, Bruce S. (2015). "New information on the morphology and stratigraphic range of the mid-Permian gorgonopsian Eriphostoma microdon Broom, 1911". Papers in Palaeontology . 1 (2): 201–221. Bibcode:2015PPal....1..201K. doi:10.1002/spp2.1012. S2CID   128762256.
  10. 1 2 3 Kammerer, Christian F. (2016). "Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)". PeerJ . 4 e1608. doi: 10.7717/peerj.1608 . ISSN   2167-8359. PMC   4730894 . PMID   26823998.
  11. 1 2 Kammerer, Christian F. & Masyutin, Vladimir (2018). "Gorgonopsian therapsids (Nochnitsa gen. nov. and Viatkogorgon) from the Permian Kotelnich locality of Russia". PeerJ . 6 e4954. doi: 10.7717/peerj.4954 . PMC   5995105 . PMID   29900078.
  12. 1 2 3 4 5 Sidor, Christian A.; Angielczyk, Kenneth D.; Weide, D. Marie; Smith, Roger M. H.; Nesbitt, Sterling J.; Tsuji, Linda A. (2010). "Tetrapod fauna of the lowermost Usili Formation (Songea Group, Ruhuhu Basin) of southern Tanzania, with a new burnetiid record". Journal of Vertebrate Paleontology . 30 (3): 696–703. Bibcode:2010JVPal..30..696S. doi:10.1080/02724631003758086. S2CID   55397720.
  13. ↑ Brant, Anna J.; Sidor, Christian A. (2024). "Earliest evidence of Inostrancevia in the southern hemisphere: new data from the Usili Formation of Tanzania". Journal of Vertebrate Paleontology . e2313622. doi:10.1080/02724634.2024.2313622.
  14. ↑ Angielczyk, Kenneth D.; Peecook, Brandon R.; Smith, Roger M. H. (2023). "The mandible of Compsodon helmoedi (Therapsida: Anomodontia), with new records from the Ruhuhu Basin, Tanzania". Palaeontologia Africana. hdl:10539/35702. ISSN   2410-4418.
  15. ↑ Ezcurra, Martín D.; Scheyer, Torsten M.; Butler, Richard J. (2014). "The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence". PLOS ONE . 9 (2) e89165. Bibcode:2014PLoSO...989165E. doi: 10.1371/journal.pone.0089165 . PMC   3937355 . PMID   24586565.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.