Kembawacela

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Kembawacela
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Suborder:† Anomodontia
Clade:† Dicynodontia
Family:† Cistecephalidae
Genus:† Kembawacela
Angielczyk, Benoit & Rubidge, 2019
Type species
†Kembawacela kitchingi
Angielczyk, Benoit & Rubidge, 2019
Other species
  • †K. yajuwayeyiAraújo et al. 2022

Kembawacela ("iron digger") is an extinct genus of cistecephalid dicynodont from the Late Permian of East Africa. The genus contains two known species, the type species Kembawacela kitchingi from the Madumabisa Mudstone Formation of Zambia described in 2019, and a second species, K. yajuwayeyi, from the Chiweta Beds of Malawi described in 2022. Like other cistecephalids, Kembawacela was specialised for a fossorial, burrowing lifestyle similar to modern day moles. It is unique amongst cistecephalids for the presence of a pair of tusks in the upper jaw, characteristic of many other dicynodonts but lost in other cistecephalids. It is likely that Kembawacela was a locally endemic species of cistecephalid in the Luangwa Basin of Zambia.

Contents

Description

Kembawacela broadly resembled other cistecephalids in size and shape. It was a small dicynodont (skull length roughly 5 centimetres (2.0 in) long along the base) and had a highly specialised body plan for digging. Kembawacela is known from skulls, lower jaws and various pieces of postcrania, including parts of the pelvis, femur, ulna and various vertebrae. [1] Although broadly similar in superficial appearance, the two species K. kitchingi and K. yajuwayeyi can be distinguished by details of the skull architecture. [2]

Its skull is typical for cistecephalids, with a broad head and large temporal fenestra with a very short, tapered snout. It had large, strongly forward facing eyes like some other cistecephalids (including Cistecephalus ), but unlike the smaller, sideways facing eyes of Cistecephaloides and Kawingasaurus . Similarly, the zygomatic arches project out almost laterally behind the eyes and curve back almost 90 degrees to the back of the skull. The pineal foramen ("third eye") is positioned very far back on the roof of the skull, overhanging the very back of the skull (similar to Sauroscaptor ). [3] Kembawacela is most obviously distinguished by the prominent tusks in its upper jaw. The majority of Kembawacela specimens have these tusks, and it is possible that they were sexually dimorphic in this species. These tusks face slightly out to the sides, but do not sit out on a prominent caniniform process projecting from the jaw margin like in some other dicynodonts. Aside from the tusks, Kembawacela was otherwise toothless, and possessed a keratinous beak at the tips of its jaws, as is typical of dicynodonts. The beak was relatively broad and blunt, and the tip of the upper jaw was arched upwards. [1]

Between K. kitchingi and K. yajuwayeyi, they can be distinguished by details of the individual bones and anatomy of the skull, including the shape of the jugal bone of the cheek. In K. kitchingi, the ascending process that joins to the postorbital bone to form the postorbital bar rimming the eye socket is exposed on the back of the bar, while in K. yajuwayeyi it is hidden on the internal side. Further, the anterior process of the jugal beneath the eye is notably taller in K. yajuwayeyi than in K. kitchingi, despite the only known skull of the former being slightly compressed. Another difference is in the position of the maxillary canal, a channel for the sensitive trigeminal nerve and its blood vessels in the snout. In K. kitchingi it emerges and runs laterally from the maxillary sinus, whereas the canal sits just anteriorly in front of the sinus in K. yajuwayeyi. The angle between the anterior rami of the pterygoid bones (sheets of bone connecting to the palatine bones in front) on the roof of the mouth also differs between them, with K. yajuwayeyi having a much narrower ~46° angle between them compared to the ~61° of K. kitchingi. [2]

The body of Kembawacela is poorly known, but the preserved skeleton of K. kitchingi resembles that of other cistecephalids like Cistecephalus. It had three sacral vertebrae and an ilium with well developed forward and backward pointing processes, and a large, robust ulna in the arm. Unlike Cistecephalus, however, the head of the femur is roughly triangular shaped. [1]

History of discovery

Specimens of Kembawacela were first discovered and collected in the 1960s by Alan Drysdall and James Kitching in the Luangwa Basin of Zambia. They reported discovering at least 13 specimens that they preliminarily assigned to Cistecephalus microrhinus and the now synonymous C. planiceps. Four of these specimens were identified in the collections of the Evolutionary Studies Institute at the University of the Witwatersrand in Johannesburg, South Africa, although a possible fifth specimen originally noted by Kitching has since been lost. [1]

The specimens were later suggested to belong to a new species of Cistcephalus in an unpublished BSc honours thesis by Freeman in 1993. Further examinations and the discovery of an additional four specimens proposed that the Luangwa cistecephalid was an entirely new genus. [4] In 2019, the taxon was formally described in detail and named Kembawacela kitchingi by Kenneth Angielczyk, Julien Benoit and Bruce Rubidge. The genus name is from the phrase "kemba wacela", translated to "iron digger" in the locally spoken Bemba language. It was named for the iron-rich hematite nodules various specimens from the Luangwa Basin—including the type specimen of Kembawacela (NHCC LB18)—have been found in, as well referring to the proposed digging lifestyle of cistecephalids. The species was named to honour James Kitching, who collected the first specimens of Kembawacela. [1]

The specimens were collected from various different localities in the Luangwa Basin, but were all from the upper Madumabisa Mudstone Formation. This formation is believed to overlap in time with the Cistecephalus Assemblage Zone (AZ) and Daptocephalus AZ of the Karoo Basin in South Africa, which have been dated to the Wuchiapingian to early Changhsingian in the Late Permian. The specimens are housed at both the Evolutionary Studies Institute in South Africa and at the National Heritage Conservation Commission in Lusaka, Zambia. [1]

In 2016, a cistecephalid skull (DMMM-PK-16-1) was found encased in a rock nodule during exploration of the Chiweta Beds in the Mount Waller Area of Northern Malawi. Due its small size and delicate nature, the examination of the specimen was performed using x-ray microtomography to image the bones inside the rock matrix. This skull was formally described and named as a new species of Kembawacela, K. yajuwayeyi, by Araújo and colleagues in 2022. The authors named the species in honour of their friend Dr. Yusuf Juwayeyi, an accomplished archaeologist, professor, and international representative of Malawian research. The species name combines the surname Juwayeyi with Ya-, the possessive prefix in the Chichewa language. The skull is mostly complete, missing only the tip of the snout, its left zygomatic arch and postorbital bar behind the eye, and parts of the occiput. [2]

Classification

Kembawacela is well supported as a member of the family Cistecephalidae in the phylogenetic analysis of Angielczyk et al. (2019), where it was found as a relatively basal member of the clade:

Kistecephalia

Kembawacela is primarily distinguished from other cistecephalids by its tusks, but can also be uniquely diagnosed by a trough on the underside of the vomer and an interparietal bone with paired extensions that reach up from the back of the skull to flank the pineal foramen. There are also various other slight differences of the skull and skeleton between it and other cistecephalids. [1]

Palaeobiology

It is possible that Kembawacela was sexually dimorphic, as two of the seven known specimens appear to have lacked tusks. Notably, one of these specimens is the largest known individual, implying that the lack of tusks was not due to it not being fully grown yet. Sexual dimorphism is known from other cistecephalids, such as the prominent ridges over the eyes in Cistecephalus, and although Kembawacela lacks those traits the presence or absence of tusks is suggested to be an indicator of sexual dimorphism more broadly in dicynodonts. Unfortunately, the relatively small sample size means this possibility cannot be statistically analysed. [1]

The tusks of Kembawacela are also notable as one specimen preserves unerupted tusks within the jaw bones. There is no evidence that these tusks are replacements of a previous pair (as has been suggested to occur in Diictodon ), and another specimen with the inside of the jaw exposed preserves no such replacements either. The size of the specimen is comparable to the others, which would suggest that the tusks of Kembawacela may not have erupted until quite late in the animal's life, close to their mature body size. It's possible that this relatively late eruption of the tusks in Kembawacela was taken even further in other cistecephalids, where their development was suppressed and prevented entirely from erupting in the tuskless species. [1] [4]

Burrowing

Kembawacela shares various features with other cistecephalids associated with a fossorial (burrowing) lifestyle. The ulna, the only known bone from the forelimb, has the typically large olecranon process associated with scratch-digging found in other cistecephalids.

The skull has various features associated with burrowing, being broad and wedge-shaped. The large, forward facing eyes may be related to seeing in low-light environments, with binocular vision providing greater light sensitivity, although this is not typical of modern fossorial mammals which have small eyes (as in Cistecephaloides and Kawingasaurus). Interestingly, Kembawacela is the only known cistecephalid known to preserve pieces of the bony sclerotic ring surrounding the eye, and they are remarkably smaller than is suggested by the size of the orbits. However, they were too incompletely preserved to estimate the light sensitivity of the eyes.

The footplates of the bony stapes are large, associated with hearing low-frequency sounds underground, although its inner-ear is not as specialised as Kawingasaurus. [1]

Palaeoecology

Kembawacela coexisted with a wide variety and abundance of other dicynodonts in the upper Madumabisa Mudstone Formation, including Endothiodon , Compsodon , Pristerodon , the burrowing Diictodon feliceps , Emydops , Dicynodontoides , a species similar to Katumbia , Odontocyclops whaitsi , Oudenodon bainii , Kitchinganomodon , Daptocephalus , Syops , Digalodon cf. rubidgei and a species of lystrosaurid. [4] [5] Other therapsids included the locally endemic predatory therocephalians Ichibengops and Mupashi , as well as the more widespread Theriognathus microps and Ictidosuchoides longiceps , along with the semi-aquatic cynodont Procynosuchus and an indeterminate biarmosuchian. [6] [7] [8] [9] Reptiles are represented by the pareiasaur Pareiasuchus , a herbivorous parareptile. [10]

Much of the fauna of the Madumabisa Mudstone Formation is shared with that of the Cistecephalus AZ in the Karoo, South Africa, suggesting the two regions shared similar biomes and were broadly connected. However, the presence of endemic species like Kembawacela are indicative of fine scale variations between the two localities, such as environmental differences. The fossorial lifestyle of Kembawacela and other cistecephalids is a likely factor in its endemism, as its unique ecology would have limited its ability to disperse and so restricted its range to within the Luangwa Basin. [1]

The environment of the upper Madumabisa Mudstone Formation was a wet, vegetated floodplain within a wide rift valley with plentiful sinuous meandering rivers, ponds and lakes prone to episodic flooding. [4]

Related Research Articles

<span class="mw-page-title-main">Dicynodontia</span> Extinct clade of therapsids

Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typically toothless beak, unique amongst all synapsids. Dicynodonts first appeared in Southern Pangaea during the mid-Permian, ca. 270–260 million years ago, and became globally distributed and the dominant herbivorous animals in the Late Permian, ca. 260–252 Mya. They were devastated by the end-Permian Extinction that wiped out most other therapsids ca. 252 Mya. They rebounded during the Triassic but died out towards the end of that period. They were the most successful and diverse of the non-mammalian therapsids, with over 70 genera known, varying from rat-sized burrowers to elephant-sized browsers.

<i>Robertia</i> Extinct genus of dicynodonts

Robertia is an extinct genus of small herbivorous dicynodonts from the Middle to Late Permian of South Africa, between 260 and 265 million years ago. It is a monospecific genus, consisting of the type-species R. broomiana, which was classified by Lieuwe Dirk Boonstra in 1948 and named in honor of Robert Broom for his study of South African mammal-like reptiles.

<i>Cistecephalus</i> Extinct genus of dicynodonts

Cistecephalus is an extinct genus of dicynodont therapsid from the Late Permian of southern Africa. It was a small, specialised, burrowing dicynodont, possibly with habits similar to a modern mole. The head was flattened and wedge-shaped, the body long, and the forelimbs very strong, with similarities in structure to the forelimb of modern burrowing mammals.

<i>Diictodon</i> Extinct genus of dicynodonts

Diictodon is an extinct genus of pylaecephalid dicynodont that lived during the Late Permian period, approximately 255 million years ago. Fossils have been found in the Cistecephalus Assemblage Zone of the Madumabisa Mudstone of the Luangwa Basin in Zambia and the Tropidostoma Assemblage Zone of the Teekloof Formation, Tapinocephalus Assemblage Zone of the Abrahamskraal Formation, Dicynodon Assemblage Zone of the Balfour Formation, Cistecephalus Assemblage Zone of the Middleton or Balfour Formation of South Africa and the Guodikeng Formation of China. Roughly half of all Permian vertebrate specimens found in South Africa are those of Diictodon. This small herbivorous animal was one of the most successful synapsids in the Permian period.

<i>Cistecephalus</i> Assemblage Zone

The Cistecephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in South Africa. This biozone has outcrops located in the Teekloof Formation north-west of Beaufort West in the Western Cape, in the upper Middleton and lower Balfour Formations respectively from Colesberg of the Northern Cape to east of Graaff-Reinet in the Eastern Cape. The Cistecephalus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Late Permian in age.

<i>Endothiodon</i> Extinct genus of dicynodonts

Endothiodon is an extinct genus of medium to large dicynodont from the Late Permian. Like other dicynodonts, Endothiodon was an herbivore, but it typically lacked the two tusks that characterized most other dicynodonts and instead had long rows of teeth inset in the jaws that replaced in waves. The anterior portion of the upper and lower jaw are curved upward, creating a distinct beak that is thought to have allowed them to be specialized grazers.

<i>Myosaurus</i> Extinct genus of dicynodont from the lower Triassic

Myosaurus is a genus of dicynodont synapsids. Myosaurus was a small, herbivorous synapsid that existed around the early Triassic period. All of the fossils found of this species were found in Antarctica and South Africa. Compared to other fossils found from species that existed during this time, the Myosaurus is not common in the fossil record. This is due to a shortage of discovered fossils that possess characteristics unique to the Myosaurus. Notably, under 130 fossil fragments have been found that have been classified as Myosauridae, and almost all have been skulls. These skulls can be classified as Myosaurus because this species, unlike other dicynodonts, do not possess tusks or postfrontal teeth. The only species identified in the family Myosauridae is the Myosaurus gracilis, or M. gracilis. It should be recognized that the Myosaurus is almost always referred to as the M. gracilis in scientific research.

Compsodon is an extinct genus of dicynodont belonging to the superfamily Emydopoidea. Fossils have been found in the Balfour Formation of South Africa and the Madumabisa Mudstone of Zambia.

Digalodon is an extinct genus of kistecephalian dicynodont, known from the Karoo Basin of South Africa and the Upper Madumabisa Mudstone Formation of Zambia. Originally given a sparse description in 1948, for a time it was considered synonymous with other dicynodonts as a small juvenile individual of a larger genus, such as Aulacephalodon or Dicynodontoides; however it has since been recognized as a distinct species.

<i>Dicynodontoides</i> Extinct genus of dicynodonts

Dicynodontoides is a genus of small to medium-bodied, herbivorous, emydopoid dicynodonts from the Late Permian. The name Dicynodontoides references its “dicynodont-like” appearance due to the caniniform tusks featured by most members of this infraorder. Kingoria, a junior synonym, has been used more widely in the literature than the more obscure Dicynodontoides, which is similar-sounding to another distantly related genus of dicynodont, Dicynodon. Two species are recognized: D. recurvidens from South Africa, and D. nowacki from Tanzania.

<i>Kawingasaurus</i> Extinct genus of dicynodonts

Kawingasaurus is an extinct genus of dicynodont therapsid from the Late Permian Usili Formation of Tanzania. It is a member of the family Cistecephalidae, and like other cistecephalids it is thought to have been fossorial. It is a member of the family Cistecephalidae. Cistephalidae includes genera Cisteceohalus, Cistecephaloides and Kawingasaurus. Greek for Saurus meaning “lizard” appears as a suffix denoting a reptilian origin. Living between 254.17 and 259.9 million years ago in the late Permian and believed to have the first and last recorded appearance in this time period. It lived in deep burrows as a suggested by most burrowing dicynodonts from evaluation of cranial sutures, vestibule inflation and enlarged stapes foot plates which are thought to be functionally correlated with bone-conduction hearing; all observed in fossorial vertebrates which use seismic signals as communication.

<i>Odontocyclops</i> Extinct genus of dicynodonts

Odontocyclops is an extinct genus of Dicynodonts that lived in the Late Permian. Dicynodonts are believed to be the first major assemblage of terrestrial herbivores. Fossils of Odontocyclops have been found in the Karoo Basin of South Africa and the Luangwa Valley of Zambia. The phylogenetic classification of Odontocyclops has been long under debate, but most current research places them as their own genus of Dicynodonts and being very closely related to Rhachiocephalus and Oudenodon.

<i>Pristerodon</i> Extinct genus of dicynodont therapsid from the late Permian

Pristerodon is an extinct genus of dicynodont therapsid from the Late Permian of South Africa, Zambia and India.

Katumbia is a genus of dicynodont from Late Permian (Changhsingian) Kawinga Formation of the Ruhuhu Basin, Tanzania. and possibly the Upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia. The type species, K. parringtoni, was originally referred to the genus Cryptocynodon, which is now recognized as a junior synonym of Endothiodon.

Syops is an extinct genus of dicynodont therapsid. The type species S. vanhoepeni was first named in 1938 as Dicynodon vanhoepeni. Fossils of the genus have been found in the Cistecephalus Assemblage Zone in the Usili Formation of the Ruhuhu Basin, Tanzania and the Upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia. Its phylogenetic placement is somewhat uncertain, with multiple different studies finding it as either a basal geikiid, rhachiocephalid a dicynodontoid more derived than the most basal genera but less derived than Lystrosauridae, or a lystrosaurid.

<span class="mw-page-title-main">Cistecephalidae</span> Extinct family of dicynodonts

Cistecephalidae is an extinct family of dicynodont therapsids from the Late Permian of South Africa, India and Zambia. It includes the genera Cistecephalus, Cistecephaloides, and Kawingasaurus. Cistecephalids are thought to have had a fossorial or burrowing lifestyle, with adaptations such as broad skulls, strong forelimbs, and squat bodies. A similar group of dicynodonts called the pylaecephalids were also fossorial, although to a lesser extent than cistecephalids. Cistecephalids showed a high level of endemism, with each of the five known species unique to a single region.

<span class="mw-page-title-main">Usili Formation</span> Geologic formation in Tanzania

The Usili Formation is a Late Permian geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Permian, including temnospondyls, pareiasaurs, therapsids and the archosauromorph Aenigmastropheus.

<i>Bulbasaurus</i> Extinct genus of dicynodonts

Bulbasaurus is an extinct genus of dicynodont that is known from the Lopingian epoch of the Late Permian period of what is now South Africa, containing the type and only species B. phylloxyron. It was formerly considered as belonging to Tropidostoma; however, due to numerous differences from Tropidostoma in terms of skull morphology and size, it has been reclassified the earliest known member of the family Geikiidae, and the only member of the group known from the Tropidostoma Assemblage Zone. Within the Geikiidae, it has been placed close to Aulacephalodon, although a more basal position is not implausible.

<i>Thliptosaurus</i> Extinct genus of dicynodonts

Thliptosaurus is an extinct genus of small kingoriid dicynodont from the latest Permian period of the Karoo Basin in KwaZulu-Natal, South Africa. It contains the type and only known species T. imperforatus. Thliptosaurus is from the upper Daptocephalus Assemblage Zone, making it one of the youngest Permian dicynodonts known, living just prior to the Permian mass extinction. It also represents one of the few small bodied dicynodonts to exist at this time, when most other dicynodonts had large body sizes and many small dicynodonts had gone extinct. The unexpected discovery of Thliptosaurus in a region of the Karoo outside of the historically sampled localities suggests that it may have been part of an endemic local fauna not found in these historic sites. Such under-sampled localities may contain 'hidden diversities' of Permian faunas that are unknown from traditional samples. Thliptosaurus is also unusual for dicynodonts as it lacks a pineal foramen, suggesting that it played a much less important role in thermoregulation than it did for other dicynodonts.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Angielczyk, K.D.; Benoit, J.; Rubidge, B.S. (2019). "A new tusked cistecephalid dicynodont (Therapsida, Anomodontia) from the upper Permian upper Madumabisa Mudstone Formation, Luangwa Basin, Zambia". Papers in Palaeontology . 7: 405–446. doi:10.1002/spp2.1285. S2CID   210304700.
  2. 1 2 3 Araújo, R.; Macungo, Z.; Fernandez, V.; Chindebvu, E. G.; Jacobs, L. L. (2022). "Kembawacela yajuwayeyi n. sp., a new cistecephalid species (Dicynodontia: Emydopoidea) from the Upper Permian of Malawi". Journal of African Earth Sciences . 196: Article 104726. Bibcode:2022JAfES.19604726A. doi: 10.1016/j.jafrearsci.2022.104726 . S2CID   252393501.
  3. ↑ Kammerer, C.F.; Bandyopadhyay, S.; Ray, S. (2016). "A new taxon of cistecephalid dicynodont from the upper Permian Kundaram Formation of India". Papers in Palaeontology. 2 (4): 569–584. Bibcode:2016PPal....2..569K. doi:10.1002/spp2.1055. S2CID   88833541.
  4. 1 2 3 4 Angielczyk, K.D.; Steyer, J.-S.; Sidor, C.A.; Smith, R.M.H.; Whatley, R.L.; Tolan, S. (2014). "Permian and Triassic dicynodont (Therapsida: Anomodontia) faunas of the Luangwa Basin, Zambia: taxonomic update and implications for dicynodont biogeography and biostratigraphy". In Kammerer, C.F.; Angielczyk, K.D.; Fröbisch, J. (eds.). Early evolutionary history of the Synapsida. Springer, Dordrecht. pp. 93–138 In. ISBN   978-94-007-6841-3.
  5. ↑ Kenneth D. Angielczyk (2019). "First occurrence of the dicynodont Digalodon (Therapsida, Anomodontia) from the Lopingian upper Madumabisa Mudstone Formation, Luangwa Basin, Zambia". Palaeontologia Africana. 53: 219–225. hdl:10539/26832.
  6. ↑ Huttenlocker, Adam K.; Sidor, Christian A.; Angielczyk, Kenneth D. (2015). "A new eutherocephalian (Therapsida, Therocephalia) from the upper Permian Madumabisa Mudstone Formation (Luangwa Basin) of Zambia". Journal of Vertebrate Paleontology . 35 (5): e969400. Bibcode:2015JVPal..35E9400H. doi:10.1080/02724634.2015.969400. S2CID   83554630.
  7. ↑ Huttenlocker, A. K.; Sidor, C. A. (2016). "The first karenitid (Therapsida, Therocephalia) from the upper Permian of Gondwana and the biogeography of Permo-Triassic therocephalians". Journal of Vertebrate Paleontology. 36 (4): e1111897. Bibcode:2016JVPal..36E1897H. doi:10.1080/02724634.2016.1111897. S2CID   130994874.
  8. ↑ Kemp, T. S. (1979). "The primitive cynodont Procynosuchus: functional anatomy of the skull and relationships". Philosophical Transactions of the Royal Society B . 285 (1005): 73–122. Bibcode:1979RSPTB.285...73K. doi:10.1098/rstb.1979.0001.
  9. ↑ Sidor, C. (2015). "The first biarmosuchian from the upper Madumabisa Mudstone Formation (Luangwa Basin) of Zambia". Palaeontologia Africana. 49: 1–7. hdl: 10539/17373 . ISSN   2410-4418.
  10. ↑ Lee, M. S. Y.; Gow, C. E.; Kitching, J. W. (1997). "Anatomy and relationships of the pareiasaur Pareiasuchus nasicornis from the Upper Permian of Zambia" (PDF). Palaeontology . 40 (2): 307–335.
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