Lycosuchidae

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Lycosuchidae
Temporal range: Middle Permian, 265–260  Ma
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Lycosuchus.jpg
Partial skull of Lycosuchus in the Museum für Naturkunde, with "double canines" visible
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade:† Therocephalia
Family:† Lycosuchidae
Nopcsa, 1923
Valid genera

† Lycosuchus
† Gorynychus ?
† Simorhinella

Synonyms
  • †TrochosuchidaeRomer, 1956
  • †TrochosauridaeRomer, 1966

Lycosuchidae is an extinct family of therocephalian therapsids from the Middle Permian Beaufort Group of South Africa. It currently includes only two monospecific genera, Lycosuchus , represented by L. vanderrieti, which was named by paleontologist Robert Broom in 1903, and Simorhinella , represented by S. baini, which was named by Broom in 1915. Both species are characterized by their large size, reduced tooth counts and short, relatively low and broad snouts.

Contents

Two sets of functional enlarged canine teeth, so-called "double canines", were once regarded as a defining feature of lycosuchids. However, recent studies have proposed that they actually represent co-existing functional and replacement canines, and various lycosuchid specimens show the teeth at different stages of growth and replacement. Nonetheless, the pattern of tooth replacement appears to be unusual in lycosuchids, and the alternating canines appear to occur concurrently more than in other predatory therapsid groups. [1] Lycosuchids are among the earliest known therocephalians and are also thought to be the most basal. The Russian genus Gorynychus , containing two species, may also belong to the family, although this result is not typically recovered.

Taxonomy and classification

UCMP 42667, a complete skeleton of a lycosuchid. Cynariognathus platyrhinus.jpg
UCMP 42667, a complete skeleton of a lycosuchid.

The concept of a family of "double canined" early therocephalians was first initiated by Broom in 1908, when he proposed that the "double canined" early therocephalians formed a separate unit from other early therocephalians then recognised as the "Pristerognathidae" (now known as Scylacosauridae). [3] Broom would continue to postulate that such a division existed, but for many decades he did not attribute a name to such a group despite Lycosuchidae already being made available. The family Lycosuchidae was first established by Baron Franz Nopcsa in 1923, although the name was often misattributed by later researchers until the end of the 20th century when his precedent was recognised. [4] A Lycosuchidae family was also used by Samuel W. Williston in his 1925 publication The Osteology of the Reptiles, and a similar concept was used by Haughton and Brink in 1954, though neither of them attributed any authorship to Lycosuchidae. [4]

The validity of Lycosuchidae was not always supported by researchers, particularly when simultaneous functional canines were the only proposed criterion. This culminated in a paper by Juri van den Heever in 1980, where he argued that lycosuchids were an unnatural, artificial collection of "pristerognathids" that had died during the process of alternating canine replacement typical of predatory therapsids, and argued it should be invalidated. [4] When not recognised as forming their own family, lycosuchid genera were typically subsumed under the family Scylacosauridae, which was more commonly (though incorrectly) identified as Pristerognathidae by most researchers during the 20th century. [5] Van den Heever would later reconsider his view on lycosuchids and recognise them as a distinct lineage after all, establishing the anatomical criteria for which the family is diagnosed today. [5] [6]

An alternate name for the family, Trochosuchidae, was established by Alfred Romer in 1956, apparently unaware of the pre-existing use of Lycosuchidae by other authors. [7] Romer named the family after Trochosuchus , a now dubious genus of lycosuchid. Curiously, Romer would erect a family for the lycosuchid genera for a second time in 1966, this time as Trochosauridae after the lycosuchid Trochosaurus (also now dubious). [8] Romer likely did this because in 1966 he felt that Trochosuchus was distinct from lycosuchids and so assigned it to another family, the Alopecodontidae (a family otherwise made up of what are now scylacosaurids). This is despite the fact that Romer had previously considered the genera Trochosuchus and Trochosaurus synonymous while under Trochosuchidae. Although Lycosuchidae has priority over either name, some authors perpetuated the use of Trochosuchidae and Trochosauridae, including some who used the former well after Romer proposed replacing it with Trochosauridae (e.g. Camp et al. (1968, 1972)). [5]

Dubious genera

Photo of NHMUK R5747, a referred specimen of the dubious lycosuchid Trochosaurus major, showing the skull and jaw in ventral view NHMUK PV R 5747 - All.jpg
Photo of NHMUK R5747, a referred specimen of the dubious lycosuchid Trochosaurus major, showing the skull and jaw in ventral view

Although now only containing two definitive members, a number of other genera have historically been assigned to Lycosuchidae (or its equivalent grouping by the author). However, all other genera besides Lycosuchus that have been historically included in Lycosuchidae are now regarded as nomen dubia, or dubious names. These include the aforementioned Trochosuchus and Trochosaurus, as well as Hyaenasuchus , Trochorhinus and Zinnosaurus . As such, the majority of specimens attributed to Lycosuchidae are incertae sedis, with only a few being attributable to diagnosable taxa. [5] [9]

The dubiousness of all other historically named lycosuchids is in part due to the often poor quality of their type material, which are often incomplete and badly weathered. Another confounding factor is that several were distinguished based on features such as the proportions of the canines, snout, and number of postcanine teeth—features now known to be variable and subject to taphonomic distortion—as is the case for Trochosuchus, Trochosaurus and Trochorhinus. [5] Also, the only other valid lycosuchid genus, Simorhinella, is only distinguished from Lycosuchus by features of its palate. As such, other lycosuchids cannot be identified to a genus if the palate is obscured, as it is in the holotypes of Hyenasuchus and Zinnosaurus. [1]

While the genus was never explicitly assigned to Lycosuchidae, two species of the dubious basal therocephalian Scymnosaurus , S. ferox (the type) and S. major, are also based upon lycosuchid material and so it could also be regarded as an additional dubious lycosuchid. [5] [1]

Phylogeny

An early phylogenetic hypothesis for lycosuchids was proposed by Broom in 1908 before the family had even been established. In it, Broom hypothesised that genera that would later become lycosuchids were one of several lines of descent from a primitive therocephalian common ancestor, namely Alopecodon . From this ancestor, Broom traced a direct line of descent from Hyaenasuchus, to Trochosuchus and finally into Lycosuchus. This line of descent was based upon their dentition, beginning with the aqcquisition of two supposed functional large canines in Hyaenasuchus, followed by a decrease in the number of incisors in Trochosuchus and finally to the loss of most postcanines in Lycosuchus. [3]

Following the taxonomic work of Van den Heever in the 1980s, Lycosuchidae become functionally monotypic and subsequently phylogenetic analyses have only ever included Lycosuchus to represent the group. As such, with only one taxon to include, it is difficult to assess whether Lycosuchidae as recognised (including the various specimens attributed to it) definitively forms a clade. For example, the first cladistic analysis of therocephalians by Hopson and Barghusen (1986) simply subsumed Lycosuchus into Pristerognathidae (=Scylacosauridae) as a single family of early therocephalians. Nonetheless, a revision of Scylacosauridae in 2023 by Christian F. Kammerer has explicitly defined Scylacosauridae to exclude Lycosuchus. [2]

Although Simorhinella has also been regarded as a lycosuchid since 2014, it has yet to be included in a phylogenetic analysis to test the family's potential monophyly. Notably, Abdala et al. (2014) highlight that while Simorhinella possesses the diagnostic characteristics of Lycosuchidae, it also has several traits in its palate found in scylacosaurids but not seen in Lycosuchus. This raises the possibility that Lycosuchidae is paraphyletic relative to scylacosaurian therocephalians (Scylacosauridae + Eutherocephalia), with Simorhinella potentially closer to Scylacosauria. [1]

On the other hand, the Russian therocepalian Gorynychus was recovered as the sister taxon of Lycosuchus by Liu and Abdala (2019), effectively in a monophyletic Lycosuchidae (shown below, left). [10] However, this result was only recovered under the majority rule consensus (i.e. it was not recovered in every iteration of the analysis), and it has only been recovered once since then. Indeed, most subsequent analyses of this dataset (such as Liu and Abdala, 2023, below right cladogram) have found Gorynychus to be placed intermediately between Lycosuchus and Scylacosauria (as would be the suggested position of Simorhinella). [11] Gorynychus was also assigned to Lycosuchidae by Suchkova and Golubev (2018), independently of these phylogenetic results, when they named G. sundyrensis. However, this was based entirely on anatomical similarities and was not supported by any phylogenetic analysis. [12]

Restorations of the possible lycosuchid Gorynychus Gorynychus species.jpg
Restorations of the possible lycosuchid Gorynychus

Note that in both cladograms, regardless of the placement of Gorynychus, Lycosuchus occupies a basalmost position in Therocephalia. This result has been consistently recovered in most phylogenetic analyses of therocephalian relationships, while scylacosaurids are closer to Eutherocephalia. Contrary to these results, a recent analysis from 2024 with the aim of analysing the relationships of early cynodonts and therocephalians found a paraphyletic Therocephalia in which Lycosuchus and Alopecognathus (representing scylacosaurids) were instead sister taxa, forming a clade that was itself the sister of Eutherocephalia + Cynodontia. [13]

Theriodontia  
Traditional therocephalians

Related Research Articles

<span class="mw-page-title-main">Therocephalia</span> Extinct order of therapsids

Therocephalia is an extinct clade of eutheriodont therapsids from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their teeth, suggest that they were carnivores. Like other non-mammalian synapsids, therocephalians were once described as "mammal-like reptiles". Therocephalia is the group most closely related to the cynodonts, which gave rise to the mammals, and this relationship takes evidence in a variety of skeletal features. Indeed, it had been proposed that cynodonts may have evolved from therocephalians and so that therocephalians as recognised are paraphyletic in relation to cynodonts.

<i>Anteosaurus</i> Extinct genus of anteosaurid synapsid from the Permian

Anteosaurus is an extinct genus of large carnivorous dinocephalian synapsid. It lived at the end of the Guadalupian during the Capitanian age, about 265 to 260 million years ago in what is now South Africa. It is mainly known by cranial remains and few postcranial bones. Measuring 5–6 m (16–20 ft) long and weighing about 600 kg (1,300 lb), Anteosaurus was the largest known carnivorous non-mammalian synapsid and the largest terrestrial predator of the Permian period. Occupying the top of the food chain in the Middle Permian, its skull, jaws and teeth show adaptations to capture large prey like the giants titanosuchids and tapinocephalids dinocephalians and large pareiasaurs.

<i>Trochosaurus</i> Extinct genus of therapsids from Permian South Africa

Trochosaurus is a dubious genus of therocephalian therapsid from South Africa, to which various species were once assigned. The genus was based upon multiple weathered and distorted fossils of therocephalians of the family Lycosuchidae. Like other lycosuchids, specimens placed in Trochosaurus have only five large incisors in each premaxilla, seemingly two functional "double canines" in each maxilla, and few postcanines. However, the fossils lack any further diagnostic traits to justify referring them to their own genus, or to any species therein. Hence, Trochosaurus is now considered to be a nomen dubium and is disused, as are all its assigned species.

<i>Moschorhinus</i> Genus of synapsid from late Permian and early Triassic South Africa

Moschorhinus is an extinct genus of therocephalian synapsid in the family Akidnognathidae with only one species: M. kitchingi, which has been found in the Late Permian to Early Triassic of the South African Karoo Supergroup. It was a large carnivorous therapsid, reaching 1.1–1.5 metres (3.6–4.9 ft) in total body length with the largest skull comparable to that of a lion in size, and had a broad, blunt snout which bore long, straight canines.

<i>Pristerognathus</i> Extinct genus of therapsid from the Middle Permian of South Africa

Pristerognathus is an extinct genus of therocephalian, known from the late Middle Permian (Capitanian) of South Africa. It lends its name to the now defunct Pristerognathus Assemblage Zone of the Beaufort Group of South African geological strata. Pristerognathus was a medium-sized therocephalian with a 25 cm (9.8 in) skull and a total length up to 1.5 m.

<i>Lycosuchus</i> Extinct genus of therapsids from the middle Permian of South Africa

Lycosuchus is an extinct genus of carnivorous therocephalians which lived in the Middle Permian 265—260 Ma existing for approximately 5 million years. As a member of the Lycosuchidae, the genus represents one of the earliest diverging therocephalians. The type and only species, L. vanderrieti, is known from a handful of well-preserved specimens featuring the cranium and lower jaw; the holotype US D173 housed at the University of Stellenbosch, South Africa, is a near complete occluded skull. Specimen MB.R. 995, housed at the Museum für Naturkunde Berlin, Germany, consists of a near complete and isolated lower jaw, along with a partial snout and brain case. With the help of μCT data, Pusch et al (2020) described the endocranial anatomy of Lycosuchus vanderrieti.

<i>Theriognathus</i> Extinct genus of therapsids from late Permian South Africa and Tanzania

Theriognathus is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, known from fossils from South Africa, Zambia, and Tanzania. Theriognathus has been dated as existing during the Late Permian. Although Theriognathus means mammal jaw, the lower jaw is actually made up of several bones as seen in modern reptiles, in contrast to mammals. Theriognathus displayed many different reptilian and mammalian characteristics. For example, Theriognathus had canine teeth like mammals, and a secondary palate, multiple bones in the mandible, and a typical reptilian jaw joint, all characteristics of reptiles. It is speculated that Theriognathus was either carnivorous or omnivorous based on its teeth, and was suited to hunting small prey in undergrowth. This synapsid adopted a sleek profile of a mammalian predator, with a narrow snout and around 1 meter long. Theriognathus is represented by 56 specimens in the fossil record.

<i>Moschowhaitsia</i> Extinct genus of therapsid from the late Permian of Eurasia

Moschowhaitsia is an extinct genus of therocephalian therapsids from the Late Permian (Guadalupian) of Russia and China. The type species, Moschowhaitsia vjuschkovi, was discovered in the Changxingian-aged Archosaurus Assemblage Zone of Russia and named in 1963 by Russian palaeontologist Leonid Petrovich Tatarinov. A second species was discovered in Jingtai County of Gansu, China in 2020 and named as M. lidaqingi in 2023 by Jun Liu and Fernando Abdala, the first whaitsiid therocephalian to be discovered in China. It was among the larger carnivores in the faunal assemblages it occurred in, with a skull-length of up to 25 centimetres (9.8 in) in M. vjuschkovi and an even larger estimated 35 centimetres (14 in) for M. lidaqingi, one of the largest therocephalian skulls reported. The genus name Moschowhaitsia alludes to two other therocephalians, Moschorhinus and Whaitsia, due to the structure of its palate combining physical features of both these genera.

<i>Alopecognathus</i> Extinct genus of therapsids

Alopecognathus is an extinct genus of therocephalian therapsids from the Late Permian of South Africa.

<i>Glanosuchus</i> Extinct genus of therapsids

Glanosuchus is a genus of scylacosaurid therocephalian from the Late Permian of South Africa. The type species G. macrops was named by Robert Broom in 1904. Glanosuchus had a middle ear structure that was intermediate between that of early therapsids and mammals. Ridges in the nasal cavity of Glanosuchus suggest it had an at least partially endothermic metabolism similar to modern mammals.

<i>Scymnosaurus</i> Extinct genus of therapsids from middle Permian South Africa

Scymnosaurus is a dubious genus of therocephalian therapsids based upon various fossils of large early therocephalians. The genus was described by Robert Broom in 1903 with S. ferox, followed by S. watsoni in 1915 and a third, S. major, by Lieuwe Dirk Boonstra in 1954. Each of these species are considered nomen dubia today and based upon specimens belonging to two separate families of therocephalians. S. ferox and S. major represent specimens of Lycosuchidae incertae sedis, while S. watsoni is Scylacosauridae incertae sedis. Broom named a fourth species in 1907 from KwaZulu-Natal, S. warreni, though he later referred it to Moschorhinus as a valid species in 1932 but now is recognised as being synonymous with M. kitchingi.

Trochosuchus is a dubious genus of therocephalian therapsid from the middle Permian (Capitanian) of South Africa based on a weathered and poorly preserved undiagnostic fossil of a lycosuchid therocephalian. It includes the type and only species, T. acutus. Trochosuchus was named by palaeontologist Robert Broom in 1908 based on its supposedly unique proportions of the simulatenous 'double' functional canines thought to be characteristic of lycosuchids, with the pair in front being noticeably smaller than the second pair behind.

<i>Raranimus</i> Extinct genus of therapsids

Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.

<span class="mw-page-title-main">Akidnognathidae</span> Extinct family of therapsids

Akidnognathidae is an extinct family of therocephalian therapsids from the Late Permian and Early Triassic of South Africa, Russia and China. The family includes many large-bodied therocephalians that were probably carnivorous, including Moschorhinus and Olivierosuchus. One akidnognathid, Euchambersia, may even have been venomous. Akidnognathids have robust skulls with a pair of large caniniform teeth in their upper jaws. The family is morphologically intermediate between the more basal therocephalian group Scylacosauridae and the more derived group Baurioidea.

<span class="mw-page-title-main">Scylacosauridae</span> Extinct family of therapsids

Scylacosauridae is an extinct family of therocephalian therapsids. Scylacosaurids lived during the Permian period and were among the most basal therocephalians. The family was named by South African paleontologist Robert Broom in 1903. Scylacosaurids have long snouts and unusual saber-like canine teeth.

<i>Blattoidealestes</i> Extinct genus of therapsid from Middle-Permian South Africa

Blattoidealestes is a dubious genus of therocephalian, an extinct therapsid from the Middle Permian of South Africa. The type species Blattoidealestes gracilis was named by South African paleontologist Lieuwe Dirk Boonstra from the Tapinocephalus Assemblage Zone in 1954. Dating back to the Middle Permian, Blattoidealestes is one of the oldest therocephalians. It is similar in appearance to the small therocephalian Perplexisaurus from Russia, and may be closely related.

Silpholestes is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species Silpholestes jackae was named by South African paleontologist Robert Broom in 1948 from the Cistecephalus Assemblage Zone.

Lycideops is an extinct genus of therocephalians from the Late Permian of South Africa. The type species is Lycideops longiceps, named in 1931 by South African paleontologist Robert Broom. Fossils of Lycideops come from the Dicynodon Assemblage Zone of the Beaufort Group. Lycideops is a member of the family Lycideopidae. Like other lycideopids, Lycideops has a long snout.

<i>Simorhinella</i> Extinct genus of therapsids from the Late Permian of South Africa

Simorhinella is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. It is known from a single species, Simorhinella baini, named by South African paleontologist Robert Broom in 1915. Broom named it on the basis of a single fossil collected by the British Museum of Natural History in 1878 that included the skull and jaws from the eye sockets forward. The skull is unusual in that it has an extremely short and deep snout, unlike the longer and lower snouts of most other therocephalians. Because of the skull's distinctiveness, the classification of Simorhinella within Therocephalia based on the holotype was deemed to be uncertain. However, a 2014 study describing the skull of a much larger therocephalian identified the new specimen as an adult of Simorhinella, based on a bony crest on the vomer of the palate found in both specimens. Based on its anatomy, they proposed that Simorhinella was closely related to the basal therocephalian Lycosuchus and placed it in the family Lycosuchidae.

<i>Ictidosaurus</i> Genus of therapsid from the Middle Permian of South Africa

Ictidosaurus was a therapsid genus found in the Abrahamskraal Formation of South Africa, which lived during the middle Permian period. Fossils of the type species were found in the Tapinocephalus, and the base of the Eodicynodon assembly zones, of the Karoo Basin. Older classifications of the species, along with many other specimens found in the Iziko South African Museum archives, were originally classified within therocephalian family names, in this case the Ictidosauridae, which has been reclassified as belonging to the Scylacosauridae. The type species is I. angusticeps.

References

  1. 1 2 3 4 Abdala, F.; Kammerer, C. F.; Day, M. O.; Jirah, S.; Rubidge, B. S. (2014). "Adult morphology of the therocephalian Simorhinella bainifrom the middle Permian of South Africa and the taxonomy, paleobiogeography, and temporal distribution of the Lycosuchidae". Journal of Paleontology. 88 (6): 1139. doi:10.1666/13-186.
  2. 1 2 Kammerer, C. E. (2023). "Revision of the Scylacosauridae (Therapsida: Therocephalia)". Palaeontologia africana. 56: 51–87. ISSN   2410-4418.
  3. 1 2 Broom, R. (1908). "On the inter-relationships of the known Therocephalian genera". Annals of the South African Museum. 4: 369–372.
  4. 1 2 3 Van den Heever, J. A. (1980). "On the validity of the therocephalian family Lycosuchidae (Reptilia, Therapsida)". Annals of the South African Museum. 81: 111–125.
  5. 1 2 3 4 5 6 Van den Heever, J. (1987). The comparative and functional cranial morphology of the early Therocephalia (Amniota: Therapsida) (Ph.D. thesis). University of Stellenbosch.
  6. ↑ Van Den Hever, J. A. (1994). "The cranial anatomy of the early Therocephalia (Amniota: Therapsida)". Annals of the University of Stellenbosch. 1: 1–59.
  7. ↑ Romer, Alfred S. (1956). Osteology of the Reptiles. Chicago: University of Chicago Press. ISBN   978-0-89464-985-1.
  8. ↑ Romer, Alfred S. (1966). Vertebrate Paleontology (Third ed.). Chicago: University of Chicago Press. ISBN   978-0-7167-1822-2.
  9. ↑ Wyllie, Alistair (2003). "A review of Robert Broom's therapsid holotypes: have they survived the test of time" (PDF). Palaeontologia africana. 39: 1–19 – via CORE.
  10. 1 2 Liu, Jun; Abdala, Fernando (2019-02-22). "The tetrapod fauna of the upper Permian Naobaogou Formation of China: 3. Jiufengia jiai gen. et sp. nov., a large akidnognathid therocephalian". PeerJ. 7: e6463. doi: 10.7717/peerj.6463 . ISSN   2167-8359. PMC   6388668 . PMID   30809450.
  11. 1 2 Liu, J.; Abdala, F. (2023). "Late Permian terrestrial faunal connections invigorated: the first whaitsioid therocephalian from China". Palaeontologia africana. 56: 16–35. hdl: 10539/35706 .
  12. ↑ Suchkova, J.A.; Golubev, V.K. (2019). "New Permian therocephalian (Therocephalia, Theromorpha) from the Sundyr Assemblage of Eastern Europe". Paleontological Journal (4): 87–92. doi:10.1134/S0031031X19040123.
  13. ↑ Pusch, L. C.; Kammerer, C. F.; Fröbisch, J. (2024). "The origin and evolution of Cynodontia (Synapsida, Therapsida): Reassessment of the phylogeny and systematics of the earliest members of this clade using 3D-imaging technologies". The Anatomical Record. doi: 10.1002/ar.25394 . PMID   38444024.
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