Owenetta

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Owenetta
Temporal range: 260.5–250  Ma
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S
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Mid Wuchiapingian - early Induan
"Owenetta" kitchingorum.jpg
"Owenetta" kitchingorum
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Parareptilia
Order: Procolophonomorpha
Family: Owenettidae
Genus: Owenetta
Broom, 1939
Type species
Owenetta rubidgei
Broom, 1939
Synonyms
  • ?ColubriferCarroll, 1982
  • ?Colubrifer campiCarroll, 1982

Owenetta is an extinct genus of owenettid procolophonian parareptile. Fossils have been found from the Beaufort Group in the Karoo Basin of South Africa. Although most procolophonians lived during the Triassic, Owenetta existed during the Wuchiapingian and Changhsingian stages of the Late Permian as well as the early Induan stage of the Early Triassic. It is the type genus of the family Owenettidae, and can be distinguished from other related taxa in that the posterior portion of the supratemporal bears a lateral notch and that the pineal foramen is surrounded by a depressed parietal surface on the skull table.

Contents

Species

The type species of Owenetta is O. rubidgei. It is known from several skulls, but no postcranial skeleton. It was described in 1939 from a partial skull found from the Late Permian Cistecephalus Assemblage Zone of the Beaufort Group. [1] Several other localities, all from the overlying Dicynodon Assemblage Zone, have yielded the remainder of the known specimens.

The naming of a new species in 2002, O. kitchingorum, extended the temporal range of Owenetta into the Early Triassic, meaning that the genus had survived past the Permian–Triassic extinction event. [2] This new species was considered distinct from the type species based on features found from three nearly complete specimens that were present from the Lystrosaurus Assemblage Zone. Found in 1968, the first material of O. kitchingorum was a small block containing two skeletons in close proximity to one another (although at the time they were thought to be of the type species). [3] These skeletons provided much of the information used to distinguish O. kitchingorum from the type species. O. kitchingorum differed from O. rubidgei in that it possessed small postparietals on the posterior edge of the skull table and that the maxilla held no more than 20 teeth, some of which were caniniform. The best preserved specimen seems to be a subadult individual on the basis of features of the skull table.

A year after the new species of Owenetta was named, a paper proposed that it should be assigned to its own distinct genus, although a new name is yet to be provided. [4] A more recent paper also supported this polyphyly. [5] If this is the case, Owenetta is once again temporally restricted to the late Permian, and most likely died out at the end of the period as a result of the mass extinction event.

Later that year Colubrifer , named in 1982 from a specimen (UCMP 42773) found from the Early Triassic Lystrosaurus Assemblage Zone and thought to represent a short limbed lizard, was re-described. Based on a skull nearly identical to those known of Owenetta, it appears that the animal was a procolophonian almost certainly of that genus. It was found to be a junior synonym of Owenetta, but due to the poor preservation of its holotype, was reassigned Owenetta sp. [6]

Phylogenetics

When Owenetta was first named and described, it and other procolophonians were thought to be within Cotylosauria, a group that comprised what was believed to be the most primitive of reptiles. Cotylosauria has since been renamed Captorhinida, which is now thought to be a paraphyletic group anapsids and anapsid relatives. Owenetta and other procolophonians are now known to be within the subclass Parareptilia. It has later been placed within the family Nyctiphruretidae, but is currently placed within the family Owenettidae, of which it is the type genus. [7] [8] [9]

The well preserved, nearly complete specimens of Owenetta can be helpful in phylogenetic analyses of procolophonians and the parareptiles, which have recently undergone many great revisions. Although the postcranial skeleton is only known from immature individuals, comparisons can be made with related taxa such as Barasaurus , which is known from both immature and mature specimens, that resolve this morphology issue. Owenetta has been used in some phylogenetic analyses to uphold the traditional theory that the procolophonians were the ancestors of turtles, [10] although it now seems that turtles, if not Archosauromorpha, have evolved from parieasaurids [11] or even sauropterygians. [12]

Related Research Articles

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<i>Lystrosaurus</i> Genus of Late Permian and Early Triassic dicynodont therapsids

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<i>Milleretta</i> Extinct genus of reptiles

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<span class="mw-page-title-main">Parareptilia</span> Subclass of reptiles

Parareptilia ("near-reptiles") is a subclass or clade of basal sauropsids/reptiles, typically considered the sister taxon to Eureptilia. Parareptiles first arose near the end of the Carboniferous period and achieved their highest diversity during the Permian period. Several ecological innovations were first accomplished by parareptiles among reptiles. These include the first reptiles to return to marine ecosystems (mesosaurs), the first bipedal reptiles, the first reptiles with advanced hearing systems, and the first large herbivorous reptiles. The only parareptiles to survive into the Triassic period were the procolophonoids, a group of small generalists, omnivores, and herbivores. The largest family of procolophonoids, the procolophonids, rediversified in the Triassic, but subsequently declined and became extinct by the end of the period.

<span class="mw-page-title-main">Procolophonia</span> Extinct suborder of reptiles

Procolophonia is an extinct suborder (clade) of herbivorous reptiles that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the Cotylosauria but are now considered a clade of Parareptilia. They are closely related to other generally lizard-like Permian reptiles such as the Millerettidae, Bolosauridae, Acleistorhinidae, and Lanthanosuchidae, all of which are included under the Anapsida or "Parareptiles".

<span class="mw-page-title-main">Procolophonomorpha</span> Order of reptiles (fossil)

Procolophonomorpha is an order or clade containing most parareptiles. Many papers have applied various definitions to the name, though most of these definitions have since been considered synonymous with modern parareptile clades such as Ankyramorpha and Procolophonia. The current definition of Procolophonomorpha, as defined by Modesto, Scott, & Reisz (2009), is that of as a stem-based group containing Procolophon and all taxa more closely related to it than to Milleretta. It constitutes a diverse assemblage that includes a number of lizard-like forms, as well as more diverse types such as the pareiasaurs. Lee 1995, 1996, 1997 argues that turtles evolved from pareiasaurs, but this view is no longer considered likely. Rieppel and deBraga 1996 and deBraga and Rieppel, 1997 argue that turtles evolved from sauropterygians, and there is both molecular and fossil (Pappochelys) evidence for the origin of turtles among diapsid reptiles.

<i>Proterosuchus</i> Extinct genus of reptiles from the Early Triassic of South Africa

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<i>Daptocephalus</i> Assemblage Zone

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<i>Lystrosaurus</i> Assemblage Zone

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<i>Procolophon</i> Extinct genus of reptiles

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<i>Macroleter</i> Extinct genus of reptiles

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<i>Eunotosaurus</i> Extinct genus of reptiles

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<i>Acleistorhinus</i> Extinct genus of reptiles

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<span class="mw-page-title-main">Owenettidae</span> Extinct family of reptiles

Owenettidae is an extinct family of procolophonian parareptiles. Fossils have been found primarily from Africa and Madagascar, with one genus present from South America. It is the sister taxon to the family Procolophonidae. Modesto and Damiani (2007) defined Owenettidae as a stem-based group including Owenetta rubidgei and all species closely related to it than to Procolophon trigoniceps.

<span class="mw-page-title-main">Procolophonoidea</span> Extinct superfamily of reptiles

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<i>Microleter</i> Extinct genus of reptiles

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Barasaurus is an extinct genus of owenettid procolophonoid parareptile known from the Late Permian and Early Triassic of Madagascar. It contains a single species, Barasaurus besairiei.

Saurodektes is an extinct genus of owenettid procolophonoid parareptile known from the earliest Triassic deposits of Eastern Cape Province, South Africa. It was first named by Sean P. Modesto, Ross J. Damiani, Johann Neveling and Adam M. Yates in 2003 and the type species is Saurodectes rogersorum. The generic name Saurodectes was preoccupied by the generic name of Saurodectes vrsanskyi Rasnitsyn & Zherikhin, 2000, a fossil chewing lice known from the Early Cretaceous of Russia. Thus, an alternative generic name, Saurodektes, was proposed by Modesto et al. in 2004. The generic name means "lizard", sauros, and "biter", dektes from Greek. The specific name, rogersorum, honors Richard and Jenny Rogers, owners of the farm Barendskraal, for their hospitality, support and interest in the work of the paleontologists who recovered the holotype. Saurodektes is known solely from the holotype BP/1/6025, a partial skull and some fragmentary partial postcranial elements, housed at the Bernard Price Institute for Palaeontological Research, although the unprepared specimens BP/1/6044, BP/1/6045 and BP/1/6047 might also be referable to it. All specimens were collected on the slopes of the Manhaar Hill at Barendskraal in the Middelburg District, from the Palingkloof Member of the Balfour Formation, Beaufort Group, only 12 metres below the base of the Katberg Formation. This horizon belongs to the Lystrosaurus Assemblage Zone, dating to the early Induan stage of the Early Triassic period.

References

  1. Broom, R. (1939). A new type of cotylosaurian, Owenetta rubidgei. Annals of the Transvaal Museum19:319–321.
  2. Reisz, R. R. and Scott, D. (2002). Owenetta kitchingorum, sp. nov., a small parareptile (Procolophonia: Owenettidae) from the Lower Triassic of South Africa. Journal of Vertebrate Paleontology22(2):244-256.
  3. Gow, C. E. (1977). Owenetta in perspective. Palaeontologica Africana20:115–118.
  4. Modesto, S. P., Damiani, R. J., Neveling, J. and Yates, A. M. (2003). A new Triassic owenettid parareptile and the Mother of Mass Extinctions. Journal of Vertebrate Paleontology23(3):715–719.
  5. Modesto, S. P. and Damiani, R. (2007). The Procolophonoid Reptile Sauropareion anoplus from the Lowermost Triassic of South Africa. Journal of Vertebrate Paleontology27(2):337-349
  6. Evans, S. E. (2001). "The Early Triassic 'lizard' Colubrifer Campi: A Reassessment". Palaeontology. 44 (5): 1033–1041. Bibcode:2001Palgy..44.1033E. doi: 10.1111/1475-4983.00214 .
  7. Lee, M. S. Y. (1995). Historical burden in systematics and the interrelationships of parareptiles. Biological Reviews70(3):459-547.
  8. deBraga, M. and Reisz, R. (1996). The Early Permian reptile Acleistorhinus pteroticus and its phylogenetic position. Journal of Vertebrate Paleontology16(3):384-395
  9. Säilä, L. K. (2008). The osteology and affinities of Anomoiodon liliensterni, a procolophonid reptile from the Lower Triassic Buntsandstein of Germany. Journal of Vertebrate Paleontology28(4):1199-1205
  10. Reisz, R. R. and Laurin, M. (1991). Owenetta and the origin of turtles. Nature349:324-326.
  11. Lee, M. S. Y. (1997). Pareiasaur phylogeny and the origin of turtles. Zoological Journal of the Linnean Society120:197-280
  12. Rieppel, O. and deBraga, M. (1996). Turtles as diapsid reptiles. Nature384:453-455.