Owenetta
Encyclopedia
Owenetta is an extinct genus
of basal
procolophonia
n parareptile. Fossil
s 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.
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. 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. 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). 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. A more recent paper also supported this polyphyly
. 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 the short limbed lizard
Colubrifer campi, named in 1982 from a specimen found from the Early Triassic Lystrosaurus Assemblage Zone, was reassigned to the genus Owenetta. Based on a skull nearly identical to those known of Owenetta, it appears that the animal was almost certainly a procolophonian of that genus. This suggests that Owenetta did in fact survive the mass extinction event at the end of the Permian.
, which is now thought to be a paraphyletic group anapsid
s 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.
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, although it now seems that turtles have evolved from parieasaurids or even sauropterygia
ns.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
procolophonia
Procolophonia
The Procolophonia are a suborder 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...
n parareptile. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s have been found from the Beaufort Group
Beaufort Group
The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup of geological strata in Southern Africa. It follows conformably after the Ecca Group and consists essentially of sandstones and shales, deposited in the Karoo Basin from the Middle Permian to the early part of the...
in the Karoo Basin
Karoo
The Karoo is a semi-desert region of South Africa. It has two main sub-regions - the Great Karoo in the north and the Little Karoo in the south. The 'High' Karoo is one of the distinct physiographic provinces of the larger South African Platform division.-Great Karoo:The Great Karoo has an area of...
of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Although most procolophonians lived during the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
, Owenetta existed during the Wuchiapingian
Wuchiapingian
In the geologic timescale, the Wuchiapingian or Wujiapingian is an age or stage of the Permian. It is also the lower or earlier of two subdivisions of the Lopingian epoch or series. The Wuchiapingian spans the time between 260.4 ± 0.7 and 253.8 ± 0.7 million years ago...
and Changhsingian
Changhsingian
In the geologic timescale, the Changhsingian or Changxingian is the latest age or uppermost stage of the Permian. It is also the upper or latest of two subdivisions of the Lopingian epoch or series. The Changhsingian lasted from 253.8 ± 0.7 to 251.0 ± 0.7 million years ago...
stages of the Late Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
as well as the early Induan
Induan
The Induan is, in the geologic timescale, the first age of the Early Triassic epoch or the lowest stage of the Lower Triassic series. It spans the time between 251 ± 0.4 Ma and 249.7 ± 0.7 Ma...
stage of the Early Triassic
Early Triassic
The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy...
. It is the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Owenettidae
Owenettidae
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....
, 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
Parietal bone
The parietal bones are bones in the human skull which, when joined together, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin pariet-, wall....
surface on the skull table.
Species
The type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the 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
Cistecephalus Assemblage Zone
The Cistecephalus Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Cistecephalus, a genus of small burrowing, mole-like reptile, whose fossils have been found in that structure....
of the Beaufort Group. Several other localities, all from the overlying Dicynodon Assemblage Zone
Dicynodon Assemblage Zone
The Dicynodon Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Dicynodon, a genus of mammal-like reptile, that flourished in the Permian Period and whose fossils have been found in that structure....
, 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. 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
Lystrosaurus Assemblage Zone
The Lystrosaurus Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Lystrosaurus, a genus of mammal-like reptile, a dominant life form of the Early Triassic Period, whose fossils have been found in that structure....
. 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). 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
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
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. A more recent paper also supported this polyphyly
Polyphyly
A polyphyletic group is one whose members' last common ancestor is not a member of the group.For example, the group consisting of warm-blooded animals is polyphyletic, because it contains both mammals and birds, but the most recent common ancestor of mammals and birds was cold-blooded...
. 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 the short limbed lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
Colubrifer campi, named in 1982 from a specimen found from the Early Triassic Lystrosaurus Assemblage Zone, was reassigned to the genus Owenetta. Based on a skull nearly identical to those known of Owenetta, it appears that the animal was almost certainly a procolophonian of that genus. This suggests that Owenetta did in fact survive the mass extinction event at the end of the Permian.
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 CaptorhinidaCaptorhinida
Captorhinida is a doubly paraphyletic grouping of early reptiles. Robert L. Carroll ranked it as an order in the subclass Anapsida, composed of the following suborders:...
, which is now thought to be a paraphyletic group anapsid
Anapsid
An anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...
s and anapsid relatives. Owenetta and other procolophonians are now known to be within the subclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
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.
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, although it now seems that turtles have evolved from parieasaurids or even sauropterygia
Sauropterygia
Sauropterygia were a group of very successful aquatic reptiles that flourished during the Mesozoic before they became extinct at the end of the era. They were united by a radical adaptation of their shoulder, designed to support powerful flipper strokes...
ns.
External links
- Owenetta in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...