Lydekkerina
Encyclopedia
Lydekkerina is an extinct genus
of stereospondyl temnospondyl. It is the type genus
of the family Lydekkerinidae
. Fossils have been collected from Early Triassic
deposits in South Africa
and Australia
. The type species
is L. huxleyi, first described in 1889. While most other stereospondyls were semiaquatic, Lydekkerina was exclusively terrestrial.
Lydekkerina can be distinguished from other lydekkerinids on the basis of several skull characteristics. One such feature is the presence of vomer
ine shagreen, tiny bumps covering the bones of the palate. An opening at the tip of the palate called the anterior palatal vacuity is divided by two projections of the skull roof, a second distinctive feature of the genus. Moreover, distinctive ridges are present on the underside of the skull roof
around the eye sockets, probably to provide structural support.
by Richard Lydekker
in 1889. The specific name honors Thomas Henry Huxley, an English
biologist
who named the genus Bothriceps in 1859 from material in Australia. Robert Broom
, a South African paleontologist, provided a more accurate description of the species in 1915 and reassigned it to the new genus Lydekkerina, named after Lydekker.
Lydekkerina is one of the most common temnospondyls found from the Permo-Triassic Karoo Basin of South Africa. Many fossils have been found from the Lystrosaurus Assemblage Zone
of the Beaufort Group
. Many, however, are poorly preserved, being crushed or deformed. The variable conditions of specimens has resulted in confusion in identification. Some paleontologists have proposed that variations in skull shape among specimens represent deformities rather than true morphologies. Therefore, characteristics that distinguish different lydekkerinids from one another may be the results of preservation, not taxonomic distinctness. In 2006, it was proposed that the South African lydekkerinids Limnoiketes
and Broomulus
were synonymous with Lydekkerina for this reason.
A second species of Lydekkerina, L. putterilli, was named by Broom in 1930. Its description was based on a small partial skull from the Permian
Dicynodon Assemblage Zone
. It was later considered to be a juvenile rhinesuchid
related to Uranocentrodon
. In 2000, L. putterilli was assigned to its own genus, Broomistega
.
Broom described a third species, L. kitchingi, from the Dicynodon Assemblage Zone in 1950. In 1996 it was reassigned as a juvenile form of the rhinesuchid Muchocephalus
. In 2003, both L. kitchingi and Muchocephalus were synonymized with Laccosaurus
.
Temnospondyl remains from the Early Triassic Rewan Formation of Queensland
, Australia, were described in 2006 and assigned to Lydekkerina huxleyi. These remains possess characters diagnostic of Lydekkerina such as the ridges underneath the skull roof and the vomerine shagreen.
across the skull is poorly developed, suggesting that Lydekkerina had little use for these organs in a land environment. The skeleton of Lydekkerina is similar to those of early stereospondyl relatives such as the archegosauroids
, but bears little resemblance to those of the exclusively terrestrial Permian temnospondyls.
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 stereospondyl temnospondyl. 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 Lydekkerinidae
Lydekkerinidae
Lydekkerinidae is a family of stereospondyl temnospondyls that lived in the Triassic period. During the Triassic, lydekkerinids had a global distribution. They were small-bodied with wedge-shaped, roughly triangular heads. Fossils have been found in Russia, Greenland, India, South Africa,...
. Fossils have been collected from 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...
deposits in 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...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The type species
Type 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...
is L. huxleyi, first described in 1889. While most other stereospondyls were semiaquatic, Lydekkerina was exclusively terrestrial.
Description
Lydekkerina was a relatively small temnospondyl, growing up to around 1 metres (3.3 ft) in length. Skulls range in length from 49 millimetres (1.9 in) in the smallest known individual to up to 100 millimetres (3.9 in) in larger individuals. The skull is wedge-shaped and has a parabolic outline with convex lateral margins. Shallow pits cover the surface of the skull. Teeth line the palate as well as the jaws, and some skulls even bear large ectopterygoid tusks on the underside of the skull.Lydekkerina can be distinguished from other lydekkerinids on the basis of several skull characteristics. One such feature is the presence of vomer
Vomer
The vomer is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.-Biology:...
ine shagreen, tiny bumps covering the bones of the palate. An opening at the tip of the palate called the anterior palatal vacuity is divided by two projections of the skull roof, a second distinctive feature of the genus. Moreover, distinctive ridges are present on the underside of the skull roof
Skull roof
The skull roof , or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land living vertebrates. The bones are derived from dermal bone, hence the alternative name dermatocranium...
around the eye sockets, probably to provide structural support.
History and classification
Lydekkerina huxleyi was first briefly described as a species of BothricepsBothriceps
Bothriceps is an extinct genus of stereospondyl temnospondyl. It is a member of the infraorder Trematosauria and is the most basal brachyopomorph known. It is one of the only brachyopomorph that lies outside the superfamily Brachyopoidea, which includes the families Brachyopidae and Chigutisauridae...
by Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
in 1889. The specific name honors Thomas Henry Huxley, an English
English people
The English are a nation and ethnic group native to England, who speak English. The English identity is of early mediaeval origin, when they were known in Old English as the Anglecynn. England is now a country of the United Kingdom, and the majority of English people in England are British Citizens...
biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...
who named the genus Bothriceps in 1859 from material in Australia. Robert Broom
Robert Broom
Professor Robert Broom was a Scottish South African doctor and paleontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow...
, a South African paleontologist, provided a more accurate description of the species in 1915 and reassigned it to the new genus Lydekkerina, named after Lydekker.
Lydekkerina is one of the most common temnospondyls found from the Permo-Triassic Karoo Basin of South Africa. Many fossils have been found 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....
of 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...
. Many, however, are poorly preserved, being crushed or deformed. The variable conditions of specimens has resulted in confusion in identification. Some paleontologists have proposed that variations in skull shape among specimens represent deformities rather than true morphologies. Therefore, characteristics that distinguish different lydekkerinids from one another may be the results of preservation, not taxonomic distinctness. In 2006, it was proposed that the South African lydekkerinids Limnoiketes
Limnoiketes
Limnoiketes is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...
and Broomulus
Broomulus
Broomulus is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...
were synonymous with Lydekkerina for this reason.
A second species of Lydekkerina, L. putterilli, was named by Broom in 1930. Its description was based on a small partial skull from the 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...
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....
. It was later considered to be a juvenile rhinesuchid
Rhinesuchidae
Rhinesuchidae is a family of Temnospondyli that lived in the Permian and Triassic period.-External links:*...
related to Uranocentrodon
Uranocentrodon
Uranocentrodon is an extinct genus of the family Rhinesuchidae....
. In 2000, L. putterilli was assigned to its own genus, Broomistega
Broomistega
Broomistega is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...
.
Broom described a third species, L. kitchingi, from the Dicynodon Assemblage Zone in 1950. In 1996 it was reassigned as a juvenile form of the rhinesuchid Muchocephalus
Muchocephalus
Muchocephalus is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...
. In 2003, both L. kitchingi and Muchocephalus were synonymized with Laccosaurus
Laccosaurus
Laccosaurus is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...
.
Temnospondyl remains from the Early Triassic Rewan Formation of Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, Australia, were described in 2006 and assigned to Lydekkerina huxleyi. These remains possess characters diagnostic of Lydekkerina such as the ridges underneath the skull roof and the vomerine shagreen.
Paleobiology
Because the bones of Lydekkerina are more heavily ossified than other stereospondyls, it is thought to have been terrestrial. Large bony projections on the skeleton likely served as attachments for strong muscles. Joints between bones were well-developed, enabling effective locomotion on land. The sensory system of pressure-sensitive sulciSulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
across the skull is poorly developed, suggesting that Lydekkerina had little use for these organs in a land environment. The skeleton of Lydekkerina is similar to those of early stereospondyl relatives such as the archegosauroids
Archegosauroidea
Archegosauroidea is an extinct superfamily of Permian temnospondyls. The superfamily is assigned to the clade Stereospondylomorpha and is the sister taxon to the suborder Stereospondyli. It includes the families Actinodontidae and Archegosauridae, and possibly the genus Intasuchus, which is placed...
, but bears little resemblance to those of the exclusively terrestrial Permian temnospondyls.