Eolydekkerina

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Eolydekkerina
Temporal range: Early Triassic
Eolydekkerina magna.jpg
Restoration of Eolydekkerina magna
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Temnospondyli
Suborder: Stereospondyli
Family: Lydekkerinidae
Genus: Eolydekkerina
Shishkin et al., 1996
Type species
Eolydekkerina magna
Shishkin et al., 1996

Eolydekkerina is an extinct genus of temnospondyl from the Early Triassic of South Africa. It belongs to the family Lydekkerinidae, along with the closely related genus Lydekkerina . It is known from a single type species, Eolydekkerina magna, which was named in 1996 from a part of the Beaufort Group called the Lystrosaurus Assemblage Zone. [1]

Contents

Description

Eolydekkerina is known from two specimens: a skull lacking the lower jaws and a poorly lower jaw, not associated with the skull. At 13 centimetres (5.1 in) in length, the skull of Eolydekkerina is larger than that of any Lydekkerina specimen. The snout is proportionally much longer, and the eye sockets are placed farther apart than they are in Lydekkerina. The proportions of the skull in Eolydekkerina are similar to those of the Australian lydekkerinid genus Chomatobatrachus . However, Eolydekkerina shares more features in common with Lydekkerina, including the nearly identical shape of bones at the back of the skull. The skull is roughly triangular in shape when viewed from above, with straight side margins. The margins of the eye socket are raised and the middle of the snout is slightly indented. Shallow grooves run along the surface of the skull behind the eye sockets and below the nostril openings. [1]

The lengthened skull of Eolydekkerina, while different from that of Lydekkerina, is similar to those of the related rhinesuchids and capitosaurians. The short skull of Lydekkerina is thought to be a derived or advanced characteristic, suggesting that Lydekkerina evolved from a more typical longer-skulled temnospondyl. Since temnospondyl skulls tend to lengthen as individuals of a species age, the skull of Lydekkerina may represent a juvenile form, while the skull of Eolydekkerina represents a fully-grown adult form. If Lydekkerina is the descendant of Eolydekkerina, it likely evolved by retaining juvenile characteristics into adulthood in a condition known as paedomorphosis. [1]

Paleoenvironment

Remains of Eolydekkerina were found in the lower part of the Lystrosaurus Assemblage Zone, a deposit that preserves very few amphibians. Amphibians become more numerous in younger parts of the Lystrosaurus Assemblage Zone with most specimens attributable to either Lydekkerina or to the dissorophoid Micropholis . Several species of the family Rhytidosteidae have also been identified from the upper part of the Lystrosaurus Assemblage Zone. When fossils of Eolydekkerina were first found, they were thought to belong to a rhytidosteid, as a rhytidosteid called Pneumatostega had already been found in this part of the assemblage zone.

The lower Lystrosaurus Assemblage Zone is dominated by the synapsid Lystrosaurus , as well as reptiles such as Owenetta and Proterosuchus . Most small-bodied lydekkerinids such as Lydekkerina are found in this type of assemblage. Lydekkerinids of similar size to Eolydekkerina (such as Chomatobatrachus) are usually found in amphibian-dominated assemblages where Lystrosaurus is not present. Therefore, the presence of Eolydekkerina in a reptile-dominated environment is unusual. [1]

Related Research Articles

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Lystrosaurus is an extinct genus of herbivorous dicynodont therapsids from the late Permian and Early Triassic epochs. It lived in what is now Antarctica, India, China, Mongolia, European Russia and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. They ranged in size from that of a small dog to 8 feet long.

<i>Ericiolacerta</i> Extinct genus of therapsid from the early Triassic

Ericiolacerta is an extinct genus of small therocephalian therapsids from the early Triassic of South Africa and Antarctica. Ericiolacerta, meaning "hedgehog lizard", was named by D.M.S. Watson in 1931. The species E. parva is known from the holotype specimen which consists of a nearly complete skeleton found in the Lystrosaurus Assemblage Zone within the Katberg Formation of the Beaufort Group in South Africa, and from a partial jaw found in the Lower Triassic Fremouw Formation in Antarctica. Ericiolacerta was around 20 centimetres (7.9 in) in length, with long limbs and relatively small teeth. It probably ate insects and other small invertebrates. The therocephalians – therapsids with mammal-like heads – were abundant in Permian times, but only a few made it into the Triassic. Ericiolacerta was one of those. It is possible that they gave rise to the cynodonts, the only therapsid group to survive into post-Triassic times. Cynodonts gave rise to mammals.

<span class="mw-page-title-main">Lydekkerinidae</span> Extinct family of temnospondyls

Lydekkerinidae is a family of stereospondyl temnospondyls that lived in the Early Triassic period. During this time period, lydekkerinids were widely distributed, with putative remains reported from Russia, Greenland, India, South Africa, Madagascar, Australia, and Antarctica. In contrast to most other stereospondyls, lydekkerinids were relatively small-bodied. The type genus is Lydekkerina, the namesake of the family and the best-known lydekkerinid.

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<i>Micropholis</i> (amphibian) Extinct genus of amphibian from the early Triassic of South Africa

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

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<span class="mw-page-title-main">Derwentiinae</span> Extinct subfamily of amphibians

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<i>Warrenisuchus</i> Extinct genus of temnospondyls

Warrenisuchus is an extinct genus of temnospondyl from the Early Triassic of Queensland, Australia. It belongs to a diverse group of Triassic temnospondyls called Capitosauria. The type species Warrenisuchus aliciae was erected in 2009. W. aliciae was originally described as a species of Parotosuchus in 1988, which is known from other species that have been found in Europe, Africa, and Antarctica. In 2000 it was then assigned to a new genus called Rewanobatrachus along with the newly named species R. gunganj, which was declared the type species of the genus. However, R. gunganj was later reclassified as a species of Watsonisuchus, invalidating the name Rewanobatrachus and requiring that R. aliciae be placed in its own genus, which was named Warrenisuchus. However, several studies suggest that Warrenisuchus aliciae may be a species of Watsonisuchus as well. Unlike most capitosaurs, Warrenisuchus is known from many juvenile skulls less than 4 centimetres (1.6 in) in length.

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

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Latiscopus disjunctus is a small Late Triassic temnospondyl collected in 1940 by a Works Projects Administration crew working near Otis Chalk, Texas that was described by John Wilson in 1948.

<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.

Vetusodon is an extinct genus of cynodonts belonging to the clade Epicynodontia. It contains one species, Vetusodon elikhulu, which is known from four specimens found in the Late Permian Daptocephalus Assemblage Zone of South Africa. With a skull length of about 18 centimetres (7.1 in), Vetusodon is the largest known cynodont from the Permian. Through convergent evolution, it possessed several unusual features reminiscent of the contemporary therocephalian Moschorhinus, including broad, robust jaws, large incisors and canines, and small, single-cusped postcanine teeth.

References

  1. 1 2 3 4 Shishkin, M. A.; Rubidge, B. S.; Kitching, J. W. (1996). "A New Lydekkerinid (Amphibia, Temnospondyli) from the Lower Triassic of South Africa: Implications for Evolution of the Early Capitosauroid Cranial Pattern". Philosophical Transactions of the Royal Society B: Biological Sciences. 351 (1347): 1635. doi:10.1098/rstb.1996.0147.