Koolasuchus | |
---|---|
Holotype mandibles | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Order: | † Temnospondyli |
Suborder: | † Stereospondyli |
Family: | † Chigutisauridae |
Genus: | † Koolasuchus Warren et al., 1997 |
Type species | |
†Koolasuchus cleelandi Warren et al., 1997 |
Koolasuchus is an extinct genus of brachyopoid temnospondyl in the family Chigutisauridae. Fossils have been found from Victoria, Australia and date back 125-120 million years ago to Barremian-Aptian stages of the Early Cretaceous. Koolasuchus is the youngest known temnospondyl. It is known from several fragments of the skull and other bones such as vertebrae, ribs, and pectoral elements. The type species Koolasuchus cleelandi was named in 1997. K. cleelandi was adopted as the fossil emblem for the state of Victoria, Australia on 13 January 2022. [1]
The first fossil of temnospondyls found in the Strzelecki Group was NMV-PI56988, the posterior fragment of a jaw, collected around 1980. The jaw fragment was first mentioned in a 1986 publication by Anne Warren and R. Jupp, who did not definitively identify it as that of a temnospondyl due to the Cretaceous age of the specimen, much younger than any other known temnospondyl specimen at the time. [2] In 1991, additional remains were reported including NMV-PI86040, an intercentrum (part of the vertebra) and NMV-PI86101, an isolated skull roof bone, likely representing either a frontal, a supratemporal or a parietal. The intercentrum unquestionably confirmed that temnospondyls were present in the Strzelecki Group. The morphology of the skull roof bone lead to the authors suggesting that the temnospondyl was either a member of Plagiosauridae or Brachyopoidea. [3]
Koolasuchus was named in 1997 from the Aptian aged Wonthaggi Formation of Strzelecki Group in Victoria. [4] It is known from four fragments of the lower jaw and several postcranial bones, including ribs, vertebrae, a fibula, and parts of the pectoral girdle. A jawbone was found in 1978 in a fossil site known as the Punch Bowl near the town of San Remo. Later specimens were found in 1989 on the nearby Rowell's Beach. A partial skull is also known but has not been fully prepared. Koolasuchus was named for the palaeontologist Lesley Kool. The name is also a pun on the word "cool" in reference to the cold climate of its environment. [5] The type species K. cleelandi is named after geologist Mike Cleeland. [6]
Koolasuchus was a large, aquatic temnospondyl, measuring up to 3 metres (9.8 ft) in length and weighing up to 500 kilograms (1,100 lb). [7] [8] [9] Like other chigutisaurids, it had a wide, rounded head and tabular horns projecting from the back of the skull. [10] Although represented by incomplete material, the skull was likely 65 centimetres (26 in) long. [11]
Koolasuchus is distinguished from other temnospondyls aside from Siderops and Hadrokkosaurus by having the ramus of the mandible "articular is excluded from the dorsal surface of the postglenoid area by a suture between the surangular and the prearticular", and is distinguished from those two taxa by a lack of coronoid teeth. [4]
Koolasuchus inhabited rift valleys in southern Australia during the Early Cretaceous. During this time the area was below the Antarctic Circle, and temperatures were relatively cool for the Mesozoic. Based on the coarse-grained rocks in which remains were found, Koolasuchus likely lived in fast-moving streams. As a large aquatic predator, it was similar in lifestyle to crocodilians. Although eusuchians and kin were common during the Early Cretaceous, they were absent from southern Australia 120 million years ago, possibly because of the cold climate. By 110 Mya, represented by rocks in the Dinosaur Cove fossil locality, temperatures had warmed and crocodilians had returned to the area. These crocodilians likely displaced Koolasuchus, leading to its disappearance in younger rocks. [5]
"Labyrinthodontia" is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras. Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group (clade) exclusive of other tetrapods. Instead, they consistute an evolutionary grade, ancestral to living tetrapods such as lissamphibians and amniotes. "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time.
Temnospondyli or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent. A few species continued into the Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amphibians, many had characteristics such as scales and large armour-like bony plates (osteoderms) that generally distinguish them from the modern soft-bodied lissamphibians.
Dendrerpeton is a genus of an extinct group of temnospondyl amphibians. Its fossils have been found primarily in the Joggins Formation of Eastern Canada and in Ireland. It lived during the Carboniferous and is said to be around 309–316 million years of age, corresponding to more specifically the Westphalian (stage) age. Of terrestrial temnospondyl amphibians evolution, it represents the first stage. Although multiple species have been proposed, the species unanimously recognized is D. acadianum. This species name comes from “Acadia” which is a historical name for the Nova Scotia region as a French colony. It refers to the location of the coal field at which the fossil was found.
The Stereospondyli are a group of extinct temnospondyl amphibians that existed primarily during the Mesozoic period. They are known from all seven continents and were common components of many Triassic ecosystems, likely filling a similar ecological niche to modern crocodilians prior to the diversification of pseudosuchian archosaurs.
Eryosuchus is an extinct genus of capitosauroid temnospondyl from the Middle Triassic of northern Russia. It was a very large predator: the largest specimen known could reach up to 3.5 m (11.5 ft) in length, with a skull over 1 m long.
Cyclotosaurus is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an amphibian, had an elongated skull up to 56 cm (22 in).
Chigutisauridae is an extinct family of large temnospondyls. The only genera recognized as belonging to Chigutisauridae at the current time are all from Gondwana. Chigutisaurids first appeared during the Early Triassic in Australia. During the Late Triassic they became widely distributed in Gondwana, with fossils found in South Africa, India and South America. Koolasuchus from the Early Cretaceous of Australia represents the youngest known temnospondyl.
Siderops is an extinct genus of chigutisaurid temnospondyl from Early Jurassic of Australia, containing the species S. kehli.
Brachyopoidea is a superfamily of temnospondyls that lived during the Mesozoic. It contains the families Brachyopidae and Chigutisauridae. The earliest records of brachyopids are from the Lower Triassic in Australia. The latest-surviving member of the superfamily is the chigutisaurid Koolasuchus from the Early Cretaceous of Australia.
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.
Mastodonsauridae is a family of capitosauroid temnospondyls. Fossils belonging to this family have been found in North America, Greenland, Europe, Asia, and Australia. The family Capitosauridae is synonymous with Mastodonsauridae.
Limnarchia is a clade of temnospondyls. It includes the mostly Carboniferous-Permian age Dvinosauria and the mostly Permian-Triassic age Stereospondylomorpha. The clade was named in a 2000 phylogenetic analysis of stereospondyls and their relatives. Limnarchia means "lake rulers" in Greek, in reference to their aquatic lifestyles and long existence over a span of approximately 200 million years from the Late Carboniferous to the Early Cretaceous. In phylogenetic terms, Limnarchia is a stem-based taxon including all temnospondyls more closely related to Parotosuchus than to Eryops. It is the sister group of the clade Euskelia, which is all temnospondyls more closely related to Eryops than to Parotosuchus. Limnarchians represent an evolutionary radiation of temnospondyls into aquatic environments, while euskelians represent a radiation into terrestrial environments. While many euskelians were adapted to life on land with strong limbs and bony scutes, most limnarchians were better adapted for the water with poorly developed limbs and lateral line sensory systems in their skulls.
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.
Keratobrachyops is an extinct genus of trematosaurian temnospondyl found in the Arcadia Formation of Queensland, Australia. It had been thought to be a basal chigutisaurid but is now thought to be a basal brachyopomorph closely related to the genus Bothriceps, and may even be a synonym of it.
Kourerpeton is an extinct genus of dvinosaurian temnospondyl. Fossils of Kourerpeton were discovered in a window of a barber's shop in either Bisbee or Mesa, Arizona. Kourerpeton was named in 1976, with the type and only species being K. bradyi. It was originally assigned to the monotypic family Kourerpetidae, which has been alternatively spelled Kourerpetontidae.
Reptiles arose about 320 million years ago during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds that are descended from early traditionally-defined reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.
Vigilius is an extinct genus of brachyopid temnospondyl amphibian from the Triassic of Arizona. It is known from the single type species Vigilius wellesi.
Diluvicursor is a genus of small ornithischian from the Lower Albian of Australia. It is known from one species, the type species D. pickeringi. The two known specimens, a vertebra and a partial juvenile postcranium discovered in 2005 from the Eumeralla Formation, are known, and they were named in early 2018.
Galleonosaurus is a genus of basal ornithopod dinosaur from the Wonthaggi Formation of the Gippsland region of Victoria, Australia. The type and only species is Galleonosaurus dorisae.
Arenaerpeton is an extinct genus of chigutisaurid temnospondyl found in the Terrigal Formation of New South Wales, Australia. The type species is A. supinatus. The genus name is derived from the Latin "Arena", meaning "sand" ; and "erpeton" meaning thing that creeps. The species name "supinatus" means "supine", referring to the fact that the fossil is lying on its back.