Sclerocephalus Temporal range: Late Carboniferous – Early Permian, | |
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One of the best preserved fossil skeletons of Sclerocephalus haeuseri | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Amphibia |
Order: | † Temnospondyli |
Family: | † Sclerocephalidae Jaekel, 1909 |
Genus: | † Sclerocephalus Goldfuss, 1847 |
Species | |
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Synonyms | |
Genus-level:
Species-level:
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Sclerocephalus is an extinct genus of temnospondyl amphibian from the lowermost Permian of Germany and Czech Republic with four valid species, including the type species S. haeuseri. It is one of the most completely preserved and most abundant Palaeozoic tetrapods. Sclerocephalus was once thought to be closely related to eryopoid temnospondyls, but it is now thought to be more closely related to archegosauroids. It is the only genus in the family Sclerocephalidae.
The adults animals reached a body length of ca. 150 cm, and had an elongate trunk and a laterally compressed tail. In some specimens lateral line sulci are retained. These body features suggest an aquatic mode of life, with aquatic larvae that probably breathed with external gills like modern tadpoles, while the adults breathed with lungs. Sclerocephalus underwent significant changes during its ontogeny, for example the eyes are much larger and the tail much longer in larvae than in adults. The latest revision, redescription and phylogenetic study of this genus was provided by Schoch & Witzmann (2009).
Sclerocephalus was often classified within the deprecated paraphyletic taxa Stegocephalia and Labyrinthodontia, because of a skull that was connected to the shoulder girdle and teeth of labyrinthodont type. The skull had a distinct pineal foramen. Besides the usual row of teeth in the upper and lower jaw, Sclerocephalus also had three additional pairs of palatine teeth. From specimens with fossilized stomach content we know the adults mainly fed on fish of the genus Paramblypterus , but sometimes also on other amphibians ( Branchiosaurus , Micromelerpeton ) and even small conspecifics.
The holotype of Sclerocephalus haeuseri was described 1847 by the German paleontologist Georg August Goldfuss, who misidentified the fossil as skull of a fish. The famous American vertebrate paleontologist Alfred Romer recognized in 1939 that the fossil amphibians described as Leptorophus levis are the larvae of Sclerocephalus. The most important modern research on Sclerocephalus was published by Boy (1988) and Schoch (2000, 2002, 2003, 2009).
A famous locality that yielded numerous excellently preserved fossils of Sclerocephalus is Odernheim am Glan in Rhineland-Palatinate (Germany), where the Permian sediments of the Rotliegend have even been named "Stegocephalenkalke" (= Stegocephalia limestones).
Krätschmer (2004) questioned the validity of the type species Sclerocephalus haeuseri, of which the holotype is lost, and considered Pfarrwaldia jeckenbachensis as valid name for the neotype designated by Boy (1988). This was refuted in the revision of Schoch & Witzmann (2009), who considered P. jeckenbachensis as younger synonym of S. haeuseri.
The following four species are recognized as valid by Schoch & Witzmann (2009):
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The phylogenetic relationships of Sclerocephalus are uncertain. It was traditionally considered a close relative of the genus Onchiodon , and both were placed in the family Actinodontidae. Actinodontidae was thought to be closely related to the family Eryopidae, and is now considered a synonym of that group. However, while Sclerocephalus shares some similarities with eryopids, it also shares much in common with a group of large-bodied, semiaquatic temnospondyls called Stereospondylomorpha. Sclerocephalus and Onchiodon are no longer thought to be closely related, and while Onchiodon remains a close relative of eryopids, Sclerocephalus is often grouped near the genus Archegosaurus as a basal stereospondylomorph. [1]
The most commonly accepted phylogeny of temnospondyls (first proposed by Yates and Warren [2000]) divides the group into two different branches called Limnarchia and Euskelia. Limnarchia is a diverse Mesozoic clade that includes Stereospondylomorpha. Euskelia is a smaller Paleozoic clade that includes Eryopidae and the group Dissorophoidea, which may have given rise to modern amphibians. [2] An earlier phylogeny proposed by Boy (1990) takes a different view, combining Eryopidae and Stereospondylomorpha into the group Eryopoidea, with dissorophoids as distant relatives. [3] If this phylogeny is correct, Sclerocephalus would be a basal member of Eryopoidea, close to the ancestry of most other stereospondylomorphs.
Schoch & Witzmann (2009) found support for the Eryopoidea clade. They included Sclerocephalus in their phylogenetic analysis and found it to nest at the base of Stereospondylomorpha. Below is a cladogram from their study: [1]
Temnospondyli |
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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 armour-like bony plates that distinguish them from the modern soft-bodied lissamphibians.
Eryopoidea are a taxon of late Carboniferous and Permian temnospondyli amphibians, known from North America and Europe. Carroll includes no fewer than ten families, but Yates and Warren replace this with a cladistic approach and include three families, the Eryopidae, Parioxyidae and Zatrachydidae. They define the Eryopoidea as all Euskelia in which the choana are relatively rounded and the iliac blade vertical. A similar definition but without the Euskelia is provided by Laurin and Steyer.
Zatracheidae is a family of Late Carboniferous and Early Permian temnospondyl amphibians known from North America and Europe. Zatracheidids are distinguished by lateral (sideways) bony protuberances of the quadratojugal bone of the skull, and a large opening in the snout called the internarial fontanelle that is bordered by enlarged premaxillae. The skull is flattened, with small orbits or eye sockets set far back. The opening in the snout may have housed a gland for producing a sticky substance so that prey would adhere to the tongue. If so, this indicates that these animals spent a large part of their time on land.
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).
Micromelerpetontidae is an extinct family of dissorophoid temnospondyl amphibians that lived from the Late Carboniferous to the Early Permian in what is now Europe, with one Carboniferous species also known from North Africa. They were biologically similar to the related branchiosaurids, but proportionally akin to the unrelated microsaurs.
Cheliderpeton is an extinct genus of temnospondyl amphibian. It lived during the Early Permian in what is now Europe. Fossils have been found from the Ruprechtice horizon of the Intrasudetic Basin of Bohemia in the Czech Republic, as well as the Saar-Nahe Basin of southwestern Germany. Cheliderpeton had a 16 cm skull, and reached about 65 cm in length.
Intasuchus is an extinct genus of temnospondyl amphibian from the Middle Permian of Russia. It is known from a single species, Intasuchus silvicola, which was named in 1956. Intasuchus belongs to the family Intasuchidae and is probably its sole member, although other taxa such as Syndyodosuchus and Cheliderpeton have been assigned to the family in the past. Intasuchus most likely belongs to the group Archegosauroidea, Permian relatives of the large, mostly Mesozoic temnospondyl clade Stereospondyli.
Actinodon is an extinct genus of eryopoidean temnospondyl within the family Eryopidae.
Apateon is an extinct genus of temnospondyl amphibian within the family Branchiosauridae.
Stereospondylomorpha is a clade of temnospondyls. It includes the superfamily Archegosauroidea and the more diverse group Stereospondyli. Stereospondylomorpha was first proposed by Yates and Warren (2000), who found Archegosauroidea and Stereospondyli to be sister taxa in their phylogenetic analysis. A similar clade is Archegosauriformes, named by Schoch and Milner (2000), which includes Stereospondyli and some Permian temnospondyls that are similar in appearance to stereospondyls, including the archegosauroids. However, according to Schoch and Milner's phylogeny, Archegosauroidea is a paraphyletic group of taxa that are successively basal to Stereospondyli, rather than a monophyletic sister taxon.
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.
Rhytidosteoidea is a superfamily of Temnospondyli, early amphibian species that existed during the Carboniferous, Permian, and Triassic periods. The taxon was established in 1965 to accommodate two new species of Deltasaurus, the author recognising an alliance with previously described genera.
Acroplous is an extinct genus of dvinosaurian Temnospondyli within the family Eobrachyopidae.
Hyperokynodon is an extinct genus of trematosaurian temnospondyl within the family Trematosauridae. Fossils have been found in Germany. While most trematosaurids existed during the Early Triassic, Hyperokynodon has been found in Late Triassic deposits, making it the youngest known trematosaurid. Hyperokynodon was known since 1852, but it was not identified as a trematosaurid until 1987. The type and only species is H. keuperinus.
Rhineceps is an extinct genus of temnospondyl amphibian in the family Rhinesuchidae. Rhineceps was found in Northern Malawi in Southern Africa known only from its type species R. nyasaensis. Rhineceps was a late Permian semi-aquatic carnivore that lived in streams, rivers, lakes or lagoons. Rhineceps is an early divergent Stereopondyl within the family Rhinesuchidae, which only existed in the late Permian (Lopingian) and failed to survive the Permian-Triassic extinction unlike other stereospondyl families.
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 within the monotypic family Intasuchidae. They were fully aquatic animals, and were metabolically and physiologically more similar to fish than modern amphibians.
Acanthostomatops is an extinct genus of zatracheidid temnospondyl from the Lower Permian Döhlen Basin of Saxony.
Branchiosauridae is an extinct family of small amphibamiform temnospondyls with external gills and an overall juvenile appearance. The family has been characterized by hundreds of well-preserved specimens from the Permo-Carboniferous of Middle Europe. Specimens represent well defined ontogenetic stages and thus the taxon has been described to display paedomorphy (perennibranchiate). However, more recent work has revealed branchiosaurid taxa that display metamorphosing trajectories. The name Branchiosauridae refers to the retention of gills.
Korkonterpeton is a genus of temnospondyl from the Asselian of the Prosečné Formation. Its genus is named after the Celtic name for the Krkonoše Mountains of the Czech Republic and the Ancient Greek word ἑρπετόν (herpetón), which means reptile. Thus Korkonterpeton means "reptile of the Krkonoše Mountains". The type species, Korkonterpeton kalnense was described based on a partial skeleton with a large skull, which is visible in dorsal and palatal views. The postcranial skeleton is disarticulated but with well-preserved elements, including the vertebral column and the ribs.