Post by Deinobrontornis on Jan 3, 2012 18:02:44 GMT -5
[a href="Sclerocephalus"]Sclerocephalus[/a]
Sclerocephalus is an extinct genus of temnospondyl amphibian from the lowermost Permian of Germany with four valid species, including the type species S. haeuseri. It is one of the most completely preserved and most abundant Palaeozoic tetrapods.
Discovery:
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).
Description and Biology:
The adults animals reached a body length of ca. 150 cm (4.9 ft), 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 aditional 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.
Taxonomy:
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):
Sclerocephalus haeuseri Goldfuss, 1847 from the Asselian (Lower Rotliegend) of Rhineland-Palatinate in Germany.
Sclerocephalus bavaricus (Branco, 1887) from the Asselian (Lower Rotliegend) or uppermost Pennsylvanian (Gzhelian) of Rhineland-Palatinate in Germany.
Sclerocephalus jogischneideri Werneburg, 1992 from the Asselian (Lower Rotliegend) of Thuringia in Germany
Sclerocephalus nobilis (Krätschmer & Resch, 2005) from the Asselian (Lower Rotliegend) of Rhineland-Palatinate in Germany.
Phylogeny:
Sclerocephalus is a stem group representative of modern amphibians (clade Lissamphibia) and shares with all Batrachomorpha the presence of only four fingers as derived character state (synapomorphy). According to the revision and cladistic study by Schoch & Witzmann (2009) Sclerocephalus nests at the base of Stereospondylomorpha, but the monophyly of the genus Sclerocephalus is only weakly supported. Schoch & Witzmann (2009) found more support for the Eryopoidea hypothesis (Eryopidae + Stereospondylomorpha) than for the Euskelia hypothesis (Eryopidae + Zatracheidae + Dissorophoidea). This indicates that the large temnospondyls of the Permian and Mesozoic formed a natural group, and that the terrestrial adaptations of Eryops and the dissorophoids evolved by convergence to Amniota. Schoch & Witzmann (2009) also confirmed the result of Werneburg & Steyer (1999) that Onchiodon (= Actinodon) frossardi does not belong to the genus Sclerocephalus but nests at the base of Eryopidae (= Actinodontidae), contra Schoch & Millner (2002) who had attributed O. frossardi to Sclerocephalus.
Sclerocephalus is an extinct genus of temnospondyl amphibian from the lowermost Permian of Germany with four valid species, including the type species S. haeuseri. It is one of the most completely preserved and most abundant Palaeozoic tetrapods.
Discovery:
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).
Description and Biology:
The adults animals reached a body length of ca. 150 cm (4.9 ft), 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 aditional 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.
Taxonomy:
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):
Sclerocephalus haeuseri Goldfuss, 1847 from the Asselian (Lower Rotliegend) of Rhineland-Palatinate in Germany.
Sclerocephalus bavaricus (Branco, 1887) from the Asselian (Lower Rotliegend) or uppermost Pennsylvanian (Gzhelian) of Rhineland-Palatinate in Germany.
Sclerocephalus jogischneideri Werneburg, 1992 from the Asselian (Lower Rotliegend) of Thuringia in Germany
Sclerocephalus nobilis (Krätschmer & Resch, 2005) from the Asselian (Lower Rotliegend) of Rhineland-Palatinate in Germany.
Phylogeny:
Sclerocephalus is a stem group representative of modern amphibians (clade Lissamphibia) and shares with all Batrachomorpha the presence of only four fingers as derived character state (synapomorphy). According to the revision and cladistic study by Schoch & Witzmann (2009) Sclerocephalus nests at the base of Stereospondylomorpha, but the monophyly of the genus Sclerocephalus is only weakly supported. Schoch & Witzmann (2009) found more support for the Eryopoidea hypothesis (Eryopidae + Stereospondylomorpha) than for the Euskelia hypothesis (Eryopidae + Zatracheidae + Dissorophoidea). This indicates that the large temnospondyls of the Permian and Mesozoic formed a natural group, and that the terrestrial adaptations of Eryops and the dissorophoids evolved by convergence to Amniota. Schoch & Witzmann (2009) also confirmed the result of Werneburg & Steyer (1999) that Onchiodon (= Actinodon) frossardi does not belong to the genus Sclerocephalus but nests at the base of Eryopidae (= Actinodontidae), contra Schoch & Millner (2002) who had attributed O. frossardi to Sclerocephalus.
