Sclerocephalus
Encyclopedia
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 tetrapod
s.
, 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).
, 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.
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):
) 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.
Temnospondyli
Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
from the lowermost 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...
of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
with four valid species, including the type species S. haeuseri. It is one of the most completely preserved and most abundant Palaeozoic tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
s.
Discovery
The holotype of Sclerocephalus haeuseri was described 1847 by the German paleontologist Georg August GoldfussGeorg August Goldfuss
Georg August Goldfuss was a German palaeontologist and zoologist.-Biography:Goldfuss was born at Thurnau near Bayreuth. He was educated at Erlangen, where he graduated Ph.D. in 1804 and became professor of zoology in 1818. He was subsequently appointed professor of zoology and mineralogy at the...
, who misidentified the fossil as skull of a fish. The famous American vertebrate paleontologist Alfred Romer
Alfred Romer
Alfred Sherwood Romer was an American paleontologist and comparative anatomist and a specialist in vertebrate evolution.-Biography:...
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
Odernheim am Glan
Odernheim am Glan is a municipality in the district of Bad Kreuznach in Rhineland-Palatinate, in western Germany. It is a village of 1,900 people. The physical setting of Odernheim is quite picturesque. It is situated on the river Glan amid rolling hills and vineyards. Nearby towns include...
in Rhineland-Palatinate
Rhineland-Palatinate
Rhineland-Palatinate is one of the 16 states of the Federal Republic of Germany. It has an area of and about four million inhabitants. The capital is Mainz. English speakers also commonly refer to the state by its German name, Rheinland-Pfalz ....
(Germany), where the Permian sediments of the Rotliegend
Rotliegend
The Rotliegend or Rotliegendes is a lithostratigraphic unit of Cisuralian age that is found in the subsurface of large areas in western and central Europe. The Rotliegend mainly consists of sandstone layers...
have even been named "Stegocephalenkalke" (= Stegocephalia limestones).
Description and Biology
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 ontogenyOntogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
, 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
Stegocephalia
Stegocephalia is an old term for early amphibians, comprising all pre-Jurassic and some later extinct large amphibians of more or less salamander-like build...
and Labyrinthodontia
Labyrinthodontia
Labyrinthodontia is an older term for any member of the extinct subclass of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times . The group is ancestral to all extant landliving vertebrates, and as such constitutes an evolutionary grade rather...
, because of a skull that was connected to the shoulder girdle and teeth of labyrinthodont type. The skull had a distinct pineal foramen
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...
. 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
Paramblypterus
Paramblypterus is an extinct genus of prehistoric bony fish.-See also:* Prehistoric fish* List of prehistoric bony fish...
, but sometimes also on other amphibians (Branchiosaurus
Branchiosaurus
Branchiosaurus is a genus of small, lightly built early prehistoric amphibians. Fossils have been discovered in strata dating from the late Pennsylvanian Epoch to the Permian Period...
, Micromelerpeton
Micromelerpeton
Micromelerpeton is an extinct genus of dissorophoidean euskelian temnospondyl within the family Micromelerpetontidae.-References:* Gaining Ground: The Origin and Early Evolution of Tetrapods...
) and even small conspecifics.
Taxonomy
Krätschmer (2004) questioned the validity of the type species Sclerocephalus haeuseri, of which the holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as 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
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of S. haeuseri.
The following four species are recognized as valid by Schoch & Witzmann (2009):
- Sclerocephalus haeuseri Goldfuss, 1847 from the AsselianAsselianIn the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...
(Lower RotliegendRotliegendThe Rotliegend or Rotliegendes is a lithostratigraphic unit of Cisuralian age that is found in the subsurface of large areas in western and central Europe. The Rotliegend mainly consists of sandstone layers...
) of Rhineland-PalatinateRhineland-PalatinateRhineland-Palatinate is one of the 16 states of the Federal Republic of Germany. It has an area of and about four million inhabitants. The capital is Mainz. English speakers also commonly refer to the state by its German name, Rheinland-Pfalz ....
in Germany. - Sclerocephalus bavaricus (Branco, 1887) from the AsselianAsselianIn the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...
(Lower Rotliegend) or uppermost PennsylvanianPennsylvanianThe Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
(GzhelianGzhelianThe Gzhelian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from 303.9 ± 0.9 to 299.0 ± 0.8 Ma...
) of Rhineland-Palatinate in Germany. - Sclerocephalus jogischneideri Werneburg, 1992 from the AsselianAsselianIn the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...
(Lower Rotliegend) of ThuringiaThuringiaThe Free State of Thuringia is a state of Germany, located in the central part of the country.It has an area of and 2.29 million inhabitants, making it the sixth smallest by area and the fifth smallest by population of Germany's sixteen states....
in Germany - Sclerocephalus nobilis (Krätschmer & Resch, 2005) from the AsselianAsselianIn the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...
(Lower Rotliegend) of Rhineland-Palatinate in Germany.
Phylogeny
Sclerocephalus is a stem group representative of modern amphibians (clade LissamphibiaLissamphibia
The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,...
) and shares with all Batrachomorpha the presence of only four fingers as derived character state (synapomorphy
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
). According to the revision and cladistic study by Schoch & Witzmann (2009) Sclerocephalus nests at the base of Stereospondylomorpha
Stereospondylomorpha
Stereospondylomorpha is a clade of temnospondyl amphibians. It includes the superfamily Archegosauroidea and the more diverse group Stereospondyli....
, but the monophyly of the genus Sclerocephalus is only weakly supported. Schoch & Witzmann (2009) found more support for the Eryopoidea
Eryopoidea
Eryopoidea are a taxon of late Carboniferous and Permian temnospondyli amphibians, known from North America and Europe. Carroll includes no less than ten families, but Yates and Warren replace this with a cladistic approach and include only two Permian families, the Eryopidae and Zatrachydidae...
hypothesis (Eryopidae
Eryopidae
Eryopidae are a family of medium to large Permian temnospondyli amphibians, known from North America and Europe. They are defined cladistically as all Eryopoidea with interpterygoid vacuities that are rounded at the front; and large external nares...
+ Stereospondylomorpha
Stereospondylomorpha
Stereospondylomorpha is a clade of temnospondyl amphibians. It includes the superfamily Archegosauroidea and the more diverse group Stereospondyli....
) than for the Euskelia
Euskelia
Euskelia is a clade of extinct Temnospondyl amphibians.-References:*Yates, A. M. & Warren, A. A. , The phylogeny of the 'higher' temnospondyls and its implications for the monophyly and origins of the Stereospondyli. Zoological Journal of the Linnean Society 128: 77-121....
hypothesis (Eryopidae + Zatracheidae + Dissorophoidea
Dissorophoidea
Dissorophoideans are a clade of medium-sized, temnospondyl amphibians that appeared during the Late Pennsylvanian in Euramerica, and continued through to the Late Permian and even possibly the Early Triassic of Gondwana...
). 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
Onchiodon
Onchiodon is an extinct genus of temnospondyl amphibian....
(= 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.