''Callistomordax'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...

amphibian from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

of Germany. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only species, ''Callistomordax kugleri'', was named in 2008. It is known from several well-preserved skeletons found in the

Erfurt Formation The Erfurt Formation, also known as the Lower Keuper (German: ''Untere Keuper'', ''Lettenkeuper'', ''Lettenkohle'' or ''Lettenkohlenkeuper''), is a stratigraphic formation of the Keuper group and the Germanic Trias supergroup. It was deposited ...

, part of the Lower

Keuper The Keuper is a lithostratigraphic unit (a sequence of rock strata) in the subsurface of large parts of west and central Europe. The Keuper consists of dolomite, shales or claystones and evaporites that were deposited during the Middle and Lat ...

, which dates back to the late

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

stage.

History of study and provenance

The first specimen of ''Callistomordax kugleri,'' which is currently reposited at the Staatliches Museum für Naturkunde (SMNS) in Stuttgart, Germany, was collected from the Middle Triassic (Upper Ladinian-aged) Erfurt Formation of Baden-Württemberg by Werner Kugler, for whom the species is named. Various authors speculated on the taxonomic affinities of the specimen, but it was not formally resolved until 2008. The specimen was subsequently donated to the SMNS and additional excavation at the original locality in 2000 led to the discovery of two nearly complete skeletons by private collectors Hans Michael Salomon and Traugott Haubold.

Anatomy

''Callistomordax'' was distinguished from other temnospondyls by characters such as a single co-ossified frontal (normally paired in tetrapods), a pterygoid with both a broad and flat quadrate ramus and a slender and narrow palatine ramus, and lateral compression of the palatal and symphyseal fangs. It shares a number of metoposaurid synapomorphies such as deeply sloping postparietals and tabulars but also retains more primitive features found in earlier diverging temnospondyls and a number of probable homoplasies.

Ecology

As with many Triassic temnospondyls, ''Callistomordax'' is considered to have been an aquatic freshwater tetrapod, evidenced by both its anatomy (e.g., lateral line system) and its depositional environment. The Lower Keuper Basin where ''Callistomordax'' was found was subjected to repeated transgression-regression cycles, resulting in mixed deposits of freshwater and marine taxa. ''Callistomordax'' is relatively rare and consists only of isolated elements in bonebeds with higher abundances of marine taxa, and the most complete specimens are found with various invertebrates and fish that suggest a relatively low salinity environment.

Phylogeny

Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

from Schoch (2008): ''Callistomordax'' is significant in filling a gap in the fossil record that inhibited firm conclusions regarding the origins of the

Metoposauridae Metoposauridae is an extinct family of trematosaurian temnospondyls. The family is known from the Triassic period. Most members are large, approximately long and could reach 3 m long.Brusatte, S. L., Butler R. J., Mateus O., & Steyer S. J. (20 ...

, which had previously been variably suggested to be placed in the Permian

Dvinosauria Dvinosaurs are one of several new clades of temnospondyls named in the phylogenetic review of the group by Yates and Warren 2000. They represent a group of primitive semi-aquatic to completely aquatic temnospondyls, and are known from the Late C ...

or within the Triassic

Trematosauria Trematosauria is one of two major groups of temnospondyl amphibians that survived the Permian-Triassic extinction event, the other (according to Yates and Warren 2000) being the Capitosauria. The trematosaurs were a diverse and important group t ...

. As seen in the above phylogeny, ''Callistomordax'' is the sister taxon to the Metoposauridae and places the

Metoposauroidea Metoposauroidea is an extinct superfamily of temnospondyls that lived from the Middle to Upper Triassic in North America, Europe and North Africa North Africa (sometimes Northern Africa) is a region encompassing the northern portion of t ...

(Metoposauridae + ''Callistomordax'') within Trematosauria.

References

{{Taxonbar, from=Q5022812 Triassic temnospondyls of Europe