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''Diplovertebron'' (from , 'double' and , 'vertebra') is an
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
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 ...
of embolomere that lived in the Late
Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...
period ( Moscovian), about 310 million years ago. ''Diplovertebron'' was a medium-sized animal, around 50 cm in length. Members of the genus inhabited European Carboniferous swamps in what is now the
Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...
. They were closely related to larger swamp-dwelling tetrapods like ''
Proterogyrinus ''Proterogyrinus'' is an extinct genus of early tetrapods from the order Embolomeri. Fossil remains of ''Proterogyrinus'' have been found in Scotland, UK, and West Virginia, United States, and date back to the Serpukhovian (mid-Carboniferous p ...
'' and '' Anthracosaurus''. However, ''Diplovertebron'' were much smaller than these large, crocodile-like creatures. Known from a single species, ''Diplovertebron punctatum,'' this genus has had a complicated history closely tied to '' Gephyrostegus'', another genus of small, reptile-like amphibians.


History

''Diplovertebron'' was one of many tetrapods found in Czech coal swamps by Antonin Frič in the late 19th century. Its remains were an assortment of disarticulated fossils encased in two slabs of coal, which were designated Fr. Orig. 96 (for the smaller slab) and Fr. Orig. 128 (for the larger slab). D.M.S. Watson (1926) assigned two more complete specimens to the genus. One of these had already been named as 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. * ...
specimen of the reptile-like tetrapod ''Gephyrostegus'' by
Otto Jaekel Otto Max Johannes Jaekel (21 February 1863 – 6 March 1929) was a German paleontologist and geologist. Biography Jaekel was born in Nowa Sól, Neusalz (Nowa Sól), Prussian Silesia, the son of a builder and the youngest of seven children. He st ...
in 1902, while the second specimen, DMSW B.65, was newly described. A later study, Brough & Brough (1967), restored the validity of ''Gephyrostegus'' and rebuked Watson's decision to add Jaekel's and his specimens to ''Diplovertebron''.
Richard Lydekker Richard Lydekker (; 25 July 1849 – 16 April 1915) was a British naturalist, geologist and writer of numerous books on natural history. He was known for his contributions to zoology, paleontology, and biogeography. He worked extensively in cata ...
renamed ''Diplovertebron'' to ''Diplospondylus'' in 1889, based on the fact that the etymology of "''Diplospondylus''" was all
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
, while that of "''Diplovertebron''" was a hybrid of Greek and
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
. However, few other paleontologists shared Lydekker's aversion to hybrid names. Another aspect of ''Diplovertebron'''s history which led to some confusion relates to the labeling in Frič's original
lithographic Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German ...
illustrations. Plate 53, the illustration which featured remains from the larger slab of ''Diplovertebron'' fossils (Fr. Orig. 128), was accidentally labeled as pertaining to fossils from the smaller slab (Fr. Orig 96). As a result, many paleontologists misunderstood the original description and ignored the larger slab when describing ''Diplovertebron'', as they assumed that there was only a single slab (Fr. Orig. 96) available. There were only a few exceptions to this mistake, namely Steen (1938) and Klembara ''et al.'' (2014). Several Czech fossils described by Frič as other genera may actually represent additional ''Diplovertebron'' material. ''Hemichthys problematica'', a supposed fish skull described in 1895, was later found to be an anthracosaur skull. Klembara ''et al.'' (2014: 776) argued that the ''Hemichthys'' skull fossil was actually referable to ''Gephyrostegus'', and that, although the name ''Hemichthys'' was published earlier, it had not been considered a valid taxon since its original description, so it should be treated as a
nomen oblitum In zoological nomenclature, a ''nomen oblitum'' (plural: ''nomina oblita''; Latin for "forgotten name") is a disused scientific name which has been declared to be obsolete (figuratively "forgotten") in favor of another "protected" name. In its pr ...
according to ''ICZN'' Art. 23.9.1.''ICZN'' Art. 23.9.1
/ref> They treated ''Diplovertebron'' as a valid genus, different from ''Gephyrostegus''. Likewise, an embolomerous tail with dense scalation along its underside was named ''Nummulosaurus kolbii'' in 1901. Romer (1947) could find no evidence that ''Nummulosaurus'' was not identical to ''Diplovertebron''. Romer was also one of the few paleontologists to consider ''Diplovertebron'' to be a
seymouriamorph Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest that seymouria ...
, rather than an embolomere. However, this classification scheme was based on ''Gephyrostegus'' fossils, as the two genera were still considered synonymous in 1947.


Description

Historical recounts of ''Diplovertebron'' between 1926 and 1967 typically reconstructed it as a reptile-like terrestrial animal with five-fingered hands and feet. However, these reconstructions were created using more complete skeletal remains of '' Gephyrostegus'' and '' Solenodonsaurus'', which at the time were considered to be synonymous with ''Diplovertebron''. Without these skeletons, the fossil remains of ''Diplovertebron'' are much more limited. Nowadays it is assumed that ''Diplovertebron'' was partially or fully aquatic, akin to other embolomeres like '' Archeria'' and ''
Proterogyrinus ''Proterogyrinus'' is an extinct genus of early tetrapods from the order Embolomeri. Fossil remains of ''Proterogyrinus'' have been found in Scotland, UK, and West Virginia, United States, and date back to the Serpukhovian (mid-Carboniferous p ...
''. Nevertheless, it was probably still similar to ''Gephyrostegus'' in terms of general proportions. Like other embolomeres, each of ''Diplovertebron'''s vertebrae were composed of two ring-shaped components of equal size. Frič originally regarded this as a unique feature, but as early as 1884, E.D. Cope drew connections between the vertebrae of ''Diplovertebron'' and "''Cricotus''" (an American embolomere more commonly known as ''Archeria''). The preserved vertebrae were from the tail region, since the front segment (intercentrum) connected to thin
haemal arch A haemal arch, also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the ha ...
es. The fragmentary skull bones are only slightly ornamented with striations, rather than the numerous pits that were present in its relatives. The
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...
contained five thick and conical teeth, about twice as long as they were wide. The
maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...
likely had over 30 teeth in it, and its teeth were thinner than those of the premaxilla. The teeth towards the front of the maxilla were thicker and more widely separated, while those at the back were closely packed. The teeth of the lower jaw were more numerous, closely packed, and much smaller than those of the upper jaw. There were over 40 in total, and the first 7 were the largest and most well-spaced. All of the teeth possessed maze-like enamel folding similar to other "
labyrinthodonts "Labyrinthodontia" (Greek language, Greek, 'maze-toothed') is an informal grouping of Extinction, extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ...
". These dental features showed some similarities to the teeth of '' Calligenethlon'', an embolomere which was similar in size to ''Diplovertebron''. The belly was covered with long, oblong scales with rounded edges, while the back was bare. Various limb bones were preserved. Unusually, they were covered with tiny pores. The
humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...
had a strong diagonal ridge along half of its shaft, similar to that of ''Archeria''. The pelvis was also quite similar to that of ''Archeria'' and ''Calligenethlon'' in the fact that the ilium had a structure typical for embolomeres: two rod-like prongs atop a short "stem". The front prong was short, but the rear prong was very long Frič (1885) referred an
interclavicle An interclavicle is a bone which, in most tetrapods, is located between the clavicles. Therian mammals ( marsupials and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. In ...
to ''Diplovertebron'', though it may have actually been from ''Gephyrostegus'' instead.


References

Benes, Josef. Prehistoric Animals and Plants. Pg. 80. Prague: Artia, 1979. {{Taxonbar, from=Q425674 Embolomeri Carboniferous amphibians of Europe Fossils of the Czech Republic Taxa named by Antonin Fritsch