Embolomeri
   HOME

TheInfoList



OR:

Embolomeri is an
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
of
tetrapods A tetrapod (; from Ancient Greek τετρα- ''(tetra-)'' 'four' and πούς ''(poús)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the lat ...
or
stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...
-tetrapods, possibly members of
Reptiliomorpha Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...
. Embolomeres first
evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
in the Early
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 ...
( Mississippian) Period and were the largest and most successful predatory tetrapods of the Late Carboniferous ( Pennsylvanian) Period. They were specialized semiaquatic predators with long bodies for eel-like undulatory swimming. Embolomeres are characterized by their vertebral centra, which are formed by two cylindrical segments, the pleurocentrum at the rear and intercentrum at the front. These segments are equal in size. Most other tetrapods have pleurocentra and intercentra which are drastically different in size and shape. Embolomeres were among the earliest large carnivorous tetrapods, with members such as the crocodilian-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 ...
'' appearing in the Visean stage of the Carboniferous. They declined in diversity during the Permian period, though at least one representative ('' Archeria)'' was common in the
Early Permian 01 or 01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), ''01'' (Richard Müller album), 2001 * 01 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...
. Embolomeres went extinct shortly before the end of the Permian.


Classification

The order Embolomeri was first named by
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...
in 1884 during his revision of " batrachian" (
amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
) evolution. Embolomeri was differentiated from several other newly named amphibian orders, such as " Rachitomi", by the presence of intercentra and pleurocentra of the same size and shape, that being large cylinders. At the time, embolomere fossils were uncommon, so Cope could only identify "cricotids" such as '' Cricotus'' as possessing embolomerous vertebrae. The genus name "''Cricotus''" is dubious, as it has been used by Cope to refer to embolomere fossils spanning anywhere between mid- Pennsylvanian deposits of Illinois and the Permian
red beds Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain t ...
of
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. Most paleontologists now refer the red bed "''Cricotus''" specimens to the genus ''Archeria''.
Michel Laurin Michel Laurin is a Canadian-born French vertebrate paleontologist whose specialities include the emergence of a land-based lifestyle among vertebrates, the evolution of body size and the origin and phylogeny of lissamphibians. He has also made impo ...
(1998) formally defined Embolomeri as "the
last common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...
of ''Proterogyrinus'' and ''Archeria'' and all of its descendants." This definition excludes '' Eoherpeton'', which is almost always considered a close ally of the group. Some authors place '' Silvanerpeton'' or chroniosuchians as close relatives as well, though they are generally agreed to lie outside Embolomeri proper. The poorly-defined group Anthracosauria is sometimes considered synonymous with Embolomeri, and the group's namesake, '' Anthracosaurus'', is an embolomere. However, other authors use the term "Anthracosauria" in reference to a broader group which includes embolomeres in combination with various other reptile-like amphibians (
reptiliomorphs Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...
). Reptiliomorphs are all tetrapods more closely related to living reptiles and synapsids (mammals and their ancestors), rather than living amphibians. Despite this, reptiliomorphs likely had amphibian-like biological traits, such as water-based reproduction. Many studies conducted since the 1990s have also placed the group
Lepospondyli Lepospondyli is a diverse clade of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minimus''), lepospondyls lived from the Visean stage of the Early Carboniferous to the Ea ...
as closer to amniotes than embolomeres were. Lepospondyls are a particularly unusual group of tetrapods, with some members (i.e. brachystelechids) very similar to lissamphibians and others (i.e. tuditanids) very similar to amniotes. If lepospondyls are both close relatives of amniotes and the ancestors of modern amphibians, then that means that crown-Tetrapoda (descendants of the common ancestor to all living tetrapods) is a much more restricted group than previously assumed. In this situation, various traditional orders of Tetrapoda such as Embolomeri and Temnospondyli actually would qualify as stem-tetrapods due to having evolved prior to the split between modern amphibians and amniotes. However, most authors consider temnospondyls to be the ancestors of modern amphibians. This would suggest that embolomeres are likely reptiliomorphs (closer to reptiles) and within the clade Tetrapoda. However, even this classification is not stable, as some analyses have found embolomeres to be more basal than temnospondyls. 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 Ruta ''et al.'' (2003):


Genera


References

{{Taxonbar, from=Q136529 Mississippian first appearances Permian extinctions Taxa named by Edward Drinker Cope Tetrapodomorph orders