Reptiliomorpha (meaning reptile-shaped; in
PhyloCode
The ''International Code of Phylogenetic Nomenclature'', known as the ''PhyloCode'' for short, is a formal set of rules governing phylogenetic nomenclature. Its current version is specifically designed to regulate the naming of clades, leaving th ...
known as ''Pan-Amniota''
) is a
clade containing the
amniotes
Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are dis ...
and those
tetrapod
Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...
s that share a more recent common ancestor with amniotes than with living
amphibians (
lissamphibia
The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relative ...
ns). It was defined by
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 ...
(2001) and Vallin and Laurin (2004) as the largest clade that includes ''
Homo sapiens
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'', but not ''
Ascaphus truei'' (tailed frog).
Laurin and Reisz (2020) defined Pan-Amniota as the largest
total clade containing ''
Homo sapiens
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'', but not ''
Pipa pipa'', ''
Caecilia tentaculata'', and ''
Siren lacertina
The greater siren (''Siren lacertina'') is an eel-like amphibian and one of the three members of the genus ''Siren''. The largest of the sirens and one of the largest amphibians in North America, the greater siren resides in the coastal plains of ...
''.
The informal variant of the name, "reptiliomorphs", is also occasionally used to refer to
stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushr ...
-amniotes, i.e. a
grade of
reptile-like tetrapods that are more closely related to amniotes than they are to lissamphibians, but are not amniotes themselves; the name is used in this meaning e.g. by Ruta, Coates and Quicke (2003).
An alternative name, "
Anthracosauria", is also commonly used for the group, but is confusingly also used for a more primitive grade of reptiliomorphs (
Embolomeri) by
Benton Benton may refer to:
Places
Canada
*Benton, a local service district south of Woodstock, New Brunswick
*Benton, Newfoundland and Labrador
United Kingdom
* Benton, Devon, near Bratton Fleming
* Benton, Tyne and Wear
United States
*Benton, Alabam ...
.
[Benton, M. J. (2000), ''Vertebrate Paleontology'', 2nd Ed. Blackwell Science Ltd 3rd ed. 2004 – see als]
taxonomic hierarchy of the vertebrates
according to Benton 2004
As the exact phylogenetic position of Lissamphibia within Tetrapoda remains uncertain, it also remains controversial which fossil tetrapods are more closely related to amniotes than to lissamphibians, and thus, which ones of them were reptiliomorphs in any meaning of the word. The two major hypotheses for lissamphibian origins are that they are either descendants of
dissorophoid temnospondyls or
microsaurian "
lepospondyls
Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minumus''), lepospondyls lived from the Early Carboniferous (Mississippian) to the Early ...
". If the former (the "temnospondyl hypothesis") is true, then Reptiliomorpha includes all tetrapod groups that are closer to amniotes than to temnospondyls. These include the
diadectomorphs,
seymouriamorphs, most or all "lepospondyls",
gephyrostegids, and possibly the
embolomeres
Embolomeri is an order of tetrapods or stem-tetrapods, possibly members of Reptiliomorpha. Embolomeres first evolved in the Early Carboniferous ( Mississippian) Period and were the largest and most successful predatory tetrapods of the Late Carb ...
and
chroniosuchians.
In addition, several "anthracosaur"
genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...
of uncertain taxonomic placement would also probably qualify as reptiliomorphs, including ''
Solenodonsaurus'', ''
Eldeceeon
''Eldeceeon'' is an extinct genus of reptiliomorph from the Mississippian (early Carboniferous) of Scotland. It is known from two fossil specimens found within the Viséan-age East Kirkton Quarry in West Lothian. The type and only species, '' ...
'', ''
Silvanerpeton'', and ''
Casineria''. However, if lissamphibians originated among the lepospondyls according to the "lepospondyl hypothesis", then Reptiliomorpha refers to groups that are closer to amniotes than to lepospondyls. Few non-amniote groups would count as reptiliomorphs under this definition, although the diadectomorphs are among those that qualify.
Changing definitions
The name Reptiliomorpha was coined by Professor
Gunnar Säve-Söderbergh in 1934 to designate amniotes and various types of late Paleozoic tetrapods that were more closely related to amniotes than to living amphibians. In his view, the amphibians had evolved from fish twice, with one group composed of the ancestors of modern
salamanders and the other, which Säve-Söderbergh referred to as Eutetrapoda, consisting of anurans (
frog
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...
s), amniotes, and their ancestors, with the origin of
caecilian
Caecilians (; ) are a group of limbless, vermiform or serpentine amphibians. They mostly live hidden in the ground and in stream substrates, making them the least familiar order of amphibians. Caecilians are mostly distributed in the tropics ...
s being uncertain. Säve-Söderbergh's Eutetrapoda consisted of two sister-groups: Batrachomorpha, containing anurans and their ancestors, and Reptiliomorpha, containing anthracosaurs and amniotes. Säve-Söderbergh subsequently added Seymouriamorpha to his Reptiliomorpha as well.
Alfred Sherwood Romer
Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution.
Biography
Alfred Romer was born in White Plains, New York, the son of Harry Houston Romer an ...
rejected Säve-Söderbergh's theory of a
biphyletic amphibia and used the name
Anthracosauria to describe the "labyrinthodont" lineage from which amniotes evolved. In 1970, the German paleontologist Alec Panchen took up Säve-Söderbergh's name for this group as having priority, but Romer's terminology is still in use, e.g. by Carroll (1988 and 2002) and by Hildebrand & Goslow (2001).
Some writers preferring
phylogenetic nomenclature use Anthracosauria.
In 1956,
Friedrich von Huene included both amphibians and
anapsid reptiles in the Reptiliomorpha. This included the following
orders
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
:
Anthracosauria,
Seymouriamorpha
Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered reptiliomorphs, and most paleontologists may still accept this point of view, but some analyses suggest that seymouriamorphs are ...
,
Microsauria,
Diadectomorpha,
Procolophonia
The Procolophonia are a suborder of herbivorous reptiles that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the Cotylosauria (later renamed Captorhinida Carroll 1988) but ar ...
,
Pareiasauria,
Captorhinidia,
Testudinata
Testudinata is the group of all tetrapods with a true turtle shell. It includes both modern turtles (Testudines) and many of their extinct, shelled relatives (stem-turtles). Though it was first coined as the group containing turtles by Jacob T ...
.
Michael Benton (2000, 2004) made it the sister-clade to
Lepospondyli, containing "anthracosaurs" (in the strict sense, i.e.
Embolomeri), seymouriamorphs, diadectomorphs and amniotes.
Subsequently, Benton included lepospondyls in Reptiliomorpha as well. However, when considered in a
Linnean framework, Reptiliomorpha is given the rank of
superorder and includes only reptile-like amphibians, not their amniote descendants.
Several phylogenetic studies indicate that amniotes and diadectomorphs share a more recent common ancestor with
lepospondyls
Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minumus''), lepospondyls lived from the Early Carboniferous (Mississippian) to the Early ...
than with seymouriamorphs, ''Gephyrostegus'' and Embolomeri (e.g. Laurin and Reisz, 1997,
1999;
Ruta, Coates and Quicke, 2003;
Vallin and Laurin, 2004;
Ruta and Coates, 2007
). Lepospondyls are one of the groups of tetrapods suggested to be ancestors of living amphibians; as such, their potential close relationship to amniotes has important implications for the content of Reptiliomorpha. Assuming that lissamphibians aren't descended from lepospondyls but from a different group of tetrapods, e.g. from
temnospondyls,
it would mean that Lepospondyli belonged to Reptiliomorpha ''sensu'' Laurin (2001), as it would make them more closely related to amniotes than to lissamphibians. On the other hand, if lissamphibians are descended from lepospondyls,
then not only Lepospondyli would have to be excluded from Reptiliomorpha, but seymouriamorphs, ''Gephyrostegus'' and Embolomeri would also have to be excluded from this group, as this would make them more distantly related to amniotes than living amphibians are. In that case, the clade Reptiliomorpha ''sensu'' Laurin would contain, apart from Amniota, only diadectomorphs and possibly also ''
Solenodonsaurus''.
Characteristics
Gephyrostegids, seymouriamorphs and diadectomorphs were land-based, reptile-like amphibians, while embolomeres were aquatic amphibians with long body and short limbs. Their anatomy falls between the mainly aquatic
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...
labyrinthodonts and the
first reptiles.
University of Bristol
The University of Bristol is a Red brick university, red brick Russell Group research university in Bristol, England. It received its royal charter in 1909, although it can trace its roots to a Society of Merchant Venturers, Merchant Venturers' sc ...
paleontologist Professor
Michael J. Benton gives the following characteristics for the Reptiliomorpha (in which he includes embolomeres, seymouriamorphs and diadectomorphs):
* narrow
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 mammal has ...
e (less than half the skull width)
*
vomers taper forward
*
phalangeal formulae (number of joints in each toe) of foot 2.3.4.5.4–5
Cranial morphology
The groups traditionally assigned to Reptiliomorpha, i.e. embolomeres, seymouriamorphs and diadectomorphs, differed from their contemporaries, the non-reptiliomorph temnospondyls, in having a deeper and taller skull, but retained the primitive kinesis (loose attachment) between the
skull roof
The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
In comparati ...
and the cheek (with exception of some specialized taxa, such as ''
Seymouria'', in which the cheek was solidly attached to the skull roof). The deeper skull allowed for laterally placed eyes, contrary to the dorsally placed eyes commonly found in amphibians. The skulls of the group are usually found with fine radiating grooves. The
quadrate bone
The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids.
In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms uppe ...
in the back of the skull held a deep
otic notch
Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Otic notches are one of the features lost in the evolution of amniotes from their tetrapod ancestors.
The notches have been interpreted as part of an ...
, likely holding a
spiracle rather than a
tympanum.
[Palaeo]
Reptilomorpha
Postcranial skeleton
The
vertebrae
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...
showed the typical multi-element construction seen in labyrinthodonts. According to Benton, in the vertebrae of "anthracosaurs" (i.e.
Embolomeri) the
intercentrum and
pleurocentrum may be of equal size, while in the vertebrae of
seymouriamorphs the pleurocentrum is the dominant element and the intercentrum is reduced to a small wedge. The intercentrum gets further reduced in the vertebrae of amniotes, where it becomes a thin plate or disappears altogether. Unlike most labyrinthodonts, the body was moderately deep rather than flat, and the limbs were well-developed and ossified, indicating a predominantly terrestrial lifestyle except in secondarily aquatic groups. Each foot held 5 digits, the pattern seen in their
amniote descendants.
[ Romer, A.S. & T.S. Parsons. 1977. ''The Vertebrate Body.'' 5th ed. Saunders, Philadelphia. (6th ed. 1985)] They did, however, lack the reptilian type of ankle bone that would have allowed the use of the feet as levers for propulsion rather than as holdfasts.
Physiology
The general build was heavy in all forms, though otherwise very similar to that of early reptiles. The skin, at least in the more advanced forms probably had a water-tight epidermal horny overlay, similar to the one seen in today's reptiles, though they lacked horny claws.
In
chroniosuchians and some
seymouriamorphs, like ''
Discosauriscus'', dermal scales are found in post-metamorphic specimens, indicating they may have had a "knobbly", if not scaly, appearance. With reptiliomorph anthracosaurs having evolved small near-circular keratinous scales, their amniote descendants further covered almost their entire body with them, and also formed
claws of keratin, with both scales and claws making
cutaneous respiration and water absorption impossible, making them breathe through their mouths and nostrils, and drink water through mouth.
Seymouriamorphs reproduced in amphibian fashion with aquatic
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s that hatched into
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
Th ...
e (tadpoles) with external gills; it is unknown how other tetrapods traditionally assigned to Reptiliomorpha reproduced.
Evolutionary history
Early reptiliomorphs
During the
Carboniferous and
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...
periods, some
tetrapod
Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...
s started to evolve towards a
reptilian condition. Some of these tetrapods (e.g. ''
Archeria'', ''
Eogyrinus'') were elongate, eel-like aquatic forms with diminutive limbs, while others (e.g. ''
Seymouria'', ''
Solenodonsaurus'', ''
Diadectes
''Diadectes'' (meaning ''crosswise-biter'') is an extinct genus of large reptiliomorphs or synapsids that lived during the early Permian period ( Artinskian- Kungurian stages of the Cisuralian epoch, between 290 and 272 million years ago). '' ...
'', ''
Limnoscelis'') were so reptile-like that until quite recently they actually had been considered to be true reptiles, and it is likely that to a modern observer they would have appeared as large to medium-sized, heavy-set
lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia al ...
s. Several groups however remained aquatic or semiaquatic. Some of the
chroniosuchians show the build and presumably habits of modern crocodiles and were probably also similar to crocodylians in that they were river-side predators. While some other
Chroniosuchians possessed elongated
newt
A newt is a salamander in the subfamily Pleurodelinae. The terrestrial juvenile phase is called an eft. Unlike other members of the family Salamandridae, newts are semiaquatic, alternating between aquatic and terrestrial habitats. Not all aqua ...
- or
eel-like bodies. The two most terrestrially adapted groups were the medium-sized insectivorous or carnivorous
Seymouriamorpha
Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered reptiliomorphs, and most paleontologists may still accept this point of view, but some analyses suggest that seymouriamorphs are ...
and the mainly herbivorous
Diadectomorpha, with many large forms. The latter group has, in most analysis, the closest relatives of the
Amniotes.
[Laurin, M. (1996)]
Phylogeny of Stegocephalians
from the Tree of Life Web Project
The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth.
This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site ...
From aquatic to terrestrial eggs
Their terrestrial life style combined with the need to return to the water to lay
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s hatching to
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
Th ...
e (tadpoles) led to a drive to abandon the larval stage and aquatic eggs. A possible reason may have been competition for breeding ponds, to exploit drier environments with less access to open water, or to avoid predation on tadpoles by fish, a problem still plaguing modern amphibians.
[Duellman, W.E. & Trueb, L. (1994): Biology of amphibians. The Johns Hopkins University Press] Whatever the reason, the drive led to
internal fertilization
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For intern ...
and direct development (completing the tadpole stage within the egg). A striking parallel can be seen in the frog family
Leptodactylidae, which has a very diverse reproductive system, including foam nests, non-feeding terrestrial tadpoles and direct development. The Diadectomorphans generally being large animals would have had correspondingly large eggs, unable to survive on land.
Fully terrestrial life was achieved with the development of the amniote egg, where a number of membranous sacks protect the
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
and facilitate gas exchange between the egg and the atmosphere. The first to evolve was probably the
allantois, a sack that develops from the gut/yolk-sack. This sack contains the embryo's nitrogenous waste (
urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.
Urea serves an important ...
) during development, stopping it from poisoning the embryo. A very small allantois is found in modern amphibians. Later came the
amnion surrounding the fetus proper, and the
chorion
The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles ( amniotes). It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals), known as the vitellin ...
, encompassing the amnion, allantois, and yolk-sack.
Origin of amniotes
Exactly where the border between reptile-like amphibians (non-amniote reptiliomorphs) and amniotes lies will probably never be known, as the reproductive structures involved
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ize poorly, but various small, advanced reptiliomorphs have been suggested as the first true amniotes, including ''
Solenodonsaurus'', ''
Casineria'' and ''
Westlothiana''. Such small animals laid small eggs, 1 cm in diameter or less. Small eggs would have a small enough volume to surface ratio to be able to develop on land without the amnion and chorion actively effecting gas exchange, setting the stage for the evolution of true amniotic eggs.
Although the first true amniotes probably appeared as early as the
Middle Mississippian
Middle or The Middle may refer to:
* Centre (geometry), the point equally distant from the outer limits.
Places
* Middle (sheading), a subdivision of the Isle of Man
* Middle Bay (disambiguation)
* Middle Brook (disambiguation)
* Middle Creek (d ...
sub-epoch, non-amniote (or amphibian) reptiliomorph lineages coexisted alongside their amniote descendants for many millions of years. By the
middle Permian
The Guadalupian is the second and middle series/ epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ...
the non-amniote
terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
forms had died out, but several
aquatic non-amniote groups continued to the end of the Permian, and in the case of the
chroniosuchians survived the
end Permian mass extinction, only to die out prior to the end of the
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
. Meanwhile, the single most successful daughter-clade of the reptiliomorphs, the amniotes, continued to flourish and evolve into a staggering diversity of tetrapods including
mammals,
reptiles, and
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s.
Gallery
File:Proterogyrinus DB.jpg, '' Proterogyrinus'', an early embolomere
File:Pteroplax DB.jpg, '' Pteroplax'', an aquatic embolomere
File:Silvanerpeton1DB.jpg, '' Silvanerpeton'', an indeterminate Carboniferous reptiliomorph
File:Eldeceeon life restoration.png, ''Eldeceeon
''Eldeceeon'' is an extinct genus of reptiliomorph from the Mississippian (early Carboniferous) of Scotland. It is known from two fossil specimens found within the Viséan-age East Kirkton Quarry in West Lothian. The type and only species, '' ...
'', an indeterminate Carboniferous reptiliomorph
File:Chroniosaurus dongusDB12.jpg, '' Chroniosaurus'', a Permian chroniosuchian
File:Madygenerpeton pustulatus.jpg, '' Madygenerpeton'', a Triassic chroniosuchian
File:Pelodosotis1DB.jpg, '' Pelodosotis'', an ostodolepid
Ostodolepidae, also spelled Ostodolepididae, is an extinct family of Early Permian microsaurs. They are unique among microsaurs in that they were large, reaching lengths of up to , terrestrial, and presumably fossorial. Ostodolepid remains have b ...
" microsaur" from the group Lepospondyli
File:Diplocaulus vale21DB.jpg, '' Diplocaulus'', a diplocaulid
The Diplocaulidae ("double cauls") is an extinct family of lepospondyl amphibians that arose during the Late Carboniferous and died out in the Late Permian. They are distinguished from other amphibians, extinct and extant, by the presence of str ...
" nectridean" from the group Lepospondyli
File:Kotlassia prima1DB.jpg, '' Kotlassia'', an aquatic seymouriamorph
File:Solenodonsaurus1DB.jpg, '' Solenodonsaurus'', an "advanced" reptiliomorph
File:Casineria kiddi reconstruction.jpg, '' Casineria'', an amniote-like reptiliomorph
File:Tseajaia BW.jpg, '' Tseajaia'', a diadectomorph
File:Diasparactus1DB.jpg, ''Diasparactus
''Diasparactus'' is an extinct genus of diadectid reptiliomorphs, a group quite closely related to the amniotes, and paralleling some of their features. Like all advanced diadectids, ''Diasparactus'' was a herbivore, though not as large as its ...
'', a diadectid diadectomorph
See also
*
List of reptiliomorphs A list of reptiliomorphs, (excluding amniotes), throughout their time.
A
*Anthracosaurus
* Archeria
*Ariekanerpeton
B
*Bystrowiana
C
*Chroniosaurus
* Chroniosuchus
*Cricotus
D
* Diadectes
* Diasparactus
*Diplovertebron
*Discosauriscus
...
References
{{Taxonbar, from=Q134683