| Tersomius Temporal range: Early Permian, | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | † Temnospondyli |
| Family: | † Micropholidae |
| Genus: | † Tersomius E.C. Case, 1910 |
| Type species | |
| Tersomius texensis E.C. Case, 1910 | |
| Species | |
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Tersomius is an extinct genus of dissorophoid temnospondyl within the family Micropholidae. It is known from the early Permian of North America (Oklahoma and Texas).
Tersomius was first named in 1910 by American paleontologist E.C. Case based on a partial skull collected from the Archer City Formation of Texas. [2] The type species is T. texensis, in reference to its geographic provenance. The brief original description was supplemented by a lengthier redescription of the holotype and description of new material by Carroll (1964). [3] At least two of these specimens do not belong to any species of Tersomius and were reassigned by Maddin et al. (2013), which has led some authors to consider it as a potential "wastebasket taxon." [4] Material referred to Tersomius cf. texensis was reported from the early Permian South Grandfield locality in Oklahoma by Daly (1973). [5]
A second species of Tersomius, T. mosesi, was named by Olson (1970) for Amos Moses, the property owner of the land in Oklahoma where the material was collected from. There are several dozen reported specimens for T. mosesi, but almost all of them are in poor condition and the osteology of this species remains poorly understood. Olson differentiated it from T. texensis mostly on the basis of notably fewer marginal teeth in the jaw. A third species of Tersomius, T. dolesensis, was named by Anderson & Bolt (2013) from the Richards Spur locality in Oklahoma. [6] It is differentiated from all other amphibamiforms by the presence of enlarged teeth along the palatine ramus of the vomer and is distinguished from T. texensis by a posteriorly restricted postorbital and a posteriorly extensive jugal.
The most recent revision of the genus is that of Schoch & Milner (2014), who list a combination of seven features and two plesiomorphies: (1) nearly circular outline of skull with curved maxilla; (2) prefrontal and postfrontal separated; (3) preorbital region equal to skull table in length; (4) internarial fenestra present; (5) teeth variably monocuspid and bicuspid; (6) vomer with both medial and lateral fangs; (7) palatine lacking denticles; (8) long supratemporal; (9) postparietal longer than tabular. [7] Most of these features are not unique to Tersomius (the combination being unique), as evidenced by the diagnosis of Anderson & Bolt (2013), who list an elongate tabular and a medial curvature of the maxillary arcade at the position of the quadrate (shared with Doleserpeton , T. texensis, and Micropholis ) as diagnostic. [6] The poor understanding of T. mosesi often leads it to be excluded in discussion or diagnosing of the genus.
Like other amphibamiforms that were described early in the 20th century, Tersomius has sometimes been listed as a dissorophid, but this was often the result of a lack of distinction between amphibamiforms and dissorophids for much of the 20th century. Its position within Amphibamiformes (the traditional Amphibamidae) is well-supported by modern computer-assisted phylogenetic analyses. Tersomius texensis is usually utilized as the representative of the genus in most analyses in which it is recovered as being closely related to Micropholis and Pasawioops, forming the Micropholidae. Below is a phylogeny of dissorophoids from Schoch (2018): [8]
| Xerodromes |
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The placement of Tersomius dolesensis within Tersomius remains somewhat disputed because it is not recovered as the sister taxon of T. texensis in recent analyses by Anderson & Bolt (2013; the original description) and Maddin et al. (2013). In the former, T. texensis was excluded from the analysis, and T. dolesensis was recovered as the sister taxon to Plemmyradytes . In the latter, both species of Tersomius were included and were not resolved as sister taxa. Below is the result of the analysis of Maddin et al. (2013):
| Amphibamiformes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Cacops, is a genus of dissorophid temnospondyls from the Kungurian stage of the early Permian of the United States. Cacops is one of the few olsoniforms whose ontogeny is known. Cacops fossils were almost exclusively known from the Cacops Bone Bed of the Lower Permian Arroyo Formation of Texas for much of the 20th century. New material collected from the Dolese Brothers Quarry, near Richards Spur, Oklahoma in the past few decades has been recovered, painting a clearer picture of what the animal looked and acted like.
Dissorophidae is an extinct family of medium-sized, temnospondyl amphibians that flourished during the late Carboniferous and early Permian periods. The clade is known almost exclusively from North America.
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 Jurassic and Cretaceous periods. Fossils have been found on every continent. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis, and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales and armour-like bony plates, that distinguish them from modern amphibians (lissamphibians).
Trematopidae is a family of dissorophoid temnospondyl spanning the late Carboniferous to the early Permian. Together with Dissorophidae, the family forms Olsoniformes, a clade comprising the medium-large terrestrial dissorophoids. Trematopids are known from numerous localities in North America, primarily in New Mexico, Oklahoma, and Texas, and from the Bromacker quarry in Germany.
Anconastes is an extinct genus of dissorophoid temnospondyl within the family Trematopidae. It is known from two specimens from the Late Carboniferous Cutler Formation of north-central New Mexico in the southwestern United States. The genus name derives from two Greek roots, ankos and nastes ("inhabitant"), which refers to the type locality of El Cobre Canyon where the specimens were found. The specific name is derived from the Latin word vesperus ("western"). The more complete specimen, the holotype, is a partial skull with articulated mandibles and a substantial amount of the postcranial skeleton. The less complete specimen, the paratype, consists only of the right margin of the skull with an articulated mandible.
Broiliellus is an extinct genus of dissorophoid temnospondyl within the family Dissorophidae. Broiliellus is most closely related to the genus Dissorophus, and both have been placed in the subfamily Dissorophinae. Broiliellus is known from five species from the Early Permian: the type species is Broiliellus texensis, and the other species are Broiliellus brevis,Broiliellus olsoni, Broiliellus arroyoensis, and Broiliellus reiszi. An additional species, Broiliellus novomexicanus, which was originally named Aspidosaurus novomexicanus, is now thought to fall outside the genus as a member of the subfamily Eucacopinae.
Ecolsonia is an extinct genus of trematopid temnospondyl. Its phylogenetic position within Olsoniformes has been historically debated, but it is presently considered to be a trematopid.
Micropholis is an extinct genus of dissorophoid temnospondyl. Fossils have been found from the Lystrosaurus Assemblage Zone of the Karoo Basin in South Africa and are dated to the Induan. Fossils have also been found from the lower Fremouw of Antarctica.Micropholis is the only post-Permian dissorophoid and the only dissorophoid in what is presently the southern hemisphere and what would have been termed Gondwana during the amalgamation of Pangea.
The Amphibamidae are an extinct family of dissorophoid temnospondyls known from Late Carboniferous-Early Permian strata in the United States.
Pasawioops is an extinct genus of early Permian dissorophoid temnospondyl within the clade Amphibamiformes.
Rubeostratilia is an extinct genus of amphibamiform temnospondyl from the early Permian of Texas. It is known from a single skull. This genus was named by Hélène Bourget and Jason S. Anderson in 2011, and the type species is Rubeostratilia texensis. The genus name comes from the Latin translation of 'redbeds' in reference to the Texas redbeds that produced both the holotype and many other early Permian fossils. The specific name is for the state of Texas. The holotype and only known specimen was collected in 1941 from the Nocona Formation exposures in Clay County by a Works Projects Administration project that was transferred to the Field Museum of Natural History through an interinstitutional exchange with the Texas Memorial Museum.
Plemmyradytes is an extinct genus of dissorophoid temnospondyl from the early Permian. It is an amphibamiform from the Eskridge Formation exposures of Nebraska. The type species is Plemmyradytes shintoni. The genus name derives from the Greek plemmyris and dytes ('diver'), while the specific name honors John Shinton, a fossil preparator at the Denver Museum of Natural History where all known specimens of this taxon are reposited following collection in the late 20th century.
Olsoniformes is a clade of dissorophoid temnospondyls. It includes the families Dissorophidae and Trematopidae. Most members of the clade were highly adapted to a terrestrial lifestyle. The clade was named in 2008 and is defined as the least inclusive clade containing Dissorophus multicinctus and Acheloma cumminsi but not Amphibamus grandiceps, Micromelerpeton credneri, and Apateon pedestris. Olsoniforms share various features such as a stout and low ilium and a thin cultriform process.
Perryella is an extinct genus of dvinosaurian(?) temnospondyl from the Permian of Oklahoma.
Parioxys is an extinct genus of temnospondyl amphibian from the Early Permian of Texas.
Branchiosauridae is an extinct family of small amphibamiform temnospondyls with external gills and an overall juvenile appearance. The family has been characterized by hundreds of well-preserved specimens from the Permo-Carboniferous of Middle Europe. Specimens represent well defined ontogenetic stages and thus the taxon has been described to display paedomorphy (perennibranchiate). However, more recent work has revealed branchiosaurid taxa that display metamorphosing trajectories. The name Branchiosauridae refers to the retention of gills.
Reiszerpeton is an extinct genus of dissorophid temnospondyl known from the Early Permian Archer City Formation of Texas. It is known solely from the holotype, MCZ 1911, a complete skull. This specimen was originally referred to the amphibamiform Tersomius texensis. A reappraisal of the holotype of T. texensis and a number of other referred specimens by Maddin et al. (2013) noted a number of differences from both T. texensis and amphibamiforms more broadly that suggested affinities with the Dissorophidae. This was confirmed by a phylogenetic analysis, which placed it as the sister taxon to the Eucacopinae. Reiszerpeton is known only from the type species, R. renascentis, which was named for Canadian paleontologist Robert Reisz. The species name refers to the recognition of Reisz as a "renaissance paleontologist." It is differentiated from other dissorophids by its small size, small and more numerous maxillary teeth, smooth cranial ornamentation, and greater distance between the orbit and the otic notch.
Nanobamus is an extinct genus of amphibamiform temnospondyl amphibian. The type species is Nanobamus macrorhinus. The type specimen is UCLAVP 3686, a skull recovered from the Lower Permian Arroyo Formation.
The Micropholidae are an extinct family of dissorophoid euskelian temnospondyls known from Late Carboniferous to Early Triassic strata in the United States and South Africa.
Amphibamiformes is an unranked clade with Dissorophoidea created by Schoch (2018). It encompasses all of the taxa traditionally considered to be "amphibamids", branchiosaurids, and hypothetically lissamphibians under the traditional temnospondyl hypothesis of lissamphibian origins. These taxa are typically small-bodied dissorophoids and form the sister group to Olsoniformes, which comprises dissorophids and trematopids.
