| Hapsidopareion Temporal range: Permian, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | † Microsauria |
| Family: | † Hapsidopareiidae |
| Genus: | † Hapsidopareion Daly, 1973 |
| Species | |
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| Synonyms | |
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Hapsidopareion is an extinct genus of microsaur belonging to the family Hapsidopareiidae. Fossils have been found in the early Permian of Oklahoma. [1] [2]
Hapsidopareion was named in 1973 by American paleontologist Eleanor Daly based on material collected from the early Permian South Grandfield locality in southwestern Oklahoma. [1] The genus name is given for the Greek hapsido- ('arch') and -pareion ('cheek'). The species name, H. lepton, is given for the slightness of the animal. The taxon is known from several partial to complete skulls and possibly by some isolated postcranial material.
Hapsidopareion was originally differentiated from other microsaurs by the large temporal emargination, which produced other variable morphology of the circum-emargination bones (e.g., postorbital). It is similar to the more recently described Llistrofus pricei in this regard, but can be differentiated from L. pricei by features such as the absence of a quadratojugal and a frontal excluded from the orbit. [3] Because all specimens of H. lepton are notably smaller than those of L. pricei, and a number of anatomical differences are likely ontogenetically variable (e.g., contact between neural arch and centrum), some researchers considered that the former maybe represent a juvenile of the latter, but recent workers have maintained the separation of these taxa. [3] [4] Using high-resolution micro-CT scans of three skulls of the coeval Hapsidopareion, Jenkins et al. (2025) identified that many of the characters used to distinguish Llistrofus from it are shared by both taxa. Due to its larger size, they identified Llistrofus as representing a more mature ontogenetic stage of Hapsidopareion, and argued that the former should be regarded as a junior synonym of the latter. [5]
Hapsidopareion is the sister taxon to Llistrofus forms the family Hapsidopareiidae (traditionally called the 'Hapsidopareiontidae') within the Recumbirostra. The family is recognized by the greatly enlarged temporal emargination. [4] In their 2025 publication, Jenkins et al. discussed the possible synonymy of Hapsidopareion and Llistrofus. The results of their phylogenetic analyses are displayed in the cladogram below, where they found recumbirostrans to be a clade along the amniote stem: [5]
Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco, lepospondyls lived from the Visean stage of the Early Carboniferous to the Early Permian and were geographically restricted to what is now Europe and North America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard-like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large, and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in the Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel, who coined the name to include some tetrapods from the Paleozoic that shared some specific characteristics in the notochord and teeth. Lepospondyls have sometimes been considered to be either related or ancestral to modern amphibians or to Amniota. It has been suggested that the grouping is polyphyletic, with aïstopods being primitive stem-tetrapods, while recumbirostran microsaurs are primitive reptiles.
Microsauria is an extinct, possibly polyphyletic order of tetrapods from the late Carboniferous and early Permian periods. It is the most diverse and species-rich group of lepospondyls. Recently, Microsauria has been considered paraphyletic, as several other non-microsaur lepospondyl groups such as Lysorophia seem to be nested in it. Microsauria is now commonly used as a collective term for the grade of lepospondyls that were originally classified as members of Microsauria.
Colobomycter is an extinct genus of acleistorhinid parareptile known from the Early Permian of Oklahoma.
Batropetes is an extinct genus of brachystelechid recumbirostran "microsaur". Batropetes lived during the Sakmarian stage[a] of the Early Permian. Fossils attributable to the type species B. fritschi have been collected from the town of Freital in Saxony, Germany, near the city of Dresden. Additional material has been found from the Saar-Nahe Basin in southwestern Germany and has been assigned to three additional species: B. niederkirchensis, B. palatinus, and B. appelensis.
Euryodus is an extinct genus of microsaur within the family Gymnarthridae. Euryodus is a Lepospondyl from the clade Microsauria that lived during the Early Permian. The name comes from Greek, meaning ‘broad-tooth’. It has been found in the southern half of North America, from its original discovery in Texas up to Utah.
Llistrofus is an extinct genus of early Permian microsaur within the family Hapsidopareiidae that is known from Oklahoma. It may be a junior synonym and more mature form of the coeval Hapsidopareion.
Odonterpeton is an extinct genus of "microsaur" from the Late Carboniferous of Ohio, containing the lone species Odonterpeton triangulare. It is known from a single partial skeleton preserving the skull, forelimbs, and the front part of the torso. The specimen was found in the abandoned Diamond Coal Mine of Linton, Ohio, a fossiliferous coal deposit dated to the late Moscovian stage, about 310 million years ago.
Rhynchonkos is an extinct genus of rhynchonkid microsaur. Originally known as Goniorhynchus, it was renamed in 1981 because the name had already been given to another genus; the family, likewise, was originally named Goniorhynchidae but renamed in 1988. The type and only known species is R. stovalli, found from the Early Permian Fairmont Shale in Cleveland County, Oklahoma. Rhynchonkos shares many similarities with Eocaecilia, an early caecilian from the Early Jurassic of Arizona. Similarities between Rhynchonkos and Eocaecilia have been taken as evidence that caecilians are descendants of microsaurs. However, such a relationship is no longer widely accepted.
Pariotichus is an extinct genus of gymnarthrid microsaurs from the early Permian of Texas.
Tersomius is an extinct genus of dissorophoid temnospondyl within the family Micropholidae. It is known from the early Permian of North America.
Brachystelechidae is an extinct family of Early Permian microsaurs. The family was first named by Robert L. Carroll and Pamela Gaskill in 1978, with the only member being Brachystelechus fritschi. Brachystelechus fritschi has since been reassigned to the genus Batropetes. Genera assigned to the family include: Batropetes, from Germany; Carrolla, from Texas; Quasicaecilia, also from Texas; Diabloroter, from the Mazon Creek lagerstätte of Illinois; and Bromerpeton from the Tambach Formation of Germany.
Tuditanomorpha is a suborder of microsaur tetrapods. Tuditanomorphs lived from the Late Carboniferous to the Early Permian and are known from North America and Europe. Tuditanomorphs have a similar pattern of bones in the skull roof. Tuditanomorphs display considerable variability, especially in body size, proportions, dentition, and presacral vertebral count. Currently there are four families of tuditanomorphs, with two being monotypic. Tuditanids first appear in the Lower Pennsylvanian. Goniorhynchidae, Hapsidopareiidae, and Trihecatontidae appear in the Late Pennsylvanian and Early Permian.
Gymnarthridae is an extinct family of the group Recumbirostra. Gymnarthrids are known from Europe and North America and existed from the Late Carboniferous through the Early Permian. Remains have been found from the Czech Republic, Nova Scotia, Illinois, Texas, and Oklahoma. Previously they were considered tuditanomorph microsaurs.
Ostodolepidae, also spelled Ostodolepididae, is an extinct family of Early Permian tetrapods. Initially they were considered microsaurs, but later were assigned to the group Recumbirostra. Ostodolepids were relatively large, reaching lengths of up to 2 feet (61 cm), terrestrial, and presumably fossorial. Ostodolepid remains have been found from Early Permian beds in Texas, Oklahoma, and Germany.
Nannaroter is an extinct genus of Recumbirostran tetrapod within the family Ostodolepidae.
Hapsidopareiidae is an extinct family of microsaurs. Hapsidopareiids are known from the Early Permian of the United States and possibly Germany and the Czech Republic.
Microleter is an extinct genus of basal procolophonomorph parareptiles which lived in Oklahoma during the Early Permian period. The type and only known species is Microleter mckinzieorum. Microleter is one of several parareptile taxa described from the Richards Spur fissure fills, and can be characterized from its high tooth count, lacrimal/narial contact, short postfrontal, and slit-like temporal emargination edged by the postorbital, jugal, squamosal, and quadratojugal. Contrary to Australothyris, which had a similar phylogenetic position as a basal procolophonomorph, Microleter suggests that early parareptile evolution occurred in Laurasia and that multiple lineages developed openings or emarginations in the temporal region.
Recumbirostra is a clade of tetrapods which lived during the Carboniferous and Permian periods. They are thought to have had a fossorial (burrowing) lifestyle and the group includes both short-bodied and long-bodied snake-like forms. At least one species, the long-bodied molgophid Nagini mazonense, lost its forelimbs entirely. Recumbirostra includes the families Pantylidae, Gymnarthridae, Ostodolepidae, Rhynchonkidae and Brachystelechidae, with additional families such as Microbrachidae and Molgophidae being included by some authors. Brachystelechidae and Molgophidae have also been grouped together in the suggested clade Chthonosauria.
Huskerpeton is an extinct genus of recumbirostran from the Early Permian period. They belong to the order Microsauria, which was established in 1863 by Dawson, and was quickly expanded to include many different small taxa. They lived in what is now Nebraska and Kansas. The holotype of Huskerpeton was uncovered at the Eskridge formation in Nebraska, which is part of how it got its name.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2025.
