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''Acleistorhinus'' (ah-kles-toe-RYE-nuss) 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
parareptile Parareptilia ("near-reptiles") is an extinct group of Basal (phylogenetics), basal Sauropsida, sauropsids ("Reptile, reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds ...
known from 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 ...
(middle
Kungurian In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian Epoch or Series. The Kungurian lasted between and million years ago (Ma). It was preceded by the Arti ...
stage) of
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
. It is notable for being the earliest known
anapsid An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. Traditionally, the Anapsida are considered the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Dia ...
reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...
yet discovered. The
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
of the lower
temporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...
of the
skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
of ''Acleistorhinus'' bears a superficial resemblance to that seen in early
synapsids Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...
, a result of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...
. Only a single
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, ''A. pteroticus'', is known, and it is classified in the
Family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Acleistorhinidae Acleistorhinidae is an extinct family of Late Carboniferous and Early Permian-aged ( Moscovian to Kungurian stage) parareptiles. It is defined as a node based clade including the last common ancestor of '' Acleistorhinus pteroticus'' and '' Co ...
, along with '' Colobomycter'' (also from the Early Permian of Oklahoma).


Etymology

''Acleistorhinus'' was first discovered and named by Eleanor Daly in 1969 in the Hennessey Formation of South Grandfield, Tillman county, Oklahoma. The name ''Acleistorhinus'' combines Greek ''rhin'' (ῥῑ́ν), meaning "nose," and akleistos, Greek for “unclosed.“


Description and Paleobiology


Skull

Although its total body length is unknown, an ''Acleistorhinus'' skull is about 3.5 centimetres long. From the dorsal side, the ''Acleistorhinus'' skull appears to have a triangular outline. The surface of the skull is generally smooth with a few small, shallow circular pits. Anteriorly, the snout is gently rounded. The elliptical external nares are each bordered by the maxilla. The tooth bearing portion of the premaxilla appears to be directed somewhat downward at its tip. Each premaxilla possess spaces for four teeth. The maxilla has a dorsal expansion immediately behind the nares forming the entire posterior border of the opening. This configuration resembles that of the procolophonids, and turtles, and results in the exclusion of the lacrimal from the posterior border of the nares. Slightly more than one third of the total length of the skull is contributed by the frontal. It is constricted anteriorly by the prefrontals, but otherwise expanded above the orbits. Generally, in early amniotes the largest element was the occiput of the supraoccipital. In ''Acleistorhinus'' the supraoccipital is rather plate-like. The reduction in the overall size of the supraoccipital allows for the development of large post-termporal fenestra, a characteristic of Reptilia.


Dentition

The marginal dentition is composed of conical teeth that are slightly recurved. No canine region is evident although the second maxillary tooth is slightly larger than the rest. The tooth-bearing portion of the maxilla extends posterior to the orbit. All the premaxillary teeth appear to be approximately the same size, and noticeably smaller than those on the maxilla. The maxillae have 11 and 13 on the right and left sides respectively, there is room for at least 17 teeth for each element. Smaller teeth are present along the sloping surface of the transverse flange, anterior to the large row of teeth. On the
parasphenoid The parasphenoid is a bone which can be found in the cranium of many vertebrates. It is an unpaired dermal bone which lies at the midline of the roof of the mouth. In many reptiles (including birds), it fuses to the endochondral (cartilage-derived ...
plate, two separate paired rows of teeth diverge posteriorly. The lateral-most rows sit on a ridge that runs the length of the main body of the parasphenoid. The tooth ridges are evident anteriorly but appear to terminate at the same level as the teeth on the transverse flange of the pterygoid.


Habitat and Diet

The Early
Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...
is marked by terrestrial plant diversification, in which insects evolved rapidly as they followed the plants into new habitats. ''Acleistorhinus'' is widely believed to be an
insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...
because its teeth are numerous, small and pointed. The back of the skull is wide resulting in the orbits being pushed forward. This would have offered a degree of binocular vision giving ''Acleistorhinus,'' a land-dwelling
insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...
, depth perception necessary for hunting fast moving objects.


Classification and Species

The genus ''Acleistorhinus'' belongs to the taxon
parareptilia Parareptilia ("near-reptiles") is an extinct group of basal sauropsids (" reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the en ...
along with Millerettidae, Lanthanosuchidae to whom it is a sister taxa, ''Macroleter'' and Procolophonia. As of present, there is only one known species of ''Acleistorhinus,'' known as ''Acleistorhinus pteroticus.'' A recent restudy, phylogenetic analysis, of ''Acleistorhinus'' indicates that this Early
Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...
amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...
from North America, the oldest known member of
parareptilia Parareptilia ("near-reptiles") is an extinct group of basal sauropsids (" reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the en ...
, is a sister taxon to Russian Lanchanosuchidae. In addition, the results support Laurin and Reisz (1995) hypothesis that Parareptilia is a monophyletic group, while differing in the number of synapomorphies diagnosing the clade. The recognition of ''Acleistorhinus'' and lanthanosuchids as sister-taxa presents new evidence for the hypothesis that parareptiles had a cosmopolitan distribution during the Paleozoic. This sister-group relationship is supported by twelve synapomorphies. Furthermore, when acknowledging ''Acleistorhinus,'' lanthanosuchids, and ''Macroleter'' nest within Parareptilia, it becomes evident through specific interrelationships within Amniota that Parareptilia is a monophyletic taxon. Using the tenet of minimum divergence time most recently discussed by Norell (1992) and Westphalian (1993), the earliest
parareptile Parareptilia ("near-reptiles") is an extinct group of Basal (phylogenetics), basal Sauropsida, sauropsids ("Reptile, reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds ...
must extend into at least the
Westphalian (stage) The Westphalian is a regional stage or age in the regional stratigraphy of northwest Europe, with an age between roughly 315 and 307 Ma (million years ago). It is a subdivision of the Carboniferous System or Period and the regional Silesian Ser ...
of the Upper
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 ...
. This suggests that the all major amniote clades
Diapsida Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The earliest traditionally identified diapsids, the araeosc ...
,
Synapsida Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rep ...
and
Parareptilia Parareptilia ("near-reptiles") is an extinct group of basal sauropsids (" reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the en ...
all diverged early in the evolutionary radiation of amniotes. At the very least parareptiles are more diverse and possess a richer fossil record than previously recognized.


Discovery

''Acleistorhinus'' was discovered by Daly in 1969, in the Early
Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...
outcrops of the Hennessey Formation, the locality of South Grandfield of southwestern Oklahoma. The Hennessey Formation is believed to be contemporaneous with the
Richards Spur Richards Spur is a Permian fossil locality located at the Dolese Brothers Limestone Quarry north of Lawton, Oklahoma. The locality preserves clay and mudstone fissure fills of a karst system eroded out of Ordovician limestone and dolomite, with t ...
locality near
Fort Sill Fort Sill is a United States Army post north of Lawton, Oklahoma, about 85 miles (137 km) southwest of Oklahoma City. It covers almost . The fort was first built during the Indian Wars. It is designated as a National Historic Landmark a ...
, Oklahoma, as they both possess a mixed
fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...
, which is generally disarticulated and incomplete. In addition, over 200 skulls and 500 specimens have been collected from South Grandfield, only one specimen of ''Acleistorhinus'' is known. It is very likely that this taxon is an erratic and would not normally preserve in the depositional environment that characterizes much of the Lower
Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...
of
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. The discovery of ''Acleistorhinus'' was far reaching because until the present only Synapida and Diapsida could trace their earliest known members to North America. Now parareptiles can also trace their earliest record from the same continent. It is very likely that all three major amniote clades Diapsida, Synapsida, and Parareptilia all diverged early during the evolutionary radiation that characterizes much of the Early Permian.


See also

* ''
Macroleter ''Macroleter'' is an extinct genus of nycteroleterid parareptile which existed in Oklahoma and Russia during the upper Permian period. It was a quite generalized primitive reptile, in many ways resembling their amphibian ancestors. It was first ...
'' * ''
Lanthanosuchidae Lanthanosuchidae is a family of procolophonomorph parareptile Parareptilia ("near-reptiles") is an extinct group of Basal (phylogenetics), basal Sauropsida, sauropsids ("Reptile, reptiles"), traditionally considered the sister taxon to Eurept ...
'' * ''
Parareptilia Parareptilia ("near-reptiles") is an extinct group of basal sauropsids (" reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the en ...
'' * ''
Chordate A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies) that distinguish them from ot ...
'' * ''
Reptilia Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and amniotic development. Living traditional reptiles comprise four orders: Testudines, Crocodilia, Squamata, and Rhynchocephalia. About 12,000 living spe ...
'' * ''
Synapsids Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...
''


References


External Source


More on parareptile
* Helpful list of parareptilia phylogeny
Permian Period
{{Taxonbar, from=Q3604579 Acleistorhinidae Cisuralian reptiles of North America Prehistoric reptile genera