''Abyssomedon'' (meaning "Guardian of the Abyss") 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 a

nyctiphruretid Nyctiphruretidae is an extinct family of hallucicranian parareptiles known from the late Early to the late Middle Permian of European Russia and south-central United States. Nyctiphruretidae was named by Efremov in 1938. The type genus is '' N ...

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

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 ...

(

Artinskian In the geologic timescale, the Artinskian is an age (geology), age or stage (stratigraphy), stage of the Permian. It is a subdivision of the Cisuralian Epoch (geology), Epoch or series (stratigraphy), Series. The Artinskian likely lasted between ...

age) fissure fills at

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 ...

Comanche County, Oklahoma Comanche County is a County (United States), county located in the U.S. state of Oklahoma. As of the 2020 United States census, 2020 census, the population was 121,125, making it the fifth-most populous county in Oklahoma. Its county seat is L ...

, south-central United States. It contains a single species, ''Abyssomedon williamsi'', which represents oldest known nyctiphruretid species and the first to be discovered in North America.

Discovery

''Abyssomedon'' is known solely from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

BMRP 2008 33a, a partial

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

housed at the

Burpee Museum of Natural History The Burpee Museum of Natural History is located along the Rock River (Mississippi River), Rock River in downtown Rockford, Illinois, United States, at 737 North Main Street. Museum history The museum was created as a Works Progress Administrat ...

Rockford, Illinois Rockford is a city in Winnebago County, Illinois, Winnebago and Ogle County, Illinois, Ogle counties in the U.S. state of Illinois. Located in far northern Illinois on the banks of the Rock River (Mississippi River tributary), Rock River, Rockfor ...

. The specimen consists of a semi-articulated partial

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 ...

and disarticulated but associated

postcrania The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...

l remains. BMRP 2008 33a was discovered in 2008 in a

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

and conglomerate nodule found at

Oklahoma Museum of Natural History The Sam Noble Oklahoma Museum of Natural History is the officially designated natural history museum for the State of Oklahoma, located on the campus of the University of Oklahoma. The museum was founded in 1899 by an act of the Oklahoma Territ ...

(OMNH) Locality V51. This site, known as

, is located just west of U.S. Highways 62 & 281, 10.5 miles south of

Apache The Apache ( ) are several Southern Athabaskan language-speaking peoples of the Southwestern United States, Southwest, the Southern Plains and Northern Mexico. They are linguistically related to the Navajo. They migrated from the Athabascan ho ...

and 6 miles north of

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 ...

, of

. The fossils of Richards Spur are found in Early Permian fissure fills in Ordovician limestone. ''Abyssomedon'' was first described and named by Mark J. MacDougall and Robert R. Reisz in

2014 The year 2014 was marked by the surge of the Western African Ebola epidemic, West African Ebola epidemic, which began in 2013, becoming the List of Ebola outbreaks, most widespread outbreak of the Ebola, Ebola virus in human history, resul ...

and the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''Abyssomedon williamsi''. The generic name is derived from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''Abyssos'', meaning "deep pit", and ''-medon'', meaning "guardian", in reference to the cave system at Richards Spur. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''williamsi'' honor the collector of the

Mr. Scott Williams, a paleontologist at the Burpee Museum.

Classification

The following

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 ...

is simplified after the

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

of MacDougall and Reisz (2014) and shows the placement of ''Abyssomedon'' within

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 ...

. Relationships within bolded

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

s are not shown.

Paleoecology

The Richards Spur locality preserves a system of Early Permian sediments and fossils trapped in a cave eroded out of Ordovician Arbuckle Limestone. The Permian sediments of Richards Spur may be equivalent to the

Garber Formation The Garber Sandstone is a geologic formation from the Permian Period in Oklahoma. It serves as an important aquifer, the Garber-Wellington Aquifer, in Logan, Oklahoma, and Cleveland counties of central Oklahoma. The upper portion of the Garber i ...

(also known as the

Wellington Formation The Wellington Formation is an Cisuralian, Early Permian geologic Formation (geology), formation in Kansas and Oklahoma. The formation's Strataca, Hutchinson Salt Member is more recognized by the community than the formation itself, and the salt ...

) elsewhere in Oklahoma, or the

Arroyo Formation The Arroyo Formation, sometimes termed the Lower Clear Fork Formation, is a geologic formation in Texas.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 ...

. Richards Spur presents a rich Early Permian

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

paleofauna, including species of

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 ...

seymouriamorph Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest that seymouria ...

s, basal

synapsid 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 ...

s, basal

eureptile Sauropsida (Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinosaur ...

s and many species of

s apart from ''Abyssomedon'', including the basal '' Microleter mckinzieorum'', the

bolosaurid Bolosauridae is an extinct family of parareptiles known from the latest Carboniferous ( Gzhelian) or earliest Permian ( Asselian) to the early Guadalupian epoch (latest Roadian stage) of North America, China, Germany, Russia and France. The bolo ...

Bolosaurus grandis ''Bolosaurus'' (from Ancient Greek ''bolos'', "lump" + ''sauros'': lizard]) is an extinct genus of bolosaurid reptile from the Cisuralian Epoch (geology), epoch (middle Sakmarian to early Kungurian stages) of North Asia and North America (Red Be ...

'', and the

lanthanosuchoid Lanthanosuchoidea is an extinct superfamily of ankyramorph parareptiles from the middle Pennsylvanian to the middle Guadalupian epoch (Moscovian - Wordian stages) of Europe, North America and Asia. It was named by the Russian paleontologist Iva ...

s such as ''

Colobomycter pholeter ''Colobomycter'' is an extinct genus of acleistorhinid parareptile known from the Early Permian of Oklahoma. Discovery The type species, ''Colobomycter pholeter'', was first described from fossil remains in 1958, at which time it was believed ...

'', '' Delorhynchus priscus'', ''

Delorhynchus cifellii ''Delorhynchus'' is an extinct genus of lanthanosuchoid parareptile known from the late Early Permian (Artinskian age) Garber Formation of Comanche County, Oklahoma. It contains three species: the type species ''D. priscus'' is based on a serie ...

'', and ''

Feeserpeton oklahomensis ''Feeserpeton'' is an extinct genus of parareptile from the Early Permian of Richard's Spur, Oklahoma. It is known from a single species, ''Feeserpeton oklahomensis'', which was named in 2012 on the basis of a nearly complete skull. ''Feeserpeton ...

.'' A speleotherm was used to Uranium-Lead date the deposits to 289 ± 0.86 million years ago, corresponding to the

stage. However, the deposits were likely deposited over several million years, as evidenced by wider speleotherm sampling.

References

{{Taxonbar, from=Q21070644 Fossil taxa described in 2014 Procolophonomorpha Cisuralian reptiles of North America Paleontology in Oklahoma Prehistoric reptile genera