Proxilodon Bonneri
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''Proxilodon'' 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
recumbirostra 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 ...
n
microsaur 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 s ...
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 ...
Speiser Formation of
Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
, United States. It contains a single species, ''Proxilodon bonneri'', (formerly "
Euryodus ''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 ...
" ''bonneri'').


History of study

There is only one known specimen of ''Proxilodon bonneri'', the former holotype of ''Euryodus bonneri'', named by Schultze & Foreman (1981). It was collected in 1976 by Brian Foreman from a roadcut site in Kansas in the lower Speiser Formation (often called the Speiser Shale) that preserves primarily aquatic vertebrates, such as the
lungfish Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, inc ...
'' Gnathorhiza'', the dvinosaur
temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...
'' Acroplous vorax'', the
nectridean Nectridea is an extinct order of lepospondyl tetrapods from the Carboniferous and Permian periods, including animals such as ''Diplocaulus''. In appearance, they would have resembled modern newts or aquatic salamanders, although they are not clos ...
lepospondyl 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 Earl ...
''
Diplocaulus ''Diplocaulus'' (meaning "double stalk") is an extinct genus of lepospondyl amphibians which lived from the Late Carboniferous to the Late Permian of North America and Africa. ''Diplocaulus'' is by far the largest and best-known of the lepospond ...
'', and the lysorophian '' Lysorophus tricarinatus''. The species was named after Orville Bonner, who prepared the specimen, a complete skull with the left lower jaw in articulation and associated vertebrae and a fragmentary humerus. Huttenlocker et al. (2013) identified numerous differences from other species of ''Euryodus'' and erected the new genus ''Proxilodon'', derived from a Latinized version of the Greek 'Euryodus,' which means 'broad-tooth' and which was the original taxonomic identification; 'proxilus' in Latin for broad/wide, and '-odon' refers to 'tooth.'


Anatomy

As with
gymnarthrids 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, I ...
like ''Euryodus'', ''Proxilodon'' possesses a long postorbital region and a slightly convex occiput, but it also has a much narrower skull than is typical of ''Euryodus'' and a higher premaxillary tooth count, among other features, that differentiate it from gymnarthrids at large. Other features listed in the diagnosis include a small notch in the premaxilla that articulates with the nasal, a nasal longer than it is broad (in line with the generally narrow skull), and the absence of a pineal foramen, instead being replaced by a shallow fossa. The holotype skull is typically sized for 'microsaurs,' measuring slightly less than 19 mm in length. Most of the internal anatomy is obscured by the articulation with the skull.


Relationships

A phylogenetic analysis of the position of ''Proxilodon'', and another novel taxon, ''
Huskerpeton ''Huskerpeton'' (“Husker” after the University of Nebraska “corn huskers” and “-erpeton” meaning creeping in Greek) is an extinct genus of recumbirostran from the Early Permian period. They belong to the order Microsauria, which was e ...
'', by Huttenlocker et al. (2013) recovered ''Proxilodon'' as a recumbirostran microsaur within a clade formed by gymnarthrids,
ostodolepids Ostodolepidae, also spelled Ostodolepididae, is an extinct family (biology), family of Early Permian tetrapods. Initially they were considered microsaurs, but later were assigned to the group Recumbirostra. Ostodolepids were relatively large, re ...
, and their relatives. Below is the topology recovered by those authors:


References

{{Taxonbar, from=Q16757765 Fossil taxa described in 2013 Cisuralian amphibians of North America Paleontology in Kansas