{{Short description|Extinct genus of amphibians}} {{Automatic taxobox | fossil_range = Early Permian, {{Fossil range|279.5|272.5|ref=<ref name=fossilworks/>}} | image = Tersomius dolesensis.jpg | image_caption = ''T. dolesensis'' skull | taxon = Tersomius | authority = E.C. Case, 1910 | type_species = ''Tersomius texensis'' | type_species_authority = E.C. Case, 1910 | subdivision_ranks = Species | subdivision = * ''Tersomius dolesensis'' * ''Tersomius mosesi'' * ''Tersomius texensis'' }}
'''''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).
== History of study == ''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.<ref>{{Cite journal|last=Case|first=Ermine Cowles|date=1910|title=New or little known reptiles and amphibians from the Permian (?) of Texas|journal=Bulletin of the American Museum of Natural History|volume=28|pages=163–181|hdl=2246/1394}}</ref> 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).<ref>{{Cite journal|last=Carroll|first=Robert L.|date=1964|title=Early evolution of the dissorophid amphibians|url=https://www.biodiversitylibrary.org/page/6311138#page/221/mode/1up|journal=Bulletin of the Museum of Comparative Zoology|volume=131 |issue=7 |pages=161–250|via=Biodiversity Heritage Library}}</ref> 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."<ref>{{Cite journal|last=Maddin|first=Hillary C.|last2=Fröbisch|first2=Nadia B.|last3=Evans|first3=David C.|last4=Milner|first4=Andrew R.|date=2013|title=Reappraisal of the Early Permian amphibamid ''Tersomius texensis'' and some referred material|journal=Comptes Rendus Palevol|language=en|volume=12|issue=7–8|pages=447–461|doi=10.1016/j.crpv.2013.06.007}}</ref> Material referred to ''Tersomius'' cf. ''texensis'' was reported from the early Permian South Grandfield locality in Oklahoma by Daly (1973).<ref>{{Cite journal|last=Daly|first=Eleanor|date=1973|title=A Lower Permian vertebrate fauna from southern Oklahoma |jstor=1303204 |journal=Journal of Paleontology|volume=47|issue=3|pages=562–589|issn=0022-3360}}</ref>
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.<ref name=":0">{{Cite journal|last=Anderson|first=Jason S.|last2=Bolt|first2=John R.|date=2013|title=New information on amphibamids (Tetrapoda, Temnospondyli) from Richards Spur (Fort Sill), Oklahoma|journal=Journal of Vertebrate Paleontology|volume=33|issue=3|pages=553–567|doi=10.1080/02724634.2013.726676|issn=0272-4634}}</ref> 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.
== Anatomy == 250px|thumb|Replica skull 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.<ref>{{Cite book|title=Handbuch der Paläoherpetologie Part 3A2. Temnospondyli|last=Schoch|first=Rainer R.|last2=Milner|first2=Andrew R.|publisher=Verlag Dr. Friedrich Pfeil|year=2014|isbn=9783931516260|editor-last=Sues|editor-first=Hans-Dieter|location=Stuttgart|oclc=580976}}</ref> 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.<ref name=":0" /> The poor understanding of ''T. mosesi'' often leads it to be excluded in discussion or diagnosing of the genus.
== Relationships == 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):<ref>{{Cite journal|last=Schoch|first=Rainer R.|date=2018|title=The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls|journal=Journal of Paleontology|volume=93|issue=1|pages=137–156|doi=10.1017/jpa.2018.67|issn=0022-3360|doi-access=free}}</ref> {{Clade|{{clade |1=Olsoniformes |label2=Amphibamiformes |2={{clade |1=''Eoscopus'' |2={{clade |1=''Platyrhinops'' |2={{clade |label1=Micropholidae |1={{clade |1='''''Tersomius''''' |2={{clade |1={{clade |1=''Pasawioops'' |2=''Micropholis''}} }} }} |2={{clade |label1=Amphibamidae |1={{clade |1=''Doleserpeton'' |2=''Amphibamus'' }} |2={{clade |1={{clade |1={{clade |1=''Gerobatrachus'' |2=''Georgenthalia'' }} |2={{clade |label1=Lissamphibia |1={{clade |1=''Eocaecilia'' |2={{clade |1=''Karaurus'' |2=''Triadobatrachus'' }} }} }} }} |label2=Branchiosauridae |2={{clade |1=''Branchiosaurus'' |2=''Apateon'' |3={{clade |1=''Leptorophus'' |2=''Schoenfelderpeton'' }} }} }} }} }} }} }} }}|label1=Xerodromes}} 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): {{Clade|{{clade |1={{clade |1=''Eoscopus'' |2={{clade |1=''Plemmyradytes'' |2={{clade |1=''Platyrhinops'' |2={{clade |1=''Doleserpeton'' |2={{clade |1=''Amphibamus'' |2={{clade |1=''Gerobatrachus'' |2={{clade |1=''Georgenthalia'' |2=Branchiosauridae}} }} }} }} }} }} }} |2={{clade |1='''''Tersomius dolesensis''''' |2={{clade |1={{clade |1='''''Tersomius texensis''''' |2=''Rubeostratilia''}} |2={{clade |1=''Micropholis'' |2=''Pasawioops''}} }} }} }}|label1=Amphibamiformes}}
==See also== {{Portal|Paleontology}} * Prehistoric amphibian * List of prehistoric amphibians
==References== {{Reflist|refs= <ref name=fossilworks>{{cite web |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=37035 |title=†''Tersomius'' Case 1910 |work=Paleobiology Database |publisher=Fossilworks |access-date=17 December 2021}}</ref> }}
{{Temnospondyli|D.}} {{Taxonbar|from=Q7705223}}
Category:Amphibamids Category:Dissorophidae Category:Prehistoric amphibian genera Category:Taxa named by Ermine Cowles Case Category:Fossil taxa described in 1910 Category:Permian amphibians of North America