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Temporal range: 305.9–272.5 Ma
Skeleton of Acheloma cumminsi in the Field Museum of Natural History.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Order: Temnospondyli
Clade: Olsoniformes
Family: Trematopidae
Williston, 1910


Trematopidae is a family of dissorophoid temnospondyls spanning the late Carboniferous to the early Permian. Together with Dissorophidae, the family forms Olsoniformes, a clade comprising the medium-large terrestrial dissorophoids. Trematopids are known from numerous localities in North America, primarily in New Mexico, Oklahoma, and Texas, and from the Bromacker quarry in Germany.

History of study

The clade Trematopidae was first proposed by American paleontologist S.W. Williston in 1910, although it was named as "Trematopsidae" following the historical (but inaccurate) derivation from the genus "Trematops" (now synonymized with Acheloma).[1] British paleontologist D.M.S. Watson proposed a related clade in 1919, Achelomidae, for Acheloma, based on perceived differences separating the taxa;[2] this is now considered a junior synonym of Trematopidae following guidelines of historical precedent.

19th century history

In 1882, American paleontologist Edward Drinker Cope named Acheloma cumminsi based on material collected from the early Permian of Texas.[3] This is technically the first trematopid to be named, although the holotype of Mordex calliprepes was named a year earlier as a species of Limnerpeton by Czech paleontologist Antonin Fritsch in 1881 (one year prior);[4] the status of Mordex as a trematopid remained debated however until the revision by Milner (2018).[5]

20th century history

In the first half of the 20th century, American paleontologist S.W. Williston named a new genus from the early Permian of Texas, Trematops.[6] At the time, most workers regarded it as only distantly related to Cope's Acheloma.[7] Two additional species of Trematops were named in short order, Trematops thomasi from Oklahoma, named by American paleontologist Maurice Mehl,[8] and Trematops willistoni from Texas, named by American paleontologist E.C. Olson in 1941.[9] Both are now regarded as junior synonyms of Acheloma cumminsi. Olson also named two species of Acheloma, A. whitei and A. pricei; both are now regarded as belonging to Phonerpeton.[10] In the same paper that he named these taxa, Olson also provided the first review of the Trematopidae, synthesizing all of the known material and providing updated taxonomic frameworks.

The second half of the 20th century saw an increase in trematopid research. In 1956, Olson named a new genus and species of trematopid from the Vale Formation of Texas, Trematopsis seltini;[11] this is now regarded as a junior synonym of the dissorophid Cacops aspidephorus.[12] In 1969, American paleontologist Peter Vaughn described the first trematopid from New Mexico, Ecolsonia cutlerensis, named for the contemporaneous Olson and the Cutler Formation from which the holotype was collected. A re-description of this taxon based on substantial new material, was completed in 1985 by a team led by American paleontologist David Berman from the Carnegie Museum of Natural History.[13] In 1970, Olson named a new species of Trematops from the early Permian of Ohio, "Trematops stonei";[14] this is the only occurrence of Acheloma/Trematops outside of Texas and Oklahoma but is now accepted to be a junior synonym of Acheloma cumminsi. In 1973, American paleontologist Theodore Eaton named Actiobates peabodyi, the first and only trematopid from Kansas and the oldest trematopid in North America.[15] Eaton also challenged the longstanding separation of trematopids and dissorophids, synonymizing them under Dissorophidae, but this has not been supported or maintained by subsequent workers. Additional material from the Garnett quarry where Actiobates was discovered, assigned to "Hesperoherpeton garnettense" may also belong to Actiobates.[16] In 1974, American paleontologist John Bolt published two papers, one describing the first trematopid material from the fossil-rich site near Richards Spur, Oklahoma,[17] and the a second exploring the function of the elongate naris in trematopids.[18] In 1985, Olson described a purported larval specimen of a trematopid;[19] this was subsequently challenged by Canadian paleontologist David Dilkes in 1991,[20] and the specimen is now regarded to be an adult specimen of an amphibamiform dissorophoid.[21][22] In 1987, the second trematopid from New Mexico, Anconastes vesperus, named for its discovery in El Cobre Canyon in western North America, was described by the same team of Berman, Reisz, and Eberth who described Ecolsonia.[23] Also in 1987, Dilkes and Robert R. Reisz of the University of Toronto re-described the holotypes of Acheloma cumminsi and Trematops milleri and identified them as synonyms; A. cumminsi takes precedence, having been described first. In 1990, Dilkes named a new taxon of trematopid from the early Permian of Texas, Phonerpeton pricei.[10] A study on developmental changes to the characteristic elongate naris of trematopids was undertaken using primarily material from Phonerpeton by Dilkes in 1993.[24] In 1998, the first trematopid from Europe, Tambachia trogallas, from the early Permian Bromacker quarry in Germany was named by a team led by American paleontologist Stuart Sumida of California State University, San Bernardino.[25]

21st century history

The 21st century has seen a renewed flurry of research into trematopids. In 2010, a team led by Berman described a new taxon from the late Carboniferous of Pennsylvania, Fedexia striegeli, named after the FedEx Corporation on whose land the holotype was found and after Adam Striegel, the discoverer.[26] In 2011, another team led by Berman described a new taxon from the Bromacker quarry, Rotaryus gothae, named after the Rotary Club of Gotha's contributions to the excavation of the locality.[27] Also in 2011, Canadian paleontologists Brendan Polley and Reisz named a new species of Acheloma from the early Permian Richards Spur locality in Oklahoma, Acheloma dunni, named for Brent Dunn, one of the collectors at the locality.[28] A study examining development changes in this species was published the previous year by Canadian paleontologists Hillary C. Maddin, Jason S. Anderson, and Reisz,[29] although the species name was not formalized by the time of that publication. In their 2014 review of the earlier temnospondyls, Schoch & Milner resurrected a second species of Phonerpeton, P. whitei,[21] following Olson's original species distinctions.[9] Data from the pes of Acheloma cumminsi was included in a broader survey of the carpus and tarsus in temnospondyls by Dilkes in 2015.[30] In 2018, British paleontologist Andrew R. Milner revised the Nýřany trematopids, clarifying the complicated history of Mordex calliprepes and erecting a new taxon, Mattauschia laticeps.[5] In 2019, a team led by American paleontologist Bryan M. Gee published the first description of computed tomography (CT) data of a trematopid in the form of a small specimen from the Richards Spur locality that they referred to cf. Acheloma.[31]


Trematopids have typically been identified by the presence of a noticeably enlarged naris that is often sub-divided in Permian forms such as Acheloma. They are also among the largest of the dissorophoids, with some specimens of Acheloma exceeding 18 cm in skull length and thus being rivaled only by middle Permian dissorophids such as Anakamacops. Schoch & Milner (2014) diagnosed trematopids by the following features: (1) greatly expanded naris replacing much of the lacrimal; (2) medially situated narial flange meeting antorbital bar; (3) otic notch with a ventral margin sloping at less than 45-degrees in large individuals; (4) a medial inflection of the rim of the adductor fossa; (5) a pterygoid-vomer contact; (6) a triangular patch of denticles on the basal plate of the parasphenoid; and (7) a humerus with a supinator process.[21] Milner (2018) further refined this based on his restudy of Mordex, including only characters 1, 3, and 5 from Schoch & Milner (2014), noting that some typical trematopid features are either not known or are not present in the primitive Mattauschia and Mordex.[5]

The function of the naris remains largely unresolved. Olson (1941) suggested that the anterior half served the typical function of smell detection and that the posterior half housed some kind of gland.[9] Bolt (1974) conjectured that the well-developed nasal flange was probably for distribution of stresses throughout the skull and might be a hallmark of terrestrial dissorophoids.[18] He then suggested that there might be a gland related to salt excretion (the "glandula nasalis externa") that would produce the enlargement of the naris. Dilkes (1993) did not discount this hypothesis, but suggested alternatives, namely that the nasal flange and the expanded naris may have been for another physiological function, such as improving respiratory efficiency and water retention, an important attribute for a terrestrial amphibian to have.[24] However, all of these hypotheses remain speculative in the absence of much complexity of the hard tissues surrounding the naris and given the relatively vague paleoecological information available for trematopids (e.g., diet).


The placement of trematopids within Dissorophoidea has long been accepted, as has their close relationship to dissorophids, although Olsoniformes was not formalized until 2007.[32] Ecolsonia and Mordex have been more uncertainly placed in their history of study,[13][5] but both are now accepted as unequivocal trematopids. The two most recent phylogenetic analyses of Trematopidae are those by Berman et al. (2011) and Polley & Reisz (2011):

Topology of Berman et al. (2011):[27]

Topology of Polley & Reisz (2011):[28]



  1. ^ Williston, S. W. (1910). "Dissorophus Cope". The Journal of Geology. 18 (6): 526–536. Bibcode:1910JG.....18..526W. doi:10.1086/621768. ISSN 0022-1376. S2CID 224836685.
  2. ^ Watson, D. M. S. (1920-01-01). "The Structure, Evolution and Origin of the Amphibia. The "Orders' Rachitomi and Stereospondyli". Philosophical Transactions of the Royal Society B: Biological Sciences. 209 (360–371): 1–73. Bibcode:1920RSPTB.209....1W. doi:10.1098/rstb.1920.0001. ISSN 0962-8436.
  3. ^ Cope, E. D. (1882). "Third Contribution to the History of the Vertebrata of the Permian Formation of Texas". Proceedings of the American Philosophical Society. 20 (112): 447–461. ISSN 0003-049X. JSTOR 982692.
  4. ^ Fritsch, Antonin (1881). "Fauna der Gaskohle und der Kalksteine der Permformations Bohmens". Self-published. 1 (3).
  5. ^ a b c d Milner, Andrew R. (2018-11-27). "Two primitive trematopid amphibians (Temnospondyli, Dissorophoidea) from the Upper Carboniferous of the Czech Republic". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 109 (1–2): 201–223. doi:10.1017/s1755691018000725. ISSN 1755-6910. S2CID 133895158.
  6. ^ Williston, S. W. (1909). "New or Little-Known Permian Vertebrates: Trematops, New Genus". The Journal of Geology. 17 (7): 636–658. Bibcode:1909JG.....17..636W. doi:10.1086/621665. ISSN 0022-1376.
  7. ^ Moodie, Roy L. (1911). "Recent Contributions to a Knowledge of the Extinct Amphibia". The American Naturalist. 45 (534): 375–384. doi:10.1086/279219. ISSN 0003-0147.
  8. ^ Mehl, Maurice G. (1926). "Trematops Thomasi, a New Amphibian Species from the Permian of Oklahoma". The Journal of Geology. 34 (5): 466–474. Bibcode:1926JG.....34..466M. doi:10.1086/623333. ISSN 0022-1376. S2CID 140610416.
  9. ^ a b c Olson, Everett Claire (1941). "The Family Trematopsidae". The Journal of Geology. 49 (2): 149–176. Bibcode:1941JG.....49..149O. doi:10.1086/624952. ISSN 0022-1376. S2CID 129647184.
  10. ^ a b Dilkes, David W. (1990-06-21). "A new trematopsid amphibian (Temnospondyli: Dissorophoidea) from the Lower Permian of Texas". Journal of Vertebrate Paleontology. 10 (2): 222–243. doi:10.1080/02724634.1990.10011809. ISSN 0272-4634.
  11. ^ Olson, Everett C. (Everett Claire), 1910-1993. (1956). Fauna of the Vale and Choza : 12, a new Trematopsid amphibian from the Vale formation. Chicago Natural History Museum. OCLC 910497526.((cite book)): CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  12. ^ Milner, Andrew R. (1985). "On the identity of Trematopsis seltini (Amphibia: Temnospondyli) from the Lower Permian of Texas". Neues Jahrbuch für Geologie und Paläontologie, Monatshefte. 1985 (6): 357–367. doi:10.1127/njgpm/1985/1985/357.
  13. ^ a b Berman, David S.; Reisz, Robert R.; Eberth, David A. (1985). "Ecolsonia cutlerensis, an early Permian dissorophid amphibian from the Cutler Formation of north-central New Mexico". New Mexico Bureau of Mines and Minerals Research Circular. 191: 1–31.
  14. ^ Olson, Everett C. (Everett Claire), 1910-1993. (1970). Trematops stonei sp. nov. (Temnospondyli: amphibia) from the Washington Formation, Dunkard Group, Ohio. Cleveland Museum of Natural History. OCLC 36073554.((cite book)): CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  15. ^ Eaton, Theodore Hildreth, Verfasser (1973). A Pennsylvanian Dissorophid Amphibian from Kansas. OCLC 1068422466. ((cite book)): |last= has generic name (help)CS1 maint: multiple names: authors list (link)
  16. ^ Milner, Andrew R. (1985). "On the identity of the amphibian Hesperoherpeton garnettense from the Upper Pennsylvanian of Kansas". Palaeontology. 28 (4): 767–776.
  17. ^ Bolt, John R. (1974). A trematopsid skull from the Lower Permian, and analysis of some characters of the dissorophoid (Amphibia, Labyrinthodontia) otic notch / John R. Bolt. Chicago: Field Museum of Natural History. doi:10.5962/bhl.title.3432.
  18. ^ a b Bolt, John R. (1974). Osteology, function, and evolution of the Trematopsid (Amphibia: Labyrinthodontia) nasal region. Field Museum of Natural History. OCLC 914664.
  19. ^ Olson, Everett C. (1985). "A Larval Specimen of a Trematopsid (Amphibia: Temnospondyli)". Journal of Paleontology. 59 (5): 1173–1180. ISSN 0022-3360. JSTOR 1305010.
  20. ^ Dilkes, David W. (1991). "Reinterpretation of a larval dissorophoid amphibian from the Lower Permian of Texas". Canadian Journal of Earth Sciences. 28 (9): 1488–1492. Bibcode:1991CaJES..28.1488D. doi:10.1139/e91-130. ISSN 0008-4077.
  21. ^ a b c Schoch, Rainer R.; Milner, Andrew R. (2014). Sues, Hans-Dieter (ed.). Handbuch der Paläoherpetologie Part 3A2. Temnospondyli I. Stuttgart: Verlag Dr. Friedrich Pfeil. ISBN 978-3-931516-26-0. OCLC 580976.
  22. ^ Gee, Bryan M.; Reisz, Robert R. (2019-09-10). "The amphibamiform Nanobamus macrorhinus from the early Permian of Texas". Journal of Paleontology. 94 (2): 366–377. doi:10.1017/jpa.2019.72. ISSN 0022-3360. S2CID 203119272.
  23. ^ Berman, David S; Reisz, Robert R.; Eberth, David A. (1987-09-16). "A new genus and species of trematopid amphibian from the Late Pennsylvanian of north-central New Mexico". Journal of Vertebrate Paleontology. 7 (3): 252–269. doi:10.1080/02724634.1987.10011659. ISSN 0272-4634.
  24. ^ a b Dilkes, David W. (1993). "Biology and evolution of the nasal region in trematopid amphibians". Palaeontology. 36 (4): 839–853.
  25. ^ Sumida, Stuart S.; Berman, David S.; Martens, Thomas (1998). "A new trematopid amphibian from the Lower Permian of central Germany". Palaeontology. 41 (4): 605–629.
  26. ^ Berman, David S; Henrici, Amy C.; Brezinski, David K.; Kollar, Albert D. (2009). "A New Trematopid Amphibian (Temnospondyli: Dissorophoidea) from the Upper Pennsylvanian of Western Pennsylvania: Earliest Record of Terrestrial Vertebrates Responding to a Warmer, Drier Climate". Annals of Carnegie Museum. 78 (4): 289–318. doi:10.2992/007.078.0401. ISSN 0097-4463. S2CID 85974488.
  27. ^ a b Berman, David S; Henrici, Amy C.; Martens, Thomas; Sumida, Stuart S.; Anderson, Jason S. (2011). "Rotaryus gothae , a New Trematopid (Temnospondyli: Dissorophoidea) from the Lower Permian of Central Germany". Annals of Carnegie Museum. 80 (1): 49–65. doi:10.2992/007.080.0106. ISSN 0097-4463. S2CID 84780478.
  28. ^ a b Polley, Brendan P.; Reisz, Robert R. (2011-03-21). "A new Lower Permian trematopid (Temnospondyli: Dissorophoidea) from Richards Spur, Oklahoma". Zoological Journal of the Linnean Society. 161 (4): 789–815. doi:10.1111/j.1096-3642.2010.00668.x. hdl:1807/18982. ISSN 0024-4082.
  29. ^ Maddin, Hillary C.; Reisz, Robert R.; Anderson, Jason S. (2010-07-02). "Evolutionary development of the neurocranium in Dissorophoidea (Tetrapoda: Temnospondyli), an integrative approach: Dissorophoid neurocranial development". Evolution & Development. 12 (4): 393–403. doi:10.1111/j.1525-142X.2010.00426.x. PMID 20618435. S2CID 10724489.
  30. ^ Dilkes, David (2015-10-22). "Carpus and tarsus of Temnospondyli". Vertebrate Anatomy Morphology Palaeontology. 1: 51. doi:10.18435/B5MW2Q. ISSN 2292-1389.
  31. ^ Gee, Bryan M.; Bevitt, Joseph J.; Reisz, Robert R. (2019-03-12). "A Juvenile Specimen of the Trematopid Acheloma From Richards Spur, Oklahoma and Challenges of Trematopid Ontogeny". Frontiers in Earth Science. 7: 38. Bibcode:2019FrEaS...7...38G. doi:10.3389/feart.2019.00038. ISSN 2296-6463.
  32. ^ Anderson, Jason S.; Henrici, Amy C.; Sumida, Stuart S.; Martens, Thomas; Berman, David S. (2008-03-12). "Georgenthalia clavinasica, a new genus and species of dissorophoid temnospondyl from the Early Permian of Germany, and the relationships of the family Amphibamidae". Journal of Vertebrate Paleontology. 28 (1): 61–75. doi:10.1671/0272-4634(2008)28[61:gcanga];2. ISSN 0272-4634. S2CID 55943106.
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