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Micropholis (amphibian)

October 22, 2023

Micropholis (Greek 'mikros' = small and 'pholis' = scale) is an extinct genus of dissorophoid temnospondyl. Fossils have been found from the Lystrosaurus Assemblage Zone of the Karoo Basin in South Africa and are dated to the Induan (Early Triassic). Fossils have also been found from the lower Fremouw of Antarctica.[1]Micropholis is the only post-Permian dissorophoid and the only dissorophoid in what is presently the southern hemisphere and what would have been termed Gondwana during the amalgamation of Pangea.

Micropholis
Temporal range: Early Triassic
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: †Temnospondyli
Family: †Micropholidae
Genus: †Micropholis
Huxley, 1859
Species
  • M. stowi Huxley, 1859 (type)
Synonyms
  • Petrophryne Owen, 1876

History of study Edit

 
Skull of M. stowi in the Field Museum of Natural History.

Micropholis was one of the first dissorophoids to be named by English paleontologist Thomas Huxley in 1859 based on a partial skull.[2] Micropholis stowii (properly Micropholis stowi), the type species, is named for George William Stow, the South African geologist and ethnologist who discovered the specimen and who proposed that it represented some extinct amphibian. English paleontologist Richard Owen later named a new genus and species, Petrophryne granulata, for a better-known skull, also from the Karoo Basin, that he suggested might be the same animal as M. stowi;[3] this synonymy was eventually accepted by other workers. Additional description was furnished by German paleontologists Ferdinand Broili and Joachim Schröder in 1937.[4] The taxon was most recently revised by German paleontologist Jürgen Boy in 1985[5] and again in 2005 by German paleontologist Rainer Schoch and South African paleontologist Bruce Rubidge.[6] Micropholis has been repeatedly incorporated in phylogenetic analyses of temnospondyls and dissorophoids. In 2015, American paleontologist Julia McHugh published a description of histological patterns in Micropholis[7].

Description Edit

Practically the entire skeleton of Micropholis is now known. Many specimens have been found, a number of which are on blocks preserving partial to complete skeletons of multiple individuals in close association,[4] and two distinct morphotypes are evident, differing in skull width and palatal dentition.[5][6]

The "slender-headed" morph is defined by corresponding narrowing of many features and cranial elements, differences in dentition on the vomer, and possibly by smaller and more numerous maxillary teeth when compared with the "broad-headed" morph. Additionally, a wide size range of individuals are known, ranging from skull lengths around 20 mm to over 40 mm. There remains some uncertainty about whether the slender-headed morph is an advanced ontogenetic stage, as the largest individuals all exhibit this skull morphology. Schoch & Milner (2014)[full citation needed] identified 10 features in the diagnosis of Micropholis:

(1) dermal ornament, with irregularly spaced pustules;
(2) accessory fangs on the vomer;
(3) unpaired anterior palatal fenestra (sometimes 'fontanelle');
(4) palatine and ectopterygoid reduces to struts along medial maxillary margin;
(5) short basipterygoid ramus of pterygoid;
(6) basal plate with prominent posterolateral horns;
(7) hyobranchial skeleton well ossified;
(8) short tail;
(9) elongate skull table (plesiomorphy); and
(10) postparietal much longer than tabular (plesiomorphy).

Phylogenetic relationships Edit

When it was first described, Micropholis was recognized as a 'labyrinthodont,' an outdated term used to refer to extinct 'amphibians' in a broad sense. However, Huxley remarked that it did not show close affinities with any of the known Triassic labyrinthodonts of the time. Its uncertain affinities continued to plague paleontologists who remarked that "no types really closely allied to it have been found".[8] As a result, it was placed within its own family, Micropholidae,[9] and sometimes within its own superfamily, Micropholoidea.[10] Although it was suggested in the 1930s that Micropholis might be allied with dissorophoids by comparison with the dissorophid Broiliellus,[11] this idea was not widely adopted[10] until the 1960s.[12] Subsequent discovery of amphibamiforms, either referred to monotaxic families such as Doleserpetontidae[13] or to Dissorophidae, has further strengthened the placement of Micropholis among dissorophoids, which has since been maintained by computer-assisted phylogenetic analyses.[14] Micropholis now belongs to the recently resurrected family Micropholidae,[15] which is included in what was historically termed Amphibamidae (now Amphibamiformes). However, its placement has long been perplexing because it retains numerous plesiomorphies and is usually recovered as one of the earlier diverging amphibamiforms despite being tens of millions of years younger than all other dissorophoids.

Below is a phylogeny from Schoch (2018)[15] showing the position of Micropholis.

References Edit

  1. ^ Gee, Bryan M.; Sidor, Christian A. (2021-05-21). "First record of the amphibamiform Micropholis stowi from the lower Fremouw Formation (Lower Triassic) of Antarctica". Journal of Vertebrate Paleontology. 41: e1904251. doi:10.1080/02724634.2021.1904251. ISSN 0272-4634.
  2. ^ Huxley, T. H. (1859-01-01). "On some Amphibian and Reptilian Remains from South Africa and Australia". Quarterly Journal of the Geological Society. 15 (1–2): 642–658. doi:10.1144/gsl.jgs.1859.015.01-02.71. ISSN 0370-291X. S2CID 129159449.
  3. ^ Owen, Richard (1876). "On Petrophryne granulata Ow., a labyrinthodont reptile from the Trias of South Africa, with special comparison of the skull with that of Rhinosaurus jasikovii". Bulletin Société Sciences Naturelles Moscou. 50: 147–153.
  4. ^ a b Broili, Ferdinand; Schröder, Joachim (1937). "Beobachtungen an Wirbeltieren der Karrooformation. XXV. Uber Micropholis Huxley". Sitzungsberichte der Bayrischen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Abteilung. 1937: 19–38.
  5. ^ a b Boy, Jürgen A. (1985-01-29). "Micropholis the last surviving dissorophoid (Amphibia, Temnospondyli; Lower Triassic)". Neues Jahrbuch für Geologie und Paläontologie - Monatshefte. 1985 (1): 29–45. doi:10.1127/njgpm/1985/1985/29. ISSN 0028-3630.
  6. ^ a b Schoch, Rainer R.; Rubidge, Bruce S. (2005-09-30). "The amphibamid Micropholis from the Lystrosaurus Assemblage Zone of South africa". Journal of Vertebrate Paleontology. 25 (3): 502–522. doi:10.1671/0272-4634(2005)025[0502:TAMFTL]2.0.CO;2. ISSN 0272-4634. S2CID 85979872.
  7. ^ Mchugh, Julia B. (2015-01-02). "Paleohistology of Micropholis stowi (Dissorophoidea) and Lydekkerina huxleyi (Lydekkerinidae) humeri from the Karoo Basin of South Africa, and implications for bone microstructure evolution in temnospondyl amphibians". Journal of Vertebrate Paleontology. 35 (1): e902845. doi:10.1080/02724634.2014.902845. ISSN 0272-4634. S2CID 86106336.
  8. ^ Watson, D.M.S. (August 1913). "II. — Micropholis stowi, Huxley, a temnospondylous amphibian from South Africa". Geological Magazine. 10 (8): 340–346. Bibcode:1913GeoM...10..340W. doi:10.1017/S0016756800127001. ISSN 1469-5081.
  9. ^ "I. The structure, evolution and origin of the amphibia. - The "orders' rachitomi and stereospondyli". Philosophical Transactions of the Royal Society of London. Series B, Containing Papers of a Biological Character. 209 (360–371): 1–73. January 1920. doi:10.1098/rstb.1920.0001. ISSN 0264-3960.
  10. ^ a b Romer, Alfred Sherwood (1947). Review of the Labyrinthodontia. Museum of Comparative Zoology. OCLC 12898383.
  11. ^ Säve-Söderbergh, G. (1935). "[Presumed Danish title not cited]" [On the dermal bones of the head in labyrinthodont stegocephalians and primitive reptilia, with special reference to eo-triassic stegocephalians from east Greenland]. Meddelelser om Grønland [Communications on Greenland] (in Danish). Copenhagen, DK. 98 (3): 1–211, plates 1–15;[full citation needed]
    [reviewer not cited] (April 1935). "Reviews – Stegocephalians and primitive reptiles". Geological Magazine. 72 (4): 190–191. Bibcode:1935GeoM...72..190.. doi:10.1017/s001675680009261x. ISSN 0016-7568;
    Double-citation needs to be checked: The first ref., to Meddelelser om Grønland is embedded inside the second citation, to Geological Magazine, where the first article is reviewed. It is displayed that way in the original text in the front-page of the review article in Geological Magazine.
  12. ^ Romer, Alfred Sherwood. Vertebrate Paleontology (Third ed.). Chicago, IL. ISBN 0-226-72488-3. OCLC 174202.
  13. ^ Bolt, J.R. (1969-11-14). "Lissamphibian origins: Possible protolissamphibian from the Lower Permian of Oklahoma". Science. 166 (3907): 888–891. Bibcode:1969Sci...166..888B. doi:10.1126/science.166.3907.888. ISSN 0036-8075. PMID 17815754. S2CID 10813454.
  14. ^ Boy, Jürgen A. (1972). Die Branchiosaurier <Amphibia> des saarpfälzischen Rotliegenden <Perm, SW-Deutschland>. OCLC 163720370.
  15. ^ a b Schoch, Rainer R. (2018-11-05). "The putative lissamphibian stem-group: Phylogeny and evolution of the dissorophoid temnospondyls". Journal of Paleontology. 93 (1): 137–156. doi:10.1017/jpa.2018.67. ISSN 0022-3360.

External links Edit

October 22, 2023
micropholis, amphibian, micropholis, greek, mikros, small, pholis, scale, extinct, genus, dissorophoid, temnospondyl, fossils, have, been, found, from, lystrosaurus, assemblage, zone, karoo, basin, south, africa, dated, induan, early, triassic, fossils, have, . Micropholis Greek mikros small and pholis scale is an extinct genus of dissorophoid temnospondyl Fossils have been found from the Lystrosaurus Assemblage Zone of the Karoo Basin in South Africa and are dated to the Induan Early Triassic Fossils have also been found from the lower Fremouw of Antarctica 1 Micropholis is the only post Permian dissorophoid and the only dissorophoid in what is presently the southern hemisphere and what would have been termed Gondwana during the amalgamation of Pangea MicropholisTemporal range Early TriassicScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass AmphibiaOrder TemnospondyliFamily MicropholidaeGenus MicropholisHuxley 1859SpeciesM stowi Huxley 1859 type SynonymsPetrophryne Owen 1876 Contents 1 History of study 2 Description 3 Phylogenetic relationships 4 References 5 External linksHistory of study Edit nbsp Skull of M stowi in the Field Museum of Natural History Micropholis was one of the first dissorophoids to be named by English paleontologist Thomas Huxley in 1859 based on a partial skull 2 Micropholis stowii properly Micropholis stowi the type species is named for George William Stow the South African geologist and ethnologist who discovered the specimen and who proposed that it represented some extinct amphibian English paleontologist Richard Owen later named a new genus and species Petrophryne granulata for a better known skull also from the Karoo Basin that he suggested might be the same animal as M stowi 3 this synonymy was eventually accepted by other workers Additional description was furnished by German paleontologists Ferdinand Broili and Joachim Schroder in 1937 4 The taxon was most recently revised by German paleontologist Jurgen Boy in 1985 5 and again in 2005 by German paleontologist Rainer Schoch and South African paleontologist Bruce Rubidge 6 Micropholis has been repeatedly incorporated in phylogenetic analyses of temnospondyls and dissorophoids In 2015 American paleontologist Julia McHugh published a description of histological patterns in Micropholis 7 Description EditPractically the entire skeleton of Micropholis is now known Many specimens have been found a number of which are on blocks preserving partial to complete skeletons of multiple individuals in close association 4 and two distinct morphotypes are evident differing in skull width and palatal dentition 5 6 The slender headed morph is defined by corresponding narrowing of many features and cranial elements differences in dentition on the vomer and possibly by smaller and more numerous maxillary teeth when compared with the broad headed morph Additionally a wide size range of individuals are known ranging from skull lengths around 20 mm to over 40 mm There remains some uncertainty about whether the slender headed morph is an advanced ontogenetic stage as the largest individuals all exhibit this skull morphology Schoch amp Milner 2014 full citation needed identified 10 features in the diagnosis of Micropholis 1 dermal ornament with irregularly spaced pustules 2 accessory fangs on the vomer 3 unpaired anterior palatal fenestra sometimes fontanelle 4 palatine and ectopterygoid reduces to struts along medial maxillary margin 5 short basipterygoid ramus of pterygoid 6 basal plate with prominent posterolateral horns 7 hyobranchial skeleton well ossified 8 short tail 9 elongate skull table plesiomorphy and 10 postparietal much longer than tabular plesiomorphy Phylogenetic relationships EditWhen it was first described Micropholis was recognized as a labyrinthodont an outdated term used to refer to extinct amphibians in a broad sense However Huxley remarked that it did not show close affinities with any of the known Triassic labyrinthodonts of the time Its uncertain affinities continued to plague paleontologists who remarked that no types really closely allied to it have been found 8 As a result it was placed within its own family Micropholidae 9 and sometimes within its own superfamily Micropholoidea 10 Although it was suggested in the 1930s that Micropholis might be allied with dissorophoids by comparison with the dissorophid Broiliellus 11 this idea was not widely adopted 10 until the 1960s 12 Subsequent discovery of amphibamiforms either referred to monotaxic families such as Doleserpetontidae 13 or to Dissorophidae has further strengthened the placement of Micropholis among dissorophoids which has since been maintained by computer assisted phylogenetic analyses 14 Micropholis now belongs to the recently resurrected family Micropholidae 15 which is included in what was historically termed Amphibamidae now Amphibamiformes However its placement has long been perplexing because it retains numerous plesiomorphies and is usually recovered as one of the earlier diverging amphibamiforms despite being tens of millions of years younger than all other dissorophoids Below is a phylogeny from Schoch 2018 15 showing the position of Micropholis OlsoniformesAmphibamiformes EoscopusPlatyrhinopsMicropholidae TersomiusPasawioopsMicropholisAmphibamidae DoleserpetonAmphibamusGerobatrachusGeorgenthaliaLissamphibia EocaeciliaKaraurusTriadobatrachusBranchiosauridae BranchiosaurusApateonLeptorophusSchoenfelderpetonReferences Edit Gee Bryan M Sidor Christian A 2021 05 21 First record of the amphibamiform Micropholis stowi from the lower Fremouw Formation Lower Triassic of Antarctica Journal of Vertebrate Paleontology 41 e1904251 doi 10 1080 02724634 2021 1904251 ISSN 0272 4634 Huxley T H 1859 01 01 On some Amphibian and Reptilian Remains from South Africa and Australia Quarterly Journal of the Geological Society 15 1 2 642 658 doi 10 1144 gsl jgs 1859 015 01 02 71 ISSN 0370 291X S2CID 129159449 Owen Richard 1876 On Petrophryne granulata Ow a labyrinthodont reptile from the Trias of South Africa with special comparison of the skull with that of Rhinosaurus jasikovii Bulletin Societe Sciences Naturelles Moscou 50 147 153 a b Broili Ferdinand Schroder Joachim 1937 Beobachtungen an Wirbeltieren der Karrooformation XXV Uber Micropholis Huxley Sitzungsberichte der Bayrischen Akademie der Wissenschaften Mathematisch Naturwissenschaftliche Abteilung 1937 19 38 a b Boy Jurgen A 1985 01 29 Micropholis the last surviving dissorophoid Amphibia Temnospondyli Lower Triassic Neues Jahrbuch fur Geologie und Palaontologie Monatshefte 1985 1 29 45 doi 10 1127 njgpm 1985 1985 29 ISSN 0028 3630 a b Schoch Rainer R Rubidge Bruce S 2005 09 30 The amphibamid Micropholis from the Lystrosaurus Assemblage Zone of South africa Journal of Vertebrate Paleontology 25 3 502 522 doi 10 1671 0272 4634 2005 025 0502 TAMFTL 2 0 CO 2 ISSN 0272 4634 S2CID 85979872 Mchugh Julia B 2015 01 02 Paleohistology of Micropholis stowi Dissorophoidea and Lydekkerina huxleyi Lydekkerinidae humeri from the Karoo Basin of South Africa and implications for bone microstructure evolution in temnospondyl amphibians Journal of Vertebrate Paleontology 35 1 e902845 doi 10 1080 02724634 2014 902845 ISSN 0272 4634 S2CID 86106336 Watson D M S August 1913 II Micropholis stowi Huxley a temnospondylous amphibian from South Africa Geological Magazine 10 8 340 346 Bibcode 1913GeoM 10 340W doi 10 1017 S0016756800127001 ISSN 1469 5081 I The structure evolution and origin of the amphibia The orders rachitomi and stereospondyli Philosophical Transactions of the Royal Society of London Series B Containing Papers of a Biological Character 209 360 371 1 73 January 1920 doi 10 1098 rstb 1920 0001 ISSN 0264 3960 a b Romer Alfred Sherwood 1947 Review of the Labyrinthodontia Museum of Comparative Zoology OCLC 12898383 Save Soderbergh G 1935 Presumed Danish title not cited On the dermal bones of the head in labyrinthodont stegocephalians and primitive reptilia with special reference to eo triassic stegocephalians from east Greenland Meddelelser om Gronland Communications on Greenland in Danish Copenhagen DK 98 3 1 211 plates 1 15 full citation needed reviewer not cited April 1935 Reviews Stegocephalians and primitive reptiles Geological Magazine 72 4 190 191 Bibcode 1935GeoM 72 190 doi 10 1017 s001675680009261x ISSN 0016 7568 Double citation needs to be checked The first ref to Meddelelser om Gronland is embedded inside the second citation to Geological Magazine where the first article is reviewed It is displayed that way in the original text in the front page of the review article in Geological Magazine Romer Alfred Sherwood Vertebrate Paleontology Third ed Chicago IL ISBN 0 226 72488 3 OCLC 174202 Bolt J R 1969 11 14 Lissamphibian origins Possible protolissamphibian from the Lower Permian of Oklahoma Science 166 3907 888 891 Bibcode 1969Sci 166 888B doi 10 1126 science 166 3907 888 ISSN 0036 8075 PMID 17815754 S2CID 10813454 Boy Jurgen A 1972 Die Branchiosaurier lt Amphibia gt des saarpfalzischen Rotliegenden lt Perm SW Deutschland gt OCLC 163720370 a b Schoch Rainer R 2018 11 05 The putative lissamphibian stem group Phylogeny and evolution of the dissorophoid temnospondyls Journal of Paleontology 93 1 137 156 doi 10 1017 jpa 2018 67 ISSN 0022 3360 External links EditMicropholis in the Paleobiology Database nbsp Paleontology portal Retrieved from https en wikipedia org w index php title Micropholis amphibian amp oldid 1139844238, wikipedia, wiki, book, books, library,

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