# Gerrothorax

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Extinct genus of amphibians

Gerrothorax Temporal range: Ladinian–Rhaetian (Middle–Late Triassic) PreꞒ Ꞓ O S D C P T J K Pg N Fossil of Gerrothorax in the Naturmuseum Senckenberg Scientific classification Kingdom: Animalia Phylum: Chordata Clade: Tetrapoda Order: †Temnospondyli Suborder: †Stereospondyli Family: †Plagiosauridae Genus: †Gerrothorax Nilsson, 1934 Type species †Gerrothorax pulcherrimus Nilsson, 1934

***Gerrothorax*** ("wicker chest") is an extinct genus of [temnospondyl](/source/Temnospondyl) [amphibian](/source/Amphibian) from the [Triassic](/source/Triassic) period of [Greenland](/source/Greenland), [Germany](/source/Germany), [Poland](/source/Poland), [Sweden](/source/Sweden), and possibly [Thailand](/source/Thailand). It is known from a single species, *G. pulcherrimus*, although several other species such as *G. pustuloglomeratus* have been named in the past.

*Gerrothorax* was about 1 metre (3.3 ft) long, and had a remarkably flattened body. It probably hid under sand or mud on [river](/source/Stream_bed) and [lake bottoms](/source/Lake_beds), and in [brackish waters](/source/Brackish_water),[1] scanning for prey with its large, upward-facing eyes. *Gerrothorax* had an unusually shaped skull with angular protrusions on the sides. This looked vaguely similar to the skull of the earlier, unrelated, amphibian *[Diplocaulus](/source/Diplocaulus)*, but was not so developed.[2]

Some *Gerrothorax* fossils preserved [hypobranchials](/source/Hypobranchial) and [ceratobranchials](/source/Ceratobranchial) (bony [gill arches](/source/Branchial_arch)) near the neck. This shows that *Gerrothorax* was [pedomorphic](/source/Pedomorphosis), retaining its [larval](/source/Larva) [gills](/source/Gill) as an adult. When originally described in 1946, these bones were considered to correspond to feather-like [external gills](/source/External_gills) similar to those of modern-day neotenic [salamanders](/source/Salamander), such as the [mudpuppy](/source/Mudpuppy), the [axolotl](/source/Axolotl), and the [olm](/source/Olm).[3][2]

However, a 2011 paper found that it was more likely that plagiosaurids such as *Gerrothorax* had internal gills, like those of fish, rather than salamander-like external gills. The authors of that study noted that plagiosaurids and other ancient amphibians which retained gills as adults had grooves on their ceratobranchials. Grooved ceratobranchials are present in both modern and ancient fish, but unknown in modern amphibians. Therefore, they were indicative of internal gills. This would have also been advantageous for survival in large animals, as internal gills would have been protected by a large skin fold and were less likely to have been damaged by the environment.[4]

Life restoration of *Gerrothorax pulcherrimus*

A 2008 study showed that *Gerrothorax* lifted its head rather than dropping its jaw when catching prey, which has been compared to how a [toilet seat](/source/Toilet_seat) opens.[5] In 2011 the skull of *Gerrothorax* was scanned using [microtomography](/source/Microtomography), revealing that the [braincase](/source/Braincase) and [palatoquadrate](/source/Palatoquadrate) regions are highly ossified.[6] A 2013 study argued that *Gerrothorax* consumed prey using [suction feeding](/source/Suction_feeding). *Gerrothorax* had strong muscles capable of both raising the cranium and lowering the jaw rapidly. The robust internal gill apparatus would have expelled water through the gills during this motion, creating intense pressure in the throat that would suck in small prey items. The gill arches were also covered in small [denticles](https://en.wiktionary.org/wiki/denticle), prohibiting any prey from escaping once devoured. Although suction feeding is common in fish and modern larval amphibians, *Gerrothorax* differs from these animals by its lack of [cranial kinesis](/source/Cranial_kinesis), meaning that its cranial bones had fused [joints](/source/Joint) and could not flex against each other to create more negative space or to envelop prey.[7]

The fossil record of *Gerrothorax pulcherrimus* extends 35 million years from the [Ladinian](/source/Ladinian) stage of the [Middle Triassic](/source/Middle_Triassic) to the [Rhaetian](/source/Rhaetian) stage of the [Late Triassic](/source/Late_Triassic). Throughout this time span, specimens of the species show few [morphologic](/source/Morphology_(biology)) differences, making *G. pulcherrimus* an extreme example of [evolutionary stasis](/source/Punctuated_equilibrium). *G. pulcherrimus* may have remained unchanged for so long because it could tolerate a wide range of ecological conditions. Although it always needed to live in an aquatic habitat, *G. pulcherrimus* may have been able to live in a variety of different water bodies with a wide range of salinity.[8]

## References

1. **[^](#cite_ref-1)** [Vertebrate Skeletal Histology and Paleohistology](https://books.google.com/books?id=tJcwEAAAQBAJ&dq=Gerrothorax+brackish+environment&pg=PT730)

1. ^ [***a***](#cite_ref-EoDP_2-0) [***b***](#cite_ref-EoDP_2-1) Palmer, D., ed. (1999). *The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals*. London: Marshall Editions. p. 53. [ISBN](/source/ISBN_(identifier)) [978-1-84028-152-1](https://en.wikipedia.org/wiki/Special:BookSources/978-1-84028-152-1).

1. **[^](#cite_ref-3)** Nilsson, Tage (13 February 1946). ["A new find of Gerrothorax rhaeticus Nilsson, a plagiosaurid from the Rhaetic of Scania"](http://paleoarchive.com/literature/Nilsson1946-NewGerrothoraxRhaeticusScania.pdf) (PDF). *Lunds Universitets årsskrift*. **42** (10).

1. **[^](#cite_ref-:2_4-0)** Schoch, Rainer R.; Witzmann, Florian (2010-06-18). "Bystrow's Paradox – gills, fossils, and the fish-to-tetrapod transition". *Acta Zoologica*. **92** (3): 251–265. [doi](/source/Doi_(identifier)):[10.1111/j.1463-6395.2010.00456.x](https://doi.org/10.1111%2Fj.1463-6395.2010.00456.x).

1. **[^](#cite_ref-5)** Farish A. Jenkins, Jr.; Neil H. Shubin; Stephen M. Gatesy; Anne Warren (2008). "*Gerrothorax pulcherrimus* from the Upper Triassic Fleming Fjord Formation of East Greenland and a reassessment of head lifting in temnospondyl feeding". *[Journal of Vertebrate Paleontology](/source/Journal_of_Vertebrate_Paleontology)*. **28** (4): 935–950. [doi](/source/Doi_(identifier)):[10.1671/0272-4634-28.4.935](https://doi.org/10.1671%2F0272-4634-28.4.935). [S2CID](/source/S2CID_(identifier)) [86523094](https://api.semanticscholar.org/CorpusID:86523094).

1. **[^](#cite_ref-6)** F. Witzmann; R. R. Schoch; A. Hilger; N. Kardjilov (2011). ["Braincase, palatoquadrate and ear region of the plagiosaurid *Gerrothorax pulcherrimus* from the Middle Triassic of Germany"](https://doi.org/10.1111%2Fj.1475-4983.2011.01116.x). *[Palaeontology](/source/Palaeontology_(journal))*. **55** (1): 35–50. [doi](/source/Doi_(identifier)):[10.1111/j.1475-4983.2011.01116.x](https://doi.org/10.1111%2Fj.1475-4983.2011.01116.x).

1. **[^](#cite_ref-7)** Witzmann, Florian; Schoch, Rainer R. (27 December 2012). "Reconstruction of cranial and hyobranchial muscles in the triassic temnospondyl *Gerrothorax* provides evidence for akinetic suction feeding". *Journal of Morphology*. **274** (5): 525–542. [doi](/source/Doi_(identifier)):[10.1002/jmor.20113](https://doi.org/10.1002%2Fjmor.20113). [ISSN](/source/ISSN_(identifier)) [0362-2525](https://search.worldcat.org/issn/0362-2525). [PMID](/source/PMID_(identifier)) [23280767](https://pubmed.ncbi.nlm.nih.gov/23280767). [S2CID](/source/S2CID_(identifier)) [25217352](https://api.semanticscholar.org/CorpusID:25217352).

1. **[^](#cite_ref-SW11_8-0)** R. R. Schoch; F. Witzmann (2011). "Cranial morphology of the plagiosaurid *Gerrothorax pulcherrimus* as an extreme example of evolutionary stasis". *[Lethaia](/source/Lethaia)*. **45** (3): 371–385. [doi](/source/Doi_(identifier)):[10.1111/j.1502-3931.2011.00290.x](https://doi.org/10.1111%2Fj.1502-3931.2011.00290.x).

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v t e Stereospondyli Kingdom: Animalia Phylum: Chordata Clade: Tetrapodomorpha Order: Temnospondyli Tetrapodomorpha see Tetrapodomorpha Temnospondyli see Temnospondyli Stereospondyli see below↓ Stereospondyli Stereospondyli Arachana Capulomala Peltobatrachus Lapillopsidae Lapillopsis Manubrantlia Rhigerpeton Rotaurisaurus Rhinesuchidae Australerpeton? Broomistega Laccosaurus Parapytanga? Rastosuchus Rhineceps Rhinesuchoides Rhinesuchus Uranocentrodon Lydekkerinidae Chomatobatrachus Cryobatrachus Deltacephalus Eolydekkerina Indobenthosuchus Luzocephalus? Lydekkerina Capitosauria Antarctosuchus Bukobaja Calmasuchus Capitosaurus Cherninia Cyclotosaurus Edingerella Eocyclotosaurus Eryosuchus Heptasaurus Huangfuchuansuchus Jammerbergia Kestrosaurus Kupferzellia Mastodonsaurus Meyerosuchus Odenwaldia Paracyclotosaurus Parotosuchus Quasicyclotosaurus Procyclotosaurus Promastodonsaurus Rhadalognathus Samarabatrachus Sassenisaurus Sclerothorax Selenocara Stanocephalosaurus Stenotosaurus Subcyclotosaurus Tatrasuchus Vladlenosaurus Volgasaurus Volgasuchus Warrenisuchus Watsonisuchus Wellesaurus Wetlugasaurus Xenotosuchus Yuanansuchus Trematosauria see below↓ Trematosauria Trematosauria Almasaurus Bothriceps Callistomordax Chinlestegophis Keratobrachyops Laidleria Latiscopus Qantas Rileymillerus Syrtosuchus Uruyiella Benthosuchidae Benthosuchus Kwatisuchus Trematosauridae Angusaurus Aphaneramma Cosgriffius Erythrobatrachus Gonioglyptus Hyperokynodon Icanosaurus Indolyrocephalus Inflectosaurus Lyrocephaliscus Microposaurus Panchetosaurus Platystega Prothoosuchus Stoschiosaurus Tertrema Tertremoides Thoosuchus Tirraturhinus Trematolestes Trematosuchoides Trematosaurus Trematosuchus Trematotegmen Wantzosaurus Metoposauridae Anaschisma Apachesaurus Arganasaurus Buettnererpeton Dutuitosaurus Metoposaurus Panthasaurus Rhytidosteidae Boreopelta Mahavisaurus Nanolania Peltostega Pneumatostega Rhytidosteus Sangaia Trucheosaurus Derwentiinae Arcadia Acerastia Deltasaurus Derwentia Indobrachyops Rewana Chigutisauridae Arenaerpeton Chigutisaurus Compsocerops Koolasuchus Pelorocephalus Siderops Brachyopidae Banksiops Bathignathus Batrachosaurus Batrachosuchoides Batrachosuchus Blinasaurus Brachyops Gobiops Hadrokkosaurus Notobrachyops Platycepsion Sinobrachyops Vanastega Vigilius Xenobrachyops Plagiosauridae Gerrothorax Megalophthalma Plagiobatrachus Plagiorophus Plagiosaurus Plagioscutum Plagiosternum Plagiosuchus See also: Trematosauroidea Metoposauroidea Rhytidosteoidea Brachyopomorpha Brachyopoidea Plagiosauroidea Category

Taxon identifiers Gerrothorax Wikidata: Q134415 Wikispecies: Gerrothorax BioLib: 450825 EoL: 53656539 GBIF: 4815752 IRMNG: 1106911 Open Tree of Life: 4948439 Paleobiology Database: 37170 Taxonomicon: 47167

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Adapted from the Wikipedia article [Gerrothorax](https://en.wikipedia.org/wiki/Gerrothorax) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gerrothorax?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.