# Mastodonsauridae

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Extinct family of temnospondyls

Mastodonsaurids Temporal range: Triassic 250.0–199.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N Skull of Heptasaurus cappelensis Scientific classification Kingdom: Animalia Phylum: Chordata Clade: Tetrapoda Order: †Temnospondyli Suborder: †Stereospondyli Clade: †Capitosauria Superfamily: †Mastodonsauroidea Family: †Mastodonsauridae Lydekker, 1885 Genera †Abiadisaurus †Bukobaja †Capitosaurus †Cherninia †Cyclotosaurus †Eryosuchus †Heptasaurus †Jammerbergia †Kestrosaurus †Kupferzellia †Mastodonsaurus †Paracyclotosaurus †Parotosuchus †Promastodonsaurus †Rhadalognathus †Sassenisaurus †Stanocephalosaurus †Subcyclotosaurus †Volgasaurus †Volgasuchus †Wetlugasaurus †Xenotosuchus Synonyms Capitosauridae Watson, 1919

**Mastodonsauridae** is a family of [capitosauroid](/source/Capitosauroidea) [temnospondyls](/source/Temnospondyl). [Fossils](/source/Fossil) belonging to this family have been found in [North America](/source/North_America), [Greenland](/source/Greenland), [Europe](/source/Europe), [Asia](/source/Asia), and [Australia](/source/Australia). The family **Capitosauridae** is [synonymous](/source/Synonym_(taxonomy)) with Mastodonsauridae.

## Description

### Size

*[Paracyclotosaurus](/source/Paracyclotosaurus) crookshanki* compared to a human

Mastodonsaurids were generally large amphibians, with some length estimates ranging from 3 to 6 meters. Some genera, like *[Mastodonsaurus](/source/Mastodonsaurus)*[1] and *[Cyclotosaurus](/source/Cyclotosaurus)*[2] were specially large, reaching at least 4 meters or more. Other genera like *[Parotosuchus](/source/Parotosuchus)* and *[Paracyclotosaurus](/source/Paracyclotosaurus)*[3] only reached 2 meters or more in length, but it's still large compared to most modern-day amphibians.

### Distinguishing features

Some mastodonsaurids including *Parotosuchus* were covered in a scaly skin, unlike the smooth skin of modern-day [amphibians](/source/Amphibian), and probably moved with an [eel](/source/Eel)-like motion in the water.[4] Another peculiar mastodonsaurid is *Sclerothorax*, with unusual features including its elongated neural spines. The neural spines are tallest at the front of the spine. *Sclerothorax* also has a very large [pectoral girdle](/source/Pectoral_girdle); the [interclavicle](/source/Interclavicle) bone is longer than the skull, meaning that *Sclerothorax* has the proportionally largest interclavicle of any temnospondyl. The body of *Sclerothorax* is covered by small scale-like bony ossicles that would have been embedded in the [dermis](/source/Dermis) in life. The skull of *Sclerothorax* is short, wide, and roughly rectangular in shape. The snout is wider than the cheek region. The bones along the midline of the [skull roof](/source/Skull_roof) are also very wide relative to those of other temnospondyls.[5]

### Skull structures

Skull cast of *[Stanocephalosaurus](/source/Stanocephalosaurus)*

There is a lot of known information about the skulls of mastodonsaurids, for example, *[Stanocephalosaurus](/source/Stanocephalosaurus)*, one of the most well-known mastodonsaurids, has a lot of data about its skull. The skull of *Stanocephalosaurus* has key features characteristic to other temnospondyls, with the most apparent being the flattened shape of its [skull roof](/source/Skull_roof). The dorsal as well as ventral surfaces of the skull of *Stanocephalosaurus* have well ornamented honeycombed patterns throughout. Palatal views of skulls in this genus show narrow interpalatal vacuities, as well as paired palatal [tusks](/source/Tusk) alternately functioning on the [vomer](/source/Vomer) and [palatine](/source/Palatine_bone), with the vomerine tusks directed backwards. This animal shows an increased expansion of the [pterygoids](/source/Pterygoid_bone) and palatines, as well as narrow posterior [nostrils](/source/Nostril). The vomer also bears two vomerine rows: a transversal denticle row and a longitudinal denticle row that runs along the inner margin of the choana. The palatines and ectopterygoids are broader than in other temnospondyls, which is somewhat common within mastodonsaurids. *Stanocephalosaurus* also has a long, triangular skull which is much longer than broad, and has an elongated preorbital region continuously narrowing anteriorly to an obtuse rounded snout. This type of skull is very similar to that of *Mastodonsaurus*, which is also triangular in shape.[6] The *Stanocephalosaurus* has at least 100 straight and conical teeth on the [premaxilla](/source/Premaxilla) and [maxilla](/source/Maxilla) combined, gradually increasing in size towards the front.[7]

While there is a lot of known information about *Stanocephalosaurus*, some of the skull regions which were previously inaccessible or too poorly preserved on *Stanocephalosaurus* have been observed with X-ray [micro-CT](/source/X-ray_microtomography) scans, including the otic capsule, delta groove of the exoccipital, as well as parts of the arterial and nervous system. Air pockets around the [stapes](/source/Stapes) of *Stanocephalosaurus* have been hypothesized to act as resonance chambers, meaning that the spoon-shaped inner ear bone could be related to underwater hearing. This trait is possibly associated with early [tetrapod](/source/Tetrapod) evolution, which probably also appears on other members of this family and can act as a link to [anuran](/source/Frog) tympanum evolution.[8]

The narrow head and elongated snout of *Stanocephalosaurus* suggests that stress levels during biting are slightly higher than temnospondyls with a wider and shorter skull. Its skull also has an elongated preorbital region compared to other mastodonsaurids. [9]

The [vertebrae](/source/Vertebra) of *Stanocephalosaurus* are rhachitomous, with a neural arch and a bipartite centrum that is divided into a large, unpaired wedge-shaped intercentrum and smaller paired pleurocentra. In anterior and posterior views, the intercentrum is a dorsally half-ring, surrounding the persistent [notochord](/source/Notochord) from ventral and lateral sides. Lateral and ventral surfaces of the intercentrum are smooth, suggesting a continuation of [cartilage](/source/Cartilage) due to the unfinished medial surface. The posterodorsal margin of the intercentrum also shows a parapophysis for articulation with the capitulum of the ribs.[10]

Skeleton of *Mastodonsaurus*, with a close up view of the skull

Another well-known mastodonsaurid in terms of fossil knowledge is *Mastodonsaurus*, notably from numerous skull specimens found in Germany. The large, oval eye sockets are midway along the skull. The jaws are lined with conical teeth, two large [tusks](/source/Tusk) project up from the end of the lower jaw, fitting through openings on the [palate](/source/Palate) and emerging out from the top of the skull when the jaw is closed. Based on recent research, the body of *Mastodonsaurus* was more crocodile-like in shape than in earlier reconstructions, with a longer trunk section and a longer tail. The greatly reduced limb bones have joints that are poorly developed.[1][11]

Skeletal reconstruction of *Paracyclotosaurus* (NHMUK PV R 6000)

*Paracyclotosaurus* is yet again, another well-known mastodonsaurid, and just like most genera of the family, it had various species. This mastodonsaurid has at least three species, including its [type species](/source/Type_species), which is *P. davidi*, along with two other: *P. crookshanki* and *P. morganorum*. The completeness of the skeleton of this animal led to an accurate description. The small distortion of the head can be overlooked, and the complete preservation of the skull and jaws makes its shape certain at a length of 60 cm. The right corner of the head is essentially undistorted and shows that the skull at its point of greatest depth is almost exactly as high as the lower jaw. The lower jaw also has its symphysis the same height as the skull above it. Therefore, at its point of greatest height, the head was essentially of oval section, 22 cm high and 44 cm wide. The nostril, orbit and tympanic membrane are all directed upward, but whether the eye could be projected upward above the head to give a horizontal view similar to a [frog](/source/Frog), is difficult to determine.[3]

With very similar features to *Cyclotosaurus*, *[Subcyclotosaurus](/source/Subcyclotosaurus)* is another good example of mastodonsaurid. Its skull is characterized by the small tabular without any trace of a "horn", but with a round lappet that approaches the squamosal flange lateral to the tympanic membrane, failing to meet it by about its own width. The occiput between the otic notches is proportionately wide, a reflection of the small size of the skull. The skull is otherwise of normal mastodonsaurid structure, being specifically more similar to *Parotosuchus* than to any other genera of this family. The skull also has a small internasal vacuity between the dorsal processes of the premaxillae and lateral lines are often shown as continuous grooves with well-defined borders. A deep groove on the [maxilla](/source/Maxilla) begins immediately behind and lateral to the nostril and passes straight back to the lachrymal, on which bone it turns outward and forward and ends abruptly. Another groove appears to begin on the maxilla, immediately lateral to that described above. It passes back just above the insertion of the teeth for the full length of the bone. The supraorbital groove begins abruptly on the dorsal surface of the premaxilla, immediately passes on to the nasal, and extends back on that bone close to its suture with the lachrymal. It then comes on to the prefrontal, passing on to the frontal where that bone enters the orbital border. Then as a well-defined groove it surrounds the hinder part of the orbit, turns vertically on to the jugal, and then backward to cross the point where jugal, quadratojugal and squamosal meet, continuing over the squamosal to pass back on to the body.

*[Xenotosuchus](/source/Xenotosuchus)* skull, showing the full complement of [tetrapod](/source/Tetrapod) [skull roof](/source/Skull_roof) bones

*[Xenotosuchus](/source/Xenotosuchus)* is a member of this which is not very well known, and only a few fragments have been discovered from this animal. This genus was originally a species of *Parotosuchus*. Like many mastodontosaurids, it was a large animal with a large head. Its [amphibian](/source/Amphibian) life history meant that the distinct shape of the [skull roof](/source/Skull_roof) would change from a generalized [tadpole](/source/Tadpole)-like skull to the distinct adult shape.[12] The head bones are covered in large pits and grooves, indicating extensive dermal armour on the head. Both the upper and lower jaw had [tusks](/source/Tusk), those of the upper jaw being situated on a second row of teeth on the [vomer](/source/Vomer) and [palatine bone](/source/Palatine_bone). Contrary to related forms like *Mastodonsaurus* and *Stanocephalosaurus*, the tusks of the lower jaw were of moderate size and did not penetrate the [premaxilla](/source/Premaxilla).[13]

Like the mentioned *Xenotosuchus*, the genus *[Wetlugasaurus](/source/Wetlugasaurus)* is also one of the smaller and less known mastodonsaurids.[14] It had a [skull](/source/Skull) that measured around 22 centimetres (8.7 in), and reached a total length of at least 1 metre (3 ft 3 in), and although it is pretty large compared to modern-day amphibians, *Wetlugasaurus* is still very small compared to most of the other mastodonsaurids.

## Paleobiology

Mastodonsaurids were [piscivorous](/source/Piscivorous), mainly preying on small and mid-sized fish, although they also ate land-living animals, such as small [archosaurs](/source/Archosaurs). Some evidences, including the fossils of some smaller temnospondyls bear tooth marks made by mastodonsaurid-like animals.

It is very likely that mastodonsaurids caught their food like the living giant salamander, waiting until the prey came near, then quickly opening their enormous mouths and swallowing them prey whole. The most probable food would be small fishes, up to some 15 cm. long, which swam in shoals.

## Paleoecology

Mastodonsaurids were aquatic animals that rarely left water and may have been completely unable to leave the water, as large quantities of bones have been found that suggests that many species have died en masse when pools dried up during times of [drought](/source/Drought).[15] They mostly inhabited swampy pools and fed mainly on fish, whose remains have been found in fossilized [coprolites](/source/Coprolite).[15]

## See also

- [List of prehistoric amphibians](/source/List_of_prehistoric_amphibians)

## References

1. ^ [***a***](#cite_ref-SRR99_1-0) [***b***](#cite_ref-SRR99_1-1) Schoch, R.R. (1999). ["Comparative osteology of *Mastodonsaurus giganteus* (Jaeger, 1828) from the Middle Triassic (Lettenkeuper: Longobardian) of Germany (Baden-Württemberg, Bayern, Thüringen)"](https://web.archive.org/web/20110428055058/http://www-alt.naturkundemuseum-bw.de/stuttgart/pdf/b_pdf/B278.pdf) (PDF). *Stuttgarter Beiträge zur Naturkunde Serie B*. **278**: 1–175. Archived from [the original](http://www-alt.naturkundemuseum-bw.de/stuttgart/pdf/b_pdf/B278.pdf) (PDF) on 2011-04-28. Retrieved 2020-04-30.

1. **[^](#cite_ref-ingavat_2-0)** Ingavat, Rucha; Janvier, Phillippe (1981). "*Cyclotosaurus* cf. *Posthumus* Fraas (Capitosauridae, Stereospondyli) from the Huai Hin Lat Formation (Upper Triassic), Northeastern Thailand". *Geobios*. **14** (6): 711–25. [doi](/source/Doi_(identifier)):[10.1016/S0016-6995(81)80149-0](https://doi.org/10.1016%2FS0016-6995%2881%2980149-0).

1. ^ [***a***](#cite_ref-Watson1958_3-0) [***b***](#cite_ref-Watson1958_3-1) D. Watson (1958). ["A New Labyrinthodont (*Paracyclotosaurus*) From Trias of New South Wales"](https://biodiversitylibrary.org/page/2290486). Bulletin of the British Museum (Natural History). {{[cite journal](https://en.wikipedia.org/wiki/Template:Cite_journal)}}: Cite journal requires |journal= ([help](https://en.wikipedia.org/wiki/Help:CS1_errors#missing_periodical))

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1. **[^](#cite_ref-SFFK07_5-0)** Schoch, R.R.; Fastnacht, M.; Fichter, J.; Keller, T. (2007). ["Anatomy and relationships of the Triassic temnospondyl *Sclerothorax*"](http://www.app.pan.pl/archive/published/app52/app52-117.pdf) (PDF). *Acta Palaeontologica Polonica*. **52** (1): 117–136.

1. **[^](#cite_ref-:1_6-0)** Howie, A.A. (1970). "A new Capitosaurid Labrinthodont from East Africa". *Palaeontology*. **13**: 210–153.

1. **[^](#cite_ref-:3_7-0)** Brown, Barnum; Bird, Roland T. (Roland Thaxter) (1933). "A new genus of Stegocephalia from the Triassic of Arizona". *American Museum Novitates* (640). [hdl](/source/Hdl_(identifier)):[2246/2062](https://hdl.handle.net/2246%2F2062).

1. **[^](#cite_ref-:0_8-0)** Arbez, Thomas; Dahoumane, Anissa; Steyer, J-Sébastien (2017-01-20). ["Exceptional endocranium and middle ear of Stanocephalosaurus (Temnospondyli: Capitosauria) from the Triassic of Algeria revealed by micro-CT scan, with new functional interpretations of the hearing system"](https://hal.sorbonne-universite.fr/hal-01643473/file/ARBEZ_Thomas.pdf) (PDF). *Zoological Journal of the Linnean Society*. **180** (4): 910–929. [doi](/source/Doi_(identifier)):[10.1093/zoolinnean/zlw007](https://doi.org/10.1093%2Fzoolinnean%2Fzlw007). [ISSN](/source/ISSN_(identifier)) [0024-4082](https://search.worldcat.org/issn/0024-4082).

1. **[^](#cite_ref-:5_9-0)** Fortuny, Josep; Marcé-Nogué, Jordi; Steyer, J.-Sébastien; de Esteban-Trivigno, Soledad; Mujal, Eudald; Gil, Lluís (2016-07-26). ["Comparative 3D analyses and palaeoecology of giant early amphibians (Temnospondyli: Stereospondyli)"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4960601). *Scientific Reports*. **6** 30387. [Bibcode](/source/Bibcode_(identifier)):[2016NatSR...630387F](https://ui.adsabs.harvard.edu/abs/2016NatSR...630387F). [doi](/source/Doi_(identifier)):[10.1038/srep30387](https://doi.org/10.1038%2Fsrep30387). [ISSN](/source/ISSN_(identifier)) [2045-2322](https://search.worldcat.org/issn/2045-2322). [PMC](/source/PMC_(identifier)) [4960601](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4960601). [PMID](/source/PMID_(identifier)) [27457883](https://pubmed.ncbi.nlm.nih.gov/27457883).

1. **[^](#cite_ref-10)** Witzmann, Florian (2007-12-12). "A hemivertebra in a temnospondyl amphibian: the oldest record of scoliosis". *Journal of Vertebrate Paleontology*. **27** (4): 1043–1046. [doi](/source/Doi_(identifier)):[10.1671/0272-4634(2007)27\[1043:ahiata\]2.0.co;2](https://doi.org/10.1671%2F0272-4634%282007%2927%5B1043%3Aahiata%5D2.0.co%3B2). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634). [S2CID](/source/S2CID_(identifier)) [86113048](https://api.semanticscholar.org/CorpusID:86113048).

1. **[^](#cite_ref-Schoch2015_11-0)** Schoch, R.R. (2015). ["9. Amphibien und Chroniosuchier des Lettenkeupers"](http://www.palaeodiversity.org/pdf/08Suppl/09Palaeodiversity_SB_Schoch.pdf) [Amphibians and chroniosuchians from the Lettenkeuper] (PDF). *Palaeodiversity Supplement 1 Special Issue: Der Lettenkeuper – ein Fenster in die Zeit Vor den Dinosauriern* [*The Lettenkeuper – a Window on the Time before the Dinosaurs*] (in German): 203–230.

1. **[^](#cite_ref-12)** Damiani, R. (2008). ["A giant skull of the temnospondyl *Xenotosuchus africanus* from the Middle Triassic of South Africa and its ontogenetic implications"](http://www.app.pan.pl/archive/published/app53/app53-075.pdf) (PDF). *Acta Palaeontologica Polonica*. **53** (1): 75–84. [doi](/source/Doi_(identifier)):[10.4202/app.2008.0104](https://doi.org/10.4202%2Fapp.2008.0104). [S2CID](/source/S2CID_(identifier)) [59056642](https://api.semanticscholar.org/CorpusID:59056642).

1. **[^](#cite_ref-Morales_13-0)** Morales, M.; Shishkin, M. A. (2002). "A Re-Assessment of Parotosuchus africanus (Broom), a Capitosauroid Temnospondyl Amphibian from the Triassic of South Africa". *Journal of Vertebrate Paleontology*. **22** (1): 1–11. [doi](/source/Doi_(identifier)):[10.1671/0272-4634(2002)022\[0001:araopa\]2.0.co;2](https://doi.org/10.1671%2F0272-4634%282002%29022%5B0001%3Aaraopa%5D2.0.co%3B2). [JSTOR](/source/JSTOR_(identifier)) [4524188](https://www.jstor.org/stable/4524188). [S2CID](/source/S2CID_(identifier)) [86254209](https://api.semanticscholar.org/CorpusID:86254209).

1. **[^](#cite_ref-14)** Steyer, J. Sebastien (2003). "A revision of the early Triassic "capitosaurs" (Stegocephali, Stereospondyli) from Madagascar, with remarks on their comparative ontogeny". *Journal of Vertebrate Paleontology*. **23** (3): 544–555. [doi](/source/Doi_(identifier)):[10.1671/1740](https://doi.org/10.1671%2F1740). [S2CID](/source/S2CID_(identifier)) [85667716](https://api.semanticscholar.org/CorpusID:85667716).

1. ^ [***a***](#cite_ref-Benes,_Josef_1979_15-0) [***b***](#cite_ref-Benes,_Josef_1979_15-1) Benes, Josef. Prehistoric Animals and Plants. Prague, Artia, 1979.

## Sources

- Damiani, Ross J. (2000). "Early Triassic mastodonsaurids (Temnospondyli, Stereospondyli) from Western Australia, with remarks on mastodonsauroid palaeobiogeography". *Alcheringa: An Australasian Journal of Palaeontology*. **24** (4): 299–305. [doi](/source/Doi_(identifier)):[10.1080/03115510008619533](https://doi.org/10.1080%2F03115510008619533). [S2CID](/source/S2CID_(identifier)) [140541478](https://api.semanticscholar.org/CorpusID:140541478).

- Moser, Markus; Schoch, Rainer (2007). ["Revision of the Type Material and Nomenclature of Mastodonsaurus Giganteus (Jaeger) (Temnospondyli) from the Middle Triassic of Germany"](https://doi.org/10.1111%2Fj.1475-4983.2007.00705.x). *Palaeontology*. **50** (5): 1245–1266. [doi](/source/Doi_(identifier)):[10.1111/j.1475-4983.2007.00705.x](https://doi.org/10.1111%2Fj.1475-4983.2007.00705.x).

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 Mastodonsauridae Wikidata: Q255408 Wikispecies: Mastodonsauridae GBIF: 4815860 IRMNG: 116360 Open Tree of Life: 3620685 Paleobiology Database: 37107

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