Gavialosuchus Explained

Gavialosuchus is an extinct genus of gavialoid crocodylian from the early Miocene of Europe. Currently only one species is recognized, as a few other species of Gavialosuchus have since been reclassified to other genera.

Taxonomy

The type species, G. eggenburgensis, is known from the early Miocene of Austria. Two other species - G. americanus and G. carolinensis - have since been reclassified to other genera.

Myrick Jr. (2001) proposed synonymizing Gavialosuchus americanus with Thecachampsa antiqua.[1] Piras et al. (2007) advocated transferring both G. americanus and G. carolinensis to Thecachampsa as distinct species of the latter genus, however.[2] Jouve et al. (2008) retained G. americanus in Gavialosuchus and found it to be the sister group of G. eggenburgensis (G. carolinensis was not discussed).[3] However, Jouve et al. (2008) didn't test Thecachampsa antiqua in their phylogenetic analysis. Shan et al. (2009) found that G. americanus and G. eggenburgensis are not sister taxa. However, they didn't include T. antiqua and G. carolinensis in their analysis.[4] Christopher A. Brochu and Glenn W. Storrs (2012) tested all four species, along with other crocodyloids, and found relatively strong support for Piras et al. (2007) suggestion.[5] Weems (2018) agreed with Piras et al. (2007) and Brochu & Storrs (2012) at americanus and carolinensis are part of Thecachampsa.[6]

Below is a cladogram based morphological studies comparing skeletal features that shows Gavialosuchus as a member of Tomistominae, related to the false gharial:[7]

Based on morphological studies of extinct taxa, the tomistomines (including the living false gharial) were long thought to be classified as crocodiles and not closely related to gavialoids.[8] However, recent molecular studies using DNA sequencing have consistently indicated that the false gharial (Tomistoma) (and by inference other related extinct forms in Tomistominae) actually belong to Gavialoidea.[9] [10] [11] [12] [13] [14] [15]

Below is a cladogram from a 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data that shows Gavialosuchus as a gavialid, related to both the gharial and the false gharial:[14]

Ecology

Unlike its modern fresh water relatives, Gavialosuchus was an estuarine and coastal water crocodilian, living in shallow marine waters.

Notes and References

  1. Myrick . A.C. Jr. . 2001 . Thecachampsa antiqua (Leidy, 1852) (Crocodylidae: Thoracosaurinae) from the fossil marine deposits at Lee Creek Mine, Aurora, North Carolina, USA . Smithsonian Contributions to Paleobiology . 90 . 219–225.
  2. Piras . P. . Delfino, M. . Del Favero, L. . Kotsakis, T. . 2007 . Phylogenetic position of the crocodylian Megadontosuchus arduini and tomistomine palaeobiogeography . Acta Palaeontologica Polonica . 52 . 2 . 315–328 .
  3. Jouve . Stéphane . Bardet, Nathalie . Jalil, Nour-Eddine . Suberbiola, Xabier Pereda . Bouya . Baâda . Amaghzaz, Mbarek . 2008 . The oldest African crocodylian: phylogeny, paleobiogeography, and differential survivorship of marine reptiles through the Cretaceous-Tertiary Boundary . Journal of Vertebrate Paleontology . 28 . 2 . 409–421 . 10.1671/0272-4634(2008)28[409:TOACPP]2.0.CO;2 . 86503283 .
  4. Shan, Hsi-yin . Wu, Xiao-chun . Cheng, Yen-nien . Sato, Tamaki . 2009 . A new tomistomine (Crocodylia) from the Miocene of Taiwan . Canadian Journal of Earth Sciences . 46 . 7 . 529–555 . 10.1139/E09-036. 2009CaJES..46..529S .
  5. Brochu . C. A. . Storrs . G. W. . 10.1080/02724634.2012.652324 . A giant crocodile from the Plio-Pleistocene of Kenya, the phylogenetic relationships of Neogene African crocodylines, and the antiquity of Crocodylus in Africa . Journal of Vertebrate Paleontology . 32 . 3 . 587 . 2012 . 85103427 .
  6. Book: Weems . Robert E. . Crocodilians of the Calvert Cliffs . The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA . Stephen J. Godfrey . Smithsonian Contributions to Paleobiology . 2018 . 100 . 100 . 213–240 . 10.5479/si.1943-6688.100.
  7. Iijima. Masaya. Momohara. Arata. Kobayashi. Yoshitsugu. Hayashi. Shoji. Ikeda. Tadahiro. Taruno. Hiroyuki. Watanabe. Katsunori. Tanimoto. Masahiro. Furui. Sora. 2018-05-01. Toyotamaphimeia cf. machikanensis (Crocodylia, Tomistominae) from the Middle Pleistocene of Osaka, Japan, and crocodylian survivorship through the Pliocene-Pleistocene climatic oscillations. Palaeogeography, Palaeoclimatology, Palaeoecology. en. 496. 346–360. 10.1016/j.palaeo.2018.02.002. 2018PPP...496..346I .
  8. Brochu . C.A. . Gingerich, P.D. . 2000 . New tomistomine crocodylian from the Middle Eocene (Bartonian) of Wadi Hitan, Fayum Province, Egypt . University of Michigan Contributions from the Museum of Paleontology . 30 . 10 . 251–268.
  9. 12775527 . 2003 . Harshman . J. . True and false gharials: A nuclear gene phylogeny of crocodylia . Systematic Biology . 52 . 3 . 386–402 . Huddleston . C. J. . Bollback . J. P. . Parsons . T. J. . Braun . M. J. . 10.1080/10635150309323 . free . 2021-06-29 . 2022-10-09 . https://ghostarchive.org/archive/20221009/http://si-pddr.si.edu/bitstream/handle/10088/6275/2003C_Harshman_et_al.pdf . dead .
  10. Gatesy . Jorge . Amato, G. . Norell, M. . DeSalle, R. . Hayashi, C. . 2003 . Combined support for wholesale taxic atavism in gavialine crocodylians . Systematic Biology . 52 . 3 . 403–422 . 10.1080/10635150309329. 12775528 . free .
  11. Willis . R. E. . McAliley . L. R. . Neeley . E. D. . Densmore Ld . L. D. . Evidence for placing the false gharial (Tomistoma schlegelii) into the family Gavialidae: Inferences from nuclear gene sequences . 10.1016/j.ympev.2007.02.005 . Molecular Phylogenetics and Evolution . 43 . 3 . 787–794 . June 2007 . 17433721.
  12. Gatesy . J. . Amato . G. . 2008 . The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships . Molecular Phylogenetics and Evolution. 48 . 3 . 1232–1237 . 10.1016/j.ympev.2008.02.009. 18372192.
  13. Erickson, G. M.. Gignac, P. M.. Steppan, S. J.. Lappin, A. K.. Vliet, K. A.. Brueggen, J. A.. Inouye, B. D.. Kledzik, D.. Webb, G. J. W. . 2012 . Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation . PLOS ONE . 7 . 3 . e31781 . 10.1371/journal.pone.0031781. Claessens. Leon. 2012PLoSO...731781E . 22431965 . 3303775. free.
  14. Michael S. Y. Lee . Adam M. Yates . 27 June 2018 . Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil . . 285 . 1881 . 10.1098/rspb.2018.1071 . 30051855 . 6030529 . free.
  15. Hekkala . E. . Gatesy . J. . Narechania . A. . Meredith . R. . Russello . M. . Aardema . M. L. . Jensen . E. . Montanari . S. . Brochu . C. . Norell . M. . Amato . G. . 2021-04-27 . Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus . Communications Biology . en . 4 . 1 . 505 . 10.1038/s42003-021-02017-0 . 33907305 . 8079395 . free.

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