Gavialosuchus

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.

Gavialosuchus Temporal range: Early Miocene, 20.4–16 Ma^[1] PreꞒ Ꞓ O S D C P T J K Pg N ↓
Gavialosuchus eggenburgensis skull
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	Archosauriformes
Order:	Crocodilia
Family:	Gavialidae
Genus:	†Gavialosuchus Toula and Kail, 1885
Type species
†Gavialosuchus eggenburgensis Toula and Kail, 1885

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.^[2] Piras et al. (2007) advocated transferring both G. americanus and G. carolinensis to Thecachampsa as distinct species of the latter genus, however.^[3] 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).^[4] 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.^[5] 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.^[6] Weems (2018) agreed with Piras et al. (2007) and Brochu & Storrs (2012) at americanus and carolinensis are part of Thecachampsa.^[7]

Below is a cladogram based morphological studies comparing skeletal features that shows Gavialosuchus as a member of Tomistominae, related to the false gharial:^[8]

Crocodylidae	Crocodylinae Tomistominae Xaymacachampsa† Megadontosuchus† Kentisuchus† Maroccosuchus† Dollosuchoides† Thecachampsa† Penghusuchus† Toyotamaphimeia† Tomistoma cairense† Maomingosuchus† Tomistoma schlegelii False gharial Gavialosuchus† Tomistoma lusitanicum† Paratomistoma† Tomistoma coppensi†

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.^[9] 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.^{[10][11][12][13][14][15][16]}

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:^[15]

Gavialidae	Gavialis gangeticus Gharial Gavialis bengawanicus† Gavialis browni† Gryposuchus colombianus† Ikanogavialis† Gryposuchus pachakamue† Piscogavialis† Harpacochampsa† Toyotamaphimeia† Penghusuchus† Gavialosuchus† Tomistoma lusitanicum† Tomistoma schlegelii False gharial

Ecology

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

References

1. Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ. 9: e12094. doi:10.7717/peerj.12094. PMC 8428266. PMID 34567843.
2. 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.
3. Piras, P.; Delfino, M.; Del Favero, L.; Kotsakis, T. (2007). "Phylogenetic position of the crocodylian Megadontosuchus arduini and tomistomine palaeobiogeography" (PDF). Acta Palaeontologica Polonica. 52 (2): 315–328.
4. 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" (PDF). Journal of Vertebrate Paleontology. 28 (2): 409–421. doi:10.1671/0272-4634(2008)28[409:TOACPP]2.0.CO;2. S2CID 86503283.
5. 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. Bibcode:2009CaJES..46..529S. doi:10.1139/E09-036.
6. Brochu, C. A.; Storrs, G. W. (2012). "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. doi:10.1080/02724634.2012.652324. S2CID 85103427.
7. Weems, Robert E. (2018). "Crocodilians of the Calvert Cliffs". In Stephen J. Godfrey (ed.). The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA. Smithsonian Contributions to Paleobiology. Vol. 100. pp. 213–240. doi:10.5479/si.1943-6688.100.
8. 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. 496: 346–360. Bibcode:2018PPP...496..346I. doi:10.1016/j.palaeo.2018.02.002.
9. 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.
10. Harshman, J.; Huddleston, C. J.; Bollback, J. P.; Parsons, T. J.; Braun, M. J. (2003). "True and false gharials: A nuclear gene phylogeny of crocodylia" (PDF). Systematic Biology. 52 (3): 386–402. doi:10.1080/10635150309323. PMID 12775527.
11. Gatesy, Jorge; Amato, G.; Norell, M.; DeSalle, R.; Hayashi, C. (2003). "Combined support for wholesale taxic atavism in gavialine crocodylians" (PDF). Systematic Biology. 52 (3): 403–422. doi:10.1080/10635150309329. PMID 12775528.
12. Willis, R. E.; McAliley, L. R.; Neeley, E. D.; Densmore Ld, L. D. (June 2007). "Evidence for placing the false gharial (Tomistoma schlegelii) into the family Gavialidae: Inferences from nuclear gene sequences". Molecular Phylogenetics and Evolution. 43 (3): 787–794. doi:10.1016/j.ympev.2007.02.005. PMID 17433721.
13. Gatesy, J.; Amato, G. (2008). "The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships". Molecular Phylogenetics and Evolution. 48 (3): 1232–1237. doi:10.1016/j.ympev.2008.02.009. PMID 18372192.
14. 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). Claessens, Leon (ed.). "Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation". PLOS ONE. 7 (3): e31781. Bibcode:2012PLoSO...731781E. doi:10.1371/journal.pone.0031781. PMC 3303775. PMID 22431965.
15. 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". Proceedings of the Royal Society B. 285 (1881). doi:10.1098/rspb.2018.1071. PMC 6030529. PMID 30051855.
16. 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. 4 (1): 505. doi:10.1038/s42003-021-02017-0. PMC 8079395. PMID 33907305.