Tomistoma

Tomistoma is a genus of gavialid crocodilians. They are noted for their long narrow snouts used to catch fish, similar to the gharial. Tomistoma contains one extant (living) member, the false gharial (Tomistoma schlegelii), as well as potentially several extinct species: T. cairense, T. lusitanicum and T. coppensi. Previously assigned extinct species known from fossils are reclassified as different genera such as Eogavialis, Toyotamaphimeia and Sutekhsuchus.^[2][3][4]

Tomistoma Temporal range: Eocene - Recent, 47.8–0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
False gharial (Tomistoma schlegelii)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	Archosauriformes
Order:	Crocodilia
Family:	Gavialidae
Subfamily:	Tomistominae
Genus:	Tomistoma S. Müller, 1846
Species
Tomistoma schlegelii †Tomistoma cairense †Tomistoma coppensi †Tomistoma lusitanicum

Unlike the gharial, the false gharial's snout broadens considerably towards the base and so is more similar to those of true crocodiles than the gharial, whose osteology indicated a distinct lineage from all other living crocodilians.^[5] However, although more morphologically similar to Crocodylidae based on skeletal features, recent molecular studies using DNA sequencing consistently indicate that the false gharial and by inference other related extinct forms traditionally viewed as belonging to the crocodylian subfamily Tomistominae actually belong to Gavialoidea and Gavialidae.^[6][7][8]

Fossil dorsal plates of "Tomistoma" calaritanum

Fossils of extinct Tomistoma species have been found in deposits of Paleogene, Neogene, and Quaternary ages in Uganda, Italy, Portugal, Egypt and India, but nearly all of them are likely to be distinct genera due to older age compared to the false gharial.^[9]

The below cladogram of the major living crocodile groups is based on molecular studies and shows the false gharial's close relationships:^{[10][11][6][7][8]}

Crocodilia	Alligatoridae Caimaninae Caiman Melanosuchus Paleosuchus Alligatorinae Alligator Longirostres Crocodylidae Crocodylus Mecistops Osteolaemus Gavialidae Gavialis Tomistoma

Here is a more detailed cladogram from a 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data that shows the false gharial's proposed placement within Gavialidae, including extinct members:^[7]

Gavialoidea	Gavialidae Gavialis gangeticus Gharial Gavialis bengawanicus† Gavialis browni† Gryposuchus colombianus† Ikanogavialis† Gryposuchus pachakamue† Piscogavialis† Harpacochampsa† Toyotamaphimeia† Penghusuchus† Gavialosuchus† Tomistoma lusitanicum† Tomistoma schlegelii False gharial (crown group) Tomistoma cairense† Dollosuchoides† Maroccosuchus† Paratomistoma† Kentisuchus†
(stem-based group)

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. Buffetaut, E. (1982). "Systématique, origine et évolution des Gavialidae Sud-Américains". Geobios. 15 (Suppl 1): 127–140. doi:10.1016/S0016-6995(82)80107-1.
3. Cho, Yi-Yang; Tsai, Cheng-Hsiu (2023-06-29). "Crocodylian princess in Taiwan: Revising the taxonomic status of Tomistoma taiwanicus from the Pleistocene of Taiwan and its paleobiogeographic implications". Journal of Paleontology. 97 (4): 927–940. Bibcode:2023JPal...97..927C. doi:10.1017/jpa.2023.36. ISSN 0022-3360.
4. Burke, P. M. J.; Nicholl, C. S. C.; Pittard, B. E.; Sallam, H.; Mannion, P. D. (2024). "The anatomy and taxonomy of the North African Early Miocene crocodylian 'Tomistoma' dowsoni and the phylogenetic relationships of gavialoids". Journal of Systematic Palaeontology. 22 (1). 2384548. doi:10.1080/14772019.2024.2384548.
5. Piras, P., Colangelo, P., Adams, D. C., Buscalioni, A., Cubo, J., Kotsakis, T., & Raia, P. (2010). The Gavialis–Tomistoma debate: the contribution of skull ontogenetic allometry and growth trajectories to the study of crocodylian relationships. Evolution & development, 12(6): 568−579.
6. 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. Bibcode:2012PLoSO...731781E. doi:10.1371/journal.pone.0031781. PMC 3303775. PMID 22431965.
7. Lee, M. S. Y.; Yates, A. M. (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.
8. Hekkala, E.; Gatesy, J.; Narechania, A.; Meredith, R.; Russello, M.; Aardema, M. L.; Jensen, E.; Montanari, S.; Brochu, C.; Norell, M.; Amato, G. (2021). "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.
9. "Fossilworks: Tomistoma". fossilworks.org.
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". Systematic Biology. 52 (3): 386–402. doi:10.1080/10635150309323. PMID 12775527.
11. 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.