Tomistoma is a genus of gavialidcrocodilians. 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. lusitanicumT. coppensi, and T. dowsoni. However, these species may need to be reclassified to different genera as studies have shown them to be paraphyletic, for example: previously assigned species T. taiwanicus from Taiwan, is reclassified to the genus Toyotamaphimeia, and T. dowsoni should be excluded from Tomistoma based on phylogenetic analysis.[2][3][4][5][6]
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.[7] 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.[8][9][10][11][12][13][2][14]
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.[15]
The below cladogram of the major living crocodile groups is based on molecular studies and shows the false gharial's close relationships:[9][12][13][2][14]
^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.
^Willis, R. E.; McAliley, L. R.; Neeley, E. D.; Densmore Ld, L. D. (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. PMID17433721.