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]
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.