Gavialidae

Gavialidae is a family of large semiaquatic crocodilians with elongated, narrow snouts. Gavialidae consists of two living species, the gharial (Gavialis gangeticus) and the false gharial (Tomistoma schlegelii), both occurring in Asia. Many extinct members are known from a broader range, including the recently extinct Hanyusuchus. Gavialids are generally regarded as lacking the jaw strength to capture the large mammalian prey favoured by crocodiles and alligators of similar size so their thin snout is best used to catch fish, however the false gharial has been found to have a generalist diet with mature adults preying upon larger vertebrates, such as ungulates.[1]

Gavialidae
Temporal range: Eocene,
Indian gharial, Gavialis gangeticus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Superfamily: Gavialoidea
Family: Gavialidae
Adams, 1854
Subfamilies

Taxonomy

The family Gavialidae was proposed by Arthur Adams in 1854 for reptiles with a very long and slender muzzle, webbed feet and nearly equal teeth.[2] It is currently recognized as a crown group,[3] meaning that it only includes the last common ancestor of all extant (living) gavialids (the gharial and false gharial) and their descendants (living or extinct).

Traditionally, crocodiles and alligators were considered more closely related and grouped together in the clade Brevirostres, to the exclusion of the gharials. This classification was based on morphological studies primarily focused on analyzing skeletal traits of living and extinct fossil species.[4] However, recent molecular studies using DNA sequencing have rejected Brevirostres upon finding the crocodiles and gavialids to be more closely related than the alligators.[5][6][7][3][8] The new clade Longirostres was named by Harshman et al. in 2003.[5]

In addition, these recent molecular DNA studies consistently indicate that the false gharial (Tomistoma) (and by inference other related extinct forms) traditionally viewed as belonging to the crocodylian subfamily Tomistominae actually belong to Gavialoidea (and Gavialidae).[5][9][10][6][7][3][8] As its name suggests, the false gharial was once thought to be only distantly related to the gharial despite its similar appearance. The false gharial and other tomistomines were traditionally classified within the superfamily Crocodyloidea as close relatives of crocodiles, based solely on morphological evidence.[9]

A 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data established the inter-relationships within Crocodilia,[3] which was expanded upon in 2021 by Hekkala et al. using paleogenomics by extracting DNA from the extinct Voay.[8] The tip dating analysis resolved the extinct Thoracosaurus and similar extinct close relatives ("thoracosaurs") as outside of Gavialoidea due to the large time difference. They concluded that the only possible explanation for the morphological data placing thoracosaurs within the gharial lineage was a significant amount of homoplastic convergence between thoracosaurs and Gavialis.[3]

The below cladogram from latest study shows Gavialidae's placement within Crocodylia:

Crocodylia
Alligatoroidea

extinct basal Alligatoroids†

Alligatoridae
Caimaninae

Caiman

Melanosuchus

Paleosuchus

Alligatorinae

Alligator

(crown group)
(stem-based group)
Longirostres
Crocodyloidea

"Crocodylus" megarhinus†

Crocodylidae

Crocodylus

Mecistops

Osteolaemus

(crown group)
(stem-based group)
Gavialoidea

Kentisuchus†

Maroccosuchus†

Paratomistoma†

Dollosuchoides†

Tomistoma cairense†

Gavialidae

Gavialis

Tomistoma

(crown group)
(stem-based group)
(crown group)
(crown group)

Here is a more detailed cladogram that shows the proposed phylogeny of Gavialidae including extinct members:[11]

Crocodyloidea

Gavialoidea

†Maroccosuchus zennaroi

†Megadontosuchus arduini

†Dollosuchoides densmorei

†Xaymacachampsa kugleri

†Kentisuchus astrei

†Kentisuchus spenceri

Gavialidae

†Tomistoma cairense

†Tomistoma coppensi

†Maomingosuchus petrolica

Tomistominae

Tomistoma schlegelii, false gharial

†Tomistoma lusitanica

†Gavialosuchus eggenburgensis

†Melitosaurus champsoides

†Tomistoma calaritanum

†Tomistoma gaudense

†Thecachampsa carolinensis

†Thecachampsa antiqua

Gavialinae

†Paratomistoma courti

†Penghusuchus pani

†Toyotamaphimeia machikanensis

†Hanyusuchus sinensis

†Eosuchus lerichei

†Eosuchus minor

†Ocepesuchus eoafricanus

†Eothoracosaurus mississippiensis

†Thoracosaurus macrorhynchus

†Thoracosaurus neocesariensis

†Aktiogavialis puertoricensis

†Eogavialis africanum

†Argochampsa krebsi

†Piscogavialis jugaliperforatus

†Ikanogavialis gameroi

†Siquisiquesuchus venezuelensis

†Dadagavialis gunai

†Gryposuchus neogaeus

†Gryposuchus croizati

†Aktiogavialis caribesi

†Gryposuchus pachakamue

†Gryposuchus colombianus

†Rhamphosuchus crassidens

†Myanmar gavialid

†Gavialis lewisi

†Gavialis bengawanicus

Gavialis gangeticus, gharial

†Siwalik Gavialis

Species list
See also: List of crocodilians

Family Gavialidae

† Indicates extinct group

Extant species
ImageScientific nameCommon NameDistribution
Gavialis gangeticusGharialIndia
Tomistoma schlegeliiFalse gharial, Malayan gharial, Sunda gharial and tomistomaPeninsular Malaysia, Borneo, Sumatra, and Java.

References
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  1. Magnusson, W. E. (1998). Cogger, H. G.; Zweifel, R. G. (eds.). Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. pp. 229–230. ISBN 978-0-12-178560-4.
  2. Adams, A. (1854). "II. Order – Emydosaurians (Emydosauria)". In Adams, A.; Baikie, W. B.; Barron, C. (eds.). A Manual of Natural History, for the Use of Travellers: Being a Description of the Families of the Animal and Vegetable Kingdoms: with Remarks on the Practical Study of Geology and Meteorology. London: John Van Voorst. pp. 70–71.
  3. 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.
  4. Holliday, Casey M.; Gardner, Nicholas M. (2012). Farke, Andrew A (ed.). "A new eusuchian crocodyliform with novel cranial integument and its significance for the origin and evolution of Crocodylia". PLOS ONE. 7 (1): e30471. Bibcode:2012PLoSO...730471H. doi:10.1371/journal.pone.0030471. PMC 3269432. PMID 22303441.
  5. 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.
  6. 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.
  7. 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.
  8. Hekkala, E.; Gatesy, J.; Narechania, A.; Meredith, R.; Russello, M.; Aardema, M. L.; Jensen, E.; Montanari, S.; Brochu, C.; Norell, M.; Amato, G. (2021-04-27). "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. ISSN 2399-3642. PMC 8079395. PMID 33907305.
  9. 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.
  10. 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.
  11. Iijima M, Qiao Y, Lin W, Peng Y, Yoneda M, Liu J (2022). "An intermediate crocodylian linking two extant gharials from the Bronze Age of China and its human-induced extinction". Proceedings of the Royal Society B: Biological Sciences. 289 (1970): Article ID 20220085. doi:10.1098/rspb.2022.0085. PMID 35259993.
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