Gavialidae

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Gavialidae
Temporal range: Eocene, 38–0 Ma
Indian Gharial Crocodile Digon3.JPG
Indian gharial, Gavialis gangeticus
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Superfamily: Gavialoidea
Family: Gavialidae
Adams, 1854
Subfamilies

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.[1]

Taxonomy[edit]

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 Caiman crocodilus llanos white background.JPG

Melanosuchus Melanosuchus niger white background.jpg

Paleosuchus Dwarf Caiman white background.jpg

Alligatorinae

Alligator Alligator white background.jpg

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

"Crocodylus" megarhinus

Crocodylidae

Crocodylus Siamese Crocodile white background.jpg

Mecistops Crocodylus cataphractus faux-gavial d'Afrique2 white background.JPG

Osteolaemus Bristol.zoo.westafrican.dwarf.croc.arp. white background.jpg

(crown group)
(stem-based group)
Gavialoidea

Kentisuchus

Maroccosuchus

Paratomistoma

Dollosuchoides

Tomistoma cairense

Gavialidae

Gavialis Gavialis gangeticus (Gharial, Gavial) white background.jpg

Tomistoma Tomistoma schlegelii. white background.JPG

(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[edit]

Family Gavialidae

† Indicates extinct group

Extant species[edit]

Image Scientific name Common Name Distribution
Indian Gharial Crocodile Digon3.JPG Gavialis gangeticus Gharial India
False Gharials (Tomistoma schlegelii) (6749856797).jpg Tomistoma schlegelii False gharial, Malayan gharial, Sunda gharial and tomistoma Peninsular Malaysia, Borneo, Sumatra, and Java.

References[edit]

  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. ^ a b c d e f 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. ^ a b c 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. ^ a b 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. ^ a b 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. ^ a b c 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. ^ a b 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.