TITLE=PHYLOGENETIC ANALYSIS OF A NEW MORPHOLOGICAL DATASET ELUCIDATES THE EVOLUTIONARY HISTORY OF CROCODYLIA AND RESOLVES THE LONG-STANDING GHARIAL PROBLEM

PEERJ >VOLUME=9

DOI=10.7717/PEERJ.12094

PMC=8428266, free, }}| image = Tomistoma_schlegelii_fg01.JPG

Berlin Zoological Garden>Berlin Zoo, Germany| status = EN| status_system = IUCN3.1

TOMISTOMA SCHLEGELII

AUTHOR=SHANEY, K.

AUTHOR3=SIMPSON, B.K.

AUTHOR5=SIDELEAU, B.

PAGE=E.T21981A214287051

Salomon MÃ¼ller>MÃ¼ller, 1846| species = schlegelii

Salomon MÃ¼ller>MÃ¼ller, 1838)| range_map = The_range_of_the_False_gharial.png| range_map_caption = Range of the false gharial| synonyms = Pseudogavialis schlegelii}}The false gharial (Tomistoma schlegelii), also known by the names Malayan gharial, Sunda gharial and tomistoma, is a freshwater crocodilian of the family Gavialidae native to Peninsular Malaysia, Borneo, Sumatra and Java. It is listed as Endangered on the IUCN Red List, as the global population is estimated at around 2,500 to 10,000 mature individuals.The specific name schlegelii honors Hermann Schlegel.JOURNAL, MÃ¼ller, S., Salomon MÃ¼ller, 1838, Waarnemingen over de Indische Krokodillen en Beschrijving van eene nieuwe Soort, Tijdschrift voor Natuurlijke Geschiedenis en Physiologie, 5, 61â€“87, nl,weblink BOOK, Beolens, B., Watkins, M., Grayson, M., amp, 2011, Tomistoma schlegelii, 235, The Eponym Dictionary of Reptiles, Baltimore, Johns Hopkins University Press, 978-1-4214-0135-5,

Characteristics

File:Tomistoma schlegelii.jpg|thumb|Close-up of a false gharial at the Tierpark Berlin Tierpark BerlinFile:Tomistomaskull.JPG|thumb|Skull of a false gharial at the Zoological Museum of the Zoological Institute of the Russian Academy of Sciences, St. Petersburg St. PetersburgThe false gharial is dark reddish-brown above with dark brown or black spots and cross-bands on the back and tail. Ventrals are grayish-white, with some lateral dark mottling. Juveniles are mottled with black on the sides of the jaws, body, and tail. The smooth and unornamented snout is extremely long and slender, parallel sided, with a length of 3.0 to 3.5 times the width at the base. All teeth are long and needle-like, interlocking on the insides of the jaws, and are individually socketed. The dorsal scales are broad at midbody and extend onto the sides of the body. The digits are webbed at the base. Integumentary sensory organs are present on the head and body scalation. Scales behind the head are frequently a slightly enlarged single pair. Some individuals bear a number of adjoining small keeled scales. Scalation is divided medially by soft granular skin. Three transverse rows of two enlarged nuchal scales are continuous with the dorsal scales, which consist of 22 transverse rows of six to eight scales, are broad at midbody and extend onto the sides of the body. Nuchal and dorsal rows equals a total of 22 to 23 rows. It has 18 double-crested caudal whorls and 17 single-crested caudal whorls. The flanks have one or two longitudinal rows of six to eight very enlarged scales on each side.Brazaitis, P. (2001) A Guide to the Identification of the Living Species of Crocodilians. Science Resource Center, Wildlife Conservation SocietyThe false gharial has one of the slimmest snouts of any living crocodilian, comparable to that of the slender-snouted crocodile and the freshwater crocodile in slenderness; only that of the gharial is noticeably slimmer.JOURNAL, Piras, P., amp, Colangelo, P., 2010, The Gavialisâ€“Tomistoma debate: the contribution of skull ontogenetic allometry and growth trajectories to the study of crocodylian relationships, Evolution & Development, 12, 6, 568âˆ’579, Adams, D. C., Buscalioni, A., Cubo, J., Kotsakis, T., Raia, P., 10.1111/j.1525-142X.2010.00442.x, 21040423, 8231693, Three mature males kept in captivity measured {{cvt|3.6|to|3.9|m}} and weighed {{cvt|190|to|210|kg}}, while a female measured {{cvt|3.27|m}} and weighed {{cvt|93|kg}}.BOOK, Mathew, A., Ganesan, M., Majid, R. A., Beastall, C., amp, 2011, Breeding of False Gharial, Tomistoma schlegelii, at Zoo Negara, Malaysia, Zoo Negara,weblink 2012-06-13, 2018-01-27,weblink" title="web.archive.org/web/20180127212512weblink">weblink dead, Females are up to {{cvt|4|m}} long.JOURNAL, MilÃ n, J., amp, Hedegaard, R., 2010, Interspecific variation in tracks and trackways from extant crocodylians, New Mexico Museum of Natural History and Science Bulletin, 51, 15â€“2, Males can grow up to {{Cvt|5|m|ft|abbr=on}} in length and weigh up to {{Cvt|600|kg|lb}}.JOURNAL, Ahmad, A. A., Dorrestein, G. M., Oh, S. J. W. Y., Hsu, C. D., Multi-organ metastasis of fibrolamellar hepatocellular carcinoma in a Malayan Gharial (Tomistoma schlegelii), Journal of Comparative Pathology, 2017, 157, 2, 80â€“84, 10.1016/j.jcpa.2017.06.007, 28942308, The false gharial apparently has the largest skull of any extant crocodilian, in part because of the great length of the slender snout. Out of the eight longest crocodilian skulls from existing species that could be found in museums around the world, six of these belonged to false gharials. The longest crocodilian skull belonging to an extant species was of this species and measured {{cvt|84|cm}} in length, with a mandibular length of {{cvt|104|cm}}. Most of the owners of these enormous skulls had no confirmed (or even anecdotal) total measurements for the animals, but based on the known skull-to-total length ratio for the species they would measure approximately {{cvt|5.5|to|6.1|m}} in length.JOURNAL, Romulus Whitaker, Whitaker, R., Whitaker, N., amp, 2008, Who's got the biggest?, Crocodile Specialist Group Newsletter 27, 4, 26âˆ’30,weblink

Three individuals ranging from {{cvt|2.9|to|4.05|m}} in length and weighing from {{cvt|79|to|255|kg}} had a bite force of {{cvt|1704-6450|N|lk=on}}.JOURNAL, 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., amp, 2012, Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation, PLoS One, 7, 3, e31781, free, 10.1371/journal.pone.0031781, 2012PLoSO...731781E, 22431965, 3303775,

Taxonomy

The scientific name Crocodilus (Gavialis) schlegelii was proposed by Salomon MÃ¼ller in 1838 who described a specimen collected in Borneo.JOURNAL, MÃ¼ller, S., 1838, Waarnemingen over de Indische Krokodilen en beschrijving eene nieuwe soort, Tijdschrift Vorr Naturrlijke Geschiendes en Physiologie, 5, 61â€“87,weblink In 1846, he proposed to use the name Tomistoma schlegelii, if it needs to be placed in a distinct genus.JOURNAL, MÃ¼ller, S., 1846, Ãœber den Charakter der Thierwelt auf den Inseln des indischen Archipels, ein Beitrag zur Naturgeschichte, Archiv fÃ¼r Naturgeschichte, 12, 109â€“128,weblink The genus Tomistoma potentially also contains several extinct species like T. cairense, T. lusitanicum, T. taiwanicus, and T. coppensi. However, these species may need to be reclassified to different genera as evidence suggests they may be paraphyletic.JOURNAL, Iijima, M., Momohara, A., Kobayashi, Y., Hayashi, S., Ikeda, T., Taruno, H., Watanabe, K., Tanimoto, M., Furui, S., 2018, Toyotamaphimeia cf. machikanensis (Crocodylia, Tomistominae) from the Middle Pleistocene of Osaka, Japan, and crocodylian survivorship through the Pliocene-Pleistocene climatic oscillations,weblink Palaeogeography, Palaeoclimatology, Palaeoecology, 496, 346â€“360, 10.1016/j.palaeo.2018.02.002, 2018PPP...496..346I, The false gharial's snout broadens considerably towards the base and so is more similar to those of true crocodiles than to the gharial (Gavialis gangeticus), whose osteology indicated a distinct lineage from all other living crocodilians. 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.JOURNAL, Molecular Systematics of the Order Crocodilia, American Zoologist, 29, 3, 831â€“841, 10.1093/icb/29.3.831, 1989, Densmore, L. D., Owen, R. D., free, JOURNAL, 12775527, 2003, Harshman, J., True and false gharials: A nuclear gene phylogeny of crocodylia, Systematic Biology, 52, 3, 386â€“402, Huddleston, C. J., Bollback, J. P., Parsons, T. J., Braun, M. J., 10.1080/10635150309323, free, JOURNAL, Gatesy, J., Amato, G., Norell, M., DeSalle, R., H. C., 2003, Combined support for wholesale taxic atavism in gavialine crocodylians, Systematic Biology, 52, 3, 403â€“422, 10.1080/10635150309329, 12775528, free, JOURNAL, Willis, R. E., McAliley, L. R., Neeley, E. D., Densmore, L. D., Evidence for placing the false gharial (Tomistoma schlegelii) into the family Gavialidae: Inferences from nuclear gene sequences, 10.1016/j.ympev.2007.02.005, Molecular Phylogenetics and Evolution, 43, 3, 787â€“794, 2007, 17433721, JOURNAL, Gatesy, J., Amato, G., 2008, The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships, Molecular Phylogenetics and Evolution, 48, 3, 1232â€“1237, 10.1016/j.ympev.2008.02.009, 18372192, JOURNAL, 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., amp, 2012, Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation, PLOS One, 7, 3, e31781, 10.1371/journal.pone.0031781, 2012PLoSO...731781E, 22431965, 3303775, free, JOURNAL, 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, 10.1098/rspb.2018.1071, 30051855, 6030529, free, JOURNAL, 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, 10.1038/s42003-021-02017-0, 33907305, 8079395, free, (File:Gavialidae - Tomistoma calaritanus.JPG|thumb|Fossil dorsal plates of "Tomistoma" calaritanus)Fossils of extinct Tomistoma species have been found in deposits of Paleogene, Neogene, and Quaternary ages in Taiwan, 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.WEB,weblink Fossilworks: Tomistoma, Fossilworks, The below cladogram of the major living crocodile groups is based on molecular studies and shows the false gharial's close relationships:{{clade| style=font-size:85%;line-height:85%|label1=Crocodilia|1={{clade

|label1=Alligatoridae
|1={{clade
|label1=Caimaninae
|1={{clade
|1={{clade
|1=Caiman (File:Caiman crocodilus llanos white background.JPG|90 px)
|2=Melanosuchus (File:Melanosuchus niger white background.jpg|120 px) }}
|2=Paleosuchus (File:Dwarf Caiman white background.jpg|90 px) }}
|label2=Alligatorinae
|2=Alligator (File:Alligator white background.jpg|100 px) }}
|label2=Longirostres
|2={{clade
|label1=Crocodylidae
|1={{clade
|1=Crocodylus (File:Siamese Crocodile white background.jpg|90 px)
|2={{clade
|1=Mecistops (File:Crocodylus cataphractus faux-gavial d'Afrique2 white background.JPG|90 px)
|2=Osteolaemus (File:Bristol.zoo.westafrican.dwarf.croc.arp. white background.jpg|90 px) }} }}
|label2=Gavialidae
|2={{clade
|1=Gavialis (File:Gavialis gangeticus (Gharial, Gavial) white background.jpg|110 px)
|2=Tomistoma (File:Tomistoma schlegelii. white background.JPG|90 px)

}} }} }} }}The following cladogram shows the false gharial's placement within the Gavialidae; it is based on a tip dating study, for which morphological, DNA sequencing and stratigraphic data were analysed:{hide}clade| style=font-size:85%;line-height:85%|label1=Gavialoidea

stem-based taxon>stem-based group)|1={{clade

|1={{clade
|1={{clade
|1={{clade
|label1=Gavialidae
|sublabel1=(crown group)
|1={{clade
|1={{clade
|1={{clade
|1={{clade
|1={{clade
|1={{clade
|1={{clade
|1={{clade
|1=Gharial
|2=Gavialis bengawanicus{{extinct{edih} }}
|2=Gavialis browni{{extinct}} }}
|2=Gryposuchus colombianus{{extinct}} }}
|2=Ikanogavialis{{extinct}} }}
|2={{clade
|1=Gryposuchus pachakamue{{extinct}}
|2=Piscogavialis{{extinct}} }} }}
|2=Harpacochampsa{{extinct}} }}
|2={{clade
|1={{clade
|1=Toyotamaphimeia{{extinct}}
|2=Penghusuchus{{extinct}} }}
|2=Gavialosuchus{{extinct}} }} }}
|2={{clade
|1=Tomistoma lusitanicum{{extinct}}
|2=False gharial }} }}
|2=Tomistoma cairense{{extinct}} }}
|2=Dollosuchoides{{extinct}} }}
|2={{clade
|1=Maroccosuchus{{extinct}}
|2=Paratomistoma{{extinct}} }} }}
|2=Kentisuchus{{extinct}} }} }}

Distribution and habitat

The false gharial is native to Peninsular Malaysia and the islands of Borneo and Sumatra; it is locally extinct in Singapore, Vietnam and Thailand. It inhabits peat swamps and lowland swamp forests.BOOK, Bezuijen, M.R., Crocodiles. Status Survey and Conservation Action Plan, Shwedick, B.M., Sommerlad, R., Stevenson, C., Steubing, R.B., Crocodile Specialist Group, 2010, Manolis, S.C., Darwin, 133âˆ’138, Tomistoma Tomistoma schlegelii, Stevenson, C.,weblink Prior to the 1950s, Tomistoma occurred in freshwater ecosystems along the entire length of Sumatra east of the Barisan Mountains. The current distribution in eastern Sumatra has been reduced by 30-40% due to hunting, logging, fires, and agriculture.BOOK, Bezuijen, M.R., Crocodiles. Proceedings of the 14th Working Meeting of the Crocodile Specialist Group, Webb, G.J.W., Hartoyo, P., Samedi, Ramono, W.S., Manolis, S.C., 1998, IUCN. The World Conservation Union, Gland, Switzerland and Cambridge, UK, 10â€“31, The False Gharial (Tomistoma schlegelii) in Sumatra,weblink The population has been estimated to comprise less than 2,500 mature individuals as of 2010.

Ecology and behaviour

Diet

Until recently, very little was known about the diet or behaviour of the false gharial in the wild. Details are slowly being revealed. In the past, the false gharial was thought to have a diet of only fish and very small vertebrates, but more recent evidence indicates that it has a generalist diet despite its narrow snout. In addition to fish and smaller aquatic animals, mature adults prey on larger vertebrates, including proboscis monkeys, long-tailed macaques, deer, water birds, and reptiles. There is an eyewitness account of a false gharial attacking a cow in East Kalimantan.The false gharial may be considered an ecological equivalent to Neotropical crocodiles such as the Orinoco and American crocodiles, which both have slender snouts but a broad diet.

Reproduction

The false gharial is a mound-nester. Females lay small clutches of 13â€“35 eggs per nest and appear to produce the largest eggs of living crocodilians. They attain sexual maturity at a length of around {{cvt|2.5|to|3|m}}, which is large compared to other crocodilians.Courtship coincides with periods of rainfall in November to February and from April to June.

Conflict

In 2008, a 4-m female false gharial attacked and ate a fisherman in central Kalimantan; his remains were found in the gharial's stomach. This was the first verified fatal human attack by a false gharial.JOURNAL, Rachmawan, D., Brend, S., 2009, Human-Tomistoma interactions in central Kalimantan, Indonesian Borneo,weblink Crocodile Specialist Group Newsletter, 28, 1, 9â€“11, However, by 2012, at least two more verified fatal attacks on humans by false gharials had occurred indicating perhaps an increase of human-false gharial conflict possibly correlated to the decline of habitat, habitat quality, and natural prey numbers.BOOK, Sideleau, B., Crocodiles. Proceedings of the 21st Working Meeting of the IUCN-SSC Crocodile Specialist Group, Britton, A. R. C., IUCN Crocodile Specialist Group, 2012, Gland, Switzerland, 111â€“114, A preliminary analysis of worldwide crocodilian attacks,weblink

Threats

The false gharial is threatened by habitat loss in most of its range due to the drainage of freshwater swamps and conversion for commercial plantation of oil palms.It is also hunted for its skin and meat, and its eggs are often harvested for human consumption.Population surveys carried out in the mid 2000s indicated that the distribution of individuals is spotty and disconnected, with a risk of genetic isolation.JOURNAL, Stuebing, R. B., amp, Bezuijen, M. R., Auliya, M., Voris, H. K., 2006, The current and historic distribution of Tomistoma schlegelii (the False Gharial) (MÃ¼ller 1838) (Crocodylia, Reptilia)", The Raffles Bulletin of Zoology, 54, 1, 181â€“197, Some population units in unprotected areas do not bear viable breeding adults.JOURNAL, RÃ¶dder, D., amp, Engler, J.O., Bonke, R., Weinsheimer, F., Pertel, W., 2010, Fading of the last giants: an assessment of habitat availability of the Sunda gharial Tomistoma schlegelii and coverage with protected areas, Aquatic Conservation: Marine and Freshwater Ecosystems, 20, 6, 678â€“684,

Conservation

The false gharial is listed on CITES Appendix I.Steps have been taken by the Malaysian and Indonesian governments to prevent its extinction in the wild. There are reports of some populations rebounding in Indonesia, yet with this slight recovery, mostly irrational fears of attacks have surfaced amongst the local human population.

References

External links

Crocodile Specialist Group: WEB,weblink Tomistoma schlegelii, {{small|(132 KB)}}
Tomistoma Task Force {{Webarchive|url=https://web.archive.org/web/20170630014423weblink |date=2017-06-30 }}
Saint Louis Zoo: False gharial
weblink" title="web.archive.org/web/20170727064519weblink">ARKive Images
BBC News: 'Match-making' for rare male croc
weblink" title="web.archive.org/web/20170723054428weblink">The Orangutan Foundation research centre being used for critical research on false gharials

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