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110-397: The gharial ( Gavialis gangeticus ), also known as gavial or fish-eating crocodile , is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are 2.6 to 4.5 m (8 ft 6 in to 14 ft 9 in) long, and males 3 to 6 m (9 ft 10 in to 19 ft 8 in). Adult males have a distinct boss at the end of

220-464: A Latinizing of the Greek κροκόδειλος ( crocodeilos ), which means both lizard and Nile crocodile . Crocodylia, as coined by Wermuth, in regards to the genus Crocodylus appears to be derived from the ancient Greek κρόκη ( kroke )—meaning shingle or pebble—and δρîλος or δρεîλος ( dr(e)ilos ) for "worm". The name may refer to the animal's habit of resting on the pebbled shores of

330-475: A monotypic taxon . John Edward Gray reviewed zoological specimens in the collection of the Natural History Museum, London . He also considered the gharial monotypic in 1869. He placed it in the family Gavialidae together with the false gharial ( Tomistoma schlegelii ) because both have long, slender jaws and similar dentition. Gharialis hysudricus proposed by Richard Lydekker in 1886

440-415: A ribosomal segment of mitochondrial DNAs of gharial and false gharial revealed that they share 22 unique nucleotides , a similarity of 94%, supporting the view that they are sister taxa. Analyses of nuclear gene sequences of both species also support the view that they are sister taxa. Molecular genetics and tip dating studies indicates a genetic divergence between the gharial and false gharial in

550-840: A 4.9 m (16 ft) long gharial weighed around 560 kg (1,230 lb), while a 4.8 m (16 ft) long Nile crocodile weighed 680 kg (1,500 lb). The gharial once thrived in all the major river systems of the northern Indian subcontinent, from the Indus River in Pakistan , the Ganges in India, the Brahmaputra River in northeastern India and Bangladesh to the Irrawaddy River in Myanmar . In

660-414: A body length of at least 3 m (9 ft 10 in) and grow up to a length of 6 m (19 ft 8 in). Adult males weigh about 160 kg (350 lb) on average, but can reach a weight of up to 600 kg (1,300 lb). The gharial is among the largest living crocodilians, with the heaviest recorded male weighing 977 kg (2,154 lb). A 6.55 m (21 ft 6 in) long gharial

770-887: A broader prey base than the gharial including snakes , turtles , birds , mammals and dead animals. The gharial is well adapted to hunting fish underwater because of its sharp interlocking teeth and long narrow snout, which meets little resistance in the water. It does not chew its prey, but swallows it whole. Juvenile gharials were observed to jerk their heads back to manoeuvre fish into their gullets, sliding them in head first. Young gharials feed on insects , tadpoles , small fish and frogs . Adults also feed on small crustaceans . Remains of Indian softshell turtle ( Nilssonia gangetica ) were also found in gharial stomachs. Gharials tear apart large fish and pick up and swallow stones as gastroliths , probably to aid digestion or regulate buoyancy. Some gharial stomachs also contained jewellery. Stones weighing about 4.5 kg (10 lb) were found in

880-445: A crocodilian shut tight. All species have a palatal valve, a membranous flap of skin at the back of the oral cavity that protects the oesophagus and trachea when the animal is underwater. This enables them to open their mouths underwater without drowning. Crocodilians typically remain underwater for fifteen minutes or less at a time, but some can hold their breath for up to two hours under ideal conditions. The maximum diving depth

990-399: A different way from those of other reptiles, a feature they share with some early archosaurs. One of the upper row of ankle bones, the ankle bone , moves with the tibia and fibula , while the heel bone moves with the foot and is where the ankle joint is located. The result is that the legs can be held almost vertically beneath the body when on land, and the foot swings during locomotion as

1100-408: A form of taxidermy. The skin is removed from the animal's carcass, treated with absorbents, and filled with cotton or polyester batting (In the past plant fibres or sawdust were used). Bird specimens have a long, thin, wooden dowel wrapped in batting at their center. The dowel is often intentionally longer than the bird's body and exits at the animal's vent. This exposed dowel provides a place to handle

1210-581: A gharial's stomach that was shot in the Sharda River in 1910. Crocodilia Crocodylia ( / k r ɒ k ə ˈ d ɪ l i ə / ) is an order of semiaquatic , predatory reptiles known as crocodilians . They first appeared during the Late Cretaceous and are the closest living relatives of birds . Crocodilians are a type of crocodylomorph pseudosuchian , a subset of archosaurs that appeared about 235 million years ago and were

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1320-401: A higher surface-area-to-volume ratio . The kidneys and excretory system are much the same as in other reptiles, but crocodilians do not have a bladder . In fresh water, the osmolality (the concentration of solutes that contribute to a solution's osmotic pressure ) in the plasma is much higher than it is in the surrounding water. The animals are well-hydrated, and the urine in the cloaca

1430-459: A hissing sound that can be heard 75 m (246 ft) away. The gharial is the only living crocodilian with such visible sexual dimorphism . Mature male gharials have larger skulls than females, exceeding a basal length of 715 mm (28.1 in) and a width of 287 mm (11.3 in). Female gharials reach sexual maturity at a body length of 2.6 m (8 ft 6 in) and grow up to 4.5 m (14 ft 9 in). Males mature at

1540-408: A hollow bulbous nasal protuberance at the tip of the snout upon reaching sexual maturity . This protuberance resembles an earthen pot known locally as "ghara". The male's ghara starts growing over the nostrils at an age of 11.5 years and measures about 5 cm × 6 cm × 3.5 cm (2.0 in × 2.4 in × 1.4 in) at an age of 15.5 years. It enables the males to emit

1650-472: A largely carnivorous diet. Some species like the gharial are specialized feeders, while others like the saltwater crocodile have generalized diets. Crocodilians are generally solitary and territorial , though they sometimes hunt in groups. During the breeding season, dominant males try to monopolize available females. Females lay their eggs in holes or mounds, and similar to many birds, care for their hatched young. Some species of crocodilians (particularly

1760-454: A left and right aorta which are connected by a hole called the Foramen of Panizza . Like birds and mammals, crocodilians have separate vessels that direct blood flow to the lungs and the rest of the body respectively. They also have unique cog-teeth-like valves that, when interlocked, direct blood to the left aorta and away from the lungs, and then back around the body. This system may allow

1870-425: A more advanced level of specialization. Others suggested that it evolved much later than other crocodilians because of its low levels of blood protein divergence. As it shares this trait with the false gharial, it was suggested that they form a sister group . In contrast, it was suggested that the gharial and all the other crocodilians form a sister group as the structure of its tail muscles is unique. Sequencing of

1980-518: A more solid justification for one spelling over the other was proposed. Prior to 1988, Crocodilia was a group that encompassed the modern-day animals, as well as their more distant relatives now in the larger groups called Crocodylomorpha and Pseudosuchia . Under its current definition as a crown group (as opposed to a stem-based group ), Crocodylia is now restricted to only the last common ancestor of today's crocodilians and all of its descendants (living or extinct ). Crocodilia appears to be

2090-403: A much greater diversity of forms than modern crocodilians. Some became small fast-moving insectivores , others specialist fish-eaters , still others marine and terrestrial carnivores , and a few became herbivores . The earliest stage of crocodilian evolution was the protosuchians in the late Triassic and early Jurassic. They were followed by the mesosuchians , which diversified widely during

2200-457: A powerful bite. Like birds, crocodilians possess a four-chambered heart and lungs with unidirectional airflow. Like most other reptiles, they are ectotherms . Crocodilians are found mainly in the warmer and tropical areas of the Americas , Africa , Asia and Oceania . They usually inhabit freshwater habitats , but some can live in saltier environments and even swim out to sea. They have

2310-699: A role in the crushing of food. Digestion takes place more quickly at higher temperatures. When digesting a meal, CO2-rich blood towards the lungs is redirected to the stomach, supplying more acid for the oxyntic glands . Compared to crocodiles, alligators digest more carbohydrates relative to protein. Crocodilians have a very low metabolic rate and consequently, low energy requirements. They can withstand extended fasting, living on stored fat . Even recently hatched crocodiles are able to survive 58 days without food, losing 23% of their bodyweight during this time. Crocodilians are ectotherms , relying mostly on their environment to control their body temperature. The sun's heat

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2420-525: A single olfactory chamber and the vomeronasal organ disappears when they reach adulthood. Behavioural and olfactometer experiments indicate that crocodiles detect both air-borne and water-soluble chemicals and use their olfactory system for hunting. When above water, crocodiles enhance their ability to detect volatile odorants by gular pumping, a rhythmic movement of the floor of the pharynx . They appear to have lost their pineal organ , but still show signs of melatonin rhythms. The skin of crocodilians

2530-434: A suitable concentration of salt in body fluids. Osmoregulation is related to the quantity of salts and water exchanged with the environment. Intake of water and salts takes place across the lining of the mouth, when water is drunk, incidentally while feeding, and when present in foods. Water is lost during breathing, and both salts and water are lost in the urine and faeces, through the skin, and via salt-excreting glands on

2640-563: Is a more detailed cladogram that shows the gharial's proposed placement within Gavialidae , including extinct members: Gharial Gavialis bengawanicus † Gavialis browni † Gryposuchus colombianus † Ikanogavialis † Gryposuchus pachakamue † Piscogavialis † Harpacochampsa † Toyotamaphimeia † Penghusuchus † Gavialosuchus † Tomistoma lusitanicum † False gharial Tomistoma schlegelii The gharial

2750-516: Is a representative specimen of the animal used in a study, such as a specimen collected as part of an ecological survey or a specimen which was the source of DNA for a molecular study. Voucher specimens confirm the identity of the species referred to in the study. They are a backup against misidentification, changing species concepts which mislead results. Type specimens are a special type of voucher specimen used in taxonomy . Museum zoological specimens may have historic significance . For example,

2860-532: Is abundant and dilute, nitrogen being excreted as ammonium bicarbonate . Sodium loss is low and mainly takes place through the skin in freshwater conditions. In seawater, the opposite is true. The osmolality in the plasma is lower than the surrounding water, which is dehydrating for the animal. The cloacal urine is much more concentrated, white, and opaque, with the nitrogenous waste being mostly excreted as insoluble uric acid . Zoological specimen Bird and mammal specimens are conserved as dry study skins ,

2970-619: Is assumed to have happened close to the Permian–Triassic extinction event (informally known as the Great Dying). Crocodylomorpha , the group that later give rise to modern crocodilians, emerged in the Late Triassic . While the most basal crocodylomorphs were large, the ones that gave rise to crocodilians were small, slender, and leggy. This evolutionary grade, the so-called " sphenosuchians " first appeared around Carnian of

3080-521: Is called conchology as distinct from malacology (wet specimens). Most hard-bodied insect specimens and some other hard-bodied invertebrates such as certain Arachnida , are preserved as pinned specimens. Either while still fresh, or after rehydrating them if necessary because they had dried out, specimens are transfixed by special stainless steel entomological pins . As the insect dries the internal tissues solidify and, possibly aided to some extent by

3190-417: Is clad in non-overlapping scales known as scutes which are covered with in beta-keratin . Many of the scutes are strengthened by bony plates known as osteoderms . They are most numerous on the back and neck of the animal. The belly and underside of the tail possess rows of broad, flat and square-shaped scales. In between crocodilian scales are hinge areas which consist mainly of alpha-keratin . Underneath

3300-421: Is common for the dry material to greatly exceed the amount of material that is preserved in alcohol. The shells minus their soft parts are kept in card trays within drawers or in glass tubes, often as lots (a lot is a collection of a single species taken from a single locality on a single occasion). Shell collections sometimes suffer from Byne's disease which also affects birds eggs. The study of dry mollusc shells

3410-456: Is diversity in snout and tooth shape, all crocodilian species have essentially the same body morphology. They have solidly built lizard-like bodies with wide, cylindrical torsos, flat heads, long snouts, short necks and tails compressed from side-to-side. Their limbs are reduced in size; the front feet have five mostly non-webbed digits, and the hind feet have four webbed digits and an extra fifth. The pelvis and ribs of crocodilians are modified;

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3520-418: Is not fully understood, but it has been suggested that they may be mechanosensory organs. There are prominent paired integumentary glands in skin folds on the throat, and others in the side walls of the cloaca. Various functions for these have been suggested. They may play a part in communication, as indirect evidence suggest that they secrete pheromones used in courtship or nesting. The skin of crocodilians

3630-420: Is olive-coloured, with adults being darker than young, which have dark brown cross bands and speckles. Its back turns almost black at 20 years of age, but its belly is yellowish-white. It has four transverse rows of two scales on the neck, which continue along the back. Scutes on the head, neck and back form a single continuous plate composed of 21 to 22 transverse series, and four longitudinal series. Scutes on

3740-560: Is permanently erect and relies on cloacal muscles to protrude it out and elastic ligaments and a tendon to pull it back in. The gonads are located near the kidneys . Crocodilians range in size from the Paleosuchus and Osteolaemus species, which reach 1–1.5 m (3 ft 3 in – 4 ft 11 in), to the saltwater crocodile and Nile crocodile, which reach 6 m (20 ft) and weigh up to 1,000 kg (2,200 lb), though some prehistoric species such as

3850-507: Is the genus Borealosuchus of North America, with six species, though its phylogenetic position is not settled. The three primary branches of Crocodilia had diverged by the Late Cretaceous . The possible earliest-known members of the group may be Portugalosuchus and Zholsuchus from the Cenomanian - Turonian stages. The classification of Portugalosuchus has been disputed by some researchers who claimed that it may be outside

3960-416: Is the main means of warming for any crocodilian, while immersion in water may either raise its temperature via conduction , or cool the animal in hot weather. The main method for regulating its temperature is behavioural. Temperate-living alligators may start the day by basking in the sun on land, and move into the water for the afternoon, with parts of the back breaking the surface so it can still be warmed by

4070-407: Is the most thoroughly aquatic crocodilian. It leaves the water only for basking on riverbanks. Being cold-blooded, it seeks to cool down during hot times and to warm up when ambient temperature is cool. Gharials bask daily in the cold season, foremost in the mornings, and prefer sandy and moist beaches. They change their basking pattern with increasing daily temperatures; they start basking earlier in

4180-405: Is the place and date of collection, attached to the specimen by a label. Additional information is the name of the collector and the habitat. Tissue from specimens may be saved for genetic studies (molecular data, DNA ). Depending on the animal group , other data may be included, for instance in bird collections the bird’s breeding condition, weight, colours of its eyes, bills and legs and nature of

4290-449: Is to store the specimen in 70% ethanol with various additives after fixing with formalin or in these days sometimes with a salt-solution. Some methods are very useful, because the color can be preserved. (Salt-)Solutions like this are Jores, Kaiserling and Romhányi. Modern specimens are stored in borosilicate glass due to its chemical and thermal resistance and good optical clarity. Minimum data associated with zoological specimens

4400-443: Is tough and can withstand damage from conspecifics , and the immune system is effective enough to heal wounds within a few days. In the genus Crocodylus the skin contains chromatophores , allowing them to change color from dark to light and vice versa. The crocodilian has perhaps the most complex vertebrate circulatory system . It has a four-chambered heart and two ventricles , an unusual trait among extant reptiles, and both

4510-501: Is unknown, but crocodiles can dive to at least 20 m (66 ft). Vocalizing is produced by vibrating vocal folds in the larynx . The folds of the American alligator have a complex morphology consisting of epithelium , lamina propria and muscle, and according to Riede et al. (2015), "it is reasonable to expect species-specific morphologies in vocal folds/analogues as far back as basal reptiles". Crocodilian vocal folds lack

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4620-468: Is usually maintained between 25 and 35 °C (77 and 95 °F), and mainly stays in the range 30 to 33 °C (86 to 91 °F). Both the American and Chinese alligator can be found in areas that sometimes experience periods of frost in winter. In cold weather, they remain submerged with their tails in deeper, less cold water and their nostrils just projecting through the surface. If ice forms on

4730-799: The Eocene about 38  million years ago . The genus Gavialis probably originated in the region of India and Pakistan in the Early Miocene . Fossil gharial remains excavated in the Sivalik Hills of Haryana and Himachal Pradesh are dated to between the Pliocene and the Early Pleistocene . Fossil gharial remains were also found at two sites in the Ayeyarwady River valley in central Myanmar, which are dated to

4840-485: The Hindustani word ' ghara ' for an earthen pot, in reference to the nasal protuberance on the adult male's snout. It is also called 'gavial'. The name 'fish-eating crocodile' is a translation of its Bengali name 'mecho kumhir', with 'mecho' being derived from 'māch' meaning fish and 'kumhir' meaning crocodile. The name 'Indian gharial' has occasionally been used for gharial populations in India. Lacerta gangetica

4950-521: The IUCN Red List since 2007. The oldest known depictions of the gharial are about 4,000 years old and were found in the Indus Valley . Hindus regard it as the vehicle of the river deity Gaṅgā . Local people living near rivers attributed mystical and healing powers to the gharial, and used some of its body parts as ingredients of indigenous medicine . The name 'gharial' is derived from

5060-727: The Karnali – Babai River system in Bardia National Park and the Narayani –Rapti river system in Chitwan National Park . In spring 2017, the Babai River was surveyed using an unmanned aerial vehicle , which detected 33 gharials on a stretch of 102 km (63 mi). In India, gharial populations are present in the: Between 1979 and 1993, less than 20 individuals were sighted in the upper reaches of

5170-717: The Late Pleistocene . During the Quaternary , Gavialis dispersed as far as Java via the Siva– Malayan route, which did not require saltwater crossings. Fossil remains of Gavialis bengawanicus found on Java were dated to the Early Pleistocene. G. bengawanicus fossils found in Thailand's Nakhon Ratchasima Province support the hypothesis of gharial dispersal through riverine systems. It represents

5280-533: The Late Triassic . They ate small, fast prey and survived into the Late Jurassic . As the Triassic ended, crocodylomorphs became the only surviving pseudosuchians. During the early Jurassic period, the dinosaurs became dominant on land, and the crocodylomorphs underwent major adaptive diversifications to fill ecological niches vacated by recently extinguished groups. Mesozoic crocodylomorphs had

5390-722: The Nile . Crocodilians, and birds, are members of the Archosaur clade. Archosaurs are distinguished from other reptiles particularly by two sets of extra openings in the skull: the antorbital fenestra located in front of the animal's eye socket and the mandibular fenestra on the jaw. Archosaurs comprise two main groups: the Pseudosuchia (crocodilians and their relatives), and the Avemetatarsalia ( dinosaurs , pterosaurs , and their relatives). The split between these two

5500-516: The Nile crocodile ) are known to have attacked humans . Humans are the greatest threat to crocodilian populations through activities that include hunting, poaching, and habitat destruction , but farming of crocodilians has greatly reduced unlawful trading in wild skins. Artistic and literary representations of crocodilians have appeared in human cultures around the world since Ancient Egypt . "Crocodilia" and "Crocodylia" have been used interchangeably for decades starting with Schmidt's redescription of

5610-520: The Santonian - Campanian stages, while definitive longirostres first appeared during the Maastrichtian stage. The earliest known alligatoroids and gavialoids include highly derived forms, which indicates that the time of the actual divergence between the three lineages must have been a pre-Campanian event. Additionally, scientists conclude that environmental factors played a major role in

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5720-409: The cartilaginous processes of the ribs allow the thorax to collapse when submerging and the structure of the pelvis can accommodate large amounts of food, or more air in the lungs. Both sexes have a cloaca , a single chamber and outlet near the tail into which the intestinal , urinary and genital tracts open. It houses the penis in males and the clitoris in females. The crocodilian penis

5830-442: The eardrums are protected by flaps that can be opened or closed by muscles. Crocodilians have a wide hearing range , with sensitivity comparable to most birds and many mammals. Hearing in crocodilians does not degrade as the animal gets older as they can regrow and replace hair cells . The well-developed trigeminal nerve allows them to detect vibrations in the water (such as those made by potential prey). Crocodilians have just

5940-467: The mugger crocodile ( Crocodylus palustris ) in parts of its range. They use the same nesting grounds, but differ in the selection of basking sites. The gharial basks close to water on shallow, sandy beaches and lays eggs only in sandy soil near water. The mugger crocodile also basks on sandy beaches, but unlike the gharial climbs steep embankments and rocks, and moves farther away from beaches for both basking and nest building. It also preys on fish, but has

6050-529: The pancreas , spleen , small intestine , and liver also function more efficiently. When submerged, a crocodilian's heart may beat at only one or two beats a minute, with little blood flow to the muscle. When it rises and takes a breath, its heart rate almost immediately speeds up, and the muscles receive newly oxygenated blood. Unlike many marine mammals , crocodilians have little myoglobin to store oxygen in their muscles. During diving, an increasing concentration of bicarbonate ions causes haemoglobin in

6160-454: The secondary palate was little developed as it consisted only of a maxilla . The mesosuchians saw a fusion of the palatine bones to the secondary palate and a great extension of the nasal passages behind the palatine and in front of the pterygoid bones . This allowed the animal to breathe through its nostrils while its mouth was open underwater. The eusuchians continued this process with the interior nostrils now opening through an aperture in

6270-409: The 1930s and is limited to only 2% of its historical range today. Conservation programmes initiated in India and Nepal focused on reintroducing captive-bred gharials since the early 1980s. Loss of habitat because of sand mining and conversion to agriculture, depletion of fish resources and detrimental fishing methods continue to threaten the population. It has been listed as critically endangered on

6380-827: The 1940s, it was numerous in the Barak River in Assam , which held big fish at the time including golden mahseer ( Tor putitora ). A few individuals were also sighted in tributaries of the Barak River in Assam, Mizoram and Manipur up to 1988, but surveys were not carried out. In 1927, a gharial was shot in the Shweli River in Myanmar, a tributary of the Ayeyawady River. This is the only authenticated record in

6490-530: The 23rd or 24th tooth. The snout of adult gharials is 3.5 times longer than the width of the skull's base. Because of this long snout the gharial is especially adapted to catching and eating fish. The nasal bones are rather short and widely spaced from the premaxillae . The jugal bone is raised. It becomes proportionally thicker with age. Two individuals in the weight range of 103–121 kg (227–267 lb) had an average measured bite force of 1,784–2,006  N (401–451  lb f ). Male gharials develop

6600-691: The Brahmaputra River between Kaziranga National Park and Dibru-Saikhowa National Park . This population had declined due to commercial fishing, poaching , encroachment by local people in gharial breeding grounds and siltation of river beds following deforestation . In 1998, it was not considered to be viable. About 30 gharials were observed in small lakes and tributaries of the Brahmaputra River in Assam between 2004 and 2007. In Bangladesh, gharials were recorded in Padma , Jamuna , Mahananda and Brahmaputra rivers between 2000 and 2015. The gharial

6710-599: The Jurassic and the Tertiary. The eusuchians first appeared during the Early Cretaceous , and includes modern crocodilians. Protosuchians were small, mostly terrestrial animals with short snouts and long limbs. They had bony armor in the form of two rows of plates extending from head to tail; this armor would still be found in later species. Their vertebrae were convex on the two main articulating surfaces, and

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6820-428: The animal needs to stop or steer in a different direction, the limbs are splayed out. Swimming is normally achieved with gentle sinuous movements of the tail, but they can move faster when pursuing or being pursued. Crocodilians are less well-adapted for moving on land, and are unusual among vertebrates in having two different means of terrestrial locomotion: the "high walk" and the "low walk". Their ankle joints flex in

6930-462: The animals to remain submerged for a longer period, but this explanation has been questioned. Other possible reasons for the peculiar circulatory system include assistance with thermoregulatory needs, prevention of pulmonary oedema , or faster recovery from metabolic acidosis . Retaining carbon dioxide within the body permits an increase in the rate of gastric acid secretion and thus the efficiency of digestion, and other gastrointestinal organs such as

7040-403: The ankle rotates. The limbs move much the same as in other quadrupeds , with the left forelimb moving first, followed by the right hindlimb, then right forelimb, and finally left hindlimb, and repeat. The high walk of crocodilians, with the belly and most of the tail held off the ground and the limbs held directly under the bodies, resembles that of mammals and birds. The low walk is similar to

7150-461: The back are bony, but softer and feebly keeled on the sides. The outer edges of the forearms, legs, and feet have crests jutting out; fingers and toes are partly webbed. Its snout is very long and narrow, widened at the end, and with 27 to 29 upper teeth and 25 or 26 lower teeth on each side. The front teeth are the largest. The first, second, and third lower jaw teeth fit into spaces in the upper jaw. The extremely long mandibular symphysis extends to

7260-443: The belly outward, and the diaphragmaticus pulls the liver back. When exhaling, the internal intercostal muscles push the ribs inward, while the rectus abdominis pulls the hips and liver forwards and the belly inward. Crocodilians can also use these muscles to adjust the position of their lungs, controlling their buoyancy in the water. An animal sinks when the lungs are pulled towards the tail and floats when they move back towards

7370-623: The bird without disturbing the feathers. Mammal study skins do not normally utilize wooden dowels, instead preparators use wire to support the legs and tail of mammals. Labels are attached to a leg of the specimen with thread or string. Heat and chemicals are sometimes used to aid the drying of study skins. Osteological collections consist of cleaned, complete and partial skeletons, crania of Vertebrates , mainly birds and mammals. They are used in studies of comparative anatomy and to identify bones from archaeological sites. Human bones are used in medical and forensic studies. In museum collections it

7480-404: The blood from the calcium and magnesium in these dermal bones act as a buffer during prolonged submersion when increasing levels of carbon dioxide would otherwise cause acidosis . Some scutes contain a single pore known as an integumentary sense organ. Crocodiles and gharials have these on large parts of their bodies, while alligators and caimans only have them on the head. Their exact function

7590-604: The blood to release oxygen for the muscles. Crocodilians were traditionally thought to breathe like mammals, with airflow moving in and out tidally, but studies published in 2010 and 2013 conclude that crocodilians breathe more like birds , with airflow moving in a unidirectional loop within the lungs. When a crocodilian inhales, air flows through the trachea and into two primary bronchi , or airways, which split off into narrower secondary passageways. The air continues to move through these, then into even narrower tertiary airways, and then into other secondary airways which were bypassed

7700-626: The country attesting the survival of gharials into the 20th century. Whether gharials still live in the Shweli River today is possible but remained unclear in 2012. By 1976, its global range had decreased to only 2% of its historical range, and fewer than 200 gharials were estimated to survive. It is locally extinct in Pakistan, Bhutan and Myanmar. Since the early 1980s, the population has been reinforced with captive-bred gharials that were released into wild habitats in India and Nepal. In 2017,

7810-496: The crown group crocodilians. The morphology-based phylogenetic analyses based on the new neuroanatomical data obtained from its skull using micro-CT scans suggested that this taxon is a crown group crocodilian and a member of the 'thoracosaurs', recovered as a sister taxon of Thoracosaurus within Gavialoidea, though it is uncertain whether 'thoracosaurs' were true gavialoids. Definitive alligatoroids first appeared during

7920-572: The early 20th century, it was considered common in the Indus River and its Punjabi tributaries. By the early 1980s, it was almost extinct in the Indus. During surveys in 2008 and 2009, no gharial was sighted in the river. It was also present in India's Godavari River but was hunted to extinction between the late 1940s and the 1960s. It was considered extinct in the Koshi River since 1970. In

8030-485: The elasticity of mammalian ones; but the larynx is still capable of complex motor control similar to birds and mammals and can adequately control its fundamental frequency . Crocodilian teeth can only hold onto prey, and food is swallowed unchewed. The stomach consists of a grinding gizzard and a digestive chamber. Indigestible items are regurgitated as pellets. The stomach is more acidic than that of any other vertebrate and contains ridges for gastroliths , which play

8140-494: The evolution of crocodilians and their ancestors, with warmer climate being associated with high evolutionary rates and large body sizes. Crocodylia is cladistically defined as the last common ancestor of Gavialis gangeticus (the gharial ), Alligator mississippiensis ( American alligator ), and Crocodylus rhombifer (the Cuban crocodile ) and all of its descendants. The phylogenetic relationships of crocodilians has been

8250-596: The eye clean. When a crocodilian leaves the water and dries off, this substance is visible as "tears". While eyesight is fairly good in air, it is significantly weakened underwater. Crocodilians appear to have gone through a "nocturnal bottleneck" early in their history with their eyes losing traits like sclerotic rings , an annular pad of the lens and colored cone oil droplets , giving them dichromatic vision (red-green colorblindness). Since then, some crocodilians appear to have re-evolved full colour vision . The ears are adapted for hearing both in air and underwater, and

8360-478: The family Crocodilini. Rhamphostoma was proposed by Johann Georg Wagler in 1830 who considered this genus to contain two species, Crocodilus gangeticus and C. tenuirostris . The family name Gavialidae was proposed by Arthur Adams in 1854 with Gavialis as the only genus in this family. Gavialis gangetica was the scientific name used by Albert Günther in 1864 who considered L. gangetica , C. longirostris and C. tenuirostris as synonyms and Gavialis

8470-413: The first time. The air then flows back into the primary airways and is exhaled. The lungs of crocodilians are attached to the liver and the pelvis by the diaphragmaticus muscle ( analogous of the diaphragm in mammals). During inhalation, the external intercostal muscles expand the ribs, allowing the animal to take in more air, while the ischiopubis muscle causes the hips to swing downwards and push

8580-454: The global population was estimated to comprise at maximum 900 individuals, including about 600 mature adults in six major subpopulations along 1,100 km (680 mi) of river courses and another 50 mature adults in eight minor subpopulations along 1,200 km (750 mi) of river courses. In Nepal, small populations are present and slowly recovering in tributaries of the Ganges, such as

8690-443: The group from the formerly defunct term Loricata . Schmidt used the older term "Crocodilia", based on Owen 's original name for the group. Wermuth opted for "Crocodylia" as the proper name, basing it on the type genus Crocodylus ( Laurenti , 1768). Dundee—in a revision of many reptilian and amphibian names—argued strongly for "Crocodylia". However, it was not until the advent of cladistics and phylogenetic nomenclature that

8800-409: The head. This allows them to move through the water without creating disturbances that could alert potential prey. They can also spin and twist by moving their lungs laterally. Swimming and diving crocodilians appear to rely on lung volume more for buoyancy than oxygen storage. Just before diving, the animal exhales to reduce its lung volume and reach negative buoyancy. When diving, the nostrils of

8910-488: The high walk, but without the body being raised, and is quite different from the sprawling walk of salamanders and lizards. The animal can change from one walk to the other instantaneously, but the high walk is the usual means of locomotion on land. The animal may push its body up and use this form immediately, or may take one or two strides of low walk before raising the body higher. Unlike most other land vertebrates, when crocodilians increase their pace of travel they increase

9020-459: The hind limbs launching the body forward and the fore limbs subsequently taking the weight. Next, the hind limbs swing forward as the spine flexes dorso-ventrally , and this sequence of movements is repeated. During terrestrial locomotion, a crocodilian can keep its back and tail straight, since the scales are attached to the vertebrae by muscles. Whether on land or in water, crocodilians can jump or leap by pressing their tails and hind limbs against

9130-435: The integument, they grip the pin and secure the specimen in place on the pin. Very small, delicate specimens may instead be secured by fine steel points driven into slips of card, or glued to card points or similar attachments that in turn are pinned in the same way as entire mounted insects. The pins offer a means of handling the specimens without damage, and they also bear labels for descriptive and reference data. Once dried,

9240-554: The jaws are closed as their teeth fit into grooves along the outside lining of the upper jaw. By contrast the lower teeth of alligators and caimans normally fit into holes along the inside lining of the upper jaw. Thus they are hidden when the jaws are closed. Crocodilians are homodonts , meaning each of their teeth are all of the same type (they do not possess different tooth types, such as canines and molars) and polyphyodonts are able to replace each of their approximately 80 teeth up to 50 times in their 35- to 75-year lifespan. They are

9350-436: The jaws are larger and more powerful than the ones that open them, and a crocodilian's jaws can be held shut by a person fairly easily. Conversely, the jaws are extremely difficult to pry open. The powerful closing muscles attach at the middle of the lower jaw and the jaw hinge attaches behind the atlanto-occipital joint , giving the animal a wide gape. A folded membrane holds the tongue stationary. Crocodilians have some of

9460-425: The late Cretaceous Deinosuchus were even larger at up to about 11 m (36 ft) and 3,450 kg (7,610 lb). They tend to be sexually dimorphic , with males much larger than females. Crocodilians are excellent swimmers. During aquatic locomotion , the muscular tail undulates from side to side to drive the animal through the water while the limbs are held close to the body to reduce drag . When

9570-699: The long-snouted gavialids more closely related to crocodiles than to alligators, with the new grouping of gavialids and crocodiles named Longirostres . Below is a cladogram from 2021 showing the relationships of the major extant crocodilian groups. This analysis was based off mitochondrial DNA , including that of the recently extinct Voay robustus : Caiman [REDACTED] Melanosuchus [REDACTED] Paleosuchus [REDACTED] Alligator [REDACTED] Crocodylus [REDACTED] † Voay Mecistops [REDACTED] Osteolaemus [REDACTED] Gavialis [REDACTED] Tomistoma [REDACTED] Though there

9680-498: The mornings, move back into the river when it is hot, and return to the beach later in the afternoon. Groups comprising an adult male, several females and subadults have been observed to bask together. Adult males dominate groups and tolerate immature males. Large groups of young, subadult and adult gharials form in December and January to bask. Adult males and females associate by mid February. The gharial shares riverine habitat with

9790-456: The only non-mammalian vertebrates with tooth sockets . Next to each full-grown tooth there is a small replacement tooth and an odontogenic stem cell in the dental lamina , which can be activated when required. Tooth replacement slows and eventually stops as the animal ages. The eyes, ears and nostrils of crocodilians are at the top of the head. This allows them to stalk their prey with most of their bodies underwater. When in bright light,

9900-507: The only survivors of the Triassic–Jurassic extinction event . The order includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae ), and the gharial and false gharial (family Gavialidae ). Although the term "crocodiles" is sometimes used to refer to all of these, it is less ambiguous to use "crocodilians". Extant crocodilians have long flat heads with long snouts and tails compressed on

10010-613: The only valid extinct Gavialis species. The below cladogram of the major extant crocodile groups is based on the latest molecular studies and shows the gharial's close relationship to the false gharial, and how the gavialids and crocodiles are more closely related than the alligatoroids : Caiman [REDACTED] Melanosuchus [REDACTED] Paleosuchus [REDACTED] Alligator [REDACTED] Crocodylus [REDACTED] Mecistops [REDACTED] Osteolaemus [REDACTED] Gavialis [REDACTED] Tomistoma [REDACTED] Here

10120-560: The pinned specimens directly in larger trays or drawers that are glass-topped and stored in cabinets. In contrast to such dried specimens, soft-bodied specimens most commonly are kept in "wet collections", meaning that they are stored in alcohol or similar preservative or fixative liquids, according to the intended function. Small specimens, whether hard or soft bodied, and whether entire, dissected , or sectioned , may be stored as microscope slide preparations. "Wet" specimen collections are stored in different solutions. A very old method

10230-619: The plains of the northern part of the Indian subcontinent. It is the most thoroughly aquatic crocodilian, and leaves the water only for basking and building nests on moist sandbanks. Adults mate at the end of the cold season. Females congregate in spring to dig nests, in which they lay 20–95 eggs. They guard the nests and the young, which hatch before the onset of the monsoon . The hatchlings stay and forage in shallow water during their first year, but move to sites with deeper water as they grow. The wild gharial population has declined drastically since

10340-694: The pterygoid bones. The vertebrae of eusuchians had one convex and one concave articulating surface. The oldest known eusuchian is Hylaeochampsa vectiana from the Early Cretaceous of the Isle of Wight in the United Kingdom. It was followed by crocodilians such as the Planocraniidae , the so-called 'hoofed crocodiles', in the Palaeogene . Spanning the Cretaceous and Palaeogene periods

10450-401: The pupils of a crocodilian contract into narrow slits, whereas in darkness they become large circles. This is typical for animals that hunt at night. Crocodilians also possess a tapetum lucidum which enhances vision in low light. When the animal completely submerges, the nictitating membranes cover its eyes. In addition, glands on the nictitating membrane secrete a salty lubricant that keeps

10560-564: The sides, with their eyes, ears, and nostrils at the top of the head. Alligators and caimans tend to have broader U-shaped jaws, that when closed, only show the upper teeth, while crocodiles usually have narrower V-shaped jaws with both rows of teeth visible when closed. Gharials have extremely slender and elongated jaws. All crocodilians are good swimmers and can move on land in a "high walk" position, traveling with their legs erect rather than sprawling. Crocodilians have thick skin covered in non-overlapping scales. They have conical, peg-like teeth and

10670-487: The snout, which resembles an earthenware pot known as a ghara , hence the name "gharial". The gharial is well adapted to catching fish because of its long, narrow snout and 110 sharp, interlocking teeth. The gharial probably evolved in the northern Indian subcontinent . Fossil gharial remains were excavated in Pliocene deposits in the Sivalik Hills and the Narmada River valley. It currently inhabits rivers in

10780-512: The specimens may be kept in conveniently sized open trays. The bottoms of the trays are lined with a material suited to receiving and holding entomological pins securely and conveniently. Cork and foam plastics are convenient examples. However, open trays are very vulnerable to attack by museum beetle and similar pests, so such open trays are stored in turn inside glass-topped, insect-proof drawers, commonly protected by suitable pesticides or repellents or barriers. Alternatively, some museums store

10890-424: The speed at which the lower half of each limb (rather than the whole leg) swings forward, so stride length increases while stride duration decreases. Though typically slow on land, crocodilians can produce brief bursts of speed, and some can run at 12 to 14 km/h (7.5 to 8.7 mph) for short distances. In some small species such as the freshwater crocodile , a running can progress to galloping. This involves

11000-415: The stomach contents. A single specimen may be a composite of preparations sharing a unique number. An example would be a vertebrate with an alcohol-preserved skin and viscera, a cleared and stained head, the post-cranial dried skeleton, histological , glass slides of various organs, and frozen tissue samples. This specimen could also be a voucher for a publication, or photographs and audiotape. A voucher

11110-868: The strongest bite forces in the animal kingdom. In a study published in 2003, an American alligator's bite force was measured at up to 2,125 lbf (9.45 kN). In a 2012 study, a saltwater crocodile's bite force was measured even higher, at 3,700 lbf (16 kN). This study also found no correlation between bite force and snout shape. Nevertheless, the gharial's extremely slender jaws are relatively weak and built more for quick jaw closure. The bite force of Deinosuchus may have measured 23,000 lbf (100 kN), even greater than that of theropod dinosaurs like Tyrannosaurus . Crocodilian teeth vary from dull and rounded to sharp and pointy. Broad-snouted species have teeth that vary in size, while those of slender-snouted species are more consistent. In general both rows of teeth are visible on crocodiles and gharials when

11220-585: The subject of debate and conflicting results. Many studies and their resulting cladograms , or "family trees" of crocodilians, have found the "short-snouted" families of Crocodylidae and Alligatoridae to be close relatives, with the long-snouted Gavialidae as a divergent branch of the tree. The resulting group of short-snouted species, named Brevirostres , was supported mainly by morphological studies which analyzed skeletal features alone. However, recent molecular studies using DNA sequencing of living crocodilians have rejected this distinct group Brevirostres, with

11330-450: The substrate and launching themselves into the air. A fast entry into water from a muddy bank can be effected by plunging to the ground, twisting the body from side to side and splaying out the limbs. The snout shape of crocodilians varies between species. Alligators and caimans generally have wider, U-shaped snouts while those of crocodiles are typically narrower and V-shaped. The gharial's are extremely elongated. The muscles that close

11440-406: The sun. At night it remains submerged, and its temperature slowly falls. The basking period is longer in winter. Tropical crocodiles bask briefly in the morning but then move into the water for rest of the day. They may also move to land at nightfall, as it is cooler. Gaping with the mouth can provide cooling by evaporation from the mouth lining. By these means, the temperature range of crocodilians

11550-463: The surface, the dermis is thick with collagen . Both the head and jaws lack actual scales and are instead covered in tight keratinised skin that is fused directly to the bones of the skull and which over time develop a pattern of cracks as the skull develops. The skin on the neck and sides is loose. The scutes contain blood vessels and may act to absorb or release heat during thermoregulation . Research also suggests that alkaline ions released into

11660-415: The tongue, though these are only present in crocodiles and gharials. The skin is a largely effective barrier to both water and ions, and gaping causes water loss by evaporation. Large animals are better able to maintain homeostasis at times of osmotic stress than smaller ones. Newly hatched crocodilians are much less tolerant of exposure to salt water than are older juveniles, presumably because they have

11770-419: The water, they maintain ice-free breathing holes, and there have been occasions when their snouts have become frozen into the ice. Temperature sensing probes implanted in wild American alligators have found that their core body temperatures can descend to around 5 °C (41 °F), but as long as they remain able to breathe they show no ill effects when the weather warms up. All crocodilians need to maintain

11880-465: Was based on a fossil skull from the Sivalik Hills that was larger than gharial fossil skulls known at the time. This name is considered to be a junior synonym of Gavialis gangeticus . The evolution of the gharial and its relationship with and divergence from other crocodilians have been a subject of controversy. Some authors assumed that the gharial evolved earlier than the other crocodilians because of its distinct skull shape and dentition, indicating

11990-575: Was claimed to have been killed in the Ghaghara River in Faizabad in August 1920, though no reliable measurements were taken. Male gharials with an alleged length of 7.16 to 9.14 m (23 ft 6 in – 30 ft 0 in) were sighted around the turn of the 20th century in Indian rivers. Overall, the gharial is less massive when compared to other crocodilians of similar length;

12100-442: Was the scientific name proposed by Johann Friedrich Gmelin in 1789. Gmelin followed Carl Linnaeus who proposed Lacerta in 1758 to include other crocodiles and various lizards known at the time. The gharial was placed in the genus Crocodilus by subsequent naturalists: The generic name Gavialis was proposed by Nicolaus Michael Oppel in 1811 for crocodiles with a cylindrical-shaped back. He placed this genus in

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