Whale shark

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Whale shark Fossil range: 60–0 Ma PreЄ Є O S D C P T J K Pg N [1]
Whale shark from Taiwan in the Georgia Aquarium Size comparison against an average human
Conservation status
Vulnerable (IUCN 2.3)[2]
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Orectolobiformes Family: Rhincodontidae (Müller and Henle, 1839) Genus: Rhincodon Smith, 1829 Species: R. typus
Binomial name
Rhincodon typus (Smith, 1828)
Range of whale shark

The whale shark, Rhincodon typus, is a slow moving filter feeding shark that is the largest living fish species. It can grow up to 18 meters (60 ft) in length and can weigh up to 13.6 tonnes (15 short tons). This distinctively-marked shark is the only member of its genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before 1984), which is grouped into the subclass Elasmobranchii in the class Chondrichthyes. The shark is found in tropical and warm oceans and lives in the open sea and can live for about 70 years.^[3] The species is believed to have originated about 60 million years ago. Although whale sharks have very large mouths, they feed mainly, though not exclusively, on plankton, microscopic plants and animals (a whale shark was observed feeding on a school of small fish in the BBC program Planet Earth).^[1]

Contents [hide] 1 Naming 2 Distribution and habitat 3 Anatomy and appearance 4 Diet 5 Behavior toward divers 6 Reproduction 7 Conservation status 8 Whale sharks in captivity 9 See also 10 References 11 External links

[edit] Naming

The species was identified in April 1828 following the harpooning of a 4.6-metre (15.1 ft) specimen in Table Bay, South Africa. It was described the following year by Andrew Smith, a military doctor associated with British troops stationed in Cape Town.^[4] He proceeded to publish a more detailed description of the species in 1849. The name "whale shark" comes from the fish's physiology; that is, a shark as large as a whale that shares a similar filter feeder eating mode. Known as a deity in a Vietnamese religion, the whale shark is called "Ca Ong", which literally translates as "Sir Fish". In Mexico, and throughout much of Latin America, the whale shark is known as "pez dama" or "domino" for its patterns of spots. Whale sharks go by the name of "Sapodilla Tom" in Belize due to the regularity of sightings near the Sapodilla Cayes on the Belize Barrier Reef. In Africa, the names for the whale shark are very evocative: "papa shillingi" in Kenya came about as it is believed that God threw shillings upon the shark which are now its spots, and in Madagascar whale sharks are known locally as "marokintana" which means "many stars". In Indonesia, the Javanese also reference the stars by calling it "geger lintang," meaning, "stars in the back". In the Philippines, it is called "butanding".

[edit] Distribution and habitat

The whale shark inhabits the world's tropic and warm-temperate seas. While thought to be primarily pelagic, seasonal feeding aggregations of the sharks occur at several coastal cities such as Gladden Spit in Belize; Ningaloo Reef in Western Australia; Útila in Honduras; Donsol, Pasacao and Batangas in the Philippines; off Isla Mujeres and Isla Holbox in Yucatan Mexico; Ujung Kulon National Park in Indonesia; Nosy Be in Madagascar Off Tofo Reef in Mozambique, and the Tanzanian islands of Mafia, Pemba and Zanzibar. Although it is often seen offshore, it has also been found closer to shore, entering lagoons or coral atolls, and near the mouths of estuaries and rivers. Its range is generally restricted to about ±30 ° latitude. It is capable of diving to depths of 700 metres (2,300 ft), and is migratory.^[3]

[edit] Anatomy and appearance

As a filter feeder it has a capacious mouth which can be up to 1.5 metres (4.9 ft) wide and can contain between 300 and 350 rows of tiny teeth.^[5] It has five large pairs of gills. Two small eyes are located towards the front of the shark's wide, flat head. The body is mostly grey with a white belly; three prominent ridges run along each side of the animal and the skin is marked with a "checkerboard" of pale yellow spots and stripes. These spots are unique to each whale shark and because of this they can be used to identify each animal and hence make an accurate population count. Its skin can be up to 10 centimetres (3.9 in) thick. The shark has a pair each of dorsal fins and pectoral fins. A juvenile whale shark's tail has a larger upper fin than lower fin while the adult tail becomes semi-lunate (or crescent-shaped). The whale shark's spiracles are just behind the eyes.

Whale shark in main tank at Osaka Aquarium.

The whale shark is not an efficient swimmer since the entire body is used for swimming, which is unusual for fish and contributes to an average speed of only around 5-kilometre-per-hour (3.1 mph). The largest specimen regarded as accurately recorded was caught on November 11, 1947, near the island of Baba, not far from Karachi, Pakistan. It was 12.65 metres (41.50 ft) long, weighed more than 21.5 tonnes (47,300 lb), and had a girth of 7 metres (23.0 ft).^[6] Stories exist of vastly larger specimens—quoted lengths of 18 metres (59 ft) are not uncommon in the popular shark literature—but no scientific records exist to support their existence. In 1868 the Irish natural scientist Edward Perceval Wright spent time in the Seychelles, during which he managed to obtain several small whale shark specimens, but claimed to have observed specimens in excess of 15 metres (49.2 ft), and tells of reports of specimens surpassing 21 metres (68.9 ft).

In a 1925 publication, Hugh M. Smith describes a huge whale shark caught in a bamboo fish trap in Thailand in 1919. The shark was too heavy to pull ashore, but Smith estimated that the shark was at least 17 metres (56 ft) long, and weighed approximately 37 tonnes (81,500 lb), which have been exaggerated to a more precise measurement of 17.98 metres (58.99 ft) and weight 43 tonnes in recent years. A shark caught in 1994 near Tainan County in Southern Taiwan is reported to have weighed 35.8 tonnes (78,887 lb).^[7] There have even been claims of whale sharks of up to 23 metres (75 ft). In 1934 a ship named the Maurguani came across a whale shark in the Southern Pacific Ocean, rammed it, and the shark consequently became stuck on the prow of the ship, supposedly with 4.6 metres (15.1 ft) on one side and 12.2 metres (40.0 ft) on the other.^[8] No reliable documentation exists of those claims and they remain little more than "fish-stories".

Ichthyornis

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Ichthyornis Fossil range: 93.5–75 Ma PreЄ Є O S D C P T J K Pg N Late Cretaceous
Ichthyornis dispar
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves (unranked): Carinatae Subclass: Ichthyornithes Order: Ichthyornithiformes Fürbringer, 1888 Family: Ichthyornithidae Marsh, 1873 Genus: Ichthyornis Marsh, 1872 Species: I. dispar
Binomial name
Ichthyornis dispar Marsh, 1872
Synonyms
see article text

Ichthyornis is a genus of seabird from the Late Cretaceous of North America. Its fossil remains are known from the (Turonian-Middle Campanian, 93.5-75 mya) chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway; some fossils from other locations like Argentina and Central Asia are sometimes referred to this taxon.

It is thought that Ichthyornis was the Cretaceous ecological equivalent of modern seabirds such as gulls, petrels, and skimmers. At 60 cm (2 ft), it was the size of a gull.

Although the wings and breastbone are very modern in appearance (suggesting strong flight ability and placing it with modern birds in the Carinatae), the jaws had numerous small, sharp teeth. Unlike earlier birds such as Enantiornithes, it appears to have matured to adulthood in a rather short, continuous process.^[1]

Ichthyornis was first discovered in 1870, by Benjamin Franklin Mudge. Othniel Charles Marsh's 1880 monograph on "Odontornithes" remains the most important general reference on this animal.

The fossil material is known to contain bones of immature individuals.^[1] It has not been thoroughly analyzed according to ontogenetical size differences, as destruction of the fossils would be necessary.

[edit] Systematics

Replica of Ichthyornis skeleton at Yale's Peabody Museum of Natural History. See Clarke (2004) for details.

Ichthyornis skeleton restoration by O.C. Marsh

Ichthyornis is close to the ancestry of modern birds, the Neornithes, but represents an independent lineage. It was long believed that it was closely related to some other Cretaceous taxa known from very fragmentary remains — Ambiortus, Apatornis (including the now separated Iaceornis) and Guildavis — but these seem to be closer still to the ancestors of modern birds. New data on the radiation of the latter, which is now known to have started already in the Cretaceous (see Vegavis), could shed more light on the exact relationship of these taxa. To agree with the 2004 review,^[2] the former order Ichthyornithiformes and the family Ichthyornithidae are now superseded by the subclass Ichthyornithes, which in the paper was also defined according to phylogenetic taxonomy.

There has been considerable confusion about the attribution of the fossil material.^[2] The similarity of the lower jaw and teeth to those of mosasaurs (fish-eating marine lizards) is so great that as late as 1952, it was argued that it really belonged to a diminutive species or young individual of or related to the genus Clidastes (Gregory, 1952); it was described as Colonosaurus mudgei.

Of the several described species, only one, Ichthyornis dispar, is currently recognized, following the seminal review by Julia Clarke.^[2] It is, however, entirely possible that several species have once existed, given the large spatial and temporal range over which fossils have been found. Many bird species show little difference in their skeletons, and the Ichthyornis material comes from a wide range of strata, so possibly more than one species existed, the bauplan being so successful as to change little in morphology.

The presumed "Ichthyornis" lentus actually belongs into the early galliform genus Austinornis.^[2] "Ichthyornis" minusculus from the Bissekty Formation (Late Cretaceous) of Kyzyl Kum, Uzbekistan, is probably an enantiornithine.

Apatosaurus

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Apatosaurus Fossil range: Late Jurassic, 150 Ma PreЄ Є O S D C P T J K Pg N ↓
Current Apatosaurus excelsus skeletal mount at the American Museum of Natural History
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Dinosauria Order: Saurischia Suborder: Sauropodomorpha Family: Diplodocidae Genus: Apatosaurus Marsh, 1877
Species
A. ajax Marsh, 1877 (type) A. excelsus (Marsh, 1879c) Riggs, 1903 A. louisae Holland, 1915 A. parvus (Peterson & Gilmore, 1902)
Synonyms
Brontosaurus Marsh, 1879c Elosaurus Peterson & Gilmore, 1902

Apatosaurus (pronounced /əˌpætɵˈsɔrəs/), including the popular but obsolete synonym Brontosaurus, is a genus of sauropod dinosaur that lived about 150 million years ago, during the Jurassic Period (Kimmeridgian and Tithonian ages). It was one of the largest land animals that ever existed, with an average length of 23 m (75 ft) and a mass of at least 23 metric tons (25 short tons). The name Apatosaurus means 'deceptive lizard', so-given because the chevron bones were similar to those of a prehistoric marine lizard, Mosasaurus. The composite term Apatosaurus comes from the Greek names apate (ἀπάτη)/apatelos (ἀπατηλός) meaning 'deception'/'deceptive' and sauros (σαῦρος) meaning 'lizard'.

The cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and the bones of the leg were much stockier (despite being longer), implying a more robust animal. The tail was held above the ground during normal locomotion. Like most sauropods, Apatosaurus had only a single large claw on each forelimb, with the first three toes on the hind limb possessing claws.

Fossils of this animal have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma and Utah, present in stratigraphic zones 2-6.^[1]

Contents [hide] 1 Description 2 Classification and species 3 History 4 Palaeobiology 4.1 Posture 4.2 Physiology 4.3 Tail 5 In popular culture 6 See also 7 References 8 External links

[edit] Description

Life restoration of Apatosaurus

Apatosaurus was a tremendously large long-necked quadrupedal animal with a long whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. One measurement places the total length of Apatosaurus at 26 meters (85 ft) and its weight at 24-32 tons, roughly the weight of four elephants.^[2]

The skull was small in comparison with the size of the animal. The jaws were lined with spatulate teeth, which resembled chisels, suited to an herbivorous diet.

[edit] Classification and species

Apatosaurus is a member of the family Diplodocidae, a clade of gigantic sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus, Supersaurus, Suuwassea, and Barosaurus. Within the subfamily Apatosaurinae, Apatosaurus may be most closely related to Suuwassea, Supersaurus and Eobrontosaurus.^[3][4][5]

In 1877, Othniel Charles Marsh published the name of the type species Apatosaurus ajax. He followed this in 1879 with a description of another, more complete specimen, which he thought represented a new genus and named Brontosaurus excelsus. In 1903, Elmer Riggs pointed out that Brontosaurus excelsus was in fact so similar to Apatosaurus ajax that it belonged in the same genus, which Riggs re-classified as Apatosaurus excelsus. According to the rules of the ICZN (which governs the scientific names of animals), the name Apatosaurus, having been published first, had priority as the official name; Brontosaurus was a junior synonym and therefore discarded from formal use.

Diplodocidae Apatosaurinae Suuwassea Supersaurus Apatosaurus Diplodocinae Barosaurus Diplodocus Cladogram of the Diplodocidae after Lovelace, Hartman, and Wahl, 2008.[5]

Apatosaurus ajax is the type species of the genus, and was named by the paleontologist Othniel Charles Marsh in 1877 after Ajax, the hero from Greek mythology. It is the holotype for the genus and two partial skeletons have been found, including part of a skull. Apatosaurus excelsus (originally Brontosaurus) was named by Marsh in 1879. It is known from six partial skeletons, including part of a skull, which have been found in the United States, in Colorado, Oklahoma, Utah, and Wyoming. Apatosaurus louisae was named by William Holland in 1915 in honor of Mrs. Louise Carnegie, wife of Andrew Carnegie who funded field research to find complete dinosaur skeletons in the American West. Apatosaurus louisae is known from one partial skeleton which was found in Colorado in the United States. Apatosaurus parvus was originally known as Elosaurus parvus, but was reclassified as a species of Apatosaurus in 1994.^[6] This synonymy was upheld in 2004.^[7]

Robert T. Bakker made A. yahnahpin the type species of a new genus, Eobrontosaurus in 1998, so it is now properly Eobrontosaurus yahnahpin. It was named by Filla, James and Redman in 1994. One partial skeleton has been found in Wyoming. However, recently it has been argued that Eobrontosaurus belongs within

Tyrannosaurus

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"T. rex" redirects here. For other uses, see T. rex (disambiguation).

Tyrannosaurus Fossil range: Late Cretaceous, 68.5–65.5 Ma PreЄ Є O S D C P T J K Pg N ↓
Tyrannosaurus rex skull, Palais de la Découverte, Paris.
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Reptilia Superorder: Dinosauria Order: Saurischia Suborder: Theropoda (unranked): Coelurosauria Superfamily: Tyrannosauroidea Family: Tyrannosauridae Subfamily: Tyrannosaurinae Genus: Tyrannosaurus Osborn, 1905
Species
T. rex (type) Osborn, 1905
Synonyms
Manospondylus Cope, 1892 Dynamosaurus Osborn, 1905 ?Nanotyrannus Bakker, Williams & Currie, 1988 Stygivenator Olshevsky, 1995 Dinotyrannus Olshevsky, 1995

Tyrannosaurus (pronounced /tɨˌrænɵˈsɔrəs/ or /taɪˌrænɵˈsɔrəs/, meaning 'tyrant lizard') was a genus of theropod dinosaur. The species Tyrannosaurus rex ('rex' meaning 'king' in Latin), commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the last three million years of the Cretaceous Period, approximately 68 to 65 million years ago. It was among the last non-avian dinosaurs to exist prior to the Cretaceous–Tertiary extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 13 metres (43 ft) in length,^[1] up to 4 metres (13 ft) tall at the hips,^[2] and up to 6.8 metric tons (7.5 short tons) in weight.^[3] By far the largest carnivore in its environment, Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running debates in paleontology.

More than 30 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of Tyrannosaurus rex are a few subjects of debate. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.

Contents [hide] 1 Description 2 Classification 2.1 Manospondylus 3 Paleobiology 3.1 Life history 3.2 Sexual dimorphism 3.3 Posture 3.4 Arms 3.5 Soft tissue 3.6 Skin and feathers 3.7 Thermoregulation 3.8 Footprints 3.9 Locomotion 3.10 Feeding strategies 4 History 4.1 Earliest finds 4.2 Notable specimens 5 Appearances in popular culture 6 References 7 Further reading 8 External links

Description

Various specimens of Tyrannosaurus rex with a human for scale

Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, FMNH PR2081 ("Sue"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13 ft) tall at the hips.^[2] Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons),^[4] to less than 4.5 metric tons (5.0 short tons),^[5][6] with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons).^[3][7][8][9] Although Tyrannosaurus rex was larger than the well known Jurassic theropod Allosaurus, it was slightly smaller than Cretaceous carnivores Spinosaurus and Giganotosaurus.^[10][11]

Size comparison of selected giant theropod dinosaurs, Tyrannosaurus in purple.

The neck of Tyrannosaurus rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs had only two clawed fingers,^[1] along with an additional small metacarpal representing the remnant of a third digit.^[12] In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.^[1]

The largest known Tyrannosaurus rex skulls measure up to 5 feet (1.5 m) in length.^[13] Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects Tyrannosaurus’ skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.^[14][15] The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids.^[16][17][18] The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.^[19][20]

dinosaurus

Dinosaurs (Greek δεινόσαυρος, deinosauros) is the dominant vertebrates in terrestrial ecosystems for over 160 million years old, from Old Triassic period (about 230 million years ago) until the end of the Cretaceous period (around 65 million years ago), when many of them extinct in the Cretaceous extinction event-Tertiary. Ten thousands of bird species living today have been classified as dinosaurs.

The discovery of primitive birds in 1861 to guide the first Archeopteryx close kinship between dinosaurs and birds. Besides the existence of fossilized feather impressions, is very similar Archeopteryx small predatory dinosaur Compsognathus. Since then, research has identified the theropod dinosaurs most likely as a direct ancestor of birds, mostly birds paleontologist now considered as the only surviving dinosaurs, and some suggest that dinosaurs and birds should be grouped in a biology class. [1] In addition to birds, crocodiles is another close relative of the dinosaurs that survived until now .. Like dinosaurs and birds, crocodiles are also members of the Archosauria, a group of reptiles which first appeared in a very old Perm period and dominated the middle Triassic period.

During the first half of the 20th century, many scientists believe dinosaurs community as a cold-blooded animals are dumb and slow. However, many studies conducted since the 1970s (called the renaissance of dinosaurs) have supported the view that dinosaurs were active animals with a high metabolism and adaptation to diverse social interactions. The resulting changes in scientific understanding of dinosaurs gradually filtered into the popular consciousness.

Since the first dinosaur fossil identified in the early nineteenth century, the framework is assembled dinosaurs became poluler performances in museums around the world. Dinosaurs became the world's cultural and continued popularity. They became the subject of best-selling books and films (most known for Jurassic Park), and new discoveries regularly expressed in the media

The term "dinosaur" (English, dinosaur) proposed in 1842 by Sir Richard Owen and the Greek bersal δεινός (deinos) "terrible, strong, great" + σαῦρος (sauros) "lizard". The term dinosaur is sometimes used informally to describe other prehistoric reptiles like Dimetrodon pelycosaurus, the winged pterosaurs, and ichthyosaurs, Plesiosaur and Mosasaurus, although none of these animals which are dinosaurs.