File:Physeter macrocephalus (sperm whale) (Wrightsville Beach, North Carolina, USA) 9 (31232078701).jpg

Physeter macrocephalus Linnaeus, 1758 - sperm whale skeleton (real). (public display, North Carolina Museum of Natural Sciences, Rayleigh, North Carolina, USA)

Mammals are the dominant group of terrestrial vertebrates on Earth today. The group is defined based on a combination of features: endothermic (= warm-blooded), air-breathing, body hair, mother's milk, four-chambered heart, large brain-to-body mass ratio, two teeth generations, differentiated dentition, and a single lower jawbone. Almost all modern mammals have live birth - exceptions are the duck-billed platypus and the echidna, both of which lay eggs.

Mammals first appear in the Triassic fossil record - they evolved from the therapsids (mammal-like reptiles). Mammals were mostly small and a minor component of terrestrial ecosystems during the Mesozoic. After the Cretaceous-Tertiary mass extinction at 65 million years ago, the mammals underwent a significant adaptive radiation - most modern mammal groups first appeared during this radiation in the early Cenozoic (Paleocene and Eocene).

Three groups of mammals exist in the Holocene - placentals, marsupials, and monotremes. Other groups, now extinct, were present during the Mesozoic.

Whales are members of Order Cetacea, which includes the dolphins and porpoises. Cetaceans have intermediate- to very large-sized bodies that are streamlined (cigar-shaped) and have a thick blubber layer for heat insulation purposes. They are evolutionarily derived from terrestrial mammals that had four legs. The former front legs are now flippers. The hind legs are highly reduced and non-functional in whales. The skull is elongated, with one or two blowholes atop the head. The tail is horizontally-oriented, unlike the vertically-oriented caudal fin ("tail") of a fish. Vertical movement of a whale's tail provides propulsion. Whale bodies have a soft outer skin layer with almost no hair - this improves water flow around the body.

Whales are famous for being deep and long divers. Sperm whales can dive to over 9,200 feet deep. Northern bottlenose whales can hold their breath for over two hours. Unlike humans, whales have evolved mechanisms for coping with diving diseases such as nitrogen narcosis and decompression sickness.

Cetaceans are subdivided into two groups - the mysticete and the odontocete whales. Mysticete whales are the baleen whales - they include the blue whale, finback whale, humpback whale, gray whale, right whale, minke whale, sei whale, etc. The odontocetes are the toothed whales and include the sperm whale, killer whale, dolphins, porpoises, and belugas. Toothed whales have smaller bodies than the baleen whales. They have one blowhole atop the head and have prominent teeth - they feed on fish and squid and other large animals.

The skeleton shown above is a sperm whale, the largest modern species of toothed whale.

From museum signage: "Wrinkled skin, a huge head, and an off-center spout make a sperm shale easy to identify. They can grow to 60 feet and weigh as much as 64 tons. This species it the most numerous of all great whales, with an estimated two million inhabiting the world's deepest oceans.

Sperm whales can dive as deep as a mile and stay underwater for up to an hour. They eat mainly squids and octopuses. These whales were hunted extensively in the 18th and 19th centuries for the high-quality oil found only in the head of this species.

Each day, an average male sperm whale will eat more than a ton of squid. Like all toothed whales, the sperm whale uses echolocation to find food in the deep, dark sea. It sends out loud clicking sounds that reflect off objects and produce echoes that the whale hears and interprets.

This sperm shale washed ashore at Wrightsville Beach in 1928. Some 50,000 people from six states flocked here to see it. The tourism boom ended when the whale began to decay. It raised a stink that cleared the beach, becoming a health hazard as well as a public nuisance. Locals called the whale "Trouble", and it lived up to its name - particularly for the museum, which wanted the whale's skeleton for display.

Moving the whale wasn't an easy task. First the 54-foot, 100,000 pound whale had to be towed to an uninhabited beach. Towing cables broke and the whale was nearly lost in the rough sea. Once onshore, Trouble washed off the beach and onto a nearby shoal where it stayed until stripped of most of its flesh.

Trouble's bones were buried for a total of 16 months [on a beach for six months and again at the fairgrounds in Raleigh for ten months] so that natural processes could remove the rest of its flesh. Then it took another two years to clean and assemble the bones for exhibit.

Museum director H.H. Brimley, who coordinated the effort to obtain Trouble, and his assistant spent nearly two years preparing and assembling Trouble's bones for display. In 1930, Trouble's skeleton was hung in the museum. At the time, only three other adult sperm whales were on display in the United States.

Early sailors scratched and inked designs in the teeth of sperm whales, a craft called scrimshaw. Oil from the whale's head and ambergris, a waxy substance found in its intestines, were used as perfume fixatives.

Sperm whales have a social structure based largely on reproductive habits. Females and juveniles form groups of 25 to 40 animals - "nursery schools". During breeding season, a male joins the nursery school, which temporarily becomes a harem. After breeding, males leave the harems and form "bachelor schools".

Sperm whales migrate, usually in groups separated primarily by sex and age. Pregnant and nursing females and their young migrate between temperate and tropical waters. Males range farther north, venturing into warm waters only during breeding season. "

Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, Cetacea, Odontoceti, Physeteridae

See info. at: <a href="https://en.wikipedia.org/wiki/Sperm_whale" rel="nofollow">en.wikipedia.org/wiki/Sperm_whale</a> and <a href="https://en.wikipedia.org/wiki/Toothed_whale" rel="nofollow">en.wikipedia.org/wiki/Toothed_whale</a> and