FACTH about COELACANTH.

COELACANTH FACT.

(1) You'd think it would be hard to miss a six-foot-long, 200-pound fish, but the discovery of a live Coelacanth in 1938 caused an international sensation. On the following slides, you'll discover everything you need to know about this "living fossil."

(2) Coelacanths first appeared in the world's oceans during the late Devonian period (about 360 million years ago), and persisted all the way to the end of the Cretaceous, when they went extinct along with dinosaurs, pterosaurs and marine reptiles. Despite their 300-million-year track record, though, coelacanths were never particularly abundant, especially compared to other families of prehistoric fish.

(3).The vast majority of creatures that go extinct manage to *stay* extinct. That's why scientists were so shocked when, in 1938, a sailing vessel dredged up a live Coelacanth near the coast of South Africa. This "living fossil" generated instant headlines around the world, and fueled hopes that somewhere, somehow, a population of Ankylosaurus or Pteranodon had escaped the end-Cretaceous extinction and survived to the present day.

(4).Sadly, in the decades following the discovery of Latimeria chalumnae (as the first Coelacanth species was named), there were no reliable encounters with living, breathing tyrannosaurs or ceratopsians. In 1997, though, a second Coelacanth species (L. menadoensis) was discovered in Indonesia. Genetic analysis showed that the Indonesian Coelacanth differs significantly from the African species, though they may both have evolved from a common ancestor.

(5).The vast majority of fish in the world's oceans, lakes and rivers--including salmon, tuna, goldfish and guppies--are "ray-finned" fish, or actinopterygians, the fins of which are supported by characteristic spines. Coelacanths, by contrast, are "lobe-finned" fish, or sarcopterygians, whose fins are supported by fleshy, stalklike structures. Besides Coelacanths, the only extant sarcoptergians alive today are the lungfish of Africa, Australia and South America.

(6).Just how distinctive are Coelacanths? Well, both identified Latimeria species have heads that can pivot upwards, thanks to an "intracranial joint" on the top of the skull (an adaptation that allows these fish to open their mouths extra-wide in order to swallow prey). Not only is this feature lacking in other lobe-finned and ray-finned fish, but it hasn't been seen in any other vertebrates on earth, including sharks and snakes.

(7).As you might expect given their extreme rarity, Coelacanths tend to stay well out of sight. Both species of Latimeria live about 500 feet below the water (in the so-called "twilight zone"), preferably in small caves carved out of limestone deposits. It's impossible to know for sure, but the total Coelacanth population may number in the low thousands, making this one of the world's rarest and most endangered fish.

(8).Like assorted other fish and reptiles, coelacanths are "ovoviviparous"--that is, the female's eggs are fertilized internally, and stay in the birth duct until they're ready to hatch. Technically, this type of "live birth" is different from that of placental mammals, where the developing embryo is attached to the mother via an umbilical cord. (While we're on the subject, one captured female Coelacanth was found to have 26 newborn hatchlings inside, each of them over a foot long).

(9).As rare as they are today, lobe-finned fish like Coelacanths constitute an important link in vertebrate evolution. About 400 million years ago, various populations of sarcopterygians evolved the ability to crawl out of the water and breathe on dry land. One of these brave tetrapods was ancestral to every land-dwelling animal on earth today, including reptiles, birds and mammals--which all bear the characteristic five-toed anatomy of their distant progenitor.

(10).The Coelacanth's "twilight zone" habitat makes the ideal fit for its sluggish metabolism: Latimeria isn't much of an active swimmer, preferring to drift along in deep-sea currents and gobble whatever smaller marine animals happen across its path. Unfortunately, the inherent laziness of Coelacanths make them a prime target for bigger marine predators, which explains why some Coelacanths observed in the wild sport prominent shark-shaped bite wounds.(source:dinosours.about)