Monday, October 28, 2013

10 Living Fossils That You Probably Didn’t Know Existed

A living fossil is a living species (or clade) of organism that appears to be similar to a species otherwise known only from fossils, typically with no close living relatives. Normally the similarity is only apparent, between two different species, one extinct, the other extant. It is an informal non-scientific term, mostly used in the media. These species have survived major extinction events, and generally retain low taxonomic diversities. A species that successfully radiates (forming many new species after a possible genetic bottleneck) has become too successful to be considered a living fossil.

That's a short introduction so let’s get to the list...

1. Bearded Vulture

The Bearded Vulture (Gypaetus barbatus), also known as the Lammergeier or Lammergeyer, is a bird of prey, and the only member of the genus Gypaetus. Traditionally considered an Old World vulture, it actually forms a minor lineage of Accipitridae together with the Egyptian Vulture (Neophron percnopterus), its closest living relative. It is not much more closely related to the Old World vultures proper than to, for example, hawks, and differ from the former by their feathered neck. Although dissimilar, Egyptian and Bearded Vultures both have a lozenge-shaped tail that is unusual among birds of prey.

2. Okapi

The okapi (Okapia johnstoni), is a giraffid artiodactyl mammal native to the Ituri Rainforest, located in the northeast of the Democratic Republic of the Congo, in Central Africa. Although the okapi bears striped markings reminiscent of zebras, it is most closely related to the giraffe.

3. Nautilus

Nautilus is the common name of pelagic marine mollusks of the cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus. Though it more specifically refers to species Nautilus pompilius, the name chambered nautilus is also used for any species of the Nautilidae.

4. Little Chevrotain

Chevrotains, also known as mouse-deer, are small ungulates that make up the family Tragulidae, the only members of the infraorder Tragulina. The 10 extant species are in three genera, but several species also are only known from fossils. The extant species are found in forests in South and Southeast Asia, with a single species in the rainforests of Central and West Africa. They are solitary or live in pairs, and feed almost exclusively on plant material. Depending on exact species, the Asian species weigh between 0.7 and 8.0 kg, and the smallest species are also the smallest ungulates in the world. The African chevrotain is considerably larger at 7–16 kg.

5. Horseshoe Crab 

Horseshoe crab are marine arthropods of the family Limulidae and order Xiphosura or Xiphosurida that live primarily in and around shallow ocean waters on soft sandy or muddy bottoms. They occasionally come onto shore to mate. They are commonly used as bait and in fertilizer. In recent years, a decline in the number of individuals has occurred as a consequence of coastal habitat destruction in Japan and overharvesting along the east coast of North America. Tetrodotoxin may be present in the roe of species inhabiting the waters of Thailand. Horseshoe crab are considered living fossils.

6. Hoatzin 

The Hoatzin (Opisthocomus hoazin), also known as the Hoactzin, Stinkbird, or Canje Pheasant, is a species of tropical bird found in swamps, riverine forest and mangrove of the Amazon and the Orinoco delta in South America. It is notable for having chicks that possess claws on two of their wing digits.

7. Frilled Shark 

The frilled shark (Chlamydoselachus anguineus) is one of two extant species of shark in the family Chlamydoselachidae, with a wide but patchy distribution in the Atlantic and Pacific Oceans. This rare species is found over the outer continental shelf and upper continental slope, generally near the bottom, though there is evidence of substantial upward movements. It has been caught as deep as 1,570 m (5,150 ft). In Suruga Bay, Japan it is most common at depths of 50–200 m (160–660 ft). Exhibiting several "primitive" features, the frilled shark has often been termed a "living fossil". It reaches a length of 2 m (6.6 ft) and has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of its six pairs of gill slits, with the first pair meeting across the throat.

8. Coelacanth 

The coelacanths constitute a rare order of fish that includes two extant species in the genus Latimeria: the West Indian Ocean coelacanth (Latimeria chalumnae) and the Indonesian coelacanth (Latimeria menadoensis). They follow the oldest known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish, reptiles and mammals than to the common ray-finned fishes. They are found along the coastlines of the Indian Ocean and Indonesia. Since there are only two species of coelacanth and both are threatened, it is the most endangered order of animals in the world. The West Indian Ocean coelacanth is a critically endangered species.

9. Clam Shrimp 

Clam shrimp are a taxon of bivalved branchiopod crustaceans that resemble the unrelated bivalved molluscs. They are extant, and known from the fossil record, from at least the Devonian period and perhaps before. They were originally classified in a single order Conchostraca, which later proved to be paraphyletic.

10. Axolotl

The axolotl also known as a Mexican salamander (Ambystoma mexicanum) or a Mexican walking fish, is a neotenic salamander, closely related to the tiger salamander. Although the axolotl is colloquially known as a "walking fish", it is not a fish, but an amphibian. The species originates from numerous lakes, such as Lake Xochimilco underlying Mexico City. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled.

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