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An order of Heliozoia. These protozoans are characterized by stiff arms radiating from the central cell mass. Each arm is supported internally by an array of microtubules which terminate on the surface of nuclei. The organisms are found in…

A class of Sarcodina; or in some modern schemes a superclass (Actinopoda) within the phylum Sarcomastigophora. Some of these protozoans have more or less permanent pseudopodia, composed of a central shaft of microtubules surrounded by a thin…

A class of teleostom fishes commonly known as the ray-finned fishes, which are distinguished by the structure of the paired fins that are supported by dermal rays. The class Actinopterygii comprises the subclasses Cladistia [Polypteriformes (bichirs…

A large, rabbit-sized rodent, belonging to the family Dasyproctidae and inhabiting South America and Central America, which is well adapted for speed because of its elongated hind legs. The agouti is a large rodent that resembles the rabbit or hare…

An order of actinopterygian fishes in the subdivision Elopomorpha, along with Elopiformes, Anguilliformes, and Saccopharyngiformes, all of which have a leptocephalous larval stage. Albuliformes, comprising three families, eight genera, and 30…

An order of the class Anthozoa (phylum Cnidaria), containing 2500–3000 species, commonly referred to as soft corals, sea fans, sea whips, and precious coral. Members of the Alcyonacea are strictly marine. They occur from northern to southern polar…

A large aquatic reptile of the family Alligatoridae. Alligators belong to the family Alligatoridae in the reptilian order Crocodylia (Crocodilia). Common usage generally restricts the name alligator to the two extant species of the genus Alligator.…

One of the four subclasses of Mammalia, containing a single order, the Multituberculata. The Allotheria first appeared in the Late Jurassic and survived well into the Cenozoic, a period of at least 100,000,000 years. Fossils are known from North…

Vicugna pacos, a member of the camel family (Camelidae), which has been domesticated for more than 2000 years and is economically important for its long, fine wool. The alpaca (Vicugna pacos; formerly, Lama pacos) [see illustration] belongs to the…

A fatty substance formed in the intestinal tract of the sperm whale (Physeter catodon). There is a question as to whether the origin of ambergris is normal or pathological, but it does serve as protection from the horny indigestible portions of the…