Animal Life

Phylum Onychophora

Onychophora (Onychophorans, velvet worms, and peripatus) Number of families 2 Thumbnail description Terrestrial carnivorous worms with legs along the whole length of the body, paired eyes, a conspicuous pair of antennae, and a velvety appearance Photo: An onychophoran seen in Peru. Evolution and systematics A number of fossils have been linked to the Onychophora, but […]

Phylum Tardigrada

Tardigrada (Water bears) Number of families 20 Thumbnail description Microscopic, aquatic, multicellular, segmental animals with four pairs of legs Photo: Colored scanning electron micrograph of a water bear (Echiniscus testudo) in its crypto-biotic tun, or barrel, state. Evolution and systematics The phylum Tardigrada belongs to the Panarthropoda group, together with the onychophorans (velvet worms) and […]

Subphylum CRUSTACEA

Phylum ARTHROPODA

Class Remipedia

Remipedia (Remipedes) Phylum Arthropoda Subphylum Crustacea Number of families 2 Thumbnail description Small, marine, cave-dwelling crustaceans characterized by a short head and a long trunk bearing setose swimming appendages. Photo: An individual of the species Lasionectes entrichoma from the Turks and Caicos Islands. Evolution and systematics The class Remipedia has two families, six genera, and […]

Class Cephalocarida

Cephalocarida (Cephalocarids) Phylum Arthropoda Subphylum Crustacea Number of families 2 Thumbnail description Cephalocarids are small crustaceans with elongate bodies, short heads without carapace, and flattened, paddle-like appendages on the thorax Illustration: Hutchinsoniella macracantha. Evolution and systematics Cephalocarids, when first discovered in Long Island Sound, were thought to be the most primitive of living crustaceans. This […]

Class BRANCHIOPODA

Order Anostraca

Anostraca (Fairy shrimps) Phylum Arthropoda Subphylum Crustacea Class Branchiopoda Number of families 8 Thumbnail description Lower crustaceans with elongated bodies and paired eyes on stalks; the body lacks a carapace (hard or bony shell) Photo: Fairy shrimps are fresh water residents and have 11 pairs of legs. Evolution and systematics On the basis of evidence […]

Order Nostostraca

Notostraca (Tadpole shrimps) Phylum Arthropoda Subphylum Crustacea Class Branchiopoda Number of families 1 Thumbnail description Pale-colored or translucent crustacean with a flattened shield-like carapace that covers two-thirds of the body and a thin, elongated abdomen ending in paired tail filaments Photo: The tadpole shrimp species Triops cancri-formis is one of the oldest known animal species […]

Order Conchostraca

Conchostraca (Clam shrimps) Phylum Arthropoda Subphylum Crustacea Class Branchiopoda Number of families 5 Thumbnail description Shrimps that possess a bivalved shell with a hinge that envelops the entire body and limbs; they are found exclusively in freshwater Photo: Clam shrimps (Limnadia lenticularis) are found in temporary puddles, sometimes dug into the mud at the bottom […]

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