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Anaspidaceans (an-ah-spih-DAY-see-ans) are usually dull brown. They measure up to 1.9 inches (50 millimeters), but some species are less than 0.39 inches (10 millimeters). They have a head, thorax, and abdomen. They may or may not have a beaklike rostrum. The eyes are found either on the tips of stalks or on the head. Some species do not have eyes at all. The first pair of antennae, or antennules (an-TEN-yuls), is either branched or not. The second pair of antennae is biramous (BY-ray-mus) or branched. The mandibles are uniramous (YU-neh-RAY-mus) or unbranched. They do not have a shieldlike carapace covering the head and thorax. The first thoracic (thuh-RAE-sik) segment is tightly joined with the head. It has a pair of maxillipeds, thoracic limbs associated with the mouth.

The pairs of thoracic legs are either unbranched or branched. In biramous legs, the inner branch is called the endopod (IHN-doh-pawd), while the outer branch is called the exopod (EHK-soh-pawd). The flaplike gills, organs used for breathing underwater, are located on the bases of the legs. The movements of the exopods keep oxygen-carrying water flowing over the gills. The abdomen also has segments. There are one, two, or five pairs of pleopods (PLEE-oh-pawds), or limblike structures attached to the underside of the abdomen. The tip of the abdomen has a pair of long appendages called uropods (YUR-oh-pawds). The uropods are found on either side of a central tail segment, or telson . The uropods and telson sometimes form a fanlike tail.

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