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A biramous limb, however, branches into two, and each branch consists of a series of segments attached end-to-end. The external branch (ramus) of the appendages of crustaceans is known as the exopod or exopodite , while the internal branch is known as the endopod or endopodite .
Anaspidacea is an order of crustaceans, comprising eleven genera in four families. Species in the family Anaspidesidae vary from being strict stygobionts (only living underground) to species living in lakes, streams and moorland pools, and are found only in Tasmania . [ 1 ]
Crustacean appendages are typically biramous, meaning they are divided into two parts; this includes the second pair of antennae, but not the first, which is usually uniramous, the exception being in the Class Malacostraca where the antennules may be generally biramous or even triramous.
Anaspidesidae is a family of freshwater crustacean that is endemic to Tasmania, Australia. [1] The family contains 3 living genera.This group of crustaceans are considered living fossils. [1]
This pair is generally uniramous, but is biramous in crabs and lobsters and remipedes. The pair attached to the second segment are called secondary antennae or simply antennae . The second antennae are plesiomorphically biramous, but many species later evolved uniramous pairs. [ 2 ]
Calman identified the following features as distinguishing eumalacostracan crustaceans: [3] "Carapace enveloping the thoracic region; movably stalked eyes; biramous first antenna; scale-like exopod on the second antenna; natatory exopods on the thoracic limbs; elongate, ventrally flexible abdomen; tail fan formed by the lamellar rami of the uropods on either side of the telson."
Compared to many other ostracoderms, such as the Heterostraci and Osteostraci, anaspids did not possess a bony shield or armor, hence their name.The anaspid head and body are instead covered in an array of small, weakly mineralized scales, with a row of massive scutes running down the back, and, at least confirmed among the birkeniids, the body was covered in rows of tile-like scales made of ...
Anaspididae is a family of freshwater crustacean that is endemic to Tasmania, Australia. [1] The family contains 3 living genera.This group of crustaceans are considered living fossils. [1]