Eumalacostraca is a subclass of crustaceans, containing almost all living malacostracans, or about 40,000 described species. The remaining subclasses of crustaceans that are not in Eumalacostraca are the Phyllocarida and possibly the Hoplocarida. Eumalacostracans have 19 segments (5 cephalic, 8 thoracic and 6 abdominal). This arrangement is known as the "caridoid facies", a term coined by William Thomas Calman in 1909. The thoracic limbs are jointed and used for swimming or walking. The common ancestor is thought to have had a carapace, and most living species possess one, but it has been lost
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Subclass
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Eumalacostraca is a subclass of crustaceans, containing almost all living malacostracans, or about 40,000 described species. The remaining subclasses of crustaceans that are not in Eumalacostraca are the Phyllocarida and possibly the Hoplocarida. Eumalacostracans have 19 segments (5 cephalic, 8 thoracic and 6 abdominal). This arrangement is known as the "caridoid facies", a term coined by William Thomas Calman in 1909. The thoracic limbs are jointed and used for swimming or walking. The common ancestor is thought to have had a carapace, and most living species possess one, but it has been lost in some subgroups.
==Caridoid facies== Calman identified the following features as distinguishing eumalacostracan crustaceans: "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."
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Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).