squid are members of what phylum and what class
They are members of the class Cephalopoda, subclass Coleoidea.
Squid
Squid are members of the class Cephalopoda, subclass Coleoidea.
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Squid [SEP] Taxonomy and phylogeny
Squid are members of the class Cephalopoda, subclass Coleoidea. The squid orders Myopsida and Oegopsida are in the superorder Decapodiformes (from the Greek for "ten-legged"). Two other orders of decapodiform cephalopods are also called squid, although they are taxonomically distinct from squids and differ recognizably in their gross anatomical features. They are the bobtail squid of order Sepiolida and the ram's horn squid of the monotypic order Spirulida. The vampire squid ("Vampyroteuthis infernalis"), however, is more closely related to the octopuses than to any squid. The cladogram, not fully resolved, is based on Sanchez et al., 2018. Their molecular phylogeny used mitochondrial and nuclear DNA marker sequences; they comment that a robust phylogeny "has proven very challenging to obtain".