In zoological nomenclature , a subphylum is a taxonomic rank below the rank of phylum .
3-397: Conchifera is a subphylum of the phylum Mollusca , containing five extant classes : Monoplacophora , Cephalopoda , Gastropoda , Bivalvia , and Scaphopoda . Conchiferans can bear a single shell as in snails and ammonites , a single pair of shells as in clams , or lack a shell as in slugs and squid . The other subphylum is Aculifera , the members of which are shellless or have
6-579: A row of several plates. Non-monoplacophoran conchiferans emerged within the once-widespread Monoplacophora. The only descendant which retains its ancestral shape is the Tryblidiida . The monophyly of Conchifera is supported by molecular phylogenetic analysis. The relationships among the members of Conchifera are disputed. A grouping of Scaphopoda and Bivalvia, named Diasoma , has been proposed, but other studies find scaphopods to be more closely related to cephalopods or gastropods. Conchifera originated in
9-639: The early Cambrian period . Classes within the Conchifera include: Subphylum The taxonomic rank of " subdivision " in fungi and plant taxonomy is equivalent to "subphylum" in zoological taxonomy. Some plant taxonomists have also used the rank of subphylum, for instance monocotyledons as a subphylum of phylum Angiospermae and vertebrates as a subphylum of phylum Chordata . Subphylum is: Where convenient, subphyla in turn can be divided into infraphyla ; in turn such an infraphylum also would be superordinate to any classes or superclasses in
#483516