Opisthobranchia, subclass Opisthobranchia(noun)
gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs; sea butterflies; sea hares
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping. Euopisthobranchia is a revised collection of opisthobranchs that is monophyletic, but this group leaves out some "traditional" opisthobranchs. The Opisthobranchia includes a number of species in the order Cephalaspidea, the sacoglossans, the anaspidean sea hares, the pelagic sea angels, the sea butterflies, and many families of Nudibranchia. Opisthobranch means "gills behind" of the heart. In contrast, Prosobranch means gills in front. Opisthobranchs are characterized by two pairs of tentacles and a single gill behind and to the right of the heart. Opisthobranchia are known from as early as the Carboniferous.
The numerical value of opisthobranchia in Chaldean Numerology is: 1
The numerical value of opisthobranchia in Pythagorean Numerology is: 5
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"opisthobranchia." Definitions.net. STANDS4 LLC, 2018. Web. 17 Jan. 2018. <http://www.definitions.net/definition/opisthobranchia>.