Mid 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From scientific Latin Opisthobranchiata, subclass name (originally order name; 1851 or earlier) from opistho- + -branchiata.
Definition of opisthobranchiate in US English:
opisthobranchiate
adjective
Zoology
Opisthobranch.
Origin
Mid 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From scientific Latin Opisthobranchiata, subclass name (originally order name; 1851 or earlier) from opistho- + -branchiata.