Late 19th century (in an earlier sense). From scientific Latin Monactinellida from mono- + ancient Greek ἀκτιν-, ἀκτίς ray + scientific Latin -ella + -ida.
Definition of monactinellid in US English:
monactinellid
nounmɒˌnaktɪˈnɛlɪd
Zoology rare
A monactinal sponge.
Origin
Late 19th century (in an earlier sense). From scientific Latin Monactinellida from mono- + ancient Greek ἀκτιν-, ἀκτίς ray + scientific Latin -ella + -ida.