protobranchn.adj.
/ˈprəʊtə(ʊ)braŋk/, U.S. /ˈproʊdoʊˌbræŋk/ Zoology and Palaeontology.
A. n.
A bivalve mollusc of the relatively primitive subclass Protobranchia, whose members are characterized by gills having a simple leaflike structure.
ΚΠ
1899 Amer. Naturalist 33 672 The test of the protobranchs is strikingly similar to that found..on the embryo of Dondersia, one of the primitive group of Solenogastres.
1958 J. E. Morton Molluscs iii. 50 In protobranchs such as Nucula..the sole is still a flat disc.
2000 Paleobiology 26 203/1 There would appear..to be two main groups of bivalve clades: an older ‘late Paleozoic-Jurassic’ one (protobranchs, arcoids, mytiloids, pteriomorphs, and lucinoids) and a younger, ‘Cretaceous’ one (heteroconchs and anomalodesmatans).
B. adj.
Designating, relating to, or characterized by a type of molluscan gill having a simple, leaflike structure, as in bivalve molluscs of the subclass Protobranchia.
ΚΠ
1902 Proc. Royal Soc. 70 500 Their superficial resemblance to the Protobranch gill is due to an expansion of the interlamellar edge of the filaments.
1968 Science 15 Mar. 1232/1 The less abundant protobranch bivalve molluscs and pleurotomariid gastropods, both of which were probably detritus-feeders, occurred in localized patches.
1993 E. N. K. Clarkson Invertebr. Palaeontol. & Evol. (ed. 3) viii. 201/1 In Order Nuculoida..the gills are protobranch, being small and leaf-like rather like those of amphineurans and cephalopods.
Derivatives
ˌprotoˈbranchiate adj. = sense B.
ΚΠ
1903 Philos. Trans. (Royal Soc.) B. 195 157 (note) Drew..is a little loath to admit the primitive nature of the Protobranchiate gill.
1996 Invertebr. Biol. 115 236/2 Yoldia..has a relatively simple protobranchiate ctenidium.
This is a new entry (OED Third Edition, September 2007; most recently modified version published online March 2022).
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n.adj.1899