unionoid

plural unionoids

1. biologyAny member of the family Unionidae or its order Unionida of freshwater mussels.

   II. n. Same as unionid.

   [1891, “unionoid (ū′ni-ọ̄-noid), a. and n.”, in William Dwight Whitney, editor, The Century Dictionary: An Encyclopedic Lexicon of the English Language […], volume VI, New York, N.Y.: The Century Co., →OCLC, page 6619, column 3

   Synonyms: unioid, unionid

comparative more unionoid · superlative most unionoid

1. biologyRelating to, resembling or characteristic of the family Unionidae or its order Unionida of freshwater mussels.

   Carbonicola, of the Devonian and Carboniferous, comprises Unionoid Bivalves, with thick shells, an external ligament, and a concentrically-striated surface.

   1879, Henry Alleyne Nicholson, “Unionidæ”, in A Manual of Palæontology for the Use of Students […], 2nd edition, volume I, Edinburgh; London: William Blackwood and Sons, →OCLC, page 492

   2 more examples

   I know nothing of that of Solenaia beyond the statement of Fischer regarding its greatly developed, mushroom shaped foot and its burrowing habit. It is, I am satisfied, an unionoid animal and the fact that there is a decided posterior pallial sinus to the shell leads me to believe that it has two siphons.

   1914, Charles Torrey Simpson, “Genus Solenaia Conrad, 1869”, in A Descriptive Catalogue of the Naiades, or Pearly Fresh-Water Mussels, part I (Unionidæ: Truncilla–Margaritana), Detroit, Mich.: Bryant Walker, →OCLC, page 456

   The current record of Australian Lower Cretaceous non-marine macroinvertebrates is substantial but mainly limited to a few highly productive localities. Some remains have been recovered from near-shore marine rocks including the Valanginian Trinity Well Sandstone Member of the Cadna-owie Formation (South Australia) and the Aptian Wallumbilla Formation (White Cliffs, New South Wales). These have produced freshwater unionoid bivalves (Alathyria coatsi, Hyridella whitecliffsensis) and Australia’s oldest known non-marine gastropod – the viviparid Notopala alboscopularis.

   2011, Benjamin P. Kear, Robert J. Hamilton-Bruce, “Non-marine invertebrates”, in Dinosaurs in Australia: Mesozoic Life from the Southern Continent, Collingwood, Vic.: CSIRO Publishing, →ISBN, chapter 6 (Life on the shore: Early Cretaceous non-marine animals and plants), page 112, column 1

   Synonyms: unionid, unioniform