unionoid

From taxonomic name Unio (with insertion of -n- after its etymon, Classical Latin ūniō (stem ūniōn-)) +‎ -oid. Compare earlier unionid and taxonomic name Unionioda.^[1]

unionoid (plural unionoids)

1. (zoology) Any member of the family Unionidae or its order Unionida of freshwater mussels.

   Synonyms: unioid, 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:

     II. n. Same as unionid.]

unionoid (comparative more unionoid, superlative most unionoid)

1. (zoology) Relating to, resembling or characteristic of the family Unionidae or its order Unionida of freshwater mussels.

   Synonyms: unionid, unioniform

   • 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:

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

   • 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:

     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.

   • 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:

     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.