Morphological evidence shows not all Velesunioninae have sculptured umbos
Zieritz, A., Sartori, A.F. and Klunzinger, M.W. (2013) Morphological evidence shows not all Velesunioninae have sculptured umbos. Journal of Molluscan Studies, 79 (3). pp. 277-282.
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Most species in the freshwater bivalve order Unionida (sensu Carter et al., 2011) display some form of shell sculpture during the early postlarval stage. These so-called ‘umbonal sculptures’, ‘beak sculptures’ or ‘rugae’ range from more or less regularly formed V- and zigzag-shapes to pseudoradial, pseudoconcentric and double-looped bars, and single-standing nodules (Modell, 1942, 1964; Watters, 1994; Zieritz, 2010). In some Unionida, this ornamentation may extend to mature ontogenetic stages (e.g. Hyriidae; Haas, 1969a, b; Watters, 1994). Others, however, are regarded as lacking sculptured umbos altogether. These include (1) the Mycetopodidae (according to descriptions by Modell, 1942, 1964; Haas, 1969a, b; Zieritz, 2010); (2) most Iridininae including Mutela rostrata (Rang, 1835), Pleiodon ovata (Swainson, 1823) and Pleiodon spekii (Woodward, 1859) (according to descriptions by Pilsbry & Bequaert, 1927; Zieritz, 2010); and (3) some Unionidae such as Actinonaias pectorosa (Conrad, 1834), Delphinonaias delphinulus (Morelet, 1849) and Pseudospatha tanganyicensis (Smith, 1880) (Zieritz, 2010). Finally, various authors, including Cotton & Gabriel (1932), Iredale (1934), Modell (1942, 1964), McMichael & Hiscock (1958) and Haas (1969a), stated that smooth umbos are also characteristic of all members of (4) the Velesunioninae, a subfamily of the Hyriidae endemic to the Australasian region (Walker et al., 2001; Walker, Jones & Klunzinger, 2013). Haas (1969b), on the other hand, described beak sculpture in the “subgenus Velesunio”—comprising four of the five currently recognized velesunionine genera (except Lortiella)—as “not strong, consisting of broken, nodulose ridges curving toward each other below, generally with smooth space between”. Unfortunately, no illustration of these sculptures has been made available by this or any other author to date.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Veterinary and Life Sciences|
|Publisher:||Oxford University Press|
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