Parthenina(?) gradatula (Mørch, 1876)

Scanning Electron Micrograph (SEM)

   Culled from grunge collected from a mangrove beach on the Jupiter Sound (Indian River) shore of Coral Cove Park (just S of Blowing Rock Preserve) by Rick Edwards on 4/27/2021 (1.79 mm.). SEM produced in collaboration with Dr. Ann Heatherington, Dept. of Geological Sciences, University of Florida, Gainesville, FL.

    In shell grit taken by SCUBA from a depth of 69 feet off Boynton Beach, FL (2 mm.).  Digital image by David Kirsh.

This species was known by a junior synonym, Chrysallida toroensis (Olsson and McGinty, 1958), until recently. Faber (2005) located and figured Mørch's type material, recognized the senior synonymy of that nominal taxon, and transferred it to the genus Mumiola A. Adams, 1863, where MolluscaBase continues to place the taxon: <http://molluscabase.org/aphia.php?p=taxdetails&id=420455>. However, the type species of the latter genus, Monoptygma spirata A. Adams, 1853, which closely resembles Mumiola myrnae Poppe, Tagaro and Stahlschmidt, 2015 differs remarkably in shell characters, including the protoconch. Expert Pat LaFollette has pointed out the close similarity of certain members of the genus Parthenina Bucquoy, Dautzenberg, and Dollfus, 1883, e.g., P. scalarum Peñas and Rolán, 2017 [Penas, Rolan, and Sabelli, 2020: Fig. 5A]. However the protoconch of that species, and all congeners thus far, is fully immersed in the teleoconch (Idem: Fig 5C; Type C), while that of the featured shell is only partially immersed (Type B) - hence the question mark above.

Faber, M.J., 2005. Studies on West Indian marine molluscs 45. The Caribbean marine gastropods described by Otto Andreas Lawson Mørch 1: some type specimens and identifications (Gastropoda: Prosobranchia).   Miscellanea Malacologica 1(5): 81-99. 28 December.

Mørch, O.A.L., 1876. Synopsis molluscorum marinorum Indiarum occidentalium imprimis insularum danicarum. Malakozoologische Blätter 23: 45-58, 87-143. <http://biodiversitylibrary.org/page/15854452>

Olsson, A.A. & T.L. McGinty, 1958. Recent marine mollusks from the Caribbean Coast of Panama with the description of some new genera and species. Bulletins of American Paleontology 39(177): 1-58. <https://www.biodiversitylibrary.org/page/10645693 [details]>

Peñas, A. and E. Rolán, 2017. Deep water Pyramidelloidea from the Central and South Pacific. 3. The tribe Chrysallidini. Sociedad Española de Malacología. ECIMAT. Universidade de Vigo. 412 pp. [not seen]

 Peñas, A., E. Rolán, and B. Sabelli, 2020. The family Pyramidellidae in the Red Sea I. The tribe Chrysallidini. Iberus 38 (supplement 8): 1-93 incl. Figs. 1-45.