Minycardita Hoare & Plas, 2003

Vendrasco, Michael J., Hoare, Richard D. & Bell, Gorden L., 2010, The youngest rostroconch mollusc from North America, Minycardita capitanensis n. sp., Zootaxa 2603, pp. 61-64 : 62

Minycardita Hoare & Plas, 2003

Type species. Minycardita sectilis Hoare & Plas, 2003 , by original designation.

Diagnosis. Minycardita is unique among members of Pseudobigaleaidae in having an elongate, swollen main body chamber, sub-circular in dorsal view, that is bordered by weak primary carinae (the two ridges from the apex to the postero-lateral edges on both sides of the shell).

Remarks. Classification within the Pseudobigaleaidae at the genus and species level can be difficult because the representative genera ( Hadropipetta Hoare, Mapes, & Yancey, 2002 ; Baiosoma Hoare, Mapes, & Yancey, 2002 ; Minycardita Hoare & Plas, 2003 ; and Exalloschema Hoare, Mapes, & Yancey, 2002) each contain only one or two species that are themselves known from only a few well-preserved specimens. In addition, there appears to be high levels of intraspecific variation within these species [e.g., variation in relative body length, angle of primary carina, ornamentation, and connection of rostrum (tube) to posterior surface in Baiosoma pala ( Hoare, Steinker, & Mapes, 1988): fig. 7-13)]. Baiosoma and Minycardita share a number of characters, including: rostral clefts (tension cracks around the base of the rostrum), the same range of concavity of posterior margin, the same relative proportion of height to length, and same chamber shape and size in side view. However, in addition to the characters listed in the diagnosis, Minycardita also differs from Baiosoma in having a denticulate ventral portion of anterior gape, ornamentation of more prominent radial ridges with less distinct comarginal growth lines, smaller and shallower concavity around posterior rostrum, smaller diameter of rostrum relative to overall height where it attaches at the posterior face, and typically more convex (versus straight) ventral surface just in front of the carina.