Elongatolucina sp.

Gill, Fiona L. & Little, Crispin T. S., 2013, A new genus of lucinid bivalve from hydrocarbon seeps, Acta Palaeontologica Polonica 58 (3), pp. 573-578 : 576

Elongatolucina sp. aff. E. elassodyseides Saul, Squires, and Goedert, 1996

Fig. 4.

2005 Vesicomyid sp. B; Gill et al. 2005: fig. 9B.

Material.— Nine specimens from BNHM localities 13968 and 17345, Miocene Huso Member , Pozon Formation, Falcon State, Venezuela .

Description.—The shell is very similar in shape to E. elassodyseides , i.e., elongate and elliptical with a straight ventral margin, and has a maximum length of 135 mm. The hinge plate is long and narrow with no teeth or sockets. There is a shallow, triangular−shaped depression underneath the umbo, which extends further to the posterior than the anterior, and causes a deflection in the ventral margin of the hinge plate. The anterior margin of this depression is bounded by a sharp ridge. The anterior adductor muscle scar is elongate and detached from the pallial line with an angle of divergence of approximately 40 °. The pedal retractor muscle scar is separate. The pallial line is entire and immediately dorsal to it are a series of digitations. A series of radial striations is clearly visible in the area between the pallial line and the shell margin. The posterior adductor muscle scar is reniform and has a cleft in its anterior margin. Radial striations extend from the umbo to the shell margin and are stronger in the anterior and posterior margins, and weaker in the centre of the shell. Those in the anterior portion, dorsal to the anterior adductor muscle scar have distinct pustules. The radial striations also pass across the adductor muscle scars.

Remarks.—Although they are morphologically very similar, there are a number of differences between the Venezuelan specimens and the type specimens of E. elassodyseides that means we do not presently feel confident in stating that they are conspecific. Additional well preserved specimens from Washington State or Venezuela may resolve this issue. The morphological differences are as follows. On average the Venezuelan specimens are larger than those of E. elassodyseides , although there is some overlap in size ( Fig. 2 ). The shape of the posterior adductor muscle scar is distinctive in the Venezuelan material but cannot be fully discerned in any of the E. elassodyseides specimens examined. Further, none of the Venezuelan specimens has any original shell material preserved, therefore no information is available on features such as shell thickness or external ornament.

Geographic and stratigraphic range.—Miocene, Huso Member, Pozon Formation, Venezuela (BNHM localities 13968 and 17345).

Figures

Fig. 2. Plot of length versus height data for Elongatolucina elassodyseides, E. sp. aff. Elassodyseides, and Elliptiolucina magnifica holotype.