Bathymodiolus (sensu lato) palmarensis, Kiel & Campbell & Gaillard, 2010

Kiel, Steffen, Campbell, Kathleen A. & Gaillard, Christian, 2010, New and little known mollusks from ancient chemosynthetic environments, Zootaxa 2390 (1), pp. 26-48 : 39-40

Bathymodiolus (sensu lato) palmarensis sp. nov.

( Fig 8 )

2005 Bathymodiolin; Gill et al. 2005, fig. 9F.

2007 Bathymodiolus ? n. sp.; Kiel and Peckmann 2007, figs. 5E–I.

Diagnosis: Bathymodioline shell with subterminal beak, straight dorsal and ventral margins, and pointed anterior margin.

Holotype: USNM 533981 .

Paratypes: USNM 533982-553984 .

Type locality: USGS locality 11253, Atlantico, Colombia; considered to be of Oligocene age. The original locality description is “¼ mile N of junction Arroyo Piadras Palmar and Palmar-Molinera-Road, Atlantico, Colombia ” and its exact location proved difficult to pin down. The town Arroyo Piadras is at 10°37’N, 75°06’W .

Description: Elongate modioliform shell, slightly inflated but with strong umbonal ridge, beaks in subterminal position; length/height-ratio 1: 2 in smallest specimen, 1:2.5 in largest; surface with strong growth increments; dorsal margin straight, angular transition to posterodorsal margin at about two-thirds of total shell length; posterior margin broadly rounded; ventral margin straight; anterior margin pointed but rounded; hinge unknown, interior of shell with fine radial lines.

Remarks: Many extant species of Bathymodiolus differ from B. (s.l.) palmarensis n. sp. by having a concave ventral margin and by having the beak in a less anterior position. Quite similar to B. (s.l.) palmarensis regarding these two characters is B. azoricus von Cosel, Comtet & Krylova, 1999 , from the Azores Triple Junction on the Mid-Atlantic Ridge, but it differs from that extant species by having a proportionally narrower anterior margin and by a less well-developed umbonal ridge. The same is true for B. brooksi Gustafson, Turner, Lutz & Vrijenhoek, 1998 . The East-Atlantic species B. mauretanicus von Cosel, 2002 , has the beaks in an even more anterior position than B. (s.l.) palmarensis , but is shorter (has a lower height/length ratio), lacks internal radial ridges or striations, and usually has a concave ventral margin. Another species with the beak in an almost terminal position and a lower height/length ratio than B. (s.l.) palmarensis is the Japanese B. platifrons Hashimoto & Okutani, 1994 . The slightly older fossil species Bathymodiolus willapaensis ( Squires and Goedert,1991) from the Eocene and Oligocene of Washington State, USA, also has the beaks in a subterminal position. It differs from B. (s.l.) palmarensis by having a slightly convex and shorter dorsal margin, which occupies only about half of the distance between beak and posterior end, whereas in B. (s.l.) palmarensis the dorsal margin is straight and occupies two-thirds of the distance between beak and posterior end. There are several genetically distinct clades among the species traditionally placed in Bathymodiolus ( Miyazaki et al. 2004; Iwasaki et al. 2006; Jones et al. 2006; Olu et al. 2007), hence we assign palmarensis only to Bathymodiolus (sensu lato).

Distribution: Colombia (Oligocene?) and possibly Venezuela (Miocene).

Etymology: After its occurrence near the Arroyo Piadras Palmar and Palmar-Molinera-Road in Colombia.

Figures

FIGURE 8. Bathymodiolus (s.l.) palmarensis n. sp. from a presumably Oligocene seep carbonate in northern Colombia. A, B. Holotype (USNM 533981), an elongate specimen showing shell remains on the anterior end. C. Smaller specimen (USNM 533982).