Colus sekiuensis, Kiel & Goedert, 2007

Kiel, Steffen & Goedert, James L., 2007, New mollusks associated with biogenic substrates in Cenozoic deep-water sediments of Washington State, Acta Palaeontologica Polonica 52 (1), pp. 41-52 : 43-44

Colus sekiuensis sp. nov.

Fig. 3D, E .

2006 Colus sp. ; Kiel and Goedert 2006a: 2626, fig. 2h. 2006 Buccind; Kiel and Goedert 2006b: 550, fig. 2M.

Derivation of the name: After the Sekiu River, near which many of the specimens were found.

Holotype: UWBM 97933 . Complete specimen with 4.5 whorls.

Paratypes: USNM 531404 , from USGS loc. 26898−A.

Type locality.— USGS locality 26898, Murdock Creek , Clallam County, Washington State, USA .

Type horizon: Upper lower Oligocene, lower part of Pysht Formation.

Material.— The type material and several specimens found at the following wood−fall sites: USGS locs. 26896−A, B, D, 26898−A, F, 26899, 26900, 26902, 26903, 26904, 26905. These specimens are deposited in the USNM.

Diagnosis.—Fusiform shell with at least five evenly convex whorls; sculpture of 12–13 subequal, broad, and almost flattopped spiral cords, interspaces narrower than cords; same sculpture on siphonal column; aperture narrow−lenticular; siphonal canal short and twisted to the left.

Description.—Protoconch unknown; suture of teleoconch narrow and incised; in addition to spiral cords the whorls have numerous very fine opisthocyrt growth lines; the inner lip of the aperture is smooth. Height of holotype 23.5 mm, width 10 mm, apical angle ca. 35 °.

Discussion.—This species has a rather generalized buccinid shell. It is placed here in Colus based on its overall similarity with the type species of this genus, but without radula or anatomical data some uncertainty remains. Similar shells are known from Eosipho Thiele, 1929 , but most Eosipho species that we have seen either have additional axial ornament unlike Colus sekiuensis , or are smooth. Warén and Bouchet (2001) mentioned undescribed species of Eosipho from sunken wood in the tropical western Pacific. Also Neptunea Röding, 1798 builds similar shells, for example the Recent Neptunea brevicauda ( Deshayes, 1832) which differs from C. sekiuensis only by its wider aperture and broader spiral cords. A very similar Recent buccind from deep water in the southern hemisphere is Germonea rachelae Harasewych and Kantor, 2004 , which has the same spiral sculpture as C. sekiuensis but a more slender shell.

Two species of Colus have so far been reported from the Paleogene of the Pacific Northwest. A single specimen from the upper Eocene to lower Oligocene Keasey Formation in Oregon was named Colus ? precursor Hickman, 1980. This specimen is slightly smaller than our largest specimens and has fewer but stronger and more erect spiral cords with very deep interspaces ( Hickman 1980a). Kanno (1971) described Colus aff. C. jordani from the lower Oligocene and lowermost Miocene Poul Creek Formation in Alaska. Colus aff. C. jordani differs from Colus sekiuensis in having numerous spiral threads with narrow interspaces, with a shorter and less twisted siphonal canal. On the western side of the North Pacific occurs Colus (Aulacofusus) asagaensis Makiyama, 1934 in Oligocene sediments in Japan, Sakhalin and Kamchatka ( Oleinik 2001), a species in which the spiral ribs are more widely spaced than in C. sekiuensis .

Among the extant species of Colus from the North Pacific Ocean, Colus herendeenii ( Dall, 1902) and C. acosmius ( Dall, 1891) resemble C. sekiuensis regarding sculpture and the twisted siphonal canal, but differ by having less convex whorls and a less pronounced suture ( Abbott 1974: figs. 2298, 2309). A very similar Recent species is C. latericeus Möller, 1842 from the North Atlantic ( Bouchet and Warén 1985).

Neptunea has not been reported from Paleogene sediments in Washington, and the Neogene species all differ from C. sekiuensis by having shouldered whorls ( Nelson 1978). A Neptunea that differs from C. sekiuensis by its broad last whorl and very weak spiral and axial sculpture was reported from the lower Oligocene Katalla district in Alaska ( Oleinik and Marincovich 2003).

Stratigraphic and geographic range.—Uppermost Eocene to uppermost Oligocene, Lincoln Creek, Makah, and Pysht Formations, Washington State, USA.

Figures

Fig. 3. Gastropods from Eocene to Miocene whale− and wood−falls in Washington State. A–C. Neomphalid Leptogyra squiresi sp. nov., from a uppermost Eocene wood−fall at the Satsop River (USGS loc. 26905). A. Holotype USNM 528923 in apertural (A1) and apical (A2) views. B. Protoconch of paratype, USNM 528922. C. Paratype showing shell microstructure, arrows indicate shell pores, USNM 532037. D, E. Buccinid Colus sekiuensis sp. nov. D. Paratype USNM 531404 from a upper lower Oligocene wood−fall at Murdock Creek (USGS loc. 26898−A); D1, sculptural detail; D2, lateral view. E. Holotype UWBM 97933 from a upper lower Oligocene whale−fall at Murdock Creek (USGS loc. 26898) in apertural (E1) and lateral (E2) views.