Philine ornatissima Yokoyama 1927

Philine ornatissima Yokoyama, 1927

Figures 7–8

Philine ornatissima Yokoyama 1927: 408, pl. 46, fig. 6.

Philine sp. 1 Gosliner 1996: 183, figs 2.7D–F, 2.8C–D, 2.9A.

Philine sp. A Cadien 1988: 8 –10, figs. 1–2.

Type material. Holotype (UMUT CM 23626): Tokyo [Pleistocene], not examined.

Other material examined. Off Long Point, Palos Verdes Peninsula, California (3343.42’N, 11824.43’W), 158 m depth, 29 Jul 2008, R/ V Ocean Sentinel (Los Angeles County Sanitation Districts Benthic Monitoring stn. 3B), 1 specimen, 5.5 mm preserved length, leg. Cadien (LACM 178901). Off Double Point, Palos Verdes Peninsula, California (3343.39’N, 11823.08’W), 61 m depth, 10 Jul 2012, R/ V Ocean Sentinel (Los Angeles County Sanitation Districts Benthic Monitoring stn. 4C), 3 specimens, 6–7 mm preserved length, leg. Cadien (LACM 178890). Off Double Point, Palos Verdes Peninsula, California (3343.00’N, 11823.23’W), 150 m depth, 11 Jul 2006, R/ V Ocean Sentinel (Los Angeles County Sanitation Districts Benthic Monitoring stn. 4B), 1 specimen, 12 mm preserved length, leg. Cadien (LACM 178889). Between White Point and Double Point, Palos Verdes Peninsula (33º42.97’N, 118º20.91’W), 32 m depth, 9 Jul 2003, R/ V Ocean Sentinel (Los Angeles County Sanitation Districts Benthic Monitoring stn. 6D), 2 specimens, 5 mm preserved length, leg. Cadien (LACM 178888).

Description. Live animal to 12 mm, uniform pale cream in color. Body very elongate, about 4–5 times as long as wide (Fig. 7 A). Cephalic shield long and narrow, rounded posteriorly. Parapodia running from near the anterior end of the body to the middle of the posterior hump, narrow anteriorly, short and thick posteriorly. Posterior end of the body with two lateral flaps and the apical portion of the shell visible, protruding slightly. Shell to 4 mm, flat, elongate (Fig. 7 B–C). Aperture wide and broad. Outer lip protruding apically, forming a triangular, distinct apical wing. Columella with a projecting rectangular plate near its posterior end. Sculpture composed of very large punctuations arranged in spiral lines (Fig. 7 G). Apical wing with strong striations.

Digestive system with a long and narrow buccal bulb, surrounded anteriorly by the central nervous system (Fig. 8 A). The buccal bulb narrows posteriorly and expands again into an oval esophagus, which connects to the small, muscular gizzard. Gizzard plates (3) oval, elongate, smooth, thicker centrally (Fig. 7 D–E). Radular formula 15 x 2.1.0.1.2. Lateral teeth broad, with large, wide bases and strong curved cusps (Fig. 7 I). Bases with a series of conspicuous denticles on the inner surface. Outer teeth narrow, elongate, lacking denticles (Fig. 7 H).

Reproductive system with a very elongate and convoluted prostate (Fig. 8 B). Penis connected to a long tubular loop. Penis elongate, covered with spines (Fig. 7 F, 8C).

Range. Japan, Russia and California, from Oceano to Point Loma (Fig. 3 A). Depth range 8–222 m.

Remarks. This species was described from Pleistocene fossils collected near Tokyo, Japan. Live animals were subsequently reported from several localities in East Asia and identified as Philine ornatissima based on similarities in shell morphology (Gulbin & Chaban 2009). Chaban (2014) and Chaban & Chernyshev (2014) provided a detailed anatomical description and indicated that the northeastern Pacific specimens referred to as Philine sp. A (Cadien, 1988) and Philine sp. 1 (Gosliner, 1996) belong to the same species. Anatomical examination of northeast Pacific specimens herein revealed striking similarities to the specimens described by Chaban, 2014 and Chaban & Chernyshev, 2014 from Asia. Additionally, the shells of the specimens here examined are similar to the holotype (UMUT CM 23626). Although with the available evidence is impossible to determine with certainty, the northeastern Pacific specimens are here regarded as P. ornatissima until molecular data becomes available to further test this hypothesis.

Habe (1950) introduced the genus Yokoyamaia for this species, based on its unique shell morphology. The anatomy of this species is similar to that of some species included in the Philine aperta clade (Price et al. 2011). In the absence of a phylogenetic analysis is not possible to determine the systematics placement of this species and therefore it is here provisionally regarded as a member of Philine until such a study is conducted.

Another similar species is Philine angulata J. G. Jeffreys, 1867 from the North Atlantic, illustrated by Ohnheiser and Malaquias (2013), which is probably closely related.