Benthosema parafibulatum, Lin & Wu & Lin & Chien, 2023

Benthosema parafibulatum sp. nov. Lin

Figure 6a–g View Fig

?2019 Benthosema pterotum —Schwarzhans & Ohe: Fig. 5D, E View Fig , non Fig. 5F–J View Fig [ Japan].

?2019 Benthosema aff. fibulatum —van Hinsbergh & Helwerda: pl. 3, Fig. 28, 29 [ Philippines].

2019 Benthosema aff. fibulatum —van Hinsbergh & Helwerda: pl. 3, Fig. 31 [ Philippines].

Holotype ASIZF 0100606 ( Fig. 6a View Fig ), Site 5, mud layer, Tianliao (Kaohsiung), Taiwan. Early Pliocene.

Paratypes Six specimens: four specimens ASIZF 0100607 , 0100610–0100612 ( Fig. 6b, e–g View Fig ), Site 5, mud layer, Tianliao (Kaohsiung), Taiwan ; two specimens ASIZF 0100608 , 0100609 ( Fig. 6c–d View Fig ), Site 5, sand layer, Tianliao (Kaohsiung), Taiwan. Early Pliocene .

Etymology Te species is named after its close relationship (based on otolith morphology) to the extant species Benthosema fibulatum .

Diagnosis OL/OH = 1.15–1.26, OL/OT = 5.22–5.75, OsL/ CaL = 1.00–1.29. Oval otoliths with curved and extended posterior rim. Two strong ventral denticles separated by a smooth gap.

Description Te otoliths are oval-shaped with curved dorsal and ventral rims. Te posterior rim is also curved and extends backward. Tere is a noticeable antero-ventral denticle positioned just before the midline of the otolith, and a stronger, sometimes protruding posterior denticle located at the postero-ventral corner. Tese two denticles are often separated by a smooth gap, and there may be 2 or 3 min denticles between the rostrum and the antero-ventral denticle. Te rostrum is broader than the antirostrum, and both are pointed. An angle is present at the postero-dorsal corner. Te sulcus is well-divided and wide in height, while the ostium is longer than the cauda. Te dorsal area is similar in size to the ventral one.

Remarks Benthosema parafibulatum exhibits otoliths that closely resemble those of modern species B. fibulatum ( Fig. 7a–c View Fig , but see Schwarzhans, 2019a: Fig. 49–1 for an image of a more compact B. fibulatum otolith from Hawaii). Te main differences lie in the lower aspect ratio (1.15–1.26 in B. parafibulatum vs 1.28–1.33 in B. fibulatum ) and less extended posterior rim observed in the fossil species. Te otoliths of B. parafibulatum also differ from those of B. pterotum in having a curved dorsal rim and a more consistent presence of a smooth gap between the two major ventral denticles. A Pliocene otolith previously described as B. aff. fibulatum from the Philippines by van Hinsbergh and Helwerda (2019) can reasonably be assigned to this newly identified species, although another undescribed species with larger dorsal area may also be involved (van Hinsbergh & Helwerda, 2019: pl. 3, Fig. 28, 29).

Occurrence Taiwan: Lower Pliocene Gutingkeng Formation in Chochen (Tainan) and Tianliao (Kaohsiung), southwest Taiwan. Philippines: Upper Pliocene–Lower Pleistocene Santa Cruz Formation in Cabarruyan, northwest Philippines.