Benthosema fibulatum (Gilbert & Cramer, 1897)

Van Hinsbergh, Victor W. M. & Helwerda, Renate A., 2019, Fish Otoliths from the Cabarruyan Piacenzian-Gelasian fauna found in the Philippines, Zootaxa 4563 (3), pp. 401-443 : 411

Benthosema fibulatum (Gilbert & Cramer, 1897)

(Figure 27 and 36–38)

1980 Benthosema fibulatum Schwarzhans W , p.42, fig. 89

1995 Benthosema fibulatum Smale MJ, Watson G, Hecht T, pp. 41–42, plate 16, fig. G1–G3.

1999 Benthosema fibulatum Rivaton & Bourret pl. 105, fig. 1–2

Material: 30 specimens in total. Roxas (3) RGM 962171, 962172, 962349; AndaDeVos (27) 962348, RGM 962345 , RGM 962346 .

One well-conserved adult oval-shaped Myctophid specimen and 29 juvenile specimens were recognized as Bethosema fibulatum . The adult specimen is characterized by a Benthosema -characteristic ventral rim consisting of a blunt massive denticle at the end of the posterior part and 4–6 poorly developed rounded denticles that are restricted to the anterior part of the ventral rim. The dorsal rim is ornamented with regular broad crenulations; it is rather regularly curved with a feeble postdorsal angle and a vertical posterior part. The specimen (OL:OH ratio=1.26) has a OCL/CCL ratio amounting 1.92. A bluntly pointed rostrum exceeds a short antirostrum. There is a distinct but short excisural notch. The inner surface is slightly convex. The outer surface shows ridges and furrows along the ventral and dorsal rims that run perpendicular to the rims, but do not reach the central part. The posterior part of the outer surface is convex and slightly thicker than the anterior part; the transition from anterior to posterior part is slightly concave.

The ventral rim with its robust posterior-ventral denticle is characteristic for otoliths of the genus Benthosema . The relatively high L:H ratio (1.26) and the high OCL/CCL ratio (1.92) fit with the extant Benthosema fibulatum as reported by Rivaton & Bourett (1999) from the Philippines environment. Together with the shape of the mid- and posterior dorsal rim and the typical dentition along the ventral rim this species discriminates from Benthosoma panamense Tåning, 1932 and other Benthosoma species.