Hymenocephalus aeger Gilbert & Hubbs, 1920

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 : 421

Hymenocephalus aeger Gilbert & Hubbs, 1920

(Figures 68–69)

2014 Hymenocephalus aeger Schwarzhans W , pp. 58–59, fig. 30

Material: 7 specimens in total. Anda1 (1) RGM 962232; AndaDeVos (3) RGM 962233 , RGM 962234 ; AndaCliff3 (1) RGM 962235 ; Tiep1 (2) RGM 962236 .

Two well-preserved specimens (OL:OH= 0.93–1.00) comply well with the characteristics of members of the genus Hymenocephalus that have a sulcus with a fused colliculum. The dorsal rim has a large moderately broad predorsal lobe that is bordered by two straight and parallel sides and a curved upper rim with four insignificant lobules; accentuated by a small concavity the posterior part runs gradually down towards a posterior point just above a posterior depression of the sulcus. The sulcus is slightly bent, in particular because its posterior part slightly declines to the ventral side. The shape of the colliculum differs between the two specimens. One has a fully fused colliculum with a thin extension towards but not reaching the anterior rim; the fused colliculum of the other specimen still displays that it is a fusion of two collicula. Under the colliculum, both specimens show a large pseudocolliculum. A ventral furrow is hardly visible.

The posterior bluntly pointed part is slightly stronger in the largest specimen, which also has the fully fused colliculum. Notwithstanding, we consider the otoliths conspecific, because of the identity in the shape of the predorsal extension and characteristic shape of the sulcus. Hymenocephalus is encountered in the Indo-Pacific marine milieu ( Schwarzhans, 2014). The specimens have a high similarity to the extant species Hymenocephalus aeger , to which species we consider them to belong. They are reminiscent of H. italicus Giglioni, 1884 , which is known from the Atlantic Ocean and Mediterranean Sea, and H. torvus Smith & Radcliffe, 1912 , and H. striatissimus Jordan & Gilbert, 1904, which dwell in Philippines and Japanese seas, but differ in OL:OH ratio, the shape and ornamentation of the dorsal extension, and curved sulcus.