Acropoma hanedai Matsubara, 1953

Lin, Chien-Hsiang, Wu, Siao-Man, Lin, Chia-Yen & Chien, Chi-Wei, 2023, Early Pliocene otolith assemblages from the outer-shelf environment reveal the establishment of mesopelagic fish fauna over 3 million years ago in southwestern Taiwan, Swiss Journal of Palaeontology (23) 142 (1), pp. 1-40 : 28

Acropoma hanedai Matsubara, 1953

Figure 16a–b Remarks Acropoma otoliths are not uncommon and quite recognizable by their notable postero-dorsal and mediodorsal angles, nearly straight sulcus, and large ventral area. Te sulcus follows a typical percomorph configuration with well-developed cristae, an oval and short ostium that is mostly filled with a colliculum, and an elongate cauda that bends only slightly ventrally at the tip. Two species, Acropoma hanedai Matsubara, 1953 and Acropoma japonicum Günther, 1859 , are known from Taiwan (Shao, 2023). Te otoliths of these two species can be distinguished based on the shape of the posterior rim in larger specimens. In A. japonicum , the posterior rim is gently curved and exhibits a less pronounced postero-dorsal angle, whereas A. hanedai has a straighter and more vertical posterior rim with a more salient angle, resulting in a more compact otolith outline appearance ( Fig. 17 for comparative figures). Both species have been found in our Gutingkeng collection, but A. hanedai is much rarer compared to A. japonicum .

Figures

Fig. 16 Fish otoliths from the Lower Pliocene Gutingkeng Formation,southern Taiwan. Scale bars =1 mm. Images are inner views unless otherwise indicated. a–b Acropoma hanedai Matsubara, 1953, Site 2, ASIZF 0100686–687.c–d Acropoma japonicum GÜnther, 1859, Site 5, sand layer, ASIZF 0100688–689.e–g Malakichthys sp., Site 2, ASIZF 0100690–692. h Synagrops japonicus (Döderlein, 1883), Site 5, sand layer, ASIZF 0100693.i Serranidae indet., Site 5, sand layer, ASIZF 0100694.j Upeneus sp., Site 2, ASIZF 0100695.1, ventral view; 2, inner view

Fig. 17 Extant Acropoma otoliths from Taiwan. Scale bars =1 mm. Images are inner views. a–d Acropoma hanedai Matsubara,1953, a 29 Aug. 2021, 80.65 mm SL, CHLOL 8683, b 24 Jan. 2021, 106.97 mm SL, CHLOL 2533, c, 19 Feb. 2020, 29.48 mm SL,CHLOL 908, d 29 Jul.2021, 68.94 mm SL, CHLOL 8299. e–h Acropoma japonicum GÜnther, 1859, e, 21 Jan.2022,103.40 mm SL,CHLOL 14810,f 21 Jan. 2022, 146.07 mm SL,CHLOL 14808,g 29 Jul. 2021, 65.95 mm SL, CHLOL 8296, h 21 Jan. 2022, 42.00 mm SL,CHLOL 14800