Restudy of fossil specimens of Sinaechinocyamus (Echinoidea; Scutelloida) with new occurrences from Taiwan

Sinaechinocyamus is a small echinoid genus that belongs to Scutelloida. From the perspective of fossil evidence, Sinaechinocyamus may have first appeared in the northern part of Taiwan since the late Miocene and gradually distributed to southern Taiwan in the late Pliocene. The extant population of Sinaechinocyamus mai distributes in the coastal area from Hsinchu to Tainart in Taiwan. In previous research, three fossil Sinaechinocyamus species in Taiwan were described. In this study, a total of 321 fossil and extant specimens of Sinaechinocyamus spp. were collected from 9 sites. Subsequent morphological analyses were conducted to reclassify the specimens, which confirmed that the morphological differences of fossil data fell within the range of extant S. mai. Therefore, these fossils specimens of Sinaechinocyamus spp. found in Taiwan should be classified as S. mai.