homocercalyoudaoicibaDictYouDict[homocercal 词源字典]
"(Of a fish’s tail) appearing outwardly symmetrical but with the backbone passing into the upper lobe, as in all higher fish", Mid 19th century: from homo- 'same' + Greek kerkos 'tail' + -al.[homocercal etymology, homocercal origin, 英语词源]