Crossword clue: having the tail nearly or quite symmetrical, the vertebral column terminating near its base; -- opposed to heterocercal.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
possessing a symmetrical tail that extends beyond the end of the vertebral column (as in most bony fishes)