常见例句The origin of the mysticete's low-frequency hearing is far murkier, even though the fossil evidence of that group now dates back to as early as 34 million years ago. 虽然就化石记录来看，须鲸在3400万年前（渐新世初期）就出现了，可是牠们的低频听觉起源仍然混沌不明。 返回 mysticete