A new fossil species supports an early origin for toothed whale echolocation
A new fossil species supports an early origin for toothed whale echolocation
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DOI：
10.1038/nature13086
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发表时间：
2014-04-17
期刊：
影响因子：
64.8
通讯作者：
Carew, James L.
中科院分区：
文献类型：
--
作者：
Geisler, Jonathan H.;Colbert, Matthew W.;Carew, James L.
齿鲸（齿鲸、海豚和鼠海豚）利用回声定位在黑暗浑浊的水生环境中捕猎和导航；关键的适应依赖于与声纳相同的原理(1)。在回声定位的脊椎动物中，齿螈是独一无二的，它们在发声唇处发出高频声音，在鼻孔下方的鼻腔通道处收缩，然后使用空气窦和瓜来调节它们的传播（2,3）。齿状突似乎有回声定位（2,4）；然而，这种复杂的行为究竟是何时以及如何进化的，以及其潜在的解剖学结构，在很大程度上是未知的。在这里，我们报告了一具齿齿龙化石，年代渐新世（大约28万年前），来自南卡罗莱纳（Cotylocara macei, gen. et sp. 11 .），它具有几个提示回声定位的特征：密集、厚实且向下的喙部；气囊窝；脑不对称;和特别宽的上颌骨。我们的系统发育分析将子叶鲸置于齿形鲸的基础分支中，这使我们推断在渐新世早期，齿形鲸从滤食性鲸的祖先（神秘鲸）分化出来后不久，回声定位的基本形式就进化出来了。随之而来的是调节回声定位的面部肌肉的扩大，这反过来又导致了子叶目祖先颅骨形状的显著、趋同的变化，并导致了现存齿齿目动物的谱系。
Odontocetes (toothed whales, dolphins and porpoises) hunt and navigate through dark and turbid aquatic environments using echolocation; a key adaptation that relies on the same principles as sonar(1). Among echolocating vertebrates, odontocetes are unique in producing high-frequency vocalizations at the phonic lips, a constriction in the nasal passages just beneath the blowhole, and then using air sinuses and the melon to modulate their transmission(2,3). Allextant odontocetes seem to echolocate(2,4); however, exactly when and how this complex behaviour-and its underlying anatomy-evolved is largely unknown. Here we report an odontocete fossil, Oligocene in age (approximately 28 Myr ago), from South Carolina (Cotylocara macei, gen. et sp. nov.) that has several features suggestive of echolocation: a dense, thick and downturned rostrum; air sac fossae; cranial asymmetry; and exceptionally broad maxillae. Our phylogenetic analysis places Cotylocara in a basal clade of odontocetes, leading us to infer that a rudimentary form of echolocation evolved in the early Oligocene, shortly after odontocetes diverged from the ancestors of filter-feedingwhales (mysticetes). This was followed by enlargement of the facial muscles that modulate echolocation calls, which in turn led to marked, convergent changes in skull shape in the ancestors of Cotylocara, and in the lineage leading to extant odontocetes.