The modern sperm whales Kogia and Physeter (superfamily Physeteroidea) represent highly disparate, relict members of a group of odontocetes that peaked in diversity during the middle to late Miocene. Based on a highly informative specimen (including the cranium with ear bones, mandibles, teeth and some postcranial elements) from the lower Miocene (early Burdigalian, 19–18 Ma) of the Chilcatay Formation (Pisco Basin, Peru), we describe here a new genus and species of physeteroid, Rhaphicetus valenciae gen. et sp. nov. The latter is one of the geologically oldest physeteroids. This medium-sized species (estimated body length between 4.7 and 5.7 m) differs from all other physeteroids by the following, probably autapomorphic, features: a narrow, cylindrical rostrum comprising nearly 75% of the condylobasal length; the two main dorsal infraorbital foramina located posterior to the antorbital notch; an upper tooth count of at least 36 teeth per quadrant; and anterior-most upper alveoli filled by thick bony pads. Our phylogenetic analysis recovers R. valenciae as one of the earliest branching stem physeteroids. The highly unusual filling of the anterior upper alveoli by bony pads is interpreted as part of a mechanism leading to the loss of apical and subapical upper teeth. By comparison with other odontocetes displaying some degree of anterior reduction of the dentition, this condition may have corresponded to the rostrum being anteriorly longer than the mandible. The elongated rostrum with a circular cross-section, the long temporal fossa, and the high number of slender, pointed upper and lower teeth all suggest that R. valenciae used its dentition to grasp relatively small prey, possibly via rapid movements of the head. On the one hand, this new Peruvian record increases our knowledge of the morphological disparity of sperm whales during the Miocene. On the other hand, it may provide clues to the ancestral morphotype for all physeteroids.

http://zoobank.org/urn:lsid:zoobank.org:pub:3E1CEFC8-0F23-416E-9C02-03750D7199BA

现代的抹香鲸Kogia和Physeter（超家族Physeteroidea）代表着一组完全不同的遗骸成员，在中新世中期至中后期多样性达到顶峰。基于Chilcatay组（秘鲁皮斯科盆地）下中新世（早Burdigalian，19-18 Ma）的高信息量标本（包括带有耳骨，下颌骨，牙齿和一些颅后元素的颅骨），我们在此描述一个类新物种，类根瘤菌，Rhaphicetus valenciaegen。等。十一月 后者是地质上最古老的类胡萝卜素之一。这种中等大小的物种（估计体长在4.7至5.7 m之间）与所有其他类不同之处在于以下特征，可能是自发形的：狭窄的圆柱形讲台，占nearly基部长度的近75％。位于眶缘切口后方的两个主要的眶下眶孔; 每个象限的上齿数至少为36齿；最上端的肺泡充满厚厚的骨垫。我们的系统发育分析恢复了瓦伦西亚芽孢杆菌作为最早的分支茎类甾醇之一。骨垫高度不寻常地填充前上牙槽被解释为导致根尖和根尖缺失的机制的一部分。通过与显示出一定程度的前牙减小的其他牙菌突相比较，这种情况可能对应于前额比下颌长。带有圆形横截面的细长的讲台，较长的颞窝以及大量细长的，尖的上，下齿，都表明瓦氏芽孢杆菌用它的牙列来抓住相对较小的猎物，可能是通过头部的快速移动。一方面，这项新的秘鲁记录增加了我们对中新世期间抹香鲸形态差异的认识。另一方面，它可能为所有类eter提供祖先形态型的线索。

http://zoobank.org/urn:lsid:zoobank.org:pub:3E1CEFC8-0F23-416E-9C02-03750D7199BA