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首页> 外文期刊>Journal of Paleontology >First remingtonocetid archaeocete (Mammalia, Cetacea) from the middle Eocene of Egypt with implications for biogeography and locomotion in early cetacean evolution
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First remingtonocetid archaeocete (Mammalia, Cetacea) from the middle Eocene of Egypt with implications for biogeography and locomotion in early cetacean evolution

机译：始于埃及中始新世的第一个remingtonocetid古生菌（哺乳动物，鲸类），对鲸类早期演化中的生物地理学和运动产生了影响

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Remingtonocetidae are Eocene archaeocetes that represent a unique experiment in cetacean evolution. They possess long narrow skulls, long necks, fused sacra, and robust hind limbs. Previously described remingtonocetids are known from middle Eocene Lutetian strata in Pakistan and India. Here we describe a new remingtonocetid, Rayanistes afer, n. gen. n. sp., recovered from a middle to late Lutetian interval of the Midawara Formation in Egypt. The holotype preserves a sacrum with four vertebral centra; several lumbar and caudal vertebrae; an innominate with a complete ilium, ischium, and acetabulum; and a nearly complete femur. The ilium and ischium of Rayanistes are bladelike, rising sharply from the body of the innominate anterior and posterior to the acetabulum, and the acetabular notch is narrow. These features are diagnostic of Remingtonocetidae, but their development also shows that Rayanistes had a specialized mode of locomotion. The expanded ischium is larger than that of any other archaeocete, supporting musculature for powerful retraction of the hind limbs during swimming. Posteriorly angled neural spines on lumbar vertebrae and other features indicate increased passive flexibility of the lumbus. Rayanistes probably used its enhanced lumbar flexibility to increase the length of the power stroke during pelvic paddling. Recovery of a remingtonocetid in Egypt broadens the distribution of Remingtonocetidae and shows that protocetids were not the only semiaquatic archaeocetes capable of dispersal across the southern Tethys Sea.
机译：Remingtonocetidae是始新世的古细菌，代表了鲸类进化的独特实验。它们拥有长长的狭窄头骨，长长的脖子，融合的sa骨和健壮的后肢。从巴基斯坦和印度的始新世中期鲁特斯人地层中已知先前描述的雷米科球虫。在这里，我们描述了一个新的雷米科动物，Rayanistes afer，n。 gen。 。 sp。，从埃及Midawara组的Lutetian中期到后期恢复。完整型保留一个ac骨，具有四个椎骨中央。几个腰和尾椎骨;具有完整的i骨，坐骨和髋臼的无名动物;和几乎完整的股骨。 Rayanistes的i骨和坐骨呈刀片状，从无名的前，后身体到髋臼急剧上升，并且髋臼切口狭窄。这些特征可诊断出Remingtonocetidae，但它们的发展也表明，Rayanistes具有专门的运动方式。扩张后的坐骨比其他任何古生菌都大，支持肌肉组织在游泳过程中后肢的强力回缩。腰椎后方倾斜的神经棘和其他特征表明腰椎的被动柔韧性增加。 Rayanistes可能利用其增强的腰部柔韧性来增加骨盆戏水期间中风的时间。在埃及，雷蒙顿球菌的恢复扩大了雷蒙顿球菌的分布，并表明原生动物不是唯一能够在特提斯海南部扩散的半水生古细菌。

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