The Eocene history of cetacean evolution is now represented by the expansive fossil record of archaeocetes elucidating major morphofunctional shifts relating to the land to sea transition, but the change from archaeocetes to modern cetaceans is poorly established. New fossil material of the recently recognized family Eomysticetidae from the upper Oligocene Otekaike Limestone includes a new genus and species, Waharoa ruwhenua, represented by skulls and partial skeletons of an adult, juvenile, and a smaller juvenile. Ontogenetic status is confirmed by osteohistology of ribs. Waharoa ruwhenua is characterized by an elongate and narrow rostrum which retains vestigial alveoli and alveolar grooves. Palatal foramina and sulci are present only on the posterior half of the palate. The nasals are elongate, and the bony nares are positioned far anteriorly. Enormous temporal fossae are present adjacent to an elongate and narrow intertemporal region with a sharp sagittal crest. The earbones are characterized by retaining inner and outer posterior pedicles, lacking fused posterior processes, and retaining a separate accessory ossicle. Phylogenetic analysis supports inclusion of Waharoa ruwhenua within a monophyletic Eomysticetidae as the earliest diverging clade of toothless mysticetes. This eomysticetid clade also included Eomysticetus whitmorei, Micromysticetus rothauseni, Tohoraata raekohao, Tokarahia kauaeroa, Tokarahia lophocephalus, and Yamatocetus canaliculatus. Detailed study of ontogenetic change demonstrates postnatal elaboration of the sagittal and nuchal crests, elongation of the intertemporal region, inflation of the zygomatic processes, and an extreme proportional increase in rostral length. Tympanic bullae are nearly full sized during early postnatal ontogeny indicating precocial development of auditory structures, but do increase slightly in size. Positive allometry of the rostrum suggests an ontogenetic change in feeding ecology, from neonatal suckling to a more specialized adult feeding behaviour. Possible absence of baleen anteriorly, a delicate temporomandibular joint with probable synovial capsule, non-laterally deflected coronoid process, and anteroposteriorly expanded palate suggests skim feeding as likely mode of adult feeding for zooplankton. Isotopic data in concert with preservation of young juveniles suggests the continental shelf of Zealandia was an important calving ground for latitudinally migrating Oligocene baleen whales.

译文

:始新世的始新世历史现在由古细菌的广泛化石记录所阐明,阐明了与陆地向海洋过渡有关的主要形态功能变化,但从古细菌到现代鲸类的变化尚不充分。来自上渐新世Otekaike石灰岩的最近被认识的Eomysticetidae科的新化石材料包括一个新属和种Waharoa ruwhenua,以成年,幼年和较小幼年的头骨和部分骨骼为代表。肋骨的骨组织学证实了个体发育状态。 Waharoa ruwhenua的特征是细长而狭窄的讲台,保留了残留的肺泡和肺泡槽。孔和龈沟仅出现在the的后半部。鼻是细长的,而骨质鼻孔位于很远的前面。巨大的颞窝位于细长的颞间区域附近,具有尖锐的矢状峰。耳骨的特点是保留了内部和外部的后椎弓根,缺乏融合的后突,并保留了一个单独的副小骨。系统发育分析支持将Waharoa ruwhenua包含在单种的Eomysticetidae中,作为最早的无齿神秘菌分支。该线虫类进化枝还包括Eomysticetus whitmorei,Micromysticetus rothauseni,Tohoraata raekohao,Tokarahia kauaeroa,Tokarahia lophocephalus和Yamatocetus canaliculatus。对个体发育变化的详细研究表明,产后矢状和颈uch的隆起,颞间区域的伸长,突的膨胀以及鼻尖长度的成比例增加。鼓膜大疱在产后早期的个体发育过程中几乎全部大小,表明听觉结构的前期发育,但大小确实有所增加。讲台的正向异形体表明,从新生儿哺乳到更专门的成年喂养行为,喂养生态学发生了显着变化。前部可能没有龟头,颞下颌关节细小,可能有滑膜囊,冠状突无侧偏,前pa后膨大,表明脱脂喂养是浮游动物成年喂养的可能方式。同位素数据与未成年幼鱼的保存表明,西兰西亚的大陆架是渐新世渐新世baleen鲸的重要产卵地。

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