德国斯图加特州立自然历史博物馆Eli Amson研究团队发现，重量级的早期鲸鱼挑战脊椎动物形态学的极限。该项研究成果于2023年8月2日在线发表在《自然》杂志上。

研究人员描述了秘鲁始新世中期的一种朝龙王鲸（Perucetus colossus）。它的骨骼质量增加程度是迄今所知最高的，这是一种与浅潜有关的适应性。据估计，巨鲸的骨骼质量超过了任何已知的哺乳动物或水生脊椎动物。这项研究表明，水生哺乳动物的骨骼结构特化反映在整个羊膜类动物的骨骼比例（骨骼质量与全身质量之比）上。研究人员使用骨骼分数来估算P. colossus的体重，事实证明它是有记录以来最重动物称号的竞争者。在初级生产力特别高的沿海地区，鲸目动物的体重峰值已经比之前假设的时间早了约3000万年。

据悉，鲸目动物的化石记录记录了陆生动物如何获得极端适应性并过渡到完全水生的生活方式。在鲸类中，这与最大体型的大幅增加有关。虽然鲸目动物在演化早期就已经有了拉长的身体，但须鲸的最大体型反映了最近的多样化，最终形成了蓝鲸。更广泛地说，迄今已知的水生四足动物中的巨型动物是在浮游、活跃的游泳者中演化而来的。

附：英文原文

Title: A heavyweight early whale pushes the boundaries of vertebrate morphology

Author: Bianucci, Giovanni, Lambert, Olivier, Urbina, Mario, Merella, Marco, Collareta, Alberto, Bennion, Rebecca, Salas-Gismondi, Rodolfo, Benites-Palomino, Aldo, Post, Klaas, de Muizon, Christian, Bosio, Giulia, Di Celma, Claudio, Malinverno, Elisa, Pierantoni, Pietro Paolo, Villa, Igor Maria, Amson, Eli

Issue&Volume: 2023-08-02

Abstract: The fossil record of cetaceans documents how terrestrial animals acquired extreme adaptations and transitioned to a fully aquatic lifestyle1,2. In whales, this is associated with a substantial increase in maximum body size. Although an elongate body was acquired early in cetacean evolution3, the maximum body mass of baleen whales reflects a recent diversification that culminated in the blue whale4. More generally, hitherto known gigantism among aquatic tetrapods evolved within pelagic, active swimmers. Here we describe Perucetus colossus—a basilosaurid whale from the middle Eocene epoch of Peru. It displays, to our knowledge, the highest degree of bone mass increase known to date, an adaptation associated with shallow diving5. The estimated skeletal mass of P. colossus exceeds that of any known mammal or aquatic vertebrate. We show that the bone structure specializations of aquatic mammals are reflected in the scaling of skeletal fraction (skeletal mass versus whole-body mass) across the entire disparity of amniotes. We use the skeletal fraction to estimate the body mass of P. colossus, which proves to be a contender for the title of heaviest animal on record. Cetacean peak body mass had already been reached around 30million years before previously assumed, in a coastal context in which primary productivity was particularly high.

DOI: 10.1038/s41586-023-06381-1

Source: https://www.nature.com/articles/s41586-023-06381-1