Data from: Mandible allometry in extant and fossil Balaenopteridae (Cetacea: Mammalia): the largest vertebrate skeletal element and its role in rorqual lunge-feeding

AbstractRorqual whales (crown Balaenopteridae) are unique among aquatic vertebrates in their ability to lunge-feed. During a single lunge, rorquals rapidly engulf a large volume of prey-laden water at high speed, which they then filter to capture suspended prey. Engulfment biomechanics are mostly governed by the coordinated opening and closing of the mandibles at large gape angles, which differentially exposes the floor of the oral cavity to oncoming flow. Mouth area in rorquals is delimited by unfused bony mandibles that form kinetic linkages to each other and with the skull. The relative scale and morphology of these skeletal elements have profound consequences for the energetic efficiency of foraging in these gigantic predators. Here we performed a morphometric study of rorqual mandibles using a dataset derived from a survey of museum specimens. Across adult specimens of extant balaenopterids, mandibles range in size from ~1-6 m in length, and at their upper limit they represent the single largest osteological element of any vertebrate, living or extinct. Our analyses determined that rorqual mandibles exhibit positive allometry, whereby the relative size of these mandibles becomes greater with increasing body size. These robust scaling relationships allowed us to predict mandible length for fragmentary remains (e.g., incomplete and/or fossil specimens), as we demonstrated for two partial mandibles from the latest Miocene of California, U.S.A., and for mandibles from previously described fossil balaenopterids. Furthermore, we showed the allometry of mandible length to body size in extant mysticetes, which hints at fundamental developmental constraints in mysticetes despite their ecomorphologic differences in the feeding styles. Lastly, we outlined how our findings can be used to test hypotheses about the antiquity and evolution of lunge-feeding., Usage notesFig5AC_mandibleThis file is a nexus file that uses log-transformed museum specimens from the first dataset (mature specimens only) to regress C-C against by Cu and Ch (mandible measurements) using PICs. See main text for details on tree source.Supplemental DataWord document that provides full institutional abbreviations in the morphometric dataset; results on PICs of extant morphometric data; and predictive equations for estimating complete mandibles and body size in extinct balaenopterids.Fig6_CHvTLThis file is a nexus file that uses log-transformed museum specimens from the second dataset (mature and immature specimens only) to regress Ch (mandible measurements) against TL using PICs for all extant Mysticeti. See main text for details on tree source.Mandibles MS dataset_R1_finalSpecimen-based morphometrics for both datasets (first and second) used in the analyses. See main text for details.

摘要
鳁鲸类（crown Balaenopteridae）是水生脊椎动物中唯一具备冲吞摄食（lunge-feed）能力的类群。单次冲吞过程中，鳁鲸会以高速快速吞入大量携带有猎物的海水，随后通过滤食获取悬浮的猎物。冲吞过程的生物力学主要由下颌骨（mandibles）在大张口角度下的协同开合控制，该过程会使口腔底部差异化地暴露于迎面而来的水流中。鳁鲸的口部区域由未愈合的骨性下颌骨界定，这些下颌骨彼此之间以及与颅骨之间形成运动连接。这些骨骼结构的相对尺寸与形态，对这类巨型捕食者的觅食能量效率有着深远影响。本研究基于对博物馆标本的调查所构建的数据集，开展了鳁鲸下颌骨的形态测量学研究。在现生鳁鲸科物种的成年标本中，下颌骨长度范围约为1~6米，其上限尺寸堪称现生及已灭绝脊椎动物中最大的单块骨学结构。本研究分析结果显示，鳁鲸下颌骨呈现正异速生长（positive allometry），即其相对尺寸会随躯体尺寸的增大而增加。这些稳健的尺度缩放规律使得我们能够通过碎片化遗骸（如不完整标本或化石标本）预测下颌骨长度，正如我们对美国加利福尼亚州晚中新世的两件部分下颌骨标本，以及此前已记述的化石鳁鲸科物种下颌骨所展示的那样。此外，我们还证实了现生须鲸亚目（Mysticeti）物种下颌骨长度与躯体尺寸间的异速生长关系，这暗示尽管须鲸亚目类群在摄食方式上存在生态形态学差异，但它们仍受到根本性的发育约束。最后，我们阐述了本研究结果可用于验证关于冲吞摄食起源与演化的相关假说。
使用说明
Fig5AC_mandible 该文件为NEXUS格式文件，基于第一数据集（仅成熟标本）的对数转换后博物馆标本数据，通过系统发育独立对比（phylogenetic independent contrasts, PICs）以Cu和Ch（下颌骨测量指标）对C-C进行回归分析。关于数据集来源树的详细信息，请参见正文。
补充数据：该Word文档包含形态测量数据集中的完整机构缩写说明、现生标本形态测量数据的系统发育独立对比分析结果，以及用于估算已灭绝鳁鲸科物种完整下颌骨长度与躯体尺寸的预测方程。
Fig6_CHvTL 该文件为NEXUS格式文件，基于第二数据集（仅成熟与未成熟标本）的对数转换后博物馆标本数据，针对所有现生须鲸亚目（Mysticeti）物种，通过系统发育独立对比以TL为因变量、Ch（下颌骨测量指标）为自变量进行回归分析。关于数据集来源树的详细信息，请参见正文。
Mandibles MS dataset_R1_final 该数据集包含本研究分析所用的两套数据集（第一与第二数据集）的标本基态形态测量数据。详细信息请参见正文。