Data from: Spinosity, regeneration, and targeting among Paleozoic crinoids and their predators

Evolving interactions between predators and prey constitute one of the major adaptive influences on marine animals during the Paleozoic. Crinoids and fish constitute a predator-prey system that may date back to at least the Silurian, as suggested by patterns of crinoid regeneration and spinosity in concert with changes in the predatory fauna. Here we present data on the frequency of breakage and regeneration in the spines of the Middle Devonian camerate Gennaeocrinus and Late Paleozoic cladids, as well as an expanded survey of the prevalence of spinosity and infestation by platyceratid gastropods on crinoid genera during the Paleozoic. Spine regeneration frequency in the measured populations is comparable to arm regeneration frequencies from Mississippian Rhodocrinites and from modern deep-water crinoid populations. The prevalence of spinosity varies by taxon, time, and anatomy among Paleozoic crinoids; notably, spinosity in camerates increased from the Silurian through the Mississippian and decreased sharply during the Pennsylvanian, whereas spines were uncommon in cladids until their late Mississippian diversification. Among camerates, tegmen spinosity is positively correlated with the presence of infesting platyceratids. These results allow us to evaluate several hypotheses for the effects of predation on morphological differences between early, middle, and late Paleozoic crinoid faunas. Our data corroborate the hypothesis that predators targeted epibionts on camerate crinoids and anal sacs on advanced cladids, and suggest that the replacement of shearing predators by crushing predators after the Hangenberg extinction affected the locations of spines in Mississippian camerates.

捕食者与猎物间的协同演化互动，是古生代（Paleozoic）海洋动物适应性演化的核心驱动因素之一。海百合（Crinoids）与鱼类构成的捕食者-猎物系统，其起源至少可追溯至志留纪（Silurian），这一推论得到海百合再生模式、棘刺发育特征与捕食者群落变迁协同一致的佐证。本文报道了中泥盆世（Middle Devonian）全壳海百合亚纲（Camerate）Gennaeocrinus属，以及晚古生代分枝海百合亚纲（Cladida）的棘刺破损与再生频率数据，并扩展调查了古生代海百合属类群的棘刺发育普遍程度，以及扁盖螺科（Platyceratidae）腹足类（gastropods）的寄生侵染情况。所测得种群的棘刺再生频率，与密西西比纪（Mississippian）Rhodocrinites属的腕足再生频率，以及现代深海海百合种群的再生水平相当。古生代海百合的棘刺发育普遍程度因类群、地质时代与解剖结构而异；值得注意的是，全壳海百合亚纲的棘刺发育率从志留纪至密西西比纪持续上升，却在宾夕法尼亚纪（Pennsylvanian）骤降，而分枝海百合亚纲的棘刺在密西西比纪晚期辐射演化前极为罕见。在全壳海百合亚纲中，口盖（tegmen）棘刺发育程度与寄生扁盖螺类的存在呈正相关。上述结果使我们得以评估多项关于捕食作用对古生代早、中、晚期海百合群落形态差异影响的假说。本研究数据证实了捕食者靶向取食全壳海百合亚纲体表附生生物、以及高级分枝海百合亚纲肛囊的假说，并表明杭格贝格灭绝（Hangenberg extinction）事件后，以粉碎型捕食者取代剪切型捕食者，对密西西比纪全壳海百合亚纲的棘刺分布模式产生了影响。