Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6.
Proc Biol Sci. 2019 Aug 14;286(1908):20191079. doi: 10.1098/rspb.2019.1079. Epub 2019 Jul 31.
Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov. is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.
放射齿动物，一个坎帕多维亚-德文纪的干群节肢动物，传统上被认为是洄游性顶级掠食者。然而，由于化石材料通常是零碎的，放射齿动物的形态和生态的许多方面仍然不清楚。在这里，我们描述了一种新的 hurdiid 放射齿动物，它基于丰富且保存异常完好的化石，来自伯吉斯页岩（加拿大不列颠哥伦比亚省大理石峡谷地区）。Cambroraster falcatus gen. et sp. nov. 的特征是一个特大的马蹄形头胸甲，具有明显的后外侧刺状突起，并部分覆盖一个带有八对侧瓣的短躯干。每对额附肢都有五个向内侧弯曲的耙状外肢，装备有一系列向前指向的钩状刺，共同围绕着口腔圆锥体。这种取食器官表明了一种微到大型的滤食性底栖食性。Cambroraster 照亮了 Hurdiidae 的进化，并证明了这些大型和专门的洄游底栖肉食动物在寒武纪大爆发后对多样化的底栖动物的利用。
