1Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2 Canada.
2Department of Natural History-Palaeobiology, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 2C6 Canada.
Commun Biol. 2019 May 3;2:164. doi: 10.1038/s42003-019-0388-4. eCollection 2019.
Phylogenomic studies have greatly improved our understanding of the animal tree of life but the relationships of many clades remain ambiguous. Here we show that the rare soft-bodied animal from the Cambrian of Canada and China, which has variously been considered a chaetognath, a nemertine, allied to molluscs, or a problematica, is related to gnathiferans. New specimens from the Burgess Shale (British Columbia, Canada) preserve a complex pharyngeal jaw apparatus composed of a pair of elements with teeth most similar to gnathostomulids. demonstrates that primitive spiralians were large and unsegmented, had a coelom, and were probably active nekto-benthic scavengers or predators. Secondary simplification and miniaturisation events likely occurred in response to shifting ecologies and adaptations to specialised planktonic habitats.
系统发生基因组学研究极大地提高了我们对动物生命树的认识，但许多进化枝的关系仍然不清楚。在这里，我们表明，来自加拿大和中国寒武纪的罕见软体动物，曾被认为是毛颚动物、纽形动物、软体动物的近亲，或疑难动物，与有颚类动物有关。来自伯吉斯页岩（加拿大不列颠哥伦比亚省）的新标本保存了一个复杂的咽部颚器，由一对带有牙齿的元素组成，与颚口动物最相似。这项研究表明，原始的螺旋动物是大型的、不分节的，具有体腔，可能是积极的底栖或掠食性的浮游生物清道夫。次生的简化和微型化事件可能是对生态变化的反应，并适应了专门的浮游生物生境。
