Sutton M D, Briggs D E, Siveter D J, Siveter D J
Earth Sciences Department, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
Nature. 2001 Mar 22;410(6827):461-3. doi: 10.1038/35068549.
Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerstätte is a Silurian (about 425 Myr bp) deposit that preserves a marine biota in remarkable three-dimensional detail. The external surface of even non-biomineralized cuticle was preserved by entombment in volcanic ash, subsequent incorporation into concretions, and infilling of the fossils with sparry calcite. Here we describe, from this deposit, a complete vermiform mollusc, which we interpret as a plated aplacophoran. Serial grinding at intervals of tens of micrometres, combined with computer-based reconstruction methods, renders the fossils in the round.
对软体动物的起源和辐射的研究尚未解决许多关于它们最近的亲属、系统发育和祖先特征的问题。多板纲动物（石鳖）和无板纲动物被广泛认为是现存最原始的软体动物，但前者的下古生代化石缺乏软躯体部分，而后者迄今未被识别为化石。赫里福德郡化石库是一个志留纪（约4.25亿年前）的沉积物，它以非凡的三维细节保存了一个海洋生物群。即使是非生物矿化的角质层的外表面也通过被火山灰掩埋、随后被纳入结核以及用亮晶方解石填充化石而得以保存。在此，我们描述了来自该沉积物的一种完整的蠕虫状软体动物，我们将其解释为有板无板纲动物。每隔几十微米进行连续研磨，并结合基于计算机的重建方法，使化石呈现出立体形态。
