中国寒武纪软舌螺动物系统分类学、解剖学及埋藏学研究

Hyoliths are a large, diverse, and rather enigmatic group of benthic motile and extinct marine invertebrates known worldwide from Paleozoic strata. They are especially diverse in Cambrian deposits, and constitute an important group of early, biomineralising metazoans. Hyoliths are usually known as simple conical shells, and the lack of other important skeletal and anatomical information tend to hinder systematic work, and to render speculative their biomechanics, palaeoecology and other aspects. Cambrian strata of China yield abundant and well-preserved hyolith fossils. To date, most of previous documentations mainly focus on systematic work, but many early-described hyolith taxa were based on poorly preserved material, which remains the validity of these taxa in question. . This project will focus on the systematics, anatomy and taphonomy of the Cambrian hyolith from both South and North China. The strata includes: in ascending order, the Zhujiaqing, Shiyantou, Yu’anshan, Hongjingshao and Wulongqing formations in Yunnan Province; the Balang Formation in Guizhou Province; the Mantou, Zhangxia and Gushan formations in Shandong Province; and the Mantou Formation in Hebei Province. Besides traditional palaeontologic methods, morphometrics, cladistics, geobiodiversity database and paleobiology database will also be applied to the systematic work, and to contribute to a better understanding of the evolutionary history of hyolith and the interaction with ecosystem through Cambrian. Taphonomic work plays an important role as offering insights into the living habitat and postmortem stories of hyoliths, and it is a way to access to the palaeoecologic reconstruction. In addition, we will also carry out intense work on the hyoliths with soft parts that yield from the exceptionally preserved lagerstätte. Information from the internal anatomy will be used to reconstruct the biologic nature of the hyolith and to interpret its affinity.

软舌螺动物是一类古生代全球广布的海洋表生底栖无脊椎动物，始现于寒武纪初期，灭绝于二叠纪末期。该类群化石常以简单锥壳保存且软体信息较少，造成其在各方面研究进展缓慢。中国寒武系发育，在碎屑岩及碳酸盐相中均产有大量软舌螺化石，但以往工作多以传统分类学研究为主，且大多早期建立属种的模式标本保存不佳，造成其分类的有效性一直存在争议。本项目将利用华南及华北寒武系保存的大量软舌螺类化石标本，采用定量古生物学及分支分类学等方法开展系统分类研究，弄清寒武纪各时期、各产区软舌螺类组成面貌、分异度及地层延限等特征，分析软舌螺各类群间的演化关系，以及在寒武纪各时期演化发展规律，揭示生态环境变化对其身体构型的影响。对各层位产出的软舌螺化石进行埋藏学研究，重塑其埋藏和生活环境。此外，本项目还针对华南及华北寒武纪主要特异埋藏化石库中具软体保存的标本开展软舌螺类的解剖学研究，为其在动物演化谱系树中的位置提供依据。

软舌螺动物是古生代地层中常见类群，始现于寒武纪纽芬兰世幸运期，绝灭于二叠纪末期，在寒武纪尤为繁盛，是最早具有矿化骨骼的两侧对称动物之一，也是研究早期后生动物起源与演化的重要类群。由于该类群多保存较差且缺乏软体信息，使其研究程度较低，亲缘关系一直存有争议，生物学及古生态学等方面仍然知之甚少，是一类亟待深入研究的重要类群。.针对以上问题，本研究以寒武纪第3期云南澄江生物群、第3/4期华北辛集和侯家山组、第4期贵州杷榔动物群及第4/5期河北馒头组中保存较好的软舌螺动物为研究对象进行了详细研究，并取得了相应进展：.（1）亲缘关系：澄江生物群中首次发现具肉茎保存的软舌螺新类群Pedunculotheca diania gen. et sp. nov.，为底栖固着滤食动物，其固着结构与腕足动物肉茎极为相似。基于54个冠轮动物属种及225个形态特征数据的谱系分析，软舌螺动物为单系群，属于腕足动物干群，二者均由寒武纪早期出现的托莫特壳类演化而来。.（2）壳壁结构及埋藏特征：河北馒头组发现的Decoritheca cyrene背部壳壁中具有保存较好的成排瘤点状结构，与外层壳壁内表面凹痕相对应。新种Cupitheca convexa sp. nov.的口盖保存有凹点结构、壳体保存有纤维状纹层结构，均可与其他冠轮动物对比。此外，根据标本保存特征及矿物特征分析，可识别出两种埋藏方式：风暴诱发的密度流导致的快速沉积和埋藏速率较慢的背景沉积。.（3）古生态学：口盖与锥壳绞合的软舌螺动物富集于粪便（澄江生物群标本）及吐卓虫尸体上及周围（杷榔生物群标本），表明该类群以粪便流体相、尸体及微生物膜为食，将有机碎屑转化为生物量带入到食物网中，是生态系统中重要的能量转换器。.（4）分类学：对华北辛集及侯家山组中的软舌螺动物进行了分类学研究和系统厘定，共识别出10属14种，包括2新属、3新种：Conotheca australiensis、Cupitheca holocyclata、C. costellata、Neogloborilus applanatus、N. spinatus、Tegminites hymenodes、Triplicatella disdoma、T. xinjia sp. nov.、Paratriplicatella shangwanensis gen. et sp. nov、Prot