陕南寒武系下部宽川铺组帽球状化石*

陕南寒武纪早期宽川铺组微体球状化石类型多样,如何正确辨别这些球状化石的生物属性是当前早期生命演化古生物学研究中的一个难点。我们在宽川铺组中发现了一类为数众多,具有一个或者多个不规则的帽状隆起结构以及翻边帽沿的帽状化石。研究表明这些帽状化石均为不完整的个体,其完整形态呈不规则的凹球形。根据帽球状化石帽身的数量和相对位置,这类化石可划分为"单帽型"、"双帽型"和"复帽型"三种类型。这些凹球状化石呈双层壳壁,内壁光滑,外壁粗糙。因为凹球状化石形态及其表面小孔与微体藻类、后生动物的胚胎以及壳体化石差异都非常显著,所以推测这类化石可能与带壳原生动物亲缘关系最为紧密。

A SPHERICAL HAT-SHAPED ORGANISM FROM THE LOWER CAMBRIAN KUANCHUANPU FORMATION

The phosphatized spheroidal fossils preserved in three dimensions from the early Cambrian Kuanchuanpu Formation in south Shaanxi,China,are rather abundant.Generally,they are interpreted as metazoan embryos and microscopic algae,but some of them remain controversial in affinities.Here we report a kind of or sub-spherical shelly fossils characterized by one,two or more deep concaved,hat-shaped structures within a subsphere frame.Most incomplete specimens appear to be hat-shaped structure with a brim on account of taphonomic transportation and abrasion. We subdivided these fossils into single-hat,double-hat and complex hat types. There is no septum between adjacent primary or secondary hat-shaped structures within an individual.The shell wall consists of a smooth inner and a coarse outer layers.The fossil differs from co-occurring algae,metazoan embryos and other shelly metazoans,but is interpreted tentatively here as a tested protozoan.