早寒武世宽川铺生物群中Punctatus卵裂胚胎化石的发现及其意义

陕南早寒武世宽川铺生物群中保存了大量磷酸盐化动物胚胎化石和小壳化石.在已报道的这些胚胎化石中, 主要是囊胚期之后不同发育阶段的胚胎化石标本, 缺少卵裂期胚胎化石材料.报道了从宽川铺生物群中新发现的多枚从4分细胞、64分细胞、128分细胞、512分细胞到千分级细胞的卵裂期胚胎化石, 以及大量囊胚期、原肠胚期和不同孵化幼体阶段的化石标本, 他们共同构成了从单个细胞(Olivooides)经卵裂到囊胚、原肠胚, 再到孵化的锥形幼体(Punctatus)的完整胚胎发育序列.从卵裂子细胞数量的变化、形态的变化、排列方式及囊胚腔形态等特征, 基本上可与贵州瓮安生物群(地质时代为伊迪卡拉纪Ediacaran)中卵裂细胞化石对比.同时也可与一些现生的低等动物卵裂胚胎对比.新化石材料的发现, 不仅填补了宽川铺生物群中卵裂期胚胎化石的空白, 而且对揭示Olivooides胚胎的卵裂过程和特点, 探讨其亲缘关系, 以及后生动物的早期演化都具有十分重要的科学意义. 

Discovery of Cleavage Punctatus Embryos Fossils from Early Cambrian Kuanchuanpu Biota

The rich phosphatized embryo fossils and a large number of small shelly fossils were found from Early Cambrian Kuanchuanpu biota in the southern Shaanxi Province. So far, only embryonic fossils of the different development stages after blastosphere have been found in the embryo fossils previously reported, with the absence of fossils of transgene embryo. This paper presents many new specimens of cleavage embryos fossils in Kuanchuanpu biota, ranging from four cells, 64 cells, 128 cells, 512 cells to classification of cells without embryo fossils of cells, as well as a number of fossil specimens developed during blastosphere period, the original embryo stage and different bowel hatch larval stage, which constituted the integrated developmental sequence of embryo from single cells (Olivooides) to blastocysts, the original embryo, and then to bowel hatch larval cone (Punctatus). The variations of these cell fossils in numbers, forms, arrangement and blastocysts cavity can be compared to those in the Wen'an biota of Guizhou belonging to Ediacaran. In addition, they can also be compared to the cleavage embryos of living Cnidaria. Here, the fossils found for the first time complement specimens of embryo fossils in Kuanchuanpu biota and reveal developmental process of Olivooides embryos. Moreover, new specimens can also provide evidences to reveal genetic relationship and early evolution of the metazoan.