生物卵化石研究进展简述

卵生是动物界最普遍的繁殖方式,卵的孵化对繁殖季节突发的气候变化响应敏感,孵化成败又与生物种群数量变动和群落演替密切相关,因此卵化石具有重要的古生物学、古气候学、古生态学研究价值。但由于卵生动物种类十分丰富,卵形态特征多样,研究领域广泛,有必要总结梳理卵化石的研究进展。本文通过对主要卵生动物类群卵的形态特征,以及卵化石在古生物学、古气候学、古生态学方面研究进展的回顾,发现卵化石的研究主要集中在脊椎动物类群,为脊椎动物演化提供了重要证据,但是由于脊椎动物卵化石通常难以建立连续的长序列记录,其古生态学和古气候学研究极为不足。然而,无脊椎动物卵化石由于数量丰富,具有统计意义,其在古生态学、古气候学研究领域具有重要意义,但是其在古生物学,包括种属鉴定等方面的研究需要加强。在无脊椎动物中,蜗牛及其卵化石在黄土-古土壤地层中保存丰富且地层分布连续,最有可能建立卵化石的长序列。通过现代过程研究,明确蜗牛卵的气候指示意义,建立第四纪蜗牛卵化石长序列,发挥蜗牛卵化石的古气候学和古生态学研究价值,是亟需开展的研究工作。

Brief review on the research advancement in fossil eggs

Background, aim, and scope Oviparous animals accounted for more than 90% of the total animal species, and therefore oviparity is the most common reproductive type. Egg hatching is sensitive to seasonal abrupt climate change occurring during breeding seasons, and hatching success or failure is closely related to population dynamics and community succession. Therefore, eggs are a promising multi-discipline research record in paleoclimatology, paleoecology and paleontology. With the diversity of eggs and numerous research advancement, it is necessary to review the advancement of research in fossil eggs. Materials and methods Previous research on fossil eggs are summarized and reviewed. The advantages and potential value of fossil snail eggs are highlighted. Results The researches on fossil eggs mainly focus on vertebrate groups, which provides important evidence for the evolution of vertebrates. However, fossil eggs of vertebrates rarely form long and continuous sequences in the strata. Therefore, it is almost impossible through studies of vertebrate eggs to decipher the influence of climate change on the evolution of oviparous animals and on the succession of oviparous animal communities through time during geological past. Different from oviparous vertebrate, oviparous invertebrates generally can lay abundant eggs and so their eggs can continuously distribute in stratigraphy. Discussion This provides a great potential for reconstructing long sequences of eggs. Among oviparous invertebrates, snails and their eggs are the most abundant fossil in the Quaternary Chinese loess deposits. Therefore, snail eggs can be used to establish long and continuous egg sequences spanning numerous glacial-interglacial cycles, with the potential to provide novel understandings. Conclusions invertebrate eggs are likely used to decipher the impact of climate change on organism through time on long timescales, among which eggs of snail are most abundant. In order to fully explore the paleoclimatological and paleoecological significances of fossil snail eggs, it is urgent to clarify the implication of snail eggs to seasonal abrupt climate events, and to establish the long sequence of Quaternary fossil snail eggs, so as to reveal the change processes and characteristics of seasonal abrupt climate events during glacial-interglacial cycles. Most fossil snails are extant, which provides the opportunities to understand the climatic implications of their eggs through field observations and culturing experiment. Hopefully, the combination of studies on modern and geological processes will provide accurate interpretation of the Quaternary fossil egg changes. Recommendations and perspectives Fossil eggs are particularly useful in paleontology, paleoclimatology and paleoecology. Long time-series of eggs are rare. Systematic study of fossil eggs from one of the most abundant oviparous invertebrates, snails, based on both experimental and field investigations, is expected to establish long sequence of fossil eggs and yield new findings.