寒武纪幸运期陕西宽川铺生物群疑难化石装饰玲珑球发育生物学

Developmental biology of a problematic taxon,Linglongsphaera ornata n.gen.n.sp.,from the Kuanchuanpu Biota(Fortunian,Cambrian),Shaanxi,China

作为磷酸盐化特异埋藏微体化石库,寒武纪宽川铺生物群保存了大量软躯体动物胚胎和成体、藻类和多门类小壳化石,为理解寒武纪大爆发初期的生物圈提供了重要的埋藏窗口。但前人的研究主要聚焦以橄榄蛋(Olivooides)为代表的刺细胞动物和以始祖动吻虫(Eokinorhynchus)等蠕虫为代表的蜕皮动物化石,对化石库中大量疑难类群的探索尚有不足。本文报道了宽川铺生物群中一类新发现的疑难化石装饰玲珑球Linglongsphaera ornata n.gen.n.sp.。装饰玲珑球整体呈球状,直径在544—1088μm之间,表面具瘤状突起装饰,内部由平均直径24μm的细胞组成。处于不同发育阶段的装饰玲珑球发育有8到180余个数量不等的腔室,单个腔室的体积随着腔室数量的增长先增加而后减小,分布的位置也从周缘直至布满整个内部,最终腔室总体积占个体总体积的36%左右后保持稳定。根据现有证据,笔者推测装饰玲珑球可能代表了一类已经灭绝的具有多细胞发育阶段的真核生物,可能与某些多细胞藻类有较近的亲缘关系,但具体的系统分类位置仍然不明。该研究为理解宽川铺生物群化石组合面貌和寒武纪大爆发初期生物圈的组成提供了新的线索。

The Kuanchuanpu Biota(535 Ma;Fortunian,Cambrian)represents an exceptionally phosphatized fossil Lagerstätte,yielding abundant fossils of embryonic and adult soft-bodied animals,small shelly fossils,and algae.This biota serves as a crucial taphonomic window for unraveling the marine ecosystem during the very beginning of the Cambrian Explosion.However,previous studies have primarily focused on well-known groups such as the cnidarians represented by Olivooides and the ecdysozoans represented by scalidophorans(e.g.,Eokinorhynchus),leaving numerous enigmatic taxa of this fossil assemblage uninvestigated.This study reports a newly discovered enigmatic fossil taxon,Linglongsphaera ornata n.gen.n.sp.,from the Kuanchuanpu Biota.This taxon is characterized by a spherical body with its diameter ranging from 544 to 1088μm.Its surface is ornamented with nodular projections,and its interior consists of cells with an average diameter of 24μm.During different developmental stages,Linglongsphaera ornata exhibits a variable number of chambers ranging from 8 to over 180.The volume of an individual chamber increases at the beginning and then gradually decreases as the overall number of chambers increases.The chambers are distributed from the periphery to throughout the interior,with the total volume of chambers being stabilized at approximately 36%of the total volume of the organism body.Based on available evidence,we propose that Linglongsphaera ornata may represent an extinct multicellular eukaryote,with possible close affinity to multicellular algae.However,its precise classification and phylogenetic position remain uncertain.This discovery contributes to a more comprehensive understanding of the diverse and enigmatic taxa of the Kuanchuanpu Biota,and sheds light on the complex early Cambrian biosphere during the Cambrian Explosion.