Thermal History of Cambrian Burgess Shale-Type Deposits:New Insights from the Early Cambrian Chengjiang and Qingjiang Fossils of South China

Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.

Kaili Biota: A Taphonomic Window on Diversification of Metazoans from the Basal Middle Cambrian: Guizhou, China

A Burgess Shale-type biota is, in part, characterized by a wide diversity of taxa and soft-part preservation. Each provides unique historical insights into early metazoan evolution. Among the more than 40 globally distributed biotas, the early Cambrian Chengjiang and Middle Cambrian Burgess-type biotas are the largest. The Kaili Biota, from the earliest Middle Cambrian of Guizhou, China, contains representatives of 110 metazoan genera belonging to 10 phyla. It contains many well-persevered soft-bodied specimens. This Chinese biota has become the third most taxonomically diverse Burgess Shale-type fauna. Because the Kaili Biota formed in an outer-shelf environment, its main faunal character is large numbers of eocrinoids and planktoic trilobites. The Kaili is younger than the Chengjiang Biota but older than the Canadian Burgess Shale Biota; it shares 30 genera with the Chengjiang and 38 genera with the Burgess Biota. The Kaili Biota displays a taphonomic window to the diversification and evolution of marine offshore organisms covering 5.13 million years between the Early and Middle Cambrian.

Priapulid worms from the Cambrian of China shed light on reproduction in early animals

In the recent years,exceptional fossil sites have revealed astonishing details on the anatomy,lifestyles and behaviour of Cambrian animals but surprisingly,very little is known about one of their most vital features,reproduction.We describe here in situ eggs(clusters of 3 to 30 oocytes)in the tube-dwelling priapulid worm Paraselkirkia sinica from the Cambrian Stage 3 Xiaoshiba Lagerstätte(ca.514 Ma,South China).These oocytes were accommodated within paired tubular ovaries located in the posterior half of the primary body cavity as in modern meiobenthic priapulid worms,thus indicating that the general organization of female tubular gonads in priapulid worms has remained virtually unchanged for half a billion years.Our findings provide for the first time,key information on the reproductive organs and strategies of early ecdysozoans,a huge animal clade that dominated Cambrian marine ecosystems and accounts for a large part of today’s biodiversity(e.g.arthropods).Moreover,we also emphasize the critical role of ecology on the reproductive strategies and lifestyles of both modern and Cambrian worms.

Biodiversity and taphonomy of the Early Cambrian Guanshan biota,eastern Yunnan

The Guanshan biota from eastern Yunnan(Cambrian Series 2,early Stage 4) is a Burgess Shale-type fossil biota with abundant exceptionally preserved soft-bodied fossils after the discovery of the well-known Cambrian Chengjiang fauna and Kaili biota in South China.The geological settings,sedimentology,taphonomy,and the fossil assemblage of the Guanshan biota are briefly summarized here.The Guanshan biota consists of about 60 taxa belonging to more than 10 metazoan groups and algae,among which the lobopods,eldonids,hyolithids with helens,and green algae are reported for the first time.The common occurrence of soft-bodied preservation in many groups,notably the trilobites and brachiopods,makes the Guanshan biota a significant fossil lagersttte for understanding the metazoan evolution during Cambrian explosion and taphonomy of the Burgess Shale-type fossils.

湖北中部寒武纪早期石龙洞组布尔吉斯页岩型生物群的发现

文章简要报道湖北中部京山县郊发现的一个布尔吉斯页岩型生物群,该生物群由大量三叶虫、腕足类、软舌螺及少量鳃曳动物、双瓣壳节肢动物、非三叶虫节肢动物和棘皮动物等组成。文中重点描述非三叶虫节肢动物Clypecaris?和棘皮动物Sinoeocrinus,两者分别为澄江动物群和凯里生物群的典型分子。依据生物地层学证据,该生物群的时代大致为寒武纪第四期晚期(龙王庙期),与凯里生物群下部组合基本相当,稍晚于云南东部的关山动物群和峡东地区石牌组的布尔吉斯页岩型生物群。该发现进一步丰富了华中地区早-中寒武世化石库的资料,扩大了布尔吉斯页岩型生物群的地理分布,并是目前已知唯一的分布在扬子地台北缘的该类型生物群,这对寒武纪环扬子地台古生态的重建和多门类后生生物的演化都将提供重要资料。