Chengjiang Biota Research Articles

Appendages of early Cambrian Eoredlichia (Trilobita) from the Chengjiang biota, Yunnan, China

ABSTRACTThe early Cambrian Chengjiang biota in Yunnan, southern China has yielded many articulated exoskeletons of the spiny redlichiid trilobite Eoredlichia intermedia, of which some have their appendages exceptionally well preserved. Both of the paired uniramous antennae of a medium-sized holaspis consist of 46–50 short segments (articles), each of which bears a fine spine near its inner edge. Behind the antennae there are twenty-one pairs of biramous limbs: three pairs are situated underneath the cephalon, one pair underneath each of the fifteen thoracic segments, and probably three pairs underneath the small pygidium. The endopod consists of a broad basis and seven podomeres, of which the last is divided into three terminal spines. The exopod is blade-like, and according to one interpretation, is dorsally hinged to the basis of the endopod; an alternative suggestion being that both the endopod and exopod are split from the basis, the latter being independent and not forming part of the endopod. The exopod has a prominent anterior rim, and possesses about forty long filaments along the posterior margin, and short setae along the rounded distal lobe. The basic appendage features of the redlichiid trilobites, and likewise the gut, are comparable to those of other known Cambrian polymerid trilobites that belong to more distantly related clades.

Analysis of Fossilised Eye systems and its Relevance to Palaeobiology

This article presents an overview of current research work, concerned with the analysis of fossilised eye systems. Besides the investigation of these sophisticated eyes in terms of the physical rules and optical principles they have to obey, it is possible by comparison with Recent systems to assign their owners to defined ecological conditions and life styles. This is demonstrated, exemplarily, in the tiny trilobite Ctenopyge ceciliae Clarkson & Ahlberg 2002, as well as in representatives of the Chengjiang Fauna from the lower Cambrian of China, surely one of the most important Lagerstatten to demonstrate the importance of vision in early evolutionary development.

The LobopodOnychodictyonfrom the Lower Cambrian Chengjiang Lagerstätte Revisited

Onychodictyon ferox, from the Lower Cambrian Chengjiang Lagerstatte, is a worm-like armored lobopod with 10 pairs of dorsal plates and a pair of probable sensory appendages (“antennae”). Newly discovered complete specimens show that Onychodictyon is represented by two species: O. ferox with a “head” bearing a pair of dorsal “antennae” and a trunk with 11 pairs of limbs, whereas O. gracilis has a blunt anterior end without any appendages and a trunk with 12 pairs of limbs. Because of the close resemblance of the “antennae” of O. ferox and those of the lobopod Miraluolishania, they are considered to be homologous structures. The “antennae” of Cambrian lobopodians are proposed to be homologous with the arthropod antennulae.

Gill rays of primitive vertebrate Yunnanozoon from Early Cambrian: a first record

Yunnanozoans (including Yunnanozoon and Haikouella) are important representatives of the primitive vertebrates in the Early Cambrian Chengjiang fauna. For Yunnanozoans, we know less about Yunnanozoon than about Haikouella due to the poor preservation of Yunnanozoon. Up to now, there have been some reports that Haikouella had developed gill rays, while there have been no reports on Yunnanozoon. In this paper, we described our new findings of the distinct gill rays of Yunnanozoon lividum based on new well-preserved material collected from the Lower Cambrian Maotianshan Shale in Xiaolantian of Yunnan Province, China. This study provides new data on the evolutionary relationship of the primitive vertebrates and their early evolution.

New Record of Palaeoscolecids from the Early Cambrian of Yunnan, China

Abstract:A new palaeoscolecid,Guanduscolex minorHu, Luo et Fu gen. et sp. nov., with preserved soft parts of introvert and intestines comes from the Lower Cambrian Guanshan fauna of Yunnan, South China. Microstructural details of the cuticle revealed by scanning electron microscopy (SEM) show that each annulation bears three rows of plates and each plate bears 9–10 marginal and 4–5 central nodes. This discovery sheds new light on the relationships and evolutionary pathway of the palaeoscolecids and other early priapulids.

SHRIMP U-Pb zircon age of tuff at the bottom of the Lower Cambrian Niutitang Formation, Zunyi, South China

A SHRIMP U-Pb zircon geochronology study of the tuff at the bottom of the Lower Cambrian Niutitang Formation at Songlin, Zunyi, South China yielded a mean 206Pb/238U age of 518±5 Ma. It is significantly younger than the Re-Os ages of 537–542 Ma for the overlying polymetallic Ni-Mo-PGE-rich layer in the basal Niutitang Formation at Songlin, suggesting that the Re-Os ages might represent that of the original magma chamber for the Ni-Mo-PGE-rich layer rather than the formation age of the strata. The intra-basinal stratigraphic correlation also implies that the absolute age of the Chengjiang biota should be younger than 518±5 Ma. Our new result, together with the SHRIMP U-Pb zircon age for the K-bentonite in the Zhongyicun member of the Zhujiaqing Formation at the Meishucun section, Yunnan Province, provides a temporal constraint for the Lower Cambrian of the Yangtze Platform in South China.

Cambrian Burgess Shale–type deposits share a common mode of fossilization

Although Cambrian Burgess Shale–type (BST) biotas are fundamental to understanding the radiation of metazoans, the nature of their extraordinary preservation remains controversial. There remains disagreement about the importance of the role of early mineral replication of soft tissues versus the conservation of primary organic remains. Most prior work focused on soft-bodied fossils from the two most important BST biotas, those of the Burgess Shale (Canada) and Maotianshan Shale (Chengjiang, China). Fossils from these two deposits do not provide ideal candidates for specimen-level taphonomic study because they have been altered: the Burgess Shale by greenschist facies metamorphism and the Maotianshan Shale by intensive subsurface weathering. Elemental mapping of soft-bodied fossils from 11 other BST deposits worldwide demonstrates that BST preservation represents a single major taphonomic pathway that may share a common cause wherever it occurs. The conservation of organic tissues, and not early authigenic mineralization, is the primary mechanism responsible for the preservation of BST assemblages. Early authigenic mineral replacement preserves certain anatomical features of some specimens, but the preservation of non-biomineralized BST fossils requires suppression of the processes that normally lead to the degradation of organic remains in marine environments.

The Earliest Annelids: Lower Cambrian Polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland

Apart from the Phyllopod Bed of the Burgess Shale (Middle Cambrian) polychaete annelids are practically unknown from any of the Cambrian Lagerstatten. This is surprising both because their diversity in the Burgess Shale is considerable, while to date the Chengjiang Lagerstatte which is equally impressive in terms of faunal diversity has no reliable records of any annelids. Here we describe, on the basis of about 40 specimens, Phragmochaeta canicularis gen. et sp. nov. from the Lower Cambrian Sirius Passet Lagerstatte of Peary Land, North Greenland. This makes it by far the oldest known polychaete, with a likely age of lower to middle Atdabanian, The body consists of approximately 20 segments, each bearing notochaetae and neurochaetae. The former appeared to have formed a felt-like covering on the dorsum, whilst the neurochaetae projected obliquely to the longitudinal axis. Apart from minor differences in chaetal size at either end there is no other tagmosis. Details of the head are obscure, and presence of palps, tentacles and eyes are conjectural. Jaws appear to have been absent. The gut was straight, and flanked by massive longitudinal musculature. P. canicularis was evidently benthic, propelling itself on the neurochaetae, with the dorsal neurochaetae conferring protection. Its stratigraphic position and generalized appearance are consistent with P. canicularis being primitive, but the phylogenetic relationships within the polychaetes remain problematic, principally because of paucity of relevant morphological information.

Comparative study of Cambrian lobopods Miraluolishania and Luolishania

The rare fossil Miraluolishania described by Liu et al. from the Lower Cambrian Chengjiang Lagerstatte in 2004 is regarded as an arthropod sphinx because it bears mosaic features of both lobopods and arthropods. The discovery of this rare transitional form offers direct fossil evidence for exploring the relationship between lobopods and arthropods. However, some scientists consider Miraluolishania to be a junior synonym of Luolishania because the former superficially resembles the latter in general appearance. Considering the significant differences between the two taxa, a thorough comparative study of Miraluolishania and Luolishania leads to the conclusion that there are definitely two different genera. Nevertheless, the “Luolishania” of the Haikou area is indeed “Miraluolishania”, whereas Luolishania is most likely the typical genus of the Maotianshan area of Chengjiang County.

EVIDENCE OF PRIAPULID SCAVENGING FROM THE EARLY CAMBRIAN CHENGJIANG DEPOSITS, SOUTHERN CHINA

Abstract A Laojieella specimen of the Lower Cambrian Chengjiang Lagerstatte in Yunnan Province, southern China, contains a tubular organism inside its digestive tract. The gut content appears to resemble Archotuba conoidalis, a sessile animal generally regarded as being closely related to cnidarians. This example demonstrates that Laojieella might be a scavenger. Reasons for the extreme paucity of recognizable remains in gut contents are discussed. Such fossils offer new insights into the reconstruction of the complex food web of the benthic community of the Chengjiang fauna.

Isotopic dating of the Chengjiang Fauna-bearing horizon in Central Yunnan Province, China

Twenty black shale samples, which are free from the influence of weathering, were collected from the Chengjiang Fauna-bearing horizon, central Yunnan Province, yielding a Pb-Pb isochron age of 534±60 Ma. Although this age is younger than both the Rb-Sr isochron age and 40Ar-39Ar age, it should represent the lower isotopic age limit of the Chengjiang Fauna.

A preliminary note on the dispersal of the Cambrian Burgess Shale-type faunas

The common or similar elements of faunas shared by the Early Cambrian Chengjiang fauna and the Middle Cambrian Burgess Shale fauna are listed in a generic level so as to have a better understanding of the palaeogeographic relationship between the South China Block and Laurentia. The Burgess Shale-type faunas probably had a worldwide distribution during the interval ranging from the Late Tommotian to Atdabanian. The geographic and biological contributions to the cosmopolitan geographic distribution of the Burgess Shale-type faunas are discussed. However, newly developed pelagic larvae in many phyla, which probably acquired their first bloom in the Cambrian, might have promoted the dispersal.

Community palaeoecology of the early Cambrian Maotianshan Shale biota: Ecological dominance of priapulid worms

The early Cambrian soft-bodied Maotianshan Shale (Chengjiang) biota of Yunnan Province, China provides a critical glimpse of animal life during the heart of the Cambrian radiation. The Shankou biota is the focus of this current work, and 9963 specimens from it have been examined and tallied. This collection of fossils represents a time-averaged assemblage of unknown duration from a 10-meter thick sequence. The predominantly benthic community recovered from this section is presumably autochthonous. This community was buried through several hundred millimeter to centimeter thick burial events. Only specimens interpreted as buried alive, based on either soft-part preservation or fully articulated skeletons, were counted. Algae were too fragmented to be counted. To avoid including synonymous species, diversity was evaluated at the genus level. A total of 57 genera from 9 phyla, encompassing 14 ecological groups, were found in this assemblage. The results reveal that the three most abundant genera comprise 43.2% of all specimens: the tubiform priapulid worm Paraselkirkia (16.0%), the diminutive priapulid worm Sicyophorus (14.3%), and the brachiopod Heliomedusa (12.9%). No other genera total more than 9% of specimens. At the phylum level, there is an interesting dichotomy between taxonomic diversity and ecological dominance. The arthropods are the most diverse phylum (37% of genera) and rank second in relative abundance of specimens (26.3%). The priapulids, however, with only 17.5% of genera is the most abundant group in the assemblage (43.2%). All other phyla, excluding brachiopods (19.6%), represent only 10.9% of the assemblage. Because of their sheer numerical abundance, this study indicates that priapulid worms may have exerted more influence on energy flow and community structure than other phyla in this particular trophic web. This result contrasts strongly with both traditional views of Maotianshan Shale biota palaeoecology, which often claimed arthropod dominance based solely on taxonomic diversity, and the palaeoecology of modern priapulids, which are relegated to marginal marine settings. This result also demonstrates the importance of collecting quantitative relative abundance data when performing palaeoecological investigations.

Early Cambrian radiation of brachiopods: A perspective from South China

Brachiopods, a group of benthic suspension-feeding marine invertebrates, made their first appearance in the Lower Cambrian. In the Yangtze Platform (South China), well-exposed Lower Cambrian stratigraphic succession represents shallow to deeper water environments. Strata from eastern Yunnan, southern Shaanxi and the Yangtze gorges areas of western Hubei Province, deposited in muddy-siltstone and carbonate lithofacies, contained an abundant variety of brachiopods, including all the representatives of the subphylum Linguliformea and the calcareous-shelled genera of Kutorgina and Nisusia from the subphylum Rhynchonelliformea. Thus the fossil assemblage bears witness to the first major phase of evolutionary radiation of brachiopods during the ‘Cambrian explosion’ interval of metazoans. Brachiopods from the celebrated Chengjiang fauna have exquisitely preserved soft-tissues, which reveal the body plans and evolutionary acquisition of morphological novelties of the early stocks, and also provide a good opportunity for testing the analogies with the stem groups from the extant representatives. These fossils have corroborated the view that brachiopods developed complex organization of tissues, and achieved considerable evolutionary success already by the onset of ‘Cambrian Explosion’. Thus it is not improbable that a large part of this radiation occurred within, or only just before early Cambrian time. Studies of Chengjiang brachiopods suggest that attachment by a pedicle to the substrate was probably the most common relationship of Cambrian brachiopods with the substrate where they inhabited.

Skara hunanensis a new species of Skaracarida (Crustacea) from Upper Cambrian (Furongian) of Human, south China

Abstract The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world, but it was not until 2005 that the Orsten-type fossils represented by Skaracarida and Phosphatocopida were first reported to be found in western Human, South China. Here, we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaracarida. They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section, western Human, south China, assigned to a new species Skara hunanensis herein. Skara hunanensis is characterized by small, soft-integumented, marine forms with slender, annulate body; labrum large and ventrocaudally directed; uniramous antennulae; biramous antennae and mandibulae; maxillas and maxillipeds of the same shape; all postantennular limbs join a short cephalic filter apparatus. The body has tow tagmata: a cephalon with five pairs of well developed appendages and a trunk composed of 11 ring-shaped conical segments. *Supported by National Natural ...

GRAVITATIONAL CONSTRAINTS ON THE BURIAL OF CHENGJIANG FOSSILS

The soft-bodied Chengjiang fossils show great potential for assessing the forces operating during the burial process, particularly subtle gravitational effects that are often overlooked. Evidence from gravitational sorting is consistent with the assumption that most Chengjiang organisms underwent local transport. Based on an examination of 1295 specimens and orientation frequency data, we found that the Chengjiang animals followed hydrostatic rules and obtained equilibrium during the burial process, resting regularly on bedding planes rather than randomly, as seen in the Burgess Shale. Specific gravity could be one of crucial factors determining the burial orientation of these organisms, even before normal compaction occurs during early diagenesis.

Discoveries of new Longfengshaniaceae from the uppermost Ediacaran in eastern Yunnan, South China and the significance

A morphologically more diverse assemblage of Longfengshaniaceae has been found in the uppermost Ediacaran (Sinian) Jiucheng Member, Yuhucun Formation at Jinning and Jiangchuan, eastern Yunnan, South China. A majority of them are different from the Longfengshania found in the Neoproterozoic Changlongshan Formation, Yanshan Mountain area, North China and the Little Dal Group, North America. They are mainly characterized by a more varied, often thallus-like appearance with no branches, such as oval, pyriform, spindle, shovel, heart, ribbon and balloon shapes, and more sturdy stalk-like projection (stipe) with a smooth connection on the basal part of the thallus. In addition, they appear to have a remarkable attaching organ of lanceolate, shuttle-like or short stem-like structure at the base of the stipe. Six distinct morphological taxa are recognized, including one new genus, two new species and three conformis species. The characteristics of the family and the genus Longfengshania are further discussed in this paper. The new discoveries of these carbonaceous macrofossils identified as Longfengshaniaceae algae on the basis of the diagnostic forms and anastomosis patterns of their thalli and stipes demonstrate that an important evolutionary radiation of metaphytes took place in the last Ediacaran stage. The flourishing of the benthonic thallophytes attached to the substrate from eastern Yunnan and considered to be photosynthetic alga probably provided continuous nutritional habitats for the explosion and diversification of the Early Cambrian “Chengjiang biota”.

중국 운남성 부근에서 발견된 초기 캄브리아기 청지앙동물군

최근 캄브리아기 초기에 해당하는 동물군 화석이 중국 운남성 부근에서 다량 발견되었다. 이 동물군 화석은 5억 2천만 년 전에서 5억 2천 5백만 년 전의 연대를 가진 마오탕샨 셰일에서 산출되며, 캐나다 로키의 버제스셰일동물군과 그린란드의 시리우스파세트동물군보다 약 1천만년 내지 2천만년 더 오래된 동물군으로 판단된다. 청지앙동물군은 아주 다양한 동물 화석으로 구성되며, 몸체의 약한 부분이 잘 보존되어 있다. 이러한 조건은 유수, 생란 작용, 생화학 작용을 받지 않는 환경 즉 반복된 빠른 퇴적작용에 의해서 화석화된 것이다. Recently lots of the Early Cambrian fauna were described from the Yunnan Province of China. The fauna occurs from the Maotiangshan shale that dated between 525 and 520 ma, which is about 10-20 million years earlier than the Burgess Shale fauna of Canadian Rocky Mountain and Sirius Passet fauna in North Greenland. The Chengjiang fauna comprises an extremely diverse faunal assembly, and soft body parts of the fauna are well preserved. Such condition probably resulted from repeated rapid burial environment that prevented the bodies from destruction by currents, bioturbation, and biolchemical activities.

Diverse pelagic predators from the Chengjiang Lagerstätte and the establishment of modern-style pelagic ecosystems in the early Cambrian

New information obtained from exceptionally preserved nonmineralized fossils in the Chengjiang Lagerstätte indicates the presence of diverse pelagic predators in the early Cambrian, including ctenophores ( Maotianoascus octonarius Chen and Zhou, Trigoides aclis Luo and Hu, Botafasciculus ramificans Hou et al., and a new species, Yunnanoascus haikouensis gen. et sp. nov.), chaetognaths ( Protosagitta spinosa Hu = Eognathacantha ercainella Chen and Huang), eldoniids ( Stellostomites eumorphus Sun and Hou, and Rotadiscus grandis Sun and Hou), and epipelagic nektonic arthropod predators (e.g., Isoxys), as well as some meroplankton (e.g., Anomalocaris and Amplectobelua). Trophic analysis of the early Cambrian pelagic community of the Chengjiang Biota reveals a phytoplankton-based food web with a complex trophic structure containing at least three (probably four) trophic levels. A complex, modern-style pelagic ecosystem may have been developed by the time of early Cambrian.

Raman spectra of a Lower Cambrian ctenophore embryo from southwestern Shaanxi, China

The Early Cambrian (approximately 540 million years old) Meishucun fossil assemblage of Ningqiang County (Shaanxi Province), China, contains the oldest complex skeletonized organisms known in the geological record. We here report the finding in this assemblage of an exquisitely preserved late-stage embryo of a ctenophore ("comb jelly"), its fine structure documented by confocal laser scanning microscopy and shown by Raman spectroscopy to be composed of carbonaceous kerogen permineralized in apatite. In its spheroidal morphology, the presence of eight comb rows and the absence of tentacles, this embryo resembles an adult ctenophore (Maotianoascus octonarius) known from the immediately younger Chengjiang fauna of Yunnan, China. The oldest ctenophore and the only embryonic comb jelly known from the fossil record, this exceptionally well preserved specimen provides important clues about the early evolution of the phylum Ctenophora and of metazoans in general.