Cambrian Of China Research Articles

A new bilaterally injured trilobite presents insight into attack patterns of Cambrian predators.

Durophagous predation in the Cambrian is typically recorded as malformed shells and trilobites, with rarer evidence in the form of coprolites and shelly gut contents. Reporting novel evidence for shell-crushing further expands the understanding of where and when in the Cambrian durophagy was present. To expand the current documentation and present new records of malformed trilobites from the Cambrian of China, we present an injured Redlichia (Pteroredlichia) chinensis from the lower Cambrian Balang Formation, western Hunan, South China. The specimen has two distinct injuries along the thorax. The injuries show different degrees of regeneration, suggesting that the specimen was attacked twice. We propose that the individual may have been targeted more readily for the second attack. This predatory approach would have been highly energy efficient, maximizing net energy gain during the attack.

Restudy of some plectronocerid nautiloids (Cephalopoda) from the late Cambrian of China; discussion on nautiloid evolution and origin of the siphuncle

ABSTRACT The sub-class Nautiloidea is divided into two super-orders, Nautilosiphonata and Calciosiphonata, based on different structural types of the connecting rings. The late Cambrian order Plectronocerida has the calciosiphonate type of connecting ring similar to that in post-Cambrian orthocerids. It is structurally more complex than the nautilosiphonate connecting ring in late Cambrian ellesemerocerid-like nautiloids. The plectronocerid nautiloids, therefore, evolved from the ellesmerocerid-like nautiloids and not vice versa. As indicated by the complex siphuncular structure in plectronocerids, cephalopod evolution began earlier than previously estimated, probably in the early Cambrian. The siphuncle in cephalopods originated from a calcareous septum that became partially non-calcified and formed the connecting ring.

The macroalga Bosworthia from the Cambrian Burgess Shale and Kaili biotas of North America and China

A comprehensive restudy of all material assigned in previous reports to the noncalcified macroalgal genus Bosworthia Walcott from the Burgess Shale Formation (Cambrian Stage 5) of western Canada and the slightly older Kaili Formation of South China, together with investigation of previously unpublished material, indicates important morphological differences between the two species heretofore included within the genus. On the basis of these differences, B. gyges is removed from the genus and assigned to Walcottophycus gen. nov. Most specimens previously assigned to Bosworthia from the Cambrian of China, including those assigned to B. simulans Walcott, are transferred to W. gyges, and it is concluded that Bosworthia remains unknown in China. Morphological details for this material when evaluated in the context of molecular clock studies and other fossil macroalgae indicate that B. simulans may belong to the extant red algal subclass Rhodymeniophycidae (Florideophyceae) and indicate that W. gyges may be an early form of bryopsidalean alga within the Chlorophyta.

Reexamination of Yuknessia from the Cambrian of China and first report of Fuxianospira from North America

AbstractYuknessia Walcott, 1919 recently was transferred from the green algae to the Phylum Hemichordata on the basis of new details observed for the type species, Y. simplex, from the Burgess Shale Formation (Cambrian Stage 5) of British Columbia. This has prompted reexamination of material attributed to Yuknessia from various Cambrian localities in South China. Findings preclude both a Yuknessia and a hemichordate affinity for all of the Chinese study material, and most of this material is formally transferred to Fuxianospira Chen and Zhou, 1997, a taxon common in the Chengjiang biota. Comparable material from the Cambrian Marjum, Wheeler, and Burgess Shale formations of North America is also assigned to Fuxianospira, and this reassignment expands both the paleogeographic and stratigraphic range of this taxon. All aspects of the study specimens, including details obtained from scanning electron microscopy, are consistent with an algal affinity, as proposed in the original descriptions of the Chinese material.

A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.

Yuknessia from the Cambrian of China

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Gut content fossilization and evidence for detritus feeding habits in an enrolled trilobite from the Cambrian of China

Enrolment was a major defensive strategy for trilobites that significantly contributed to their evolutionary success. The ability to enrol also helped to constrain the morphological evolution of trilobites, which in part was driven by the need to improve this capability to encapsulate the soft parts of the body within the mineralized dorsal exoskeleton. Here, we describe a unique example of gut content fossilization in an enrolled trilobite from the Cambrian of China, and we propose a taphonomic scenario that considers the possible implication of enrolment in this exceptional preservation. A micro-facies analysis indicates that the specimen was entombed during an obrution event and remained intact due to limited infaunal activity. The encapsulation of the body did not prevent the decay of soft tissues, but it permitted the delicate gut content to be protected during diagenesis. In isolating the decaying soft tissues from the external environment, enrolment might also have favoured the establishment of microenvironmental conditions conducive to the precipitation of pyrite framboids. Within the gut, the formation of such crystals may have led to the consolidation of the ingested material. These results suggest that fossilized gut contents might be quite common in enrolled trilobites. Textural and compositional analyses reveal that the gut content is similar to the sediment surrounding the fossil except for the presence of pyrite framboids that indicate higher initial organic matter content. The complete enrolment of the body argues against an accidental ingestion of this material or a diagenetic origin for it. Accordingly, detritus feeding habits are inferred for this ptychopariid trilobite.

Phosphatized eodiscoid trilobites from the Cambrian of China

Phosphatized eodiscoid trilobites from the Cambrian of China

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.

Phosphatized Bradoriids (Arthropoda) from the Cambrian of China

Phosphatized Bradoriids (Arthropoda) from the Cambrian of China

Monoplacophoran Igorella-type pore-channel structures from the Lower Cambrian in China

Monoplacophoran Igorella-type pore-channel structures from the Lower Cambrian Meishucunian Stage in China have been examined. A well-preserved shell shows that the pores are round or elliptical in transverse profile, elevated on the shell surface, and almost equally spaced and arranged along growth lines on the whole dorsal and lateral sides of the shell while the ventral side is smooth. The distribution of these Igorella-type pore-channel structures is different not only from the Maikhanella's concentric distribution but also from the Auriculaspira's spiral distribution. The pore is 10–20 μm in diameter, generally 15 μm, and the elevated shell wall is 0.1 μm thick. The pore peristome is slightly contracted and covered by a ring of granular crystals. These pores are apparently different in shape from the mastoids of Maikhanella and Auriculaspira. The pore channel arrangement is similar to that of recent molluskan bivalved shells, but the pore channels of the monoplacophoran Igorella-type shells are obviously bigger than those of the latter. It is speculated that the porosity of the shell may be useful for exchanging between the soft body and the surrounding water and relieving pressure on the thin shell from water. This study on pore-channel structures provides new evidence for understanding the skeletonization and ecological functions of early mollusks.

Fossilization modes in the Chengjiang Lagerstätte (Cambrian of China): testing the roles of organic preservation and diagenetic alteration in exceptional preservation

One important, and poorly understood, issue concerning the taphonomy of nonmineralizing organisms in Cambrian Burgess Shale-type deposits is the diagenetic pathways by which organisms have become exceptionally preserved. Scanning electron microscopy (SEM) analyses of exceptionally preserved fossils from the lower Cambrian Chengjiang deposit of China demonstrate that nonmineralized tissue is preserved in a variety of ways, and further suggest that there was some taxonomic control over the precipitation of authigenic minerals during early diagenesis. Organic preservation is limited to certain decay-resistant structures such as heavily sclerotized spines on the claws of anomalocaridids. Labile organic tissues of nearly all nonmineralizing animals, however, are preserved by thin films of diagenetic minerals. Microstructural studies, energy-dispersive X-ray (EDX) analyses, and elemental mapping of these minerals indicate that mineral films include apatite, pyrite, and Fe-rich aluminosilicates. The results support the assumption that early diagenetic mineralization such as phosphatization and pyritization played a key role in the preservation of nonmineralized organisms. Pyritization seems to be the most important process by which nonmineralizing Chengjiang organisms are preserved in exceptional condition. Precipitation of Fe-rich aluminosilicates, which occurred following pyritization, also played a role in the preservation of some Chengjiang fossils. Phosphatization in the Chengjiang Lagerstätte was evidently rare, and limited taxonomically or to animals having large masses of organic material.

Potential global stratotype sections and points in China for defining Cambrian stages and series

Three stratigraphic sections in the Cambrian of China that contain complete successions across important biohorizons having chronostratigraphic value, and that may be useful for developing Cambrian stage or series boundaries, are reviewed. The Wuliu section (Guizhou, South China), contains the FAD of Oryctocephalus indicus at 58.2 m above the base of the Kaili Formation. The Wangcun North section (Hunan, South China), contains the FADs of Ptychagnostus (or Acidusus) atavus, Ptychagnostus punctuosus, and Lejopyge laevigata at 1.2 m, 56.7 m, and 111.3 m, respectively, above the base of the Huaqiao Formation. The Xiaoyangqiao section (Jilin, Northeast China), contains the FAD of Cordylodus proavus in the Fengshan Formation at 10.89 m above the zero point of the section. A fourth potential stratotype section, the Wangcun South section (Hunan, South China), which contains the P. atavus, P. punctuosus, and L. laevigata zones, is discussed briefly.

Cambrian bivalved arthropods

This monograph is part of a series of publications by the two authors and their collaborators (Williams et al. 1994; Hou et al. 1996; Melnikova et al. 1997; Williams & Siveter, in press) aiming toward a comprehensive inventory of an important component of the Palaeozoic arthropod fauna: the bradoriids and the phosphatocopids. These two groups of small bivalved arthropods occur worldwide from the early Cambrian to the early Ordovician. From the time of their discovery in the late 19th century, these fossils were referred to the ostracod crustaceans until their soft parts were discovered in the Upper Cambrian of Sweden (phosphatocopids of the orsten faunal assemblage; Muller 1979, 1982), the Middle Cambrian of Australia (Walossek et al. 1993), the Lower Cambrian of Great Britain (a phosphatocopid baby, Hinz 1983), and the early Cambrian of China (Chengjiang fauna; Hou et al. 1996 for the braSeilacher, A. 1992: Vendobionta and Psammocorallia: lost constructions of Precambrian evolution. Journal of the Geological Society, London 149,607413. Seilacher, A. 1994: Early multicellular life: Late Proterozoic fossils and the Cambrian explosion. In Bengtson, S. (ed.): Early Life On Earth Nobel Symposium No. 84, 389400. Columbia University Press, New York, N.Y. Valentine, J.W. 1992: Dickinsonia as a polypoid organism. Paleobiology

Giant Predators from the Cambrian of China

Giant Predators from the Cambrian of China

Gold and platinum in shales with evidence against extraterrestrial sources of metals

Few black shales contain concentrations of precious metals higher than average continental crust (i.e. ∼5 ppb Au). Yet Au and Pt alloys have been reported from the Kupferschiefer in Poland. Moreover, thin sulfide beds in certain Chinese and Canadian shales contain several hundred ppb Au, Pd and Pt and average ∼4% Mo and ∼2.5% Ni in an association that is difficult to explain. Volcanic and non-volcanic exhalations, hydrothermal epigenesis involving either igneous or sedex fluids, biogenic processes and low-temperature secondary enrichment are among the possible factors involved in deriving Ni, PGE and Au for black shales and sulfide beds in black shales. Extraterrestrial sources have been invoked in some cases (e.g., the Cambrian of China). However, available data on abundances of PGE indicate relatively low values for Ir (<0.02–2 ppb) in comparison with amounts for other PGE (up to 700 ppb Pt and 1255 ppb Pd). These data and high contents for Mo are not consistent with extraterrestrial sources of metals for Chinese shales and Ni–Mo-sulfide beds. Data are less complete for the U.S. shales, but nevertheless are suggestive of earthly origins for PGE.

Early and Middle Cambrian Hyolitha (Mollusca) from northeastern China

The hyolithid species Hyolithes crebescens Resser and Endo, Hyolithes cybele Walcott, and Hyolithes delphus Resser and Endo from the Middle Cambrian of China are assigned respectively to the genera Nevadotheca Malinky, Novakotheca n. gen., family Hyolithidae, and Crestjahitus Syssoiev, family uncertain, all in the order Hyolithida. Recognition of Nevadotheca extends its geographic range from North America to China, and the occurrence of Crestjahitus in the Middle Cambrian of China increases its geographic and stratigraphic distribution from the Early Cambrian of the Soviet Union.Poor preservation of the type specimens of Hyolithes? aliger Resser and Endo, H.? aplatus Resser and Endo, H.? cariniferus Resser and Endo, H.? daphnis Walcott, H.? delia Walcott, H.? endoi Howell (as H. ornatus Resser and Endo), H.? mantouensis Resser and Endo, and H.? tenuis Resser and Endo renders their generic identification uncertain. Hyolithes (Orthotheca) glabrus Resser and Endo is here transferred to the hyolith order Orthothecida Marek and referred with question to Decoritheca Syssoiev, family Novitatidae.Morphology of the types of “Hyolithes” fuchouensis Resser and Endo, “H.” kuantungensis Resser and Endo, “H.” sondai Resser and Endo, “Orthotheca” daulis Walcott, and “O.” doris Walcott does not support assignment to the Hyolitha for these species; their phylogenetic affinity is uncertain.

Mellopegma (Mollusca) from the Middle Cambrian of North Greenland

During the last decade, the resurgence of interest in the non-trilobite faunas of the Cambrian has resulted in the description of many new taxa of problematic molluscs. One such form is the laterally compressed helcionellacean Mellopegma, originally described from the Middle Cambrian of Australia by Runnegar &amp; Jell (1976) but subsequently reported from the Lower Cambrian of China (Zhou &amp; Xiao, 1984). Mellopegma has now been identified from the Middle Cambrian of central North Greenland where it occurs as phosphatised internal mouids preserved in a manner similar to that of the original Australian specimens from the Currant Bush Limestone of Queensland.

Disparity, decimation and the Cambrian "explosion": comparison of eady Cambrian and Present faunal communities with emphasis on velvet worms (Onychophora)

The controversy about a Cambrian "explosion" of morphological disparity (followed by decimation), cladogenesis and fossilization is of central importance for the history of life. This paper revisits the controversy (with emphasis in onychophorans, which include emblematic organisms such as Hallucigenia), presents new data about the Chengjiang (Cambrian of China) faunal community and compares it and the Burgess Shale (Cambrian of Canada) with an ecologically similar but modern tropical marine site where onychophorans are absent, and with a modern neotropical terrestrial onychophoran community. Biovolume was estimated from material collected in Costa Rica and morphometric measurements were made on enlarged images of fossils. Cambrian tropical mudflats were characterized by the adaptive radiation of two contrasting groups: the vagile arthropods and the sessile poriferans. Arthropods were later replaced as the dominant benthic taxon by polychaetes. Vagility and the exoskeleton may explain the success of arthropods from the Cambrian to the modern marine and terrestrial communities, both in population and biovolume. Food ecological displacement was apparent in the B. Shale, but not in Chengjiang or the terrestrial community. When only hard parts were preserved, marine and terrestrial fossil deposits of tropical origin are even less representative than deposits produced by temperate taxa, Chengjiang being an exception. Nutrient limitations might explain why deposit feeding is less important in terrestrial onychophoran communities, where carnivory, scavenging and omnivory (associated with high motility and life over the substrate) became more important. Fossil morphometry supports the interpretation of "lobopod animals" as onychophorans, whose abundance in Chengjiang was equal to their abundance in modern communities. The extinction of marine onychophorans may reflect domination of the infaunal habitat by polychaetes. We conclude that (1) a mature ecological community structure was generalized during the Cambrian, and even biodiversity and equitability indices were surprisingly close to modern values; (2) the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does not support the "explosion" hypothesis; (3) disparity among phyla was not as important as the explosion-decimation model predicts, but in the case of onychophorans, disparity within the phylum was greater than it is today and its reduction may have been associated with migration into the sediment when large predators evolved.