Jih-Pai Lin

Burgess Shale-type microfossils from the middle Cambrian Kaili Formation, Guizhou Province, China

Diverse carbonaceous microfossils, including exceptionally preserved remains of non-biomineralizing metazoans, are reported from a basal middle Cambrian interval of the Kaili Formation (Guizhou Province, China). The application of a gentle acid maceration technique complements previous palynological studies by revealing a larger size-class of acritarchs, a richer assemblage of filamentous microfossils, and a variety of previously unrecovered forms. Metazoan fossils include Wiwaxia sclerites and elements derived from biomineralizing taxa, including chancelloriids, brachiopods and hyolithids, in common with previously studied assemblages from the early and middle Cambrian of Canada. In addition, the Kaili Formation has yielded pterobranch remains and an assemblage of cuticle fragments representing “soft-bodied” worms, including a priapulid-like scalidophoran. Our results demonstrate the wide distribution and palaeobiological importance of microscopic “Burgess Shale-type” fossils, and provide insights into the limitations and potential of this largely untapped preservational mode.

BURGESS SHALE-TYPE PRESERVATION: A COMPARISON OF NARAOIIDS (ARTHROPODA) FROM THREE CAMBRIAN LOCALITIES

Abstract The chemical composition of well-preserved naraoiids from the Chengjiang, Kaili, and Burgess Shale biotas is compared. Gut diverticulae in samples from all three biotas contain C, P, and Fe, indicating a primary composition of organic carbonaceous material, and the presence of apatite and pyrite as the result of authigenic mineralization in association with decay and early diagenetic processes. Gut traces from Burgess Shale specimens retain apatite and pyrite, as well as clay minerals, reflecting a history involving greenschist-grade metamorphism. Kaili specimens have been subjected to lower-grade metamorphism and, or thermal alteration, but alteration of pyrite pseudomorphs in the gut traces to limonite indicates the effect of weathering. Loss of sulfur and calcium, oxidation of pyrite, and the light color of the Chengjiang samples are the result of a greater degree of weathering than in specimens from the other two localities. As demonstrated here, Kaili samples serve as an important baseline for interpreting specimens from the Burgess Shale (high-grade metamorphism) and the Chengjiang (intense chemical weathering) deposits. Our study shows for the first time that the conservation of organic carbon is the common primary mode of soft-part preservation in naraoiid arthropods from these three signature Burgess Shale-type localities. Differences among these major deposits are a product of later diagenesis and weathering of the authigenic mineralization associated with the preservation of labile structures. Among the major constituents formed during diagenesis—carbonaceous material, calcium phosphate (e.g., apatite), and iron sulfide (e.g., pyrite)—the minerals are more susceptible to chemical weathering via hydrolysis.

Relationships of the Cambrian Protomonaxonida (Porifera)

The Protomonaxonida consist of a heterogeneous group of early fossil sponges traditionally assigned to the demosponges. However, an affinity to the hexactinellid-like Reticulosa has also been suggested, and their relationships are potentially critical to understanding the origins of the extant sponge classes. In this paper, the relationships of the protomonaxonid sponges to each other and to other sponge groups have been reassessed, using previously described specimens as well as new material from the Burgess Shale of Canada and the Hetang Biota of South China. The sponges fall into two coherent groups, one consisting of taxa with long, mostly sub-longitudinal spicules, and the other with complex arrays composed of tracts of minute (millimetre-scale) monaxons, which grade into aspiculate taxa such as the Vauxiidae. Previous ideas relating the Protomonaxonida to extant demosponge lineages are supported in the case of the second group, whereas the first group confirms the view of derivation from a hexactinellid-like ancestor. Whether the two groups were directly related or evolved monaxonid spiculation in parallel is currently uncertain. Joseph P. Botting. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China acutipuerilis@yahoo.co.uk Lucy A. Muir. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China lucy@asoldasthehills.org Jih-Pai Lin (corresponding author). State Key Laboratory of Palaeobiology and Stratigraphy, and Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, CAS, 39 East Beijing Road, Nanjing 210008, China jplin@nigpas.ac.cn

New material from the Ordovician of China indicates that Inocaulis is a graptolite

Muir, L.A., Zhang, Y.-D. & Lin, J.-P. 2012. New material from the Ordovician of China indicates that Inocaulis is a graptolite. Alcheringa 37, 558–559. ISSN 0311-5518. The problematic Early Palaeozoic fossil Inocaulis has been regarded as an alga, a graptolite and a hydroid by different authors. A new specimen from the Ordovician (late Darriwilian) of Guizhou Province (China) shows fusellar banding, confirming that it is a benthic graptolite. Lucy A Muir [lucy@asoldasthehills.org], Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Jih-Pai Lin [jplin@nigpas.ac.cn] (corresponding author), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, No. 39 East Beijing Road, Nanjing 210008, PR China. Received 13.12.2012; revised 10.5.2013; accepted 13.5.2013.

Function and hydrostatics in the telson of the Burgess Shale arthropod Burgessia

Burgessia bella is a characteristic Burgess Shale arthropod (508 Ma), but the unusual preservation of its telson in both straight and bent modes leads to contradictory interpretations of its function. A reinvestigation of the fossil material, including burial attitudes, combined with a comparison with the decay sequence and mechanics of the telson in living Limulus, demonstrates that the telson of Burgessia was flexible in its relaxed state but could be stiffened in life. Evidence of fluid within the telson indicates that this manoeuvrability was achieved by changes in hydrostatic pressure and muscular control. The dual mode in the Burgessia telson is, to my knowledge, the first documented among fossil arthropods. It indicates that the requirement for a rigid telson, which is resolved by a thick sclerotized cuticle in most arthropods, may first have been achieved by hydrostatic means.