scholarly journals Development of the early Cambrian oryctocephalid trilobite Oryctocarella duyunensis from western Hunan, China

2021 ◽  
pp. 1-16
Author(s):  
Tao Dai ◽  
Nigel C. Hughes ◽  
Xingliang Zhang ◽  
Shanchi Peng
Keyword(s):  
South China ◽  
Growth Pattern ◽  
Lower Cambrian ◽  
Hunan Province ◽  
Early Cambrian ◽  
Gradual Change ◽  
Stage 4 ◽  
Western Hunan ◽  
Trunk Segments

Abstract Abundant articulated specimens of the oryctocarine trilobite Oryctocarella duyunensis from the lower Cambrian (Stage 4, Series 2) Balang Formation at the Bulin section in western Hunan Province, South China, permit the description of all meraspid degrees. The maximum number of thoracic segments observed in this collection is 11. Meraspid growth was accompanied by progressive and gradual change in overall form, and this animal showed an homonymously segmented trunk with variation in the number of pygidial segments during ontogeny. Such variation permits a variety of plausible explanations, but a model of successive instars defined by the number of thoracic segments, and in suborder by the number of pygidial segments, is highly unlikely to explain the growth pattern because it would result in the loss of trunk segments between some instars. Degree-based ontogenetic staging is compatible with the variation observed.

Olivooides-like tube aperture in early Cambrian carinachitids (Medusozoa, Cnidaria)

2017 ◽  
Vol 92 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Jian Han ◽  
Guoxiang Li ◽  
Xing Wang ◽  
Xiaoguang Yang ◽  
Junfeng Guo ◽  
...  
Keyword(s):  
Soft Tissue ◽  
South China ◽  
Growth Pattern ◽  
Lower Cambrian ◽  
Small Mass ◽  
Early Cambrian ◽  
Spatial Relationships ◽  
Small Shelly Fossils ◽  
Secondary Thickening

AbstractThe early Cambrian Carinachitidae, a family in the subclass Conulata, are intriguing and important small shelly fossils. Their gently tapering, tube-shaped skeletons consist of convex faces separated from each other by broad, deep corner sulci, and they exhibit triradial, pentaradial, or predominantly tetraradial symmetry. However, the morphology of the aperture and the modes of growth of carinachitid skeletons as well as the anatomy of their soft parts are unknown. Examination of a single new, exceptionally well-preserved specimen of tetramerousCarinachites spinatusQian, 1977, collected from the lower Cambrian Kuanchuanpu Formation in South China, reveals: (1) that its aperture is connected to a small mass of relic soft tissue and (2) that the apertural end of each of the four faces is developed into a subtriangular lappet or oral lobe that is smoothly folded toward the long axis of the tube, partially closing the tube aperture. Similarities between thorn-like spines on the faces and the oral lobes indicate that the transverse ribs were periodically displaced from the perradial portion of the aperture during formation of new ribs. In addition, the tube walls may have undergone secondary thickening during growth. The growth pattern of the tube and the spatial relationships between the tube aperture and soft parts are analogous to those of co-occurring olivooids. These findings further strengthen the previously proposed hypothesis that coeval carinachitids, olivooids, hexangulaconulariids, and Paleozoic conulariids are closely related taxa within the subphylum Medusozoa. Finally, carinachitids most likely represent an evolutionary intermediate between olivooids and hexangulaconulariids.

scholarly journals Geologic characterization of a lower Cambrian marine shale: Implications for shale gas potential in northwestern Hunan, South China

2018 ◽  
Vol 6 (3) ◽  
pp. T635-T647 ◽  
Author(s):  
Zhenghui Xiao ◽  
Jisong Liu ◽  
Jingqiang Tan ◽  
Rongfeng Yang ◽  
Jason Hilton ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
South China ◽  
Lower Cambrian ◽  
Gas Adsorption ◽  
Vitrinite Reflectance ◽  
Mean Value ◽  
Hunan Province ◽  
Quartz Content ◽  
Gas Potential

We have investigated the geologic features of the lower Cambrian-aged Niutitang Shale in the northwestern Hunan province of South China. Our results indicate that the Niutitang Shale has abundant and highly mature algal kerogen with total organic carbon (TOC) content ranging from 0.6% to 18.2%. The equivalent vitrinite reflectance (equal-Ro) value is between 2.5% and 4.3%. Mineral constituents are dominated by quartz and clay. The average quartz content (62.8%) is much higher than that of clay minerals (26.1%), and this suggests a high brittleness index. Organic-matter pores, interparticle pores, intraparticle pores, interlaminated fractures, and structural fractures are all well developed. The porosity ranges from 0.6% to 8.8%, with an average of 4.8%, whereas the permeability varies from 0.0018 to [Formula: see text] (microdarcy) (averaging [Formula: see text]). The porosity of TOC- and clay-rich shale samples is generally higher than that of quartz-rich shale samples. The gas adsorption capacity of the Niutitang Shale varies from 2.26 to [Formula: see text], with a mean value of [Formula: see text]. The TOC content appears to significantly influence gas adsorption capacity. In general, TOC-rich samples exhibit a much higher adsorption capacity than TOC-poor samples.

scholarly journals Caught in the act: priapulid burrowers in early Cambrian substrates

2019 ◽  
Vol 286 (1894) ◽  
pp. 20182505 ◽  
Author(s):  
Giannis Kesidis ◽  
Ben J. Slater ◽  
Sören Jensen ◽  
Graham E. Budd
Keyword(s):  
Comparative Analysis ◽  
Lower Cambrian ◽  
Trace Fossil ◽  
Considerable Importance ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Southern Sweden ◽  
Stage 4 ◽  
Organic Remains

The fossilized traces of burrowing worms have taken on a considerable importance in studies of the Cambrian explosion, partly because of their use in defining the base of the Cambrian. Foremost among these are the treptichnids, a group of relatively large open probing burrows that have sometimes been assigned to the activities of priapulid scalidophoran worms. Nevertheless, most Cambrian burrows have an uncertain progenitor. Here we report a suite of exceptionally preserved trace and body fossils from sandstones of the lower Cambrian (Stage 4) File Haidar Formation of southern Sweden that can unequivocally be assigned to a scalidophoran producer. We further present the first burrow casts produced via actualistic experiments on living priapulids, and demonstrate the remarkable morphological parallels between these modern and Cambrian fossil equivalents. In addition, co-occurrence of scalidophoran-derived cuticular remains permits a unique synthesis of evidence from trace fossil, body and organic remains. Comparative analysis of these exceptionally preserved fossils supports a scalidophoran producer for treptichnids and by extension suggests a latest Ediacaran origin of the ecdysozoan clade.

scholarly journals Ontogeny of the articulated yiliangellinine trilobite Zhangshania typica from the lower Cambrian (Series 2, Stage 3) of southern China

2016 ◽  
Vol 91 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Jin-bo Hou ◽  
Nigel C. Hughes ◽  
Jie Yang ◽  
Tian Lan ◽  
Xi-guang Zhang ◽  
...  
Keyword(s):  
South China ◽  
Lower Cambrian ◽  
Southern China ◽  
Junior Synonym ◽  
Early Cambrian ◽  
South China Block ◽  
The South ◽  
Positive Allometry ◽  
Regional Correlation ◽  
Almost All

AbstractNew discoveries of the early Cambrian yiliangellinine trilobite Zhangshania typica Li and Zhang in Kunming preserve almost all instars from early postembryonic (protaspid) to mature (holaspid) phases in articulated state, in addition to mature specimens with antennae bearing paired spines on the basal articles. The ontogenetic series shows protarthrous development with some, but likely not all, early holaspid instars expressing additional pygidial segments, gradual rearward migration of the location of the longest pleural spines on the trunk segments, and striking positive allometry of the genal spines. It also reveals Parazhangshania sichuanensis Li and Zhang, 1990 to be the holaspid stage 3 of Z. typica, and therefore its junior synonym. This new find in the Hongjingshao Formation provides species-based regional correlation across the South China block and Z. typica may provide an important biostratigraphic marker for the base of the traditional Tsanglangpuan Stage.

New material of three-dimensionally phosphatized and microscopic cycloneuralians from the Cambrian Paibian Stage of South China

2017 ◽  
Vol 92 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Yunhuan Liu ◽  
Qi Wang ◽  
Tiequan Shao ◽  
Huaqiao Zhang ◽  
Jiachen Qin ◽  
...  
Keyword(s):  
New Species ◽  
South China ◽  
Early Cambrian ◽  
Late Cambrian ◽  
New Material ◽  
Western Hunan ◽  
Fossil Embryos

AbstractSome rare microscopic cycloneuralians are present in the Cambrian of South China, represented by Eopriapulites and Eokinorhynchus (both early Cambrian), fossil embryos of Markuelia (middle to late Cambrian), and palaeoscolecids (early to late Cambrian). Among them, palaeoscolecids are relatively diverse and abundant. Here, we describe new material of three-dimensionally phosphatized and microscopic cycloneuralians from the Paibian Stage of Wangcun Lagerstätte, western Hunan, South China. New material includes fossil embryos assignable to Markuelia sp., two other types of fossil embryos, and three species of palaeoscolecids, including Dispinoscolex decorus Duan, Dong, and Donoghue, 2012, Schistoscolex hunanensis Duan, Dong, and Donoghue, 2012, and Austroscolex sinensis new species. The palaeoscolecid fragments differ mainly in size and armor of the trunk annuli. Since Eokinorhynchus and Eopriapulites occurred the earliest among the Cambrian cycloneuralians, it is proposed here that: (1) cycloneuralians originated in the Cambrian Fortunian small shelly faunas rather than in the early Cambrian macrobenthos, (2) ancestral cycloneuralians may have simple trunk armor, and (3) Eopriapulites represents an ancestral cycloneuralian.

scholarly journals Occurrence ofMicrodictyonfrom the lower Cambrian Xinji Formation along the southern margin of the North China Platform

2017 ◽  
Vol 92 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Bing Pan ◽  
Timothy P. Topper ◽  
Christian B. Skovsted ◽  
Lanyun Miao ◽  
Guoxiang Li
Keyword(s):  
Lower Cambrian ◽  
North China ◽  
Ontogenetic Variation ◽  
Early Cambrian ◽  
North China Platform ◽  
Middle Cambrian ◽  
The North ◽  
Formation Stage ◽  
Inadequate Knowledge ◽  
Stage 4

AbstractDisarticulated net-like plates of the lobopodMicrodictyonhad a near cosmopolitan distribution from the early to middle Cambrian but are yet to be documented from the North China Platform. Here we report isolated plates ofMicrodictyonfrom the lower Cambrian Xinji Formation (Stage 4, Series 2) of the North China Platform, extending the paleogeographic distribution ofMicrodictyonin the early Cambrian. The plates ofMicrodictyonfrom the Xinji Formation are similar to those of other species established on the basis of isolated plates but do bear some new characters, such as mushroom-shaped nodes with a single inclined platform-like apex and an upper surface that displays radial lines. However, the plates documented here are left under open nomenclature due to inadequate knowledge of intraspecific and ontogenetic variation and low specimen numbers. Through comparison of the node shapes of the isolated plates of differentMicrodictyonspecies, we consider that low mushroom-shaped nodes could be a primitive and conservative character ofMicrodictyonwhile tall mushroom-shaped nodes may be a derived character. Subtle differences in shape and number of node apices may also represent intraspecific or ontogenetic variation.

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