A new small soft-bodied non-trilobite artiopod from the Cambrian Stage 4 Guanshan Biota

We describe an extraordinarily preserved non-trilobite artiopod Bailongia longicaudata gen. et sp. nov. from the Cambrian Stage 4 Guanshan Biota in Yiliang, Kunming of the Yunnan Province in China. Its exoskeleton consists of a large semi-elliptical cephalon with paired lateral posterior eyes, nine tapering homonomous tergites and a long slender tailspine. Appendages include paired small antennae, at least three pairs of post-antennal cephalic limbs, and trunk biramous limbs consisting of an endopod and an exopod with lamellae. B. longicaudata does not conform to any taxon within Artiopoda, although the eyes invite comparisons with Xandarella spectaculum, Sinoburius lunaris and Phytophilaspis. Parsimony analyses indicate Bailongia is a member of Artiopoda and cannot be readily accommodated within any of the major artiopod clades.

New multipodomerous appendages of stem-group euarthropods from the Cambrian (Stage 4) Guanshan Konservat-Lagerstätte

Stem-group euarthropods are important for understanding the early evolutionary and ecological history of the most species-rich animal phylum on Earth. Of particular interest are fossil taxa that occupy a phylogenetic position immediately crownwards of radiodonts, for this part of the euarthropod tree is associated with the appearance of several morphological features that characterize extant members of the group. Here, we report two new euarthropods from the Cambrian Stage 4 Guanshan Biota of South China. The fuxianhuiid Alacaris ? sp. is represented by isolated appendages composed of a gnathobasic protopodite and an endite-bearing endopod of at least 20 podomeres. This material represents the youngest occurrence of the family Chengjiangocarididae, and its first record outside the Chengjiang and Xiaoshiba biotas. We also describe Lihuacaris ferox gen. et sp. nov. based on well-preserved and robust isolated appendages. Lihuacaris ferox exhibits an atypical combination of characters including an enlarged rectangular base, 11 endite-bearing podomeres and a hypertrophied distal element bearing 8–10 curved spines. Alacaris ? sp. appendages display adaptations for macrophagy. Lihuacaris ferox appendages resemble the frontal appendages of radiodonts, as well as the post-oral endopods of chengjiangocaridid fuxianhuids and other deuteropods with well-documented raptorial/predatory habits. Lihuacaris ferox contributes towards the record of endemic biodiversity in the Guanshan Biota.

First report of acrotretoid brachiopod shell beds in the lower Cambrian (Stage 4) Guanshan Biota of eastern Yunnan, South China

Brachiopod shell accumulations are abundant and diverse in the lower Cambrian strata of Yunnan Province, South China, but most commonly they are composed of linguloid and acrotheloid brachiopods. Here, we describe the first record of shell beds with high-density accumulations of microscopic acrotretoid brachiopods (usually <2 mm in width) in the muddy deposits of the Wulongqing Formation (Guanshan Biota, Cambrian Stage 4) in the Wuding area of Yunnan Province. The acrotretoid shell beds from the Wulongqing Formation vary from thin mm-thick pavements to more well-developed beds, several centimeters thick. The occurrence of remarkably rich acrotretoid shell beds indicates that microscopic lingulates began to exert an important role in hardening and paving the soft-substrate seafloor during the early Cambrian evolution of Phanerozoic “mixgrounds.” The new Guanshan material is referred to a new species, Linnarssonia sapushanensis n. sp., which differs from other species of Linnarssonia mainly in having a well-developed internal pedicle tube, as well as a relatively longer dorsal median septum. The occurrence of Linnarssonia sapushanensis n. sp. in the Wulongqing Formation in eastern Yunnan extend the oldest record of the genus on the Yangtze Platform of South China back to at least Cambrian Stage 4.UUID: http://zoobank.org/3e0c3878-6ce2-4eed-87bf-e39647c310c4

Brachiopod-dominated communities and depositional environment of the Guanshan Konservat-Lagerstätte, eastern Yunnan, China

The Guanshan Biota is an unusual early Cambrian Konservat-Lagerstätte from China and is distinguished from all other exceptionally preserved Cambrian biotas by the dominance of brachiopods and a relatively shallow depositional environment. However, the faunal composition, overturn and sedimentology associated with the Guanshan Biota are poorly understood. This study, based on collections through the best-exposed succession of the basal Wulongqing Formation at the Shijiangjun section, Wuding County, eastern Yunnan, China recovered six major animal groups with soft tissue preservation; brachiopods vastly outnumbered all other groups. Brachiopods quickly replace arthropods as the dominant fauna following a transgression at the base of the Wulongqing Formation. A transition from a botsfordiid-, eoobolid- and acrotretid- to an acrotheloid-dominated brachiopod assemblage occurs up-section. Four episodically repeated lithofacies reveal a relatively low-energy, offshore to lower shoreface sedimentary environment at the Shijiangjun section, which is very different from the Wulongqing Formation in the Malong and Kunming areas. Multiple event flows and rapid obrution are responsible for faunal overturn and fluctuation through the section. A detailed lithofacies and palaeontological investigation of this section provides a better understanding of the processes and drivers of faunal overturn during the later phase of the Cambrian Explosion.Supplementary material: Composition and comparison of the Malong Fauna and the Guanshan Biota is are available at: https://doi.org/10.6084/m9.figshare.c.5080799

Waptia-like Euarthropods from Burgess - Shale - type Biotas in the Early Cambrian of Eastern Yunnan, China

Waptia-like euarthropods existed for rather a long time in the Early Cambrian of eastern Yunnan; well preserved representatives come mainly from three Burgess Shale-type biotas: Chengjiang, Xiaoshiba and Guanshan. Here, we introduce a newly-discovered bivalved euarthropod from the Guanshan biota, the specific identity of which cannot be confirmed due to the absence of soft parts and poor preservation of the specimen, but its general morphology allows it be attributed to Waptia. Two representatives from the Chengjiang and Xiaoshiba biotas are also reconsidered: the preservation mode and length of specimens of Clypecaris pteroidea are variable; Clypecaris serrate has limbs beneath the carapace, which can number up to at least 4 pairs. The fossil sections bearing Waptia-like euarthropods occur over a wide area around Dianchi Lake.