Comment on "Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans".

Tian . (Reports, 8 July 2022, p. 218) claim that Cambrian yunnanozoan animals are stem vertebrates, based partly on their observation at the nanometer scale of microfibrillar tissue located in the branchial arches.

Protomelission is an early dasyclad alga and not a Cambrian bryozoan.

The animal phyla and their associated body plans originate from a singular burst of evolution occurring during the Cambrian period, over 500 million years ago. The phylum Bryozoa, the colonial 'moss animals', have been the exception: convincing skeletons of this biomineralizing clade have been absent from Cambrian strata, in part because potential bryozoan fossils are difficult to distinguish from the modular skeletons of other animal and algal groups. At present, the strongest candidate is the phosphatic microfossil Protomelission.

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.

A 'hermit' shell-dwelling lifestyle in a Cambrian priapulan worm.

The Cambrian 'explosion', about 530 million years ago, marks a rapid diversification of the major animal lineages. A concomitant increase in the complexity of ecosystems is believed to have accelerated this evolutionary radiation, but direct evidence of the ecological modes of Cambrian taxa is nevertheless scarce - even in exceptional Burgess Shale-type deposits. Here, we present new fossil material from the Cambrian (Stage 4) Guanshan biota in southern China that reveals the consistent occurrence of the priapulan worm ?Eximipriapulus within the conical shells of hyoliths.

A soft-bodied euarthropod from the early Cambrian Xiaoshiba Lagerstätte of China supports a new clade of basal artiopodans with dorsal ecdysial sutures.

We describe the exceptionally well-preserved non-trilobite artiopodan Zhiwenia coronata gen. et sp. nov.

Ecdysis in a stem-group euarthropod from the early Cambrian of China.

Moulting is a fundamental component of the ecdysozoan life cycle, but the fossil record of this strategy is susceptible to preservation biases, making evidence of ecdysis in soft-bodied organisms extremely rare. Here, we report an exceptional specimen of the fuxianhuiid Alacaris mirabilis preserved in the act of moulting from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China. The specimen displays a flattened and wrinkled head shield, inverted overlap of the trunk tergites over the head shield, and duplication of exoskeletal elements including the posterior body margins and telson.

Fuxianhuiids.

Ortega-Hernández et al. introduce fuxianhuiids, Cambrian arthropods that are important for our understaindg how the largest animal phylum evolved.

Early Cambrian fuxianhuiids from China reveal origin of the gnathobasic protopodite in euarthropods.

Euarthropods owe their evolutionary and ecological success to the morphological plasticity of their appendages. Although this variability is partly expressed in the specialization of the protopodite for a feeding function in the post-deutocerebral limbs, the origin of the former structure among Cambrian representatives remains uncertain. Here, we describe Alacaris mirabilis gen.

Onychophoran-like musculature in a phosphatized Cambrian lobopodian.

The restricted, exclusively terrestrial distribution of modern Onychophora contrasts strikingly with the rich diversity of onychophoran-like fossils preserved in marine Cambrian Lagerstätten The transition from these early forebears to the modern onychophoran body plan is poorly constrained, in part owing to the absence of fossils preserving details of the soft anatomy. Here, we report muscle tissue in a new early Cambrian (Stage 3) lobopodian, Tritonychus phanerosarkus gen. et sp.

A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China.

Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp.

Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda.

Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstätte (South China).

[Case-control study on three antithrombotic agents for the prevention of venous thromboembolism after unilateral total knee arthroplasty].

Objective: To evaluate the efficacy and safety of three antithrombotic agents on venous thromboembolism (VTE) after unilateral total knee arthroplasty.

Methods: From November 2011 to March 2014, 149 patients undergoing unilateral total knee arthroplasty for knee osteoarthritis were reviewed. Among them, there were 66 males and 83 females, ranging in age from 48 to 76 years old.

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.

Development and trunk segmentation of early instars of a ptychopariid trilobite from Cambrian Stage 5 of China.

Many three-dimensionally preserved exoskeletons found from the middle Cambrian (Stage 5) Gaotai Formation in Guizhou, southern China, have been assigned to the ptychopariid trilobite Gunnia sp. They represent mainly a series of early instars, exhibiting some delicate structures and morphological variation associated with their trunk segmentation and early development. Morphometric and statistical analyses indicate that the transverse joint appears to occur with the full growth of the third axial ring of the protopygidium, which increases in size much more rapidly than its corresponding protocephalon with growth.

Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba lagerstätte.

Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp.

Specialized appendages in fuxianhuiids and the head organization of early euarthropods.

The organization of the head provides critical data for resolving the phylogenetic relationships and evolutionary history of extinct and extant euarthropods. The early Cambrian-period fuxianhuiids are regarded as basal representatives of stem-group Euarthropoda, and their anterior morphology therefore offers key insights for reconstructing the ancestral condition of the euarthropod head. However, the paired post-antennal structures in Fuxianhuia protensa remain controversial; they have been interpreted as both 'great appendages' and as gut diverticulae.

The first stalk-eyed phosphatocopine crustacean from the Lower Cambrian of China.

Exhibiting Orsten-type preservation, specimens of the phosphatocopine Dabashanella sp. from the Lower Cambrian Stage 3 (about 520 million years ago) of southern China possess a single-fold shield and a set of appendages of crustacean design. More significantly, a pair of stalked eyes-the earliest known visual structure in this group-is attached to an ocular segment analogous to the anterior sclerite of various stem-group arthropods.

A eucrustacean metanauplius from the Lower Cambrian.

A new eucrustacean arthropod, Wujicaris muelleri gen. et sp. nov, is represented by a Lower Cambrian early metanauplius of strikingly modern morphology despite being the oldest known fossil of such an early immature crustacean larva.

Trunk segmentation of Cambrian eodiscoid trilobites.

Here we report, from Cambrian Series 2 of Chongqing, southern China, on some three-dimensionally phosphatized exoskeletons representing a series of instars of a specialized eodiscoid trilobite Badiscus spinosus gen. et sp. nov.

An epipodite-bearing crown-group crustacean from the Lower Cambrian.

Crown-group crustaceans (Eucrustacea) are common in the fossil record of the past 500 million years back to the early Ordovician period, and very rare representatives are also known from the late Middle and Late Cambrian periods. Finds in Lower Cambrian rocks of the Phosphatocopina, the fossil sister group to eucrustaceans, imply that members of the eucrustacean stem lineage co-occurred, but it remained unclear whether crown-group members were also present at that time. 'Orsten'-type fossils are typically tiny embryos and cuticle-bearing animals, of which the cuticle is phosphatized and the material is three-dimensional and complete with soft parts.

Evidence of lophophore diversity in early Cambrian brachiopoda.

The lophophore, an essential organ of the Brachiopoda, has been used widely in evolutionary and advanced phylogenetic studies, but is hitherto unknown in the fossil record. Here, the extraordinarily well-preserved lophophores of two inarticulated brachiopods Lingulella chengjiangensis and Heliomedusa orienta, from the Lower Cambrian Chengjiang fauna (Yunnan, China) are described. These primitive lophophores, respectively, trocholophous and schizolophous, have some key characters that may be plesiomorphies inherited by their recent descendants.