1
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Zhang H, Xiao S, Eriksson ME, Duan B, Maas A. Musculature of an Early Cambrian cycloneuralian animal. Proc Biol Sci 2023; 290:20231803. [PMID: 37817588 PMCID: PMC10565385 DOI: 10.1098/rspb.2023.1803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 09/18/2023] [Indexed: 10/12/2023] Open
Abstract
Cycloneuralians are ecdysozoans with a fossil record extending to the Early Cambrian Fortunian Age and represented mostly by cuticular integuments. However, internal anatomies of Fortunian cycloneuralians are virtually unknown, hampering our understanding of their functional morphology and phylogenetic relationships. Here we report the exceptional preservation of cycloneuralian introvert musculature in Fortunian rocks of South China. The musculature consists of an introvert body-wall muscular grid of four circular and 36 radially arranged longitudinal muscle bundles, as well as an introvert circular muscle associated with 19 roughly radially arranged, short retractors. Collectively, these features support at least a scalidophoran affinity, and the absence of muscles associated with a mouth cone and scalids further indicates a priapulan affinity. As in modern scalidophorans, the fossil musculature, and particularly the introvert circular muscle retractors, may have controlled introvert inversion and facilitated locomotion and feeding. This work supports the evolution of scalidophoran-like or priapulan-like introvert musculature in cycloneuralians at the beginning of the Cambrian Period.
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Affiliation(s)
- Huaqiao Zhang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | | | - Baichuan Duan
- Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resource, Qingdao 266061, People's Republic of China
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2
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Wang D, Vannier J, Sun J, Yu C, Han J. A New Chengjiang Worm Sheds Light on the Radiation and Disparity in Early Priapulida. BIOLOGY 2023; 12:1242. [PMID: 37759641 PMCID: PMC10525141 DOI: 10.3390/biology12091242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 09/08/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023]
Abstract
The vast majority of early Paleozoic ecdysozoan worms are often resolved as stem-group Priapulida based on resemblances with the rare modern representatives of the group, such as the structure of the introvert and the number and distribution of scalids (a spiny cuticular outgrowth) and pharyngeal teeth. In Priapulida, both scalids and teeth create symmetry patterns, and three major diagnostic features are generally used to define the group: 25 longitudinal rows of scalids (five-fold symmetry), 8 scalids around the first introvert circle and the pentagonal arrangement of pharyngeal teeth. Here we describe Ercaivermis sparios gen. et sp. nov., a new priapulid from the early Cambrian Chengjiang Lagerstätte, characterized by an annulated trunk lacking a sclerotized ornament, four pairs of anal hooks and 16 longitudinal rows of scalids along its introvert and eight scalids around each introvert circle, giving the animal an unusual octoradial symmetry. Cladistic analyses resolve Ercaivermis as a stem-group priapulid. Ercaivermis also suggests that several biradial symmetry patterns (e.g., pentagonal, octagonal) expressed in the cuticular ornament, may have co-existed among early Cambrian priapulids and that the pentaradial mode may have become rapidly dominant during the course of evolution, possibly via the standardization of patterning, i.e., the natural selection of one symmetry type over others.
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Affiliation(s)
- Deng Wang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi’an 710069, China; (D.W.); (J.S.); (C.Y.)
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
| | - Jean Vannier
- Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), CNRS, ENS de Lyon, Université Claude Bernard Lyon 1, Université de Lyon, Villeurbanne 69622, France;
| | - Jie Sun
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi’an 710069, China; (D.W.); (J.S.); (C.Y.)
- School of Earth Science and Resources, Key Laboratory of Western China’s Mineral Resources and Geological Engineering, Ministry of Education, Chang’an University, Xi’an 710054, China
| | - Chiyang Yu
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi’an 710069, China; (D.W.); (J.S.); (C.Y.)
| | - Jian Han
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi’an 710069, China; (D.W.); (J.S.); (C.Y.)
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3
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Dong XP, Duan B, Liu J, Donoghue PCJ. Internal anatomy of a fossilized embryonic stage of the Cambrian-Ordovician scalidophoran Markuelia. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220115. [PMID: 36249341 PMCID: PMC9532980 DOI: 10.1098/rsos.220115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
The Wangcun fossil Lagerstätte in Hunan, South China, has yielded hundreds of fossilized embryos of Markuelia hunanensis representing different developmental stages. Internal tissues have only rarely been observed, impeding further understanding of the soft tissue anatomy, phylogenetic affinity and evolutionary significance of Markuelia. In this study, we used synchrotron radiation X-ray tomographic microscopy (SRXTM) to study a new collection of fossil embryos from the Wangcun fossil Lagerstätte. We describe specimens exhibiting a spectrum of preservation states, the best of which preserves palisade structures underneath the cuticle of the head and tail, distinct from patterns of centripetal mineralization of the cuticle and centrifugal mineralization of hypha-like structures, seen elsewhere in this specimen and other fossils within the same assemblage. Our computed tomographic reconstruction of these mineralization phases preserves the gross morphology of (i) longitudinal structures associated with the tail spines, which we interpret as the proximal ends of longitudinal muscles, and (ii) a ring-shaped structure internal to the introvert, which we interpret as a ring-shaped brain, as anticipated of the cycloneuralian affinity of Markuelia. This is the first record of a fossilized nervous system in a scalidophoran, and the first instance in Orsten-style preservation, opening the potential for further such records within this widespread mode of high-fidelity three-dimensional preservation.
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Affiliation(s)
- Xi-ping Dong
- School of Earth and Space Science, Peking University, Beijing 100871, People's Republic of China
| | - Baichuan Duan
- Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resource, Qingdao 266061, People's Republic of China
| | - Jianbo Liu
- School of Earth and Space Science, Peking University, Beijing 100871, People's Republic of China
| | - Philip C. J. Donoghue
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
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4
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Liu Y, Carlisle E, Zhang H, Yang B, Steiner M, Shao T, Duan B, Marone F, Xiao S, Donoghue PCJ. Saccorhytus is an early ecdysozoan and not the earliest deuterostome. Nature 2022; 609:541-546. [PMID: 35978194 DOI: 10.1038/s41586-022-05107-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 07/13/2022] [Indexed: 11/09/2022]
Abstract
The early history of deuterostomes, the group composed of the chordates, echinoderms and hemichordates1, is still controversial, not least because of a paucity of stem representatives of these clades2-5. The early Cambrian microscopic animal Saccorhytus coronarius was interpreted as an early deuterostome on the basis of purported pharyngeal openings, providing evidence for a meiofaunal ancestry6 and an explanation for the temporal mismatch between palaeontological and molecular clock timescales of animal evolution6-8. Here we report new material of S. coronarius, which is reconstructed as a millimetric and ellipsoidal meiobenthic animal with spinose armour and a terminal mouth but no anus. Purported pharyngeal openings in support of the deuterostome hypothesis6 are shown to be taphonomic artefacts. Phylogenetic analyses indicate that S. coronarius belongs to total-group Ecdysozoa, expanding the morphological disparity and ecological diversity of early Cambrian ecdysozoans.
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Affiliation(s)
- Yunhuan Liu
- School of Earth Science and Resources, Chang'an University, Xi'an, China
| | - Emily Carlisle
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Huaqiao Zhang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.
| | - Ben Yang
- MNR Key Laboratory of Stratigraphy and Palaeontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
| | - Michael Steiner
- College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, China.,Department of Earth Sciences, Freie Universität Berlin, Berlin, Germany
| | - Tiequan Shao
- School of Earth Science and Resources, Chang'an University, Xi'an, China
| | - Baichuan Duan
- Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resource, Qingdao, China
| | - Federica Marone
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA.
| | - Philip C J Donoghue
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK.
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5
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Ou Q, Shu D, Zhang Z, Han J, Van Iten H, Cheng M, Sun J, Yao X, Wang R, Mayer G. Dawn of complex animal food webs: A new predatory anthozoan (Cnidaria) from Cambrian. Innovation (N Y) 2022; 3:100195. [PMID: 35005675 PMCID: PMC8717384 DOI: 10.1016/j.xinn.2021.100195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/07/2021] [Indexed: 12/03/2022] Open
Abstract
Cnidarians diverged very early in animal evolution; therefore, investigations of the morphology and trophic levels of early fossil cnidarians may provide critical insights into the evolution of metazoans and the origin of modern marine food webs. However, there has been a lack of unambiguous anthozoan cnidarians from Ediacaran assemblages, and undoubted anthozoans from the Cambrian radiation of metazoans are very rare and lacking in ecological evidence. Here, we report a new polypoid cnidarian, Nailiana elegans gen. et sp. nov., represented by multiple solitary specimens from the early Cambrian Chengjiang biota (∼520 Ma) of South China. These specimens show eight unbranched tentacles surrounding a single opening into the gastric cavity, which may have born multiple mesenteries. Thus, N. elegans displays a level of organization similar to that of extant cnidarians. Phylogenetic analyses place N. elegans in the stem lineage of Anthozoa and suggest that the ancestral anthozoan was a soft-bodied, solitary polyp showing octoradial symmetry. Moreover, one specimen of the new polyp preserves evidence of predation on an epifaunal lingulid brachiopod. This case provides the oldest direct evidence of macrophagous predation, the advent of which may have triggered the emergence of complex trophic/ecological relationships in Cambrian marine communities and spurred the explosive radiation of animal body plans. Polypoid animal from early Cambrian of China is a stem-group anthozoan cnidarian Anthozoan ancestor inferred to be soft-bodied, solitary polyp of octoradial symmetry The new anthozoan provides the oldest direct evidence of macrophagous predation Macrophagous predation may have triggered complex food webs in early Cambrian
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Affiliation(s)
- Qiang Ou
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China.,Department of Zoology, University of Kassel, Kassel 34132, Germany
| | - Degan Shu
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Zhifei Zhang
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Jian Han
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Heyo Van Iten
- Department of Geology, Hanover College, Hanover, IN 47243, USA.,Cincinnati Museum Center, Department of Invertebrate Paleontology, 1301 Western Avenue, Cincinnati, OH 45203, USA
| | - Meirong Cheng
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Jie Sun
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Xiaoyong Yao
- School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
| | - Rong Wang
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Georg Mayer
- Department of Zoology, University of Kassel, Kassel 34132, Germany
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6
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Tube-dwelling in early animals exemplified by Cambrian scalidophoran worms. BMC Biol 2021; 19:243. [PMID: 34772414 PMCID: PMC8588615 DOI: 10.1186/s12915-021-01172-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 10/22/2021] [Indexed: 11/17/2022] Open
Abstract
Background The radiation of ecdysozoans (moulting animals) during the Cambrian gave rise to panarthropods and various groups of worms including scalidophorans, which played an important role in the elaboration of early marine ecosystems. Although most scalidophorans were infaunal burrowers travelling through soft sediment at the bottom of the sea, Selkirkia lived inside a tube. Results We explore the palaeobiology of these tubicolous worms, and more generally the origin and evolutionary significance of tube-dwelling in early animals, based on exceptionally preserved fossils from the early Cambrian Chengjiang Lagerstätte (Stage 3, China) including a new species, Selkirkia transita sp. nov. We find that the best phylogenetic model resolves Selkirkia as a stem-group priapulid. Selkirkia secreted a protective cuticular thickening, the tube, inside which it was able to move during at least part of its life. Partly based on measured growth patterns, we construe that this tube was separated from the trunk during a moulting process that has no direct equivalent in other scalidophorans. Although the ontogeny of Selkirkia is currently unknown, we hypothesize that its conical tube might have had the same ecological function and possibly even deep development origin as the lorica, a protective cuticular thickening found in larval priapulids and adult loriciferans. Selkirkia is seen as a semi-sedentary animal capable of very shallow incursions below the water/sediment interface, possibly for feeding or during the tube-secreting phase. Brachiopod epibionts previously reported from the Xiaoshiba Lagerstätte (ca. 514 Ma) also presumably occur in Selkirkia sinica from Chengjiang (ca. 518 Ma). Conclusions Our critical and model-based approach provides a new phylogenetic framework for Scalidophora, upon which to improve in order to study the evolution of morphological characters in this group. Tube-dwelling is likely to have offered Selkirkia better protection and anchoring to sediment and has developed simultaneously in other Cambrian animals such as hemichordates, annelids or panarthropods. Often lost in modern representatives in favour of active infaunal lifestyles, tube-dwelling can be regarded as an early evolutionary response of various metazoans to increasing environmental and biological pressure in Cambrian marine ecosystems. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01172-4.
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7
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Howard RJ, Edgecombe GD, Shi X, Hou X, Ma X. Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan. BMC Evol Biol 2020; 20:156. [PMID: 33228518 PMCID: PMC7684930 DOI: 10.1186/s12862-020-01720-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 11/08/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ecdysozoa are the moulting protostomes, including arthropods, tardigrades, and nematodes. Both the molecular and fossil records indicate that Ecdysozoa is an ancient group originating in the terminal Proterozoic, and exceptional fossil biotas show their dominance and diversity at the beginning of the Phanerozoic. However, the nature of the ecdysozoan common ancestor has been difficult to ascertain due to the extreme morphological diversity of extant Ecdysozoa, and the lack of early diverging taxa in ancient fossil biotas. RESULTS Here we re-describe Acosmia maotiania from the early Cambrian Chengjiang Biota of Yunnan Province, China and assign it to stem group Ecdysozoa. Acosmia features a two-part body, with an anterior proboscis bearing a terminal mouth and muscular pharynx, and a posterior annulated trunk with a through gut. Morphological phylogenetic analyses of the protostomes using parsimony, maximum likelihood and Bayesian inference, with coding informed by published experimental decay studies, each placed Acosmia as sister taxon to Cycloneuralia + Panarthropoda-i.e. stem group Ecdysozoa. Ancestral state probabilities were calculated for key ecdysozoan nodes, in order to test characters inferred from fossils to be ancestral for Ecdysozoa. Results support an ancestor of crown group ecdysozoans sharing an annulated vermiform body with a terminal mouth like Acosmia, but also possessing the pharyngeal armature and circumoral structures characteristic of Cambrian cycloneuralians and lobopodians. CONCLUSIONS Acosmia is the first taxon placed in the ecdysozoan stem group and provides a constraint to test hypotheses on the early evolution of Ecdysozoa. Our study suggests acquisition of pharyngeal armature, and therefore a change in feeding strategy (e.g. predation), may have characterised the origin and radiation of crown group ecdysozoans from Acosmia-like ancestors.
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Affiliation(s)
- Richard J Howard
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall, TR10 9TA, UK
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Gregory D Edgecombe
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Xiaomei Shi
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Chenggong Campus, Kunming, 650500, China
| | - Xianguang Hou
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China.
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Chenggong Campus, Kunming, 650500, China.
| | - Xiaoya Ma
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China.
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Chenggong Campus, Kunming, 650500, China.
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall, TR10 9TA, UK.
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8
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Edgecombe GD. Arthropod Origins: Integrating Paleontological and Molecular Evidence. ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2020. [DOI: 10.1146/annurev-ecolsys-011720-124437] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phylogenomics underpins a stable and mostly well-resolved hypothesis for the interrelationships of extant arthropods. Exceptionally preserved fossils are integrated into this framework by coding their morphological characters, as exemplified by total-evidence dating approaches that treat fossils as dated tips in analyses numerically dominated by molecular data. Cambrian fossils inform on the sequence of character acquisition in the arthropod stem group and in the stems of its main extant clades. The arthropod head problem incorporates unique appendage combinations and remains of the nervous system in fossils into a scheme mostly based on neuroanatomy and Hox expression domains for extant forms. Molecular estimates of arthropod origins in the Cryogenian or Ediacaran predate a coherent picture from the arthropod fossil record, which commences as trace fossils in the earliest Cambrian. Probabilistic morphological clock analysis of trilobites, which exemplify the earliest arthropod body fossils, supports a Cambrian origin, without the need to posit an unfossilized Ediacaran history.
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Affiliation(s)
- Gregory D. Edgecombe
- Department of Earth Sciences, The Natural History Museum, London SW7 5BD, United Kingdom
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9
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Wang D, Vannier J, Yang XG, Sun J, Sun YF, Hao WJ, Tang QQ, Liu P, Han J. Cuticular reticulation replicates the pattern of epidermal cells in lowermost Cambrian scalidophoran worms. Proc Biol Sci 2020; 287:20200470. [PMID: 32370674 DOI: 10.1098/rspb.2020.0470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cuticle of ecdysozoans (Panarthropoda, Scalidophora, Nematoida) is secreted by underlying epidermal cells and renewed via ecdysis. We explore here the relationship between epidermis and external cuticular ornament in stem-group scalidophorans from the early Cambrian of China (Kuanchuanpu Formation; ca 535 Ma) that had two types of microscopic polygonal cuticular networks with either straight or microfolded boundaries. Detailed comparisons with modern scalidophorans (priapulids) indicate that these networks faithfully replicate the cell boundaries of the epidermis. This suggests that the cuticle of early scalidophorans formed through the fusion between patches of extracellular material secreted by epidermal cells, as observed in various groups of present-day ecdysozoans, including arthropods. Key genetic, biochemical and mechanical processes associated with ecdysis and cuticle formation seem to have appeared very early (at least not later than 535 Ma) in the evolution of ecdysozoans. Microfolded reticulation is likely to be a mechanical response to absorbing contraction exerted by underlying muscles. The polygonal reticulation in early and extant ecdysozoans is clearly a by-product of the epidermal cell pavement and interacted with the sedimentary environment.
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Affiliation(s)
- Deng Wang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China.,Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622, Villeurbanne, France
| | - Jean Vannier
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622, Villeurbanne, France
| | - Xiao-Guang Yang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Jie Sun
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Yi-Fei Sun
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Wen-Jing Hao
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Qing-Qin Tang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Ping Liu
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
| | - Jian Han
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, People's Republic of China
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10
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Kesidis G, Slater BJ, Jensen S, Budd GE. Caught in the act: priapulid burrowers in early Cambrian substrates. Proc Biol Sci 2020; 286:20182505. [PMID: 30963879 DOI: 10.1098/rspb.2018.2505] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
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.
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Affiliation(s)
- Giannis Kesidis
- 1 Department of Earth Sciences (Palaeobiology), Uppsala University , Villavägen 16, 75236 Uppsala , Sweden
| | - Ben J Slater
- 1 Department of Earth Sciences (Palaeobiology), Uppsala University , Villavägen 16, 75236 Uppsala , Sweden
| | - Sören Jensen
- 2 Área de Paleontología, Facultad de Ciencias, Universidad de Extremadura , 06006 Badajoz , Spain
| | - Graham E Budd
- 1 Department of Earth Sciences (Palaeobiology), Uppsala University , Villavägen 16, 75236 Uppsala , Sweden
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11
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Chen Z, Zhou C, Yuan X, Xiao S. Death march of a segmented and trilobate bilaterian elucidates early animal evolution. Nature 2019; 573:412-415. [PMID: 31485079 DOI: 10.1038/s41586-019-1522-7] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Accepted: 07/30/2019] [Indexed: 11/09/2022]
Abstract
The origin of motility in bilaterian animals represents an evolutionary innovation that transformed the Earth system. This innovation probably occurred in the late Ediacaran period-as evidenced by an abundance of trace fossils (ichnofossils) dating to this time, which include trails, trackways and burrows1-3. However, with few exceptions4-8, the producers of most of the late Ediacaran ichnofossils are unknown, which has resulted in a disconnection between the body- and trace-fossil records. Here we describe the fossil of a bilaterian of the terminal Ediacaran period (dating to 551-539 million years ago), which we name Yilingia spiciformis (gen. et sp. nov). This body fossil is preserved along with the trail that the animal produced during a death march. Yilingia is an elongate and segmented bilaterian with repetitive and trilobate body units, each of which consists of a central lobe and two posteriorly pointing lateral lobes, indicating body and segment polarity. Yilingia is possibly related to panarthropods or annelids, and sheds light on the origin of segmentation in bilaterians. As one of the few Ediacaran animals demonstrated to have produced long and continuous trails, Yilingia provides insights into the identity of the animals that were responsible for Ediacaran trace fossils.
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Affiliation(s)
- Zhe Chen
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.,Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China
| | - Chuanming Zhou
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.,CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
| | - Xunlai Yuan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China. .,Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China. .,University of Chinese Academy of Sciences, Beijing, China.
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA.
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12
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Wang D, Vannier J, Schumann I, Wang X, Yang XG, Komiya T, Uesugi K, Sun J, Han J. Origin of ecdysis: fossil evidence from 535-million-year-old scalidophoran worms. Proc Biol Sci 2019; 286:20190791. [PMID: 31288707 DOI: 10.1098/rspb.2019.0791] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
With millions of extant species, ecdysozoans (Scalidophora, Nematoida and Panarthropoda) constitute a major portion of present-day biodiversity. All ecdysozoans secrete an exoskeletal cuticle which must be moulted periodically and replaced by a larger one. Although moulting (ecdysis) has been recognized in early Palaeozoic panarthropods such as trilobites and basal groups such as anomalocaridids and lobopodians, the fossil record lacks clear evidence of ecdysis in early scalidophorans, largely because of difficulties in recognizing true exuviae. Here, we describe two types of exuviae in microscopic scalidophoran worms from the lowermost Cambrian Kuanchuanpu Formation ( ca 535 Ma) of China and reconstruct their moulting process. These basal scalidophorans moulted in a manner similar to that of extant priapulid worms, extricating themselves smoothly from their old tubular cuticle or turning their exuviae inside out like the finger of a glove. This is the oldest record of moulting in ecdysozoans. We also discuss the origin of ecdysis in the light of recent molecular analyses and the significance of moulting in the early evolution of animals.
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Affiliation(s)
- Deng Wang
- 1 State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University , Xi'an 710069 , People's Republic of China.,2 Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), Université Claude Bernard Lyon 1 , Villeurbanne Cedex 69622 , France
| | - Jean Vannier
- 2 Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), Université Claude Bernard Lyon 1 , Villeurbanne Cedex 69622 , France
| | - Isabell Schumann
- 3 Department of Genetics, University of Leipzig , Talstraße 33, 04103 Leipzig , Germany.,4 Molecular Evolution & Animal Systematics, Institute of Biology, University of Leipzig , Talstraße 33, 04103 Leipzig , Germany
| | - Xing Wang
- 5 Qingdao Institute of Marine Geology, China Geological Survey , Qingdao 266071 , People's Republic of China
| | - Xiao-Guang Yang
- 1 State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University , Xi'an 710069 , People's Republic of China
| | - Tsuyoshi Komiya
- 6 Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo , Tokyo 153-8902 , Japan
| | - Kentaro Uesugi
- 7 Japan Synchrotron Radiation Research Institute (JASRI) , 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo , Japan
| | - Jie Sun
- 1 State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University , Xi'an 710069 , People's Republic of China
| | - Jian Han
- 1 State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University , Xi'an 710069 , People's Republic of China
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13
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Cui H, Xiao S, Cai Y, Peek S, Plummer RE, Kaufman AJ. Sedimentology and chemostratigraphy of the terminal Ediacaran Dengying Formation at the Gaojiashan section, South China. GEOLOGICAL MAGAZINE 2019; n/a:10.1017/S0016756819000293. [PMID: 31631899 PMCID: PMC6800678 DOI: 10.1017/s0016756819000293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The late Ediacaran Dengying Formation (ca. 551.1-538.8 Ma) in South China is one of two successions where Ediacara-type macrofossils are preserved in carbonate facies along with skeletal fossils and bilaterian animal traces. Given the remarkable thickness of carbonate-bearing strata deposited in less than 12.3 million years, the Dengying Formation holds the potential for a relatively continuous chemostratigraphic profile for the terminal Ediacaran stage. In this study, a detailed sedimentological and chemostratigraphic (δ13Ccarb, δ18Ocarb, δ13Corg, δ34Spyrite, and 87Sr/86Sr) investigation was conducted on the Dengying Formation at the Gaojiashan section, Ningqiang County of the southern Shaanxi Province, South China. Sedimentological results reveal an overall shallow marine depositional environment. Carbonate breccia, void-filling botryoidal precipitates, and aragonite crystal fans are common in the Algal Dolomite Member of the Dengying Formation, suggesting that peritidal facies were repeatedly karstified. The timing of karstification was likely early, probably soon after the deposition of the dolomite sediments. The presence of authigenic aragonite cements suggests high alkalinity in the terminal Ediacaran ocean. Geochemical analysis of micro-drilled samples shows that distinct compositions are registered in different carbonate phases, which should be considered when constructing chemostratigraphic profiles representative of true temporal variations in seawater chemistry. Integrated chemostratigraphic data suggest enhanced burial of organic carbon and pyrite, and the occurrence of extensive marine anoxia (at least in the Gaojiashan Member). Rapid basinal subsidence and carbonate accumulation during a time of elevated seawater alkalinity and increased rates of pyrite burial may have facilitated the evolutionary innovation of early biomineralizing metazoans.
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Affiliation(s)
- Huan Cui
- Research Group of Analytical, Environmental and Geo- Chemistry (AMGC), Division of Earth System Science, Vrije Universiteit Brussel (VUB), Brussels 1050, Belgium
- ET-HOME (Evolution and Tracers of the Habitability of Mars and Earth) Astrobiology Research Consortium, Belgium
- NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Department of Geology, University of Maryland, College Park, MD 20742, USA
- Author for correspondence: (H. Cui) or (H. Cui), Present address: Research Group of AMGC, Free University of Brussels (VUB), Brussels 1050, Belgium
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Yaoping Cai
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environment, Department of Geology, Northwest University, Xi’an 710069, China
| | - Sara Peek
- Department of Geology, University of Maryland, College Park, MD 20742, USA
- United States Geological Survey, Menlo Park, CA 94025, USA
| | - Rebecca E. Plummer
- Department of Geology, University of Maryland, College Park, MD 20742, USA
- Hydrology and Remote Sensing Laboratory, Beltsville Agricultural Research Center, US Department of Agriculture, Beltsville, MD 20705 USA
| | - Alan J. Kaufman
- Department of Geology, University of Maryland, College Park, MD 20742, USA
- Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742, USA
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14
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Zhang X, Liu W, Isozaki Y, Sato T. Centimeter-wide worm-like fossils from the lowest Cambrian of South China. Sci Rep 2017; 7:14504. [PMID: 29109509 PMCID: PMC5674079 DOI: 10.1038/s41598-017-15089-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 10/20/2017] [Indexed: 11/09/2022] Open
Abstract
The trace fossil record implies that large worm-like animals were in place along with the skeletonizing organisms during the initial stage of the Cambrian explosion. Body fossils of large worms, however, have so far not been found. Here, we describe a large, soft-bodied, worm-like organism, Vittatusivermis annularius gen. et sp. nov. from the lowest Cambrian of South China, which is constrained to the Fortunian Age (541-529 Ma) of the Cambrian Period. The elongate body of Vittatusivermis was large enough to have supported organ systems and a fluid skeleton that facilitated peristaltic locomotion, thus allowing for more complex patterns of movement than those of flatworms. Its occurrence on the same bedding surface as trace fossils suggests that Vittatusivermis might have produced epichnial trails and shallow burrows on and within sediments. Therefore, Vittatusivermis is likely to have been one of the long expected producers of trace fossils in the earliest Cambrian.
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Affiliation(s)
- Xingliang Zhang
- State Key Laboratory of the Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environment, Department of Geology, Northwest University, Xi'an, 710069, PR China.
| | - Wei Liu
- State Key Laboratory of the Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environment, Department of Geology, Northwest University, Xi'an, 710069, PR China
| | - Yukio Isozaki
- Department of Earth Science and Astronomy, University of Tokyo, Tokyo, 153-8902, Japan
| | - Tomohiko Sato
- Department of Earth Science and Astronomy, University of Tokyo, Tokyo, 153-8902, Japan
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15
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Giribet G, Edgecombe GD. Current Understanding of Ecdysozoa and its Internal Phylogenetic Relationships. Integr Comp Biol 2017; 57:455-466. [DOI: 10.1093/icb/icx072] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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16
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Abstract
This paper addresses the taphonomic processes responsible for fossil preservation in calcium phosphate, or phosphatization. Aside from silicification and rarer examples of carbonaceous compression, phosphatization is the only taphonomic mode claimed to preserve putative subcellular structures. Because this fossilization window can record such valuable information, a comprehensive understanding of its patterns of occurrence and the geochemical processes involved in the replication of soft tissues are critical endeavors. Fossil phosphatization was most abundant during the latest Neoproterozoic through the early Paleozoic, coinciding with the decline of non-pelletal phosphorite deposits. Its temporal abundance during this timeframe makes it a particularly valuable window for the study of early animal evolution. Several occurrences of phosphatization from the Ediacaran through the Permian Period, including Doushantuo-type preservation of embryo-like fossils and acritarchs, phosphatized gut tracts within Burgess Shale-type carbonaceous compressions, Orsten-type preservation of meiofaunas, and other cases from the later Paleozoic are reviewed. In addition, a comprehensive description of the geochemical controls of calcium phosphate precipitation from seawater is provided, with a focus on the rates of phosphate nucleation and growth, favorable nucleation substrates, and properties of substrate tissue and pore-fluid chemistry. It is hoped that the paleontological and geochemical summaries provided here offer a practical and valuable guide to the Neoproterozoic–Paleozoic phosphatization window.
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17
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Han J, Morris SC, Ou Q, Shu D, Huang H. Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China). Nature 2017; 542:228-231. [PMID: 28135722 DOI: 10.1038/nature21072] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 12/22/2016] [Indexed: 02/01/2023]
Abstract
Deuterostomes include the group we belong to (vertebrates) as well as an array of disparate forms that include echinoderms, hemichordates and more problematic groups such as vetulicolians and vetulocystids. The Cambrian fossil record is well-populated with representative examples, but possible intermediates are controversial and the nature of the original deuterostome remains idealized. Here we report millimetric fossils, Saccorhytus coronarius nov. gen., nov. sp., from an Orsten-like Lagerstätte from the earliest Cambrian period of South China, which stratigraphically are amongst the earliest of deuterostomes. The bag-like body bears a prominent mouth and associated folds, and behind them up to four conical openings on either side of the body as well as possible sensory structures. An anus may have been absent, and correspondingly the lateral openings probably served to expel water and waste material. This new form has similarities to both the vetulicolians and vetulocystids and collectively these findings suggest that a key step in deuterostome evolution was the development of lateral openings that subsequently were co-opted as pharyngeal gills. Depending on its exact phylogenetic position, the meiofaunal habit of Saccorhytus may help to explain the major gap between divergence times seen in the fossil record and estimates based on molecular clocks.
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Affiliation(s)
- Jian Han
- State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Simon Conway Morris
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
| | - Qiang Ou
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China.,Department of Zoology, University of Kassel, Kassel 34132, Germany
| | - Degan Shu
- State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Hai Huang
- College of Petroleum Engineering, Xi'an Shiyou University, Xi'an 710065, China
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18
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Zhang H, Xiao S, Liu Y, Yuan X, Wan B, Muscente AD, Shao T, Gong H, Cao G. Armored kinorhynch-like scalidophoran animals from the early Cambrian. Sci Rep 2015; 5:16521. [PMID: 26610151 PMCID: PMC4660871 DOI: 10.1038/srep16521] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 10/14/2015] [Indexed: 11/09/2022] Open
Abstract
Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period.
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Affiliation(s)
- Huaqiao Zhang
- Key Laboratory of Economic Stratigraphy and Palaeogeography, Chinese Academy of Sciences (Nanjing Institute of Geology and Palaeontology), Nanjing 210008, China
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Yunhuan Liu
- College of Earth Science and Resources, Chang'an University, Xi'an 710054, China.,State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xunlai Yuan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Bin Wan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
| | - A D Muscente
- Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Tiequan Shao
- College of Earth Science and Resources, Chang'an University, Xi'an 710054, China
| | - Hao Gong
- Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Guohua Cao
- Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA 24061, USA
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Abstract
The foundation of the diverse metazoan nervous systems is laid by embryonic patterning mechanisms, involving the generation and movement of neural progenitors and their progeny. Here we divide early neurogenesis into discrete elements, including origin, pattern, proliferation, and movement of neuronal progenitors, which are controlled by conserved gene cassettes. We review these neurogenetic mechanisms in representatives of the different metazoan clades, with the goal to build a conceptual framework in which one can ask specific questions, such as which of these mechanisms potentially formed part of the developmental "toolkit" of the bilaterian ancestor and which evolved later.
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Affiliation(s)
- Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Angelika Stollewerk
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
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20
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Liu Y, Li Y, Shao T, Zhang H, Wang Q, Qiao J. Quadrapyrgites from the lower Cambrian of South China: growth pattern, post-embryonic development, and affinity. CHINESE SCIENCE BULLETIN 2014. [DOI: 10.1007/s11434-014-0481-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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