Letter | Published:

Brain structure resolves the segmental affinity of anomalocaridid appendages

Nature volume 513, pages 538542 (25 September 2014) | Download Citation



Despite being among the most celebrated taxa from Cambrian biotas, anomalocaridids (order Radiodonta) have provoked intense debate about their affinities within the moulting-animal clade that includes Arthropoda. Current alternatives identify anomalocaridids as either stem-group euarthropods1,2,3, crown-group euarthropods near the ancestry of chelicerates4, or a segmented ecdysozoan lineage with convergent similarity to arthropods in appendage construction5. Determining unambiguous affinities has been impeded by uncertainties about the segmental affiliation of anomalocaridid frontal appendages. These structures are variably homologized with jointed appendages of the second (deutocerebral) head segment, including antennae and ‘great appendages’ of Cambrian arthropods, or with the paired antenniform frontal appendages of living Onychophora and some Cambrian lobopodians. Here we describe Lyrarapax unguispinus, a new anomalocaridid from the early Cambrian Chengjiang biota, southwest China, nearly complete specimens of which preserve traces of muscles, digestive tract and brain. The traces of brain provide the first direct evidence for the segmental composition of the anomalocaridid head and its appendicular organization. Carbon-rich areas in the head resolve paired pre-protocerebral ganglia at the origin of paired frontal appendages. The ganglia connect to areas indicative of a bilateral pre-oral brain that receives projections from the eyestalk neuropils and compound retina. The dorsal, segmented brain of L. unguispinus reinforces an alliance between anomalocaridids and arthropods rather than cycloneuralians. Correspondences in brain organization between anomalocaridids and Onychophora resolve pre-protocerebral ganglia, associated with pre-ocular frontal appendages, as characters of the last common ancestor of euarthropods and onychophorans. A position of Radiodonta on the euarthropod stem-lineage implies the transformation of frontal appendages to another structure in crown-group euarthropods, with gene expression and neuroanatomy providing strong evidence that the paired, pre-oral labrum is the remnant of paired frontal appendages1.

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Data deposits

This published work and the nomenclatural acts it contains have been deposited in ZooBank under accession number http://zoobank.org/urn:lsid:zoobank.org:pub:189DCAFF-0DD6-49C2-BE80-E999DDF059C1.


  1. 1.

    A palaeontological solution to the arthropod head problem. Nature 417, 271–275 (2002)

  2. 2.

    , , , & The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science 323, 1597–1600 (2009)

  3. 3.

    , & Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Commun. 4, 2485 (2013)

  4. 4.

    , , , & Functional morphology, ontogeny and evolution of mantis shrimp-like predators in the Cambrian. Palaeontology 55, 369–399 (2012)

  5. 5.

    & in Originations, Radiations and Biodiversity Changes: Evidences from the Chinese Fossil Record (eds et al.) 139–158, 847–850 (Science Press, 2006)

  6. 6.

    , , & A suspension-feeding anomalocarid from the Early Cambrian. Nature 507, 496–499 (2014)

  7. 7.

    & Morphology of Anomalocaris canadensis from the Burgess Shale. J. Paleontol. 88, 68–91 (2014)

  8. 8.

    & The oral cone of Anomalocaris is not a classic “peytoia”. Naturwissenschaften 99, 501–504 (2012)

  9. 9.

    et al. Acute vision in the giant Cambrian predator Anomalocaris and the origin of compound eyes. Nature 480, 237–240 (2011)

  10. 10.

    Arthropod body-plan evolution in the Cambrian with an example from anomalocaridid muscle. Lethaia 31, 197–210 (1998)

  11. 11.

    , , & Complex brain and optic lobes in an early Cambrian arthropod. Nature 490, 258–261 (2012)

  12. 12.

    , , , & Chelicerate neural ground pattern in a Cambrian great appendage arthropod. Nature 17, 364–367 (2013)

  13. 13.

    in Arthropod Brain: Its Evolution, Development, Structure and Function (ed. ) 159–180 (John Wiley, 1987)

  14. 14.

    & Neural development in Onychophora (velvet worms) suggests a step-wise evolution of segmentation in the nervous system of Panarthropoda. Dev. Biol. 335, 263–275 (2009)

  15. 15.

    & Distribution of serotonin in the trunk of Metaperipatus blainvillei (Onychophora, Peripatopsidae): implications for the evolution of the nervous system in Arthropoda. J. Comp. Neurol. 507, 1196–1208 (2008)

  16. 16.

    , , & The involvement of engrailed and wingless during segmentation in the onychophoran Euperipatoides kanangrensis (Peripatopsidae: Onychophora) (Reid 1996). Dev. Genes Evol. 219, 249–264 (2009)

  17. 17.

    , , , & The organization and evolutionary implications of neuropils and their neurons in the brain of the onychophoran Euperipatoides rowelli. Arthropod Struct. Dev. 35, 169–196 (2006)

  18. 18.

    , , & A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods. BMC Evol. Biol. 10, 255 (2010)

  19. 19.

    The use of osmium in the fixation and staining of tissue. Proc. R. Soc. Lond. B 147, 185–199 (1957)

  20. 20.

    , , , & Arthropod phylogeny: onychophoran brain organization suggests an archaic relationship with a chelicerate stem lineage. Proc. R. Soc. B 273, 1857–1866 (2006)

  21. 21.

    The evolution of arthropod limbs. Biol. Rev. Camb. Philos. Soc. 79, 253–300 (2004)

  22. 22.

    & The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Dev. Genes Evol. 216, 395–415 (2006)

  23. 23.

    A new arthropod from the Early Cambrian of north Greenland, with a ‘great appendage’-like antennula. Zool. J. Linn. Soc. 158, 477–500 (2010)

  24. 24.

    & The affinities of the cosmopolitan arthropod Isoxys and its implications for the origin of arthropods. Lethaia 46, 540–550 (2013)

  25. 25.

    , , & Stages of embryonic development in the amphipod crustacean, Parhyale hawaiensis. Genesis 42, 124–149 (2005)

  26. 26.

    , & Homeotic evidence for the appendicular origin of the labrum in Tribolium castaneum. Dev. Genes Evol. 211, 96–102 (2001)

  27. 27.

    , , & Morphological and molecular data argue for the labrum being non-apical, articulated, and the appendage of the intercalary segment in the locust. Arthropod Struct. Dev. 31, 65–76 (2002)

  28. 28.

    Arthropod Brains: Evolution, Functional Elegance, and Historical Significance Ch 9, 427–446 (Belknap, 2012)

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This work was supported by the National Natural Science Foundation of China (U1302232, 41372031 and 40962001), a Leverhulme Trust Research Project Grant (F/00 696/T), by the Center for Insect Science, University of Arizona, and by a grant from the Air Force Research Laboratory (FA86511010001) to N.J.S. We thank T. Goral for assistance with energy dispersive X-ray spectroscopy. We acknowledge A. Daley’s advice about anomalocaridid anatomy.

Author information


  1. Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China

    • Peiyun Cong
    • , Xiaoya Ma
    •  & Xianguang Hou
  2. Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

    • Xiaoya Ma
    •  & Gregory D. Edgecombe
  3. Department of Neuroscience, University of Arizona, Tucson, Arizona 85721, USA

    • Nicholas J. Strausfeld
  4. Center for Insect Science, University of Arizona, Tucson, Arizona 85721, USA

    • Nicholas J. Strausfeld


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Fossil data were analysed by all authors, all of whom contributed to the text.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Xianguang Hou or Nicholas J. Strausfeld.

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Supplementary information

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    Supplementary Information

    This file contains details of specimen preservation, morphological description of specimens, description of phylogenetic analysis, and supplementary references. This file was replaced on 21 July 2014.

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    Supplementary Data

    Dataset of characters for phylogenetic analysis in Nexus format (editable in Mesquite or NDE).

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