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Mandibulate convergence in an armoured Cambrian stem chelicerate
Aria, Cedric1,4; Caron, Jean-Bernard1,2,3
AbstractBackground: Chelicerata represents a vast clade of mostly predatory arthropods united by a distinctive body plan throughout the Phanerozoic. Their origins, however, with respect to both their ancestral morphological features and their related ecologies, are still poorly understood. In particular, it remains unclear whether their major diagnostic characters were acquired early on, and their anatomical organization rapidly constrained, or if they emerged from a stem lineage encompassing an array of structural variations, based on a more labile "panchelicerate" body plan. Results: In this study, we reinvestigated the problematic middle Cambrian arthropod Habelia optata Walcott from the Burgess Shale, and found that it was a close relative of Sanctacaris uncata Briggs and Collins (in Habeliida, ord. nov.), both retrieved in our Bayesian phylogeny as stem chelicerates. Habelia possesses an exoskeleton covered in numerous spines and a bipartite telson as long as the rest of the body. Segments are arranged into three tagmata. The prosoma includes a reduced appendage possibly precursor to the chelicera, raptorial endopods connected to five pairs of outstandingly large and overlapping gnathobasic basipods, antennule-like exopods seemingly dissociated from the main limb axis, and, posteriorly, a pair of appendages morphologically similar to thoracic ones. While the head configuration of habeliidans anchors a seven-segmented prosoma as the chelicerate ground pattern, the peculiar size and arrangement of gnathobases and the presence of sensory/tactile appendages also point to an early convergence with the masticatory head of mandibulates. Conclusions: Although habeliidans illustrate the early appearance of some diagnostic chelicerate features in the evolution of euarthropods, the unique convergence of their cephalons with mandibulate anatomies suggests that these traits retained an unusual variability in these taxa. The common involvement of strong gnathal appendages across non-megacheirans Cambrian taxa also illustrates that the specialization of the head as the dedicated food-processing tagma was critical to the emergence of both lineages of extant euarthropods-Chelicerata and Mandibulata-and implies that this diversification was facilitated by the expansion of durophagous niches.
KeywordArthropoda Chelicerata Convergence Macroevolution Cambrian Burgess Shale
Indexed BySCI
Funding ProjectUniversity of Toronto (Dept. of Ecology and Evolution) ; Natural Sciences and Engineering Research Council[341944]
WOS Research AreaEvolutionary Biology ; Genetics & Heredity
WOS SubjectEvolutionary Biology ; Genetics & Heredity
WOS IDWOS:000418937500001
Funding OrganizationUniversity of Toronto (Dept. of Ecology and Evolution) ; Natural Sciences and Engineering Research Council
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Cited Times:12[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorAria, Cedric
Affiliation1.Univ Toronto, Dept Ecol & Evolutionary Biol, Toronto, ON M5S 3B2, Canada
2.Royal Ontario Museum, Dept Nat Hist, Palaeobiol Sect, Toronto, ON M5S 2C6, Canada
3.Univ Toronto, Dept Earth Sci, Toronto, ON M5S 3B1, Canada
4.Chinese Acad Sci, Nanjing Inst Geol & Palaeontol, State Key Lab Palaeobiol & Stratig, Nanjing 210008, Jiangsu, Peoples R China
First Author AffilicationNanjing Institute of Geology and Palaeonotology,CAS
Corresponding Author AffilicationNanjing Institute of Geology and Palaeonotology,CAS
Recommended Citation
GB/T 7714
Aria, Cedric,Caron, Jean-Bernard. Mandibulate convergence in an armoured Cambrian stem chelicerate[J]. BMC EVOLUTIONARY BIOLOGY,2017,17:20.
APA Aria, Cedric,&Caron, Jean-Bernard.(2017).Mandibulate convergence in an armoured Cambrian stem chelicerate.BMC EVOLUTIONARY BIOLOGY,17,20.
MLA Aria, Cedric,et al."Mandibulate convergence in an armoured Cambrian stem chelicerate".BMC EVOLUTIONARY BIOLOGY 17(2017):20.
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