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| Balhuticaris voltae Izquierdo-López & Caron, 2022 |
Highlights:
• Balhuticaris voltae; a bivalved arthropod from the Cambrian Burgess Shale
• It is the largest bivalved arthropod and one of the largest Cambrian arthropods
• It was an agile nektobenthic swimmer with an extremely multisegmented body
• This species increases the ecological and functional disparity of bivalved arthropods
Summary
The origin of mandibulate arthropods can be traced back to the Cambrian period to several carapace-bearing arthropod groups, but their morphological diversity is still not well characterized. Here, we describe Balhuticaris voltae, a bivalved arthropod from the 506-million-year-old Burgess Shale (Marble Canyon, British Columbia, Canada). This species has an extremely elongated and multisegmented body bearing ca. 110 pairs of homonomous biramous limbs, the highest number among Cambrian arthropods, and, at 245 mm, it represents one of the largest Cambrian arthropods known. Its unusual carapace resembles an arch; it covers only the frontalmost section of the body but extends ventrally beyond the legs. Balhuticaris had a complex sensory system and was probably an active swimmer thanks to its powerful paddle-shaped exopods and a long and flexible body. Balhuticaris increases the ecological and functional diversity of bivalved arthropods and suggests that cases of gigantism occurred in more arthropod groups than previously recognized.
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| Reconstruction of Balhuticaris voltae Full body in lateral view (A), close-up of (A) with the morphotype B type of carapace (A.1), close-up of the cephalic area in dorsal view (B), leg (C), and close-up of the telson and caudal rami in dorsal view (D). Artistic reconstruction (E) and alternative artistic reconstruction swimming inverted (F). All reconstructions courtesy of Hugo Salais. Abbreviations: ce, cephalon (head). Scales: A-D) 10 mm. |
Phylum: Arthropoda von Siebold, 1848 (Hegna et al., 2013).
Subphylum: Mandibulata Snodgrass (1938) (Snodgrass, 1938).
Genus: Balhuticaris voltae gen. et sp. nov.
Etymology: Balhuticaris, from Balhūt (Bahamut), a gigantic sea monster from several Persian cosmographies, and the Latin caris, crab. Species name voltae from the Catalan volta, meaning vault or arch-like structure, referring to the shape of the carapace in frontal view.
Diagnosis for genus and species: Bivalved arthropod with a carapace sub-equal to or greater in height than length, covering the frontalmost section of the body and extending anteroventrally beyond the level of the longest cephalothoracic legs; stalked eyes laterally bilobate. Total number of post-cephalic segments ca. 110:10–12 thoracic segments and ca. 100 post-thoracic segments. Each thoracic segment is three times longer than a post-thoracic segment. Caudal rami tripartite, with pseudo-segments bearing elongated setae distally.
Alejandro Izquierdo-López and Jean-Bernard Caron. 2022. Extreme Multisegmentation in A Giant Bivalved Arthropod from the Cambrian Burgess Shale. iScience. 25(7); 104675. DOI: 10.1016/j.isci.2022.104675
