Smith, Martin R (2013) Nectocaridid ecology, diversity, and affinity: early origin of a cephalopod-like body plan. Paleobiology, 39 (2). pp. 297-321. ISSN 0094-8373 DOI 10.1666/12029Full text not available from this repository.
Nectocaridids are soft-bodied early to middle Cambrian organisms known from Burgess Shale-type deposits in Canada, China, and Australia. Originally described as unrelated species, they have recently been interpreted as a clade; their flexible tentacles, camera-type eyes, lateral fins, internal gills, axial cavity, and funnel point to a relationship with the cephalopods. However, aspects of this reinterpretation, including the relevance of the group to cephalopod evolution, have been called into question. Here, I examine new and existing nectocaridid material, including a large new form that may represent a sexual dimorph of Nectocaris pteryx. Differences between existing taxa largely represent taphonomic variation between sites and specimens—which provides further constraint on the organisms' anatomy. I revise the morphology of the tentacles and fins, and describe mouthparts and phosphatized gills for the first time. A mathematical analysis supports the presence of the earliest known camera-type eyes, and fluid mechanical considerations suggest that the funnel is optimized for efficient jet propulsion in a low Reynolds number flow regime. Nectocaridids closely resemble coleoid cephalopods, but a position deeper within Cephalopoda raises fewer stratigraphic challenges. Whether its coleoid-like construction reflects common ancestry or profound convergence, the Nectocaris body plan adds substantially to Cambrian disparity, demonstrating the rapid colonization of nektobenthic niches after the Cambrian explosion.
|Additional Information:||High resolution images may be accessed from the related Author url listed above once the paper has been published|
|Uncontrolled Keywords:||NIL AREP; IA65;|
|Subjects:||04 - Palaeobiology|
|Divisions:||04 - Palaeobiology|
|Journal or Publication Title:||Paleobiology|
|Page Range:||pp. 297-321|
|Depositing User:||Sarah Humbert|
|Date Deposited:||31 Mar 2013 21:41|
|Last Modified:||23 Jul 2013 10:05|
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