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An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda.

Smith, Martin R. (2020) 'An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda.', Journal of paleontology., 94 (1). pp. 64-69.

Abstract

Nectocaridids are soft-bodied Cambrian organisms that have been controversially interpreted as primitive cephalopods, contradicting the long-held belief that these molluscs evolved from a shell-bearing ancestor. Here I document a new nectocaridid from the Whetstone Gulf formation, extending the group’s range into the Late Ordovician. <i>Nectocotis rusmithi</i> n. gen, n. sp. possesses a robust internal element that resembles a non-mineralized phragmocone or gladius. <i>Nectocotis</i> can be accommodated in the cephalopod total group if (1) cephalopods inherited a non-mineralized shell field from the ancestral mollusc; (2) the earliest cephalopods bore internal shells. This evolutionary scenario would overturn the traditional ectocochleate, <i>Nautilus</i>-like reconstruction, and indicate a trend towards increased metabolic efficiency through the course of Cambrian–Ordovician evolution.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1017/jpa.2019.57
Publisher statement:This article has been published in a revised form in Journal of Paleontology 10.1017/jpa.2019.57. This version is published under a Creative Commons CC-BY-NC-ND. No commercial re-distribution or re-use allowed. Derivative works cannot be distributed. © 2019 The Paleontological Society.
Date accepted:14 June 2019
Date deposited:18 June 2019
Date of first online publication:15 August 2019
Date first made open access:15 February 2020

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