A re-description of the post-embryonic development of Derocheilocaris remanei Delamare-Deboutteville and Chappuis, 1951 (Mystacocarida) is presented. It includes nine stages, not ten as originally described. The first stage already has a maxillula (though not fully developed) and is, therefore, not an ortho-nauplius as previously reported. Particular focus is on the development of the post-mandibular appendages (maxillula, maxilla, maxilliped) that undergo significant changes during ontogeny, and the development of the so-called ‘toothed furrows’, all of which are good indicators of changes between the stages. The maxilla and maxilliped are quite different from each other in the adult stage, but they develop in a very similar manner, showing very similar morphologies at certain stages. None of the post-mandibular appendages has a fully formed coxa, but only a proximal endite, which is in contrast to some previous interpretations. The development of D. remanei was originally considered very different from that of its transatlantic ‘sister species’, D. typicus, but our observations indicate that this is not the case. Rather, the development of D. typicus and D. remanei is very similar. This implies that not only the adult morphology of Mystacocarida is remarkably conservative, but also the larval sequence. With regard to the feeding system, mystacocaridans have a cephalo-thoracic feeding apparatus including the first pair of trunk limbs modified as maxillipeds, which collaborate with the maxillulae and maxillae in the feeding process. All three limbs are very similar to each other (the main difference is that the maxilliped possesses a vestigial exopod). The feeding system is in both general aspects and in particular details very similar to that of Copepoda and the representatives of the Cambrian taxon Skara. This suggests a close relationship between these three taxa, for which we propose the name Copepodoida. The name refers to specific features found exclusively in copepodans and, in our view, mystacocaridans and the three species of Skara.
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Vol. 31 • No. 4