Data from: Fine-scale appendage structure of the Cambrian trilobitomorph Naraoia spinosa and its ontogenetic and ecological implications

Trilobitomorphs are a species-rich Palaeozoic arthropod assemblage that
unites trilobites with several other lineages that share
similar appendage structure. Post-embryonic development
of the exoskeleton is well documented for some trilobitomorphs, especially
trilobites, but little is known of the ontogeny of their soft parts,
limiting understanding of their autecology. Here we
document appendage structure of
the Cambrian naraoiid trilobitomorph Naraoia spinosa by computed microtomography, resulting in three-dimensional reconstructions of appendages at both juvenile and adult stages. The adult has dense, strong spines on the protopods of post-antennal appendages, implying a predatory/scavenging behavior. Absence of such gnathobasic structures but instead tiny protopodal bristles and a number of endopodal setae suggests a detritus-feeding strategy for the juvenile. Our data add strong morphological evidence for ecological-niche shifting by Cambrian arthropods during their life cycles. A conserved number of appendages across the sampled developmental stages demonstrates that Naraoia ceased budding off new appendages by the mid-juvenile stage.