Data from: Three new naraoiid species from the Burgess Shale, with a morphometric and phylogenetic reinvestigation of Naraoiidae

Naraoiids are non‐biomineralized euarthropods characterized by the
complete fusion of post‐cephalic tergo‐pleurae into a single shield, as
well as an extensively ramified digestive tract. Ranging from the early
Cambrian to the late Silurian (Pridoli), these arthropods of simple
appearance have traditionally been associated with the early
diversification of trilobites and their close relatives, but the
interrelationships and affinities of naraoiids within Artiopoda remain
poorly characterized. Three new species from the Burgess Shale (middle
Cambrian, Stage 5) of British Columbia, Canada, are described here:
Misszhouia canadensis sp. nov., from Marble Canyon (Kootenay National
Park), the first species belonging to the genus Misszhouia outside of
China; Naraoia magna sp. nov., from Marble Canyon and also from the
Raymond Quarry (Yoho National Park), the largest species of Naraoia
described thus far, reaching up to 9 cm in length; and Naraoia arcana sp.
nov., from two sublocalities on Mount Stephen (Yoho National Park),
defined by its unusual combination of spines. This new material shows that
gut morphology is no longer a reliable character to distinguish Misszhouia
from Naraoia. We demonstrate that Naraoia and Misszhouia can instead be
discriminated morphometrically, based on simple metrics of the dorsal
exoskeleton. Our quantitative results also help with inter‐specific
discrimination and illustrate possible cases of sexual dimorphism.
Phylogenetically, the inclusion of morphometric data adds resolution to
our cladogram, although parsimony and likelihood treatments provide
somewhat different evolutionary scenarios. In all cases, liwiines are
nested within Naraoiidae, resolved as the most derived clade of
trilobitomorph arthropods.