Data from: Morphometric analysis of Skiagia-plexus acritarchs from the early Cambrian of North Greenland

The Cambrian evolutionary radiations are marked by spectacular biotic
turnovers and the establishment of increasingly tiered food chains. At
their base are primary producers, which in the Cambrian fossil record are
chiefly represented among organic-walled microfossils. The majority of
these microfossil remains have traditionally been attributed to an
informal category of incertae sedis called “acritarchs”, based entirely on
form taxonomy. Acritarch form-taxa have been intensely used for
biostratigraphy, and in large-scale studies of phytoplankton diversity.
However, both prospects have been challenged by cases of taxonomic
inconsistencies and over-splitting arising from the large phenotypic
plasticity seen among these microfossils. The acritarch form-genus Skiagia
stands as an ideal case-study to explore these taxonomic challenges, since
it encompasses a number of form-species widely used in lower Cambrian
biostratigraphy. Moreover, subtle morphological differences among Skiagia
species were suggested to underlie key evolutionary innovations towards
complex reproduction strategies. Here we apply a multivariate morphometric
approach to investigate the morphological variation of Skiagia-plexus
acritarchs using an assemblage sourced from the Buen Formation (Cambrian
Series 2, Stage 3–4) of North Greenland. Our analysis showed that the
specific-level classification of Skiagia discretizes a continuous spectrum
of morphologies. While these findings bring important taxonomic and
biostratigraphic hurdles to light, the unequal frequency distribution of
life cycle stages among Skiagia species suggests that certain elements of
phytoplankton paleobiology are nonetheless captured by Skiagia
form-taxonomy. These results demonstrate the value of using morphometric
tools to explore acritarch phenotypic plasticity and its potential
ontogenetic and paleoecological drivers in Cambrian ecosystems.