SMALL SHELLY FOSSIL TAXONOMIC WRANGLING: SALTERELLA, LIDACONUS, AND THEIR ONGOING AMBIGUITY

SMALL SHELLY FOSSIL TAXONOMIC WRANGLING: SALTERELLA, LIDACONUS, AND THEIR ONGOING AMBIGUITY

Noah Keller, Prescott Vayda, Shuhai Xiao

The Cambrian Period is host to staggering quantities of new-found diversity within the animal kingdom. Due to the increasing number of niches created and the increasing number of species adapting to fill them, the period marked a time of tumult both when it was happening and retrospectively for those among us attempting to describe it.

Enter Salterella, a small shelly fossil that is the oldest seashell in Virginia and that has long been used in North America as a biostratigraphic tool. It is remarkable for its unique skeletal configuration among the animal kingdom: its skeleton consists of a conical biomineralized shell and an infilling of layered, agglutinated sediments. This unique body plan has placed Salterella and its relatives into the isolated Phylum of Agmata. Agmatans are notable not only for the morphological experimentation of the time but also the taxonomic ambiguity these forms present.

Here we seek to resolve one such instance of ambiguity between two agglutinating forms described from the Harkless Formation of western Nevada. Lidaconus and Salterella are both centimeter-scale, curved conical forms known from Cambrian Stage 4 in the region, but are both poorly documented and studied. We use morphological and microstructural analyses to compare specimens of each genus to understand their potential relationship and to clarify the taxonomy of conical forms from the Harkless Formation. This work has implications for the biostratigraphic application of agmatans, and helps us better understand the diversity of this unique group of organisms.