A dynamic and collaborative database for morphogeometric information of trilobites.

Modern morphometric-based approaches provide valuable metrics to quantify and understand macroevolutionary and macroecological patterns and processes. Here we describe TriloMorph, an openly accessible database for morpho-geometric information of trilobites, together with a landmark acquisition protocol. In addition to morphological traits, the database contains contextual data on chronostratigraphic age, geographic location, taxonomic information and lithology of landmarked specimens. In this first version, the dataset has broad taxonomic and temporal coverage and comprises more than 55% of all trilobite genera and 85% of families recorded in the Paleobiology Database through the Devonian. We provide a release of geometric morphometric data of 277 specimens linked to published references. Additionally, we established a Github repository for constant input of morphometric data by multiple contributors and present R functions that help with data retrieval and analysis. This is the first attempt of an online, dynamic and collaborative morphometric repository. By bringing this information into a single open database we enhance the possibility of performing global palaeobiological research, providing a major complement to current occurrence-based databases.

Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic.

Trilobites, key components of early Palaeozoic communities, are considered to have been invariably fully marine. Through the integration of ichnological, palaeobiological, and sedimentological datasets within a sequence-stratigraphical framework, we challenge this assumption. Here, we report uncontroversial trace and body fossil evidence of their presence in brackish-water settings. Our approach allows tracking of some trilobite groups foraying into tide-dominated estuaries. These trilobites were tolerant to salinity stress and able to make use of the ecological advantages offered by marginal-marine environments migrating up-estuary, following salt wedges either reflecting amphidromy or as euryhaline marine wanderers. Our data indicate two attempts of landward exploration via brackish water: phase 1 in which the outer portion of estuaries were colonized by olenids (Furongian-early late Tremadocian) and phase 2 involving exploration of the inner to middle estuarine zones by asaphids (Dapingian-Darriwilian). This study indicates that tolerance to salinity stress arose independently among different trilobite groups.