About three dozen specimens of the synziphosuran Limuloides limuloides (Woodward 1865) have been collected from Silurian strata in the Welsh Borderland since 1855, making it a rather rare component of the fauna. Most of these specimens are incomplete, mainly isolated prosomas. Here, a new specimen of the species is described from a single part (no counterpart). It is an articulated prosoma and opisthosoma, lacking a telson, and in apparently full relief. It comes from the lowermost Aston Mudstone Formation (Wenlock: Homerian, probably nassa zone), from a locality close to Aston Dingle near Bishop’s Castle, Shropshire, which is a new locality for L. limuloides, and the specimen is only the third known for this species in the Wenlock.

Eurypterids (sea scorpions) are a group of extinct, marine euchelicerates that have an extensive Palaeozoic record. Despite lacking a biomineralised exoskeleton, eurypterids are abundantly preserved within select deposits. These collections make statistical analyses comparing the morphology of different genera possible. However, eurypterid shape has not yet been documented with modern geometric morphometric tools. Here, we summarise the previous statistical assessments of eurypterid morphology and expand this research by presenting landmark and semi-landmark analyses of 115 eurypterid specimens within the suborder Eurypterina. We illustrate that lateral compound eye morphology and position drives specimen placement in morphospace and separates proposed apex predators from more generalist forms. Additionally, evidence for size clusters in Eurypterus that may reflect ontogeny is uncovered. We highlight the use of geometric morphometric analyses in supporting the naming of new taxa and demonstrate that these shape data represent a novel means of understanding inter-generic ontogenetic trajectories and uncovering developmental changes within the diverse euarthropod group.