Small theropod-dominated dinosaur footprint assemblages in the Middle Jurassic Valtos Sandstone and Kilmaluag Formations on the Isle of Skye, Scotland.

Abstract

Middle Jurassic deposits on the Isle of Skye, Scotland, are improving our understanding of the distribution, palaeoenvironmental preferences and behaviour of theropod dinosaurs from a time when the global fossil record is sparse. Here, we describe and classify 185 Bathonian-aged ex situ dinosaur tracks from Skye's Trotternish Peninsula-many described for the first time and imaged using photogrammetric techniques-into four morphotypes within a new Hebridean series. In the freshwater, closed-lagoonal Kilmaluag Formation at Lùb Score, smaller morphotypes are more abundant than larger equivalents in the freshwater-brackish fluviodeltaic Valtos Sandstone Formation at Valtos. Although assessable outcrops of track-bearing horizons are limited, we infer that the proximity to, or suitability of, specific palaeoenvironments for different-sized trackmakers may influence assemblage composition. Scarce surfaces with multiple tracks indicate potential trackmaker behaviours in respective palaeoenvironments, including foraging at Valtos and post-hatchling care at Lùb Score. The tracks most likely represent traces of a large megalosaurid and multiple smaller-bodied basal coelurosaurian or non-coelurosaurian (e.g. Ceratosauria, Megalosauroidea, Allosauroidea) theropods. The documentation of these trackmakers and their behaviours further enriches our understanding of dinosaur faunas during this poorly known time.