PhD: Fossil ichthyosaurs of Scotland

Ichthyosaurs are sea reptiles that lived during the Age of Dinosaurs. Like modern dolphins, their aquatic adaptations were so complete that they resembled fish and even gave birth underwater to live young. They occupied a wide variety of ecological niches, and some evolved immense sizes. Their fossils have been studied for over 200 years, and while many aspects of their palaeobiology are well-known, important questions remain. For example, several ichthyosaur radiations occurred before their extinction in the Late Cretaceous. Some of these may have been due to replacement after wider extinction events, some due to other factors. One outstanding question is, how did large-eyed and deep-diving-adapted ophthalmosaurid ichthyosaurs, dominant in the Late Jurassic, replace non-ophthalmosaurid forms? This faunal turnover is poorly understood because ichthyosaurs are poorly known during the preceding Middle Jurassic. Fortunately, the Scottish Isle of Skye offers a rare window into northern ichthyosaur diversity during this time. National Museums Scotland holds eight partial skeletons from Skye and elsewhere in Scotland (e.g., Helmsdale), one of which represents the very first vertebrate fossil collected by academic researchers on Skye in 1966. A recent acquisition includes rare skull material and offers new information on juvenile ichthyosaurs. The NMS specimens showcase an unexpected diversity of species but, to date, only one Scottish taxon has ever been named (Dearcmhara shawcrossi). This project will address this, providing new information for estimating northern ichthyosaur diversity during this critical period in ichthyosaur evolution. Because the Skye material covers this critical but undersampled interval, the project will investigate the drivers behind the replacement of non-ophthalmosaurid ichthyosaurs by ophthalmosaurids; did this turnover occur as a competitive replacement within the context of sea-level change or other environmental factors? Similarly, sea reptile composition over this period changed from ichthyosaur-dominated pelagic faunas to pelagic faunas characterised by ichthyosaurs and a more diverse and abundant crocodylomorph and sauropterygian fauna. This project will attempt to constrain the timing of these changes, and to investigate possible drivers for these events.