Gigantic rhizodonts in Scotland’s lochs: The one that got away

James O’Donoghue (UK) Fig. 1. If gigantic rhizodonts still lurked in Scotland’s lochs, anglers might find they are biting off more than they can chew. (Illustration by Megan Whatley.) Every angler dreams of reeling in a prize catch – a 40lb pike perhaps, or a whopper of a salmon. Record-breaking fish fire the imagination as few other creatures can, and the lochs of Scotland have inspired many a fishy tale. However, even the tallest of these stories pale into insignificance when compared with the primeval occupants of the lochs. Had you cast a line there 340 million year ago, you could have ended up as bait yourself. For Scotland’s ancient lakes and rivers held a behemoth of a fish known as Rhizodus hibberti (Fig. 2), which notched up a truly staggering snout-to-tail length of seven metres. It was the ultimate ‘one that got away’, a predator that was half as big again as a great white shark. To this day, it remains the largest freshwater fish ever to have lived. Rhizodonts, the group of fishes to which R. hibberti belonged, may have been the last truly gigantic predators to live in fresh water, suggests palaeontologist Jon Jeffery, an expert on one of the most widely distributed species, Strepsodus. They also have the distinction of being the most primitive ‘tetrapodomorphs’ known. That is, they belong to the group of fishes from which tetrapods descended. Tetrapods are vertebrates that colonised land and includes all amphibians, reptiles, birds and mammals. Fig. 2. Jaw … Read More