Largest coprolite from a carnivore

Based on dimensions, the largest coprolite (fossilized poo) by a carnivorous animal measures 67.5 centimetres (2 feet 2.5 inches) long – along the central curve – and up to 15.7 centimetres (6.2 inches) wide, as confirmed on 2 March 2020. The coprolite was discovered on a private ranch near the town of Buffalo in South Dakota, USA, in summer 2019. Now known as “Barnum” – named after palaeontologist Barnum Brown who unearthed the first Tyrannosaurus rex remains in 1902 – the specimen is owned by coprolite collector George Frandsen (USA).

Along the outer curve, Barnum measures 75 cm (2 ft 5.5 in) and along the inner curve, 59 cm (1 ft 11 in); its depth varies from 5 to 14 cm (2–5.5 in). The coprolite weighs approximately 9.28 kg (20 lb 7.3 oz). Although removed for measuring purposes, Barnum is generally kept in a protective jacket in order to preserve its structural integrity.

Coprolites are the fossilized droppings of ancient animals. As well as offering an insight into the range and habitat of certain animal types (and sometimes even specific species), the traces of undigested food (known as inclusions) offer an invaluable insight into prehistoric diets.

Independent X-ray fluorescence analysis of Barnum by the Geoarchaeological XRF Laboratory in Albuquerque, New Mexico, USA, revealed high quantities of phosphorus and calcium – a feature consistent with other coprolites produced by carnivores. Its authenticity is supported further by visible fragments of crushed bone and the long, cylindrical shape of the fossil, rounded on one side and flattened on the other, most likely from where it originally dropped onto the ground. Although it can’t be said for certain if this coprolite came from a T. rex, its size and origin (in the Hell Creek Formation) – as well as high quantity of bone – point towards it being the most likely source.

Frandsen also holds the record for largest collection of coprolites – he had 1,277 at the last official count on 1 Aug 2015; he now estimates the collection has swollen to more than 7,000, though this is pending verification. A large proportion of his collection is on display at the South Florida Museum in Bradenton, Florida, USA, and Frandsen also maintains an online archive called the “Poozeum”.