Poo unveiled

March 5, 2009 06:49 by Kate Phillips

Curator Wayne Gerdtz with Jurassic poo. Image Benjamin Healley, Museum Victoria.

The lump looks small and unassuming. It has a rough texture and is surprisingly heavy for its size. This small pink and grey rock holds an intriguing secret. It is a 150 million year old sauropod dinosaur poo – fossilised and preserved as a record of life in a very different time.

Imagine standing in a lush Jurassic forest in what is present day Utah, USA.
The ground vibrates with thundering footfalls. It is a 25 tonne sauropod coming to feed. Its giant neck and small head reach into the dense vegetation to tear off some leaves. The mouthful of leaves travels down its long neck to its roomy stomach. Fermentation chambers filled with bacteria in its guts help break down the plant fibres and extract the nutrients. A soft lump of poo falls onto a bit of swampy ground, where it is preserved and fossilised – turned into stone. It is buried and remains hidden for 150 million years until someone digs it up. We acquire it for the museum.
Fossilised poo – or ‘coprolites’ – were unveiled at Melbourne Museum today in preparation for installation in the Dinosaur Walk, opening on April 3 at Melbourne Museum. A coprolite will be on open display in the new exhibition, enabling visitors to touch it for themselves.

How do we know it is dinosaur poo? It comes from a rock layer known as the Morrison formation, which is the right age and contains many fossils of Late Jurassic dinosaurs. It is the ‘right’ size and shape. It is similar to other lumps which have been analysed and have been found to have plant remains in them. The process involves looking at thin sections of the rock under a microscope, where traces of plants can be seen. We cannot be 100% sure our lump is fossilised dinosaur poo, but the evidence suggests it is highly likely.

Is it rare? Fossils of dinosaur bones are quite rare, but fossils of soft parts like skin, muscle or traces like poo are even rarer. The conditions to preserve a soft lump are unusual, so coprolites are rare.