‘Dinosaur’ bone reclassified as belonging to an extinct mammal

by Phil Robinson

The bone that was located

A ‘dinosaur’ bone unearthed over 60 years ago has recently be reclassified instead as the right femur of a Paleoparadoxia, an aquatic mammal similar to a hippopotamus. The animal is thought to have been fully aquatic spending most of its time eating plants on the bottom of the sea floor. The fossil was discovered in the 1950’s on one of the Higahi Karasugawa River banks during the construction of a dam close to Tsuchiyu Onsen Town, Japan. It was displayed in the town hall as a ‘dinosaur’ bone until the hall was destroyed in a fire in 1954.

In 2017, the bone, then stored in an old wooden box in the geological collection room at the University of Tsukuba was located by one of the study’s authors and re-examined. The re-examination led to the discovery that the bone instead belonged to Japan’s iconic extinct mammal the Paleoparadoxia.

One of the papers authors, Dr Kimura pointed out that, “We believe that this specimen is a good lesson not only for vertebrate palaeontologists but also for all museum curators and researchers”. A good lesson to be heeded by all! Such historic finds are often used to construct evolutionary histories and ecosystems. However, mistakes around the basic identification of bones can be made for a variety of reasons, never mind the evolutionary spin that is then forced upon them as well.


Paleoparadoxia, an aquatic mammal similar to a hippopotamus

Further reading:

Identified remains in Idaho raise big questions for anthropologists



Japan’s iconic extinct mammal, hertigaedaily.com, 27 July 2018.

Matsui, K., et al., A long-forgotten ‘dinosaur’ bone from a museum cabinet, uncovered to be a Japan’s iconic extinct mammal, Paleoparadoxia (Desmostylia), R. Soc. Open sci. 5:172441, July 2018 | doi:10.1098/rsos.172441.