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Prehistoric Japanese Sea Hippo Discovered in a Dusty Museum Cabinet

Usually when you open up dusty old drawers and cabinets the biggest prize you can hope to find is maybe those last few quarters you need to finally do your laundry. It’s pretty rare to open up a cabinet and find a 16 million-year-old thigh bone from a sea hippo. Yet that’s what happened at the University of Tsukuba in Japan.  Researchers were looking through the geological collection room when they happened to open up an “old wooden box” and found a bone with a note attached. It had been sitting in storage for 60 years.  The “sea hippo” is actually part of a group of an iconic animals from Japanese prehistory called Paleoparadoxia which is Greek for “ancient paradox.” Is the paradox how something supposedly so iconic ends up unceremoniously stuffed in a cabinet? Apparently that can happen quite a bit, and in the paper published in Royal Society Open Science, the authors say that this should be a lesson in what else might be hiding in museums and other dusty cabinets.

The femur of this particular sea hippo took quite a journey to end up shoved in a cabinet. Reading the handwritten note, archaeologists tracked down the site where the bone was first excavated. It was pretty easy, considering the note read “the right bank of the Higashi Karasugawa River, Tatenokoshi, Tsuchiyu Onsen Town, Fukushima City.” it was signed by a man named Tadayasu Azuma and dated June 14, 1955.  The research team interviewed locals and found that after the bone was found, it was displayed in the hall of the village as a “dinosaur bone.” It’s weird how something so impressive and mysterious as the dinosaurs has become a catch-all term for anything old. There’s a lot of old bones besides dinosaurs, as this case demonstrates.

Paleoparadoxia, full skeleton.

According to locals, the bone was excavated during the construction of a dam by Tadayasu Azuma. Azuma kept the femur in his house before it was displayed as a “dinosaur bone” in the village hall. At some point, according to the paper, a university professor “took the well preserved bones with him,” which includes our dusty hippo thigh. That’s a pretty vague sentence they gave. Did he steal them? Can I just decide to take some bones with me?

Shortly thereafter, Tsuchiyu Onsen Town was gutted by a devastating fire, but the remaining fossils survived. After the fire, the rest of the smaller fossils were (once again) taken by a high school teacher. It seems like Japan has a real problem with teachers just taking bones with them. These fossils were not recovered.

The Paleoparadoxia, AKA sea hippo,  was an ancient, ocean dwelling mammal that spent its days walking around the sea floor eating plants. At first thought to be an amphibious creature, the seven-foot-long Paleoparadoxia was later found to be a fully aquatic mammal. It lived between 10 and 20 million years ago and ranged all across the Pacific from Japan to Alaska and south in the waters off the coast of Mexico. According to scientists, this newly found bone is the best preserved specimen found yet.

Artists rendition of the sea hippo

Drawing by artist Nobu Tamura of the paradoxical sea hippo.

The authors of the paper say that this is a strong argument for properly identifying specimens and recording secondary characteristics, as there’s a good chance this would never have been discovered if not for chance:

Rediscovery of this specimen tells us about the importance of recording secondary information of museum specimens accurately, especially as it is difficult to know how informative or rare a specimen may turn out to be when examined within a comparative context that allows for their proper identification.

Who knows what else is out there just collecting dust?