Whales in the mountains

I work for a public museum (VMNH is a Virginia state agency), so part of my job is answering questions from the public about paleontology. This usually takes the form of identifying “fossils” that people have found in a local stream or some other unlikely place. About 90% of the time they’re mistaken, and I’m left with the unenviable task of telling someone that their prized fossil is, in fact, a rock. But every now and then I get something different.

Last week Francis Deboever sent me a series of photos of a supposed fossil; the verdict from some online forums was that it was a whale rib. This one really is a bone, and it’s from a whale, but it’s not a rib. This is a segment of a dentary (lower jaw) from a baleen whale. Several mental foramina, which are typical of whale dentaries, are visible along the dorsal margin, as indicated by the arrows below:

In cross-section, the mandibular canal is visible, filled with sediment that includes fragments of seashells:

While most parts of baleen whale skulls are somewhat fragile, dentaries are actually rather tough. Fragments show up frequently along the rivers on the Virginia Coastal Plain, usually having weathered out of either the Calvert, Eastover, or Yorktown Formations. So Francis has a nice, but rather common, baleen whale lower whale jaw. What, then, makes this bone special? This bone was found in Harriston, Virginia:

Harriston is located in the mountains, more than 80 miles from the nearest coastal plain sediments! How did this whale manage to make its way to the Blue Ridge? The probable answer is actually included in Francis’ email:

“[It] appears to have washed out from under an old concrete slab that I believe covers the debris from an old concrete well.”

The Miocene and Pliocene deposits along the James River used to be quarried fairly extensively. These are soft sediments that are extremely rich in mollusk shells, and they were mined for a variety of purposes, including fertilizer, fill dirt, and making concrete. It’s very likely that the well was constructed from concrete made from a load of Eastover or Yorktown sediment transported in from a quarry near the James River, and that happened to include a whale jaw fragment among the sediment.

Thanks to Francis for bringing this specimen to our attention, and for giving me permission to post the photos on the blog.

Advertisements
This entry was posted in Chesapeake Group. Bookmark the permalink.

2 Responses to Whales in the mountains

  1. boesse says:

    I saw this on the forum as well – I’m pretty surprised how large the mandibular foramen is that far anterior – in the second photo, which shows the anterior end – it’s still really huge, and that’s at least 1/3 to 1/2 of the way down from the posterior end. In Herpetocetus, the enlarged canal is more attenuated, and appears to ‘pinch down’ not too far anterior of the coronoid process and coronoid crest.

    This specimen is a little more like Uranocetus in this regard – however, I don’t know what the mandibular canals of the Maryland cetotheres s.l. are like (or the term Erich Fitzgerald recently coined – “Kelloggitheres”)

  2. Alton Dooley says:

    Keep in mind, this could be from a balaenid. That might place it a little further back. Just speculating; I haven’t actually compared it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s