Idaho dinosaurs saved from being road gravel.

I was nervous to hear that what I suspected to be a significant fossil site in the Wayan Formation had been recently deemed to be a prime location to harvest rock for road gravel. Thankfully (and I am quite grateful for this) the land administrator, Caribou-Targhee National Forest was very receptive to the concerns myself and a retired paleo friend voiced about this. Caribou-Targhee allowed volunteer paleontological monitoring of the construction and salvage of fossils discovered. The workers at the site were even kind enough to spread out a large sample of rock for us and wash it off with water trucks, and they are saving what rock they can for us for a significant time to allow us to collect more matrix samples for processing.

The outcrop after the fossiliferous rock lens was removed.

This site has easily turned out to be the most significant multi-taxic site known for the Wayan, with most Wayan sites being isolated occurrences of Oryctodromeus or Macroelongatoolithus. While not on-par in fossil abundance with what would typically be called bonebeds in the better exposed Cretaceous formations of North America, this site is as close we've seen for Idaho. Fossils I've seen and collected at this site so far consist of isolated or articulated bones (a few articulated caudal vertebrae of various individuals) and teeth. I have found additional bones and teeth just by noisily hammering apart (probably to the annoyment of the neighbors) random matrix blocks I have collected. So far from this site we have recognized fossils from the following animals (preparation this fall will allow better identifications):

• Oryctodromeus (big surprise)
• Ankylosaurs
• Large ornithopod
• Medium-sized theropod
• Dromaeosaurs
• Macroelongatoolithus eggshell
• Probable new cool and unsuspected dinosaur type (I need to see the specimen to verify)!
• Crocodylians
• Turtles
• Mammals
• Fish
• Lots of mystery partial bones that need prepared

Medium sized theropod vertebra. Fossil recovered from lands administered by Caribou-Targhee National Forest.

Small dinosaur metatarsal(?) end. Fossil recovered from lands administered by Caribou-Targhee National Forest.

Oryctodromeus caudal vertebra in cross-section. Fossil recovered from lands administered by Caribou-Targhee National Forest

It's no big surprise to see that these types of animals were there, but considering how rare they usually are in the Wayan, it's great to have this additional physical evidence.

The matrix the fossils occur in consists of an impure sandstone full of chert pebbles and mud clasts torn from the channel margins or proximal floodplain during a high energy flood. Some of the mud clasts are angular and large, indicating they didn't travel far from their origin. The deposit represents either the bottom of a river channel where bones and teeth accumulated over time (a channel lag deposit) or what's termed a crevasse-splay, where a levee burst during a high water flood event and buried bones and teeth accumulated on the adjacent floodplain.

Matrix block from the fossil locality. Note the very large and elongate green mudstone clast below the hammer.

I've been disappointed in not being able to do nearly as much fieldwork this summer as I had hoped. However, this locality has produced more fossils from non-Oryctodromeus forms than I typically find in years of prospecting. Our work at this site is not at all done yet, the Forest Service has agreed to leave some matrix blocks accessible for me for the foreseeable future, and I hope to gather as many of them as I can, and they should certainly yield more important specimens.