Oryctodromeus exhibit at the Museum of the Rockies

After roughly a year of work the exhibit on Oryctodromeus, and aspects of the fauna and flora of the Wayan Formation of Idaho and Vaughn member of the Blackleaf Formation, is on public display at the Museum of the Rockies in Bozeman. Since my research includes providing a thorough osteological description of Oryctodromeus, I was asked to choose all the bones that were cast and molded for the skeletal mount, and to help make sure that the skeletal mount represented our best knowledge of the animal. Having worked on the animal for about a decade (collecting a lot of specimens before the species was described and describing the osteology of Idaho specimens in my Masters thesis), it is awesome to finally see a skeletal mount of the animal, and an exhibit describing some of the fauna and flora of the Wayan and Vaughn! I also love how the work of everyone involved in researching the Wayan and Blackleaf (Jamie Fearon, Steve Robison, Jade Simon, Cary Woodruff ) is described. Here I don't want to give away the whole exhibit, but I would like to share the Oryctodromeus mounts.

I love the Lull Mount that Matt Smith of Livingston did. A Lull Mount is a mount were one side is skeletal and the other side is fleshed out. Of course we have no idea about what integument Oryctodromeus had but I like the scheme used here. One of the things that took some people by surprise as the skeleton took shape is the length of the tail in Oryctodromeus. The tail on this mount is over seven feet long, roughly two-thirds of the whole length of the animal, a condition similar in Tenontosaurus. I based the length of the tail on a Wayan Formation specimen which represents (as far as I can tell) one individual, this specimen has 57 caudal vertebrae. I measured the length of each caudal and just used that to give a minimum length for a tail. Interestingly, the tail vertebrae of Oryctodromeus very quickly loose their long processes and the tail becomes thin and whip-like.
Another interesting aspect of the tail not indicated on the mount is the extreme abundance of ossified tendons found in many of the specimens. In these specimens the ossified tendons begin near the base of the neck and occur on the tops of the transverse processes of the vertebrae, and the tail vertebrae are entirely encased in a thick lattice of tendons (see Krumenacker, 2010). This could definitely complicate getting around in a burrow if these tendons were as stiffening as believed. But we have ideas that may help solve this problem...

Of course one of the most important aspects of Oryctodromeus, is it's burrowing behavior. As described originally (Varricchio et al., 2007), the bones of an adult and two juveniles were found in a fossilized burrow. Matt Smith did a great job again creating a replica of the burrow with two kiddos and the adult in the burrow. The original description also discusses smaller burrows that extend off the main body of the Oryctodromeus burrow, these could possibly belong to a small mammal (look carefully at the burrow in the exhibit).

As I said, I don't want to give away everything about the new exhibit, so I'll leave off there.

A few useful references as discussed above:

Krumenacker, L.J., 2010. Chronostratigraphy and paleontology of the mid-Cretaceous Wayan Formation of eastern Idaho, with a description of the first Oryctodromeus specimens from Idaho. BYU Provo MS.

Varricchio, D. J., A. J. Martin, and Y. Katsura. 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society B: Biological Sciences 274: 1361–1368.

Faunal update

I've heard in regard to blogging that "Never has so much been written by so many that will be read by so few", and seeing as it's not dissertation or family related it has been a while since I updated this blog. However, I've given a few talks at conferences the past month detailing new Wayan/Idaho Cretaceous discoveries, so it's a good time to share this new information here.

My talks this spring were at the Mid-Mesozoic conference in Utah and Colorado (http://www.utahpaleo.org/mid-mesozoic-conference.html), and the regional GSA meetings here in Bozman (https://gsa.confex.com/gsa/2014RM/webprogram/Paper238289.html). The former talk outlined Wayan fauna and taphonomy, and the latter the fauna and taphonomy of the bonebed found last year that I have termed the Robison Bonebed, after my friend and mentor Steve Robison. Between the Robison bonebed, another site yet to be discussed, and other Wayan localities we are just starting to finally get real diversity (albeit very fragmentary fossils) for the Wayan fauna. So here is an updated listing of all the critters we now know about:

• Oryctodromeus: A small burrowing ornithopod. This animal heavily dominates the Wayan fossil assemblage, >12 partial to near complete skeletons and lots of isolated bits and pieces.
• Hadrosaur: Known from a tooth from the Robison Bonebed. These large ornithopods were fairly new arrivals on the Cretaceous scene at this time and would be dominant in later Late Cretaceous faunas.
• Iguanodont: Known from a few isolated teeth and bones from various localities.
• Nodosaurs: Known from isolated teeth, a partial skeleton currently under research, and arguably common scutes, teeth, and vertebrae from the Robison Bonebed.
• Giant oviraptorosaur: Represented by very common isolated eggshell, eggshell concentrations, and rare large eggs.
• Tyrannosaurid: Known from isolated teeth. These are small animals that have not yet achieved the giant size that tyrannosaurs would gain in the later Late Cretaceous.
• Cf. Neovenatorid allosauroid: This animal is represented by a small vertebra from a young animal.
• Dromaeosaurs: Known from rare teeth from various localities.
• Coelurosaurs/indeterminate small theropod(s): Known from teeth and bones from a few localities. I'm hoping to get better identifications on these and more material.
• Large, maybe Allosaurus-sized, possible fish-eating theropod: This animal is known from teeth from the Robison Bonebed. The teeth are distinctive and I can't seem to find anything that matches them.
• Triconodontid mammals: Known from isolated teeth from two localites.
• Non-cimolodontan multituberculate mammal: Known from a jaw with teeth found at the Robison Bonebed.
• Cimolodontan mammal: Known from teeth from one site.
• Eutriconodontid mammal: Known from teeth from one site.
• Metatherian mammal: Known from teeth from one site.
• Indeterminate mammals: Known from teeth from the Robison Bonebed.
• Deinosuchus-like/Large goniopholid crocodylian: Partial skull currently under research.
• Small crocodylians: Known from teeth from a number of sites.
• Turtles: Fairly common shell fragments from a number of sites.
• Semionotid fish: Known from hundreds of large crushing teeth and a few scales from a few sites. The size of one scale indicates maybe close to a meter in length at least for some of these fish.

And here's a figure that generally summarizes the fauna of the Wayan, made in this case to represent the fauna from the bonebed.

Once work is completed on these sites and specimens a number of publications will come out on all these bits and pieces. Hopefully in the interim we can find some more complete material of all these animals.

A few useful references:

Dorr, J.A. 1985. Newfound Early Cretaceous Dinosaurs and Other Fossils in Southeastern Idaho and Westernmost Wyoming, Contributions from the Museum of Paleontology, University of Michigan 27(3):73- 85.  Link: http://deepblue.lib.umich.edu/bitstream/handle/2027.42/48524/ID377.pdf

Krumenacker, L. J.; 2010. Chronostratigraphy and paleontology of the mid-Cretaceous Wayan Formation   of eastern Idaho, with a description of the first Oryctodromeus specimens from Idaho (MS), Brigham Young University. Link: http://contentdm.lib.byu.edu/cdm/ref/collection/ETD/id/2317

 

Simon, J. D., D. J. Varricchio, F. D. Jackson, and S. R. Robison, 2012. Giant theropod eggs from the Albian-Cenomanian Wayan Formation of Idaho: Taxonomic, paleogeographic, and reproductive implications. Journal of Vertebrate Paleontology 32 (3, supplement):174.

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.

Introductions to the Wayan and Vaughn: An apparent Oryctodromeus paradise

Does the world need another paleontology blog? Probably not, but here it is (you're welcome). Here the focus will be on general Mesozoic paleontology with some focus on work I am doing in the Cretaceous of Idaho and Montana, as well as reports on occasional paleontological outings and whatever else garners my interest. On that note, lets jump to an introduction of the work I will be doing as a PhD student, work in the mid-Cretaceous. of Idaho and Montana.

Since my time as an undergraduate, I have been involved in working in the Cretaceous formations of eastern Idaho, with most work being in the mid-Cretaceous (latest Albian-Cenomanian) Wayan Formation. Persistence in annually prospecting for outcrops (which are few and far-between) and fossils is slowly allowing a better understanding of the mid-Cretaceous Wayan fauna. The fossil assemblage (Krumenacker, 2010) is dominated by partial skeletons of the small burrowing ornithopod Oryctodromeus, but includes fragmentary remains that indicate the presence of nodosaurs, iguanodonts, large theropods, dromaeosaurs, possible neoceratopsians, turtles, and various crocodylians (including a large Deinosuchus-like form that is currently undergoing description). Eggshell and large eggs of the oogenus Macroelongatoolithus are also known (Simon et al., 2012), with isolated eggshell being fairly common; the presence of this form suggests the presence of a large oviraptorid (hence the silly title banner). Some recent ongoing work by my PhD advisor Dr. Dave Varricchio, others, and myself  is demonstrating the presence of a diverse microvertebrate fauna. Also, if we are really lucky, it sounds as if we may have a new type of unexpected dino to add to the Wayan fauna, once I can see the fossil for myself...

A rare good outcrop of the Wayan Formation.

In southwest Montana, there is a rock formation with numerous Oryctodromeus fossils as well, in fact, it was first described from these rocks (Varricchio et al., 2007), the Vaughn Member of the Blackleaf Formation. The dominance of Oryctodromeus in both the Wayan and Vaughn, and their equivalent Cenomanian ages, suggest that both of these formations represent the same depositional system, the deposits of which have been disrupted by more recent volcanism and tectonic activity. Regional thickness differences in both rock units reflect subsidence rates, while lithological variations reflect, partially, the volcanic input from volcanism associated with the Idaho batholith, to the west.

Vaughn Member near Lima, Montana.

I'm interested to know why a small ornithopod, a dinosaur type typically rare in dinosaurian faunas, is the most common vertebrate in both rock units, while those dinosaurs that are usually most common in other Early to mid-Cretaceous faunas (nodosaurs, large ornithopods, sauropods, theropods) are so poorly represented. I have some suspicions, but they will be hard to prove.

To help address these questions, we plan to do a taphonomic study looking at patterns in fossil preservation and types of fossils found in both rock units, and how these may relate to subsidence rates, depositional environments, and proximity to the Cretaceous Interior Seaway. This may not directly answer my questions, but it will give a better idea of preservational constraints in the area at the time. Of course all this depends on availability of funding, which in paleo and science generally, is hard to come by. If funding is not as forthcoming, my doctoral work will be more Orycto-centric and focus on histology, phylogeny, and morphology. There are plenty of questions in these areas to answer about this wonderful little dinosaur.

There you are, you rare mid-Cretaceous lovers, more rare ornithopod enthusiasts, and unlucky fellows who stumbled across this by accident. More on this and other things later....

Useful references:

Krumenacker, L. J., 2010. Chronostratigraphy and paleontology of the mid-Cretaceous Wayan Formation of eastern Idaho, with a description of the first Oryctodromeus specimens from Idaho. BYU Provo MS.

Simon, J. D., D. J. Varricchio, F. D. Jackson, and S. R. Robison, 2012. Giant theropod eggs from the Albian- Cenomanian Wayan Formation of Idaho: Taxonomic, paleogeographic, and reproductive implications. Journal of Vertebrate Paleontology 32 (3, supplement):174.

 

Varricchio, D. J., A. J. Martin, and Y. Katsura. 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society B: Biological Sciences 274: 1361–1368.