Amateur fossil hunters have been digging at a spot near Mitchell, Oregon for years. They’ve found plenty of ammonites, and one dinosaur toe bone. A few years ago, the Bureau of Land Management granted a permit to the University of Oregon to try to find dinosaur bones at that site. A team of volunteers from the North American Research Group, a local fossil collecting group, along with an emeritus professor at the University of Oregon, set out to see what they could find. In the end, they didn’t find dinosaur bones. Instead, they found evidence that a lot of large, bird-like cousins of dinosaurs had once spent a time eating and pooping at this spot - it’s likely this was once a home to a nesting colony of pterosaurs. Gregory Carr, who organized the dig, and Gregory Retallack, emeritus professor at UO, join us to talk about what they found.
Note: This transcript was computer generated and edited by a volunteer.
Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. For over seven decades, fossil hunters have been digging in a spot near Mitchell, Oregon. Over the course of that time, they’ve found plenty of ammonites and a small dinosaur bone. A few years ago, the Bureau of Land Management granted a permit to the University of Oregon to try to look for more bones, so a team of volunteers from a local fossil collecting group, along with an emeritus professor at the University of Oregon, set out to see what they could find. In the end, their 2021 dig didn’t turn up dinosaur bones.
Instead, according to a paper published in the journal Lethaia, they uncovered evidence that a lot of large bird-like dinosaur cousins had once spent time eating and pooping at this spot. Their theory is that the site was once home to a nesting colony of pterosaurs. I’m joined now by two of the coauthors of this paper. Greg Carr, a retired engineer, organized the dig. Greg Retallack is a professor emeritus at the University of Oregon. Welcome to Think Out Loud.
Greg Retallack: Hi there.
Greg Carr: Hello.
Miller: Hello. So, Greg Retallack first: the area we’re talking about is near what’s now Mitchell, in Central Oregon. What would that area have been like 100 million years ago?
Retallack: Well, even though we didn’t find the dinosaur bones that we wanted, and let’s still go out and find them, we did get a very good impression of what it was like almost exactly 103 million years ago. We found fossil plants, and we’ve known quite a bit from the sediments and from the debris flow that we are interpreting as the remains of pterosaur guano, that it was very similar to the rocky coast of northern California, including redwoods.
So, if you want to see in your mind’s eye what Oregon was like 103 million years ago, just think about that coast near Arcata in Humboldt County, California, where the coast redwoods are.
Miller: So, is it that the Pacific Ocean as we know it now? Was it just that the water levels were higher? How is it that what is central Oregon now was the coast 103 million years ago?
Retallack: Oh Western Oregon just wasn’t there. [laughter] It’s all a lot younger. Bits of it came in from the ocean, and bits of it moved north. The only really old parts of Oregon are what Thomas Condon in his 1911 book called the two islands, The Klamaths and the Blue Mountains. That was the coast back then.
Miller: Can you explain what you found in that area near Mitchell back in 2014?
Retallack: Oh, yeah, that was very exciting. We found a toe bone, a single toe bone of a dinosaur. Oregon’s first described dinosaur. We published that one in 2018, and then, within a month, another one was reported from Cape Sebastian by Dave Taylor. So, Oregon has two dinosaurs now, but in both cases, it’s very frustrating. We know what general kind of dinosaur it is; the one that they’ve found is a lambeosaur, the one that I found is an ornithopod. But we’d really like to give it a name. We would like a diagnostic piece, like a piece of skull or a tooth or something, so that we could actually name Oregon’s dinosaurs.
Miller: What are the limitations of having just a toe bone? What can you infer from that single bone, and what is just too far away, in terms of what you can fill in?
Retallack: Oh, you can infer a lot. I went on a dinosaur odyssey up to Alaska and down through the great dinosaur museums of Canada and Montana to do comparisons, and from that single toe bone, we know it was big, probably about 1500 lbs in weight, probably about 10 to 12 ft long. It was quite comparable in size to those of big dinosaurs, and it’s actually easy to do now because whole skeletons of dinosaurs are on display throughout the North American West and Canada, just to compare our bone with that. So we know it was big, we know it was an ornithopod from its morphology, so it was a herbivore, but that’s about it. It’s a very interesting time in the evolution of this ornithopod lineage, from the more early types that were found in the early Cretaceous through to the really bizarre late Cretaceous kinds.
Miller: Greg Carr, how did you become interested in archaeological digs? As I noted, you are a retired engineer.
Carr: Yeah, well, I grew up as a rock hound. My dad’s a geologist, so I’ve always been collecting rocks and minerals and crystals and things like that. I really got into fossils almost exclusively about 15 years ago. I joined a very active local fossil club, the North America Research Group; they meet in Tualatin every month. From there, I learned where a lot of the good fossil areas are in Oregon, and I learned how to prep and present fossils, so it’s been a kind of a specialization of the general stuff I was doing before.
Miller: What have you found in the Mitchell area over the years?
Carr: Well, in Mitchell, the flight that we were at has been famous among casual collectors. The people have been collecting ammonites there for about 70 years. We have a part of a jaw of a plesiosaur that came from the same formation about five miles away. We have found ichthyosaur back bones from that same formation, the Hudspeth Trail, and in fact, on this dig, we found a tooth and a backbone from an ichthyosaur as well as the other things that we found there.
Miller: How did that 2021 dig come to be? How did you rope Greg Retallack into making this happen?
Carr: [laughter]
Retallack: Well, I was keen to go. My role was mainly on the technical side, which was getting the permit from the BLM, because it’s BLM land, but the other Greg, he just carried the ball and did a superb effort. We got 82 volunteers out there, and it was quite wonderful actually to see people really turned on to fossils.
Miller: Greg Carr, what was the role of volunteers in this effort?
Carr: Well, yes, we had lots of volunteers. We had a lot of the people from the North America Research Group show up, but we had other people from the area; families that were just vacationing in the area heard about it. We allowed them to come in and dig. We had people from the Rice Rock and Mineral Museum in Hillsboro come out. Basically, you can’t do a dig like this without having a lot of labor. You need people to shovel rock and to sift through things, and to count pieces of ammonite shell to try to figure out how violent the storm was that washed this stuff out.
Besides, people like to go dig in the rocks. This place is rewarding, always has been, for ammonites. Now to find this additional dimension of not only pterosaurs, which we had known were in the area because we have a pterosaur bone from somebody’s backyard in Mitchell from many years ago, but we now have come to the realization that there are scattered dinosaur bones there. We were hoping to find the dinosaur in place, but we didn’t.
Miller: Greg Retallack, can you explain the bits of evidence that you found that gave you the confidence to say that there were a bunch of prehistoric winged reptiles, these pterosaurs, that roosted at the top of what used to be a kind of coastal cliff? What’s the evidence that lets you say that?
Retallack: Well, we had a very distinctive bed. It was about a meter thick and green and strange looking, and it was absolutely full of fragments of ammonites. Ammonites can be quite big, and these certainly were, but all of these shell fragments were about the size of cornflakes. This is characteristic of what we call a durophagous predator: something that is eating something hard and crunching it up into small pieces.
Miller: ‘Durophagous’ meaning an eater of hard things.
Retallack: They’re eating hard things. That’s right. Eating a shelled creature, the ammonite, to get the octopus-like creature from the inside, and really crunching them up like herring gulls do. In fact, the size distribution of the ammonite fragments was exactly like that you get in herring gulls. This pterosaur group is very diverse. It includes creatures that were quite like condors, that were like flamingos, that were like pelicans, that were like bats. Now, we can add that some of these were quite like herring gulls. There’s no other reasonable explanation for that great amount of broken up shell.
The second line of evidence was we analyzed the whole bed for phosphorus, and the phosphorus was off the charts. This is the sort of indication that we took that we had some sort of a guano deposit. Guano, of course, is mined in many Pacific Islands and other places, Chile for example, for phosphate fertilizer. These two lines of evidence led us to believe that what we were dealing with was a sort of a landslide, a debris flow, of guano and shell fragments down into the shallow ocean where the ammonites actually lived. We also found a couple of bits of bone that we think might be pterosaur, although not particularly diagnostic either.
Miller: How big a colony might we be talking about?
Retallack: Well, a meter thick landslide of high phosphate and shell debris, that’s a pretty significant colony. I would say that would be a colony on a par with the sorts of phosphate deposits we find, for example, in Peru and Chile on the coast there. In a very productive area of moon upwelling, we have colonies of gulls, herring gulls and puffins and other seabirds, on Oregon sea stacks, but nothing that would produce a bed of that thickness.
Miller: I saw a quote from you in an article about your paper and about this dig where you essentially said that this was an ‘unsuccessful dig’ from the perspective of finding more bones to add to the skeleton, to add to the toe bone, that you had previously found. How do you figure it out for yourself, what is a successful dig and what’s unsuccessful?
Retallack: Well, the stated objective of the dig was to find something diagnostic so I could put a name on the Oregon dinosaurs. It was unsuccessful from that point of view. And now, I get the feeling it’s actually doubly unsuccessful; it turns out that we didn’t find the dinosaur bone piece that we wanted. Well, we’ll still keep looking. But one of our reviewers, a pterosaur expert, suggested to us that the pterosaur we’ve always known from Central Oregon might not be the one that actually chomped up the bone. That might be another group; there could be two Oregon pterosaurs. So there could be another pterosaur out there which we need to find now as well.
It goes on and on. This is what I really love about science. Even though I’m 71 years old, I’m still finding new things.
Miller: Maybe the issue is the incompleteness of the word ‘success’ or ‘not success’, because what you and this team, including Greg Carr and these volunteers, have uncovered, it may bring up plenty of questions, but also deepens our understanding of what the world was like 103 million years ago. That’s not nothing, right?
Retallack: No, no, no, no, no. It was a great study, and it really worked out well, particularly because we’ve always suspected, and it was actually reconstructed in the aviary in Jurassic Park movie three, remember, that they were in these kind of coastal aviaries. We just never had any evidence for it before. I think that was one of the reasons why it was so well accepted.
Carr: I wouldn’t say it was unsuccessful.
Miller: Greg Carr, what were you saying?
Carr: I was gonna say, from my standpoint, it was a quite successful dig. We did actually find some broken pieces of dinosaur bone. We found one entire bone, but it was again another toe bone, so it doesn’t help us figure out what kind of dinosaur bone. We found an ichthyosaur bone. We had lots of people, and I organized field trips for our fossil club, and people enjoyed it. Nobody got hurt. Nobody got affected by the heat; the last weekend of the dig was that weekend thay we hit 115 degrees, and yet nobody suffered from that. So in my mind, it actually was a very successful dig.
Miller: Greg Carr, do you have plans, along with our other Greg, to go back and to find another 10x4 meter rectangle and dig again?
Carr: We don’t have any plans for a permitted dig. The US laws are kind of strange; if you’re just a casual collector, you can go out to these places and dig for ammonites and other invertebrates, plant materials. What you can’t do is you can’t collect bones. If we say yes, there are plans for us to take our fossil club back out there and dig for more ammonites. If we find bones though, we have to leave them there, carefully mark them, document them, contact the folks at the University of Oregon, and get a permit to collect the bones. So, yes, we’re going back there, but not for bones, just for invertebrates.
Miller: Greg Retallack, what question are you most excited to answer now, in your emeritus professor life? And we have just about 45 seconds left.
Retallack: Oh, I’ve wandered off into all sorts of other things. This was just a lovely piece of serendipity. I’ve been working primarily on the origin of life in soils, on the nature of soil formation on Mars, on really early phases in soil history, which is my specialty. This was a deviation, and quite a delightful one. Although the dig was unsuccessful in terms of its stated aims, it was really a blast, and Mitchell now has a brew pub and a bakery. It’s quite the going town now.
Miller: Greg Retallack and Greg Carr, thanks so much for joining us.
Carr: Thank you.
Retallack: Yeah, thanks.
Miller: Greg Retallack is professor emeritus in earth science at University of Oregon. Greg Carr is a retired engineer.
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