An artist’s rendering shows how Ahvaytum bahndooiveche may have appeared in a habitat dating to around 230 million years ago. Credit: Gabriel Ugueto.
It’s not often that a discovery completely changes the accepted narrative of a particular area of study. But that is exactly what happened when a dinosaur find in Wyoming challenged the perceived wisdom that an inhospitable climatic period prevented dinosaurs from migrating to what is now the northern hemisphere.
That find in 2013 led Dr Dave Lovelace on a 12-year odyssey in which he would finally prove that dinosaurs did in fact exist in the northern hemisphere at the same time as those found in the southern hemisphere, in countries such as Argentina and Brazil.
ScienceVega caught up Dr Lovelace to hear the fascinating journey that led to the naming of Ahvaytum bahndooiveche, which is now the oldest known dinosaur to have roamed North America.
ScienceVega: Can you outline the accepted knowledge regarding the emergence of dinosaurs in Gondwana before they spread to Laurasia?
DL: For perhaps 20 to 30 years it has been a longstanding hypothesis that dinosaurs originated in the southern hemisphere. All of the fossils we have of the most primitive-looking or least-derived fossils of dinosaurs were all found in Argentina and Brazil initially, and those were found as early as the 1960s. They have since acted as a placeholder for the earliest dinosaurs.
Researchers didn’t have good age constraints for the rocks in North America, so we thought we had things that are of a parity with the southern hemisphere until around 2003 when we started getting radiometric dates for the rocks in the US where all the Triassic-era dinosaur fossils have been found, which is the modern-day desert southwest portion of the country.
The rocks were dating to around 224 to 225 million years ago and the main point is that all of the dinosaurs were younger than those dates. We had dates for South America from as early as the mid-1990s and that meant there was a temporal gap.
A schematic of the supercontinent Pangea and it’s subsequent break-up to the modern day. Credit: Kious, Jacquelyne; Tilling, Robert I.; Kiger, Martha, Russel, Jane; blanked out by User:Llywelyn2000., Public domain, via Wikimedia Commons.
That led to the hypothesis of what is known as the diachronous rise; that the rise of dinosaurs occurred at two different times in each hemisphere of the globe. It seemed that initially dinosaurs appeared in the southern hemisphere and, for unknown reasons, didn’t appear in the northern hemisphere for around ten million years or more afterwards.
A lot of the hypothesis was driven by what we thought of the climate across the globe at this point. At the dawn of the dinosaurs, about 230 million years ago, we are looking at a world where all the continents were squashed together in the supercontinent of Pangaea. It was basically a C-shaped continent where the equator was roughly straight through the middle of the ‘C’, and in the southern half of that, all the dinosaurs were from mid to high latitudes, 35° paleolatitude, which equates roughly to the central portions of the hemisphere. But there was nothing from 30° in the southern hemisphere up to the equator and nothing from the northern hemisphere at all.
The idea was that there were large belts of aridity that were super dry and super hot in the middle of the continent, and that was the barrier that was preventing dinosaurs that originated in the southern hemisphere from migrating northward.
As paleoclimate models have improved, they have shown there were probably zones of humidity and moisture along the coast, as you might suspect. Unfortunately, those weren’t readily incorporated into the hypothesis of dinosaur origins, and that is where things stood until climate change in what is known as the Carnian pluvial episode, a period of humidity and moisture, from around 234 to 232 million years ago, started to change things.
The Carnian pluvial episode was actually defined by geology in the UK, specifically looking at what they classically called the ‘fissure’-fill deposits, which are really conduit pipes that dissolved during this period because of the high humidity and high precipitation.
This then was the time period, this change in climate, that allowed dinosaurs to migrate, which is where things stood prior to our discovery.
Bone fragments found during the excavations. Credit: David M Lovelace.
ScienceVega: So how does your research challenge that narrative? How has it added to it?
DL: We found a very fragmentary specimen; just the upper portion of the femur and one of the ankle bones, but those two bones are some of the most diagnostic elements of dinosaurs. Sometimes skulls have more information, but in terms of the bones you’re more likely to find, those are probably the two you would wish for.
Ideally, we would have more of the specimen, and we do have another head of a femur and a lower portion of an upper arm bone, and they were diagnostic to a slightly different animal that is either very closely related to dinosaurs, or it’s a really early diverging ornithischian dinosaur. We don’t know which, and we didn’t argue this in our paper, but we’re just saying it is an animal called a silesaur.
Unfortunately, we found all that material fairly close together. It was found on the surface and had weathered out. We were never able to locate exactly where it was weathering from, but we were able to constrain where it could possibly be from, which is why we know where it is in the stratigraphic rock record.
Atreipus track (silesaurid?) from the Jelm Formation. Credit: David M Lovelace.
So now we have a dinosaur in the northern hemisphere and the other fauna in the formation pointed to an older age. We suspected that this was Carnian in age, so somewhere between 237 and 227 million years, which means it would have been the oldest known dinosaur in North America and, therefore, in the northern hemisphere.
However we didn’t know that with any rigorous certainty; we had a lot of qualitative data, but we didn’t have quantitative data. So before we made this claim that we had a really old dinosaur, we had to go through the process of finding out the age.
When we found these specimens, we also found a lot of vertebra, some claw bones, toe bones, a lot of other things, but they could be from either the silesaur or the dinosaur, so we have combined those together as a separate collection because we don’t know which bones belongs to which critter. We have more of the animal, but we don’t know exactly which elements truly belong to the dinosaur.
Regardless they were diagnostic and we thought that they were roughly the same age as some of the older dinosaurs in the world, and that’s what drove us to continue to build the story of the context of where these animals were found. Once we got radiometric ages to actually constrain the rocks above our dinosaur, we knew that our dinosaur had to be older than those ages.
The lowest age we got was about 229 million years and our specimen is well below that. We then used stratigraphic modelling where we have a prediction on what the age is going to be based on how thick the rock is and different age tie points that tell us the rate of deposition, and how fast sediment was collecting in this area over time.
Once we know that rate, we can predict, if a specimen is, for example, five metres down, then it will be this many million years older. That is where we got the age of about 230 million years old. The base of our formation is probably about 231 million years old, and those ages are all very comparable to the 229 million in Argentina and the 230 million age in Brazil, which is where all the oldest dinosaurs known that have really good radiometric dates are.
Now we had some really good constraints to say that our dinosaur is the same age and this basically challenged the hypothesis that there was a big climatic barrier preventing dinosaurs from migrating northward.
It also means dinosaurs are around the same time globally, which means they have a cosmopolitan distribution; they’re kind of everywhere.
It still begs the question, where did dinosaurs originate? But we know that our model of how organisms evolve really seems to have a central focus. It is a centre of origin that they disperse from, but that’s not necessarily how things happen; a population might certainly originate in an area, but if there’s genetic communication all throughout, you can get all sorts of speciation going on globally.
The fact that dinosaurs are all over the globe tells us that either there’s an origin much deeper in time, or the ancestors of these animals were already there and you just have different populations of those animals evolving in a similar trend globally.
Garrett Suprise locality with 2013 UWGM field crew member Garrett Jonshon looking at the outcrop where UWGM 1975 was discovered. Credit: David M Lovelace.
ScienceVega: These fossils were first discovered in 2013. Can you give an overview of the techniques that have been used in the analysis since then to get to where we are today?
DL: The specimens were found in 2013, and they weren’t published until 2025, so that is a pretty decent gap in time.
Why does it take so long to publish an animal that only has a few bones it, when it seems it should be pretty fast? We took the view that we really wanted to define that ecosystem instead of simply saying we had found a dinosaur from the Triassic beds of Wyoming. We knew it was the oldest Wyoming dinosaur because there are no Triassic dinosaurs from Wyoming. We also suspected it was probably Carnian, but that’s just because the animals that we found around it, or had been found historically, were a little bit different than other things found in the desert southwest.
We thought it was older, but we didn’t really have the evidence. Therefore we had to go about doing a lot of stratigraphic work, which means we trench into our outcrops to measure the rocks and to understand what they look like and what the environment was.
We had to build the context, not just of our little area that we’re studying, but of the entire formation and its relationship to the rocks that are really well known in the desert southwest.
In Arizona, New Mexico and Texas there are great outcrops with great fossils with really good radiometric dates and a lot of work had gone into them. With our Wyoming rocks, the Chugwater group, and specifically the Popo Agie formation, are small bands of rock that hadn’t really been studied for half a century. We had a lot of work to do just to set up the story, to talk about the dinosaurs.
In the interim, we found a lot of other specimens that were really important, including a little chunk of the tooth-bearing section of the skull of an animal called a rhynchosaur of which there are a lot and some of the most famous specimens have been found in the UK. Those are important globally because they bind all the rocks of a certain age because they go extinct at about 227 million years ago. If they are there, those rocks have to be older than 227 million years.
And we found two different taxa at the unit about four or five metres below where our dinosaur is, and part of the same formation. Therefore we have another constraint suggesting this is probably Carnian rock. That was important, but we still didn’t have a quantitative date so we did some radio isotopic analysis of zircon crystals, originally created in the magma chamber of volcanoes and erupted as ash that was quickly incorporated into local sediment that was preserved as sandstones.
We got very lucky in the sense that we had three consecutive ages from rocks that were stacked on top of each other. The base layer gave us crystals that were all about 229-million-years-old, the next level had crystals that were both 229- and 228-million-years-old and the next level had 229-, 228- and 227-million-years-old.
We know that as the higher band had crystals of 229, 228 and 227 that they’re recycling some of that sediment around that region and pulling it into that new deposit, but we don’t have 228 and 227 in that lower band which means that these are probably recording actual ages. Those stack dates tell us it was actually a pretty good approximation for the age and it supports all the other evidence that we were finding.
All of this meant we were really confident we had a mid- to late-Carnian dinosaur in the northern hemisphere and that’s when we started going about publishing it.
All of this took place over the course of about five years. We initially started to write the dinosaur paper around 2018-2019 while we were still writing the rhynchosaur paper (published in 2022) and the geology paper (published in 2024) and we had another animal that had been found, which also ties to climate, and that was also published in 2024. That is what really set the stage. All of these things are building this huge context, and without them the dinosaur paper we published wouldn’t be quite as meaningful or quite as impactful. We did a lot of work to establish this with a high degree of certainty. That is why it took 12 years to get from discovery to publication.
A rainbow over the field area in Wyoming, USA. Credit: David M Lovelace.
ScienceVega: At what point after the 2013 discovery did you decide to go about publishing in what seems to have been a very far-sighted and strategic manner?
DL: That’s a very insightful question. When we found it in the field in 2013, we knew we had a dinosaur. It was the characteristics of the femur, although we didn’t know whether it was a sauropod line or theropod line, but we knew it was very early diverging, so somewhere at the base of those two lineages; the saurischians.
I like to tell stories and I think the best stories are the ones that have a lot of different chapters to them that help flesh out the story, so it’s not only about visualising what’s going on, but also putting it into context. That’s important to me, and I realised that we needed to do a lot of work.
In other formations globally, lots of research has already taken place; you find a dinosaur, you know the age of the rocks, what the environment was like and other animals in the area. In this case there wasn’t that information, so we had to establish it.
It took us years to build that story, but it was purposeful. I wanted to take the time to establish all of these tie points before we really talked about the dinosaur because I really wanted to make sure we actually had the support that we needed to overthrow a hypothesis that’s been so well supported for so long.
ScienceVega: Why did you choose to call the dinosaur Ahvaytum bahndooiveche, broadly translated as ‘Long ago dinosaur’ from the language of the Eastern Shoshone Tribe, the local Native American people, rather than the more traditional Latin?
DL: In 2020, a lot of events in the US were starting to change the dialogue in the social context, especially associated with colonialism and how we were working with native groups. I realised that everything we’ve named is in Latin, but there is a bigger history and I realised ‘I’m only doing things this way because it’s the way my academic ancestors did it’, and ‘just because it was the way I was taught to do it, doesn’t mean that it has to be done that way’. So my lab took a couple years to dive into not only the philosophy, but also the importance of why we should be moving away from traditional nomenclatural practices.
We reached out to the tribal nations of the Eastern Shoshone and the Northern Arapahoe, who are in Wyoming, because we were working on their ancestral lands – not on the reservation which is sovereign territory, because we thought it was important to recognise that.
The best part of this story is the last three years because we’ve been working with school groups and interacting with students. It has changed the way we do fieldwork and how we bring stories together. We took 7th grade students, who are learning their Shoshone and Arapahoe languages, out into the field along with their Elders who are looking to preserve their history, culture and their language. This led to a dialogue between the students, the Elders and us researchers, and we shared our perspective of how we, as researchers, are interpreting the rocks and then the Elders shared their stories and how they see the rock and their cultural understandings.
The Elders shared with us ways that would be more respectful for us as researchers to approach problems and to approach the land. Ultimately it was the tribal students who came up with ideas for the names of these animals, all of which have now been published. Ahvaytum bahndooiveche is a Shoshone name chosen by an Elder who was working with the students. The Elders and tribal educators are co-authors on our paper.
Building these relationships takes a long time. You don’t instantly have a great working relationship, and there was a lot of trust to establish and a history of mistrust that we had to overcome, but it was an amazing journey for us as a lab and as individuals.
For me, the most important part was using this dinosaur as a tool to work with the students and to get them excited about science. That’s just my passion.
Dave Lovelace in the lab. Credit: University of Wisconsin-Madison Geology Museum.
ScienceVega: What reaction have you had to this research that fundamentally changes the accepted narrative?
DL: So far, the response from our peers has been astoundingly supportive. We had previously discussed this research at conferences, so it has not come as a complete shock, but all the other data and pulling it all together into a single story I don’t think has been shared in that way before.
I’ve been exceedingly pleased with how little pushback we have had. In fact, a lot of people are very excited because this really opens the field. It asks more questions than answers and for scientists that is like gold. We want more questions to try to go out and investigate. These questions are going to be driving what today’s high school students are going to be solving in their careers. To me, that’s awesome.
Read the original paper here.
