A University of Wisconsin Geology Museum field crew is seen here in 2016 prospecting for additional material at the site in Wyoming where fossils of Ahvaytum bahndooiveche were discovered in 2013. The researchers are Aaron Kufner (left) and Jennifer Lien.
Photo by David M. Lovelace.
The thing about science that distinguishes it from religion is the willingness to change its collective mind when the facts change. This is because science is led by the fact wherever they lead
Science is reasonable uncertainty religion is unreasonable certainty. Religion appeals to those who value certainty over truth, whereas science appeals to those who value truth above certainty.
And scientists have just changed their collective minds about where and when the first dinosaurs appeared.
The consensus had been that they first appeared on the southern end of the supercontinent Pangea before it split into Gondwana in the South and Laurasia in the north and only spread to Laurasia millions of years later.
What can you tell me about the ancient reptile, Ahvaytum bahndooiveche, and its place in the evolution of dinosaurs? Ahvaytum bahndooiveche is a recently identified dinosaur species from the Late Triassic period, approximately 230 million years ago, discovered in what is now Wyoming, USA. This species is notable for being the oldest known dinosaur from the ancient northern supercontinent Laurasia, challenging previous beliefs that dinosaurs originated solely in the southern supercontinent Gondwana.However, that consensus has now been challenged by the discovery of reptile remains in North America (The western part of Laurasia after the Atlantic opened up).
Discovery and Naming
The fossil remains of Ahvaytum bahndooiveche were uncovered in 2013 at the Garrett's Surprise locality within the Popo Agie Formation in Wyoming. The genus name "Ahvaytum" translates to "long ago," and the species name "bahndooiveche" means "water's young handsome man," a term used by the Eastern Shoshone to refer to both dinosaurs and colorful native salamanders. This naming honors the Eastern Shoshone Tribe, whose ancestral lands include the discovery site, and reflects a collaborative effort between researchers and Indigenous communities.
Physical Description
Ahvaytum bahndooiveche was a small dinosaur, estimated to be about 3 feet (0.91 meters) in length and 1 foot (0.30 meters) in height, comparable in size to a modern chicken but with a notably long tail. The fossil material includes fragmentary hindlimb bones, such as an isolated left astragalus and a partial left femur, suggesting it had progressed beyond the juvenile stage and was still slowly growing.
Evolutionary Significance
This discovery has significant implications for our understanding of dinosaur evolution. Prior to this find, it was believed that dinosaurs originated in Gondwana and later dispersed to Laurasia. The existence of Ahvaytum bahndooiveche in Laurasia during the same period as the earliest known southern dinosaurs indicates that dinosaurs were more widely distributed across the globe earlier than previously thought. This challenges the hypothesis of a delayed dinosaurian dispersal out of high-latitude Gondwana and suggests a more complex scenario for the early evolution and distribution of dinosaurs.
In summary, Ahvaytum bahndooiveche provides valuable insights into the early stages of dinosaur evolution, highlighting a broader and more rapid dispersal of these creatures across ancient Earth than was previously understood.
Dinosaurs roamed the northern hemisphere millions of years earlier than previously thought, according to new analysis of the oldest North American fossils
How and when did dinosaurs first emerge and spread across the planet more than 200 million years ago? That question has for decades been a source of debate among paleontologists faced with fragmented fossil records. The mainstream view has held that the reptiles emerged on the southern portion of the ancient supercontinent Pangea called Gondwana millions of years before spreading to the northern half named Laurasia.
But now, a newly described dinosaur whose fossils were uncovered by University of Wisconsin–Madison paleontologists is challenging that narrative, with evidence that the reptiles were present in the northern hemisphere millions of years earlier than previously known.
The UW–Madison team has been analyzing the fossil remains since they were first discovered in 2013 in present-day Wyoming, an area that was near the equator on Laurasia. The creature, named Ahvaytum bahndooiveche, is now the oldest known Laurasian dinosaur, and with fossils estimated to be around 230 million years old, it’s comparable in age to the earliest known Gondwanan dinosaurs.
UW–Madison scientists and their research partners detail their discovery Jan. 8, 2025, in the Zoological Journal of the Linnean Society.
We have, with these fossils, the oldest equatorial dinosaur in the world — it’s also North America’s oldest dinosaur.
Dr. David M. Lovelace, co-lead author.
Department of Geoscience
University of Wisconsin-Madison, Madison, WI, USA.
Discovered in a layer of rock known as the Popo Agie Formation, it took years of careful work by Lovelace and his colleagues to analyze the fossils, establish them as a new dinosaur species and determine their estimated age.
While the team doesn’t have a complete specimen — that’s an exceedingly rare occurrence for early dinosaurs — they did find enough fossils, particularly parts of the species’ legs, to positively identify Ahvaytum bahndooiveche as a dinosaur, and likely as a very early sauropod relative. Sauropods were a group of herbivorous dinosaurs that included some famously gigantic species like those in the aptly named group of titanosaurs. The distantly related Ahvaytum bahndooiveche lived millions of years earlier and was smaller — much smaller.
It was basically the size of a chicken but with a really long tail. We think of dinosaurs as these giant behemoths, but they didn’t start out that way.
Dr. David M. Lovelace.
Indeed, the type specimen of Ahvaytum bahndooiveche, which was full-grown but could have been slightly bigger at its maximum age, stood a little over one foot tall and was around three feet long from head to tail. Although scientists haven’t found its skull material, which could help illuminate what it ate, other closely related early sauropod-line dinosaurs were eating meat and would likely have been omnivorous.
The researchers found the few known bones of Ahvaytum in a layer of rock just a little bit above those of a newly described amphibian that they also discovered. The evidence suggests that Ahvaytum bahndooiveche lived in Laurasia during or soon after a period of immense climatic change known as the Carnian pluvial episode that has previously been connected to an early period of diversification of dinosaur species.
The climate during that period, lasting from about 234 to 232 million years ago, was much wetter than it had been previously, transforming large, hot stretches of desert into more hospitable habitats for early dinosaurs.
Lovelace and his colleagues performed high-precision radioisotopic dating of rocks in the formation that held Ahvaytum’s fossils, which revealed that the dinosaur was present in the northern hemisphere around 230 million years ago. The researchers also found an early dinosaur-like track in slightly older rocks, demonstrating that dinosaurs or their cousins were already in the region a few million years prior to Ahvaytum.
We’re kind of filling in some of this story, and we’re showing that the ideas that we’ve held for so long — ideas that were supported by the fragmented evidence that we had — weren’t quite right. We now have this piece of evidence that shows dinosaurs were here in the northern hemisphere much earlier than we thought.
Dr. David M. Lovelace.
While the scientific team is confident they’ve discovered North America’s oldest dinosaur, it’s also the first dinosaur species to be named in the language of the Eastern Shoshone Tribe, whose ancestral lands include the site where the fossils were found. Eastern Shoshone tribal elders and middle school students were integral to the naming process. Ahvaytum bahndooiveche broadly translates to “long ago dinosaur” in the Shoshone language.
Several tribal members also partnered with Lovelace and his UW–Madison colleagues as the researchers sought to evolve their field practices and better respect the land by incorporating the knowledge and perspectives of the Indigenous peoples into their work.
The continuous relationship developed between Dr. Lovelace, his team, our school district, and our community is one of the most important outcomes of the discovery and naming of Ahvaytum bahndooiveche.
Amanda LeClair-Diaz, co-author.
Fort Washakie Schools
Fremont County School District #21, Fort Washakie, WY, USA.
LeClair-Diaz is the Indian education coordinator at Fort Washakie school and coordinated the naming process with students and tribal elders — a process that started under her predecessor, Lynette St. Clair.
Typically, the research process in communities, especially Indigenous communities, has been one sided, with the researchers fully benefiting from studies. The work we have done with Dr. Lovelace breaks this cycle and creates an opportunity for reciprocity in the research process.
Amanda LeClair-Diaz.
AbstractCreationists traditionally gleefully trumpet occasions where science has got the date wrong, but this is such a case. It's a case of new information pushing the earliest date even further back than creationists would like it to be. Instead of the earliest dinosaurs appearing in the fossil record 230 million years ago in Gondwana, they were present 230 million years before 'Creation Week' in Laurentia in what was later to become North America.
The origin of Dinosauria is thought to be deeply rooted in the high-latitude southern hemisphere (Gondwana). Nearly 6–10 million years separates Gondwanan faunas and the oldest known dinosaur occurrence in the northern hemisphere (Laurasia). However, our understanding of dinosaur origins is biased by an apparent absence of Carnian-aged (237–227 Mya) Laurasian terrestrial strata. Here we report on UWGM 1975/UWGM 7549, the oldest known Laurasian dinosaur Ahvaytum bahndooiveche gen. et sp. nov., and UWGM 7407/UWGM 7550, a silesaurid, from palaeoequatorial deposits of the lower Popo Agie Formation, Wyoming, USA. High-precision radioisotopic detrital ages [e.g. ≤229.04 ± 0.24 Mya (2σ)] from the upper Popo Agie Formation constrain an age-depth model that predicts a ~230 Mya age for UWGM 1975, making Laurasia’s first unequivocal Carnian-aged sauropodomorph dinosaur comparable in age to the oldest dinosaur faunas of Gondwana. The presence of a ~230 Mya, low-latitude, early sauropodomorph from the northern hemisphere, along with a silesaurid, challenges the hypothesis of a delayed dinosaurian dispersal out of high-latitude Gondwana. These data fill a critical gap in the early record of sauropodomorph dinosaur evolution and demonstrate widespread geographic distribution by the mid-late Carnian.
INTRODUCTION
The Carnian Epoch of the Late Triassic (237–227 Mya) (Cohen et al. 2013) heralded the proliferation of early dinosaurs and their closest relatives (Jones et al. 2013.1, Langer et al. 2018, Lee et al. 2018.1). At the same time, several prominent Early–Middle Triassic clades (e.g. rhynchosaurs, dicynodonts, and stereospondyl amphibians) underwent a significant reduction in taxonomic diversity or became extinct altogether by the earliest Norian (Dal Corso et al. 2020). For more than 50 years, the lack of Carnian dinosaurs from the northern hemisphere (Laurasia) has sharply contrasted with the prevalence of the world’s oldest dinosaurs in the southern hemisphere (Gondwana) (Langer et al. 2010, Lee et al. 2018.1, Kent and Clemmensen 2021, Novas et al. 2021.1, Griffin et al. 2022). Currently, the oldest known North American dinosaur, Lepidus praecisio Nesbitt and Ezcurra, 2015, is found in the lower Dockum Group near the classic Otis Chalk quarries of west Texas, USA, with an age no younger than the base of the Adamanian holochron (c. 221 Mya) but without older temporal constraints (Nesbitt and Ezcurra 2015, Martz and Parker 2017).
Globally, biostratigraphic models and detrital zircon ages constrain the oldest dinosaurs to the mid–late Carnian (Hyperodapedon Assemblage Zone) of the Candelária Sequence in Brazil (c. 233 Mya) (Langer et al. 2018, Schultz et al. 2020.1), lower Ischigualasto Formation, Argentina (c. 230 Mya) (Desojo et al. 2020.2), Pebbly Arkose Formation, Zimbabwe (Griffin et al. 2022), and the lower Maleri Formation (Langer et al. 2010, Kammerer et al. 2016), India. The lack of Carnian-aged Laurasian dinosaurs has been hypothesized to reflect inhospitable environmental barriers (Dunne et al. 2021.2, Kent and Clemmensen 2021, Griffin et al. 2022) that isolated high-latitude faunas until conditions improved during the Carnian Pluvial Episode (CPE), which is linked with a global increase in humidity lasting ~2 Myr (c. 234–232 Mya) (Simms and Ruffell 1989, Dal Corso et al. 2020, Simms and Drost 2024). Despite increased sampling and improved high-resolution radioisotopic dating techniques refining our understanding of the spatiotemporal distribution of the earliest dinosaurs and their kin (Irmis et al. 2011, Langer et al. 2018, Philipp et al. 2018.2, Desojo et al. 2020.2, Rasmussen et al. 2020.3, Lovelace et al. 2024.1), there continues to be an apparent dearth of northern hemisphere Carnian-aged dinosaur body-fossils.
As such, the diachronous rise hypothesis, which suggests dinosaur origins as a Gondwanan phenomenon (Irmis et al. 2011, Lee et al. 2018.1, Kent and Clemmensen 2021, Griffin et al. 2022), has largely relied on an absence of body-fossils in the northern hemisphere. Alternatively, the apparent absence of Carnian-aged dinosaurs in Laurasia can be explained by a paucity of well-studied time-equivalent terrestrial strata, most of which lack radioisotopic age control (Lovelace et al. 2024.1). Only a few Laurasian units have yielded faunal assemblages similar to those from chronostratigraphically similar Gondwanan strata (Fig. 1) (Benton and Walker 2010.1, Milroy et al. 2019, Zeh et al. 2021.3, Lovelace et al. 2024.1, Tourani et al. 2023, Simms and Drost 2024). The distribution of Carnian traces (e.g. UWGM 7435) across Laurasia attributed to dinosauromorphs (including dinosaurs) further support the sampling bias explanation. These traces demonstrate the presence of Dinosauria well before the first temporally constrained northern hemisphere dinosaur body-fossils (Bernardi et al. 2018.3). However, these data should not be over extrapolated beyond simply indicating the presence of this clade where traces are known.
Here we report the first dinosauromorphs, including a new sauropodomorph dinosaur and an indeterminate silesaurid along with high-resolution radioisotopic detrital ages from the Late Triassic (Carnian) Popo Agie Formation of Wyoming, USA. Although often fragmentary, the lower Popo Agie fossil assemblage (Fig. 1C) is known to include metoposaurids (Kufner et al. 2023.1), hyperodapedontine rhynchosaurs (Fitch et al. 2023.2), and loricatans (Dawley et al. 1979, Nesbitt et al. 2020.4b). Our findings of a novel species of sauropodomorph dinosaur from mid–late Carnian deposits in the northern hemisphere demonstrate the unambiguous presence of dinosaurs at low latitudes in strata chronostratigraphically equivalent to the oldest Gondwanan dinosaur faunas. Vertebrate remains are still considered to be relatively rare in the Popo Agie Formation (Lovelace et al. 2024), with the notable exceptions being two mass death assemblages dominated by metoposaurid (Kufner and Lovelace 2018.4) and latiscopid (So et al. 2024.2) stereospondyls. Although our study demonstrates the presence of at least one dinosaur (or more depending on future consensus on the phylogenetic position of ornithischians relative to silesaurids), the relative abundance of dinosaurs in the Popo Agie fauna is still equivocal. Regardless, these new data challenge the diachronous rise hypothesis and call into question the impermeability of Pangaean latitudinal environmental barriers during the early-mid Carnian. This new assemblage is strongly reminiscent of those of dinosaur-bearing, high-latitude Gondwanan strata, making it unambiguously the oldest such assemblage in the northern hemisphere, and the oldest known low-latitude dinosaur globally.
Figure 1. A palaeogeographic map (A) of Triassic outcrops shows the position of key localities (1 to 9); Chugwater Group, Wyoming, USA (inset), local geology surrounding Garrett’s Surprise (star). Chronostratigraphic context of early dinosaur-bearing units (B) shows the relative stratigraphic positions for first occurrences of dinosaurian body and trace fossils tied to a generalized stratigraphic section (C) of the upper Chugwater Group [after Lovelace et al. (2024.1)]. The shaded box highlights the stratigraphic position of UWGM 1975 and UWGM 7407 within the Popo Agie Formation. Localities: 1, Argentina; 2, Brazil; 3, Zimbabwe; 4, India; 5, Germany; 6, Britain; 7, Morocco; 8, Texas, USA (Dockum Group); 9, south-western USA (Chinle/Moenkopi formations); 10, Wyoming, USA (Chugwater Group). Silhouettes (not to scale) on outcrop demonstrate faunal distribution within the Popo Agie and Jelm formations. At, Atreipus sp.; At–Gr, Atreipus–Grallator plexus; An, Anaschisma browni; Be, Beesiiwo cooowuse; Bu, Buettnererpeton bakeri; Br, Brachychirotherium sp.; Eu, Eubrachiosaurus browni; He, Heptasuchus clarki; Pa, Parasuchus bransoni; Po, Poposaurus gracilis; Ni, Ninumbeehan dookoodukah. Artist credits for silhouettes from Phylopic.org and abbreviated formation names provided in the Supporting Information, Text S1. Previously published dinosaur-bearing localities recovered from PBDB (PaleobioDB.org; accessed Feb, 2024; Supporting Information, Data S1).
Figure 2. Holotype left astragalus of Ahvaytum bahndooiveche gen. et sp. nov. (UWGM 1975). 3D model in (A) medial, (B) lateral, (C) lateral transparent, (D) posterior transparent, (E) distal, (F) proximal, (I) anterior, and (J) posterior orthographic views. Photographs in (G) proximal and (H) distal views. Abbreviations: amc, anteromedial corner; ap, ascending process of the astragalus; g, groove; f, foramen; ff, fibular facet; ldn, laterodistal notch (= lateroventral depression); mf, medial fossa; nf, non-articular fossa (= dorsal basin, = semi-elliptical fossa); p, platform; plp, posterolateral process; plr, posterolateral ridge; tf, tibial facet. Diagonal lines indicate broken surfaces. Arrows indicate anterior direction. Scale bar = 1 cm. STL models archived online (morphosource.org ID: 000607569).
Figure 3. Proximal end of a left femur UWGM 7549 (A–E) referred to Ahvaytum bahndooiveche gen. et sp. nov.). 3D model in (A) anteromedial, (B) posterolateral, (C) proximal, (D) anterolateral, and (E) posteromedial orthographic views. Abbreviations: alt, anterolateral tuber; amt, anteromedial tuber; ce, concave emargination; dlt, dorsolateral trochanter; ft, fossa trochanterica (= facies articularis antitrochanterica); gt, ‘greater trochanter’; pmt, posteromedial tuber; ve, ventral emargination. Arrows indicate anterior direction. Scale bar = 1 cm. STL models archived online (morphosource.org ID: 000607572).
Figure 4. Photographs of sulcimentisaurian silesaurid elements from the Garrett’s Surprise locality. Distal end of a left humerus UWGM 7550 (A–E) in (A) anterior, (B) posterior, (C) medial, (D) lateral, (E) and distal views. Proximal end of a right femur UWGM 7407 (F–J) in (F) proximal, (G) anterolateral, (H) posteromedial, (I) posterolateral, and (J) anteromedial views. Abbreviations: alt, anterolateral tuber; amt, anteromedial tuber; at, anterior trochanter; dlt, dorsolateral trochanter; ect, ectepicondyle; ent, entepicondyle; g, groove; gt, ‘greater trochanter;’ ipmt, incipient posteromedial tuber; n, notch; rc, radial condyle; uc, ulnar condyle. Arrows point in the anterior direction. Scale bar equals 1 cm.Lovelace, David M; Kufner, Aaron M; Fitch, Adam J; Curry Rogers, Kristina; Schmitz, Mark; Schwartz, Darin M; LeClair-Diaz, Amanda; St.Clair, Lynette; Mann, Joshua; Teran, Reba
Rethinking dinosaur origins: oldest known equatorial dinosaur-bearing assemblage (mid-late Carnian Popo Agie FM, Wyoming, USA)
Zoological Journal of the Linnean Society, 203(1), zlae153; DOI: 10.1093/zoolinnean/zlae153
Copyright: © 2025 The authors.
Published by Oxford University Press on behalf of the Linnean Society of London. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
Not much comfort there for creationists who've been fooled into thinking the scientific evidence is stacking up in support of the Bible's 6-10,000-year narrative and against an old earth and evolutionary biology.
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