The find is particularly significant as it corresponds to the emergence of the Bering Land Bridge, an expanse of land that once connected the two continents, says the study.<\/p>
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The research team found approximately 75 fossil tracks, including this theropod track. Credit: Fiorillo et al., Geosciences 2024<\/figcaption><\/figure> The research was led by palaeontologist Anthony Fiorillo, executive director of the New Mexico Museum of Natural History and Science<\/a>, alongside an international team of scientists, including geology professor Paul McCarthy from the University of Alaska Fairbanks<\/a>. <\/p>
\u201cWe’ve had projects for the last 20 years in Alaska trying to integrate sedimentology, dinosaur palaeontology and the palaeoclimate indicators,\u201d says McCarthy. <\/p>
\u201cWe\u2019ve done work in three other formations \u2014 in Denali, on the North Slope and in Southwest Alaska \u2014 and they’re about 70 million years old.\u201d<\/p>
\u00a0\u201cThis new one is in a formation that’s about 90 to 100 million years old.”<\/p>
\u201cIt was just like we were walking through the woods of millions of years ago.” <\/p><\/blockquote>
Fiorillo notes the importance of the age: “What interested us about looking at rocks of this age is this is roughly the time that people think of as the beginning of the Bering Land Bridge \u2014 the connection between Asia and North America. We want to know who was using it, how they were using it and what the conditions were like.”<\/p>
According to the paper, research into the palaeoclimate can help scientists understand global warming today.<\/p>
\u201cThe mid-Cretaceous was the hottest point in the Cretaceous,\u201d says McCarthy. \u201cThe Nanushuk Formation gives us a snapshot of what a high-latitude ecosystem looks like on a warmer Earth.\u201d\u00a0<\/p>
The Nanushuk Formation is a thick outcropped layer of sedimentary rock, which dates to roughly 94 million to 113 million years ago in the mid-Cretaceous Period \u2013 around the time when the formation of the Bering Land Bridge began.<\/p>
![\"Small](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/62\/2024\/03\/Small-tridactyl-tracks-with-three-slender-toe-impressions-attributable-to-avian-theropods.-The-heat-map-right-signifies-red-for-higher-elevations-and-blue-for-lower-elevations.-The-scale-bar-is-in-centimeters.jpeg\")
Small tridactyl tracks with three slender toe impressions attributable to avian theropods. The heat map (right) signifies red for higher elevations and blue for lower elevations. The scale bar is in centimetres. Credit: Fiorillo et al., Geosciences 2024<\/figcaption><\/figure> Walking into the past<\/h3>
During the fieldwork, which took place in 2015\u20132017, the team found approximately 75 dinosaur tracks (along with other related indicators) on Coke Basin, a geologic feature of the Nanushuk Formation.<\/p>
\u201cThis place was just crazy rich with dinosaur footprints,\u201d says Fiorillo. <\/p>
“Research into the palaeoclimate can help scientists understand global warming today.”<\/p><\/blockquote>
The researchers were particularly intrigued by one site where an ancient landscape revealed itself through fossilised trees, tracks and faeces.<\/p>
\u201cWe were at a spot where we eventually realised that for at least 400 yards we were walking on an ancient landscape,\u201d says Fiorillo. <\/p>
\u201cOn that landscape we found large upright trees with little trees in between and leaves on the ground. We had tracks on the ground and fossilised faeces.\u201d<\/p>
\u201cIt was just like we were walking through the woods of millions of years ago.”<\/p>
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Abundance of birds <\/h3>
\u201cOne of the things we did in our paper was look at the relative frequencies of the different kinds of dinosaurs,\u201d says Fiorillo. \u201cWhat was interesting to us was that the bipedal plant eaters were clearly the most abundant.\u201d<\/p>
The paper says that 59% of the total tracks discovered belonged to two-legged plant eaters and 17% were four-legged plant eaters. Meanwhile, birds accounted for 15% and non-avian, mostly carnivorous, bipedal dinosaurs were 9%.<\/p>
\u00a0\u201cOne of the things that was interesting is the relative frequency of bird tracks,\u201d Fiorillo says. He points out that nearly half of North America\u2019s shorebirds breed in the warm months of today\u2019s Arctic. The bird tracks along the Kukpowruk River indicate that the warm paleoclimate may have similarly influenced bird populations during the Cretaceous Period, suggests the study.<\/p>
\u201cThe samples we analyzed indicate it was roughly equivalent to modern-day Miami. That\u2019s pretty substantial.\u201d <\/p><\/blockquote>
Exotic Alaska<\/h3>
Carbon isotope analysis of wood samples provided insights into precipitation levels, indicating an annual rainfall of about 70 inches, supporting global precipitation patterns associated with the Cretaceous Thermal Maximum (a long-term trend approximately 90 million years ago when average global temperatures were significantly higher than those of today).<\/p>
\u201cThe temperature was much warmer than it is today, and what\u2019s possibly more interesting is that it rained a lot,\u201d says Fiorillo. <\/p>
\u201cThe samples we analysed indicate it was roughly equivalent to modern-day Miami. That\u2019s pretty substantial.\u201d<\/p>
McCarthy\u2019s role as a fossil soils expert was to interpret the type of environment that existed at the time: \u201cWe can say here’s a river channel, here’s a flood deposit, here’s a levee, here’s the floodplain, here’s a swamp. And so if we’re able to find tracks in that section, then you can sometimes say that a group of dinosaurs seems to have really liked being here as opposed to there.\u201d<\/p>
Despite these revelations, Fiorillo emphasises that there is still much more to uncover. <\/p>
\u201cThis puts a new dot on the map and tells us there’s a lot here, and it fits into the bigger picture,\u201d he says. \u201cThe big picture is we’re trying to get better resolution on what life was like in the high latitudes back at the time the dinosaurs were roaming around.\u201d<\/p>
Find out more about the study: New Dinosaur Ichnological, Sedimentological, and Geochemical Data from a Cretaceous High-Latitude Terrestrial Greenhouse Ecosystem, Nanushuk Formation, North Slope, Alaska<\/em><\/a><\/p>
More prehistoric discoveries<\/strong><\/p>
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Main image credit: Fiorillo et al., Geosciences 2024<\/em><\/p> <\/body><\/html>\n
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