{"id":45167,"date":"2025-09-29T16:24:10","date_gmt":"2025-09-29T16:24:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/il\/45167\/"},"modified":"2025-09-29T16:24:10","modified_gmt":"2025-09-29T16:24:10","slug":"dinosaurs-may-have-been-the-original-ecosystem-engineers-long-before-beavers","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/il\/45167\/","title":{"rendered":"Dinosaurs May Have Been the Original Ecosystem Engineers Long Before Beavers"},"content":{"rendered":"

\"\" <\/a>Credit: Marcin Ambrozik.<\/p>\n

Dinosaurs\u2019 eating habits and, later, their extinction may have altered the course of rivers in ancient North America, according to a new paper published in\u00a0Communications Earth and Environment<\/a>.\u00a0<\/p>\n

\u201cEcosystem engineer\u201d is the term ecologists use for a species that significantly alters its environment. Beavers and their wetland-supporting dams provide a\u00a0common example<\/a>. A new look at the stark changes in rock formations dated to just after the\u00a0dinosaurs<\/a>\u00a0went extinct suggests that they, too, could have been ecosystem engineers.<\/p>\n

The research team suggests dinosaurs once cut down enough vegetation (through consuming, trampling, or uprooting) to create wide floodplains. After\u00a0an asteroid wiped out dinosaurs<\/a>, along with three quarters of life on Earth, forests emerged, constraining rivers to narrower, meandering paths.<\/p>\n

\u201cThe only thing that fit all the evidence we had was that it\u2019s actually the removal of dinosaurs that [changed rivers],\u201d said\u00a0Luke Weaver<\/a>, a paleontologist at the University of Michigan\u2019s Museum of Paleontology and lead author of the new study.\u00a0<\/p>\n

The argument upsets a long-held hypothesis that ancient North America was a wet, frequently flooded place in the few million years following dinosaurs\u2019 disappearance.<\/p>\n

An Ancient Asteroid Hits<\/p>\n

The North American geologic record shows a stark contrast, called a facies shift, between sedimentary rocks of the Late Cretaceous (just before dinosaurs\u2019 extinction) and those created in the early Paleogene (just after dinosaurs\u2019 extinction).\u00a0For example, a Late Cretaceous formation in the present-day Great Plains, called the Hell Creek Formation, is composed of dark, gray-green mudstone. The early Paleogene rock directly above it, called the Fort Union Formation, looks much different: It\u2019s marked by various deposits of coal and brightly colored layers described as pajama stripes.<\/p>\n

Between these dinosaur and postdinosaur periods, scientists have found a layer of rock with elevated amounts of iridium, an element rare on Earth but common on asteroids. This layer, called the Cretaceous-Paleogene boundary, or KPB, is thought to have been created by the impact of the asteroid that led to\u00a0the extinction<\/a>\u00a0of most dinosaurs.\u00a0<\/p>\n

However, it\u2019s not widely accepted by scientists that the Hell Creek\u2013Fort Union shift and the KPB are actually related. \u201cMost people have argued that it\u2019s a coincidence,\u201d Weaver said.<\/p>\n

To further examine whether the KPB was linked to the facies shifts, Weaver and his colleagues examined five locations with facies shifts in the western United States that they thought might show the iridium anomaly. They found it in all five spots.<\/p>\n

\u201cSure enough, they\u2019re following the same trend,\u201d Weaver said. \u201cIt\u2019s a phenomenon that is true across the entire region.\u201d He and the research team take the iridium results as evidence that the change in geology between the Late Cretaceous and early Paleogene formations is not simply a coincidence but related to the catastrophic asteroid impact 66 million years ago.\u00a0<\/p>\n

Ponds or Not?<\/p>\n

Yet another mystery lurks in these rock formations. Paleontologists generally agree that the Late Cretaceous sediments of the Hell Creek Formation suggest an environment with waterlogged soils and small river deposits: a floodplain with poorly constrained river flow.\u00a0<\/p>\n

But what happened to create the features found in the early Paleocene Fort Union Formation, after the dinosaurs went extinct, is less settled. Previous research interpreted the formation\u2019s pajama-striped pattern as variegated beds\u2014rock features that are horizontal, uniformly fine grained, laminated (composed of very thin layers of sediment), and extensive (sometimes stretching for kilometers).<\/p>\n

These variegated beds were likely formed by ponds, said\u00a0David Fastovsky<\/a>, a sedimentary geologist and paleontologist emeritus at the University of Rhode Island. Fastovsky was the\u00a0first to interpret<\/a>\u00a0how the pajama-striped features may have formed.<\/p>\n

His interpretation aligns with what others have called the \u201cwet Paleogene\u201d hypothesis\u2014the idea that the early Paleogene was characterized by a high water table, possibly due to sea level rise.\u00a0<\/p>\n

Weaver and his colleagues offer a different explanation. \u201cThere are a lot of reasons why we didn\u2019t think that was a legitimate interpretation,\u201d Weaver said.<\/p>\n

Instead, the research team thinks waterways in the early Paleogene were much more structured and that it\u2019s more likely the pajama-striped beds are point bar deposits\u2014accumulations of sediment that occur in the bends of constrained, meandering rivers. The deposits are tilted, and the sediments\u2019 grain size increases nearer the bottom of the tilt, the paper states.<\/p>\n

\u201cAll of those features combined are things that are very indicative of point bar deposits,\u201d Weaver said.\u00a0<\/p>\n

Fastovsky disagrees. While point bar deposits certainly exist in the Fort Union Formation, he said the pajama-striped formations are definitively not examples of them. He thinks it\u2019s likely that the research team misinterpreted what they called \u201cvariegated beds\u201d in the formation.\u00a0<\/p>\n

\u201cWe\u2019re not talking about the same rocks,\u201d he said.<\/p>\n

\"\" <\/a>Two areas of the Fort Union Formation in present-day Montana (marked E and F) were interpreted as point bars\u2014accumulations of sediment found in the bends of meandering rivers\u2014by the research team. Credit: Weaver et al., 2025,\u00a0https:\/\/doi.org\/10.1038\/s43247-025-02673-8<\/a><\/p>\n

For example, some images of the Paleogene beds presented in the paper show an obvious dip, indicating to Fastovsky that the team wasn\u2019t looking at the actual variegated beds in the Fort Union Formation. \u201cThey correctly identified what they saw, but what they saw was not, as they suggested, what we have been calling \u2018variegated beds,\u2019\u201d Fastovsky wrote in an email.\u00a0<\/p>\n

Weaver said it\u2019s unlikely his team analyzed the incorrect beds. \u201cEverywhere that we see those thin beds, those sandstones and mudstones that [Fastovsky] interpreted as pond deposits, we found them to have some degree of depositional dip,\u201d he said, adding that his research team visited nearly every spot where Fastovsky did his work.<\/p>\n

\u201cThe obvious evidence for major flooding at that time\u201d cannot be ignored regardless of the interpretations, Fastovsky said. Despite the disagreement, he said it\u2019s still possible that dinosaurs altered the landscape and the way rivers flowed.<\/p>\n

Ecosystem Engineers<\/p>\n

The study\u2019s authors argue that together, their findings of additional iridium anomalies and their new interpretation of the Fort Union Formation suggest that herds of Cretaceous herbivorous dinosaurs (like\u00a0triceratops<\/a>) could have been ecosystem engineers, drastically changing the landscape in which they lived.<\/p>\n

Scientists know from research on modern ecosystems that large, terrestrial animals influence the type and amount of vegetation that grows on a landscape. For example,\u00a0bison may influence nutrient cycling<\/a>\u00a0and grassland growth in the Great Plains, and African elephants routinely\u00a0destroy trees and sediment<\/a>\u00a0in search of food.<\/p>\n

In the new study, the authors write that large, herbivorous dinosaurs of the Late Cretaceous were likely no different. They consumed large amounts of vegetation, keeping the landscape free of dense forest and allowing water to flow across wide, open plains.\u00a0<\/p>\n

Paleobotany studies\u00a0have shown<\/a>\u00a0that after the asteroid hit, plant communities changed drastically, too: Late Cretaceous forests were more open, while early Paleogene forests had closed canopies and denser growth.<\/p>\n

There\u2019s simply not enough data, however, to definitively answer the question of whether the dinosaurs\u2019 disappearance caused the change in vegetation, said\u00a0Jordan Mallon<\/a>, a paleobiologist and dinosaur ecologist at the Canadian Museum of Nature who was not involved in the new study.\u00a0<\/p>\n

\u201cWithout a doubt, these animals had some impact on their environment\u2014you\u2019re talking about many, multi-ton species that were abundant on the landscape,\u201d Mallon said. However, scientists have little information about what that specific impact may have been.<\/p>\n

There\u2019s little evidence available, for example, about the particular eating habits of the large Cretaceous herbivores seen in the fossil record, such as what species of plants they ate or in what quantities.<\/p>\n

\u201cWe really don\u2019t know exactly how dinosaurs modified their landscapes,\u201d he said.<\/p>\n

This article originally appeared in EOS Magazine.<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Credit: Marcin Ambrozik. Dinosaurs\u2019 eating habits and, later, their extinction may have altered the course of rivers in…\n","protected":false},"author":2,"featured_media":45168,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[10828,3185,85,46,141],"class_list":{"0":"post-45167","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-dinosaurs","9":"tag-ecosystems","10":"tag-il","11":"tag-israel","12":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/45167","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=45167"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/45167\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/45168"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=45167"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=45167"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=45167"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}