On a remote stretch of the Rocky Mountain foothills in northeastern British Columbia, footprints first glimpsed in 1988 have finally been read in depth, revealing a moment in the deep past that western Canada's stone records mostly passed over. About 86 million years ago, when the sea stood high and reached the mountains' edge, a river delta spread across a green, low-lying land where herbivores and their predators walked the sandy banks. Researchers Guy Plint and Charles Helm suggest that the rising crowd of plant-eating and hunting dinosaurs was bound up with the quiet spread of flowering pl
Rare Coniacian Dinosaur Tracks in B.C. Reveal a Flowering-Plant World 88 Million Years Ago
The only Coniacian land rocks in western Canada hold the tracks
Mark
Why do tracks from one remote corner of B.C. matter?
Mimi
Because Coniacian rocks across western Canada are marine, except around Tumbler Ridge. This delta is basically the only place to see land animals from that moment.
Mark
And what did the tracks show?
Mimi
Mostly ornithopods, with three blunt toes, 30 to 50 centimetres wide. Then theropod tracks with claw marks, and a few rare rounded prints that might be ankylosaurs.
Luke
Worth noting that the theropod and ankylosaur identifications are the authors' belief and a maybe. Only the ornithopod call is stated firmly.
Mark
The older formations were dominated by ankylosaur tracks. What changed?
Mimi
The Marshybank plants are mostly flowering plants, which were more nutritious and recovered faster from grazing.
Luke
That's the authors' argument, though, not a demonstrated cause. The tracks show which animals walked there and the fossils show which plants grew there. The link between them is an inference.
Mark
Is there anything we don't know?
Luke
Plenty. The piece doesn't say how many tracks were found or how many sites. It also doesn't say why the shift happened elsewhere.
Mimi
Which is why the authors point to future fossil work.
O Pulso
- Tracks sat unexamined for decades in a region so remote that the question of who would reach them stayed open until 2022.
- A rare window opened: the only terrestrial rock of its age in western Canada, while everything around it lay beneath an ancient sea.
- Crowds of three-toed ornithopod prints and sharp-clawed theropod trails overlap on trampled sand, hinting at a busy, crowded shoreline.
- The authors trace the surge of herbivores to flowering plants richer in nutrition and quicker to regrow, a link still waiting for more fossils to confirm it.
On a remote stretch of the Rocky Mountain foothills in northeastern British Columbia, footprints first glimpsed in 1988 have finally been read in depth, revealing a moment in the deep past that western Canada's stone records mostly passed over. About 86 million years ago, when the sea stood high and reached the mountains' edge, a river delta spread across a green, low-lying land where herbivores and their predators walked the sandy banks. Researchers Guy Plint and Charles Helm suggest that the rising crowd of plant-eating and hunting dinosaurs was bound up with the quiet spread of flowering plants, a reminder that even the landscape's newest growth can reshape which creatures thrive.
In the foothills of the Rockies in northeastern British Columbia, a scatter of dinosaur footprints was noticed in 1988, but the site lay so far from roads and people that serious study did not begin until 2022. Now the tracks are telling a story that western Canada's rocks rarely preserve.
The setting was dramatic. Between roughly 95 and 84 million years ago, sea levels were exceptionally high, and the water reached almost to the mountains. Rivers pushed sediment into the Interior Seaway and built deltas along its western edge. Across western Canada, rocks of this age are marine, with one exception: the Tumbler Ridge area, where a river delta reached into the sea and left land deposits behind, the Marshybank Formation.
This was a low, watery country of lakes, mires and slow rivers beneath dense vegetation, including stands of large conifers. When floods spread sand across the floodplain, the sheets of sand kept the imprints of animals that had walked through soft mud. The most common tracks are broad, three-toed prints of duck-billed herbivores. Narrower, clawed prints likely belong to meat-eating theropods, and a few rounded marks may be from armoured ankylosaurs.
The plants tell the rest. Alongside ferns and conifers grew a majority of flowering plants, which were more nutritious, easier to digest and quicker to recover after being eaten. The authors, Guy Plint and Charles Helm, argue that this change in plant life helped drive the flourishing of herbivores and the predators that followed them. Future fossil work may test that idea.
In the foothills of the Rocky Mountains in northeastern British Columbia, a set of dinosaur footprints was first noticed in 1988. The site was so remote that serious investigation did not begin until 2022. What researchers have since described is a rare record of a stretch of time that barely shows up in western Canada's rocks.
The setting matters. Between about 95 and 84 million years ago, during the late Cenomanian, Turonian, Coniacian and Santonian stages of the Cretaceous, sea levels were exceptionally high. Shorelines were pushed west until water lapped against the Rocky Mountain foothills. Rivers carried sediment into the Interior Seaway, building deltas and coastal plains along its western edge, and over millions of years the sea rose and fell, alternately narrowing and widening that plain.
Across western Canada, rocks of Coniacian age are entirely marine, with one exception: the small Tumbler Ridge area. There a river system built a delta reaching eastward into the seaway. Its deposits are known as the Marshybank Formation, and, critically, they include terrestrial layers that preserved the tracks. The wider Tumbler Ridge area holds land deposits spanning much of the Cretaceous, with a rich record of vertebrate tracks, including giant crocodiles, birds, pterosaurs and many dinosaurs. The Tumbler Ridge Museum houses and exhibits many of them, and the area became a UNESCO Global Geopark in 2014.
The Marshybank delta was low-lying, a land of shallow lakes, mires and floodplains crossed by slow, winding rivers. Abundant fossil roots point to dense vegetation, and preserved stumps indicate stands of large trees, probably conifers such as dawn redwood. When rivers flooded, they spread sand beyond their banks in thin sheets called crevasse splays. The undersides of those sheets preserve natural casts of tracks pressed into soft mud, and the sandy channel banks were thoroughly trampled by dinosaurs.
The most common prints have three broad, blunt toes and measure 30 to 50 centimetres wide. These are ornithopod, or duck-billed dinosaur, tracks, left by large herbivores that could walk on two legs or shift to four. Next most common are prints with three narrower, longer toes tipped with claw marks, which the authors believe belong to carnivorous theropods. A few rare rounded tracks with four or five indistinct digits may have been made by ankylosaurs, the armoured dinosaurs.
The tracks resemble a contemporaneous find from the Frontier Formation in southwestern Montana, and share much with the dinosaur fauna of the overlying Wapiti Formation, which dates from 84 to 66 million years ago. They differ sharply from older layers: the Dunvegan Formation (97 to 95 million years ago) and the Gates Formation (109 to 107 million years ago) are dominated by ankylosaur tracks instead.
The plant fossils help explain the shift. Marshybank strata contain gymnosperms such as conifers, cycads and ginkgos, along with ferns and horsetails. Most of the flora, though, are angiosperms, or flowering plants, possibly distant relatives of modern plane, poplar and willow, plus laurel, buckthorn, soapberry and low shrubs and herbs. Angiosperms arose in the tropics about 130 million years ago and reached Alaska roughly 30 million years later.
Flowering plants were more nutritious and easier to digest than conifers, cycads and ferns, and they grew faster and recovered better from being cropped. The authors, Guy Plint of Western University and Charles Helm of Nelson Mandela University, argue that the proliferation of Coniacian herbivores, especially ornithopods, and of the carnivores that hunted them, is tied to the diversification and spread of flowering plants. Further fossil work at the site may test that link.
Citações Notáveis
The rise of Coniacian herbivorous dinosaurs, and the carnivores that preyed on them, is related to the spread of flowering plants.— Guy Plint and Charles Helm, paraphrased
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