An international team of paleontologists from Australia, Canada and Italy has documented more than 100 footprints of hadrosaurid and tyrannosaurid dinosaurs preserved within the bank of the Redwillow River, located near the city of Grande Prairie in Alberta, Canada.
Hypothetical reconstruction of the Tyrants Aisle tracksite during track formation, depicting a small herd of Edmontosaurus regalis as they produce tracks in a riverine setting; a lone tyrannosaurid dinosaur watches the herd, while a pair of troodontids scuffle nearby. Image credit: José Vitor Silva.
The 72.5-million-year-old dinosaur footprints were discovered at the Tyrants Aisle locality, the largest tracksite known from the Late Cretaceous Wapiti Formation of northwest Alberta and northeast British Columbia.
This locality occurs in the lower part of Unit 4 of the formation, exposed along the southern bank of the Redwillow River.
More than 100 dinosaur tracks are preserved across at least three distinct track-bearing layers, indicating that this area was traversed by different sets of dinosaurs for some time, possibly following the margins of an ancient river system.
“It was important that we carefully document this site while it is still available to us,” said lead author Nathan Enriquez, a Ph.D. student in the Palaeoscience Research Centre at the University of New England.
“The site is submerged by the Redwillow River for much of the year and is continuously eroded. By the time we found the site, much information had already been lost. Sadly, the tracks will eventually be lost to time.”
“However, our work guarantees that the information presently contained at the site will be available for generations to come and, through the use of digital technology, 3D models are now available of the most significant footprints and trackways.”
“We feel we have done these tracks justice, and are proud to present this special window into the lives of these fascinating animals.”
Representative hadrosaurid tracks from Tyrants Aisle: (A) photograph, (B) digital elevation model, and (C) interpretive illustrations of Hadrosauropodus tracks; the blue writing board measures 11.8 cm (4.6 inches) wide and 18.7 cm (7.4 inches) tall; warm and cool colors indicate relatively high and low topography, respectively; (D) photograph, (E) digital elevation model, and (F) interpretive illustration of hadrosaurid morphotype A track. Image credit: Enriquez et al., doi: 10.1371/journal.pone.0262824.
The most abundant tracks at the Tyrants Aisle locality are those of hadrosaurs.
The biggest of their footprints measured 65 cm (25.6 inches) long, suggesting the animal was 2.6 m (8.5 feet) tall at the hips.
The paleontologists suggest the trackmaker was a species of comb-crested hadrosaurid dinosaur called Edmontosaurus regalis.
“They may have acted a bit like cows, grazing on low-growing vegetation and forming herds,” Enriquez said.
Tridactyl theropod-like footprints at Tyrants Aisle greater than 45 cm (17.7 inches) in length can be attributed with confidence to tyrannosaurids.
Smaller footprints of troodontid and ornithomimid dinosaurs as well as azhdarchid pterosaurs also represent at the site.
“The best-preserved tyrannosaur track at the site measures almost 50 cm (19.7 inches) in length and, based on the age of these rocks, was possibly produced by Albertosaurus sarcophagus, an earlier relative of Tyrannosaurus rex,” Enriquez said.
The team’s paper was published online in the journal PLoS ONE.
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N.J. Enriquez et al. 2022. The dinosaur tracks of Tyrants Aisle: An Upper Cretaceous ichnofauna from Unit 4 of the Wapiti Formation (upper Campanian), Alberta, Canada. PLoS ONE 17 (2): e0262824; doi: 10.1371/journal.pone.0262824
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