A new species of daspletosaurus has been excavated in rocks of intermediate age from a Montana tyrannosaur site, making it a “missing link” with the T.rex.
Daspletosaurus wilsoni sample a combination of features found in more primitive tyrannosaurs from older rockssuch as a set of prominent horns around the eye, as well as features known from later members of this group (including T. rex), such as a high eye socket and expanded air sacs in the skull, reports the Dickinson Museum Center.
These findings suggest that previous research was correct in identifying several species of Daspletosaurus as a single evolutionary lineage and support that T. rex is descended from this group.
the new studio, published in Peer J. supports adding tyrannosaurs to a growing list of dinosaurs (including horned and duck-billed dinosaurs) for which anagenesis (linear evolution) has been proposed. This seems to suggest that linear evolution is more widespread in dinosaurs, sbranching evolution being less frequent than previously thought.
Daspletosaurus wilsoni it means “Wilson’s fearsome reptile”named for John “Jack” P. Wilson (San Diego, California), who discovered the holotype specimen. The holotype specimen (BDM 107) was collected from exposures from the Judith River Formation in Valley County, northeastern Montana.
In the Late Cretaceous of North America, many families of dinosaurs are represented by multiple, closely related species. Previously it was thought that these represented diversity, that is, that they lived at the same time, which would be evidence of branching evolution. However, a large number of new specimens and a better understanding of their location in time have changed what we think of.
Now we can see that many of these species are very finely separated from each other in time, forming consecutive ladder-like rungs in a single evolutionary lineage where an ancestral species evolves directly into a descendant species. This is called the “anagenesis” mode of evolution and is contrasted with “cladogenesis,” where successive branching events produce many species that are closely related and thus resemble each other, but represent evolutionary “cousins.” instead of ancestors and descendants.
Elias Warshaw is currently conducting more detailed research into the link between T. rex and Daspletosaurus.
The new species is based on a skull and a partial skeleton (BDM 107) recovered by the Badlands Dinosaur Museum between 2017 and 2021. The original discovery was made in 2017 by crew member Jack Wilson, who saw a small, flat piece of bone sticking out of the bottom of a towering cliff. This distinctive flat bone was the middle part of a tyrannosaur’s nostril. A careful excavation around the bone revealed a complete premaxilla, which is the bone at the tip of the snout.
Some broken vertebrae from around the site showed that it was a large tyrannosaurus, but there was ~25 ft (8 m) of rock over the bones. Field teams in 2020 and 2021 used a jackhammer to excavate down to the bone layer and uncovered a partial skull and skeleton. The seemingly never-ending task of removing the overload gave rise to the specimen’s nickname “Sisyphus,” after the figure from Greek mythology.