Professor Steve Brusatte, from the University of Edinburgh’s School of GeoSciences, is part of an international team that has uncovered evidence of the last-surviving dinosaurs in what is now New Mexico. The study, published in Science, reshapes our understanding of the final days of the dinosaurs, revealing that diverse and thriving communities persisted right up until the asteroid impact that ended their reign. An artist’s impression of the last dinosaurs from southern North America features a long-necked Alamosaurus (Natalia Jagielska) For many decades scientists have been trying to understand the events surrounding the mass extinction that wiped out the dinosaurs.The results of the research led by Professor Andrew Flynn, New Mexico State University, in collaboration with scientists at Baylor University, New Mexico Tech, the University of Edinburgh and others around the world has been published in Science. The paper “Late-surviving New Mexican dinosaurs illuminate high end-Cretaceous diversity and provinciality” takes a new look at the last-surviving dinosaur-dominated ecosystems in the San Juan Basin of northwestern New Mexico.Unlike the well-studied dinosaur communities from the Hell Creek region, dominated by Triceratops and Edmontosaurus, researchers found the New Mexico dinosaur fauna dominated by a very different kind of dinosaur – the large, long-necked sauropod Alamosaurus. Scientists estimate the Alamosaurus’ body at about the length of two semi-tractor trailer rigs and weighing in at 30 to 80 tons with a long neck and a height of about 30 to 50 feet. Imagine the Alamosaurus as the size of a blue whale but half as heavy. The extinction of the dinosaurs is the most famous instance of mass death in the history of Earth. An inconvenient truth is that until now paleontologists have had few fossils of dinosaurs unequivocally dated to the last few hundred thousand years of the Cretaceous, before the asteroid hit, so much of our understanding of the extinction was extrapolated from older fossils and statistical analyses.Now in New Mexico we have fossils of dinosaurs that were there right at the end and when we compare them with the only other fossils accurately dated from this time, from further north, we can see they are much different. There clearly were many types of dinosaurs thriving up until that moment the asteroid ended it all. Professor Steve Brusatte, Co-author Professor of Palaeontology and Evolution, School of GeoSciences Our new data shows that the dinosaurs in New Mexico, which are made up of very different species than those found in Wyoming and North Dakota, are the same age. What our new research shows is that dinosaurs are not on their way out going into the mass extinction. They're doing great, they're thriving, and that the asteroid impact seems to knock them out. This counters a long-held idea that there was this long-term decline in dinosaur diversity leading up to the mass extinction making them more prone to extinction. Another key finding is that after the extinction event, the surviving mammals still retain the same north and south bioprovinces. Mammals in the north and the south are very different from each other, which is different than other mass extinctions where it seems to be much more uniform. Professor Andrew Flynn, Lead author New Mexico State University These last non-avian dinosaurs come from the Naashoibito Member in the De-Na-Zin Wilderness Area near Farmington, New Mexico. All dinosaurs, except for birds (which are their modern descendants), became extinct about 66 million years ago when an asteroid slammed into the Yucatan peninsula in Mexico, extinguishing about 75% of all life on Earth.Dr Dan Peppe, Baylor University, co-author “The Naashoibito dinosaurs lived at the same time as the famous Hell Creek species in Montana and the Dakotas. They were not in decline. These were vibrant, diverse communities”Dr Alfio Alessandro Chiarenza, Royal Society Newton International Fellow at University College London, co-author: “For years, modelling studies predicted we’d eventually find evidence of diverse, late-surviving dinosaur communities across North America. Dinosaurs were not in decline: these communities showed no signs of inevitable extinction,” said Chiarenza.Through Earth’s history, the direction of the magnetic field flips between normal (where magnetic north is the same direction as today) and reversed (magnetic north is south). Scientists know when these magnetic field reversals happen and are able to use them to estimate when rocks were deposited. Flynn and his team measured the magnetic pole direction of the rocks and, combined with geochemical ages of crystals in sandstones of the same rocks, discovered the dinosaur fossils found in northern New Mexico were the same age as fossils of dinosaurs such as Tyrannosaurus and Triceratops found in the Hell Creek Formation located in the badlands of North Dakota and Montana. We’re able to conclusively show that these dinosaurs are from the very end of the Cretaceous. What we found is that that these rocks were deposited in the last 380,000 years of the Cretaceous period. These are the very last dinosaurs alive in New Mexico before the asteroid impact. Professor Andrew Flynn, Lead author New Mexico State University Read the full paper Read the full paper: Andrew G. Flynn et al., Late-surviving New Mexican dinosaurs illuminate high end-Cretaceous diversity and provinciality. Science 390, 400-404(2025). DOI:10.1126/science.adw3282 Related links Professor Steve Brusatte | Research Explorer Profile Publication date 27 Oct, 2025
