A new look at the nearly forgotten bones could change how we think about pre-dinosaur reptiles, and their discovery that they are the oldest known marine reptile fossils in the Southern Hemisphere. report in Current Biology — and also serves as a legacy to the scientists who prompted the reassessment.
Dinosaurs and Ancient Reptiles
Before the dinosaurs ruled the land, reptiles ruled the seas for millions of years. Sauropods are the most diverse and geologically longest-surviving group of aquatic reptiles, with an evolutionary history spanning more than 180 million years.
All marine reptile fossils associated with the beginning of the Age of Dinosaurs have been found to be located within an ancient low- to mid-latitude belt stretching from present-day East Asia, the Middle East, and Europe to northwestern North America.
“In contrast, the Southern Hemisphere has been a blank slate until now,” he said. Benjamin Kear From the Uppsala University Museum of Evolution. New Zealand lies on the Antarctic coast of a global super-ocean called Panthalassa, making it “an unexpected place for early marine reptiles,” Keir said.
read more: 5 of the Most Interesting Prehistoric Marine Reptiles
Revisiting forgotten fossils
In late 2018, Euan Fordyce of the University of Otago in New Zealand rediscovered the fossils of a marine reptile in the South Island that had been found by geologists in 1978 and largely forgotten. Fordyce notified Kier and asked him to examine the bones, which are in the National Palaeontology Collection at the National Science Centre of New Zealand. COVID-19 border closures delayed Kier’s visit.
“Unfortunately, Euan passed away before I could get around to looking at the specimen,” says Keir, but last year he borrowed the fossil from GNS Science in New Zealand and hired a team to analyze it.
When he and his colleagues examined it, they found it to be a nothosaur, a type of aquatic reptile that lived about 240 million years ago, before the rise of the dinosaurs. Nothosaurus was up to 22 feet long and paddled on four legs. Its flattened skull had thin, conical teeth that it used to catch fish and squid.
Keir says the discovery is twofold: Its age and location mean the team determined that the fossil is 40 million years older than any sauropod fossils previously found in the Southern Hemisphere.
read more: How the Age of Reptiles Started 250 Million Years Ago
Mapping Migration
The time and place of origin of the fossils, combined with sophisticated evolutionary models and mapping, suggest that nothosaurus originated near the equator and migrated north and south.
Their emergence and migration likely began shortly after the devastating mass extinction 252 million years ago that marked the beginning of the Age of Dinosaurs.
“Simply put, this means that ecological opportunism, adaptive evolution and globalization in the earliest land-to-sea vertebrate transitions were interconnected and occurred simultaneously, or at least within a very short time interval,” Keir said.
read more: 5 mass extinctions that struck Earth
More discoveries of Nothosaurus fossils
The exact route that Nothosaurus took is unknown, but some theories suggest that they may have traveled along the Arctic coastline, swam inland seas, or used ocean currents to cross the Panthalassa Ocean.
But this new discovery will likely inspire more paleontologists to search farther and further afield in search of more nothosaurus fossils.
“In terms of where we could find more, we currently have the potential to find more just about anywhere there are marine rocks of the right age and depositional environment,” Kier said. “Frankly, the race is on to find the next one!”
New Zealand nothosaurus fossils National Paleontological Collections at GNS Science In New Zealand, the authors dedicated the paper to Fordyce.
read more: Why were prehistoric marine reptiles so huge?
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Prior to joining Discover, Paul Smaglik spent more than 20 years as a science journalist specializing in U.S. life sciences policy and global scientist career issues. He began his career in newspapers but moved to science magazines. His work has appeared in publications such as: Science News, Science, Natureand Scientific American.
