I’m always happy to see fossil finds in the news. How that news is presented is another matter. Right after all the hype about the “BIGGEST DINOSAUR EVER!” – or not – news sources have been muddling the story of a different scrappy sauropod also found in Argentina. Contrary to headline hooks, paleontologists haven’t found a sauropod that “survived the great extinction.”
The new dinosaur, described by Pablo Gallina and coauthors in PLoS One, is named Leikupal laticauda. That title speaks to the dinosaur’s significance. Leikupal translates to “vanishing family”, underscoring the fact that this long-necked dinosaur was perhaps one of the last members of a peculiar lineage of dinosaurs called diplodocids.
If you’ve been to a major museum’s dinosaur hall, or cracked open an illustrated dinosaur book published anytime in the last century, you’re already familiar with diplodocids. These Jurassic classics included Apatosaurus, Barosaurus, and Diplodocus itself – peg-toothed giants with tapering, “whiplash” tails. Most of these distinctive dinosaurs lived in Jurassic North America, with Tornieria from the Late Jurassic of Tanzania being the sole exception, and the whole group was thought to have been snuffed out by 145 million years ago.
Leikupal changes the diplodocid story. The handful of vertebrae that distinguish this new dinosaur were found in rock layers that date to sometime between 145 and 132 million years old. That extends the time of the diplodocids just a bit further into the dawn of the Cretaceous. Even better, Leikupal was found in the Bajada Colorada Formation of western Argentina, the first time a diplodocid has ever been identified from a site in South America. Diplodocids ranged more widely in space and time than anyone previously knew.
This poorly-known sauropod was a survivor. Yet Leikupal may have been part of a “dead clade walking” – the last tatter of a previously much-richer group that has been winnowed down. And it’s that part of the story that news reports have stumbled over.
When we think of dinosaur extinction, we think of the end-Cretaceous disaster that dramatically altered the course of life on Earth. The trouble with headlines that proclaim “dinosaur survived mass extinction” is that it sounds as if Leikupal somehow dodged the asteroid that smacked into the planet 66 million years ago. The dinosaur had already been dead for at least 66 million years by then. A video by Discovery News, rightly called out by paleontologist Victoria Arbour, is the worst example of misconstruing the age and actual importance of the dinosaur.
But can we at least say that Leikupal survived a mass extinction, even if it’s not the one the public usually thinks of? Perhaps not.
Analyses of the comings and goings of prehistoric species through time have previously turned up an extinction pulse at the end of the Jurassic. The event wasn’t bad enough to compete with the “Big Five” mass extinctions, but it still seemed to be a spike from the constant, slower tick of extinction that has been going on since life first evolved.
The trouble is that sometimes “extinctions” are really false signals from rock layers that have yet to be thoroughly-explored. Recent discoveries have shown that groups of prehistoric organisms that were thought to be wiped out at the end of the Jurassic in fact survived well into the Cretaceous. Our knowledge of the fossil record is far from complete, after all, and the history of the Early Cretaceous is a time period that is undergoing rapid changes as it receives greater attention. So the end-Jurassic event might be better understood as a time of “faunal turnover” in which some lineages withered while others simultaneously thrived.
Leikupal is a dinosaur worth talking about. While only known from a set of eight vertebrae, the sauropod nevertheless alters the ending to the diplodocid story and hints at future finds, such as the Middle Jurassic sauropods that track the evolution and dispersal of these dinosaurs through the Americas and Africa. But stories such as this require nuance to explain evolutionary dramas that unfolded over millions and millions of years. Much like diplodocids, such attention to detail is in very short supply today.
Gallina, P., Apesteguía, S., Haluza, A., Canale, J. 2014. A diplodocid sauropod survivor from the Early Cretaceous of South America. PLoS ONE. 9,5: e97128. doi:10.1371/journal.pone.0097128