The Age of Dinosaurs ended about 66 million years ago. Granted, avian dinosaurs are still fluttering about, but all the fantastic non-avian forms – the sauropods, tyrannosaurs, ankylosaurs, ceratopsids, and kin – disappeared forever in one of the worst natural calamities of all time. They are never coming back.
All the same, early 20th century paleontologist William Diller Matthew once wondered if there might be another reptilian reign at some point in the distant future. In Matthew’s day, the immediate ancestors of dinosaurs were thought to be generalized little reptiles that “were probably much like the modern lizards in size, appearance, and habitat.” (This was decades before dinosauriforms such as Silesaurus and archaic dinosaurs like Eoraptor, Pampadromaeus, and Eocursor more closely constrained our understanding of what the first dinosaurs were like.) Since lizards persisted through the era of dinosaurian dominance, and had survived to the present day, Matthew wondered if modern lizards might form the rootstock for creatures just as fantastic as Allosaurus, Brachiosaurus, and Stegosaurus. He wrote:
If some vast catastrophe should today blot out all the mammalian races including man, and the birds, but leave the lizards and other reptiles still surviving, with the lower animals and plants, we might well expect the lizards in the course of geologic periods to evolve into a great and varied land fauna like the Dinosaurs of the Mesozoic Era.
Naturalist John Burroughs took exception to this. “Does not the evolutionary impulse run its course? Can or will it repeat itself?” he asked of Matthew. Dinosaurs were unique, specialized creatures that had been allotted their threescore years and ten, so to speak, and evolution showed no indication of reversing its course to bring Apatosaurus and kin back from extinction.
Matthew defended his abstract thought experiment. Even though the note was a tidbit of speculation, there was no reason to think that reptiles might not again rule the world. Matthew wrote:
Certainly such an expansive evolution of the lizards with their higher competitors removed would not cause the huge Brontosaurus to reappear on earth. But it might—if we accept the modern theory of geologic history—bring about the appearance of gigantic wading or amphibious reptiles equally huge and equally innocuous, although probably not at all like a Brontosaur in appearance.
Strange thing is, an ecosystem full of enormous reptiles thrived shortly after the demise of the non-avian dinosaurs. About 60 million years ago, in what is now northern Colombia, the 40-foot snake Titanoboa likely wrapped its body around huge crocodiles and other reptiles that inhabited the humid hothouse world of the Paleocene. There were no dinosaur mimics, but here, in these ancient swamps, reptiles were the dominant creatures. And paleontologists have just described a titanic turtle which sculled through the same vegetation-choked waters.
The turtle – described by researchers Edwin Cadena, Daniel Ksepka, and colleagues in the Journal of Systematic Palaeontology – was about the size of a mini car. Dubbed Carbonemys cofrinii, the creature’s skull was about 10 inches long. And while Cadena and colleagues refrained from officially attributing it to Carbonemys, an enormous shell found near the skull seems to fit the body size expected for the turtle. The fossilized carapace measures about five feet, seven inches long.
This turtle wasn’t the biggest of all time, but it was far larger than any other turtle found in the same habitat. And given its large size, Carbonemys was big enough to pick on other inhabitants of the Paleocene swamp.
While the paper describing the turtle provides only scant information about the creature’s biology, the promotional materials for the study cast Carbonemys as an enormous ambush predator that might have snatched up small crocs and other prey. Study co-author Dan Ksepka, in a quote provided in the paper’s official press release, said “It’s like having one big snapping turtle living in the middle of a lake.” And while tooth-marked shells show that the wetland’s crocs fed on smaller turtles, Ksepka reasoned that Carbonemys wouldn’t have much to worry about from its crocodyliform neighbors.
Future analysis and new discoveries will help fill in our understanding of the mega-turtle’s natural history. But the bigger question is why so many reptiles in the same habitat grew to be so large. A warmer climate is one possibility. Perhaps Carbonemys, Titanoboa, and the larger of their neighbors ballooned in size thanks to the equitable, hothouse world. Then again, Cadena and colleagues point out that the largest turtles of the group Carbonemys belongs to – called panpelomedusoids – are found in strata from cooler times. The reason for the gigantic nature of Carbonemys might be attributable to other ecological influences that we don’t yet understand. Whatever the reason for the turtle’s size, though, Carbonemys lived in a lush land of giants – a brief episode in time when reptiles again ruled.
Cadena, E., Ksepka, D., Jaramillo, C., & Bloch, J. (2012). New pelomedusoid turtles from the late Palaeocene Cerrejón Formation of Colombia and their implications for phylogeny and body size evolution Journal of Systematic Palaeontology, 10 (2), 313-331 DOI: 10.1080/14772019.2011.569031