When I was growing up I used to spend hours poring over the Time/Life series of nature books in my little library, absolutely enthralled by images of strange creatures from all over the world, but one photograph was particularly arresting. A grainy black-and-white double-page spread showed an anaconda that had wrapped its crushing coils around a caiman and a tree, slowly squeezing the life out of the crocodylian. Without any frame of reference for size it was easy to envision the two animals as giants, but that was just my b-movie fueled imagination running wild. Even though both anacondas and caimans are large reptiles they do not achieve the monstrous proportions seen in late night creature features.
As discovered by scientists last year, however, in the wake of the mass extinction that wiped out the non-avian dinosaurs a cousin of living anacondas grew to prodigious size. Named Titanoboa, this 60 million year old snake was at least 40 feet long and lived in an ancient swamp in what is now Colombia. That same habitat was also inhabited by plenty of potential prey, from fish to turtles, and one of the larger potential menu items has just been described by paleontologists Alexander Hastings, Jonathan Bloch, Edwin Cadena, and Carlos Jaramillo in the latest Journal of Vertebrate Paleontology.
At an estimated seven feet long, the crocodile-like Cerrejonisuchus improcerus would have been relatively easy prey for Titanoboa. Classified as a dyrosaurid it was only a cousin of living crocodiles and caimans, but in its Paleocene habitat it probably inhabited a similar niche as a semiaquatic predator. More than being just a Titanoboa snack, however, Cerrejonisuchus is helping scientists to understand how extinct relatives of crocodiles spread throughout the world in the distant past.
The idea that crocodylians have "been unchanged since the time of the dinosaurs" is one of the standard tropes of nature documentaries. It is also wrong. True, reptiles similar to living alligators and crocodiles have been around for millions of years, but the "living fossil" angle obscures the fact that these extant species are vestiges of a much more diverse array of bizarre prehistoric animals. There were ocean-going forms, species with armadillo-like armor, and terrestrial types that died out only in the last few thousand years, just to name a few.
The dyrosaurids were part of this radiation of lost lineages, and many of them lived during the Paleocene (the 10 million years between the end of the Cretaceous and the dawn of the Eocene). Many of them have been found in Africa, with a few more from Asia, Europe, and North America, but South American dyrosaurids are much rarer. Cerrejonisuchus, a relatively short-snouted type recognized from three nearly complete skulls and lower jaw, thus provided a way to compare dyrosaurids from around the globe in an attempt to figure out where the group first evolved.
When the authors of the new research ran a cladistic analysis to determine the relationships of the dyrosaurids they also kept track of where the animals had been found. The pattern that emerged appeared to pin Africa as the place of origins for the crocodile relatives, but the existence of forms elsewhere at different times suggested that there had been at least three dispersals of dyrosaurids out of Africa. Cerrejonisuchus represented an early dispersal just after the end of the Cretaceous, and its small size and short snout, both unusual for members of this group, hinted that it was quickly adapted to be more of a generalist feeder than its narrow-mouthed, fish-eating relatives. Furthermore, the presence of dyrosaurids such as Cerrejonisuchus in South America 60 million years ago was consistent with the idea that these marine and coastal crocs swam up the coastline to reach North America once they had crossed the ocean from Africa.
As interesting as this might be to vertebrate paleontologists, however, it is not the kind of story you expect to make headlines. Most members of the public have never even heard of a dyrosaurid, hence all the press releases about Cerrejonisuchus being prey for Titanoboa. There is nothing about the interaction between the two reptiles in the paper, and no hard evidence that Titanoboa consumed the dyrosaurid, but given that the giant snake had to be eating something it is not unreasonable to assume that Cerrejonisuchus sometimes wound up as a meal. Perhaps we will see a paper on this subject sometime in the future. As work continues on the site that yielded both reptiles I can only hope that we hear more about this unique slice of prehistory.
[Ed. note - I previously identified the croc in the uppermost photo as Cerrejonisuchus. This was an incorrect assumption on my part. Whatever it is, though, I look forward to hearing more about it.]
Alexander K. Hastings; Jonathan I. Bloch; Edwin A. Cadena; Carlos A. Jaramillo (2010). A new small short-snouted dyrosaurid (Crocodylomorpha,
Mesoeucrocodylia) from the Paleocene of northeastern Colombia Journal of Verterbrate Paleontology, 30 (1), 139-162 : 10.1080/02724630903409204
Nice write up Brian! I was still a staff science writer at the Florida Museum of Natural History when Dr. Bloch first told me about his work describing Titanoboa and it's body size. I asked him how big the vertebra was that they were using for the estimates and he gestured with his hands and said "about as big as a dinner plate." That made an impression on me!