Two years ago, when I was still stuck in the middle of the garden state, New Jersey State Museum assistant curator of natural history Jason Schein took me on a brief tour of his institution’s collections. There were crocodyliforms everywhere. Shelf after shelf contained the teeth, armor, and bones of a variety of prehistoric crocs that had been pulled from the roughly 65.5 million year old marl found in the southern part of the state. Among the prettiest specimens Schein pointed out to me was a virtually complete lower jaw. The fossil had been attributed to a genus called Diplocynodon, and an array of short, conical teeth were embedded in the slender jaw. What I didn’t know at the time was that I was looking at a previously-unknown species of croc unique to New Jersey.
Fossil crocodile expert Christopher Brochu described the new species with colleagues David Parris, Barbara Smith Grandstaff, Robert Denton, and William Gallagher in the latest issue of the Journal of Vertebrate Paleontology. They have called it Borealosuchus threeensis.
The crocodyliform’s species name is a testament to where it was found. In the southern part of the state, just behind a Target-dominated shopping center, there is an open-pit glauconite mine run by Hungerford and Terry, Inc. The wet, sucking green muck of the site is what’s left of a seaway which once rested over New Jersey at the terminal end of the Cretaceous and earliest part of the post-dinosaur era, the Paleocene. This site is vastly different from the dry, rocky fossil sites found out west, and many of the bones found here look like and have the consistency of chunky peanut butter. Jacketing fossils is a near-impossible task. You could wait days for plaster to completely dry in such a saturated environment. Nevertheless, a wealth of fossil creatures have been excavated from this one site – everything from bits and pieces of dinosaurs to mosasaurs and, of course, an exceptional array of at least five crocodyliform species.
One of the ways to get to this place is by way of the NJ Turnpike. As explained in the paper’s etymology section (which is my new favorite explanation of a fossil creature’s name), “threeensis” was selected for the species name “in reference to a question every New Jersey resident encounters when traveling: ‘Oh, you’re from New Jersey? Which exit?’ The type locality is most easily reached from the New Jersey Turnpike by taking Exit 3 and heading east on New Jersey Highway 168.”
But there’s more to the little jaw than just the recognition of a new species. The reassignment of the jaw also alters our understanding of crocodyliform relationships and dispersals. When the jaw was classified as Diplocynodon, it was an anomaly. Diplocynodon was a genus of crocodyliform which spread through Eurasia in the millions of years after the end-Cretaceous extinction. The existence of Diplocynodon in New Jersey would not only extend the range of the genus into the Cretaceous, but also place the east-coast specimen far afield from its Eurasian relatives.
Things look different now that the jaw has been reassigned to a new species of Borealosuchus. Whereas Diplocynodon was more closely related to alligators – an alligatoroid, in technical terms – Borealosuchus sits further down the evolutionary tree, near the base of the group which contains all living crocodiles, alligators, and gharials (the Crocodylia). And, curiously, Borealosuchus threeensis appears to be more closely related to later species of Borealosuchus from North America than to species which lived closer to it in time. (Thanks to Christopher Brochu for the correction.) Since the known material is so incomplete, however, exactly how the new species relates to others of the same genus is still a bit fuzzy.
With any luck, additional fossils will help clarify what Borealosuchus threeensis looked like and how the croc related to others of its kind. Perhaps some will turn up as a result of new, large-scale excavations. I can only hope. Rumors have been circulating that the glauconite mining operation at the pit may close in the near future, and when that happens paleontologists will lose one of the last places in New Jersey where you can so easily touch a lost world.
For more on crocodyliforms, see:
Brochu, C., Parris, D., Grandstaff, B., Denton, R., & Gallagher, W. (2012). A new species of Borealosuchus (Crocodyliformes, Eusuchia) from the Late Cretaceous–early Paleogene of New Jersey Journal of Vertebrate Paleontology, 32 (1), 105-116 DOI: 10.1080/02724634.2012.633585