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An Ancient Alligator for the Alf Museum

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Lower jaw and reconstructed skull of LeidyosuchusAncient Utah was even more infested by crocodilians than thought, thanks to a new discovery announced by the Alf Museum. This 75 million year old partial skeleton turns out to be from an early alligator called Leidyosuchus, which had previously only been known from rocks of a similar age in Alberta. With this find, scientists have identified a whopping six different kinds of ancient crocs living in southern Utah at the same time!

The Alf Museum's Leidyosuchus was discovered in 2010 by Kevin Quick, a science teacher at The Webb Schools (Claremont, California), and Sam Woodward '12, then a high school student at Webb. They were on a summer paleontology expedition with the museum in southern Utah, within Grand Staircase-Escalante National Monument. Kevin found a small cobble with a piece of bone sticking out one end; returning to the site with Sam, they together found the rock layer where the fragment had originated. Excavations in 2011 uncovered the partial skeleton of this animal, including lower jaws, osteoderms (bony plates embedded in the back of the animal), ribs, vertebrae, and limb bones.

In collaboration with Augustyn Family Curator Dr. Andy Farke, Webb students Madison Henn '13, Albert Xu '13, and Sam Woodward '12 worked to identify the type of animal that the bones came from. Several features in the skeleton identified it as an alligatoroid, a member of the crocodilian group that includes alligators and caimans. Details of the jaw bones further narrowed the fossil's identity to a type of animal called Leidyosuchus. Leidyosuchus (whose name means "Leidy's crocodile," in honor of a noted early American paleontologist) was an early alligatoroid, distinguished from modern gators most notably by its more triangular skull in top view. Although the shape of the snout in the Alf Museum specimen suggests it was probably previously unknown species of Leidyosuchus, the researchers decided not to give it a formal name until more complete skull fossils are discovered.

Webb student Sam Woodward '12 (left) and science teacher Kevin Quick at the site of their discovery

The discovery was important for two big reasons:

  1. This is the first time that Leidyosuchus has been definitively identified from the southwestern United States. Previously, undisputed fossils of Leidyosuchus had been found only in Alberta, Canada. Some scientists had labeled isolated teeth from Utah and elsewhere as Leidyosuchus, but because crocodilian teeth are so simple, the isolated specimens could have come from any one of dozens of different species. So, the Alf Museum specimen extends the known geographic range of Leidyosuchus by nearly 1,000 miles!
  2. The Alf Museum's Leidyosuchus is the fifth kind of alligatoroid and the sixth kind of crocodyliform (the group including modern crocs and their extinct relatives) to be identified in the Kaiparowits Formation. This means that 75 million years ago, Utah had more different kinds of crocs living alongside each other than anywhere else in North America. How did this happen? Contrasts in the size and body shapes of the various species suggest they may have lived in different habitats and eaten from different food sources.

Leidyosuchus lived in a rich tropical ecosystem, alongside numerous dinosaurs and other animals (such as the baby Parasaurolophus that recently made international headlines). At that time, southern Utah was much wetter and more densely vegetated, being situated on a low coastal plain. Discoveries by the Alf Museum and other museums have done much to reconstruct this ancient world.

The specimen is currently on exhibit at the Alf Museum, and the full scientific findings were published in the journal PaleoBios. All fossils were collected under permit from the United States Department of the Interior Bureau of Land Management (Utah), in coordination with Grand Staircase-Escalante National Monument (permits UT11-004E-GS and UT06-001S).

Farke, A. A., M. M. Henn, S. J. Woodward, and H. A. Xu. 2014. Leidyosuchus (Crocodylia: Alligatoroidea) from the Upper Cretaceous Kaiparowits Formation (late Campanian) of Utah, USA. PaleoBios 30(3): 72–88. [read article for free]


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