Return to Down’s Quarry

This is our last year at the Down’s Quarry, completing our five year excavation and study of the site. The Down’s Quarry is located in Eastern Arizona about 50 miles south of I-40 along the Arizona/New Mexico border. At this site there are exposures of the Triassic Chinle Formation, which were deposited about 220 million years ago.

Museum Crew working at Down’s Quarry 2013. Photo by Dick Webb.

Appalachian State Crew at Down’s Quarry. Photo by Dick Webb.

At this point I would like to show you some of the past field images and some of the material which we have so far prepared and catalogued. We have found the remains of a number of early archosaurs; crocodilian–like animals. Included in these are the aetosaurs, Desmatosuchus and Calyptosaurus, and also the remains of a number of phytosaurs. Since the body of an aetosaur is completely covered with bony plates, which we call osteoderms, each dead aetosaur could leave hundreds of osteoderms, and these are the main fossils which we recover. It seems almost everywhere you dig, you uncover another osteoderm: it’s osteoderms all the way down.

Desmatosuchus specimen on exhibit at Petrified National Forest.

Desmatosuchus fossils from Down’s Quarry.

Phytosaur fossils from Down’s Quarry.

Phytosaur skull from exhibit at New Mexico Museum of Natural History. Photo by Paul Brinkman.

About as abundant as osteoderms are coprolites; these are the fossil fecal remains of animals: their dung. However, between these osteoderms and coprolites, we have uncovered a number of limb bones, vertebrae, teeth, and skull bones. As a result of these osteoderms and the other fossils we are starting to get a better picture of life during the Late Triassic.

Coprolites from Down’s Quarry.

The dicynodont, Placerias, for whom the quarry was originally named, has also produced a number of bones, but not as many as we expected to find. There are a lot of questions we could answer about Placerias if we could discover a complete pelvis. We hope we will find one this season.

Placerias skeleton on exhibit at New Mexico Museum of Natural History. Photo by Paul Brinkman.

Placerias fossils from Down’s Quarry.

We have also uncovered several fossils from the temnospondyl amphibians called metoposaurs.   These were huge amphibians with heads up to 2½ feet long and bodies up to 8 feet long.

Temnospondyl fossils from Down’s Quarry.

The field jackets we prepare in the quarry (for safe transport of the bones back to the museum) also contain a lot of the surrounding sediment. Back in the lab we process this sediment by washing it through screens to reveal a good number of microfossils. These include teeth, limb bones, vertebrae, and scales of a variety of fishes, amphibians, reptiles and pre-mammals.

You would think that in the four years since we began this project we could prepare all the fossils which we collected in about 8-9 weeks over those four field seasons. It just does not work out that way. We still have a significant backlog of material waiting for preparation in the lab.

Plaster jackets from Down’s Quarry awaiting preparation.

Advertisement