Written by Phil Cerroni
By Derek J. Main, P.hD.
The Arlington Archosaur Site (AAS) begins its 10 year anniversary dig season this spring with an opening dig celebrating Darwin Day followed by a string of busy digs this spring. The AAS will host digs nearly every weekend in March (2, 16, 23 and 30) followed by an equally busy month of digs in April. The AAS spring dig season will end with a celebration of Earth Day on April 20.
The AAS occurs within the Cretaceous (95-100 Million year old) sediments of the Woodbine Formation in Arlington. The sediments of the Woodbine Formation preserve an ancient delta plain swamp environment and coastal ecosystem from a peninsula that projected out into a shallow interior seaway. The ancient North Texas peninsula is called Rudradia. This surprises many North Texans, as the AAS, and its ancient swampland ecosystem lies with a short drive of the ever popular Six Flags and Ranger’s Ballpark. Who would have known that an ancient coastline with giant dinosaurs and prehistoric crocodiles was so close!
The AAS has proven to be an important site to science in that numerous fossils of a primitive herbivorous dinosaur called Protohadros, several carnivorous dinos (theropods), a new turtle, a new species of lungfish and a new giant super-predator croc (& her babies) have all been discovered at the site. These fossils are rare in North America and represent a unique chance to study Cretaceous coastal ecosystems. Our duck billed dino, Protohadros in particular is a transitional species, or "missing link", in the evolution of iguanodonts into hadrosaurs (commonly called duck-billed dinosaurs). In fact all of our fossil animals are dynamic examples of evolution in action! Of equal interest, numerous coprolites (excrement) representing nearly every animal within the ecosystem have been recovered. It is also an interesting site as it is among the few major dinosaur excavations to occur within an urban setting (the DFW Metroplex).
The public are welcome to help with the dig. However, no private fossil collecting is allowed, as all of the fossils found at the site are returned to UTA campus for curation and study. We take adult diggers and work most weekends. We provide the tools and training, it’s fairly simple work, but tedious and requires some heavy lifting (not appropriate for children under 12). We usually begin the day with free geologic tours of the AAS to first time diggers to help them understand what we have found and why. Come out to the AAS this spring and spend an afternoon hiking along the ancient Cretaceous coast.