Clues to Earth’s early inhabitants Top, left; The Stegosaurus was voted the state fossil by Colorado schoolchildren. Top, right; A lifelike replica. Bottom, right; Kids are naturally drawn to the dinosaur sculptures near the visitor center. Bottom, left; The main track site reveals two types of dinosaurs. PHOTOS BY DAVE GIBSON[/caption]

Formed over eons of mountain building process and erosion, Dinosaur Ridge in Golden, Colorado, is sometimes referred to as a hogback because of its resemblance to the spine of a razorback hog. Tilted to an angle of 40 degrees, it was once a coastal plain of the Western Interior Seaway that stretched from the Arctic Ocean to the Gulf of Mexico. The climate was tropical with flowering plants and deciduous trees. In 1936 when Alameda Parkway was built to connect Denver to Red Rocks Park and the planned amphitheater, dinosaur tracks were unearthed in the Dakota sandstone.

The footprints laid down on Dinosaur Ridge’s east side are estimated to be up to 110 million years old from the Mid- Cretaceous Period. Thirty-nine sets of tracks of two different types of dinosaurs have been identified at the main track site. The first were made by duck-billed iguanodon-like ornithopods that grew to be 25-feet long and weighed three tons. Strictly herbivores and gregarious in nature, the exact kind of ornithopod can’t be determined without skeletal evidence. They traveled in small social groups with subadults moving perpendicular to the adults. Six of the trackways are parallel to one another. The other tracks are from birdlike ostrich-sized ornithomimids whose fossilized prints show no particular order. A few crocodilian footprints may also be seen.

More prehistoric clues are on display on either side of the main track site in the way of trace fossils. Trails and burrows of invertebrates such as worms and mollusks are preserved. Visible are impressions of plants, roots, driftwood and scrapes where mating ornithomimids clawed the ground in a courtship ritual seen in birds today. Ripples formed in the once sandy seafloor are frozen in time.

The farther west you travel on Alameda Parkway, the further you go back in time. A vast floodplain dominated the landscape filled with conifers, ferns, and cycads in the Late-Jurassic Period 150 million years ago. Unlike during the Cretaceous Period 40 million years later, none of the plants had flowers. For a hands-on experience at the Dinosaur Bone Quarry, you can touch the rib, limb, and pelvic bones of dinosaurs and skull fragments of a stegosaurus embedded in the rock. The bones came to rest in riverbeds and ponds when transported there by seasonal storms which covered them in a layer of mud.

At the Brontosaur Bulges site, foot depressions through a rock stratum are three feet in diameter and one foot deep. They were formed by a sauropod. Species of sauropods include apatosaurus and brontosaurus. Spanning 75 feet in length and weighing 45 tons, they were among the largest creatures to ever roam the Earth.

Located at 16831 Alameda Parkway in Golden, Dinosaur Ridge is open to visitors from 9 a.m. until 5 p.m. daily. You are welcome to walk the 1.5 mile trail unescorted or take the walking tour at a cost of $10. A $28 Dino Pass includes a bus tour, entry into the Exhibit Hall and Morrison Natural History Museum.

For more information about Dinosaur Ridge, go to www.dinoridge.org or call 303-697-3466.