in 1989, dinosaur tracks were revealed at the Culpeper Stone Company near Stevensville
Source: US Geological Survey, Culpeper East 7.5x7.5 topographic quadrangle (2013)
Various types of dinosaurs have lived in Virginia since that form of life evolved 230-240 million years ago, during the Triassic Period when Virginia was in the center of Pangea. As life refilled the niches, they had the advantage of walking upright, unlike the sprawling gait of salamanders and lizards. Dinosaurs grew fast, an essential characteristic since no Tyrannosaurus rex survived more than 30 years. Their lungs were especially efficient at extracting ocygen and removing heat, like the lungs of modern birds today.
Species with a hip/leg arrangement for walking upright, such as the archosaurs that appeared after the Permian extinction, could move faster on land. Today's alligators and crocodiles are descendants of the pseudosuchian line of archosaurs. Today's birds are the suvivors of the avemetatarsalian line, which also produced the dinosaurs of the Meszoic Era.1
Dinosaurs first appeared in what is now South America, but at the start of the Triassic Period there were no separate continents. The supercontinent of Pangea allowed species on land to migrate without crossing any part of the Panthalassa Ocean.
However, the first dinosaurs were limited to humid areas. Dry areas were a barrier to migration, and Virginia was in the middle of Pangea far from the moist coast. The distribution of dinosaurs was limited by climate and by their inability to exist in deserts. At some point after the first 20 million years of dinosaur evolution, the climate changed and/or the species developed new adaptations that allowed exansion out of the humid tropics. Some dinosaurs managed to migrate into Virginia during the Triassic.2
Only a few dinosaur bones or teeth have ever been discovered on the East Coast of North America, and none have been found (yet) in Virginia. During the "bone war" rivalry of paleontologists Edward Drinker Cope and O. C. Marsh after the Civil War, the focus was on excavating sites west of the Mississippi River.3
Dinosaur fossils have been excavated from iron mining pits in "Dinosaur Alley" between Washington and Baltimore, from Cretaceous clays formed 110 million years ago. There is clearly potential for finding parts of a dinosaur skeleton within Virginia.4
Fortunately, an animal with just one skeleton can create millions of tracks in its lifetime. Those trace fossils have a greater chance of being preserved and discovered, and dinosaur footprints have been found within Virginia.
there are more trace fossils of dinosaur tracks than dinosaur bones
Source: National Park Service, Dinosaur & Plant Fossils
Herds of plant-eating dinosaurs and packs of predators walked across the muddy shorelines on the edge of lakes in Triassic Period basins. Those basins were created as the crust of Pangea cracked and the Atlantic Ocean opened up. In what is now Northern Virginia east of the Blue Ridge, a lake sometimes as much as 60 miles long and 10 miles wide existed for 30 million years. Tracks discovered in Triassic sediments show that other basins near Richmond and Danville were also home to dinosaurs.
There were no flowering plants then; they had not developed yet. At the time when dinosaurs evolved, the day was only 23 hours long. (Since then, the moon has moved further away and the earth spins more slowly.) Monsoons swept across the continent, redistributing heat and moisture. Storms created floods, and floods deposited sediments.
Thousands of feet of rock have eroded off the Blue Ridge over the last 215 million years, filling the Triassic basins in the process. Most of the floods washed away evidence of life, and typically the tracks of dinosaurs disappeared quickly as storms or wind moved sediments around. In addition, 50-70 million years of sediments deposited in the Middle Jurassic-Early Cretaceous have also eroded away, removing whatever evidence they once contained of dinosaurs, ferns, cycads, and the earliest flowering plants.5
Occasionally, the ancient dinosaur trackways have been preserved and exposed later by quarry excavations.
Animals that lived alongside the dinosaurs have been identified from those pits, including Pleurocoelus nanus, Pleurocoelus altus, Priconodon crassus, Allosaurus medius, and Coelurus gracilis. In the District of Columbia, the thighbone of a 10-ton Astrodon (which could reach foliage as high as 33 feet) was excavated from the McMillan water treatment plant. Fossil remains of the Rutiodon phytosaur were found near Dulles Airport and at Solite Quarry near Danville.
In 2012, a vistor to NASA's Goddard Space Flight Center in Maryland discovered a trackway in the Patuxent Formation deposited during the Cretaceous Period. There were 70 footprints from theropods, sauropods, nodosaurs, pterosaurs, and small mammals species. The specific trackway may record the foragers that crossed a muddy area within a period of several hours or days, and the animals that hunted the foragers.6
Tracks remain deeply buried in most cases, but occasionally are exposed. Dinosaur State Park in Connecticut has an extraordinary display of Eubrontes tracks, exposed when the state highway department was constructing a building and preserved because a bulldozer operator quickly recognized that he was about to destroy a rare resource.7
ichnofossils (traces of dinosaurs) were formed 200+ million years ago when dinosaurs stepped on mud
The landscaping at Oak Hill, President Monroe's former home in Loudoun County, was enhanced with new walkways in 1920. Sandstone slabs were excavated from the quarry 3,800 feet north of the house. In those slabs were dinosaur footprints, which are highlighted today in the sidewalks, patios, and floors at Oak Hill.
The tracks of two dinosaur species, Grallator and Eubrontes, are distinctive three-toed footprints Those tracks are trace fossils and not associated with specific bones. Grallator was a meat-eating dinosaur that sprinted on two legs. Eubrontes was a larger predator, reaching 20 feet in length. Until more fossils are discovered, most characteristics of the dinosaurs that made the tracks will remain a mystery.8
Dinosaur tracks have been found in the Richmond, Danville, and Culpeper basins. The most impressive set of fossil footprints discovered so far in Virginia come from the Culpeper Stone Company quarry (now owned by Luck Stone) in Stevensville, near Culpeper. The quarry workers who initially discovered the tracks were not paleontologists, but realized the depressions in the bedrock were significant. As one said:9
Over 4,800 footprints of dinosaurs and other species were preserved on two levels. On a low level of the quarry are 2,300 Kayentapus footprints aligned into twenty trackways. These were made by dinosaurs 10-13 feet long that moved at nearly 20 miles per hour. Kayentapus was a theropod carnivore, probably hunting ornithischians (dinosaurs with bird-like hips) while avoiding other predators that would eat a Kayentapus.10
Analysis of 830 separate footprints at a higher level has revealed 32 separate trackways with six distinctive patterns. The different species thought to have made those tracks are Gregaripus bairdi, Agrestipus hottoni, Apatichnus minor, Anchisauripus parallelus, plus trackmakers Eubrontes and the smaller Grallator. Gregaripus bairdi and Agrestipus hottoni are thought to have been herbivores, while the other four were carnivores.
The tracks were all made within a few days of each other, and the Gregaripus was running at nearly seven miles/hour. Random chance may have favored the retention of more footprints from carnivores, or perhaps they had gathered in large numbers in anticipation of the herbivores migrating though the area.11
dinosaur track from near Aldie
Source: Virginia Geological Survey, The Geology of the Virginia Triassic (Plate 31)
At the Solite Quarry on the Virginia-North Carolina border near Danville, Atreipus footprints are associated with a particular 10-million year period in the Late Triassic. Near Manassas, Apatopus, Brachuchirotherium, Chirotherium, and Grallator tracks have been documented.12
Along the Rappahannock River, a research geologist and amateur paleontologist recognized that the local Cretaceous sediments in Spotsylvania County should contain trace fossils. After using a boat to explore the riverbank, they found tracks of the herbivore Sauroposeidon, which grew to 70 feet in length. A footprint preserved in stone was 3-feet by 1.5-feet in size.
They also found footprints of Iguanadont, Hypsilophodont, Archaeornithomimus, Priconodon, Eolambia, and Irenesauripus, plus non-dinosaur species.13
Tyrannosaurus rex is the most famous dinosaur species. The tyrannosaur group existed for 100 million years, starting in the Middle Jurassic. They had colored feathers for display to attract mates and warn competitors.
Starting 84-80 million years ago, some tyrannosaurs evolved into the large, unrivaled predators highlighted in so many dinosaur exhbits and movies. A Tyrannosaurus rex ate 250 pounds of meat daily. It had teeth and jaws so powerful that it is hardest-biting terrestrial animal of all time. It was the only dinosaur whose teeth could puncture through the bones of its prey.
If a moviemaker shows a Tyrannosaurus rex biting through a car, that scene would reflect the actual capability of the top predator species. It could move up to 25 miles per hour for a brief chase, typically hunting in packs and ambushing prey with a short burst of energy. An assessment of intelligence known as the encephalization quotient, based on the ratio of the size of the brain to the size of the entire animal, suggests the Tyrannosaurus rex was as smart as modern chimpanzees.
Tyrannosaurus rex, like many species of dinosaurs, had feathers 66 million years ago. They were used for display and controlling body temperature, but some species of dinosaurs at that time were also flying with feathered wings.
When the Tyrannosaurus rex species evolved 68 million years ago, it emerged first in China. It expanded its range and migrated across the Bering Land Bridge, which was possible because the breakup of Pangea had not separated Asia and North America yet. Tyrannosaurus rex immigrated from to western North America, but no one has found evidence of it in Virginia.14
The migration of Tyrannosaurus rex to Eastern North America was blocked by the Western Interior Seaway. High water levels in the Cretaceous Period flooded the middle of the continent. The Arctic Ocean and the Gulf of Mexico were connected, separating Laramidia from Appalachia. Dinosaur species developed independently on the separate sides of the seaway.15
the Western Interior Seaway separated Virginia from Laramidia, the territory of Tyrannosaurus rex after it arrived during the Cretaceous Period
Source: US Geological Survey, New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism (published in PLOS One, September 22, 2010)
Almost all of the dinosaurs died out in Virginia and across the world after a catastrophic meteorite/comet impact 66 million years ago in the Gulf of Mexico. In Virginia, all the dinosaurs not within underground burrows died in one brief period, the same day of the impact which formed the Chicxulub crater now located at the edge of the Yucatan peninsula.
The impact immediately blasted steam and molten rock high into the atmosphere. A cloud of gas and particles quickly spread outward in all directions, and air currents at high altitude carried the cloud around the world. No place was safe or unaffected. When incandescent shards of rock fell back to the surface, the atmosphere at ground level was heated to the temperature of a modern pizza oven.
All wildlife and plants exposed on the surface were pelted by the hot particles. They ignited organic material directly, and the hot, hot air set every grassland and forest on fire. In what is now Virginia, it is likely that every animal and every plant that was not in a burrow or water was baked or burned to death. Black ash covered the earth's surface at the end of that dramatic day. Once-blue lakes and streams were grey with suspended soot, or black with a floating cover of once-green plants.
That same day, earthquakes exceeding anything experienced in modern times rocked the land. Winds from the blast wave and the atmospheric heating exceeded the force of hurricanes and blasted the scorched landscape.
A massive amount of water was displaced by the initial meteorite/comet impact. Ocean current patterns were disrupted again by the fast return of water into impact crater, which was briefly empty after the heat of collision caused a column of the ocean to flash into steam. The disruption at the impact site triggered tsunamis. One perhaps 50 feet high swept inland from the Atlantic Ocean, sweeping away the ash and whatever charred remains of dead dinosaurs were still on the surface.
the impact event that killed off the dinosaurs occurred about 1,200 miles from Virginia (red square), but the location of shorelines and tectonic plates was different 66 million years ago
Source: Center for Lunar Science and Exploration, Cretaceous-Teritary (K-T) Boundary (by Jake Bailey, 2000)
After the initial stunning effects, soot remaining in the atmosphere darkened the sky. That blocked sunlight and triggered a period of global cooling. Tiny particles of soot circulated in the atmosphere for months and years.
Raindrops ultimately brought the soot particles to the earth's suface. Those raindrops included sulfur, in part from the vaporized rganic material and in part because the meteorite/comet hit where bedrock was rich in gypsum (CaSO4).
The surfur reacted with the water in the atmoshere, acid rain fell from the skies, and the chemistry of lakes and the ocean shifted. The changes in temperature, acidity, and sunlight were too fast for the species to adapt by gradual evolutionary change. The impact killed 70% of the species on land and in the oceans. The vacated niches were filled by new forms of life as mammals replaced reptiles.
Most individual dinosaurs in Virginia died within one day. Almost all - but not all - dinosaur species disappeared within just a few thousand years.
The only dinosaurs that managed to survive were the birds. The species who survived fed on seeds and carrion, reproduced quickly, and could get through a brief period when photosynthesis was interrupted. Birds are the only descendants of dinosaurs in Virginia today.16
artists speculate on the appearance of dinosaurs, reflecting the discovery of feathers and melanosomes in fossils
Source: Wikipedia, Dino Crisis (serie) (by Salvatore Rabito Alcón)