What Did Westchester Look Like During the Age of the Dinosaurs?

Let's call it Jurassic Park-Chester.


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A pack of Coelophysis hunting in what is now the Hudson Valley.

Illustration by corey ford/istock

The midday sun, directly overhead the equatorial region of the great land mass Pangea, sears the warm and forbidding land. A creature leaves the herd and scurries across the edge of a marsh to find cover behind a fern. It waits, perched on three birdlike toes supporting its hind legs. She is not a bird, though; she is a lizard, standing three feet tall at the hips but, leaning forward, spanning nearly 10 feet from nose to tail. She is looking to add to her 40-pound frame. She is looking for lunch.

Other beasts are grazing nearby, on the fruit and leaves of the cycads and other tropical plants that forest the region. But our creature wants meat. When a small, furry animal — rodent-ish but not a rodent — pops out of its nest, she snaps it up in her long, powerful jaws, crunches it easily and speeds off gracefully to rejoin the herd. She leaves behind nothing but footprints in that marshy mud slowly drying under the deep sky, which is growing fantastically orange and red behind the setting afternoon sun.

Two hundred-plus million years, thousands of miles in latitude and longitude and unfathomable differences from the world in which they were left, those very footprints — or, at least, some like them — will be found in an unexpected place: Nyack Beach State Park, in Haverstraw, Rockland County. These tracks, and the relatively few other clues left in our geologic neighborhood from the Mesozoic Era, tell us what the Hudson Valley was like during the age of the dinosaurs.

Saltasaurus, shown to scale along present-day Mamaroneck Avenue in White Plains.

The first dinosaur fossils found in New York State, these footprints were discovered in 1972. Imprinted in slabs of rock that now belong to the New York State Museum, in Albany, the footprints belong to a type of lizard known as a Grallator. Our beast was probably coelophysis, a slender, bipedal carnivore that lived throughout the east coast of what we call North America. It’s also found in other parts of the world, because back then, there was no North America. There was no New York, no Hudson River, no Westchester or Rockland or Albany Counties. There was only Pangea.

 

Triassic Tarrytown

Two hundred forty-eight million years is, when you think about it, unthinkable. As a species, we humans haven’t made it anywhere close to 1 million years yet. The land on which we now live has drifted and changed, been uplifted, folded, submerged, frozen, and melted countless times since the Mesozoic Era began those 248 million years ago. At the beginning of that time, called the Triassic period, the continents were all connected as one giant land mass that stretched from pole to pole. Determined creatures could cover the entire land mass of Earth — and they did, which is why similar fossils are found in Nyack and in Mongolia and Australia.

Our region, though, is rather fossil-poor. Substrata of dirt and rocks from large portions of the Mesozoic simply don’t exist in most of the Hudson Valley, because of all that drifting, uplifting, folding, and submerging. Better records of our dinosaur past have been found in Connecticut, New Jersey,  and down the eastern seaboard, though, and scientists believe we can infer that, if those forms of life lived in Hartford or Newark or Baltimore, they likely lived in White Plains and Chatham, too.

If, back then, someone had put a GPS transponder at the future location of, say, The Westchester, it would have pinged at about 10 degrees north latitude, the same parallel as Costa Rica. We can’t know what longitude, but it was probably somewhere in the middle of what is now the Atlantic Ocean, except that there was no Atlantic Ocean, only Pangea and a great global ocean called Panthalassa. North America and Eurasia were mashed together, and that mashing had created enormous mountain ranges where they collided — what is now Connecticut, in fact, boasted peaks as high as Mount Everest, and the Ramapo Mountains were legitimate mountains back then. That the highest point in Westchester today is 980 feet, and that Connecticut’s elevation today tops out at about 2,400 feet and is now known for its lovely, gentle, rolling hills, shows what 200 million years of weathering can do.

(L to R): Eubrontes giganteus track from Riker Hill Fossil site in Livingston, NJ; tracks from Dinosaur State Park in Rocky Hill, CT.

The climate was much warmer, with no polar ice and higher sea levels. At the beginning of the era, life was limited. Earth had just come out of the Permian Extinction, the   largest mass extinction known. For unclear reasons, more than 90 percent of the planet’s life forms vanished. It took much of the Triassic, which lasted about 50 million years, for life to return.

It was during this time that the continents began to pull apart; in our neck of the woods, that occurred somewhere along the New Jersey Turnpike. Rift valleys ran all the way from Greenland to South America, and as North America pulled away, one of the rifts came to be called the Newark Basin. “The center was somewhere near the New Jersey-Pennsylvania border,” says Paul Olsen, the man who found those dinosaur tracks at Nyack Beach, now the Arthur D. Storke Professor of Earth & Environmental Sciences at Columbia University. “There would have been a broad lake in Rockland-Westchester, running south to Maryland and Virginia. Westchester would probably have been on its eastern shore.” As a basin, our land would periodically fill and drain. “It would have been a mud flat, with fringe vegetation, surrounded by islands,” Olsen says.

Fossil of Eurypterus remipes — the official state fossil of New York.

Over the next 50,000 millennia, continental separation continued. The atmosphere contained carbon dioxide at concentrations that were two to three times as high as they are now. But that was just fine for the few small dinosaurs, other reptiles similar to crocodiles called phytosaurs, and, in Olsen’s precise scientific phrasing, “many bizarre creatures” that came to inhabit the lands. Plants like cycads, conifers, and horsetail rushes grew abundantly, but there were no flowering plants — or bees or butterflies to pollinate them — just yet. Though no insect remains have been found near here, many that look very much like modern flies, beetles, bugs, and dragonflies have been found in North Carolina. Our earliest ancestors were here, as well. These creatures, called synapsids, are also known as “mammal-like lizards,” which means they are “not like anything we can compare it to,” says Carl Mehling, a senior scientific assistant in the Division of Paleontology at the American Museum of Natural History. “They were quadrupeds but probably had no fur.”

The skies were also populated by creatures like Icarosaurus, a small lizard that could glide using “wings” — elongated ribs covered with skin and shaped like an airplane wing to create lift. (The only known Icarosaurus fossil skeleton was found in North Bergen, NJ.) The waters were home to lots of fishy creatures — “the most common were the coelacanths, related to gars, and others, like sturgeons and clams,” Olsen says. “But be careful. Croc-like phytosaurs would leap out of the water and grab you,” he warns. They likely feasted on small, gopher- or shrew-like early mammals, or on the larger dicynodont, “a Volkswagen-shaped mammal that was probably dumb as a brick,” he says.

Hudson Valley Critters Throughout the Ages

The dinosaurs and their peers roamed this land from about 230 million years ago to about 65 million years ago. As unimaginably long as that may seem, it is just a fleeting moment in geological time. Using the familiar 24-hour clock analogy, if the earth’s forming 4.6 billion years ago is considered midnight, the dinosaurs didn’t appear until almost 11 p.m. What else lived in what is now the Hudson Valley before us human newbies arrived just one minute ago, at 11:59 p.m.?

BD: Before dinosaurs

For the first 3.5 billion years, life on earth was tiny and tenuous. From about 400 million to 300 million years ago, our land was underwater, drifting north toward the equator from somewhere near the South Pole. Invertebrates, such as trilobites (relatives of horseshoe crabs), brachiopods (early mollusks), cephalopods (ancestors of squids), Tentaculites (conical, carrot-shaped organisms), and coral were abundant. And Eurypterus, a giant sea scorpion that could grow up to four feet long and was one of the most fearsome predators in the sea before proto-sharks arrived on the scene, is New York State’s official fossil. Fossils of these long-gone creatures have been found at John Boyd Thacher State Park in Albany County, along Route 209 from Kingston to Stroudsburg, PA, and at Highland Mills.

AD: After dinosaurs

For 64 million years following the great extinction of the dinosaurs and much of life on earth, the region was warm, moist and conducive to the evolution of many of the plants and animals we see today (and more than a few we don’t see anymore). Creatures like mammoths, mastodons, giant beavers and sloths, musk oxen, and the giant short-faced bear roamed the land. Over the past two million years, though, periodic ice ages brought glaciers that covered the state and then retreated, each time reshaping the landscape, carving rivers and lakes and mountains and killing off many of these animals. The mastodon, though, was probably still around when the earliest humans arrived here, about 13,000 years ago; the famous Cohoes Mastodon skeleton, found in 1866 near the Cohoes Falls, has been dated to about that time.

 

Jurassic Jefferson  Valley

Another mass extinction, about 206 million years ago, killed off half of all land species, ended the Triassic and launched the Jurassic. The leading explanation for this, Olsen says, is massive explosions of lava from fissures in the earth that buried about 11 million square kilometers. “We were covered in lava, from France to South America,” he says, because the lands were still very close together. Carbon dioxide and sulfur gases were doubled, which likely was the real cause of the extinctions. The gas and smoke from these eruptions probably caused some spectacular sunsets, Olsen says. The Hudson Valley, and the rest of planet Earth, was no place to be back then, unless you were a dinosaur.

Mesozoic means “middle animal,” and for the next 150 million years or so, dinosaurs thrived. The climate was hot and dry at first, then warm and moist. More and bigger dinosaurs roamed the earth, and a few, like pterosaurs and Archaeopteryx, believed to be a bird-like dinosaur hybrid, filled the skies. Therapods, fierce and superb hunters, seemed to like our location, as evidenced by the hundreds of footprints and trackways found in what is now Walter Kidde Park in Roseland, NJ, west of Newark, and in Rocky Hill, CT, near Hartford, where they are now visible again, at Dinosaur State Park.

Most scientists think that the track- makers there were similar in size and shape to Dilophosaurus, a 20-foot long, half-ton beast, says Meg Enkler, Environmental Education Coordinator at the park. “There was a large lake here, surrounded by mudflat — ideal conditions to preserve footprints — with high mountains to the east and west,” she says. “We have mammal tracks from rodent-type creatures, ginkos, magnolias, different and unusual conifers, but no flowers yet.”

corey ford/istock

Growing to 20 feet in length and weighing up to a half-ton, the Dilophosaurus likely dominated our region during the Mesozoic era.

The lake, and others like it up and down our eastern shore, were caused by the continued rifting of North America from Africa. “The rift basins just got bigger and bigger, would rupture, be covered with lava, then sink,” Olsen says. “And the sea crept in.” We were underwater for large periods of time. By the middle of the Jurassic, the Atlantic Ocean began to take form, and by the end, 145 million years ago, it was hundreds of miles wide.

By now, we are up to about 25 degrees north latitude — where the Florida Keys currently bask. The Ramapos were still real mountains, and may have produced rain, but otherwise the area was mostly arid. With more rifting during the Jurassic and greater intrusion of the ocean, and with the continental drift north through the subtropics, the landscape would have picked up a greater amount of conifer and fern forest, says Keith Landa, director of the Teaching, Learning, and Technology Center at Purchase College. “Shallow tropical seas in the region would have helped make a ‘nicer’ climate. On the other hand, the episodes of volcanic activity in the area due to the rifting would have resulted in periods of pretty nasty conditions.” The lava flowing out of fissures extended throughout the length of the rift valleys, with the release of carbon dioxide, steam, sulfur dioxide, and other noxious gasses. “These episodes would have had a major impact on regional habitability,” Landa says, and not in a good way. In Connecticut, three major episodes of volcanisms during the Mesozoic have been discovered.

Other creatures of the time found in our region include three prosauropod dinosaur skeletons from the Early Jurassic, which were found in Manchester, CT. These plant-eaters, some of the largest dinosaurs of their day, were up to 30 feet long from tiny head to tail and could rise up on hind legs to munch on leaves and fruits 13 feet above the ground.

Icons designed by Freepik from Flaticon

Cretaceous Catskill

The third Mesozoic period, the Cretaceous, lasted from 146 million to 65 million years ago. This was the golden age of dinosaurs; nearly half of all the dinosaurs we know about lived during the last 15 million years of the Cretaceous period.

Pangea has broken into two large continents, and we are drifting toward our current global destination. The land is lower, and the seas are encroaching Westchester and Rockland. “Most of the time it’s underwater or on the shoreline,” Olsen says. There are no sediments from this period found in the area, but our neighbors give clues to what it was probably like.

In fact, the first nearly complete dinosaur skeleton in the world was found in Haddonfield, NJ, in 1858. Sediments from the Cretaceous period revealed a 75-million-year-old fossil of a Hadrosaurus foulkii, the first known duck-billed dinosaur, which have become the most plentiful dinosaur finds from this period on the East Coast. Hadrosaurs had long tails to balance the front of their body as they sped across the land at speeds of 10 miles an hour up to — when being chased by a hungry adversary — perhaps 30 miles an hour. (In 1991, Hadrosaurus was named the official New Jersey State Dinosaur.) Ellisdale, NJ, has also produced numerous late Cretaceous fossils, including specimens of giant dinosaurs like Dryptosaurus, a tyrannosaur sixfeet tall at the hip that may be a cousin of the fearsome T Rex; Hypsibema, which had about 1,000 small teeth, weighed up to four tons and spanned 30-plus feet from duck-billed head to tail; and even body-armored dinosaurs with clubs on their tails. Out in the growing ocean, giant marine lizards with long necks prowled the shores; “They looked like the Loch Ness monster,” Mehling says. There were crocs off the coast of New Jersey that look like they do today. “And,” Olsen adds, “a giant turtle called Archelon lived around here, the largest sea turtle ever documented, 16 feet wide from flipper to flipper.”

During the 80 million years that the Cretaceous period lasted — longer than the time it has taken to get to today — temperatures were higher than ever before or since, then cooled somewhat toward the end of the era. By about 65 million years ago, most of the continents were separated; India was drifting at sea, though Australia was still part of Antarctica, which was forested rather than frozen and well populated by the creatures of “middle life.” While more volcanic eruptions were poisoning the atmosphere and making things difficult, all in all, life was good. Until it wasn’t.

 

When is a dinosaur not a dinosaur?

About 450 million years ago, the “Hudson Valley” was part of a submerged continental shelf in the subtropical region of the Southern Hemisphere. Shifting land masses and sediment, overrun with sand, clay and volcanic deposits called turbidity, left a pattern of wrinkled, flowing formations that have come to be known as “dinosaur skin outcropping.” These are found at, among other places, Coxsackie in Greene County. But dinosaurs didn’t appear for another 300 million years, so don’t be fooled. This skin is just interesting rock.

 

The End of an Era

The midday sun, low in the sky as the temperate land mass known as North America settles into winter, gently warms the subtropical landscape. A menagerie of strange beasts on the ground, in the water and in the air, live harmoniously, as they have for 180 million years.

A streak of light glows faintly in the firmament, then grows brighter, then impossibly bright. The creatures raise their scaly or thorny or furry or feathered heads in wonder. The streak arcs across the sky. Sonic booms shake the land. The streak disappears over the horizon. Then, the entire planet shudders and quakes and rends apart. Firestorms engulf the globe. Tsunamis flood every coast on Earth, including the northeast coast of our continent, and drown everything for hundreds of miles inland. Acid rain burns the landscape, and layers of sediment containing iridium, a rare metal on Earth but common in meteorites, covers the ground from pole to pole. Darkness from this “impact winter” cloaks the globe, and within mere geologic moments, three-fourths of all life, including every living thing over about 20 pounds, becomes extinct. It is a very bad day. The Hudson Valley, and the rest of planet Earth, was no place to be back then.

Unless you were a mammal.

 

 

 

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