What happened to the Western Interior Seaway?
The Western Interior Seaway was a shallow body of water teeming with extensive marine life. The inhabitants of the Interior Seaway included marine predators such as and that reached lengths of up to 18 meters (59 feet). Other marine species includes,, and the huge -eating (estimated to be 10 meters (33 feet) long); and advanced bony fish such as,, and the 5-metre (16-foot) long, which was larger than any contemporary.
- Other marine organisms included,, squid-like, and others that emitted the chalky platelets that gave the its name.
- The Western Interior Seaway was home to early, such as the flightless, which had thick legs for swimming through water and small wings used for marine steering rather than flight; and the -like, an early avian with a mouth with sharp teeth.
Ichthyornis shared the skies with giants like and. Fossils of Pteranodon are exceedingly frequent; it was likely a key component of the surface ecology, but it was only discovered in the southernmost portions of the Seaway. (bivalve mollusks resembling oysters) were well-adapted to living in the oxygen-poor bottom muck of the ocean.
These organisms left many fossils in the,,, and strata. There is a considerable deal of variation in the shells, and the several diverse species have been dated and may be used to identify particular strata in the sea’s rocky formations. Some species, such as Inoceramus (Haploscapha) grandis, can measure well over a meter in diameter.
However, many species can easily fit in the palm of one’s hand. Sometimes, entire schools of fish sought refuge beneath the giant’s shell. The shells of this genus are comprised of prismatic calcitic crystals that developed perpendicular to the surface, and their fossils frequently preserve a pearlescent sheen.
- Artist’s conception of and two circling a shipwreck in the Western Interior Seaway
- the platyurus at Woodland Park, Colorado
- , an ancient bivalve from South Dakota’s Cretaceous period.
The foothills of the relatively young Rocky Mountains produced a lush shoreline along its western side, while in the lowlands, tropical woods harboured rivers and creeks, marshes and wetlands. The broad sea would have absorbed heat in the summer months and released it in the cooler months, helping to sustain the temperate and humid conditions of the time.
How ancient is the Western Interior Seaway?
02-24-2018 For over a month, I’ve been working on the fossil of an old shark, The shark is in the genus Ptychodus, a term essentially meaning ‘fold teeth’ in Greek. The name stems from the animal’s unusual teeth, adapted for breaking shells rather than shredding flesh like typical shark teeth.
The man I’ve been slowly removing a rock layer from has revealed a bizarre and twisted visage. Two eye sockets are spread on either side of plates of rounded, blunt teeth. The teeth seem to have formerly been organized in tidy rectangles, albeit some of the tooth plates are bent and a few teeth are dispersed throughout the skull.
The complete shark fossil has been flattened and looks as little more than a black etching in a light stone. The body inhabits several shattered pieces of rock laying next to each other on a table. A lengthy column of vertebrae extend back in the same general configuration as in a living shark, except for a couple that have slid out of position, sinking in the center of the back.
Two fins show delicate, hand like cartilage skeletal structures on either side of the body. At the tail there is a strip of delicate glowing skin, but it’s cut short by chunks of rock on each side that simply weren’t recovered at the quarry where the Ptychodus was found. Such is the testament of the Earth’s past.
Broken rock and twisted fossilized skeleton cobbled together with sediment, chemistry, physics, genetics, biology and geology to disclose what we know, what we may know about the planet’s history. Although my specific shark was found in Texas, the species Ptychodus was initially discovered in Kansas.
- Some may think of corn fields, or Dorothy and Toto, and feel that Kansas is an improbable area to encounter a shark.
- But Kansas as we know it now is not even nearly the same place as Kansas of the Late Cretaceous Western Interior Seaway.
- The Western Interior Seaway cut what is now the United States roughly in half.
The whole states of Colorado and Wyoming were truly submerged at one point. The center of Utah and Kansas were on the opposite sides of the sea and much of the south, including all of Texas, was under water. In the modest museum in Hill City South Dakota, linked to Black Hills Institute of Geological Research, I previously worked hangs the skeleton of an enormous turtle.
The turtle is dangling from the ceiling, appearing to swim through the air above your head, staring down attentively, tilted head slightly down. The turtle is a sea turtle and very much resembles living leatherback sea turtle bones. The difference between the turtle in South Dakota of the genus Archelon and current Leatherbacks is largely size and range.
Imagine if the world’s largest known sea turtle was discovered in South Dakota, a highly landlocked state. The biggest Archelon specimen is around 13 feet long and 16 feet broad. Adult leatherback sea turtles measure around 6-7 feet long and weigh approximately 500-1500 pounds.
- Archelon, swam in the same huge inland sea as Ptychodus,
- The sea spanned from the Gulf of Mexico all across Canada into the Arctic seas, the water was 2,500 feet deep at its deepest and home to a zoo of bizarre and exotic species.
- The Western Interior Seaway was also home to Xiphactinus, another species I studied on, the genus bigger (at 18 feet long) than any known bony fish.
Mostly Xiphactinus seems like a regular fish but with protruding, pencil like teeth that might make the impressionable think twice before swimming in the water. Truly bizarre beasts such as the long snake-necked plesiosaurs, looking like sea dragons from folklore swam across the centre of our continent once.
Pterosaurs, including the iconic pterodactyl and swimming birds both fished the Western Interior Seaway. The Western Interior Seaway was subtropical as far north as Wyoming. Partially the climate was warmer because the North American continent has shifted over time but evidence is clear that the whole planet was warmer.
Antarctica wasn’t the fully ice covered freezer we know but was a place dinosaurs could roam. The Western Interior Seaway lasted for around 60 million years, longer than the human race, but all things must come to an end and the last we saw of the seaway was 70 million years ago. 
The National Weather Service’s winter storm warning for today reminded me of some study I conducted a while back regarding Montana’s tropical heritage. So, prepare a cup of something warm, schedule a cross-country ski excursion for this weekend, and envision yourself on Montana’s tropical beaches.
Or, you know, head back to work, whatever you choose. Three hundred fifty million years ago, a warm shallow sea covered the territory of what are today the states of Montana, Idaho, Wyoming and the Dakotas. Actually, the ocean level was so high that much of the western hemisphere was submerged. People who know about such things compare the water that blanketed Montana to the Gulf of Mexico-warm, shallow, and dense with small marine life.
When these animals perished, their remains sunk into the muddy sea bed. Over time (millions and millions of years) their skeletons compacted and metamorphosed into Madison Limestone-the pale gray rock so abundant in Montana, Idaho, Wyoming and the Dakotas.
Limestone is an intriguing substance. On the one hand, it is porous and calcite (the principal element in both limestone and Tums) is relatively simple to dissolve, leading to the production of the amazing formations of the Lewis and Clark Caverns and the numerous caverns that dot Southwest Montana. On the other side, Montana’s dry environment and alkaline soil makes Madison Limestone the most durable rock in Montana.
Most of Montana’s mountains have limestone pinnacles, and most of the cliffs and ridges and most obvious features (such the spectacular canyon along the Clark Fork, or the Beaverhead formation at Dillon) are Madison Limestone. Limestone’s endurance in the Montana environment also means that it has appeared in many of the state’s renowned buildings, such the Montana State Capitol.
