DINING OUT: A herd of Kosmoceratops dinosaurs grazes among the cypress trees 76 million years ago in a primeval swamp in what is now southern Utah.
Image: Illustration by James Gurney
In Brief
- Between 90 million and 70 million years ago, during the Late Cretaceous period, a shallow sea flooded the central region of North America, subdividing the continent into eastern and western landmasses. Scientists refer to the western landmass as Laramidia.
- In the 1980s a researcher proposed that distinct dinosaur communities inhabited the northern and southern regions of Laramidia for several million years. Critics doubted that so many large animals could have shared this relatively small chunk of land, however.
- But over the past decade discoveries in southern Utah have bolstered the notion of distinct dinosaur communities in the north and south, revealing a host of species new to science—including many giant varieties.
- Exactly what enabled so many behemoths to coexist in such a small area remains unclear, but it may be that dinosaurs had lower energy requirements than today’s large terrestrial animals do or that plants during the Late Cretaceous provided more food than their modern-day counterparts.
More In This Article
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Overview
Illustrating the Lost Continent
On a cool September morning in 2010 my crew and I began our daily descent from camp back into deep time, walking single file down a steep, knife-edge ridge of sandstone and mudstone in southern Utah’s Grand Staircase-Escalante National Monument. Each of us carried water, a field notebook, lunch, a rock hammer and other hand tools. Heavier tools and materials—rock saws, picks, shovels, bags of plaster and swaths of burlap—awaited us half a mile away at the dig site. Even from the hilltop we could easily see the plaster jackets down in the quarry—alabaster beacons in a wilderness of arid, gray-striped badlands. Some of the irregular lumps were not much bigger than a loaf of bread. Others spanned 10 feet and tipped the scales at more than a ton. All contained the bony remains of animals that coexisted here 76 million years ago.
Over the course of two field seasons this single quarry—one of many in the fossil-rich rocks of the Kaiparowits Formation—had yielded a striking array of creatures, including several dinosaurs. Most impressive was a largely complete skeleton of Gryposaurus, a massive, duck-billed plant eater approaching the size of Tyrannosaurus. The crew was now under pressure to finish excavating the remaining fossils before the helicopter came in a few days to airlift the priceless cargo to a nearby road. From there the fossils would travel by truck to the Natural History Museum of Utah in Salt Lake City, where trained volunteers would painstakingly open the jackets, remove the rock and glue the bones back together over a period of months.
This article was originally published with the title Dinosaurs of the Lost Continent.
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10 Comments
Add CommentThe question of how so many species of large dinosaurs could exist in a relatively small land area compared to large mammals is most likely related to the environmental and/or their physiological differences that enabled them to grow so large in the first place.
Reply | Report Abuse | Link to thisOne key difference I didn't see mentioned is the dinosaur's advanced flow-through air sac respiratory system - like those of today's birds that allow them to expend so much energy for long periods.
Also, does the discovery of fossils of several species indicate any actual number of animals that coterminously existed in a region? As I understand, fossils are produced only in very specific conditions and may not represent a statistically valid sampling of a population. Perhaps the actual numbers of large dinosaurs in the region were less than envisioned...
The energy requirements of dinosaurs during this period were very low due to lowered surface gravitation. Lowest gravitation ~200 Ma and gradually increased to ~67 Ma when it rapidly increased. This is why the dinosaurs became extinct (except the avian dinosaurs.) The asteroid impact had little effect in terms of extinction.
Reply | Report Abuse | Link to thisThis is all explained at www.dinoextinct.com, click on 'The Gravity Theory of Mass Extinction' to view a PDF summary of the theory.
The most productive natural ecosystem on the face of the earth is a mangrove swamp. While other swamps are not as productive, they can still be extremely productive ecosystems. Fast growing swamp plants can support more grazing animals than dry land plants.
Reply | Report Abuse | Link to thisThe artist's picture should probably show a picture of the dinosaur in the swamp munching on a fast growing sedge. Simply because the Cypress Tree left a fossil, does not prove it was the most common plant in the swamp.
I read this article and got the point about the problem of two distinct dinosaur faunas living on Laramidia or western NAM in Campanian epoch. There was passing mention of a barrier separating the northern and southern fauna, but no discussion. There was a large igneous province in what is now Idaho and Montana which is associated with the Idaho Batholith whose youngest dates fall into the time window. This coincides with the deposition of a large clastic wedge that thins to the east and covered most of the two states. This geology might have created a biogeographic barrier.
Reply | Report Abuse | Link to thisI know I am usually serious but they probably did not have political parties and there was enough prey for predators and mixed taste. In Africa today there are many different prey species that attack and feed from the same prey group in fact they often collide over ownership with might usually making right. But might comes in several flavors that include stealth, placement of the carcass, numbers of predators etc. A leopard usually hides the prey in a tree, hyenas will try to bring enough of their own to overwhelm a lion pride and the cheetah just has to eat really really fast.
Reply | Report Abuse | Link to thisWhat is always interesting is when the prey bite back such as water buffalo groups and I picture a group of triceratops acting in a group self defense strategy. Duckbills probably used their unique sound abilities to create a range of calls to identify what type of predator was coming or discovered.
I haven't even touched the pterosaurs and attacks from the sky but I imagine most large kills back then took some semblance of kills on the African Savannah today with each type coming for its piece of the pie.
Even in places such as Yellowstone you can see similar predator prey issues with the wolves, bear, coyotes, foxes and badgers all making do with whatever opportunity is available. As long as an ecosystem is made of competing feed back systems multiple prey and predator relationships can exist. That is why we need to pay attention to the way we sprawl, slash and burn and overburden the sea. We are removing the connectivity required to support multiple systems and that may allow for a crash based on simple asymmetric math principles.
When we discover a dinosaur that killed for fun and was able to prolifically do this with no control, we may then have an alternative to the asteroid extinction theory. Until then I go with asteroids, earth quakes and volcanoes created by the initial shock of said impact.
Jim, the best reason put forth on the large size of the dinosaurs so far is the abundance of O2. I think the amount was around 23% compared to the 20% today. Also reptiles will continue to grow as they age and this characteristic may have carried over even as they became warm blooded.
Reply | Report Abuse | Link to thisAnother factor regarding the larger plant eaters was the need of extremely large digestive systems to get nutrition out of the plant material they subsisted on. Some of the stomach projections on the Sauropods was close to the size of a small car.
One thing I have not seen much research on is if the predators hopped more than walked. Looking at the leg and arm relations of the predators and the anatomy of the marsupials in Australia it seems natural to think that hopping would be a better means of moving. They also had large, long tails that would have been required to stabilize jumping. My take is they would get a much bigger bang for the buck and the speed they could attain would be impressive, especially for a predator.
Yes, thanks. To put another way, the issue of "what enabled so many behemoths to coexist in such a small area" compared to "today’s large terrestrial animals" is likely the same differences in environmental conditions between the two eras and/or physiological differences between dinosaurs and modern mammals.
Reply | Report Abuse | Link to thisWikipedia says that, on average, the Cretaceous period CO2 levels were 6 times preindustrial levels, while O2 was 1.5 times current levels. The greater oxygen levels combined with more efficient respiration would increase dinosaurs' energy levels, while the much greater carnbon dioxide levels should have produced more plant material.
In these conditions, the a relatively small region of productive vegetation should be able to sustain a larger population of large, active dinosaurs than a region of similar size can today sustain large mammals.
Interesting idea about at least some of the bipedal dinosaurs jumping - there might be some evidence in preserved tracks...
2 things.
Reply | Report Abuse | Link to this1) Oxygen levels are not enough to explain the enormous bodies their muscle and bone had to support. Gravity must have been a fraction of today's level.
2) Fossils are formed by catastrophic events and so could be associsted with large water movements. Corpses can be carried miles from their origin. The idea of dinos falling down dead and being preserved where they lay is nonsensical. Unless they were immediately covered by vast amounts of mud/ sand/tar etc, and then superheated to prevent disintegration they just disappear by natural processes.
2 things.
Reply | Report Abuse | Link to this1) Oxygen levels are not enough to explain the enormous bodies their muscle and bone had to support. Gravity must have been a fraction of today's level.
2) Fossils are formed by catastrophic events and so could be associsted with large water movements. Corpses can be carried miles from their origin. The idea of dinos falling down dead and being preserved where they lay is nonsensical. Unless they were immediately covered by vast amounts of mud/ sand/tar etc, and then superheated to prevent disintegration they just disappear by natural processes.
Many dinosaurs' bones (including large sauropods) were hollow and used in their air-sac respiratory system.
Reply | Report Abuse | Link to thisThe hollow vertebra in sauropods long neck allowed them to lift their heads off the ground without requiring any decrease in Earth's gravity.