The Western Interior Cretaceous Seaway

Between 70 and 100 million years ago, much of central North America was covered in a shallow, inland sea known as the Western Interior Cretaceous Seaway.  While the ancestors of Tyrannosaurus and Triceratops roamed the fragmented continent, an amazing array of fascinating marine reptiles prowled through the waves.  Sea turtles the size of a small car, long-necked plesiosaurs, and fifty foot long relatives of the Komodo dragon.  Check out the documentary by clicking on the link below!

The first stop in the documentary is to visit Dinosaur Ridge, a very exciting fossil site just a few minutes drive from where I live in Colorado.  Dinosaur Ridge has a number of very interesting points of geological and paleontological interest, but the portion of the ridge that we visit in the documentary are the fossil dinosaur trackways on the eastern side of the ridge.  Here, just before the area was completely inundated by the seaway, a number of different dinosaurs (paleontologists believe some sort of large, iguanodont-like ornithopod; an ostrich-like ornithomimosaur; and a large Acrocanthosaurus-like theropod) left their footprints in the once-squishy beach sand.  In other, nearby rock layers, we can find the remains of lithified ripple marks, showing exactly where the waves would lap gently at the shore.

Fossil dinosaur trackways preserved at Dinosaur Ridge in Colorado ornithopod theropod and ornithomimosaur tracks from the Early Cretaceous on the shores of the Western Interior Seaway Photo Credit Zack Neher

Fossil dinosaur trackways preserved at Dinosaur Ridge in Morrison, Colorado.  The majority of the footprints are thought to belong to some sort of ornithopod dinosaur like the famous Iguanodon, although some are attributed to an ornithomimosaur, and others to a large, Acrocanthosaurus-like theropod.  Crocodilian tracks are also reported.

Lithified petrified ripple marks from the shore of the ancient Western Interior Cretaceous Seaway preserved at Dinosaur Ridge in Colorado Photo Credit Zack Neher

Petrified ripple marks from the shore of the ancient Western Interior Cretaceous Seaway, preserved at Dinosaur Ridge.

Zoomed in lithified petrified ripple marks from the shore of the ancient Western Interior Cretaceous Seaway preserved at Dinosaur Ridge in Colorado Photo Credit Zack Neher

 

A mounted skeleton of the theropod dinosaur Acrocanthosaurus at the Houston Museum of Natural Science in Texas with Cian Kinderman Photo Credit Zack Neher

A mounted skeleton of the theropod dinosaur Acrocanthosaurus, on display at the Houston Museum of Natural Science in Texas.  This dinosaur gets its name from the enormous, elongate neural spines running down its back, which would have made the animal look much larger and more intimidating than a relative without them.

Next, I visited Doug Hartshorn, the Museum Coordinator at the Morrison Natural History Museum, so that he could tell us more about some of the Western Interior Seaway’s inhabitants.  He told us about the mosasaurs, such as Tylosaurus, and the Pteranodon, a species of pterosaur, a group of winged reptiles that were closely related to dinosaurs.

Mounted skeleton of the mosasaur Tylosaurus on display at the Houston Museum of Natural Science in Texas with Cian Kinderman Photo Credit Zack Neher

Mounted skeleton of the mosasaur Tylosaurus on display at the Houston Museum of Natural Science in Texas.  Tylosaurus and the other mosasaurs were not dinosaurs, and in fact were close cousins of modern day monitor lizards, such as the Komodo dragon (Varanus komodoensis).  In this shot, you have an excellent view of the pterygoid teeth, situated on the roof of the mouth of the animal.  These twin rows of teeth could be used like a conveyor belt, to pull prey back into the belly of the beast.

Zach Evens and Zack Neher for scale next to a mounted skull of the mosasaur Tylosaurus at the Morrison Natural History Museum in Colorado with Masaki Kleinkopf Photo Credit Mona Kamath

My friend Zach Evens and I next to the Tylosaurus skull at the Morrison Natural History Museum in Colorado.  Although Tylosaurus, one of the biggest members of the group, could grow up to fifty feet long, this is still much smaller than the monster-sized mosasaur featured in the movie “Jurassic World.”  Photo Credit: Mona Kamath

Mounted skeletons of the sea turtle Toxochelys and the mosasaur Plioplatecarpus on display at the Houston Museum of Natural Science in Texas with Cian Kinderman Photo Credit Zack Neher

Mounted skeletons of the sea turtle Toxochelys and the mosasaur Plioplatecarpus, on display at the Houston Museum of Natural Science in Texas.  Toxochelys, the most common sea turtle in the Western Interior Seaway, had evolved a bite that was perfectly adapted to consume hard-bodied prey, such as clams and ammonites.

Dumeril's monitor lizard Varanus dumerilii attacks a plastic Megalodon like in Jurassic World at the Morrison Natural History Museum in Colorado Photo Credit Zack Neher

Herkimer, the Dumeril’s monitor lizard (Varanus dumerilii) at the Morrison Museum attacks a plastic shark as he reenacts his favorite scene from Jurassic World.  Herkimer, like all monitor lizards, is a close relative of the mosasaurs.  The white dot on top of Herkimer’s head (just a little bit behind his eyes) is actually a third eye known as the pineal eye, something that we see on the skull of mosasaurs, as well.

Mounted skeleton of a female Pteranodon on display at the Morrison Natural History Museum in Colorado Photo Credit Zack Neher

Mounted skeleton of a Pteranodon, on display at the Morrison Museum.  Pteranodon is one of a group of flying reptiles called pterosaurs, closely related to dinosaurs and crocodilians.  There appear to be two different morphs of Pteranodon, those with a small crest on their head like that featured here, and those with larger crests, as in the photograph below.  In a classic case of sexual dimorphism, many paleontologists suspect the small-crest morph to be female, and the large-crest morph to be the male.

Masaki Kleinkopf next to a mounted skeleton of Pteranodon sternbergi on display at the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado Photo Credit Zack Neher

The large-crest morph of Pteranodon, most likely the male, with my friend Masaki Kleinkopf for scale.  Scale is important for these animals, as many of them are a good deal larger than any flying animals we have alive today.  Modern albatross have the largest wingspan of any flying creature today, somewhere around eleven feet wide.  An good-sized Pteranodon would have a wingspan much wider than that, and some other pterosaurs grew even bigger still.  This cast is on display at the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado.

After speaking with Doug for a bit, we briefly look at a few other animals that lived in the seaway.  I’ve included those images here, as well as several more fascinating creatures that I didn’t get the chance to cover in the documentary.

Zack Neher for scale with the famous Xiphactinus gillicus fish-within-a-fish Inception fossil on display at the Sternberg Museum of Natural History in Kansas Photo Credit Mark Neher

The famous “Fish-within-a-fish” Inception fossil, on display at the Sternberg Museum of Natural History in Kansas.  It appears that the larger fish, Xiphactinus, died shortly after ingesting a smaller species of fish, Gillicus. Photo Credit: Mark Neher

African dwarf clawed from Hymenochirus sp. after choking to death on some sort of algae eater Photo Credit Zack Neher

Although I always thought it a bit hard to swallow that the Xiphactinus choked to death on prey that was simply too large for it, a startling encounter with my pet African dwarf clawed frog (Hymenochirus sp.) a few years ago changed that.  Apparently, it had decide that going after the algae eater in the tank was a good idea, despite the fact that the algae eater was much larger than it could reasonably expect to handle!

The teeth of the prehistoric shark Cretoxyrhina on display at the Sternberg Museum of Natural History in Kansas with Mark Neher Photo Credit Zack Neher

The teeth of the prehistoric shark Cretoxyrhina on display at the Sternberg Museum in Kansas.  This shark is thought to resemble the modern great white shark (Carcharodon carcharias) in size and general shape.

Model of the ammonite Jeletzkytes on display at the Houston Museum of Natural Science in Texas with Cian Kinderman Photo Credit Zack Neher

This is a model of the ammonite Jeletzkytes on display at the Houston Museum.  This ammonite genus was one of many that inhabited the Western Interior Seaway.  Although ammonites resemble the modern genus Nautilus, they are only distantly related to one another.

Mona Kamath sitting on a specimen of Placenticeras meeki, a giant ammonite, at the Kremmling Cretaceous Ammonite Locality in Kremmling Colorado Photo Credit Zack Neher

Mona Kamath sitting on a specimen of Placenticeras meeki in the field at the Kremmling Cretaceous Ammonite Locality.  Placenticeras is a giant genus of ammonite, and are fairly abundant at the site.  To learn more about KCAL, check out this post from the The Natural World Archives, by guest blogger Wayne Itano.

Didymoceras cheyennensis ammonite attached to an Inoceramus simpsoni clam from North Dakota on display at the Mace Brown Museum of Natural History in South Carolina Photo Credit Zack Neher

The bizarre fossil shell of the ammonite species Didymoceras cheyennensis, attached to a specimen of the fossil clam Inoceramus simpsoni, on display at the Mace Brown Museum of Natural History in South Carolina.  In my opinion, Didymoceras is one of the most ridiculous and impractical animals that I can imagine.

Mounted skeletons of Archelon ischyros Elasmosaurus and other extinct sea monsters on display at the Black Hills Institute of Geological Research, Inc. in South Dakota with Mikaila Bloomfield Seamus Kieran and Emily Barber Photo Credit Zack Neher

Mounted skeletons of the giant sea turtle Archelon ischyros, the long-necked plesiosaur Elasmosaurus, and an assortment of other extinct sea monsters on display at the Black Hills Institute of Geological Research, Inc. in South Dakota.

Mounted skeleton of the enormous car-sized sea turtle Archelon ischyros on display at the Black Hills Institute of Geological Research, Inc. in South Dakota with Mikaila Bloomfield Seamus Kieran and Emily Barber Photo Credit Zack Neher

A closer shot of the enormous car-sized sea turtle Archelon ischyros.  Archelon is the largest species of sea turtle ever discovered, and is thought to be fairly closely related to the modern leatherback sea turtle (Dermochelys coriacea).

Mounted skeleton of the plesiosaur Elasmosaurus on display at the Black Hills Institute of Geological Research, Inc. in South Dakota with Mikaila Bloomfield Seamus Kieran and Emily Barber Photo Credit Zack Neher.jpg

The enormous and ridiculously elongate neck of the plesiosaur Elasmosaurus.  Reminiscent of the terrestrial sauropods, the heads of these creatures look almost comically small at the end of their necks, the length of which could vary considerably between different genera.

Despite the mountains and the mile-high elevation that we see today, it is always a startling reminder to come across a fossil seashell or shark tooth while out hiking and enjoying the Colorado outdoors.

The Flatirons and the Rocky Mountains covered by clouds in Boulder Colorado Photo Credit Zack Neher

 

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A Brief Fossil History of Camelids

What do World War I and II, penguin flippers, heat exhaustion and dehydration, Snowmass ski resort, the inspiration for Indiana Jones, warm-blooded fish, the accidental death of John Ainsworth Horrocks, the neck of the giraffe, luscious eyelashes, and Hawaiian seabirds all have in common? If you thought that they will all be featured in this three-part post about the dromedary camel, then you are correct.

Meredith Leung riding on the back of a dromedary camel Camelus dromedarius in the Sahara Desert in Morocco on Semester at Sea Spring 2016 with Michael Collett Kim Kassander Haley Collins and Emily Kaplan Photo Credit Zack Neher

Meredith Leung, one of my friends from Semester at Sea, riding on the back of a dromedary camel (Camelus dromedarius) in the Sahara Desert in Morocco.

While in Morocco, my friends and I got the chance to ride dromedary camels in the Sahara Desert, an opportunity that I was very excited about. The first thing that struck me as we rode out between the dunes was how barren and inhospitable the place was (which probably seems pretty obvious, but was still surprising to witness). I was, however, surprised at how many large shrubs and bushes could be found fairly frequently, a number I imagine would decrease the further into the desert you get. But even with the surprising amount of shrubbery where we were, it didn’t look like a place that would allow animals as large as a camel to survive. But survive they had, for millions of years, and that was one of the things that interested me the most.

A dromedary camel Camelus dromedarius silhouetted against the horizon in the Sahara Desert in Morocco on Semester at Sea Spring 2016 with Michael Collett Kim Kassander Meredith Leung Emily Kaplan and Haley Collins Photo Credit Zack Neher

A domesticated dromedary silhouetted against the horizon.  The single hump on the back of the animal is plainly visible in this photograph.  The related Bactrian camel (Camelus bactrianus) has two humps.

Despite their absence on the continent today, the earliest camels actually evolved in North America, around 35 million years ago (MYA).  These small, early camels looked more like modern gazelle than today’s camels, as they were small, slender creatures with sharp hooves to aid in running.  Over time, they diversified from their small, goat-sized ancestors to a fantastic array of shapes and sizes, and inhabiting an equally diverse set of biomes, a much greater diversity than we see today. Some evolved similar to modern day gazelle, deer, and pronghorn, adapted for faster running in open areas. Others became huge, larger than modern day camels. Still others found their way northwards, inhabiting the most northern reaches of Canada in the frigid Arctic. It wasn’t until a few million years ago that the camelids found their way outside of North America. In one direction, we see the ancestors of the modern day guanaco, vicuña, alpaca, and llama cross the Isthmus of Panama into South America. Meanwhile, the ancestor of the modern dromedary and Bactrian camels dispersed from Alaska into Russia via the Bering Land Bridge (which humans would later use to cross in the opposite direction).

Mounted fossil skeleton of the extinct camelid Paleolama on display at the Houston Museum of Natural Science in Houston, Texas with Cian Kinderman Seamus Kieran Mikaila Bloomfield and Emily Barber Photo Credit Zack Neher

A mounted fossil skeleton of the extinct camelid Paleolama on display at the Houston Museum of Natural Science in Houston, Texas.  Paleolama was a mid-sized North American species that lived during the Ice Age.  You can see the resemblance in the overall body plan between Paleolama and the modern dromedary.

Humans would have actually encountered wild camels in North America when they first arrived during the last Ice Age.  Even in Colorado, we find the remains of Ice Age camels that would have lived alongside more famous and charismatic megafauna, such as the Columbian mammoth. In 2011, fossil bones of the genus Camelops were unearthed during the massive Ice Age dig at the Snowmass ski resort, discovered in the same layers as the bones of Columbian mammoth, deer, and bison. Although the exact cause of extinction is not entirely certain, there is a growing body of evidence that suggests that many of the large Ice Age mammals were driven to extinction by the arrival of early humans approximately 10,000 years ago, making the Ice Age Camelops another possible casualty of the spread of humanity.*

Fossil skull cast of the extinct camelid Camelops on display at The Living Desert Zoo and Gardens in Palm Desert California with Mark Julie and Dani Neher and Rick Nick and Sydney Carlson Photo Credit Zack Neher

This is a fossil skull cast of the extinct camelid Camelops, on display at The Living Desert Zoo and Gardens in Palm Desert, California.  Check out how large those nasty-looking front teeth are.  Unlike deer, camels evolved offensive weapons such as large, sharp teeth to combat potential predators.  Even a bite from today’s camels is nothing to joke about.

Even though we typically think of camels as exclusively desert animals, the fossil record shows us that in prehistory, the camel family had become adapted to a wide variety of habitats and niches. The development of a nomadic, desert lifestyle actually appears to be a fairly recent one!

Michael %22Big Mike%22 Collett riding on the back of a dromedary camel Camelus dromedarius in the Sahara Desert in Morocco on Semester at Sea Spring 2016 with Meredith Leung Kim Kassander Emily Kaplan and Haley Collins Photo Credit Zack Neher

Michael “Big Mike” Collett riding on the back of a dromedary in the Sahara.  See where the green rope is attached to the camel’s lower jaw?  If you look at the picture of the Camelops skull, you can see a large gap between the front teeth and the molars, called a diastema.  For these camels, many of the ropes were looped through here.

Join us next time, as we investigate an adaptation of the modern camel that helps keep it cool in the desert heat….and helps keeps penguins warm underwater!

 

* Unfortunately, the investigation is a bit of a COLD CASE.  Boom, Ice Age puns.