Pterandon sternbergi. By John Conway - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1790653 The Niobrara Formation is a geological formation from the Coniacian to the Campanian stages of the Late Cretaceous in Kansas. It spans five million years of the Western Interior Seaway's history, from 87 to 82 Ma. The interesting thing about this formation, though, is that in the Late Cretaceous, Kansas was covered by an ocean. [1] This map of North America in the Campanian gives an idea of the impact the Western Interior Seaway had on the region's geography. By Scott D. Sampson, Mark A. Loewen, Andrew A. Farke, Eric M. Roberts, Catherine A. Forster, Joshua A. Smith, Alan L. Titus - http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012292, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=55596550 The Niobrara Formation In many ways, the Niobrara was very similar to ocean ecosystems today. Fossils of phytoplankton have been found in the Niobrara and have even formed into oil. [2] Phytoplankton and other small and/or planktonic organisms would have formed the diet of others. But where the wildlife gets most interesting is where it differs from ecosystems today, and that's what we'll talk about in this series of blogposts. This one, part 1, will cover bony fish and turtles. Keep in mind I won't be able to cover every species or group, I'll have to settle for covering a few unique species, though of course all extinct species are interesting and important in their own right. What fauna does the Niobrara have that, say, the Atlantic Ocean today does not? Bony Fish Like many ocean ecosystems today, there were many species of bony fishes in the Niobrara Formation. However, of course, these were extinct bony fish and so were different and in a lot of cases very cool. [3] An especially interesting resident of the Coniacian seaway would have been Micropycnodon, a small, fat, peg-toothed fish similar to today's parrotfish. It may have fed on small invertebrates that encrusted the shells of inoceramids [4], a type of giant clam. [5] Peg-like pycnodont (possibly Micropycnodon kansasensis) teeth from the Menuha Formation in Israel. By ARetzler11 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14865118 Another very interesting bony fish that would have inhabited the seaway was Protosphyraena. Similar in appearance to today's modern swordfish, Protosphyraena grew up to about 3 meters (about 10 feet) long and would probably have been pretty common in the seaway. It might have fed on schools of smaller fish, striking them with its elongated rostrum (nose) to stun them like swordfish do today. P. perniciosa and the slightly smaller P. nitida, note the long pectoral fins and thin pelvic fins almost like ribbons. And, of course, the awesome-looking teeth. By Creator: Dmitry Bogdanov - [email protected], CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=4937666 Another large bony fish (closely related to Protoshyraena in the group Pachycormidae) that would have occupied a very different ecological niche was Bonnerichthys. It, like the much larger and more well-known Jurassic Leedsichthys, would have filter fed using specialized gill rakers, a very different lifestyle to Protosphyraena. A size comparison of pachycormid fishes, showing five well-known genera, including Bonnerichthys and Protosphyraena. By Eotyrannu5 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=72201097 Some larger carnivorous bony fish ate the ones previously mentioned, most notably the ichthyodectids. This group of large predatory fish includes many of the larger bony fish from the Niobrara. Xiphactinus is the most famous of these, it being a 6 metre (20 foot) predatory fish that probably was one of the top predators in the Niobrara. Specimens of Xiphactinus have been found with the smaller ichthyodectid Gillicus in them, suggesting that the predator may have tried to swallow the prey and then choked on it, causing an untimely death. X. audax with the poor Gillicus in its stomach. By Chip Clark, Smithsonian, National Museum of Natural History - http://qrius.si.edu/browse/object/10022846#.WL-mDX-ZPy1, Public Domain, https://commons.wikimedia.org/w/index.php?curid=56900551 Turtles If you thought those fish were weird, and don't like weird organisms, then stop reading now. Because it's only going to get weirder (or more awesome, or both, depending on your point of view) from here on out. Archelon and Protostega were giant protostegid turtles from the Smoky Hill Chalk. They had hooked beak-like faces (like most turtles), and swam around the seaway, probably eating things like squid, ammonites or maybe small fish. [6] They grew to monstrous sizes, Protostega at around 3.4 m (a little over 11 feet) at most and Archelon at a chart-topping 4.6 m (15 feet). [7] Just imagine for a second swimming in a Cretaceous sea when a turtle roughly the size of a small car passes you. Unless you aggravated it, though, it would probably leave you alone, it’s favorite prey being of the tentacled variety. An Archelon ischyros skeleton, from Wikimedia Commons. This picture was taken in 1902. By Frederic A. Lucas - "Animals of the past" http://www.copyrightexpired.com/earlyimage/bones/display_animalspast_archelon.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2895807 Along with Archelon and Protostega, there were other, smaller, turtles that inhabited the flooded Kansas, like Toxochelys, a smaller (about 2 m or 6 ft) turtle that is more common in the formation. Hope you enjoyed this rather short first blog post. There will be a part 2 and maybe more coming this way, (in which I'll write about all the other animals that inhabited the Niobrara, like mosasaurs, pterosaurs, other sorts of -saurs, and more) as well as some other blog posts on paleontology and the natural world in general. If you enjoyed this, please support Past Earths by spreading the word that this blog exists. Thank you! Sources:
1. “Niobrara Formation.” Wikipedia, Wikimedia Foundation, 4 Aug. 2018, en.wikipedia.org/wiki/Niobrara_Formation. 2. “Niobrara Hydrocarbon Potential.” The Niobrara News, 5 July 2014, www.niobraranews.net/niobrara-hydrocarbon-potential/. 3. “Paleobiota of the Niobrara Formation.” Wikipedia, Wikimedia Foundation, 20 July 2018, en.wikipedia.org/wiki/Paleobiota_of_the_Niobrara_Formation. 4. “A Field Guide to Fossils of the Smoky Hill Chalk.” Marine Turtles, oceansofkansas.com/fieldguide2.html. 5. “Inoceramids.” Marine Turtles, oceansofkansas.com/Inoceramids.html. 6. “Archelon.” Wikipedia, Wikimedia Foundation, 25 May 2018, en.wikipedia.org/wiki/Archelon. 7. “A Field Guide to Fossils of the Smoky Hill Chalk.” Marine Turtles, oceansofkansas.com/fieldguide3.html.
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