Were the Giant Shark Species that We Know Today Already Present 91 Million Years Ago?

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Carmina Joy in History

Last updated: 04 March 2020, 06:23 GMT

Deep in the heart of northern Kansas, researchers excavated farmland that used to be under the ocean. Surprisingly, they ended up finding a brand new species of shark that lurked beneath the surface around 91 million years ago.

During the middle to the late Cretaceous period, the region of the United States we know now as the Great Plains was submerged under the North American Western Interior Seaway, with Mitchell County, Kansas lying at the edge of the eastern boundary of the water.

Just as the oceans are teeming with life today, so too did the ancient seaway. And also like today, sharks were an apex predator that most marine animals feared.

What Was Found? The Giant Shark Specimen


DePaul University professor of paleobiology Kenshu Shimada and Michael Everhart from the Sternberg Museum of Natural History at Fort Hays State University thought they had uncovered the remains of a prehistoric shark species known as Credotus crassidens, which ranged from England to North America.

However, when they compared the teeth they had found to known Credotus crassidens teeth, they realized to their delight that they had just found a brand new species of shark, which they named Cretodus houghtonorum in honor of Keith and Deborah Houghton, who owned the land where the specimen was found and donated it to the museum.

The pair of researchers found more than just teeth, which they explained in a paper published in the Journal of Vertebrate Paleontology: The specimen is largely disarticulated but consists of at least 134 teeth, 61 vertebrae, 23 placoid scales, and multiple small fragments of calcified cartilage. The scale morphology suggests that Cretodus was a more sluggish shark than Cretoxyrhina and Cardabiodon. The vertebral centra are well calcified and exhibit many radiating calcified lamellae typical of ‘lamnoid vertebrae.’ The teeth are represented by 34 upper left teeth, 28 upper right teeth, 31 lower left teeth, and 22 lower right teeth, with the lamnoid tooth pattern. The dentition shows a strong tendency to monognathic heterodonty, and each tooth row consisted of up to at least five functional and replacement teeth.

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Bigger than the Great White


The teeth, of course, tell us a lot about sharks both living and extinct. But this specimen revealed even more. Much of what we know about extinct sharks is based on isolated teeth, but an associated specimen representing a single shark individual like the one we describe provides a wealth of anatomical information that in turn offers better insights into its ecology,” Shimada, said in a statement.

Based on the vertebrae, the team estimated the shark’s length at around 17 feet, and that it could have possibly reached 22 feet, bigger than a Great White Shark named Deep Blue estimated to be 20 feet in length and is also a distant cousin of the Credotus along with the Tiger Shark.

As important ecological components in marine ecosystems, understanding sharks in the past and present is critical to evaluate the roles they have played in their environments and biodiversity through time, and more importantly how they may affect the future marine ecosystem if they become extinct.

Indeed, sharks are vulnerable to extinction today due to the demand for shark fin soup. But if sharks disappear, ocean eco-systems would be thrown into chaos. Besides, Shimada and Everhart believe Credotus houghtonorum engaged in cannibalism before birth, much like modern-day sharks.

What is more exciting is its inferred large size at birth, almost 4 feet or 1.2 meters in length, suggesting that the cannibalistic behavior for nurturing embryos commonly observed within the uteri of modern female lamniform must have already evolved by the late Cretaceous period.



The Conclusive Findings


Despite these scientific findings that have been mentioned earlier, there was not the most exciting part of the excavation. Like a forensic team, Shimada and Everhart had the opportunity to map out a series of events that occurred 91 million years ago, starting with the ingestion of a hybodontid shark by the Credotus, only for the Credotus to die and be scavenged upon by a Squalicorax shark before it, too, succumbed to whatever killed it near the same spot.

During the excavation, two teeth of Squalicorax cf. S. falcatus and two partial dorsal fin spines of a hybodontid shark were discovered. The two fragmentary dorsal fin spines are thought to have come from a single hypsodont individual that was likely ingested by the individual of Cretodus houghtonorum. The teeth of S. cf. S. falcatus, on the other hand, may represent teeth that were accidentally shed during scavenging of the carcass of C. houghtonorum.

If so, this fossil record may represent a trophic chain of three different sharks. Besides, the present fossil record suggests that C. houghtonorum typically inhabited nearshore environments and Cretoxyrhina Mantelli offshore environments within the North American Western Interior, possibly representing a case of resource partitioning between the two species.

Circumstantially, we think the shark possibly fed on the much smaller hypsodont and was in turn scavenged by Squalicorax after its death. That’s a fascinating find that certainly provides a clear picture of the eat or be eaten world of Cretaceous period oceans. These waters were dangerous.

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Conclusion




In the end, the scientists understand that without the cooperation of landowners, they would not be able to make discoveries like this one, which is why they hope to foster goodwill among landowners across Kansas and the rest of the world so that further research can shed more light on these ancient eras in Earth’s history and fill in the gaps with new species so we can further understand the creatures living among us today.

Sharks are an important foundational species in the ocean environment. Letting them go extinct would be a great loss. Sharks have survived on this planet for over 91 million years. If they die out now, we only have ourselves to blame and we’ll suffer for it just as much as every species that relies on the ocean.