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Shonisaurus lived during the Norian stage of the late Triassic period (215 mya). S. popularis measured around 15 metres (49 ft) long. A second species from British Columbia was named Shonisaurus sikanniensis in 2004. S. sikkanniensis was one of the largest marine reptiles of all time, measuring 21 metres (69 ft). However, phylogenetic studies later showed S. sikanniensis to be a species of Shastasaurus rather than Shonisaurus.

Shonisaurus and Shastasaurus may have specialized on eating shell-less cephalopods, as adult specimens appear to lack teeth entirely, a trait that is not found in most other ichthyosaur species.

A unique fossil bed of these massive marine reptiles led paleontologists to hypothesize that an equally massive octopus ancestor, or “Triassic Kraken,” may have killed the Shonisaurs and arranged them in a particular pattern. Modern-day octopods are known to create middens using prey items, so the idea is not entirely unfounded. The scientists have gone as far as to suggest that this ancient Shonisaurus midden may have been created as a sort of octopod “self-portrait” indicating that the ancient kraken may have been an intelligent being. An alternative (perhaps more likely) theory suggests that the midden may be a sexually selected trait in the ancient octopod species.

Learn more about the kraken midden here.

Learn more about the Shonisaurus here.

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Shastasaurus: Super Special Awesome Non-Dinosaur Post!

I’ve decided to do a “mega-post” on a prehistoric animal. Luckily for our non-dinosaur fans, the subject is no dinosaur. It’s not even an archosaurs, as a matter of fact. Yes, I’m talkin’ ‘bout Shastasaurus, one of the largest aquatic vertebrates (and the largest marine reptile) of all time. Take that, usual post style.

The Names: The generic name refers to Mount Shasta, which can be found in Northern California today. The type species, Shastasaurus pacificus, has a specific name that you should be able to decipher. I’ll leave S. sikanniensis and S. liangae out for now, because I have no idea what the etymology of their specific names mean. Sorry.

Accumulation of Remains and Names: Originally, only Shastasaurus pacificus was regarded as a species of Shastasaurus. Over time, more species were added. These species were Shastasaurus (Formerly Guanlingosaurus) liangae and Shastasaurus (Formerly Shonisaurus) sikanniensis. Some dubious species S. carinthiacus, S. neubigi) have been recovered from Europe, but probably don’t belong to Shastasaurus at all.

Where? S. pacificus was recovered in Northern California (U.S.A.). S. sikanniensis was recovered in the Pardonet Formation of British Columbia (Canada). S. liangae was recovered in Falang Formation of Guizhou Province (China).

When? All species of Shastasaurus are from the Carnian Stage (roughly 235-228 million years ago)of the Late Triassic Period. These creatures tend to be found in younger Carnian deposits.

Anatomy: Shastasaurus was peculiar among ichthyosaurs in that it bore a short, toothless snout. Other ichthyosaurs possessed long snouts that were adorned with many sharp teeth. In fact, even juvenile Shastasaurus had toothless mouths, implying that they were born toothless. In Shastasaurus liangae (the only species associated with adequate skull remains), the head is small compared to the body, being only about 8 per cent of the total length of the body. Shastasaurus was very slim in profile, with a ribcage less than two meters deep despite the 7-meter distance between the tips of its front flippers. Both Shastasaurus and Shonisaurus (the latter genus refers only to S. popularis) are often depicted with a dorsal fin, despite the fact that neither genus really had one. The dorsal fin is a more derived trait that more advanced (and later-occurring) ichthyosaurs such as Temnodontosaurus possessed.

Size: S. liangae was a fairly small species of Shastasaurus, with a length of only 27 feet (8.3 meters). The largest species, S. sikanniensis, was an immense animal, measuring about 70 feet (21 meters) long. These creatures, while not as threatening as Liopleurodon or Tylosaurus, constituted the largest marine reptiles of all time, and some of the largest marine animals of all time in general.

Diet: Unlike more primitive ichthyosaurs (Thalattoarchon!) but very much like more derived ones, Shastasaurus didn’t feed on animals its size or bigger, a dietary preference very easily proven by analyzing the skull of the animal. It can be concluded that Shastasaurus was a suction feeder that preyed on shell-less cephalopods and fish. Suction feeding is a method of feeding that uses, well… suction. The predator expands its oral cavity’s volume or throat, causing a pressure difference between the inside and outside of the animal. When the mouth of the predator is open, water then flows into the predator’s mouth, carrying the prey item in with it. This feeding method is seen in many marine predators of the present, including bony fish.

Phylogeny: Shastasaurus was a member of the epynomous Shastasauria, a group of fairly primitive ichthyosaurs which were somewhere between the fairly primitive forms (such as Cymbospondylus) and more advanced forms (Californosaurus, for example.

Conclusion: Shastasaurus is an odd ichthyosaur. Not only was it a behemoth, it fed on very little animals and had truly bizarre proportions. It and its closest relatives were gone by the Jurassic, presumably because of climate change or other phenomena. This post was enjoyable because it was comprehensive, and I hope to do something much like it again.

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