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Thalattoarchon saurophagis: Marine Predators.

Size: 28 feet (8.6 meters) long.

Time Period: The Anisian Stage of the Middle Triassic.
Locale:
The Favret Formation of Nevada in the United States.

Name: The generic name means “lord of the sea” in reference to the predatory nature of the animal. The specific name means “serpent-eater,” because the animal may have eaten its own relatives.

Even though the dinosaurs ruled the land during the Mesozoic, the sea was one place that they never truly conquered. Even today, seagoing birds are far from the top of the food chain, mostly due to huge aquatic predators. A trend of evolution was the tendency of some groups to return to the water even though their ancestors had once crawled out of a primeval ocean themselves. During the Mesozoic, many sea reptile groups appeared, from plesiosaurs like Liopleurodon to seagoing lizards like Plotosaurus to marine crocodiles like Dakosaurus (see my post on the very same animal for more). One other group that is slightly less well-known is the ichthyosaurs, a shame considering how cool they were. These fish-mimics had their beginnings in the Triassic Period, and finally met their end during the Early Cretaceous for reasons yet unknown (but possibly due to the appearance of aforementioned seagoing lizards). One of the earlier species of ichthyosaur may also be the sea’s first macropredatory animal (an animal capable of seizing animals as big as it was and eating them).

Thalattoarchon is the name of this ichthyosaur, whose primary difference from later relatives like Temnodontosaurus and Opthalmosaurus is its snout. Whereas you might find conical, unserrated teeth for grabbing fish and cephalopods in the snouts of most ichthyosaurs, Thalattoarchon had large, thin teeth with two cutting edges and smooth crowns. These blade-like teeth were probably helpful in the seizing of other prey, and though their surfaces aren’t serrated like a Tyrannosaurus’s, they resemble the teeth of such evolutionary success stories as the mosasaurs and pliosaurs. These animals were also kings of the ocean in their own times.

Since not very much skeletal material of Thalattoarchon is actually known, its appearance must be inferred. Like most primitive ichthyosaurs, it probably had an elongated, eel-like body and a barely-developed tail fin to aid with swimming. It was found in the same area as its look-alike, the ichthyosaur Cymbospondylus, which it differed from by having a head twice the size of Cymbospondylus’s head relative to its body. In fact, Thalattoarchon may have even evolved its lethal dentition to kill and eat other ichthyosaurs, but until actual evidence of this is found (coprolites, bones of other animals found with Thalattoarchon) no conclusion can be reached.

Another thing that Thalattoarchon indicates was how life was recovering after the Permian-Triassic extinction, which wiped out over 90% of all life on the planet. Specialized macropredatory creatures like this big ichthyosaur only appear when communities of animal are diverse and well-established. If one lived in a community that was not like this, it would simply starve due to lack of food. Since Thalattoarchon lived only 8 million years after the great extinction, the marine life of the world had to have bounced back and specialized considerably in order to accommodate such specialized predators. Only species that were truly resilient would have survived to create these new environments, alluding to the possibility of Permian ancestors of groups like the ichthyosaurs that we haven’t uncovered yet. 

In conclusion, Thalattoarchon is the first huge badass marine predator described in 2013. Not only is it a huge marine apex predator, but one of the first. It fills in a bit of information about ichthyosaur evolution and how a devastated world bounces back after a major extinction, like the kind that not even the ichthyosaurs could avoid millions of years after this sharp-toothed predator ruled the seas.

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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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