You wouldn’t need to swim in Late Cretaceous seas. If you’ve seen the primary Jurassic World film, you’ll acknowledge a mosasaur because the creature that leapt from the water to eat a terrific white shark. That movie might have exaggerated the true measurement of mosasaurs, however the impact is real: some species might attain terrifying lengths. These reptiles spent their lives within the water, however they breathed air. They had fins, lengthy tails, mouths filled with enamel, and could possibly be anyplace from 10 to 50 ft in size. Scientists classify them as ‘squamates,’ a time period that refers to lizards and snakes. And but, pinpointing what mosasaurs really have been stays elusive.

Two shows on the annual meeting of the Society of Vertebrate Paleontology in Toronto this November supplied a glance into present mosasaur analysis: how they could have captured and devoured prey, whether or not they have been venomous, in addition to the place they could have roamed and what they may have eaten. These revelations are the newest home windows into marine reptiles that lived some 66 million to 100.5 million years in the past.

Henry Sharpe, an undergraduate pupil on the University of Alberta, and Amelia R. Zietlow, a PhD candidate on the Richard Gilder Graduate School on the American Museum of Natural History in New York, described a few of their ongoing analysis into mosasaur jaws. These fossils supply thrilling clues as to how they could have captured prey.

When many people consider toothed aquatic predators, we would assume dying by swift, highly effective chew. But that wasn’t essentially the case with mosasaurs. Not solely do mosasaurs possess a kinetic, or moveable, jaw, however scientists like Sharpe and Zietlow are unraveling what different fearsome capabilities they could have had in widespread with their residing squamate family.

Jaws that might open additional large

To start with, squamates have an intramandibular joint—a joint in the midst of the decrease jaw. Some lizards and snakes “have developed a hinge in the middle of these bones,” Sharpe defined. “And this hinge is sometimes looser and sometimes more rigid, depending on the species, but they all have basically a joint in the middle of the lower jaw.” That joint permits movement between the 2 halves. “The jaw can kind of bend forward at that point in some taxa,” Zietlow stated. “In other taxa, it can kind of bend outward. That varies from mosasaur to mosasaur.”

Sharpe, Zietlow, and their colleagues studied uncommon full mosasaur decrease jaws in North American museums, “because we wanted to look at how mosasaur jaws related to other marine animals versus other squamates,” stated Sharpe. In different phrases, they’re on a quest to raised perceive how mosasaurs ate primarily based on these fossils, in addition to how different species—together with residing whales, snakes and lizards, and extinct marine reptiles—may examine to mosasaurs.

For instance, take the jaws of as we speak’s snakes and hyenas. Snake jaws aren’t fused collectively, they usually’re delicate. This means they can’t solely transfer every separate jaw bone however each units of enamel independently as they seize and swallow their prey. “They actually walk the jaws up the prey as they eat it,” described Zietlow. This is vastly completely different to a hyena jaw, a solidly constructed construction with no flexibility that’s robust sufficient to crush bones.

Now contemplate what is understood about most mosasaur species: They usually didn’t have serrated enamel to tear off chunks of flesh, they usually didn’t have arms to carry prey, however that they had versatile mandibles. This, Zietlow asserts, signifies they most likely ate what they might swallow entire. Yet, “most mosasaurs don’t seem to have had strong bites proportionally for how big they are,” she stated. “That’s where this research question initially came from: ok, so what are they doing? How are they hunting prey? How are they killing it? How are they eating it?”

Zietlow defined that, whereas scientists aren’t positive precisely how mosasaurs ate, their anatomy does counsel sure feeding methods. Prognathodon, an unlimited mosasaur species, have been the “meanest-looking animals that ever lived,” she stated, with “huge conical teeth with serrations on both sides and built-in bony ridges above their eyes. They’re the ones that we most often find with plesiosaurs and mosasaurs and other large vertebrates inside of them.” Those serrated enamel are an anomaly, as only a few mosasaurs had them, and this leads paleontologists to consider that these with serrated enamel had the power to tear chunks of flesh from their prey. There is, Zietlow added, as-yet unpublished intestine content material proof that Prognathodon might have been ripping substantial physique components off of prey.

The center joint will not be the one moveable facet of the mosasaur jaw. There’s additionally the mandibular symphysis, the purpose at which two decrease jaw bones join. In our skulls, the mandibular symphysis is fused proper at our chin. Our decrease jaw is, primarily, one strong bone. In mosasaurs, Sharpe defined, this joint was not fused; it was looser. Like Zietlow, Sharpe famous that intestine contents in some mosasaur fossils reveals that “we have mosasaurs that are eating plesiosaurs and turtles and other mosasaurs that are up to half their length. So they’re eating very large things. And having these jaws that could open up like this basically to swallow prey would be very, very helpful.”

Remarkably, mosasaurs might have used their tongue to odor. Like different squamates, resembling snakes and monitor lizards, mosasaurs had two telltale holes within the backside of their jaw that point out that they had that particular organ.

“We know that they had it,” Zietlow confirmed. “To what degree they were using it, we’re not so sure, because they’re aquatic. It’s possible they were using other senses—for example, their ears appear to be very well developed. This is still an active area of research. “

A venomous bite?

If mosasaurs had moveable jaws, if their jaws were proportionately weak, and if they used their tongues to smell, might they also have featured another familiar trick of modern squamates? Could mosasaurs have been venomous?

It’s not a new idea, but the capacity for venom in extinct creatures is tough to prove. Until recent decades, many living venomous lizards and snakes weren’t even recognized as such by scientists, typically because the species were too small to affect humans or the venom in question wasn’t directly fatal. Rather, it was an anticoagulant. “It’s helping their prey bleed out,” he stated. For people, the quantity of bleeding was minimal, so it was straightforward to overlook. “Because of this,” Sharpe concluded, “scientists realized that grooves in the teeth are not a 100% accurate indicator for venom.”

Iguanas, which don’t have grooves of their enamel, are one of many squamates now recognized to have been venomous. In iguanas, Zietlow acknowledged, “the venom sac is actually vestigial, so they’re not using it, they’re not secreting it. It’s just like a saliva gland that’s modified. It’s a venom gland, but they don’t use it anymore because they’re primarily herbivorous.”

And this, she defined additional, has implications for the venomous lizard household tree known as toxicoferans, and it consists of snakes, monitor lizards, gila monsters, and now iguanas. “They all,” she stated, “share a common ancestor, and what that means is that the ancestor to this group probably was venomous.” That’s vital, she defined, as a result of “even if mosasaurs weren’t using venom to kill things, it’s possible that, like iguanas, it was present but vestigial.”

Diets of turtles, mollusks, crustaceans, fish, and extra

But what have been mosasaurs consuming, and, with a number of sizes and species of mosasaurs in the identical ocean, how have been they capable of coexist?

This is the main focus of ongoing analysis by Femke Holwerda, a postdoctoral analysis fellow on the Royal Tyrrell Museum of Palaeontology, who introduced what she categorized as a “pilot study” on the SVP annual assembly. She has carried out an unlimited quantity of labor finding out fossils of creatures that lived inside the Bearpaw Sea in southern Alberta, Canada, all of that are housed on the Royal Tyrrell Museum. The Bearpaw Sea was a part of the bigger Western Interior Seaway, a Cretaceous physique of water that reduce via what’s now North America.

That sea was residence to at the very least 4 or 5 species of mosasaur (Mosasaurus missourensis, Prognathodon overtoni, Plioplatecarpus primaevus, Tylosaurus sp., and a potential Mosasaurus conodon) in addition to turtles, sharks, sawfish, lobsters, cuttlefish, elasmosaurs, fish resembling Enchodus, mollusks, and ammonites. Holwerda needs to disclose extra about these historic interrelationships, which is hard enterprise. Reconstructing ecosystems which can be 66 million to 145 million years previous is not any small feat. Absent direct proof like intestine contents, her analysis includes appreciable detective work.

“Mosasaurs are the star of the show, but I thought it was important to look at the other components of the ecosystem,” Holwerda stated.

Which is, partially, which makes her analysis so intriguing. Mosasaurs might not exist, however virtually all the pieces else she research has trendy descendants. All of the aforementioned species have been discovered inside the Bearpaw Formation, excluding sharks and sawfish, two species present in different places however recognized to co-exist on the similar time interval.

Her analysis is multi-faceted and nonetheless a piece in progress To get a greater image of historic eating regimen, she’s analyzed mosasaur dental microwear, finding out the pits, scratches, and gouges on fossil enamel. 2D microwear means observing and counting the variety of pits versus scratches on every tooth. 3D microwear, which includes the usage of specialised software program, presents considerably extra information and fewer human error. Both present a glance into what a species was consuming over the previous a number of weeks or months previous to dying.

“Some say 2D microwear is no longer relevant now that there is the more in-depth 3D microwear analysis,” she admitted, “but I still think it adds information to the story, especially coupled with 3D microwear.”

Her plan is to make use of each, however for her presentation at this yr’s SVP assembly, she mentioned the 2D dental microwear outcomes, energy-dispersive x-ray spectroscopy (EDX) and isotopic evaluation.

Holwerda has been capable of apply that information and correlate it to the place these species might have been feeding. In different phrases, she was capable of finding proof for area of interest partitioning inside the Bearpaw Sea. And she did this by finding out strontium and barium over calcium inside the fossils. Of word, she discovered that the big mosasaur Prognathodon shared a eating regimen with sawfish; each are durophagous, or recognized to have eaten more durable substances. Those more durable substances, primarily based on the fossils discovered within the Bearpaw Sea, would have at the very least included mollusks, crustaceans, probably ammonites. The medium-sized mosasaur Plioplatecarpus appears to have eaten the identical fish as Cretaceous sharks. And Mosasaurus seems to have been making the most of all accessible meals within the Bearpaw Sea, because the outcomes overlapped the diets of all different massive historic marine species she sampled.

Certain isotopes supply perception into how deeply mosasaurs might have been capable of dive, which is how Holwerda was capable of decide that solely Prognathodon and Mosasaurus—two of the most important species—seem to have been swimming within the deepest components of historic seas.

Remarkably, Holwerda is even capable of decide the salinity and temperature of the water via oxygen isotopes present in tooth fossils. Strontium isotopes supplied indications of how near shore mosasaurs might have migrated or whether or not they remained out within the ocean. This is as a result of, in keeping with what scientists perceive up to now, strontium variations in seawater will solely get recorded nearer to shore, as these point out freshwater enter. Strontium in salt water is kind of steady.

Her analysis thus far signifies that the assorted mosasaur species within the Bearpaw Sea lived in numerous areas and ate various things, however extra information is required. Her greatest concern in the intervening time is what she refers to as “those pesky, pesky turtles.” Although she sampled a couple of handful of turtles from the Royal Tyrrell Museum, just one produced sufficient materials for the mass-spectrometer to offer any information.

“Prognathodon should be eating those turtles,” she acknowledged, “or you should see that from the signal, because there are Prognathodon with turtle remains in their stomach.” To decide this with any accuracy, she would love a extra strong turtle pattern for comparability.

Holwerda expressed concern about trendy local weather change, questioning, “What can we learn from the past, from that warm Cretaceous sea?” It was a time, she stated, when neither the North or South Pole had any ice and sea ranges have been a lot increased. “For the mosasaurs, of course, it was perfect! It was nice and warm.” But as our planet heats up, what does that imply for current marine animals?

There continues to be a lot work to be carried out by all three of those paleontologists, and each teams point out there are various questions they’ve but to reply.

“Mosasaurs are such common fossils,” Zietlow stated. “They’ve had a lot of work done on them; they’re related to living animals, and yet we still don’t know the most basic fact about them which is: what are they? We know they’re lizards—but what kind of lizard are they?”

Jeanne Timmons (@mostlymammoths) is a contract author primarily based in New Hampshire who blogs about paleontology and archaeology at mostlymammoths.wordpress.com.