Globidens (Globe Teeth) is a genus of mosasaur that lived 84.9 - 66 million years ago, from the Santonian stage to the Maastrichtian stage of the Late Cretaceous Period. It is known from various oceans around the world, from North and South America to Africa, the Middle East, and even Indonesia. The species depicted on Prehistoric Planet is based on Globidens dakotensis,[DN 1] which lived in the Western Interior Seaway of North America.
Globidens grew approximately 5 - 6 meters (16 - 20 feet) length.[1] Its mass is unknown, but based on mosasaurs of similar size, it likely weighed around 1 - 2 metric tons (1.1 - 2.2 short tons). Amongst mosasaurs, it was small, being around half the length of medium-sized members like Kaikaifilu and Prognathodon, and only one-third of the largest members like Tylosaurus proriger and Mosasaurus hoffmannii, the apex predators of its habitat, the Western Interior Seaway. It was, however, still significantly bigger than others like Phosphorosaurus, one of the smallest members of the mosasaur family, and Globidens was still a robust, powerful predator in its own right, equipped with strong jaws and ball-shaped teeth meant for crushing shells with ease. There are at least six species of Globidens, with the one depicted on Prehistoric Planet being primarily based on G. dakotensis.[DN 1]
Jaws and Dentition[]
“ Globidens has broad, rounded teeth that easily crack the ammonites' shell, releasing the air that keeps them buoyant. Without it, they sink helplessly to the seabed. ”
Most mosasaurs have bite forces powerful enough to crunch through the shells of turtles and ammonites, but none were as specialized in dealing with armored prey as Globidens, which is named for the spherical teeth in its jaws, clearly meant more for crushing through shells as opposed to gripping, puncturing, and tearing through flesh. Its durophagous diet is further supported by several crushed bivalve shells found in the remains of a Globidens specimen discovered in the upper DeGrey Formation of South Dakota.[2] Although it appears that Globidens preferred to feed on inoceramid clams and other bivalves by the sea floor, it is equally likely that, as with other mosasaurs, it would have also hunted ammonites, and, as with many predators, it was likely an opportunistic carnivore that fed on the most convenient meal within reach, since rounded teeth in modern-day lizards are fit for a generalist diet.[DN 2]
Senses[]
Globidens is shown occasionally flicking its forked tongue out. As with other squamates, mosasaurs are believed to have forked tongues, which collect chemical particles from the environment to be inserted into the vomeronasal organ (also known as Jacobson's organ) by their palate,[DN 3] which contains a chemosensory system to help the user identify the source of these chemicals for a variety of reasons ranging from prey detection to the determination of the state of other organisms, be they aggressive rivals or individuals open to mating. This feature still works very well for sea snakes, so it would also work just fine for mosasaurs. While usually depicted as long, slim and deeply-forked like those of snakes, Prehistoric Planet instead modeled their tongues after the shorter, thicker, and less-mobile tongues of anguimorph lizards, since mosasaurs are believed to be part of the anguimorph group themselves.[DN 4] However, while this means that mosasaurs are in the same group as varanids (monitor lizards), they do not seem that close to them, and mosasaurs may possibly not be anguimorphs at all.[DN 5]
Speed[]
The speed of Globidens is not stated, though the segment it appeared in made it clear that it is quick enough to catch up with the ammonites it feeds on. Going off of calculations made in the Uncovered segment "How Fast Was A Mosasaur?", where it is said that a mosasaur can cover 75% of its body length in a single second, Globidens, being 5 - 6 meters (16 - 20 feet) long, can cover a distance of 3.75 - 4.5 meters (12 - 15 feet) in one second, or 13.5 - 16.2 kilometers (8.4 - 10.1 miles) per hour. It is possible that, given how it is only one-third the length and around one-eighth the mass of Mosasaurus hoffmannii, Globidens may have been, in theory, faster than these calculations (which are meant for mosasaurs the size and weight of Mosasaurus) make it out to be. Conversely, it is also possible that the extra mass and the greater amount of muscles and generated power allow the larger mosasaurs to accelerate with such great speed, and, due to being smaller and thus, lighter and packing lesser or proportionately weaker muscles, Globidens may not have accelerated to such great speeds, meaning that the calculation only works for mosasaurs possessing a similar length and mass as Mosasaurus. On the show, Globidens is not really shown relying on the "C-start" technique used by Mosasaurus and modern-day fish to achieve top speed, though this is probably not necessary for going after speeding ammonites.
Prehistoric Planet's Portrayal[]
On Prehistoric Planet, Globidens is depicted with orange and brown tones. Countershaded with a dark back and light belly, its face has a more vibrant orange hue, with its snout streaked with thin, dark stripes, and its back covered in broader but more faded dark stripes.
As shown on Prehistoric Planet, Globidens thrived in the warm, shallow waters of the Gulf of Mexico, which was, by that time, part of the Western Interior Seaway, an inland sea that split North America into two landmasses (Laramidia in the west and Appalachia in the east). It was also present in similar seas across the globe, like those in South America, Morocco, Angola, the Middle East, and what is now Timor Island by Indonesia.
Paleofauna[]
“ In the waters that surround North America, there are other giant predators. But they have no rivals. Mosasaurs. They may look like huge sharks, but they are in fact, a kind of aquatic lizard. Size, speed, and powerful jaws mean that very few creatures in the ocean are safe from these hunters. ”
Globidens occupies the role of durophagous specialist in its ecosystem, allowing it to avoid competition with similarly-sized animals such as the lamniform shark Squalicorax or the polycotylid plesiosaur Dolichorhynchops, which possessed a long, thin jaw filled with thin, sharp teeth, meant more for catching fish. Being quite small by mosasaur standards, however, Globidens itself was likely considered viable prey by other, more voracious predators that matched or exceeded it in size, like the bony fish Xiphactinus, Cretoxyrhina (also known as the "Ginsu Shark"), and other, larger mosasaurs that were almost three times the size of Globidens like Tylosaurus proriger and Mosasaurus hoffmannii, powerful apex predators that, when fully grown, can only be threatened by other adult specimens of their kind. Even so, because it seemed to be unchallenged in its chosen niche as a specialized durophage (a lifestyle kept stable by the many ammonites, bivalves, and other shelled prey during its time), Globidens thrived, retaining its place in the ecosystem and surviving far longer than many of the animals it coexisted with (including Cretoxyrhina, which went extinct 73 million years ago due to the shrinking of the Western Interior Seaway in North America and getting outcompeted by massive mosasaurs worldwide). Ultimately, however, Globidens, along with all mosasaurs and many other Late Cretaceous animals, perished due to the Cretaceous-Paleogene Extinction Event, a catastrophe that wiped out three-quarters of life on Earth 66 million years ago.
Hunting Tactics and Feeding Preferences[]
Globidens pursues a Sphenodiscus
“ Before the ammonites can escape, the mosasaur disables as many as it can. ”
While its jaws and teeth can easily crush the armor of its chosen prey, brute force alone is not enough to guarantee hunting success for this durophage. Hence, like most carnivorous animals, Globidens showed a degree of predatory cunning, having anticipated and capitalized on the time when Sphenodiscus shoals come up to lay their eggs, using this knowledge to ambush them in an area the ammonites needed to pass through to get to their destination. It also attacked several of the ammonites in quick succession, simply crippling one before moving on to the next rather than taking its time to consume each prey it catches. That way, it is able to amass a larger amount of food, helpless on the seabed, a banquet it wisely accumulated so it can feed in peace after all the effort and energy it expended.
Globidens rips a Sphenodiscus out of its shell
In the late Campanian-aged upper DeGrey Formation within South Dakota, USA, one Globidens specimen was discovered to contain within its stomach several bivalves, including oysters, what appears to be the lamellar shells of Anomia saltwater clams, and, most of all, the prismatic shells of at least four types of inoceramid clams (which were, at one point, also planned to appear on Prehistoric Planet). This indicates that, while Globidens would have had no problems crushing and swallowing prey while they were still in their shells, it prefers thin-shelled prey mostly comprised of fleshy, visceral mass, like the inoceramids,[2][DN 2] the largest of which could grow up to 1.87 meters (6 feet, 2 inches), with a shell that is merely 3 centimeters (1.18 inches) thick.[3][4] Prehistoric Planet reflects this preference of Globidens in the second segment of North America, where, although the durophagous mosasaur can easily crack the shells of Sphenodiscus with its spherical teeth, which evolved specifically for tackling robust prey, it seemed to only exert this effort when crippling as many of the ammonites as possible. When feeding at a leisurely pace, Globidens is shown ripping the soft bodies of the cephalopods out of their shells instead.
Appearance[]
Globidens catches a glowing scaphitid, while unidentified pterosaurs fly overhead
As revealed by official concept art made by Gaëlle Seguillon, Globidens was originally planned to appear in the fifth and penultimate segment of Coasts, the very first episode of the series, hunting down bioluminescent scaphitid ammonites at night while they were engaged in their mating rituals, the last step in their brief lives before they lay their eggs and finally expire.[PhP 2] This concept was carried over to the most recent episode of the main series, which features Globidens hunting dozens of egg-bearing Sphenodiscus "tiger ammonites" during daytime in the second segment of North America.
The second segment of North America takes place in the Gulf of Mexico, where a Globidens seeks out shoals of "tiger ammonites", Sphenodiscus. Every year, from the deep levels of the ocean, thousands of females come up to the coast, each ammonite carrying hundreds of fertilized eggs that need to be laid in the shallows, right where Globidens is waiting for them, using its forked tongue to hone in on their location.
“ Tiger ammonites are themselves hunters. The combination of a streamlined profile and a powerful siphon enables them to shoot through water at great speed. But so can the mosasaur. ”
The Sphenodiscus use their own predatory traits (their streamlined profile and powerful siphon) to get to their destination faster and evade incoming threats. Unfortunately for them, Globidens is also quick enough to catch up to them and attack. With its globular teeth, the mosasaur easily crunches through the shells of the ammonites, releasing the buoyant air within its prey, disabling and sinking as many Sphenodiscus as it can instead of taking time to consume each ammonite it catches.
“ Finally, time to tuck in. Globidens may have killed dozens... but even this makes only a small impact on the overall numbers of ammonites. Most of the shoal have survived, and continue on their journey to their spawning grounds. ”
Once the shoals of ammonites have passed through the area, with no more prey to cripple, Globidens feeds on the ammonites it sunk to the ocean floor, effortlessly ripping their fleshy bodies from their shattered shells. Despite the mosasaur having killed dozens of the ammonites, many more make it to the shallows to successfully lay their eggs.
