Globidens was a mosasaur, a kind of meat-eating marine lizard, that was about twenty feet long from snout to tail. Fossils of different species within the genus have been found in the United States, Morocco, Angola, and Indonesia which flourished throughout the late cretaceous period from 85 to 66 million years ago. The genus name, Globidens, translates to "Globe Teeth" because of its unusual sphere-shaped teeth.
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| Globidens phosphaticus cracking the shell of an ammonite. Watercolor life reconstruction by Christopher DiPiazza. |
Globidens is most known for its teeth, which were unlike those of any other mosasaur, most of which had cone-shaped teeth, like Tylosaurus, or blade-like teeth, like Platecarpus. Globidens, on the other hand, had teeth that weren't sharp at all, but had wide bulbous crowns. The skull looks like this beast had a mouth full of big, round mushrooms growing out of its jaws! These blunt, teeth were ideal for crushing hard objects, leading paleontologists to hypothesize that it specialized in hunting prey with shells, like mollusks, crustaceans, and possibly even turtles. In addition to the teeth, Globidens had a robust lower jaw, which would have been controlled by enormous muscles in life, giving it an extremely powerful bite. Paleontologists suspect it may have had one of the strongest bite forces of any mosasaur, despite not being the largest-bodied member of the family. After the discovery of it's teeth, a Globidens skeleton with shell fragments of large prehistoric bivalves in the stomach cavity proved the already strong hypothesis of its preferred food.
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| Skull of Globidens phosphaticus, which lived in what is now Angola, on display at the Smithsonian National Museum of Natural History in Washington D.C. |
Other than the jaws, Globidens had other notable features. Its snout was relatively short for a mosasaur. A shorter snout, allows for a higher concentration of pressure when biting down, so this was likely another adaptation that supported its strong biting pressure. The eye sockets were large and housed wide scleral rings (a disc-shaped bone that supports the eyeball in life) which supports the idea that this creature had good vision, and likely could see well in low light, like the seafloor where much of its prey would have dwelled. Lastly, Globidens' bones were dense which this is another adaptation of an animal that wants to be able to dive deeper underwater. In addition to wanting to dive into deeper waters to find its preferred food, Globidens would also be avoiding other species of mosasaurs that it shared its habitat with that were even larger than it, like Tylosaurus, which was more of a surface predator.
Amazingly, Globidens wasn't the last lizard to evolve strange round teeth for crushing shells. A kind of lizard alive today, called a Caiman Lizard (genus Dracaena) native to central and South America, has teeth almost exactly like those of Globidens, just on a smaller scale, which it uses to crush the shells of snails. Even more interesting is the Caiman Lizard is from a totally different family of lizards from mosasaurs, so the shell-crushing teeth evolved convergently. Evolution is amazing!
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| The modern day Caiman Lizard independently evolved similar feeding adaptations to that of Globidens because it also eats hard-shelled prey. (photo credit: Reptiles Magazine) |
That is all for this beast! Can you think of any other animals (alive or extinct) that have similar crushing adaptations? As always feel free to comment below!
References
LeBlanc, Aaron; Mohr, Sydney; Caldwell, Michael (2019). "Insights into the anatomy and functional morphology of durophagous mosasaurines (Squamata: Mosasauridae) from a new species of Globidens from Morocco". Zoological Journal of the Linnean Society.
Martin, J. E. and Fox, J. E. 2007. Stomach contents of Globidens, a shell-crushing mosasaur (Squamata), from the Late Cretaceous Pierre Shale Group, Big Bend area of the Missouri River, central South Dakota. Geological Society of America Special Papers, 427:167-176.
Massare, J. A. 1987. Tooth Morphology and Prey Preference of Mesozoic Marine Reptiles. Journal of Vertebrate Paleontology, 7(2):121-137.
Russel, Dale (1975). "A new species of Globidens from South Dakota, and a review of globidentine mosasaurs". Fieldiana Geology. 33 (13): 235–256.
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