Name Meaning: Abel’s lizard
Geologic Era: Cenomanian stage (100-93 million years ago)
Location Discovered: North Africa (Morocco)
Range: Modern North Africa?
Extinction: 95 million years ago?
This is a very nicely preserved tooth, with serrations still plainly visible. That being said, I’m sure that this is not a dromaeosaur (raptor) tooth. Several features lead me to believe this. First, it lacks the curvature I would expect to see on a dromaeosaur tooth. This tooth is pretty straight, and looks like it would not have much curve even if it were complete. Second, Deltadromeus, despite its name, is not currently considered to be a dromaeosaur. Rather, it appears to be a ceratosaur, and a rather primitive one at that. Third, Deltadromeus lived 95 million years ago. I do not know if this is a misprint on the label, or a mistake. This tooth is also very small to have come out of something the size of Deltadromeus (6 meters long). Even though no recognized skull material exists for Deltadromeus, I would expect the teeth to be somewhat larger than the one below.
I cannot make a species identification on this tooth. What I can say with some degree of comfort is that it appears to be abelisaurid. This was a rather unusual group of theropods that have been found in Africa, South America, and Europe, and India. Abelisaurs are related to ceratosaurs, if somewhat distantly. What sets abelisaurs apart are two factors: their skulls and their forearms. Since I cannot make a species identification, I have chosen Majungasaurus as my example of a typical abelisaur. This animal lived around 30 million years later than the animal the tooth came from, but most abelisaurs were similar in appearance, so we can make some assumptions on appearance based on a close relative.
Abelisaur skulls are generally much shorter and taller than the typical theropod, giving an almost bulldog-like appearance. Many also possessed ornamentation on the skull, ranging from horns to bumps and ridges. The function of these ornaments is not known, but could have been used for courtship or identification. Abelisaurs also have somewhat thinner teeth for the size of the skull, generally being labiolingually compressed. What this means is that the teeth are more blade-like, compared to a human’s tooth.
The second feature that makes abelisaurs unique is their very tiny forearms. They were proportionately shorter than even Tyrannosaurus rex, almost to the point of looking completely nonfunctional. The finger bones of Majungasaurus were fused, meaning the hand was probably immobile. The bones of the rest of the arm are comparatively heavy, if short. Whatever the forelimbs were used for, they were unlikely to be able to grasp items.
Incidentally, our tooth does bear some resemblance to a fragmentary abelisaur maxilla from around the same time period. The article detailing this tooth, Record Of Abelisauridae (Dinosauria: Theropoda) From The Cenomanian Of Morocco, is available if you would like to read it. Our tooth matches up nicely in size and appearance to the referred specimen. It is possible that they are from the same type of animal, though the maxilla has not yet been formally described as a species.
Full Skeleton:”Majungasaurus crenatissimus, ROM” by D. Gordon E. Robertson – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Majungasaurus_crenatissimus,_ROM.jpg#/media/File:Majungasaurus_crenatissimus,_ROM.jpg
Skeletal Diagram:”Majungasaurus crenatissimus skeleton” by Jaime A. Headden (User:Qilong) – http://qilong.wordpress.com/2011/10/19/walking-sledgehammers/. Licensed under CC BY 3.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Majungasaurus_crenatissimus_skeleton.jpg#/media/File:Majungasaurus_crenatissimus_skeleton.jpg
Life Restoration:”Majungasaurus BW” by Nobu Tamura (http://spinops.blogspot.com) – Own work. Licensed under CC BY 2.5 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Majungasaurus_BW.jpg#/media/File:Majungasaurus_BW.jpg
Journal Reference:Mahler, L. (2005). “Record of Abelisauridae (Dinosauria: Theropoda) from the Cenomanian of Morocco”.”. Journal of Vertebrate Paleontology25 (1): 236–239.