Is Skorpiovenator a real dinosaur?
Skorpiovenator was named in... 2008 and it is most definitely a real dinosaur. This incredible Late Cretaceous Argentine abelisaurid is known from a spectacularly preserved skeleton missing only parts of the tail and its arms. The name means "scorpion hunter," so named "...because of the abundance of living scorpions moving around the excavation". Yikes!
At around 20' long and over 3,000 lbs, Skorpiovenator was a medium-sized abelisaur. The largest currently known abelisaurid is Pycnonemosaurus at 30' long and considerably heavier.
The abelisaurs, that we know of, never attained the massive size that tyrannosaurids and carcharodontosaurids
attained. Yet, in the southern hemisphere, the carcharodontosaurids go extinct around 90 million years ago, while the abelisaurs make it right up to "The Last Day".
Abelisaurs are wildly successful Gondwanan theropods known from all over the southern hemisphere with new taxa being named every hear. Skorpiovenator lived alongside the theropods Mapusaurus, Taurovenator, Ilokelesia, Gualicho, Tralkasaurus, Aoniraptor, Ovroraptor, Huinculsaurus, the sauropods Argentinosaurus, Choconsaurus, Cathartesaura, and Limaysaurus, and unnamed iguanodonts.
Abelisaurids are famous for two amazing features, their bizarre arms and their crazy cool skulls. How much of the Skorpiovenator arm complex exists? The field photo and available cast do not show any evidence of a shoulder blade, nor any of the arm bones themselves. The descriptive text says, "...lacking the right forearm...", implying the left arm is present, however, the accompanying skeletal illustration shows only one bone drawn in the left arm, either the radius or the ulna. Character 88, "Forelimb zeugopodium composed by short and robust radius and ulna", is marked as a '1', meaning at least one of the forearm bones is present. However, the character reads "radius and ulna", implying both are present, which is not supported by the illustration. Character 90, "Distal end of radius/ulna...", is marked with a question mark, suggesting whatever forelimb bone(s) collected are either missing the distal half or were not prepared for the study. There is no other mention of the forelimb in the text. No subsequent papers have mentioned its arms either. The missing components of the tail were touched upon in the original description but for reasons unknown, nothing else was said about the shoulder or arms. Though I hope the left arm is complete and simply needs preparation I am of the opinion it doesn't exist other than a fragment of a forelimb bone (Tracy Ford's Paleofiles lists it as an ulna). One of the best abelisaurid forelimbs discovered thus far is that of Majungasaurus. It has a gigantic shoulder blade for such little hands. The four fingers, if one can call them that, consist of metacarpals (the wide, flat part of your hand), then a 1-2-1-1 phalanx count. This means it had only 1 "finger bone" (the first bone you can see at the base of your finger), then 2 bones on the next finger over, then the remaining fingers had only one finger bone each. It may not even have had claws! What the heck they were doing with stumps I have no idea. The entire arm was short, making T. rex arms seem kingly. Maybe they slap-fought for dominance? Were they somehow used for display to attract mates? Skorpiovenator's completeness led me to hope an arm was present but, alas, it seems not to be the case.
Skorpiovenator's skull doesn't have the horns of Carnotaurus, however it does have a very rough face, with lots of texture. It is possible the skull was covered in thick, extremely robust , bumpy scales. The scales may have even been like armor, they were that thick!
The skull photo in the original publication reminded me of the marine iguanas (Amblyrhynchus cristatus) I studied in the Galapagos. On numerous occasions, I observed them fight one another. They pushed their bumpy heads against one another, the long toes and toe claws grasping for purchase on the sand and rocks. I marveled at one battle where the smaller competitor, to me, won the match for it was able to push the larger one around using better technique (or perhaps just was lucky with the substrate). The larger male at one point was rolled over and took the opportunity to bite the smaller male. The head butting pushed the larger male's head repeatedly into rocks, resulting in a bloody lip. Yet, for reasons I know not, the fight simply stopped. Ah lizard culture :-)!
Perhaps Skorpiovenator used its skull in a similar fashion, slow-speed headbutting that relied upon its powerful legs (those tiny arms wouldn't be able to do anything!) and rigid neck region to push an opponent back or even knock it down where it could kick and bite if the loser didn't acquiesce.
Or, perhaps they used their heads to side-strike opponents like giraffes do today. The bumpy-textured skull was robustly built, keeping the brain safe, and the neck bones are quite rigid, giving it. Such bashing would be quite the sight to see!
Abelisaurid tails have some of the most beautiful caudal ribs one will ever see! In fact, the way they are built, it is quite likely the base of the tail was quite inflexible. This tracks with modifications in the dorsal and cervical vertebrae, suggesting the vertebral column was rod-like and fairly inflexible.
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