First real entry in quite a while! Should be able to get some relatively stable posts in over the next month or so, then it's back to 'variably whenever possible.'
Since the group's discovery in the Bahariya Oasis of western Egypt in the early 1900s, spinosaur feeding habits and ecology have been something of an enigma for paleontologists, partly due to their truly bizarre crocodile-like snout and teeth, and greatly amplified by their absolute rarity within the fossil record (the fascinating history of spinosaur discoveries is something that I'll deal with in a later post, likely when I cover some of the research I'm currently engaged in!).
The holotype of Baronyx walkeri, a spinosaur found in the Early Cretaceous of Europe (and, depending on the paleontologist you talk to, Africa) was preserved with gut contents comprised of acid-etched fish scales (belonging to an animal called Lepidotes) along with a small skeleton of a juvenile iguanadon (one of the herbaceous creatures found in these ancient river and lake systems). The idea that spinosaurs were partly piscovorous (fish-eating) in nature was first seriously postulated in 1984 based upon the strange shape and form of their jaws, and this possibility was further supported when it was realized that Baryonyx was in fact a spinosaur (for a while there was some contention about how it fit into the Dinosauria, with some initially feeling that it belonged in a separate family entirely).
Just how much spinosaurs may have utilized fish as a part of their diet is currently unknown, largely due to a great need for more discoveries and further ecological studies (both modern day and ancient). Past research has shown a remarkable degree of similarity in the skulls of Baryonyx and the modern day gharial crocodile, but too little is known to draw many conclusions at this current point in time. We paleontologists are forced to work with what we have, and more often than not we have is perpetually less than what we would like.
;-)
(to give an idea of how tremendous an issue this is for those who work on the group, at the current point in time there are over 50 known partial Tyrannosaurus skeletons--of the four (possibly 3) genera for which spinosaur skeletons are known, there are at the most one partial skeleton and assorted bone fragments for each)
Though extremely rare, there is some concrete evidence of spinosaur feeding beyond that of Baryonyx. In 2004, Eric Buffetaut and David Martill described a series of vertebrae belonging to a pterosaur found in the Santana Formation of Brazil. The vertebrae, on their own, would seem to be nothing particularly spectacular (though when one truly starts to contemplate the odds against their existence, any fossil is remarkable).
However, when preparation of the vertebrae began, they found something unexpected: embedded in the frontmost of the three was a large spinosaur tooth, very similar in form to those previously found in the area.
Though certain aspects will always be lost to the ages, we can at least surmise a few details of the feeding event. Because none of the bones or tooth show any degree of acid wear, it likely wasn't swallowed by the spinosaur in question. Though it's certainly possible the pterosaur was attacked (either in low altitude flight or on the ground), it seems more likely that the carcass was scavenged.
Though much remains to be discovered about this fascinating group, the little we do know paints a fascinating tale of a group of theropod dinosaurs whose known distribution spans a minimum of 60 million years of deep time, and whose dispersal took them through at least four continents. Though we do have some skeletal remains, the majority of spinosaur fossils consist of isolated teeth, and any traces of these animals at all are worthy of awe.
Cheers!
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All photographs are taken from their original publications excepting the first two, which were taken from the Wikimedia Commons and here.