Dinosaur predator size discussion

Well, I've grabbed a few "silhouette" images.  I can't find one that does everything I want.  Most people throw in T. rex and then compare it to large carcharodontosaurs, because they're the biggest.  But I'm more interested in the Morrison animals, and their analogs around the globe at the same time, at least right now.  Actually, what I was most interested in was in comparing the Epanterias specimen to Saurophaganax.

Just a quick refresher.  I've done a MEET THE TYRANTS and a MEET THE CARNOSAURS series of posts; the latter is more important in this particular instance, since Allosaurus, Epanterias and Saurophaganax are all carnosaurs.  I haven't ever done a MEET THE MEGALOSAURS, nor was I planning to, although they're still very important animals in this discussion.  The Morrison is the famous late Jurassic formation of the American West, and it is vast (although most of the formation is underground); famous sites like the Cleveland-Lloyd quarry and Dinosaur National Monument are just the tip of the iceberg.  It stretches from just north of the Canadian border, covers most of Montana, all of Wyoming and Colorado, the eastern half of Utah, the western half of North and South Dakota, parts of Nebraska, the northern half of New Mexico, and corners in Idaho, Kansas and Arizona.  Of course it's both overlaid and underlaid by other formations from other time periods with different fossils too.  At its base, the Morrison is possibly the very latest Oxfordian period of the Jurassic.  It continues on through the entirety of the Kimmeridgian, and ends in Tithonian, although it does not go all the way to the Jurassic-Cretaceous boundary at the end of the Tithonian.  Early Rocky Mountain orogeny (the Nevadan) created conditions not unlike the Andean stratovolcanos along what was the west coast of North America at the time (North America had not completely accreted the island arcs and other terranes that came with the subduction of the Farallon plate under the North American plate, so the west coast was further east than it is today.)  These mountains could have been in the 20,000 ft. elevation range, much like the higher Andes are today.  Much of the rest of the territory to the east was relatively flat, and the Morrison is mostly the drainage basins of rivers flowing from these mountains into the Sundance Sea, an epicontinental extension of the Arctic Ocean that came down through Canada and relatively deep into the US, although it receded and expanded multiple times throughout the Jurassic (no relation to the later Cretaceous Niobrara Sea.)  The Mesozoic was altogether warmer than the climate today, as the Earth's climate has almost always been (so much for global warming) so the northern extents seem to have been marshy subtropical wetlands, while to the south it is much drier, and characterized by sand dunes.  Much of the dinosaur fossils are found in mudstone beds, suggesting that they lived in either riparian or coastal floodplains and that their fossils were buried by seasonal (or probably even more exceptional) floods.

Another interesting facet of the Morrison is that it corresponds in time with several other formations around the globe.  The Lourinha Formation of Portugal is believed to be coterminous with the Morrison in time, and has many of the same animals in it (or very closely related analogs.)  The Tendaguru Formation in Tanzania is also believed to be coterminous, or maybe slightly later (going right up to the end of the Tithonian).  Tendaguru was less marine (no Sundance sea) while the Lourinha was more marine, being right on the coast of the Atlantic Ocean (as it is today.)  The Morrison is also either coterminous or very close to the Upper Shaximiao formation of China; the so-called Mamenchisaurus Assemblage, although the animals there are not quite as closely related to each other as those of the other three formations, they are still very similar.  The Solnhofen Limestone of Germany is also the same age, but as it represents a marine archipelago of small islands, some of the European fauna appears to be different.

All of these formations are characterized by a number of hypsilophodont and early iguanodont grade ornithopods, a wide (even bewildering, as scientists wonder how they distinguished themselves without head-to-head competition) assemblage of sauropods, several stegosaurs, early ankylosaurs, and several therapods, including large carnosaurs, large megalosaurs (maybe including Megalosaurus if it hadn't been replaced by it's close relative Torvosaurus yet), medium sized ceratosaurs (including Ceratosaurus) small coelurosaurs, and even very early tyrannosauroids, often of the proceratosaur family.

So anyway; what are these big therapods?  Who were the biggest bad-boys of meat-eaters in the Morrison?  First off, it's worth noting that we don't know exactly what lived when; although we can detect some variation from early to late Morrison, it's not always easy to correlate differing sites across the formation exactly.  These animals may not have all lived at the same time.  Some specialists believe that Torvosaurus was replaced partway through the Morrison as "largest carnivore" by Saurophaganax, although others suggest that they merely represent differing environmental preferences.  In general, the animals seem to have gradually gotten bigger as the Morrison progressed.  But with the caveat that some of this stuff is speculative, I'm just going to throw them all in to be sure.

1. Ceratosaurus was clearly the smallest of the "large" therapods.  Originally thought to be a hold-out of a much more primitive group (well, technically this isn't untrue) it is now believed that Ceratosaurus actually represents a brave new horizon as close relatives of it ended up becoming the Gondwanan abelisaur family which ruled the meat-eater guild in the late Cretaceous of the south.  He doesn't actually appear in any of the images, but if you look at the allosaur progression below, he'd be about the size of the "Big Al"—the smallest of the listed allosaurs here.
   
   
   
2. Allosaurus is not only the most common, but clearly the most important meat-eater in the Morrison, and they come in various sizes.  The largest is Epanterias which is mostly not believed to be a separate valid genus anymore; although it might be a separate species after all (in which case, it would be Allosaurus amplexus.)  In the image below, you see an average sized Dinosaur National Monument allosaur (green) compared to the specimen that was originally named "Epanterias" but which is now usually considered to be merely the largest allosaur specimen.  Paul and Carpenter do note, however, that it is higher in the Morrison (i.e. more recent) than the type specimen, and therefore could well represent a different animal—although it isn't a good enough, diagnostic set of remains, so it can't be definitively called anything.  Whether or not there's really a late appearing, extra large allosaur or if it's an allosaur relative that deserves its own designation may remain a mystery until something else is found that can clear it up for us.  Although it's tantalizing to point out that Saurophaganax, the largest shown below, is also late in the Morrison (and to date, only found in the south of the formation; New Mexico and the tip of the Oklahoma panhandle.)  If "Epanterias" is non-diagnostic and is also late in the formation, could it be a Saurophaganax from further up north?  For that matter, what exactly is Saurophaganax?  A descendant of Allosaurus or a close relative that coexisted, but was much more rare?
   
   
   
3. The next image below shows the largest specimen of Yangchuanosaurus (beige) from the Shaximiao formation mentioned above next to "Epanterias" (light blue), the largest Torvosaurus specimen (green) (once thought to be a unique animal named Edmarka rex) and Saurophaganax (maroon.) Torvosaurus was also present in the Lourinha under a different species, and seems to be a close relative of the earlier Megalosaurus, which although is famous as the first discovered dinosaur, is also relatively poorly known.  Even more primitive megalosaur relative Marshosaurus was in the Morrison, but not a ton is known about it.  Assuming the remains we have are full grown, it would have been smaller than Ceratosaurus.  It's interesting to see the clear size progression, although for the most part, they're in the same order of magnitude.  These were all fairly large carnosaurs.  The darker blue... well, see below.
   
   
   
4. While Saurophaganax does seem to be the largest Jurassic therapod for which we have direct knowledge, there is a trackway found from the same era in Morocco, which seems to suggest that possibly larger animals yet existed out there.  The illustration above uses this trackway, the 19IGR, and scales up an Allosaurus skeleton to fit the tracks.  In doing so, it gets us to well into the big carcharodontosaur or tyrannosaur range, and possibly even rivals them—although be careful making too much of this, as comparing the skeleton of one animal to the footprints of another that lived very far away in both time and place is fraught with one possibly bad assumption after another.  Plus, for all we know, it could be an early member of some anatomically divergent family, like the spinosaurs, which are found in the same area later in the "mid" Cretaceous.

I should point out yet again, that the Morrison is my favorite dinosaur formation. Not only is it local to America, particularly the American West, which makes it likable, but it's also got that really classic sauropod-carnosaur vibe.  So to really kind of explore what was there, what the biggest and most interesting animals we'd find there might be, is a very specific niche dinosaur interest of mine.  I like the tantalizing possibility that there are animals here as big as any of the carcharodontosaurs or tyrannosaurs of the later Cretaceous, and I like the tantalizing possibility of the largest dinosaur ever living here (Amphicoelias fragillimus) even though it probably didn't.  But we honestly don't know a lot about the upper limits of size for most of these animals.  There are very few for which we have enough samples to say, and the largest, oldest individuals would be rare even in life, much less in the fossil record.  

Can we say definitively that Brachiosaurus didn't grow as big as Sauroposeidon, for example?  Or even Alamosaurus and Argentinosaurus and Puertasaurus?  No, we can't, because there aren't enough specimens, and the specimens we have aren't very complete anyway. (Not only that, the most complete specimen we do have appears to be a subadult.) All we can say with certainty are that 1) they're all in the same order of general magnitude in size, and 2) we seem to have a larger specimen of some of those other three, at least right now.

Even if it was.... there are only 12 specimens known, sometimes only from a single bone, of Brachiosaurus.  It is also only known from the earlier part of the Morrison.  Did they go extinct later?  Or do we just not have enough sampling to verify that they were still there?