One of these days we may see a paper come out about this. France, as you may know, contains a dinosaur of truly gigantic proportions (and no, I'm not talking about the Algerian species "Brachiosaurus" nougaredi which seems to have disappeared into a black hole somewhere in Paris). No, this one's a local. A new "titanosaur" known only as the French Monster, or the giant of Angeac, has turned up in the past few years in a bone bed which contains a huge jumble of Early Cretaceous dinosaurs of various sizes - everything from baby abelisaurs to massive hundred-foot sauropods.
Except it's not really a titanosaur, is it?
The French Monster is another one of those legendary or semi-legendary sauropods which should have a name and a formal description, though it's unlikely most of them ever will. Even the pictures evoke something rarely seen in the fossil record.
Mainly the image that sticks in your mind is the very long and oddly blackened right femur, over 2.2m long, with which everyone seems to be "doing the Jensen" though none of them come close to getting it right.
But there is much more to the Angeac-Charente site where this bone was found. There appears to be part of a second femur also recovered at the site, and possible rib fragments. And different individuals of this species have been found, with the fossils in different shades of mineralization.
These teeth have a very basal appearance, and so the labeling of this animal as a titanosaur is unlikely. The teeth could easily pass for Brachiosaur teeth. But there is more than just this first indication what what we are seeing may not be a true titanosaur.
Between brachiosaurs and basal somphospondyli (creatures like Chubutisaurus, Ligabuesaurus, and some would say, Paluxysaurus and Sauroposeidon) and true titanosaurs, there was an amazing radiation of transitional forms. These appear to form at least two major families: Euhelopodidae, and Acrofornica (tall-arches). Both are characterized by extremely long necks, high cervical counts, and bifid neural spines in the neck. The Acrofornica are further distinguished by very tall neural arches, high diapophyses, and nearly no neural spine in the dorsals. They tend to have well-separated sacral ribs, whereas those of euhelopodids tend to be extensively fused together. And whereas euhelopodids (or at least some of them) have procoelous tail vertebrae (anticipating derived titanosaurs!) the tails of acrofornicans revert back to simple amphiplatyan tails, as in basal titanosaurs.
After about 3 years of morphometric comparisons between various elements and overlaps between different specimens (some of them very fragmentary) the following family tree slowly began to reveal itself. This is not a complete family tree of titanosauriformes; only some of the more well-known ones intermediate between brachiosaurs and titanosaurs are included here.
Well it turns out that the French Monster is more like Huabeisaurus than previously realized. Both are closer to Euhelopus and the acrofornicans than to true titanosaurs.
Complicating matters is the fact that some lognkosaurian titanosaurs have a protruding femoral head and a high and prominent lateral bulge, which differs from all other titanosaurs, and converges on that of some euhelopodids and acrofornicans. However the distal end of the femur follows radically different patterns in the two lineages. Here's the comparison of posterior views, you be the judge (not to scale):
Perhaps the biggest oddity of all is how slender the French Monster's femur is. The crushing is mostly from front to back, not lateral. So it really was this narrow. There is a possibility then, that this animal was not even close to the maximum size possible. As an adult it may have been more robust. There is no coracoid or scapula material, so the degree of suture fusion in the shoulders (and thus the animal's maturity) is open to speculation.
As far as I can see it, this dinosaur is most likely a chubutisaur (or whatever Paluxysaurus is, seeing as it's more or lesss totally busted as a purported brachiosaur), but may also belong in acrofornica or euhelopodidae depending on how the cladistics stack up. In any case it's huge and unusual, and maybe soon we may get to see a description and some idea of its overall proportions.