Please welcome Brontomerus mcintoshi February 23, 2011

Today is the culmination of a project that I and Matt, and our co-author Rich Cifelli, are very proud of: the publication of the new sauropod, Brontomerus mcintoshi. Go and read the paper — it’s open access, thanks to the good folks at Acta Palaeontologica Polonica.

This project started for Matt many years ago — he first mentioned it to me on 15 May 2004, and we first discussed it in detail in July that year. It’s amazing to realise that very nearly seven years have slipped by since then. But it’s done at last, and Brontomerus mcintoshi is born today!

So, what is Brontomerus, and why should you care? It’s a kick-ass new sauropod — literally — which extends the range of known sauropod morphology and contributes to the growing record of Early Cretaceous sauropod diversity in North America. Plus its name means “thunder-thighs” and sounds kind of like Brontosaurus. What’s not to like?

We know Brontomerus from elements representing about 10% of a skeleton — not much, admittedly, but about 9% more than for Xenoposeidon. Oddly enough, for this blog, the two most informative elements are appendicular: a nearly complete and very weird left ilium, and most of a very nice and rather weird left scapula. We also have a single badly mangled presacral centrum (though even that is interesting), a single gorgeous caudal vertebra, a pair of partial sternal plates, and a bunch of dorsal ribs in various states of repair, of which one, probably the first from the right-hand side, is complete and — you guessed it — weird. (No cervical ribs, though.) There are a few more fragments, but they’re uninformative.

We know that not all this material is from a single animal, because it’s of wildly different sizes: based on the relative sizes of scapula and ilium in Rapetosaurus, we estimated that the animal that contributed the scapula is about three times as long in linear dimension (and so about 3^3 = 27 times as massive) as the much smaller beast that kindly donated its ilium. “But wait!”, you cry: “If the bones are not all from the same individual, what makes you say they’re all from the same taxon?” Patience, young padawan; we will discuss this at length later this week (hereafter PYP;WWDTALLTW).

Because the ilium is the most distinctive of the bones, we nominated it as the holotype. “But wait!”, you cry: “If the ilium is from a juvenile individual, surely it’s not suitable to be the holotype?” PYP;WWDTALLTW.

We diagnosed Brontomerus by five autapomorphies of the holotype ilium: preacetabular lobe 55% of total ilium length, longer than in any other sauropod; preacetabular lobe directed anterolaterally at 30° to the sagittal, but straight in dorsal view and vertically oriented; postacetabular lobe reduced to near absence; ischiadic peduncle reduced to very low bulge; ilium proportionally taller than in any other sauropod, 52% as high as long. What does all that mean? PYP;WWDTALLTW. (Wow, that acronym is turning out to be more useful than I expected.) In briefest summary, it’s nothing like any other sauropod ilium I’ve ever seen; and that’s not because it’s from a juvenile.

Brontomerus has had a slightly odd publication history: it was inadvertently published as an “accepted manuscript” on the Acta web-site on 3rd January, whence it was quickly picked up by the Dinosaur Mailing List. In a matter of hours, a Wikipedia article appeared, along with mentions on a surprising number of web-sites: as I write this, four days before publication, Google has 60 hits for “brontomerus” including pages from Germany, Holland, the Czech Republic, Poland and Argentina. But the Acta people were very fast to take down the accepted manuscript once I’d pointed out that the name was being accidentally leaked, and I was able to have the Wikipedia article deleted pretty quickly too. It seems that, against all expectation, the genie was pretty much put back in the bottle.

As if that weren’t enough failage to be going on with, I (Mike) accidentally posted this very article a couple of days before publication. D’oh! (WordPress’s Publish button is terribly easy to hit.) Again, we scrambled to try to limit the damage. I was able to un-publish the article itself, but by then it had already gone out by RSS, so some of you might have seen this post before in that earlier form. (This is of course the reason for the I’m Stupid post.)

All the rushing around to shut down premature announcements was, of course, intended to keep the powder dry for today; and we heartily encourage all of you who’ve been wanting to to talk about Brontomerus to do so now!

There is a lot more that we could say — and will say — about Brontomerus. We have a bunch more posts planned for later in the week, as noted above. Those of you who can’t wait will of course read the paper, but may also find yummies on the press-pack page or the unofficial online supplementary information.

References