Giraffatitan's head is just WEIRD.

Posted by Nima On Monday, January 4, 2016 23 comments

The Jurassic weirdness continues!

The last post on Giraffatitan focused on the torso, and how it had often been inaccurately restored. But I didn't appreciate just how strange this animal's spine was until I got down to business, and started articulating images of the bones to see exactly how the centra and zygapohyses actually fit together. In the process I discovered that the actual 12th dorsal, though published by Werner Janensch in his 1950 monograph, was never scaled or reproduced in the mounted skeleton, nor was it used by any of the previous artists who had done skeletals of Giraffatitan. Greg Paul, Scott Hartman, Stephen Czerkas and or course (ironically) Janensch himself had left it out of their full-body skeletals. In addition it appears that they all changed the bizarre proportions of dorsal 9 - which has a relatively compact neural arch but a hugely elongated centrum - in order to make it fit in sequence such that the spine was more or less straight. But D9 (as heavily restored in plaster by Janensch anyway) has to be tilted upwards by around 40 degrees in order to have the short hyposphene reach far back enough to properly lock into place with D10, which indicates that their angle of articulation is anything but straight, and that D9 probably fits into the dorsal column like an upward-pointing wedge of sorts.

The result is a bizarre double-kink in the lower dorsals which both reinforces the lower back and makes the torso shorter and more compact. The fact that D10's centrum (again, going off of Janensch's restoration) has a condyle that is tilted up and back further reinforces this tilted angle of articulation demanded by the hyposphene of D9, as does the resulting snug fit of the neural spines of D9 and D10, without an excessive gap between them. Oddly Janensch doesn't carry over the weird shapes of both bones to his own full-body skeletal, though he does illustrate them individually in his paper, odd shapes and all, just it as his team restored them.

But this is far from the only strange thing about Giraffatitan that has been overlooked for decades.
Nearly every part of its body turned out to have unexpected features not included in ANY previous restorations. And one of the most commonly oversimplified, blurred, or just flat-out distorted parts in many restorations is... the head.

That's right, Giraffatitan's head is truly weird. A marvel of natural engineering and stress distribution through struts that in some places appear thinner than a human finger. The skull was light and hollow, yet could get up to a meter long (estimated size for adult individuals such as HMN XV2). And yet it was packed with big teeth resembling a cross between spoons and railroad spikes, built to crunch through hard branches high in the ancient conifers.

As you can see in the above picture, the skull is partially reconstructed with plaster, including one of the eye struts and the region just below the base of the nasal crest.

But there are in fact four skulls in existence. At least that is how many Janensch mentioned.

Three of them are missing a great deal of material, but the most well-known one, HMN t1, is nearly complete. We know this skull very well. Anyone who has seen photos of the Berlin mounted specimen (mostly based on HMN SII) has also probably seen this t1 skull, which is actually from a smaller individual. A scaled up cast of this skull was mounted on the skeleton itself in 2007, replacing an older crude sculpted skull.

The skull you see at the feet (or rather hands) of the Giraffatitan in these photos is actually only a cast of HMN t1. The real skull is stored in a museum vault and is (supposedly) off limits to the public.

Now at one point this face was cute.

Then it got fossilized and crushed. A few pieces such as the upper part of the eye socket are missing or broken. The upper jaw is partially collapsed in the middle, causing the sides of the maxillae to turn up and flare out. The sides of the jaws are thus artificially bowed out sideways. This led Dr. Matt Wedel to comment that it looks like a toilet seat today. Honestly I feel sorry for this poor creature. But sauropod skulls being delicate and easily smushed is a fact of life. Some of them had such loose connections between the skull bones that they actually dislocated during fossilization!

The crushing is easier to see from the side:


The snout has been flattened in the center, and to some extent the top of the nasal arch has also been squashed. Also notably, the teeth appear artificially long because they have slipped out of their sockets (or been pushed out by inclined crushing during fossilization) and the roots are visible. The skull itself had to be glued together from many fragments, and when first excavated was a bit of a jumble, like this:

Overall I would say given the shape the bones were in, Janensch and his staff had done a pretty good job of rebuilding the skull. Some of the skull elements were actually warped in the fossilization process, which makes sense as the bone layers are extremely thin.

But the trickiest aspect of this whole story is that there are a number of different ways the skull could have looked in real life. The crushing was uneven, which means the left and right sides of the skull appear rather different, with the right upper jaw considerably flatter than the left. Also we may be dealing with the possibility of ontogeny, that the skull of Giraffatitan would have changed shape with age and maturity. This is usually not a big concern in sauropods, as they do not develop any horns or massive butting surfaces on their heads, but that doesn't preclude the possibility that the shape of the head itself changed with age.

In trying to reconstruct a profile of Giraffatitan's head, I had to get around a few things.

First, the specimen I'm using for the skeletal is HMN SII, so the skull has to closely match the S116 skull, which is from the same or similar-sized individual. This skull has somewhat different proportions to some of the bones than HMN t1, although part of this may be due to either ontogeny or sex of the individual. That said, I wanted to create a reconstruction that adequately combines the most consistent aspects of all the skulls and eliminates crushing so that we can see the "ideal" morph of how SII's head would have looked on the living animal.

This was going to be a literal headache. It didn't help that Janensch and other early authors had themselves illustrated the "generic" Giraffatitan skull a number of different ways, with varying proportions.

So in brief, below, is the progress of morphs, trying to get the uncrushed proportions just exactly right (with a similar but shorter process for the referred Felch Quarry skull of Brachiosaurus - also an immature specimen - shown below it.)

By comparison with many photos from different angles and all the known Janensch engravings, gradually a more complete picture emerged. And so with a few remixes for different specimens, ultimately the conclusion was that the typical Giraffatitan head - hypothetically a mix of t1 and S116 - would look as follows.

So after about 30 variations and tweaks, this is what we've got. Overall a LOT better than the ugly derpy overbite version you see in most books and websites (basically a caricature of the crushed t1 skull), or for that matter the oversimplified blurry Greg Paul version which is sorely lacking in detail and deviates substantially from the fossils in several ways.

Pauly DERP that you can get sued for imitating. 

So yes, Giraffatitan - when uncrushed - has a rather different head than we've long been lead to believe. Feel free to comment below.


Degio said...

That's the stuff!
I really liked your Giraffatitan's dorsals post and love this one...
I wait for an updated version of your G.brancai in future!

bricksmashtv 2 said...

I'm curious, when you update your current Giraffatitan skeletal, will you be updating it with the HMN XV2 skull or the HMN SII skull?

bricksmashtv 2 said...

I'm curious, when you update your current Giraffatitan skeletal, will you be updating it with the HMN XV2 skull or the HMN SII skull?

Nima said...

@ Degio: Thanks! I am close to finishing it. It will be HUGE!

@ bricksmashtv 2: I will use the HMN SII/S116 skull, with a few modifications to make it more like the actual S116 material (this version is more of a composite). The XV2 skull is speculative, no skull material has been found for XV2 but this is just what I think it - or another adult Giraffatitan - might have looked like.

However I may use the speculative skull for another picture of different individuals of Giraffatitan comparing the sizes.

Scott Hartman said...
This comment has been removed by the author.
Scott Hartman said...

As I said on your last post, your dorsals thing isn't really true. Janensch (and his illustrator's) D11/12 (which is your D10/11) has centra that are mostly restored, so their shape is simply NOT KNOWN. You can't argue about how accurate their illustrations are, because in this case it's based on missing data, and thus the restored illustrations of them with weird-looking centra doesn't mean anything.

The skull stuff is interesting though.

Nima said...

@ Scott Hartman

This may be true, but also from what I've seen of the restored vertebrae themselves (which seem to match the illustrations very closely) the job done by Janensch does appear to have been rather conservative in terms of how much bone he restored, hence why the shapes come out weird rather than more "average" and overfilled like much of Jensen's brachiosaur material... or his reconstruction of a Supersaurus neck vertebra (*ick*).

Also there is the issue of D9, where the neural arch (apparently not restored) is unusually far forward and the centrum is apparently in much better shape, and does look unusually long and the cotyle angle is also rather odd... which only makes sense if the entire vertebra tilts up at a steeper angle so its postzygs can actually couple with D10s prezygs. And this odd kink actually fits very well with D10 having a condyle that seems to be "leaning back" more than normal. And then we have D11 which has a taller neural spine and *appears* to have a larger cotyle than D10, something unusual in brachiosaurs to say the least.

It would be wrong to say that the shape of the centra of D10 and D11 are the only weird things about Giraffatitan's dorsals. They are just one of many. There is also a smaller specimen whose D12 is known, and looks just like the one from Fund no. 8 only smaller, so the angle or articulation with the vertebra in frount would have likely been similar to what I depicted here.

It is largely educated guesses at this point, but I am fairly confident my revision of my own Giraffatitan skeletal - dorsals and all - will be a good step in the right direction of less "generic" brachiosaurs. schematics.

Scott Hartman said...

Actually quite a bit of the centra and most of the neural spine of D9 are also missing - there's no way to be sure about its shape in lateral view either. And FWIW I highly doubt Janensch was the one doing the restoration, that most likely was a preparator whose name has been lost to time now (the illustrations simply reflect the final restored version of the bones...but not the sculpted versions that were mounted, which as you note are very different from the fossils...but beware Janensch's whole-body measurements, as they are based on the mount, NOT on the more conservative restored elements).

Nima said...

@ Scott - that's interesting, the vertebra that I label D9 (the one with the super long centrum) shows what looks like a pretty complete neural spine in the paper, no dotted lines like with the edge of the centrum... but not having seen the bone in person, I can't comment on how the artist drew it.

No worries about the whole body measurements, I know the story there... never trust a published body length you can't verify from the actual fossils. The old sculpted mount was so different from the actual bones it's a shock Janensch even used it in his published skeletal. I just restore as much of the skeleton based on the fossils and their individual measurments as possible, and cross-check the scaling, correct for crushing and erosion just enough so the bones articulate properly, and then however it turns out, I use my 4m scale bar to measure the final body length.

At least in theory that's what's supposed to happen :)

Anonymous said...

Jens Kosch post Part 2:

Other cranial material includes:
- a single frontal from the site St (current collection number unknown t me)
- Y-1 (current collection number unknown to me):
occipital condyle, basioccipital, basisphenoid (partial), exoccipital (dext, sin), supraoccipital, prooticum (dext, sin), orbitosphenoid (sin partial), laterosphenoid (dext, sin, both partial),

I have absolutely no idea where the functional teeth in the left maxilla MB.R.2181.4 on plate X of Jenensch (1935-36) come from. They are obviously not the functional teeth of the left maxilla of this individual (see MB.R.2181.23.9).

I really like you restorations, Nima. Especially the nasal and the nasal processes of premaxilla. However, I think some of your morphs have to much of a “chin” on the rostral portion of the dentary (as in Camarasaurus). Still, the “typical” results for the different growth stages are good in this regard.

I find the labelling of MB.R.2223 (t1) and MB.R.2180 (S 66) as juvenile a bit unfitting. There is a size gap between those two with MB.R.2180 being considerably larger than MB.R.2223. Using the definitions of Hone et al. 2016 I would consider both to be subadult, whereas MB.R.2181 strdells the line to be considered adult (although certainly not fully adult by osteological fusion standards).

All in all, great work though. I can't wait to see the new complete skeletal restauration of Giraffatitan.

Hone DWE, Farke AA, Wedel MJ. 2016 Ontogeny and the fossil record: what, if anything, is an adult dinosaur? Biol. Lett. 12: 20150947.

Janensch, W. 1935-36, Die Schädel der Sauropoden Brachiosaurus, Barosaurus und Dicraeosaurus
aus den Tendaguru-Schichten Deutsch-Ostafrikas. Palaeontographica 2 (Suppl. 7) 1. Reihe II. 147-

Anonymous said...

i, I am Jens Kosch, now in the Zanno lab at Raleigh, NC, but previously I was at FU-Berlin and I wrote my Masters Thesis on the dentigerous bones and the dentition of Giraffatitan.

First of all: I really appreciate the work done and the the way a lot of the steps are presented in this post, Nima.

But I don't like the fact that you ignore the currently valid collection numbers of the individual specimens. You simply use Janensch's designations.
All the collection numbers are HMN are now MB and for the fossil non avian dinosaurs it is MB.R. (the Museum für Naturkund has no further connections to the Humbolt University anymore. Also see:
The specific collection numbers are:
- MB.R.2180 (SI of Janensch and other scources (e.g. Taylor 2009, Paul 1988), the head is also called S 66 in Janensch 1935-36). This one has the following cranial bones preserved: Parietal (sin + dext), frontal (sin + dext), nasal (dext), lacrimal (dext., sin partial), squamosal (dext), pterygoid (sin), ectopterygoid (sin), palatine (dext, sin partial), premaxilla (sin), maxilla (dext, sin), dentary (dext, sin), angular (sin), surangular (dext, sin, both partial), splenial (sin), coronoid (dext), occipital condyle, basioccipital, basisphenoid and parasphenoid, exoccipital (dext, sin), supraocciital (partial), prootic (dext, sin), orbitosphenoid (dext, sin), laterosphenoid (dext, sin), quadrate (dext, sin partial),

- MB.R.2181 (SII of Jannensch and other sources, the head is also called S116 in Janensch 1935-36). This one has the following dermatocranial bones preserved:
Prefrontal (dext), postorbital (dext, sin partial), postfrontal (dext, sin partial), jungal (dext), squamosal (dext partial), quadratojungal (dext, sin?), pterygoid (dext, sin), ectopterygoid (dext, sin), palatine (dext sin, both partial, just lateral parts), premaxilla (dext, sin), maxilla (dext, sin), dentary (dext, sin), angular (dext, sin partial), surangular (dext, sin), splenial (dext, sin), coronoid (dext, sin), prearticular (dext, sin), quadrate (sin), articular (dext, sin), ca. 20 plates of the scleral ring

- MB.R.2223 (skull t1 of Janensch)

Large portions of the right maxilla MB.R.2181.3 were heavily reconstructed with plaster. It is kept as a single unit by three metal rods and connected to the premaxillae MB.R.2181.1-2 by three other metal rods.

Isolated tooth rows (“dentures”) are known from both individuals (MB.R.2180 and MB.R.2181) and a few others
- MB.R.2181.23.9 (functional teeth of left maxilla)
- MB.R.2180.20.12 (functional teeth 1-6 of left maxilla and functional teeth 4-8 of left dentary)
- MB.R.2180.21.7 (functional teeth, likely dentary dext 1-2 and dentary sin 1-3
- MB.R.2182 (functional teeth, likely maxilla sin 3-7)

- MB.R.2390 (=WJ4170, also mentioned as WJ 1111 on page 154 of Janensch 1935-36)
This is a “denture”, purely isolated teeth in syn vivo arrangement, not a bone!
From the same site also comes a single prefrontal.

End of the first part of the post (the second part is for unknown reasons above and dated earlier ...)

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