In the last post on Giraffatitan, we focused on just how strange the head is, and explored some hints about the ontogeny of the animal's face.
However after a deeper exploration of the actual fit of the skull bones, dumping all stylizations and previous conventions of illustrating this iconic brachiosaur, a few things started dawning after being hidden and dissociated for mission of years. Giraffatitan is even weirder than I thought last time.
Not that it's easy to tell from three fragmentary skulls and a fourth that, while largely complete, has undergone massive distortion from crushing. That skull, HMN t1, which was reconstructed in the 1930s, was cast in fiberglass recently by Research Casting International (RCI) in their 2007 revamp of the Humboldt Museum's dinosaur hall - one that was long overdue. The cast was scaled up by around 15% or so on a 3D printer to match the body of the larger HMN SII, whose associated (and far less complete) skull SMN S116 was significantly larger than HMN t1. Apparently an earlier cast of HMN t1 existed as far back as the 30s and stood in a glass case in front of the old mount.
From the sides the distortion is more apparent.
Left: moderate vertical crushing in the upper jaw. Right: more severe crushing in upper jaw, including lateral splaying of the lip region and artificial progmathism and splaying of the premaxilla and snout tip. This actually results in a different observable lip line on one side than on the other. Of course the teeth are seriously falling out of their sockets here. They did not extend out that far in life.
Another problem is that the warping and crushing is in more than one direction, so that you are literally getting a different face looking at it from different angles. Judging the ideal "shape it should be" from a few photos at odd diagonal angles is asking for trouble. So how do you reliably uncrush this thing evenly, without photographic distortion on top of physical distortion, and get an idea of what the skull originally looked like?
Well you can go based on photos by amateur photographers from slightly off angles in a small cramped basement room, or go by professional drawings from the past, or use published photos. I prefer published photos from the paper, but for Janensch (1935) these are rather old and grainy, and I assumed a better result could be had from bigger, newer, sharper full-color photos, or from supposedly well-measured professional drawings of the skull in its hypothetical pristine form.
Initially the design for the Giraffatitan skulls in the skeletal redux went like this:
The first version was on the old Giraffatitan skeletal I posted. The drawing I used for inspiration (artist unknown) was rather grainy, and I ended up exaggerating the proportions and the shape of the teeth somewhat. On a 1950s brachiosaur drawing this head may have looked okay, but the shape of the nose and the jaws just seemed contrived based on what I had seen of the skulls - and the snout was a bit too beak-like in profile.
The second version came to me after hunting down a photo from a not-quite-profile angle on the web. Upping the contrast and then editing out the further premaxilla yielded a good snout profile, and this time with the nasal arch editing looking much better. The nasals of HMN t1 do appear a bit flattened so will need to be edited each time. Here the angle itself helped counteract the appearance of the crushed snout that plagues ride-view verbatim restorations.We end up with more robust jaws and a more believable gumline for a brachiosaur. But still, this image was based on a photo from an angle and so necessitated some distortion due to perspective as well.
Out of frustration some may resort to simply taking Janensch's drawing of a "de-crushed" composite skull as the true path. The problem here is that Janensch made a glaring error - the snout in his engraving is far too long. I shortened it a bit, but even then this version seems to shrink the nose and the rear skull and overgrow the snout and jaws. None of the Giraffatitan skulls have these proportions, they all reflect proportionally shorter jaws than that.
Finally a real edge-on profile photo of the right side of the skull surfaced on the internet. It was poorly lit and grainy, but it was the best profile available at the time - the picture was taken from some distance, so no "fish-eye" shape distortion, and also no angle distortion. Of course the crushing was still there, but now there was no extra visual illusion on top of it to undo. Rapidly this became a line-drawing, but then the flattened upper jaw and prognathic snout tip had to be corrected. With the jaws deepened to make up for crushing and possible erosion, the teeth back in their sockets, and the back of the skull at its proper proportions, this fourth attempt looked like the answer.
Based on it, I crafted the previous incarnation of the ontogenic sequence of Giraffatitan skulls, with some more modification.
Unfortunately, this assumed the other skulls were more or less identical to HMN t1. And it also utilized an excessive amount of morph change from the original despite compensation for crushing being necessary. A better photo was needed. Actually several better ones were needed for these skulls turned out to be unique individuals with different faces.
Looking closer at photos of the skulls, it became clear that this little happy family just looked wrong.
Pretty messy, pretty horrible. But let's clean up the process a bit...
|How to draw accurate Giraffatitan skulls without going insane|
It is often helpful to invert colors in MS Paint and work "in negative" - it allows you to avoid distracting and potentially artificial structures and visual illusions caused by too many changes between black and white regions. Now the process of following the skull photos much more closely than in the last set of reconstructions becomes very simple. The published photos from Janensch (1935) are rather grainy compared to more recent ones, but at least they were taken professionally, from proper lateral angles at a good distance, and thus can be used to make a skull recon while both removing crushing and avoiding the pitfalls of having to worry about camera angle distortion from amateur photos of the skulls (or of t1 anyway, since the other skulls have never been reconstructed or cast, and are off limits to the public). Reversing one side of the skull and overlapping it in Paint and Pixia allows you to get an idea of the relative crushing and distortion in different directions on both sides of the skull, and average their outlines to compensate for it. Some additional decrushing was also done with the snouts, which were all a bit more flattened than normal.
So in the end we have a rather different set of skulls than the speculative versions in the last post. Interestingly enough, the large HMN S116 has an absolutely huge nose, even by the standards of the more famous HMN t1. While the nasal arches are not preserved in S116, the enormous and massively buttressed shape of the upper maxillary process means that the nasals begin higher up on the skull than in HMN t1. In addition, the higher slope of the maxilla's upper surface indicates the nasal arch was also more elongated from front to rear (relative to the snout) than in t1. This overall indicates a nose that was oversized in all dimensions relative to t1. The lower jaw by contrast seems a bit undersized.
This can be easily explained as the result of ontogeny, as the large S116 - probably the same animal as the huge mounted postcrania labeled HMN SII - is actually still growing, its coracoids being unfused to scapulae, though it is still more mature than the smaller t1. However, there is probably more to this bulbous difference in nasal size than just ontogeny.
Note that the immature HMN S66, which is smaller than t1, also shares the large S116's trait of very large and tall upper maxillary processes and thus nasal bones that are rooted very high on the head. The nasal of S66 is flattened, which is to be expected as it has disconnected from the premaxillary (whose upper portion, making up the lower half of the nasal arch, has long broken off and disappeared) . However judging by the high-sloping upper surfaces of the maxillae in this specimen, the full nasal arch was likely also proportionally taller and longer than in t1. The fact that both the more mature S116 and the slightly smaller and (likely) less mature S66 have significantly more massive and taller upper maxillary processes and larger noses overall than t1, as well as a different shape to the maxillary processes altogether, indicates we may actually be looking at sexual dimorphism - perhaps with the large S116 and the much smaller S66 both being males, and the intermediately sized t1 being a female.
This possibility indicates that dimorphism in Giraffatitan could have progressed, at least in the skull, from a relatively young age. HMN SII/S116 was roughly 74ft. long, even with the substitution of the smaller correct tail HMN Aa for the oversized tail "HMN Fund no" used in the mounted exhibit. Judging by the unfused coracoids (and overlapping unfused scapula from the similar-sized HMN Sa9 - which may also be part of the same individual), the animal was likely a subadult, perhaps in its tens or early 20s assuming these animals took around 30 years to reach adulthood, which seems to be the indication in osteological sauropod studies. HMN S66, by a very rough estimate, was probably around 50ft. long, and may have been in its early teens. Unfortunately there has not been much histological work done on Giraffatitan to determine the ages of various specimens so these are speculations for now, but it is likely that if we are seeing sexual dimorphism in skulls, it probably began well before Giraffatitan reached physical maturity.
Of course, adult Giraffatitans (of which HMN XV2 and "HMN Fund no" may be examples) would have had even bigger heads. As these larger specimens, likely ranging between 85 and 90ft. long when alive, are not known from shoulder material, whether they are full-grown or not is impossible to determine. So the typical adult size of Giraffatitan - let alone its upper limit - is not determinable with any certainty, and neither is its maximum likely adult skull size. But we can at least scale up S116 to get a rough model of how big XVs's skull may have been.
Eventually thus we end up with an ontogenic sequence, which can be compared to other brachiosaurs known thus far:
Yes, those are some pretty huge skulls. And it makes sense, as they needed a big head, and especially a big mouth, to pack down all the food needed to grow to such huge sizes and beyond. HMN XV2 could have taken in 30gk in a single bite (though given how Jurassic conifer tendrils were built, much of each bite would have been air). And things get even stranger when you realize that even in the smaller HMN t1, the braincase was about 500 cc's, far larger than in many dinosaurs, and comparable to a chimpanzee brain, which is considered pretty large in terms of raw size. Nobody will ever see sauropods as "pin-headed" ever again.
So to recap, not all Giraffatitan skulls were copies of HMN t1. There is significant variation, enough to suggest a possible dimorphism in addition to ontegenic changes.
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:
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.
I knew this day was coming!
Lacovara's titanosaur has been described, named, and even 3D imaged! Dreadnoughtus schrani, read about it here: http://www.nature.com/srep/2014/140904/srep06196/full/srep06196.html .
I saw this animal in preparation at the lab in Carnegie Museum long before it had a name, and I had the opportunity to speak with Dr. Lacovara himself at SVP 2010 and 2011 about this animal's morphology and likely lineage, so seeing the fruits of the Drexel team's work is personally satisfying. And unlike many instances of new dinosaur names, this one fits the bill perfectly. Dreadnoughtus is indeed a dreadnought of the dinosaurs. Not the only one by any means, but it's about time sauropods got some really imposing-sounding names, not just predatory theropods like T. rex. At some point sauropods really do get too big for any predator to mess with.
Now as usual with these giant dinosaur discoveries there are a number of myths floating around with the facts. Some of the most common rumors media reports that we can scrutinize are as follows:
1. This is the biggest dinosaur yet found.
Actually, no it's not. Argentinosaurus, Alamosaurus, Puertasaurus, Ruyangosaurus, the Chubut Monster, "Huanghetitan" ruyangensis, and maybe even Paralititan and Argyrosaurus sp. likely outclass it for raw size and mass. And there are a few brachiosaurs which also might be larger, including a very big referred specimen of Brachiosaurus itself. Of course neither specimen of Dreadnoughtus is fully grown (unfused scapula-coracoid suture is a dead giveaway of immaturity) so perhaps an adult Dreadnoughtus could rank higher in the "top 10 biggest". It is however among the biggest dinosaurs that are actually complete enough to reasonably estimate their size without much room for guesswork. But nobody is officially claiming it to be the "biggest" - we know based on general large titanosauriform proportions that most or all of the aforementioned animals are larger, even if estimating just how much larger is a bit more tricky.
2. This is the most complete giant titanosaur found.
This is technically true. Although it's missing most of the neck and ribs, which are largely present in Futalognkosaurus, the other contender for "most complete giant titanosaur". The fully tally of bones from the two Dreadnoughtus specimens adds up to more, especially considering the limb material, but the published diagrams and 3D scans still look less complete than Futalognkosaurus - when you composite all 3 specimens of Futa together, anyway. Surface area-wise, Futa's huge and deep neck bones at least make it appear more complete. And the referred juveniles contribute some limb material. Both animals appear to be similar in size.
3. This animal is a lognkosaur, as the paper seems to imply.
What's funny is that when the fossils were still under preparation back in 2010-11, both Dr. Lacovara and myself thought it might be something much more derived, like a record-sized Aeolosaurus-grade saltasaurid, due to the forward-slanted, antenna-like prezygapophyses in the tail. Of course to be fair, most of the fossils were in fragments at the time and had to be painstakingly glued back together, and when part or all of a caudal neural spine is broken off, many unrelated titanosaurs can look deceptively like "aeolosaurs". However, after analyzing the paper I can say that a lognkosaur-like position is indeed more plausible. This animal however isn't quite a lognkosaur. Close, but not quite.
The upper humerus bulges upward medially, much more like Argyrosaurus and Quetecsaurus, which has a very Argyrosaurus-like hand shape. Unfortunately hand material is missing for Dreadnoughtus, but the arm bones look Argyrosaur-like enough. The femur is very wide and robust with a large, midlevel 4th trochanter, convex-curved upper margin, and a reduced lateral bulge - very different from any known lognkosaur femur, but very similar to the two huge "Argyrosaurus sp." femurs in the Field Museum. The dorsal vertebrae are pretty wide with substantial laminae making the neural spines triangular, but just not as wide as in true lognkosaurians. They do however bear a passing resemblance to the dorsals of "Argyrosaurus sp." (=Elaltitan lilloi) specimen PVL 4628. The paper clusters it with Malawisaurus, which it places in a more derived position than true lognkosaurs - a position that isn't supported by the humerus and femur morphology and think should be re-examined. The Paleo King ranks this species as an Argyrosaurid, probably closest to Quetecsaurus. Which is a very good thing indeed, as it (along with the even odder Quetecsaurus) greatly improves our knowledge of this obscure titanosaur family.
|Bones NOT to scale here!|
|Or here, though looks may deceive!|
4. The neck was horizontal (?!?!?!?)
The reality is that only two of the neck bones were found, and both exhibit pretty serious crushing. And the first 3 dorsal vertebrae are missing entirely, with the 4th being seriously crushed as well. So it's very difficult if not impossible to reconstruct its neck posture accurately. The honest answer is that we don't know what Dreadnoughtus' neck posture was. But I think it's a pretty good guess that the neck was vertical or semi-vertical as in Futalognkosaurus, not horizontal as in the published skeletal in the paper. We are definitely dealing with a high-browser here. Titanosaurs of such large size usually have the extremely long and vertical necks of high browsers - there is no point in wasting such necks to only bend down and eat ferns like Saltasaurus or Diplodocus. Even the paltry tooth material found with Dreadnoughtus is that of a high-browsing conifer eater. The 9th(?) cervical is big enough to indicate an even longer neck than Futalognkosaurus, and even with the 3D model omitting any speculative reconstruction of the hands (and leaving precious little space for them), the shoulders of Dreadnoughtus are still higher than its hips. Add in hands of correct lognkosaur or argyrosaur proportions, and this will tilt up the torso and shoulders even further. And the general rule with all high-shouldered sauropods is that they also tend to be high-browsers, regardless of neck length. So we have two patterns of evidence in favor of a vertical neck.
|Original skeletal from paper - the neck seems to be horizontal to make room for more figures? The back is oddly curved, which isn't evidence by anything in the fossils, and the dorsal spines just look wrong. Where's the backsweep?|
|Very hastily corrected version with correct-sized hands and a straighter back and more vertical neck. Now that's better!|
5. Dreadnoughtus and Puertasaurus were basically best chums.
Doubtful. Although they were found very close together (something like only 13 miles apart) in Santa Cruz province in the far south of Argentina, their time horizons may be different. The exact stratigraphy of the Dreadnoughtus site is still a bit murky, and even if it is Maastrichtian in age, it may still be separated from Puertasaurus by hundreds of thousands of years if not more. And even if they did live at the same time, they may not have been buddies. Big sauropods in similar feeding niches were just as likely to compete over resources as share them. Notice that term similar niches. This did not mean that big herbivores always butted heads (or tails, as the case may be). Sauropods in vastly different feeding niches (such as brachiosaurs and diplodocids in the Morrison and Tendaguru formations) tended to coexist just fine.
Plus, if the subadult type specimen of Dreadnoughtus (or one of similar size, around 50-60 tons) crossed paths with the Puertasaurus type (around 90-110 tons, which may or may not be an adult) then maybe "dread-nought" may have stopped being such an appropriate label! Comparing the dorsals of Dreadnoughtus with the one found from Puertasaurus, you will soon see that while Dreadnoughtus may be huge, it's definitely not in the same league.
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.