April 19, 2013
Up top there is a commercially obtained
cast sculpture of a thumb claw of Megaraptor. Down below is an unpainted urethane cast of one of my favorite inanimate objects in the universe: OMNH 780, a thumb claw of Saurophaganax. I dunno how much of the Megaraptor claw is real [none, it turns out, but it's based on a true story]; certainly the cast is faithful enough to record some tool-marks in the rugose part near the base. But I know how much of OMNH 780 is legit, and that is all of it. I would have put in a photo of the actual specimen but irritatingly I forgot to take any during my recent visit, and I didn’t have the Megaraptor claw back then anyway. Hopefully I’ll get back to the OMNH this summer, and then it is ON.
The kaiju-loving fanboys of CarnivoraForum undoubtedly want to know how these two compare. Well, much to my disappointment, the Megaraptor claw is a shade longer (28.7 cm max straight-line distance) than the Saurophaganax claw (26.3 cm). But the Saurophaganax claw is about twice as thick and way more robust, and the flexor tubercle which anchored the tendon that powered the claw’s movement is friggin’ immense. It’s like pitting an NBA forward against an NFL linebacker: one is a little taller, but the other one will pound you like a tent stake.
If anyone’s wondering, these claws are both waaay shorter than those of Therizinosaurus (half a meter and up), which still holds the longest-claws-of-anything-ever title. The problem for fans of excessive violence is that Therizinosaurus probably wasn’t doing terribly exciting things with its claws–grooming its feathers, making veggie kabobs, and scratching its ample behind, most likely.
The same was not true for Saurophaganax, which the unbelievers call Allosaurus maximus, a red-blooded all American murder machine with a triple PhD in kicking your ass. When it wasn’t drinking camptosaur blood straight from the jugular, it was eating mud-mired diplodocids butt first while they were still alive. And what about those rumors that Saurophaganax was completely feathered in $100 bills, or that it was the direct linear ancestor of Charles Bronson and Steven McQueen? It’s probably too soon to say, since I just made them up, but I’ll bet your mind is blown nonetheless.
How dangerous was Saurophaganax? Let me put it this way: it’s still dangerous. Thanks to the high concentration of heavy elements in Morrison dinosaur bones, you’re supposed to air out the specimen cabinets before you start working so the radon can escape. Otherwise you might breathe in freakin’ radioactive gas and get cancer (in contrast to some “facts” in the previous paragraph, this is actually true). That’s right, Saurophaganax can kill you, just by lying around in a drawer. After 145 million years, it’s still reaping souls for Hades. By god, that’s giving them what for!
In short, the thumb claw of Saurophaganax is the most impressive instrument of dinosaurian destruction I’ve yet laid eyes on. If you want to see it in context, check out the mounted skeleton at the Oklahoma Museum of Natural History in Norman.
All I want to do in this post is make people aware that there is a difference between these two things, and occasionally that affects those of us who work in natural history.
In one of his books or essays, Stephen Jay Gould made the point that in natural history we are usually not dealing with whether phenomena are possible or not, but rather trying to determine their frequency. If we find that in a particular population of quail most of the birds eat ants but some avoid them, then we know some things: that quail can tolerate eating ants, that quail are not required to eat ants, and that both strategies can persist in a single population.
This idea has obvious repercussions for paleoart, especially when it comes to “long-tail” behaviors. I dealt with that in this post, and also in the comment thread to this one. But that’s not what I want to talk about today.
Sometimes it is useful to talk about things that never happen, or that have at least never occurred in the sample of things we know of. Obviously how certain you can be in these cases depends on the intensity of sampling and the inherent likelihood of a surprising result, which can be hard to judge. If you argued right now that T. rex lacked feathers because no T. rex specimens have been found with feathers, you’d most likely be wrong; it is almost certainly just a matter of time before someone finds direct evidence of feathers in T. rex, given the number of T. rex specimens waiting to be found and the strength of the indirect evidence (e.g., phylogenetic inference, analogy: ornithomimids are known to be feathered even though most specimens are found without feather impressions). If you argue that sauropods are unique among terrestrial animals in having necks more than five meters long, you’re most likely right; being wrong would imply the existence of some as-yet undiscovered land animal of sauropod size, or with seriously wacky proportions (or both), and our sampling of terrestrial vertebrates is good enough to make that extremely unlikely.
The reason for this post is that sometimes people confuse that last argument, which is about sampling and induction, with the argument from personal incredulity.
For example, in our no-necks-for-sex paper (Taylor et al. 2011), we included this passage:
Sauropoda also had a long evolutionary history, originating about 210 million years ago in the Carnian or Norian Age of the Late Triassic, and persisting until the end-Cretaceous extinction of all non-avian dinosaurs about 65 millions years ago. Thus the ‘necks-for-sex’ hypothesis requires that this clade continued to sexually select for exaggeration of the same organ for nearly 150 million years, a scenario without precedent in tetrapod evolutionary history.
One of the reviewers argued that we couldn’t include that section, because it was just the argument from personal incredulity writ large, like so:
There are no other known cases of X in tetrapod evolutionary history, and therefore we don’t believe that the case in question is the sole exception.
…with the second part of that unstated (by us) but implied. But we disagreed, and argued (successfully) that it was an argument based on sampling, like so:
There are no other known cases of X in tetrapod evolutionary history, and therefore it is unlikely that the case in question is the sole exception.
Now, it is perfectly fair to criticize arguments like that based on the thoroughness of the sampling and the likelihood of exceptions, as discussed above for T. rex feathers. Just don’t mistake arguments like that for arguments from personal incredulity.* On the flip side, if someone makes an argument from personal incredulity, see if the same thing can be restated as an argument about sampling. Maybe they’re correct but just expressing themselves poorly (“I refuse to believe that the moon is made out of cheese”), and maybe they’re wrong and restating things in terms of sampling will help you understand why.
* If you want to get super pedantic about it, they’re both arguments from ignorance. But one of them is at least potentially justifiable by reference to sampling. Absence of evidence is not necessarily evidence of absence, but it may get to be that way as the sampling improves (e.g., there is no evidence of planets closer to the sun than Mercury, and at this point, that is pretty persuasive evidence that no such planets exist).
Parting shot: one thing that has always stuck in my head from Simberloff (1983) is the bit about imagining a large enough universe of possible outcomes. And I’ve always had a perverse fascination with Larry Niven’s “Down in Flames”, in which he pretty much demolished his Known Space universe by assuming that every basic postulate of that universe was false. Neither of these follow directly on from the main point of the post, but they’re not completely unrelated, either. Because I think that they yield a pretty good heuristic for how to do science: imagine what it would take for you to be wrong–imagine a universe in which you are wrong–and then go see if the thing that makes you wrong, whatever it is, can be shown to exist or to work. If not, it doesn’t mean you’re right, but it means you’re maybe less wrong, which, if we get right down to it, is the best that we can hope for.
The photos have nothing to do with the post, they’re just pretty pictures from the LACM to liven things up a little.
- Simberloff, D. (1983). Competition theory, hypothesis-testing, and other community ecological buzzwords. The American Naturalist, 122(5), 626-635.
- Taylor, M. P., Hone, D. W., Wedel, M. J., & Naish, D. (2011). The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology, 285(2), 150-161.
April 8, 2013
Last night London and I spent the night in the Natural History Museum of Los Angeles County (LACM), as part of the Camp Dino overnight adventure. So we got lots of time to roam the exhibit halls when they were–very atypically–almost empty. Above are the museum’s mounted Triceratops–or one of them, anyway–and mounted cast of the Mamenchisaurus hochuanensis holotype, presented in glorious not-stygian-darkness (if you went through the old dino hall, pre-renovation, you know what I mean).
We got there early and had time to roam around the museum grounds in Exposition Park. The darned-near-life-size bronze dinos out front are a minor LA landmark.
The rose garden was already closed, but we walked by anyway, and caught this rainbow in the big fountain.
After we checked in we had a little time to roam the museum on our own. I’ve been meaning to blog about how much I love the renovated dinosaur halls. The bases are cleverly designed to prohibit people touching the skeletons without putting railings or more than minimal glass in the way, and you can walk all the way around the mounted skeletons and look down on them from the mezzanine–none of that People’s Gloriously Efficient Cattle Chute of Compulsory Dinosaur Appreciation business. Signage is discreet and informative, and so are the handful of interactive gizmos. London and I spent a few minutes using a big touch-screen with a slider that controlled continental drift from the Triassic to the present–a nice example of using technology to add value to an exhibit without taking away from the real stuff that’s on display. There are even a few places to sit and just take it all in. That’s pretty much everything I want in a dinosaur hall.
Also, check out the jumbotron on the left in the above photo. It was running a (blessedly) narration-free video on how fossils are found, collected, prepared, mounted, and studied, on about a five-minute loop. Lots of pretty pictures. Including this next one.
There are a couple of levels of perspective distortion going on here, both in the original photo and in my photo of that photo projected on the jumbotron.
Still, I feel confident positing that that is one goldurned big ilium. I’m not going to claim it’s the biggest bone I’ve ever seen–that rarely ends well–but sheesh, it’s gotta be pretty freakin’ big. And apparently a brachiosaurid, or close to it. Never mind, it’s almost certainly an upside-down Triceratops skull. Thanks to Adam Yates for the catch. I will now diminish, and go into the West.
Triceratops, Styracosaurus, and Einiosaurus–collect the whole set!
Of course, the centerpiece of the second dinosaur hall–and how great is it that there are two!?–is the T. rex trio: baby, juvenile (out of frame to the right), and subadult. Yes, subadult: the “big” one is not as big as the really big rexes, and from the second floor you can see unfused neural arches in some of the caudal vertebrae (many thanks to Ashley Fragomeni for pointing those out to me on a previous visit).
Awwwww! C’mere, little fella!
Still, this ain’t Vulgar Overstudied Theropod Picture of the Week. Here are some sweet pneumatic diplodocid caudals in the big wall o’ fossils (visible behind Mamenchisaurus in the overhead photo above). The greenish color is legit–in the Dino Lab on the second floor, they’re prepping a bunch of sauropod elements that look like they were carved out of jade.
Sudden violent topic shift, the reason for which will be become clear shortly: London and I have been sculpting weapons of mass predation in our spare time. In some of the photos you may be able to see his necklace, which has a shark tooth he sculpted himself. Here are a couple of allosaur claws I made–more on those another time.
The point is, enthusiasm for DIY fossils is running very high at Casa Wedel, so London’s favorite activity of the evening was molding and casting. Everyone got to make a press mold using a small theropod tooth, a trilobite, or a Velociraptor claw. Most of the kids I overheard opted for the tooth, but London went straight for the claw.
Ready for plaster! Everyone got to pick up their cast at breakfast this morning, with instructions to let them cure until this evening. All went well, so I’ll spare you a photo of this same shape in reverse.
We were split into three tribes of maybe 30-40 people each, and each tribe bedded down in a different hall. The T. rex and Raptor tribes got the North American wildlife halls, but our Triceratops tribe got the African wildlife hall, which as a place to sleep is about 900 times cooler. Someone had already claimed the lions when we got there, so London picked hyenas as our totem animals.
Lights out was at 10:30 PM, and the lights came back on at 7:00 this morning. Breakfast was out from 7:15 to 8:00, and then we had the museum to ourselves until the public came in at 9:30. So I got a lot of uncluttered photos of stuff I don’t usually get to photograph, like this ammonite. Everyone should have one of these.
London’s favorite dino in the museum is Carnotaurus. It’s sufficiently weird that I can respect that choice.
Not that there’s anything wrong with the old standards, especially when they’re presented as cleanly and innovatively as they are here.
Finally, the LACM has a no tripod policy, and if they see you trying to carry one in they will make you take it back to your car. At least during normal business hours. But no one searched my backpack when we went in last night, and I put that sucker to some good use. Including getting my first non-bigfoot picture of the cast Argentinosaurus dorsal. It was a little deja-vu-ey after just spending so much time with the giant Oklahoma Apatosaurus–elements of the two animals really are very comparable in size.
If you’re in the LA area and interested in spending a night at the museum–or at the tar pits!–check out the “Overnight Adventures” page on the museum’s website. Cost is $50 per person for members or $55 for non-members, and worth every penny IMHO. It’s one of those things I wish we’d done years ago.
March 20, 2013
Next week I’m going to visit the Perot Museum of Nature and Science in Dallas, Texas, to see their big Alamosaurus (these photos were kindly provided by Ron Tykoski of the Perot Museum, with permission to post). See that sweet string of cervical vertebrae in front of the mounted skeleton? A photo of those same vertebrae when they were still in the ground was featured in the post “How big was Alamosaurus?” three and a half years ago. Happily now they are out of the ground, prepped, and on display, and Tony Fiorillo and Ron Tykoski are working on getting them and some other new Alamosaurus material described.
Here’s another view of that mount. You may be wondering, first, how legit is it, and second, how big is it? Happily, I have answers for you. In email messages with permission to cite, Ron Tykoski wrote,
The Alamosaurus skeletal mount by RCI in the photos is based upon scaling the Smithsonian and UT Austin material to match the size of our cervicals here in Dallas. There were enough overlapping parts between the pieces at the three institutions to get the proportions pretty nicely supported.
I ran across your SV-POW thread on ‘How big was Alamosaurus?’ back when you first posted it in ‘09. You ought to be pleased to know that you came remarkably close to the eventual size of the skeleton we wound up with. The full skeleton RCI generated (again, based off scaling to the Dallas verts) is 84ft long, about 16ft at the shoulder (I dropped a tape measure from the 1st dorsal neural spine to the floor during skeleton construction and got 480cm-490cm), and a neck + head of about 25ft. The overall length and neck length were provided by RCI after fabrication and assembly. That shoulder height is a bit suspect though based on the positioning of the pectoral girdle in the mount, relative to the ribcage and vert column. I think the head currently is posed about 25ft or so off the floor, but I can’t verify that (I didn’t get into the scissor-lift to check that at the time). This skeleton actually played a role in determining the size of the hall in which it is installed. We decided early in the planning phase for the building that this skeleton would be the centerpiece for the hall. As a result, the ceilings for this floor had to be made extra-high, and the mid-room support pillars designed out to accommodate the skeleton and still clear all the HVAC, sprinkler heads, and other necessities.
That’s all pretty fantastic–both that we have enough of Alamosaurus to do a pretty rigorous full skeletal mount, and that the beast was legitimately pretty darned big. Ron goes on:
One correction to the story on SV-POW, the Dallas cervical series consists of only 9 verts, not 10. There may have been frags or something that made folks think there was a 10th at the anterior end of the series when first found, but I’ve never seen evidence of it in our collection. This may be supported by the fact that the verts were given letter designations in the field (that we still use), and are identified as verts B through J, from anterior to posterior.
I later learned from Tony Fiorillo that the vertebrae were labelled B through J in the field in case anything anterior to B turned up, but nothing did, so the ‘A’ placeholder went unused. That reminds me of the search in the mid-1800s for the hypothetical planet Vulcan (not the one you’re thinking of) between Mercury and the Sun, which I bring up for no reasons other than that hypothetical planets are cool, and if you’re exploring, it’s worth keeping an open mind about what might yet turn up.
There’s more to say about the size of Alamosaurus–we haven’t even covered the big material described by Fowler and Sullivan (2011) yet–but I’m not going to say a whole lot right now, since I’m going to see the Big Bend material in Dallas in just a few days. Watch this space.
January 31, 2013
You may remember this:
…which I used to make this:
…and then this:
The middle image is just the skeleton from the top photo cut out from the background and dropped to black using ‘Levels’ in GIMP, with the chevrons scooted up to close the gap imposed by the mounting bar.
The bottom image is the same thing tweaked a bit to repose the skeleton and get rid of some perspective distortion on the limbs. The limb posture is an attempt to reproduce an elephant step cycle from Muybridge.
That neck is wacky. Maybe not as wrong as Omeisaurus, but pretty darned wrong. As I mentioned in the previous Rapetosaurus skeleton post, the cervicals are taller than the dorsals, which is opposite the condition in every other sauropod I’ve seen. All in all, I find the reposed Rapetosaurus disturbingly horse-like. And oddly slender through the torso, dorsoventrally at least. The dorsal ribs look short in these lateral views because they’re mounted at a very odd, laterally-projecting angle that I think is probably not correct. But the ventral body profile still had to meet the distal ends of the pubes and ischia, which really can’t go anywhere without disarticulating the ilia from the sacrum (and cranking the pubes down would only force the distal ends of the ilia up, even closer to the tail–the animal still had to run its digestive and urogenital pipes through there!). So the torso was deeper than these ribs suggest, but it was still not super-deep. Contrast this with Opisthocoelicaudia, where the pubes stick down past the knees–now that was a tubby sauropod. Then again, Alamosaurus has been reconstructed with a similarly compact torso compared to its limbs–see the sketched-in ventral body profile in the skeletal recon from Lehman and Coulson (2002: figure 11).
I intend to post more photos of the mount, including some close-ups and some from different angles, and talk more about how the animal was shaped in life. And hopefully soon, because history has shown that if I don’t strike while the iron is hot, it might be a while before I get back to it. For example, I originally intended this post to follow the last Rapetosaurus skeleton post by about a week. So much for that!
Like everything else we post, these images are CC BY, so feel free to take them and use them. If you use them for the basis of anything cool, like a muscle reconstruction or life restoration, let us know and we’ll probably blog it.
September 25, 2012
Another extraordinary specimen from the wonderful Oxford University Museum of Natural History: the skeleton of a goliath frog Conraua goliath, the largest extant anuran, which comfortably exceeds 30 cm and 3 kg in life:
As noted by sometime SV-POW!sketeer Darren Naish over on Tetrapod Zoology, frogs have stupidly weird skeletons — surely the most derived of any tetrapod, despite their lowly, early diverging “amphibian” status. Rather than describe all the oddities myself, I’ll just quote Darren’s article:
Anurans have (at most) nine presacral vertebrae, and some have as few as five; ribs are either highly reduced or absent; the radius and ulna are fused (forming the radioulna); the bones of the pectoral girdle are highly reduced and complimented by an assortment of new weird bits; the pelvis consists of a rod-like central unit (the urostyle) surrounded by two super-long, shaft-like ilia; and in their (generally) elongate hindlimbs, the tibia and fibula are fused (forming the tibiofibula) while the ankle bones are elongated to form a long ‘extra’ limb segment.
That’s a pretty astonishing list; and, sure enough, frog skeletons weird me out every time I see them. (Of all the dead animals I’d like to get hold of in decent condition, to extract the bones from, frogs miss the top of the list only to bats, crocs and turtles. And maybe raptors.)
This particular species of frog has another skeletal oddity that caught my eye:
As you can see, the humerus is perforated: there is a distinct foramen running down it just behind the anterior edge. Is the anterior bar a partially detached deltopectoral crest? Or is it a completely novel ossification that has become partially fused to the humerus?
For what it’s worth, this feature doesn’t seem to be consistently present in goliath frogs. A bit of googling shows that it’s present in this skeleton, but not in this one from Bone Clones. The humerus of the latter does have a distinctly protruding deltopectoral crest, but it lacks the perforation. So I guess that is evidence against the Novel Ossification hypothesis.
Does anyone know more about this odd feature? Does it develop through ontogeny? Is it found in other frogs? What is its mechanical significance?
September 20, 2012
Back when we were at Cambridge for the 2010 SVPCA, we saw taxidermied and skeletonised hoatzins, and were struck that the cervical skeleton was so very much longer than the neck as it appears in life — because necks lie. At Oxford last week for the 2012 SVPCA, we saw a similar pair of hoatzin mounts (one adult, one juvenile) that clarified the situation:
And here is juvenile in side-view:
As you can see, it’s folding its neck way down out of the way, so that externally it appears much shorter. (And comparing with the Cambridge specimen, you can see that the neck skeleton is proportionally much longer than this in adult.)
Why does it do this? I have no idea.
But I do know it’s not unique to hoatzins. Another nice illustration of how misleading birds’ necks are when viewed in a live animal is this parrot (probably Amazona ochrocephala) in the Natuurhistorisch Museum of Rotterdam (from this Love in the Time of Chasmosaurs post):
One thing that’s not clear to me is how much of the neck the bird can extend in life. If the parrot wants to uncoil all that spare cervical skeleton to reach upwards or forwards, can it? Will the soft tissue envelope allow it? My guess is not, otherwise you’d surely see them doing it. But then … why is all that neck in there at all?
September 8, 2012
August 15, 2012
You haven’t heard from me much lately because I’ve been busy teaching anatomy. Still, I get to help people dissect for a living, so I can’t complain.
Further bulletins as events warrant.
July 18, 2012
This is the sacrum of Camarasaurus supremus AMNH 5761. Top row: dorsal view, with anterior to left. Middle row, from left to right: anterior, left lateral and posterior views. Bottom row: ventral view, with anterior to left. Modified from Ostrom and Mook (1921:figs. 43-44).
It’s instructive to compare with the “Apatosaurus” minimus sacrum. Direct comparison is somewhat hindered for two reasons: first, the ilia are fused to that sacrum but not to this; and second, different views are available, so I put the composites together differently. We can’t do anything about the ilia. But to facilitate comparison, here is a reworked version of the “Apatosaurus” minimus illustration with the right-lateral view discarded, a ventral-view silhouette added, and the composition mirroring that of Osborn and Mook’s Camarasaurus:
One thing is for sure: whatever else “Apatosaurus“ minimus might be, it ain’t Camarasaurus.