Giraffe and human metacarpals compared
May 30, 2020
Here’s one of my most prized possessions: a cannon bone from a giraffe. I got it last fall from Necromance, a cool natural history store in LA. Originally they had a matched pair on display in the front window. Jessie Atterholt got one of them last summer, and I got the other a few months later.
The cannon bones of hoofed mammals consist of fused metacarpals (in the forelimbs) or metatarsals (in the hindlimbs). In this case, the giraffe cannon bone in the top photo is the one from the right forelimb, consisting of the fused 3rd and 4th metacarpals, which correspond to the bones in the human hand leading to the middle and ring fingers. Only my third metacarpal is traced in the top photo. For maximum homology goodness I should have traced MC4, too, but I’m lazy.
I didn’t know that this was a right forelimb cannon bone when I got it. In fact, I only figured that out this afternoon, thanks to the figures and text descriptions in Rios et al. (2016), which I got free through Palaeontologia Electronica (you can too). The weirdly large and perfectly circular holes at the ends of my cannon bone were clearly drilled out by somone, I guess maybe for mounting purposes? At first I thought it might have been to help the marrow cook out of the shaft of the bone during simmering and degreasing, but none of the drilled holes intersect the main marrow cavity, they’re just in the sponge of trabecular bone at the ends of the element.
This post is a sequel to one from last year, “Brachiosaurus and human metacarpals compared“, which featured metacarpal 3 from BYU 4744, the partial skeleton of Brachiosaurus from Potter Creek, Colorado. I know what everyone’s thinking: can we make these two high-browsing giants throw hands?
Yes, yes we can. The giraffe cannon bone is 75.5cm long, and the brachiosaur metacarpal is 57cm long, or 75.5% the length of the giraffe element. I scaled the two bones correctly in the above image. My hands aren’t the same size because they’re at different distances from the camera, illustrating the age-old dictum that scale bars are not to be trusted.
The Potter Creek brachiosaur is one of the largest in the world–here’s me with a cast of its humerus–but ‘my’ giraffe is not. World-record giraffes are about 19 feet tall (5.8m), and doing some quick-and-dirty cross-scaling using the skeleton photo above suggests that the metacarpal cannon bone in a world-record giraffe should be pushing 90cm. So the giraffe my cannon bone is from was probably between 15.5 and 16 feet tall (4.7-4.9m), which is still nothing to sniff at.
I don’t know how this bone came to be at Necromance. I assume from an estate sale or something. I only visited for the first time last year, and at that time they had three real bones from giraffes out in the showroom: the two cannon bones and a cervical vertebra. They might have put out more stuff since–it’s been about six months since I’ve been there–but all of the giraffe bones they had at that point have been snapped up by WesternU anatomists. Jessie and I got the cannon bones, and Thierra Nalley got the cervical vertebra, which is fair since she works on the evolution of necks (mostly in primates–see her Google Scholar page here). I don’t know if there are any photos of Thierra’s cervical online, but Jessie did an Instagram post on her cannon bone, which is nearly as long as her whole damn leg.
There will be more anatomy coming along soon, and probably some noodling about sauropods. Stay tuned!
Reference
Stevens & Parrish 1999 vs. Taylor et al. 2009
May 23, 2020
Credit: anonymous tattoo, Grant Harding for the caption.
Update. Here is the Instagram post that Grant got this from. Unfortunately it seems to be from an account that specialises in reposting others’ work without attribution, so we don’t know where the tattoo photo originated.
The Nanoblock Brachiosaurus
May 2, 2020
My eldest son Dan went out to visit his girlfriend Beth, shortly before the Coronavirus crisis began, during her university placement in Toulouse. While they were there, they bought me this gift:
As you can see, it’s a Lego-like self-assembly kit; but as you can also see from the mug in the background, it’s tiny. As best I can make out, the blocks are half the length and width of Lego blocks, and about third the height. The whole model is about seven or eight inches (18-20 cm) from nose to tail.
Here’s a very quick walk-round, so you can appreciate the 3d shape.
I am properly impressed with this. It has the shape of the ribcage right, and the hips and shoulders, and the proportions are right so that it conveys with absolute conviction the quality of brachiosaurosity. It has a very posable neck that can be placed in a realistic life posture, and there are even hints of scapulae and ilia.
I made only one change from the instructions: I reoriented the forefoot so that we have a vertically oriented arcade of metacarpals rather than a plantigrade forefoot.
It was a very picky build. The instructions recommend using Nanoblock tweezers, sold separately, but I just used my big clumsy fingers, so that ribs and legs and things were constantly falling off. The process was rather like what this video shows, but much slower.
If you want one of your own, you can get it from Amazon UK or from Amazon US. I recommend it for serious sauropod lovers, but would be infuriating for children, and requires patience and precision to assemble.
Oh, and kit came with plenty of spare parts, in case you lose some of them: enough that Dan was able to make a juvenile with the leftovers.
The R2R debate, part 5: what I actually think
May 1, 2020
I’ve written four posts about the R2R debate on the proposition “the venue of its publication tells us nothing useful about the quality of a paper”:
- part 1: opening statement in support
- part 2: opening statement against the motion
- part 3: my response for the motion
- part 4: the video!
A debate of this kind is partly intended to persuade and inform, but is primarily entertainment — and so it’s necessary to stick to the position you’ve been assigned. But I don’t mind admitting, once the votes have been counted, that the statement goes a bit further than I would go in real life.
It took me a while to figure out exactly what I did think about the proposition, and the process of the debate was helpful in getting me the point where I felt able to articulate it clearly. Here is where I landed shortly after the debate:
The venue of its publication can tell us something useful about a paper’s quality; but the quality of publication venues is not correlated with their prestige (or Impact Factor).
I’m fairly happy with this formulation: and in fact, on revisiting my speech in support of the original proposition, it’s apparent that I was really speaking in support of this modified version. I make no secret of the fact that I think some journals are objectively better than others; but that those with higher impact factors are often worse, not better.
What are the things that make a journal good? Here are a few:
- Coherent narrative order, with methods preceding results.
- All relevant information in one place, not split between a main document and a supplement.
- Explicit methods.
- Large, clear illustrations that can be downloaded at full resolution as prepared by the authors.
- All data available, including specimen photos, 3D models, etc.
- Open peer review: availability of the full history of submissions, reviews, editorial responses, rebuttal letters, etc.
- Well designed experiment capable of replication.
- Honesty (i.e. no fabicated or cherry-picked) data.
- Sample sizes big enough to show real statistical effect.
- Realistic assessment of the significance of the work.
And the more I look at such lists, the more I realise that that these quality indicators appear less often in “prestige” venues such as Science, Nature and Cell than they do in good, honest, working journals like PeerJ, Acta Palaeontologica Polonica or even our old friend the Journal of Vertebrate Paleontology. (Note: I am aware that the replication and statistical power criteria listed above generally don’t apply directly to vertebrate palaeontology papers.)
So where are we left?
I think — and I admit that I find this surprising — the upshot is this:
The venue of its publication can tell us something useful about a paper’s quality; but the quality of publication venues is inversely correlated with their prestige (or Impact Factor).
I honestly didn’t see that coming.
Sauropod Vertebra Picture of the Week 