What an articulated giraffe neck looks like
April 16, 2013
The cervical series of Giraffa camelopardalis angolensis FMNH 34426, articulated by Mike and me and photographed by Mike back in the summer of 2005, cropped and composited by me recently, not previously posted because there’s just too much cool stuff, man. But we’re working on it.
By the way, if you want the details on this critter:
UPDATE April 23, 2014: What a maroon–I completely forgot to report the size of this thing! When we articulated all the centra and measured them (without cartilage, obviously), we got a length of 171 cm. When we measured the centra individually, leaving off the anterior condyles, we got a length of 164 cm. I think the discrepancy can be explained by the relative shallowness of the posterior cotyles of the vertebrae–as you can see in the big image above, the condyles do not nest completely within the cotyles, so each one does contribute a little bit to the length of the neck.
The measurements of each vertebra, as recorded by Mike in my notebook in the FMNH mammalogy collections in 2005, are here:
Giraffa FMNH 34426 cervical and dorsal measurements
Just for completeness, I should note that in our neck cartilage paper (Taylor and Wedel 2013b), we found that cartilage added considerably to the length of the articulated neck in many amniotes. Based on the intervertebral spacing in horses, 1-2 cm of cartilage between these giraffe vertebrae doesn’t seem unreasonable, which would bring the length of the neck to perhaps 1.8 meters. Amazingly, this is only 75% of the longest giraffe necks on record, which are up to 2.4 meters (Toon and Toon 2003).
References
- Taylor, Michael P., and Mathew J. Wedel. 2013c. The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs. PLOS ONE 8(10): e78214. 17 pages. doi:10.1371/journal.pone.0078214
- Toon, A., and Toon, S.B. 2003. Okapis and giraffes. In: M. Hutchins, D. Kleiman, V. Geist, and M. McDade (eds.), Grzimek’s Animal Life Encyclopedia, 2nd ed. Vol 15: Mammals IV, 399–409. Gale Group, Farmington Hills.
Sauropod Vertebra Picture of the Week 
April 16, 2013 at 1:16 am
Given that sauropods seem play around a bit with which verts are considered to be cervicals and which are dorsals, what are your thoughts on the giraffe’s first dorsal (thoracic) vert behaving more like the last cervical; ie C8?
April 16, 2013 at 7:12 am
My distinctly non-expert take on this is that the eighth-cervical notion was proposed just once by one person (Solounias 1999), and has been ignored or refuted subsequently by everyone except People On The Internet Who Think It Sounds Cool (e.g. Mitchell and Skinner 2003, Badlangana et al. 2009). So as a sauropod guy who has to rub up against giraffes in passing, I just accept the near-unanimous view that the giraffe a respectable seven-cervical mammal.
References
Badlangana, N. Ludo, Justin W. Adams and Paul R. Manger. 2009. The giraffe (Giraffa camelopardalis) cervical vertebral column: a heuristic example in understanding evolutionary processes? Zoological Journal of the Linnean Society 155:736-757.
Mitchell, G., and J. D. Skinner. 2003. On the origin, evolution and phylogeny of giraffes Giraffa camelopardalis. Transactions of the Royal Society of South Africa 58:51-73.
Solounias, N. 1999. The remarkable anatomy of the giraffe’s neck. Journal of Zoology 247:257-268.
April 16, 2013 at 3:45 pm
I’m glad Mike got to this one first. I remember seeing the talk proposing 8 cervicals in giraffes, and reading the paper, but I’ve pretty much forgotten the whole gist of the argument and it’s clearly had no subsequent effect on me. So I’m neither for nor against it; I’m aware of it and that’s about it.
I’d probably be more het up about a possible cervical count other than 7 in giraffes if manatees and sloths didn’t have even stranger cervical counts (and different counts in different sloths). As it is, giraffes would be the fourth mammal with a non-standard cervical count, or maybe even farther down the list, which would be interesting but not mind-blowing.
April 17, 2013 at 3:58 am
Thanks guys. I thought that it was prob an unorthodox view but I don’t have access to paywalled literature and figured that you would prob have perused some relevant papers when writing yours.
Sloths are weird. Two-toeds have one less cervical than the mammal norm and three-toeds two more. Intuitively you (I) would think that the differences would be in the same direction although I know that they’re not particularly closely related.
Any idea whether the two extra cervicals in three-toeds are dorsals that have shifted or new verts that have been added (or should I be asking this over at TetZoo)?
April 17, 2013 at 4:15 am
But G. would be the only mammal with an extra cervical, no? And only by cheating. Reptilia seems able to run off extra cervicals as needed without stealing dorsals.
What does it mean that Reptilia seems to have little difficulty churning out extra vertebrae, while mammals have lost the knack? Has interaction between the spinal cord and individual verts got too specific to accommodate an extra vert tucked in there somewhere? Or muscle attachments, or arteries?
April 17, 2013 at 4:41 am
Actually, I was able to fairly readily locate a study which answers my Q.
Firstly, it would seem that three-toed sloths may have as few as 8 and as many as 10 neck vertebrae. Secondly, whether these neck vertebrae are all “cervicals” is a matter of definition.
The above-linked paper looked at the timing of ossification during development and this appeared to show that the latter “extra” neck verts are in fact ribless thoracic vertebrae. So, that appears to answer my Q about whether the extra neck verts are the result of an axial shift or not.
Now it’s just a matter of whether we should call them “cervicals” because they’re morphologically and functionally similar to the other neck vertebrae or “thoracics/dorsals” because that is what they originally were and how they seem to behave developmentally.
References
Lionel Hautiera, Vera Weisbeckerb, Marcelo R. Sánchez-Villagrac, Anjali Goswamid, and Robert J. Asher. 2010. Skeletal development in sloths and the evolution of
mammalian vertebral patterning. The Proceedings of the National Academy of Sciences vol. 107 no. 44 18903-18908
April 17, 2013 at 6:22 am
Nathan asked,
Actually the answer seems to be cancer. In humans, anyway, people with nonstandard cervical counts often die young from really nasty cancers. The hypothesis is that somehow in mammals the genes that control cervical count got pleiotropically tangled up with genes that control mitosis, so that mutations that affect the number of cervicals tend to unleash hell. See:
Galis F. 1999. Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes, and cancer. Journal of Experimental Zoology (Mol Dev Evol) 285:19
Galis F, Metz JAJ. 2003. Anti-cancer selection as a source of developmental and evolutionary constraints. BioEssays 25:1035
If you can’t get hold of those, let me know. I, uh, know a guy.
April 17, 2013 at 6:24 am
Oh, also, Mark: thanks for bringing this up. I’m sorry if I sounded dismissive. I’m really not. If anything, I’m kinda ashamed that I haven’t stayed more current on this stuff. Seeing as how I’m sorta interested in necks and evolution and the like.
April 18, 2013 at 4:17 am
No worries, Matt. I knew that, being stinkin’ mammals and all, the Q was kinda on the periphery of your area of academic interest but “necks doing crazy things” was prob inside the boundary rather than outside. And anyway, sometimes other people will jump in with an illuminating comment or two.
One additional thing that I took away from the above-mentioned study is that Hautiera et al. think that *all* mammals may have exactly seven cervicals after all, with the varying number of “neck” vertebrae in manatees and two-toed sloths also resulting from axial shifts. They stated that they intend to investigate this futher, presumably if they can get hold of a range of suitable specimens.
April 18, 2013 at 7:37 am
[…] light of the recent discussion here on how many cervical vertebrae giraffes have (spoiler: seven), I thought it would be good to air […]
April 18, 2013 at 8:15 pm
Okay, I am struggling with something here.
Hautiera et al. think that *all* mammals may have exactly seven cervicals after all, with the varying number of “neck” vertebrae in manatees and two-toed sloths also resulting from axial shifts.
I suppose it depends on how you define cervical vertebrae and dorsal vertebrae, and what kinds of evidence you can get your hands on.
As a paleontologist, for now and for the foreseeable future all I have to go on is gross anatomy, and usually without a lot of information on the sequence of skeletal fusions through development. So to me a vertebra close behind the skull (i.e., not in the sacrum or tail) with fused or otherwise immobile costal elements is a cervical vertebra, and ones farther back with big mobile costal elements are dorsals. If a vertebra has undergone an “axial shift” and lost its big mobile rib, then to me that’s a dorsal getting recruited into the cervical series, and now it’s a cervical.
Now, a developmental biologist might argue, “No, it’s still a dorsal, because X, Y, and Z”, but then I would respond that calling it a dorsal seems to be (1) defining additional cervicals out of existence, (b) based on data that paleontologists and even most gross-level comparative anatomists can’t access. I’m actually more het up about the first point: morphologically and functionally, Bradypus has 8-10 cervicals; even if those extra vertebrae are in some sense dorsals (phylogenetically, developmentally, etc.), they look like cervicals and they act like cervicals in the living animal, so as a practical matter I would prefer to call them cervicals.
Also, it seems that when these axial shifts occur we could say that vertebrae have been brought into the neck and lost their big mobile ribs but they are still developmentally dorsals, or we could say that they are morphologically and functionally cervicals even if they get off to a different start developmentally. Does the first phrasing gain us anything that the second does not? I guess more to the point: should developmental concerns automatically outweigh gross morphology and function in determining what we call these vertebrae?
I’m honestly curious. Help me out.
April 18, 2013 at 10:21 pm
Matt, I should think your definition for a cervical would suggest that many squamates would have very, VERY few cervicals indeed, and that many vertebrae preceding the shoulders might be “dorsals” due to the presence of mobile ribs.
When it comes to the axial shift, associated development of certain muscle groups, ligaments, and the natal position of the shoulder and relationship of internal organs *may* have better utility for assessing whether a vertebra is a “dorsal” or not.
What may be most obvious, though, is that a “cervical” can be a very subjective thing, indeed; settling on one definition is frought with problems, as almost anyone can bring up a contradiction. This is especially true when you consider even nonavian dinosaurs, in which the transition from “immobile” to “mobile” ribs occurs over a series of between 3 and 8 or so vertebrae, and that this is associated with the position of the shoulder girdle, this obscuring the exact position of the cervical-dorsal transition: the so-called “transitional” vertebrae of Welles and Long. Sauropods, like mammals, seem to have “settled” with a distinct cutoff, but it’s not always apparent, and we may be underestimating developmental shifts in morphology. Silounias, in his “giraffes modified their necks” paper, argues for an axial shift, by noting that one of the “last cervical” in a juvenile giraffe has the morphology of a dorsal (with large, well-separated, and mobile rib joints), but develops into something that looks like the “true” cervical immediately preceding it, which itself lacks this developmental shift.
April 18, 2013 at 10:36 pm
Matt, I should think your definition for a cervical would suggest that many squamates would have very, VERY few cervicals indeed, and that many vertebrae preceding the shoulders might be “dorsals” due to the presence of mobile ribs.
When it comes to the axial shift, associated development of certain muscle groups, ligaments, and the natal position of the shoulder and relationship of internal organs *may* have better utility for assessing whether a vertebra is a “dorsal” or not.
Yep, totally solid points. I should have said something like, “with mobile ribs that bound the peritoneal cavity” or something like that.
Having typed that, I now expect to hear about some weird tetrapod with dorsal vertebrae that don’t bound the peritoneal cavity. I can’t work out how that would be possible, but I’m still wrestling with ribless dorsals in the necks of sloths, so have mercy.
April 19, 2013 at 2:05 am
…they look like cervicals and they act like cervicals in the living animal, so as a practical matter I would prefer to call them cervicals.
In case it wasn’t clear, I agree with that altho’ I can see where Hautiera et al. are coming from. Given the paucity of fossil material it doesn’t make sense to me to be have to try to determine whether an isolated vertebrae that looks like a cervical should be referred to as a cervical, or a dorsal because it was recruited from there at some time in the past (except possibly for extinct sloths and manatees).
However, I was wondering whether the different timings for the ossification of cervicals versus dorsals might inform things like the timings for the fusion or bifurcation of different vertebrae later in life, or whether that’s so variable even within a species that the embryonic order of ossification gets lost in the noise.
April 24, 2014 at 3:08 pm
[…] meter bars are both one meter as advertised. The giraffe neck is FMNH 34426 (from this post), which is actually 1.7 meters long, but I scaled it up to 2.4 meters to match that of the tallest […]