Sauropod Vertebra Picture of the Week | SV-POW! All sauropod vertebrae, except when were talking
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keywords: description:SV-POW! ... All sauropod vertebrae, except when we're talking about Open Access Sauropod Vertebra Picture of the WeekSV-POW! All sauropod vertebrae, except when were talking about Open Access
Matt Wedel will be yapping about Brachiosaurus. Again. October 7, 2021I have the honor of giving the National Fossil Day Virtual Lecture for The Museums of Western Colorado Dinosaur Journey, next Wednesday, October 13, from 7:00 to 8:00 PM, Mountain Daylight Time. The title of my talk is Lost Giants of the Jurassic but its mostly going to be about Brachiosaurus. And since I have a whole hour to fill, Im gonna kitchen-sink this sucker and put in all the good stuff, even more than last time. The talk is virtual (via Zoom) and free, and you can register at this link.
The photo up top is from this July. Thats John Foster (standing) and me (crouching) with the complete right humerus of Brachiosaurus that we got out of the ground in 2019; that story is here. The humerus is in the prep lab at the Utah Field House of Natural History State Park Museum in Vernal, and if you go there, you can peer through the tall glass windows between the museums central atrium and the prep lab and see it for yourself.
If youve forgotten what a humerus like that looks like in context, heres the mounted Brachiosaurus skeleton at the North American Museum of Ancient Life with my research student, Kaelen Kay, for scale. Kaelen is 58 (173cm) and as you can see, she can just get her hand on the animals elbow. The humerusin this case, a cast of the right humerus from the Brachiosaurus altithorax holotypeis the next bone up the line. Kaelen came out with us this summer and helped dig up some more of our brachiosaurmore on that story in the near future.
Want more Brachiosaurus? Tune in next week. Heres that registration link again. I hope to see you there!
Posted by Matt WedelFiled in brachiosaurids, Brachiosaurus, humerus, museums, navel blogging, People we like, stinkin appendicular elements, stinkin' mammals, stinkin' SV-POW!sketeers, timely, Utah Field House of Natural History
Leave a Comment Heres that hen respiratory system segmentation youordered September 13, 2021
Two and a half years ago, I posted a glorious hemisected hen, taken (with permission) from a poster by Roberts et al. 2016, and supplied by Ray Wilhite, best known in this parish for his work on sauropod appendicular material.
At the end of that post, I blithely promised More from this poster in a subsequent post!, and then — predictably — forgot all about it. My apologies. Here is the fulfilment of that promise, in glorious colour:
Theres lots to love here, not least the sheer extent of the respiratory system — it almost seems there is no space in the hens torso for any actual soft tissue. But the big thing for me is how tiny a part of the respiratory system the lung contributes. Its almost an afterthought: its a fools game judging 3d volumes from a single perspective, but here it seems that the lung makes up at most 20% of the system.
And yet its the only part of the system that has parenchymal tissue — the only place where gas exchange takes place. The air-sacs are not doing anything: they just sit there, moving air through the lung as they expand and contract but otherwise inert. Isnt that strange? Doesnt it seem wasteful? Why not respire though the entire air-sac system?
And of course this raises questions about how the system worked in sauropods. Long-time followers of this blog, or indeed of Matts research output, will know that there is very good evidence that sauropods had an air-sac system similar to that of birds, but since the air-sacs themselves do not fossilise we cant know the details of the soft-tissue anatomy — only what we can infer from fossilised vertebrae. So I cant help speculating about whether the greater metabolic demands of sauropods compelled them to evolve more extensive gas-exchange in their respiratory systems.
[Greater metabolic demands? Yes, because metabolic throughput scales roughly with body mass to the 3/4 power (Kleiber 1932) but air gets into an animal though a gas-exchange surface whose area, if isometric, goes with the square of linear dimension, i.e. body mass to the 2/3 power. So metabolic demand relative to gas-exchange area goes with body mass to the power 3/4 / 2/3 = 3*3/4*2 = 9/8. All numbers very subject to debate.]
Long, long ago (2004), in an email, I asked Matt this same question. His response, in part:
Blue whales, of up to 209 tons, get by just fine with the horribly inefficient mammalian design, so why couldnt 100 ton sauropods get by with the avian one?
Which is a good point. But as I responded at the time:
Maybe the real mystery here is what the heck are whales doing that were not? And the answer would seem to be swimming in water, which is an order of magnitude less energetically demanding than walking on land. Hmm.
(And yes, it really does seem to be true that swimming is about an order of magnitude less energetic than running: see Schmidt-Nielsen 1972:figure 4.)
And there, my record of our discussion fizzles out. If we discussed further, history does not record what was said. And I feel this is still worthy of some exploration. In short, whales are big blubbery cheats, and nothing they say or do can be taken at face value.
Bonus content! Here is the whole poster!
Filed in dissection, pneumaticity
4 Comments No-one better tell ME giraffes arent all about the highbrowsing August 14, 2021
On Thursday, I took the family to the Cotswolds Wildlife Park, a rather lovely zoo just over an hour away from us in Burford, Oxfordshire. Somehow Id never even heard of this place until we passed a sign for it on the A417 a few weeks ago. Lots of great stuff there, but I wanted to focus on this:
As you can see, the clump of big trees in the giraffe enclosure has had all its foliage methodically stripped off, right up to the point where the tallest giraffe can reach, giving it a striking mushroom shape.
Posted by Mike TaylorFiled in giraffe
2 Comments Whats the difference between a cervical and dorsalvertebra? June 6, 2021
In mammals — certainly the most-studied vertebrates — regional differentiation of the vertebral column is distinct and easy to spot. But things arent so simple with sauropods. We all know that the neck of any tetrapod is made up of cervical vertebrae, and that the trunk is made up of dorsal vertebrae (subdivided into thoracic and lumbar vertebrae in the case of mammals). But how do we tell whether a given verebra is a posterior cervical or an anterior dorsal?
Here two vertabrae: a dorsal vertebra (D3) and a cervical vertebra (C13) from CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):
Its easy to tell these apart, even when as here we have only lateral-view images: the dorsal vertebra is tall, its centrum is short, its neural spine is anteroposteriorly compressed and its parapophysis is up on the dorsal half of the centrum; but the cervical vertebra is relatively low, its centrum is elongated, its neural spine is roughly triangular and its parapophysis hangs down well below the centrum (and has a cervical rib fused to it and the diapophysis).
But things get trickier in the shoulder region because, in sauropods at least, the transition through the last few cervicals to the first few dorsals is gradual — the vertebrae become shorter, taller and broader — and tends to have no very obvious break point. In this respect, they differ from mammals, in which the regional differentiation of the spinal column is more abrupt. (Although even here, things may not be as simple as generally assumed: for example, Gunji and Endo (2016) argued that the 1st thoracic vertebra of the giraffe behaves functionally like an 8th cervical.)
So here are those two vertebrae in context: the sequence D3 D2 D1 C15 C14 C13 in CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):
Given that the leftmost is obviously a dorsal and the rightmost obviously a cervical, where would you place the break-point?
The most usual definition seems to be that the first dorsal vertebra is the first one that has a free rib, i.e. one not fused to the vertebra: in the illustration above, you can see that the three cervicals on the right all have their cervical ribs fused to their diapophyses and parapophyses, and the three dorsals on the left do not. This definition of the cervical/dorsal distinction seems to be widely assumed, but it is rarely explicitly asserted. (Does anyone know of a paper that lays it out for sauropods, or for dinosaurs more generally?)
But wait!
Hatcher (1903:8) — the same dude — in his Haplocanthosaurus monograph, writes:
The First Dorsal (Plate I., Fig. 1). [] That the vertebra now under consideration was a dorsal is conclusively shown not by the presence of tubercular and capitular rib facets showing that it supported on either side a free rib, for there are in our collections of sauropods, skeletons of other dinosaurs fully adult but, with the posterior cervical, bearing free cervical ribs articulating by both tubercular and capitular facets as do the ribs of the dorsal region. The character in this vertebra distinguishing it as a dorsal is the broadly expanded external border of the anterior branch of the horizontal lamina [i.e. what we would now call the centroprezygapophyseal lamina]. This element has been this modified in this and the succeeding dorsal, no doubt, as is known to be the case in Diplodocus to give greater surface for the attachment of the powerful muscles necessary for the support of the scapula.
Hatchers illustrations show this feature, though they dont make it particularly obvious: here are the last two cervicals and the first dorsal, modified from Hatcher (1903:plate I), with the facet in question highlighted in pink: right lateral view at the top, then anterior, and finally posterior view at the bottom. (The facet is only visible in lateral and anterior views):
Taken at face value, Hatchers words here seem to imply that he considers the torso to begin where the scapula first lies alongside the vertebral column. Yet if you go back to the Diplodocus transition earlier in this post, a similar scapular facet is not apparent in the vertebra that he designated D1, and seems to be present only in D2.
Is this scapular-orientation based definition a widespread usage? Can anyone point me to other papers that use it?
Wilson (2002:226) mentions a genetic definition of the cervical/dorsal distinction
Vertebral segment identity may be controlled by a single Hox gene. The cervicodorsal transition in many tetrapods, for instance, appears to be defined by the expression boundary of the Hoxc-6 gene.
But this of course is no use in the case of extinct animals such as sauropods.
So whats going on here? In 1964, United States Supreme Court Justice Potter Stewart, in describing his threshold test for obscenity, famously said I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it. Is that all we have for the definition of what makes a vertebra cervicals as opposed to dorsal? We know it when we see it?
Help me out, folks! What should the test for cervical-vs-dorsal be?
ReferencesGunji, Mego, and Hideki Endo. 2016. Functional cervicothoracic boundary modified by anatomical shifts in the neck of giraffes. Royal Society Open Science 3:150604. doi:10.1098/rsos.150604Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.Hatcher, J. B. 1903b. Osteology of Haplocanthosaurus with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds; additional remarks on Diplodocus. Memoirs of the Carnegie Museum 2:1-75 and plates I-VI.Wilson, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136:217-276. Posted by Mike TaylorFiled in cervical, Diplodocus, dorsal, Haplocanthosaurus, help SV-POW!, ribs, Thinking it through
16 Comments How big was theArchbishop? June 2, 2021
Various Internet rumours have suggested that the Archbishop is a super-giant sauropod one third larger than the mounted Giraffatitan specimen MB.R.2181 (formerly HMN SII). This is incorrect.
Migeods assessment of the size of the animal was based on the vertebrae: The [neck] vertebrae found give a 20-foot [6.10 m] length [] The length of the back including the sacral region was about 15 feet [4.57 m]. The eight or nine caudal vertebrae cover about 6 feet [1.83 m] (Migeod 1931a:90). This gives the total preserved length of the skeleton as 41 feet (12.50 m). By comparison, Janensch (1950b:102) gives lengths of portions of the mounted skeleton of MB.R.2181 as 8.78m (neck), 3.92m (torso) and 1.07m (sacrum) for a torso-plus-sacrum length of 4.99m. On this basis, the preserved neck of NHMUK PV R5937 is only 69% as long as that of MB.R.2181, but since the first four vertebrae were missing and omitted from Migeods measurement, this factor cannot be taken at face value. More informative is the torso-plus-sacrum length, which in NHMUK PV R5937 is 92% the length of MB.R.2181.
This is consonant with measurements of individual elements, which compare as follows:
Table 4. Comparative measurements of Archbishop and Giraffatitan elements
Archbishop measurements taken from Migeod (1931a) and converted from imperial; Giraffatitan measurements are for MB.R.2181 except where noted, and are taken from Janensch (1950a:44) and Janensch (1961).
Notes.
[1] Janensch (1950a) did not report a total centrum length for C11, as its condyle had not been removed from the cotyle of C10; but since the length of its centrum omitting the condyle was, at 87 cm, identical to that of C10, it is reasonable to estimate its total length as also equal to that of C10.
[2] Janensch (1961:181) did not include measurements for the right scapula of MB.R.2181, which is incorporated into the mounted skeleton, but does give the proximodistal length of its right coracoid as 45 cm. Using the 193 cm length given for the similarly sized scapula Sa 9, we can deduce a reasonable total estimate of 238 cm for the scapulocoracoid.
[3] Estimated by Janensch (1950b:99) based on cross-scaling from the fibula and ilium of Find J from the Upper Saurian Marl.
[4] This is the measurement provided by Janensch (1961:199) for the ilium Ma 2, which is incorporated into the mounted skeleton, and which Janensch (1950b:99) considered to match MB.R.2181 very precisely.
[5] Based on a restoration of the midshaft which Janench (1950b:99) calcuated based on other finds.
Individual lines of this table should each be treated with caution: Migeods measurements may have been unreliable, and in any case are underspecified: for example, we do not know whether, when he gave a vertebras length, he included overhanging prezygapophyses or the condyle. Similarly, we know that Migeod (1931:96) wrote that a rib was as much as 92.5 inches long, but we do not know for certain that, like Janensch, he measured the length over the curve rather than the straight-line distance between the ends. And when Migeod says that the ilium measured 38.5 by 31 inches we do not know that the height was measured at the public process, as Janensch (1961:199) specified.
With those caveats in place, nevertheless, a picture emerges of a sauropod somewhat smaller than MB.R.2181, though by no means negligible. On average, the measurements come out about 15% smaller than those of Giraffatitan.
But this average conceals a great deal of variation. The cervical vertebrae are comparable in length to those of MB.R.2181 (The total of 203 cm for C10 and C11 in the Archbishop, only 1.5% longer than 200 cm for MB.R.2181, is a difference well within the margin of measurement error). The Archbishops scapulocoracoid may have been 93% as long as in MB.R.2181. But the limb bones are signficantly shorter (87% for the humerus and a scarcely credible 62% for the femur), and the humeri at least bseem to be have been proportionally more robust in the Archbishop: only 2.86 times as long as wide, whereas the ratio is 3.61 in MB.R.2181. If Migeods measurements can be trusted, we have here an animal whose neck is as long as that of Giraffatitan, but whose limbs are noticably shorter. These proportions corroborate the hypothesis that the Archbishop is not a specimen of Giraffatitan.
Posted by Mike TaylorFiled in Giraffatitan, math, The Archbishop
11 Comments A third pneumatic hiatus in a specimen of Barosaurus May 27, 2021
Heres a pretty cool image: Plate 7 from Lull (1919), showing the partial skeleton of Barosaurus YPM 429 (above), compared to the much more complete skeleton of Diplodocus CM84/94 (below).
Ive been pretty familiar with that Barosaurus skeleton diagram since I was about 9 years old, because its in Donald Gluts New Dinosaur Dictionary, which Ive written about here before. In particular, I like that Lull was scrupulous about drawing in the lateral pneumatic cavities in the caudal vertebrae. Its pretty common in Diplodocus for the tail to be pneumatized out to somewhere between caudal 15 and 19, and the same is true in Barosaurus. Im not just relying on the figureLull was also good about saying explicitly what was going on with the pneumatization in the centrum of each vertebra.
I returned to this image as an adult doing research on sauropod pneumaticity, and I read big swaths of Lull (1919), but never the bit about the sacrum. Why would I? The sacrum of YPM 429 is pretty scrappy, and I was mostly interested in the big honkin cervicals, and in learning how to distinguish bones of Barosaurus and Diplodocus. I always assumed that the sacrum of Barosaurus was pneumatized right the way through.
Only, er, it aint. As I just discovered.
Lull (1919: p. 22):
See that second sentence? The central fragment is extremely massive, with no adaptation for lightening the weight appreciable in the portion preserved. Thats old-timey talk for, the chunk of centrum has no pneumatic openings or cavities. Which is kind of a big deal, because:
a gap of one or more apneumatic vertebrae with pneumatic vertebrae on either side constitutes a pneumatic hiatus. Why thats a big deal is explained in this post.
If I had read this in the early 2000s, I would have flipped out. I did flip out when I discovered what seemed to be a pneumatic hiatus at the base of the tail in Haplocanthosaurus. Just that possibility sent me scurrying off to the Carnegie Museum to investigate, and precipitated both a dissertation chapter, later published as Wedel (2009), and an enduring fascination with Haplocanthosaurus. If Id been reading Lull instead of Hatcher, my air sac paper would have been about Barosaurus, probably, and I wouldnt have known enough about Haplo to get interested in the other specimens, which would have been a real shame.
A pneumatic hiatus in Barosaurus would have been big news in 2009. In 2021, its still nice, but not groundbreaking. The groundbreaking pneumatic hiatuses in Barosaurus were described in two different juvenile skeletons by Melstrom et al. (2016) and Hanik et al. (2017). Those were both mid-thoracic hiatuses, which probably separated the pneumatization domains of the cervical air sacs anteriorly and the abdominal air sacs posteriorly. A mid-sacral hiatus in YPM 429 is probably within the domain of the abdominal air sac, just like the hiatus in sacral 5 of CM 879 that I described in my 2009 paper. Its still exciting, in that it shows that there were abdominal air sacs, and they were separate from the lungs and cervical air sacs, but this example in YPM 429 is now third in line in terms of priority, just within this one genus. Which is why Im telling the world with a blog post, instead of hopping on a plane (or, er, planning a very long road trip) to New Haven. Ill check on YPM 429 the next time Im out there, but the specifics will keep for now.
ReferencesHanik, Gina M., Matthew C. Lamanna and John A. Whitlock. 2017. A juvenile specimen of Barosaurus Marsh, 1890 (Sauropoda: Diplodocidae) from the Upper Jurassic Morrison Formation of Dinosaur National Monument, Utah, USA. Annals of Carnegie Museum 84(3):253–263.Lull, R.S. 1919. The sauropod dinosaur Barosaurus Marsh. Memoirs of the Connecticut Academy of Arts and Sciences 6:1-42.Melstrom, Keegan M., Michael D. D’Emic, Daniel Chure and Jeffrey A. Wilson. 2016. A juvenile sauropod dinosaur from the Late Jurassic of Utah, USA, presents further evidence of an avian style air-sac system. Journal of Vertebrate Paleontology 36(4):e1111898. doi:10.1080/02724634.2016.1111898Wedel, M.J. 2009. Evidence for bird-like air sacs in saurischian dinosaurs. Journal of Experimental Zoology 311A:611-628. Posted by Matt WedelFiled in Barosaurus, diplodocids, pneumatic hiatus, pneumaticity
Leave a Comment I misconstrued the review history of the paper discussed in the last post: myapologies May 21, 2021
Two days ago, I wrote about what seemed to be an instance of peer review gone very wrong. Ive now heard from two of the four authors of the paper and from the reviewer in question — both by email, and in comments on the original post — and its apparent that I misinterpreted the situation. When the lead authors tweet mentioned pushing it through eight rounds of review, I took this at face value as meaning eight rounds at the same journal with the same reviewers — whereas in fact the reviewer in question reviewed only four drafts. (That still seems like too many to me, but clearly its not as ludicrous as the situation as I misread it.) In this light, my assumption that the reviewer was being obstructive was not warranted.
I have decided to retract that article and I offer my apologies to the reviewer, Dave Grossnickle, who approached me very politely off-list to offer the corrections that you can now read in his comment.
Posted by Mike TaylorFiled in I'm stupid, Peer review, stinkin' SV-POW!sketeers
2 Comments When peer-review goes bad reallybad. May 19, 2021
THIS POST IS RETRACTED. The reasons are explained in the next post. I wish I had never posted this, but you can’t undo what is done, especially on the Internet, so I am not deleting it but marking it as retracted. I suggest you don’t bother reading on, but it’s here if you want to.
Neil Brocklehurst, Elsa Panciroli, Gemma Louise Benevento and Roger Benson have a new paper out (Brocklehurst et al. 2021, natch), showing that the post-Cretaceous radiation of modern mammals was not primarily due to the removal of dinosaurs, as everyone assumed, but of more primitive mammal-relatives. Interesting stuff, and its open access. Congratulations to everyone involved!
Neil summarised the new paper in a thread of twelve tweets, but it was the last one in the thread that caught my eye:
Thanks to all my co-authors for their tireless work on this, pushing it through eight rounds of review (my personal best)
Im impressed that Neil has maintained his equanimity about this — in public at least — but if he is not going to be furious about it then we, the community, need to be furious on his behalf. Pushed to explain, Neil laid it out in a further tweet:
Was just one reviewer who really didnt seem to like certain aspects, esp the use of discrete character matrices. Fair enough, cant please everyone, but the editor just kept sending it back even when two others said our responses to this reviewer should be fine.
Again, somehow this tweet is free of cursing. He is a better man than I would be in that situation. He also doesnt call out the reviewer by name, nor the spineless handling editor, which again shows great restraint — though I am not at all sure its the right way to go.
There is so, so much to hate about this story:
The obstructive peer reviewer, who seems to have to got away with his reputation unblemished by these repeated acts of vandalism. (Im assuming he was one of the two anonymous reviewers, not the one who identified himself.)The handling editor who had half a dozen opportunities to put an end to the round-and-round, and passed on at least five of them. Do your job! Handle the manuscript! Dont just keep kicking it back to a reviewer who you know by this stage is not acting in good faith.The failure of the rest of the journals editorial board to step in and bring some sanity to the situation.The normalization of this kind of thing — arguably not helped by Neils level-headed recounting of the story as though its basically reasonable — as someting authors should expect, and just have to put up with.The time wasted: the other research not done while the authors were pithering around back and forth with the hostile reviewer.Its the last of these that pains me the most. Of all the comforting lies we tell ourselves about conventionl peer review, the worst is that its worth all the extra time and effort because it makes the paper better.
Its not worth it, is it?
Maybe Brocklehurst et al. 2021 is a bit better for having gone through the 3rd, 4th, 5th, 6th, 7th and 8th rounds of peer review. But if it is, then its a marginal difference, and my guess is that in fact its no better and no worse that what they submitted after the second round. All that time, they could have been looking at specimens, generating hypotheses, writing descriptions, gathering data, plotting graphs, writing blogs, drafting papers — instead they have been frittering away their time in a pointless and destructive conflict with someone whose only goal was to prevent the advancement of science because an aspect of the paper happened to conflict with a bee he had in his bonnet. We have to stop this waste.
This incident has reinforced my growing conviction that venues like Qeios, Peer Community in Paleontology and BiorXiv (now that its moving towards support for reviewing) are the way to go. Our own experience at Qeios has been very good — if it works this well the next time we use it, I think think its a keeper. Crucially, I dont believe our paper (Taylor and Wedel 2021) would have been stronger if it had gone through the traditional peer-review gauntlet; instead, I think its stronger than it would have been, because its received reviews from more pairs of eyes, and each of them with a constructive approach. Quicker publication, less work for everyone involved, more collegial process, better final result — whats not to like?
ReferencesBrocklehurst, Neil, Elsa Panciroli, Gemma Louise Benevento and Roger Benson. 2021. Mammaliaform extinctions as a driver of the morphological radiation of Cenozoic mammals. Current Biology. doi:10.1016/j.cub.2021.04.044Taylor, Michael P., and Mathew J. Wedel. 2021. Why is vertebral pneumaticity in sauropod dinosaurs so variable? Qeios 1G6J3Q. doi:10.32388/1G6J3Q Posted by Mike TaylorFiled in Look, this isn't complicated, Peer review, Shiny digital future
15 Comments Haplocanthosaurus neural canals are weird, part 2: getting comparative specimens from the grocerystore May 16, 2021
Anatomical features of the neural canal in birds and other dinosaurs. A. MWC 9698, a mid caudal vertebra of Apatosaurus in posterodorsal view. Arrows highlight probable vascular foramina in the ventral floor of the neural canal. B. LACM 97479, a dorsal vertebra of Rhea americana in left anterolateral view. Arrows highlight pneumatic foramina inside the neural canal. C. A hemisected partial synsacrum of a chicken, Gallus domesticus, obtained from a grocery store. Anterior is to the right. The bracket shows the extent of the dorsal recess for the glycogen body, which only spans four vertebrae. Arrows highlight the transverse grooves in the roof of the neural canal for the lumbosacral organ. D. Sagittal (left) and transverse (right) CT slices through the sacrum of a juvenile ostrich, Struthio camelus. The bracket shows the extent of the lumbosacral expansion of the spinal cord. Indentations in the roof of the neural canal house the lumbosacral organ. In contrast to the chicken, the ostrich has a small glycogen body that does not leave a distinct osteological trace. Yellow arrows show the longitudinal troughs in the ventral floor of the neural canal that house the ventral eminences of the spinal cord. Wedel et al. (2021: fig. 4).
This is the second in a series of posts on our new paper about the expanded neural canals in the tail vertebrae of the Snowmass Haplocanthosaurus. Im not going to talk much about Haplo in this post, though. Instead, Im going to talk about chickens, and about how you can see a lot of interesting spinal anatomy in a living dinosaur for about two bucks.
You know by now that Academia Letters publishes peer reviews, which is one of the things that drew me to this fairly new journal. More on that in a later post, but in the meantime, the peer reviews for the Haplo paper are on the right sidebar here. I confess, I had a total forehead-slap moment when I read the opening lines of Niels Bondes review:
This paper is interesting, and should be published and discussed by others with interest in dinosaur-bird relations. However, as these publications are also meant for the general public, I would recommend that 2 3 illustrations were added of the features mentioned for birds under nos. 3 6, because the general public (and many paleontologists) have no ideas about these structures, and what they look like.
The original submission only had figures 1 and 2. And this request is totally fair! If you are going to discuss six alternative hypotheses for some mysterious anatomical structure, its just responsible reporting to illustrate those things. That goes double if, as Niels Bonde noted, the anatomy in question is unfamiliar to a lot of people, even many paleontologists. Huxleys quote after first reading Darwins Origin of Species flashed through my head: How extremely stupid not to have thought of that.
Slide 21 of my 2014 SVPCA talk on supramedullary diverticula in birds and other dinosaurs, illustrating pneumatic foramina in the roof, walls, and floor of the neural canal.
At the time I read that review, I already had images illustrating five of the six hypotheses. A juvenile ostrich synsacrum that Jessie Atterholt and I had CT scanned gave us three of them all by itself: the lumbosacral expansion of the spinal cord to run the hindlimbs, as in all limbed tetrapods and in some fish with sensitive fins; the transverse channels in the dorsal wall of the neural canal to accommodate the lumbosacral balance organ; and the paired troughs in the floor of the neural canal that house the ventral eminences of the spinal cord (Figure 4D in the image at the top of this post). I had good photos of pneumatic foramina in the walls and floor of the neural canal in a dorsal vertebra of a rhea from my 2014 SVPCA talk (Figure 4B), and some photos of small foramina, presumably for blood vessels rather than air spaces, in the floor of the neural canal in a caudal vertebra of Apatosaurus (Figure 4A).
What I did not have is a photo illustrating the fairly abrupt, dome-shaped space in the sacral neural canal that houses the glycogen body of birds. I mean, I had published images, but I didnt want to wrestle with trying to get image reproduction rights, or with redrawing the images. Instead, I went to the grocery store to buy some chicken.
I dont know how universally true this is, but IME in the US when you buy a quartered chicken, the vertebrae are usually nicely hemisected by the band saw that separated the left and right halves of the animals. So you can see the neural canal in both the dorsal and sacral parts of the vertebral column. Here are the hemisected dorsal vertebrae in the breast quarter from a sectioned rotisserie chicken:
Thats just how it came to lie on my plate, but its not in anatomical position. Lets flip it over to sit upright:
And label it:
I could and probably should do a whole post just unpacking this image, but I have other fish to fry today, so Ill just note a couple of things in passing. The big interspinous ligament is the same one you can see in transverse section in the ostrich dissection photos in this post and this one. Also, the intervertebral joints heading toward the neck, on the left of the image, have much thicker intervertebral cartilage than the more posterior dorsals. Thats because the posterior ones were destined to fuse into a notarium. You can see a diagram and a photograph of a chicken notarium in figures 4 and 5, respectively, here. And finally, the big takeaway here is that the neural canal is normal, just a cylindrical tube to hold the spinal cord.
The thigh quarter usually has the pelvis and the hemisectioned synsacrum attached. Heres a lateral view of the left half of the pelvis and synsacrum:
And the same thing labeled:
And now flipped around so we can see it in medial view:
And now that image labeled:
And, hey, there are three of our alternative hypotheses on display: the long (many vertebral segments) lumbosacral expansion of the spinal cord, which is reflected in a gradually expanded neural canal in the synsacrum; the shorter, higher dome-shaped recess for the glycogen body; and finally the transverse spaces for the lumbosacral balance organ.
Borrowed from http://humanorgans.org/spinal-cord/
As a refresher, theres nothing terribly special about the lumbosacral expansion of the spinal cord you have one, labeled as the lumbar enlargement in the above diagram. Where the spinal cord has adjacent limbs to run, it has more neurons, so it gets fatter, so the neural canal gets fatter to accommodate it. The cord itself doesnt look very expanded in the chicken photo above, but that chicken has been roasted rotisserie-style, and a lot of lipids probably cooked out of the cord during that process. Whats more important is that the neural canal is subtly but unmistakably expanded, over the span of many vertebrae.
The lumbosacral spinal cord of a 3-week-old chick in dorsal view. The big egg-shaped mass in the middle is the glycogen body. Watterson (1949: plate 1).
Thats in contrast to the recess for the glycogen body, which is colored in blue in the chicken photo. Glycogen bodies, like the egg-shaped one in the young chicken in the image immediately above, tend not to go on for many vertebral segments. Instead they balloon up and subside over the space of just 4 or 5 vertebrae, so they leave a different skeletal trace than other soft tissues.
Finally, there are the transverse spaces for the lumbosacral balance organ, which I discussed in this post. Those are the things that look like caterpillar legs sticking up from the sacral endocasts in the above figure from Necker (2006). In life, the spaces are occupied by loops of meningeal membranes, through which cerebrospinal fluid can slosh around, which in turn puts pressure on mechanoreceptive cells at the edge of the spinal cord and gives birds a balance organ in addition to the ones in their heads. In the photo of the cooked chicken, the delicate meninges have mostly fallen apart, leaving behind the empty spaces that they once occupied.
I really liked that chicken synsacrum, and I wanted to use it as part of Figure 4 of the new paper, but it needed a little cleaning, so I simmered it for a couple of hours on low heat (as one does). And it promptly fell apart. At least in the US, most of the chickens that make it to table are quite young and skeletally immature. That particular birds synsacrum wasnt syn-anything, it was just a train of unfused vertebrae that fell apart at the earliest opportunity. I had anticipated that might be an issue, so Id gotten a lot of chicken, including a whole rotisserie chicken and four thigh quarters from the deli counter at the local supermarket. Happily this fried chicken thigh quarter had a pretty good neural canal:
And it cleaned up nicely:
And with a little cropping, color-tuning, and labeling, it was ready for prime time:
I didnt label them in the published version, for want of space and a desire not to muddy the waters any further, but the jet-black blobs I have colored in the lower part of that image are the exit holes that let the spinal nerves out of the neural canal so they could go serve the hindlimbs, pelvic viscera, and tail. We have them, too.
At my local grocery store, a fried chicken thigh costs about $1.65 if you get it standalone, or you can buy in bulk and save. You get to eat the chicken, and everything else Ive done here required only water, heat, soap, and a little time. The point is that if I can do this, you can do this, and if you do, youll get to see some really cool anatomy. I almost added, which most people havent seen, but given how much chicken we eat as a society these days, probably most peoples eyes have fallen on the medial surface of a cooked chicken thigh quarter at one time or another. Better to say, which most people havent noticed. But now you can. Go have fun.
Way back in January of 2019, I finished up Things to Make and Do, Part 25b with this line: I have one more thing for you to look for in your bird vertebrae, and that will be the subject of the next installment in this series. Stay tuned! Here we are, 2.3 years later, and Ive finally made good. So if theres a promised post youve been waiting for, stick around, we may get to it yet.
ReferencesNecker, R. 2006. Specializations in the lumbosacral vertebral canal and spinal cord of birds: evidence of a function as a sense organ which is involved in the control of walking. Journal of Comparative Physiology A, 192(5):439-448.Watterson, R.L. 1949. Development of the glycogen body of the chick spinal cord. I. Normal morphogenesis, vasculogenesis and anatomical relationships. Journal of Morphology 85(2): 337-389.Wedel, Mathew, Atterholt, Jessie, Dooley, Jr., Alton C., Farooq, Saad, Macalino, Jeff, Nalley, Thierra K., Wisser, Gary, Yasmer, John. 2021. Expanded neural canals in the caudal vertebrae of a specimen of Haplocanthosaurus. Academia Letters, Article 911, 10pp. Posted by Matt WedelFiled in anatomical preparations, chicken, dorsal, nervous system, neural canal, sacral, stinkin' theropods
1 Comment Haplocanthosaurus neural canals are weird, part 1: in which we tell theworld May 15, 2021
A. Recovered skeletal elements of Haplocanthosaurus specimen MWC 8028. B. Caudal vertebra 3 in right lateral view. C. The same vertebra in posterior view. Lines show the location of sections for D and E. D. Midsagittal CT slice. The arrow indicates the ventral expansion of the neural canal into the centrum. E. Horizontal CT slice at the level of the neural arch pedicles, with anterior toward the top. Arrows indicate the lateral expansions of the neural canal into the pedicles. B-E are shown at the same scale. Wedel et al. (2021: fig. 1).
New paper out today:
Wedel, Mathew; Atterholt, Jessie; Dooley, Jr., Alton C.; Farooq, Saad; Macalino, Jeff; Nalley, Thierra K.; Wisser, Gary; and Yasmer, John. 2021. Expanded neural canals in the caudal vertebrae of a specimen of Haplocanthosaurus. Academia Letters, Article 911, 10pp. DOI: 10.20935/AL911 (link)
The paper is new, but the findings arent, particularly. Theyre essentially identical to what we reported in our 1st Paleo Virtual Conference slide deck and preprint, and in the Tiny Titan exhibit at the Western Science Center, just finally out in a peer-reviewed journal, with better figures. The paper is open access and free to the world, and its short, about 1600 words, so this recap will be short, too.
A. Photograph of a 3D-printed model of the first three caudal vertebrae of Haplocanthosaurus specimen MWC 8028, including endocasts of the neural canal (yellow) and intervertebral joints (blue), in right lateral view, and with the neural canal horizontal. B. Diagram of the same vertebrae in midsagittal section, emphasizing the volumes of the neural canal (yellow) and intervertebral joint spaces (blue). Anterior is to the right. Wedel et al. (2021: fig. 2).
John Foster and I described Museum of Western Colorado (MWC) specimen 8028, a partial skeleton of Haplocanthosaurus from Snowmass, Colorado, in late 2014. One weird thing about that specimen (although not the only weird thing) is that the neural canals of the tail vertebrae are bizarrely expanded. In most vertebrae of most critters, the neural canal is a cylindrical tunnel, but in these vertebrae the neural canals are more like spherical vacuities.
John and I didnt know what to make of that back in 2014. But a few years later I started working with Jessie Atterholt on bird anatomy, which led me to do a little project on the whole freaking zoo of weird stuff that birds and other dinosaurs do with their neural canals, which led to the 1PVC presentation, which led to this.
Caudal vertebra 3 of Haplocanthosaurus specimen MWC 8028 in left posterolateral (A), posterior (B), and right posterolateral (C) views, with close-ups (D and E). In A and B, a paintbrush is inserted into one of the lateral recesses, showing that the neural canal is wider internally than at either end. Wedel et al. (2021: fig. 3).
Of course there will be more posts and more yapping, as signaled by the Part 1 in the post title. Although I am extremely satisfied with the streamlined, 1600-word missile of information and reasoning that just dropped, there are parts that I want to unpack, that havent been unpacked before. But the paper launched at midnight-thirty, Pacific Daylight Time, Im up way too late finishing this first post, and I reckon the rest will keep for a few hours at least.
Anatomical features of the neural canal in birds and other dinosaurs. A. MWC 9698, a mid caudal vertebra of Apatosaurus in posterodorsal view. Arrows highlight probable vascular foramina in the ventral floor of the neural canal. B. LACM 97479, a dorsal vertebra of Rhea americana in left anterolateral view. Arrows highlight pneumatic foramina inside the neural canal. C. A hemisected partial synsacrum of a chicken, Gallus domesticus, obtained from a grocery store. Anterior is to the right. The bracket shows the extent of the dorsal recess for the glycogen body, which only spans four vertebrae. Arrows highlight the transverse grooves in the roof of the neural canal for the lumbosacral organ. D. Sagittal (left) and transverse (right) CT slices through the sacrum of a juvenile ostrich, Struthio camelus. The bracket shows the extent of the lumbosacral expansion of the spinal cord. Indentations in the roof of the neural canal house the lumbosacral organ. In contrast to the chicken, the ostrich has a small glycogen body that does not leave a distinct osteological trace. Yellow arrows show the longitudinal troughs in the ventral floor of the neural canal that house the ventral eminences of the spinal cord. Wedel et al. (2021: fig. 4).
I have a ton of people to thank. John Foster, obviously, for initiating the line of research that led here. Julia McHugh for access to the MWC collections, and for being an excellent sounding board regarding the Morrison Formation, sauropod dinosaurs, and crafting ambitious but tractable research projects. Anne Weil for helping me be methodical in thinking through the logic of the paper, and Mike Taylor for helping me get it polished. Niels Bonde, Steven Jasinski, and David Martill for constructive reviews, which were published alongside the paper. We couldnt take all of their suggestions because of space limitations, but figures 3 and 4 were born because they asked for them, and thats not a small thing. Vicki and London Wedel for putting up with me at various points in this project, especially in the last few days as Ive been going bonkers correcting page proofs. And finally, because Im the one writing this blog post, my coauthors: Jessie Atterholt, Alton Dooley, Saad Farooq, Jeff Macalino, Thierra Nalley, Gary Wisser, and John Yasmer, for their contributions and for their patience during the unusually long gestation of this very short paper.
More to say about all that in the future. For now, yay, new paper. Have fun with it. Heres the link again.
ReferencesFoster, J.R., and Wedel, M.J. 2014. Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado. Volumina Jurassica 12(2): 197–210. DOI: 10.5604/17313708 .1130144Wedel, Mathew, Atterholt, Jessie, Dooley, Jr., Alton C., Farooq, Saad, Macalino, Jeff, Nalley, Thierra K., Wisser, Gary, Yasmer, John. 2021. Expanded neural canals in the caudal vertebrae of a specimen of Haplocanthosaurus. Academia Letters, Article 911, 10pp. DOI: 10.20935/AL911 Posted by Matt WedelFiled in caudal, chicken, Haplocanthosaurus, nervous system, neural canal, new papers, ostrich, papers by SV-POW!sketeers, rhea, stinkin' theropods, Tails
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(2016) on moral dimensions ofopen Hone, Farke, and Wedel (2016) on dinosaur ontogeneticstages Taylor (2016) on evaluatingresearch Taylor (2015) on incompletenecks Wedel et al. on apatosaur neckcombat Upchurch, Mannion and Taylor (2015) on Haestasaurusbecklesii Kraatz, Sherratt, Bumacod, and Wedel (2015) on rabbitskulls Taylor (2014) on quantifying neckcartilage Foster and Wedel (2014) on the Snowmass Haplocanthosaurus Farke, Cifelli, Maxwell, and Wedel (2014) onAquilops Taylor (2014 for 2004) on dinosaurdiversity Wedel and Taylor (2013b) on caudalpneumaticity Taylor and Wedel (2013b) on neckcartilage Wedel and Taylor (2013a) on sauropod neural spinebifurcation Taylor and Wedel (2013a) on sauropod neckanatomy Wedel (2012) on long nerves ofsauropods Yates, Wedel, and Bonnan (2012) on prosauropodpneumaticity Taylor, Hone, Wedel and Naish (2011) on sexual selection of sauropodnecks Taylor, Wedel and Cifelli (2011) on Brontomerus Taylor (2010) on the history of sauropodresearch Taylor (2009) on the inevitability of electronic publishing of nomenclaturalacts Taylor (2009) on Brachiosaurus and Giraffatitan Taylor, Wedel and Naish (2009) on neckposture Upchurch, Martin, and Taylor (2009) on Cetiosaurus nomenclature Wedel (2009) on airsacs Taylor and Naish (2007) on XenoposeidonAll the MuseumAbbreviationsChecklist for new zoological genus and species names [DRAFTv3]Open Access Bio and Paleo[UNMAINTAINED] Categories100% totally real Apatosaurus Art brachiosaurids Brachiosaurus caudal cervical collections diplodocids Diplodocus dorsal Giraffatitan goofy mounts museums navel blogging necks open access papers by SV-POW!sketeers pneumaticity rants Shiny digital future size stinkin appendicular elements stinkin heads stinkin mammals stinkin publishers stinkin theropods timely titanosaur Archives October 2021 September 2021 August 2021 June 2021 May 2021 April 2021 March 2021 February 2021 January 2021 December 2020 November 2020 October 2020 September 2020 August 2020 July 2020 June 2020 May 2020 April 2020 March 2020 February 2020 January 2020 December 2019 November 2019 October 2019 September 2019 August 2019 July 2019 June 2019 May 2019 April 2019 March 2019 February 2019 January 2019 December 2018 November 2018 October 2018 September 2018 August 2018 July 2018 June 2018 May 2018 April 2018 March 2018 February 2018 January 2018 December 2017 November 2017 October 2017 September 2017 August 2017 July 2017 June 2017 May 2017 April 2017 March 2017 February 2017 January 2017 December 2016 November 2016 October 2016 September 2016 August 2016 July 2016 June 2016 May 2016 April 2016 March 2016 February 2016 January 2016 December 2015 November 2015 October 2015 September 2015 August 2015 July 2015 June 2015 May 2015 April 2015 March 2015 February 2015 January 2015 December 2014 November 2014 October 2014 September 2014 August 2014 July 2014 June 2014 May 2014 April 2014 March 2014 February 2014 January 2014 December 2013 November 2013 October 2013 September 2013 August 2013 July 2013 June 2013 May 2013 April 2013 March 2013 February 2013 January 2013 December 2012 November 2012 October 2012 September 2012 August 2012 July 2012 June 2012 May 2012 April 2012 March 2012 February 2012 January 2012 December 2011 November 2011 October 2011 September 2011 August 2011 July 2011 June 2011 May 2011 April 2011 March 2011 February 2011 January 2011 December 2010 November 2010 October 2010 September 2010 August 2010 July 2010 June 2010 May 2010 April 2010 March 2010 February 2010 January 2010 December 2009 November 2009 October 2009 September 2009 August 2009 July 2009 June 2009 May 2009 April 2009 March 2009 February 2009 January 2009 December 2008 November 2008 October 2008 September 2008 August 2008 July 2008 June 2008 May 2008 April 2008 March 2008 February 2008 January 2008 December 2007 November 2007 October 2007 Blogroll 10 Minute Astronomy@MikeTaylor on TwitterDarren NaishEcho Station 5-7Matt WedelMike TaylorScholarly Closed AccessThe Open Dinosaur ProjectThe Reinvigorated Programmer RSSRSS - PostsRSS - CommentsBlog Stats 4,449,035 hits Blog at WordPress.com. 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