In the first installment in this series (link), we looked at a couple of weird sauropod vertebrae with neurocentral joints that were situated either entirely dorsal or ventral to the neural canals. This post has more examples of what I am calling “offset” neurocentral synchondroses.

I decided it made more sense to refer to the synchondrosis as being offset, instead of referring to the neural canal as offset. Because the neural canal in all of these vertebrae is right where it pretty much always is, just dorsal to the articular surfaces of the centrum. In an adult, fused vertebra, there’d be no sign that anything unusual had ever happened. So I think it makes more sense to talk about the neurocentral joint having migrated dorsally or ventrally relative to the canal, rather than vice versa. If you know differently, or if these weirdos have been addressed before elsewhere and I’ve just missed it, please let me know in the comments!

Here’s a plate from Marsh (1896) showing caudal vertebrae of Camarasaurus (“Morosaurus” in O.C. Marsh parlance), which echo the Alamosaurus caudal from the first post in having the neurocentral joint almost entirely ventral to the neural canal. The neural arch here doesn’t just arch over the canal dorsally, it also cuts under it ventrally, at least in part.

This plate is also nice because it shows the relationships among the arch, centrum, and caudal ribs before they fuse. Here’s the caption, from Marsh (1896):

Here’s the preceding plate, Plate 33, with illustrations of an unfused Camarasaurus sacrum.

And its caption:

This plate not only shows how the sacral ribs fuse to the arch and spine medially, and to each other laterally (forming the sacrocostal yoke), it also shows a last sacral that is very similar to the aforementioned caudals in the position of the neurocentral joint. But interestingly that neurocentral joint offset only seems to be present in the last caudal sacral – the lower figure shows widely-separated neurocentral joint surfaces in the more anterior centra, indicating that the neural arches (not figured in this dorsal view) did not wrap around the neural canal to approach the midline. (I think we’re looking at S2 through S5 here, and missing a dorso-sacral.)

So now I’m freaked out, wondering if this neural arch wrap-around in the caudals is common to most sauropods and I just haven’t looked at enough juvenile caudals to have spotted it before. As always, feel free to ablate my ignorance in the comments, particularly if you know of more published examples. I’m a collector.

The neural canal of that last sacral also has a very interesting cross-sectional shape, like a numeral 8. I have some thoughts on that, but they’ll keep for a future post in this series.

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Last time, we took a very quick look at YPM 1910, a mounted skeleton that is the holotype of Camarasaurus (= “Morosaurus“) lentus, in the dinosaur hall of the Yale Peabody Museum.

Here’s the whole skeleton, in various views. Skip down to the bottom for the science; or just enjoy the derpiness. First, in anterior view:

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Here’s a more informative right anterolateral view. As you can see, this little Camarasaurus is in every sense in the shadow of the the much more impressive Apatosaurus (= “Brontosaurus“) excelsus holotype, YPM 1980: click through for the full image:

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And here’s the corresponding photo from Lull (1930: figure 1) (see below):

Camarasaurus lentus, holotype skeleton, oblique front view (Full 1930: fig. 1)

Camarasaurus lentus, holotype skeleton, oblique front view (Lull 1930: fig. 1)

It’s interesting to see such a familiar mount in such unfamiliar surroundings. Judging by the cabinets in the background, YPM 1910 was mounted in what’s now the dinosaur hall at Yale — i.e. it hasn’t moved since the photo was taken. But back then, Brontosaurus hadn’t been mounted, and Zallinger’s mural hadn’t been painted.

If you thought this animal looked dumb from the front, check out this left anterodorsolateral view, taken from the balcony above the hall. The foreshortening of the neck makes Cam look like a particularly dense puppy.

(Once more, click through for the full version of the photo, including the much more impressive Apatosaurus.)

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Right lateral view, with Zallinger’s justly famous mural in the background. Note the Diplodocus-type double-beamed chevrons in the tail:

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Here’s the justly under-rated posterior view:

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And finally, Lull’s left posterolateral photo — taken from a position that can’t now be replicated, due to the inconveniently located Brontosaurus. (The Archelon in the background, which was previously featured on SV-POW!, has been moved to the end of the hall since Lull’s time.

Camarasaurus lentus, oblique rear view. Lull (1930: fig. 2)

Camarasaurus lentus, oblique rear view. Lull (1930: fig. 2)

How much of this skeleton is real? Happily, not the skull. We can only hope that the real thing wasn’t quite so troubling. But much of the rest of the skeleton is real bone. To quote Lull (1930:1-3):

In the Yale specimen the entire vertebral column is present from the second or third cervical to the tenth caudal with one or two later caudals. Of the limbs and their girdles there are present the left scapula, right coracoid, both humeri, the left radius and ulna, both ilia, the right pubis and left ischium, and both femora, tibiae and fibulae. One cervical rib is present but no thoracic ribs. The disarticulated sacrum lacked one rib from either side.

(How could Lull have been unsure whether the most anterior preserved cervical was the second or third? C2 in sauropods, as in most animals, is radically different from the subsequent cervicals. He does go on to say that only the centrum of the most anterior vertebra is preserved, but the axis has a distinct anterior central articulation.)

Lull is quite ready to criticise the mount, and notes in particular:

The cervical ribs in the Yale mount are not long enough by half, and the thoracic ribs may be somewhat heavy and their length a little short […] both carpus and tarsus are probably incorrect, as the elements in each instance are fewer than shown, there being no more than two at most. There is apparently no justification for the fore and aft extensions of the distal chevrons, as these were not preserved and the Osborn-Mook restoration was followed. […] A probable error lies in too great an allowance for cartilage between the [pelvic] elements, thus making the acetabulum seem rather large.

He also notes a scheme that sadly never came to pass:

[The holotype of Camarasaurus (= “Morosaurus“) robustus], a very perfect specimen, we intend to mount when the great Brontosaurus excelsus type is completed. The three sauropods, ranging in length from 21 to nearly 70 feet, should make a very impressive group.

They would have done! But in the end it fell to the Museum für Naturkunde Berlin to give us the world’s first three-sauropod combo (unless someone knows of an earlier one?)

Finally; the mounted Yale Camarasaurus also crops up in three of the plates of Ostrom and McIntosh (1966). Plate 60 depicts metacarpals I and II in all the cardinal views except for some reason posterior; plate 61 does the same for metacarpals III and IV); and plate 70 shows the right pubis in every aspect but anterior. Here it is:

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Morosaurus lentus [Now referred to Camarasaurus lentus] Marsh (1889) YPM 1910 (holotype). Right pubis (reversed) in medial (1), posterior (2), lateral (3), proximal (4), and distal (5) views; transverse sections through blade (6) and shaft (7). (Ostrom and McIntosh 1966: plate 70)

Judging by this, it’s a beautifully preserved element with some very distinctive morphology. But we’ve been burned by Marsh’s plates before, and I don’t trust them at all any more — at least, not until I’ve seen the elements for myself. Now I wish I paid more attention to Derpy’s pubes.

And on that line, I’m out.

References

Lull, Richard S. 1930. Skeleton of Camarasaurus lentus recently mounted at Yale. American Journal of Science, 5th series, 19(109):1-5.

Ostrom, John H., and John S. McIntosh. 1966. Marsh’s Dinosaurs: the Collections from Como Bluff. Yale University Press, New Haven, CT. 388 pages including 65 positively scrumptious plates.

Matt’s harsh-but-fair “Derp dah durr” / “Ah hurr hurr hurr” captions on his Giraffatitan skull photos reminded me that there is a sauropod with a much, much stupider head than that of Giraffatitan. Step forward YPM 1910, a mounted skeleton that is the holotype of Camarasaurus (= “Morosaurus“) lentus, in the dinosaur hall of the Yale Peabody Museum. Herp derp derp Full details on this specimen next time! (But a spoiler: the skull isn’t real.)

Probably everyone who reads SV-POW! already knows that the manus, or forefoot, or sauropods was very distinctive.  The metacarpal bones, rather than being splayed out horizontally as in the forefeet of most animals, were arranged more or less vertically in a horseshoe shape, hence the characteristic shape of sauropod manus prints.

This was first recognised by Osborn (1904), a paper which contains the greatest single sentence in any scientific paper:

My previous figures and descriptions of the manus are all incorrect.

Here is the rather beautiful illustration from that paper (fig. 1):

It depicts the right manus, in anterior view,  of AMNH 965, “Morosaurus” sp.  As described by Osborn and Mook (1921:376-377), that genus was subsequently synonymised with Camarasaurus by Mook (1914), following the earlier suggestion of Osborn (1898), and this synonymy is universally accepted — for now, at least.

If anything, trackway evidence suggests that this illustration shows the metacarpals insufficiently vertical, resulting in the manus being too splayed out.

I have nothing more to say about that; just wanted to post the illustration because it’s beautiful and out of copyright (so feel free to use it however you want!)

References

  • Mook, Charles C.  1914.  Notes on Camarasaurus Cope.  Annals of the New York Academy of Science 24:19-22.
  • Osborn, Henry F.  1898.  Additional characters of the great herbivorous dinosaur Camarasaurus.  Bulletin of the American Museum of Natural History 10: 219-233.
  • Osborn, Henry F.  1904.  Manus, sacrum and caudals of Sauropoda.  Bulletin of the American Museum of Natural History 20:181-190.
  • Osborn, Henry Fairfield, and Charles C. Mook.  1921.  Camarasaurus, Amphicoelias and other sauropods of Cope.  Memoirs of the American Museum of Natural History, n.s. 3:247-387, and plates LX-LXXXV.