The full story on Morosaurus lentus

February 14, 2014

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:

x

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.

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8 Responses to “The full story on Morosaurus lentus

  1. Marco Says:

    Hi, excellent post sa always!
    A little of topic question:
    How many Camarasaurus species are Now valid?

    Thank you
    Marco

  2. Mike Taylor Says:

    Thanks!

    I don’t think anyone knows how many valid species of Camarasaurus there are. That group is way overdue for re-study. As far as I know there’s never been a single phylogenetic analysis that treated Camarasaurus as anything more fine-grained than a single OTU. My best guess is that there are a fair few species, and that when someone takes the trouble to look at them in detail they’ll conclude that multiple genera are warranted. But that’s just my intuition, don’t ask me to justify it.

  3. Matt Wedel Says:

    I believe that the canonical response here is, “Damn, if my sauropod was that ugly, I’d graft a pseudohead on its tail and teach it to walk backwards.”

  4. LeeB Says:

    Ikejiri did some work on Camarasaurus species; see his paper here: http://nmgs.nmt.edu/publications/guidebooks/downloads/56/56_p0367_p0379.pdf

    LeeB.

  5. Mike Taylor Says:

    Oh, that’s important! I can’t believe I’d never seen it before, thanks for the pointer!

  6. Mark Robinson Says:

    Just so I’m clear, the Diplodocus-type chevrons are not actually present where we have those particular Camarasaurus caudal verts?

  7. Mike Taylor Says:

    Correct — it’s just Diplodocus-type sculptures of chevrons.


  8. […] on SV-POW! — we’ve often shown individual bones, but the mounted skeleton appears only in the background of the much less impressive Morosaurus (= Camarasaurus) lentus mount. We’ll fix that real […]


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