What about the forearm of “Pelorosaurusbecklesii?

June 2, 2015

Yesterday, we looked at (mostly) the humerus of the Wealden sauropod “Pelorosaurusbecklesii, which you will recall is known from humerus, radius, ulna and a skin impression, and — whatever it might be — is certainly not a species of Pelorosaurus.

Now let’s look at the radius and ulna.

Left forearm of

Left forearm of “Pelorosaurusbecklesii holotype NHMUK R1870, articulated, in anterior view, with proximal to the left: radius in front, ulna behind.

They fit together pretty neatly: the proximal part of the radius is a rounded triangular shape, and it slots into the triangular gap between the anteromedial and anterolateral processes of the proximal part of the ulna.

Left forearm of “Pelrosaurus” becklesii holotype NHMUK R1870 in proximal view, with anterior to the right. The arms of the ulna enclose the radius.

Left forearm of “Pelorosaurusbecklesii holotype NHMUK R1870 in proximal view, with anterior to the right. The “arms” of the ulna enclose the radius.

Let’s take a closer look at the ulna:

Left ulna of

Left ulna of “Pelorosaurusbecklesii holotype NHMUK R1870. Top row: proximal view, with anterior to the bottom. Middle row, from left to right: medial, anterior, lateral and posterior views. Bottom row: distal view, with anterior to top.

And the radius:

Left radius of

Left radius of “Pelorosaurus” becklesii holotype NHMUK R1870. Top row: proximal view, with anterior to the bottom. Middle row, from left to right: medial, anterior, lateral and posterior views. Bottom row: distal view, with anterior to top.

As you can see, it’s pretty well preserved: there’s no evidence of significant crushing in any of the bones, and the 3d shape is apparent.

In short, it’s a really sweet specimen. Someone really ought to get around to describing it properly, and giving it the new generic name that it clearly warrants.

15 Responses to “What about the forearm of “Pelorosaurusbecklesii?”

  1. Frosted Flake Says:

    Beautiful. The texture is visible and seems fresh. The broken areas provide opportunity to observe the interior structure. Am I looking at marrow? That seems unlikely. Could you please comment about the layers visible in the cracks? Are the surfaces of the joints typical? They seem a bit arthritic. Thank you for the ‘big picture’. Is there a close-up of that crack available?

    A very nice specimen. Thanks.

  2. Mike Taylor Says:

    Well, Frosted Flake, I don’t know about marrow, but that would be the obvious interpretation of what we’re seeing at the broken ends. (Note: this refers to an image in the previous post, not this one.) I’m really not the person to comment on the detail in the cross-sections, though.

    The surfaces of the joints are perfectly good, non-arthritic, sauropod joints, though. Unlike the bones of mammals, which articulate closely together with only a thin layer of cartilage, those of sauropods had very thick cartilaginous ends, like those of bird bones, which dramatically altered the functional shapes of the joints. (I must blog about this properly some time.)

  3. Aaron Natera Says:

    Do we get to see the skin impression?

  4. Mike Taylor Says:

    I wouldn’t rule it out :-)

  5. […] of the Wealden-supergroup putative titanosaur “Pelorosaurus” becklesi. We’ve seen the bones of the forearm, the radius and ulna. That’s it for bony remains: no other bones have been […]

  6. John Scanlon Says:

    ‘Marrow’ would refer to a soft tissue, so that’s probably not what we’re seeing on the previous post. I don’t know from sauropod limbs, but the mineral infill seems to be in a simple tubular cavity rather than (e.g.) the interspaces of trabecular bone, but that’s to be expected at mid-shaft in any group, probably. Bones broken open before burial would get filled with mud which usually ends up pretty much the same as the matrix outside. But assuming the matrix is more or less calcareous (expected for Wealden, yes?), an intact bone will have its internal cavities filled mainly with crystalline calcite, the insoluble sediment particles being filtered out by the bone. In the cross-sections the crystals appear to be bimodal in size and colour, but I suspect the yellow material is actually old glue rather than a different mineral. Other stuff (organic residues, iron and manganese oxides etc.) gets concentrated in the gaps between the calcite crystals, often as dendrites, lending a lot of black.

  7. […] who knew? There I was posting images of “Pelorosaurus” becklesi‘s humerus, radius and ulna, and skin impression. There I was saying that this beast is due a proper description, and warrants […]

  8. Bump!

    Since this post had to do a lot with an ulna I think I may as well ask here.
    Anyone interested in a potential >100 tonne sauropod ulna from the Kem Kem?

  9. Mike Taylor Says:

    Of course! Do you have a link?

  10. Here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7188693/

    They describe this ulna as 54 cm across the proximal end, which appears to be quite larger than that measurement in many other titanosaurs going by what I measured in scalebars in skeletals. This is how it sizes up against those titanosaurs:

    -33.3 meters and 106.8 tonnes based on Futalognkosaurus (38.1 tonnes, 38.3 cm proximal ulna width, measurement and length from SpinoInWonderland skeletal, mass based on Benson 2014)

    -35.6 meters and 109.9 tonnes based on Malawisaurus (3.25 tonnes, 16.7 cm proximal ulna width, measurement and length from Palaeozoologist’s skeletal, mass based on his estimate with some extra meat).

    -34.1 meters and 97.6 tonnes based on Antarctosaurus (14.4 tonnes, 28.5 cm proximal ulna width, measurement and length from Ornithopsis, mass based on Mazzetta 2004).

    No matter how you slice it, this looks very sizeable.

  11. Mike Taylor Says:

    Thanks for this link. Oddly, the article says the measurement across its proximal articular end is 54 cm (page 64) but then downgrades it to 51 cm (page 130). Not sure what’s going on there.

    Anyway, even at 51 cm it seems to be transversely bigger than the ulna of the Giraffatitan brancai paralectotype MB.R.2181 (formerly HMN SII), which remains the benchmark for big sauropods. For this bone, Janensch (1961:191) gives two proximal widths: 44.5 cm based on the medial wing and 37.5 cm based on a lateral — presumably both measured from the extremity of the “wing” to the olecranon. That makes it hard to compare directly, but Beilage A (between pages 186 and 187) shows the ulna in proximal view and its apparent that the maximum width across both wings is less than the distal width of the humerus, which is drawn to same scale in the same illustration. Janensch (1961: table 3) gives the distal width of that humerus as 51 cm, suggesting the ulna’s width is a little less, perhaps 48 cm.

    So the Kem Kem ulna is big.

  12. I had that same issue with 54 vs 51 cm too! First I read 54, than thought I read 51, then dismissed it as misreading, but it’s good to see I’m not alone there.
    In any case, it seems to me as though the 51 cm is probably a typo, since using the scalebar gives about 54 cm by my measurement.

    For comparing with Giraffatitan, I think Janesch’s 37.5 cm is probably the same metric as the 54 cm for this ulna as it matches up nicely with what the scalebar in Paleo King’s skeletal gives. And since it’s described as ‘lateral’, that’s further support for 37.5 cm and 54 cm being the same metric because the olecranon of the ulna is most prominent in the lateral plane.

    And yes, even if we base it on a long-armed brachiosaurid which it almost certainly was not, it’s still plenty big. With the above measurements it’s some 36% larger than HMN SII, which Larramendi and Molina (2020) had as 23 meters and 35 tonnes. Based on that very likely too low figure, it already ends up at 31.3 meters and 88 tonnes.

    All things considered, I think that whatever this is thoroughly blows the 2 other giant African sauropods (Paralititan and Giraffatitan) right out of the water.

  13. Matt Wedel Says:

    Relevant: according to the SI from Carballido et al. (2017) on Patagotitan, the ulna of MPEF-PV 3399/27 is 52.5 cm across at the proximal end. So the Kem Kem ulna is legitimately huge.

    That said, the new paper by Otero et al. in JVP puts the mass of Patagotitan at possibly only 60-70 tons. From their abstract:

    “In the light of a modification of the scaling equation previously proposed and adjusting the long bone circumference for the humeri of Patagotitan, a new body mass estimate of this species ranges between 42–71 tons, with a mean value of 57 tons. Although
    considerably less than the value obtained by the original linear equation, the corrected quadratic equation used here provides a mean body mass estimate that is more consistent with those derived from volumetric reconstructions of Patagotitan.”

    So Patagotitan-class isn’t necessarily a 100-tonner.

  14. I see. That new equation is pleasingly consistent with the volumetric models, much more than the older one from 2012; I think I should email Campione and Evans and see what they think about it.

    As for a Patagotitan-based Kem Kem ulna, I believe you’re right in that while it would still be very large, it wouldn’t be a 100-tonner.
    However, I do think the Malawisaurus, Futalognkosaurus, and Antarctosaurus based estimates are most likely closer to the mark, for 1 reason – Patagotitan’s ulna is quite a bit more anteroposteriorly expanded/elongated at the proximal end than any of these taxa as well as the Kem Kem ulna. If you take a look at the 2020 paper on its appendicular osteology you will see what I mean. Considering this, it appears to me the differently shaped ulna of Patagotitan may artificially drag down the weight if you were to use it as a base for the Kem Kem ulna.

    One last thing: I recall Greg Paul (2019) noting in his paper about giant sauropods that out of all places where giant sauropods were found, Africa was somewhat sparse on them so far. Considering this ulna as well as the potential 1.88 meter humerus from Ibrahim (2016), I think that could be just an artifact of bad sampling.

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