Equatorial Minnesota on Alamosaurus

February 21, 2021

Figure 3. BIBE 45854, articulated series of nine mid and posterior cervical vertebrae of a large, osteologically mature Alamosaurus sanjuanensis. Series is estimated to represent the sixth to fourteenth cervical vertebrae. A, composite photo-mosaic of the cervical series in right lateral view; identification of each vertebra indicated by C6 to C14, respectively. B, line drawing based on the photo-mosaic in A. C, line drawing in B with labels shown and vertebral fossae indicated by solid grey fill; cross-hatching represents broken bone surfaces and reconstructive material. Abbreviations: C, cervical vertebra; cdf, centrodiapophyseal fossa; clf, centrum lateral fossa; pocdf, postzygapophyseal centrodiapophyseal fossa; prcdf, prezygapophyseal centrodiapophyseal fossa; prcdf1, dorsal prezygapophyseal centrodiapophyseal fossa; prcdf2, ventral prezygapophyseal centrodiapophyseal fossa; sdf, spinodiapophyseal fossa; spof, spinopostzygapophyseal fossa; sprf, spinoprezygapophyseal fossa. (Tykoski and Fiorillo 2016)

Have you been reading Justin Tweet’s series, “Your Friends the Titanosaurs“, at his awesomely-named blog, Equatorial Minnesota? If not, get on it. He’s been running the series since June, 2018, so this notice is only somewhat grotesquely overdue. The latest installment, on Alamosaurus from Texas and Mexico, is phenomenal. I have never seen another summary or review that pulled together so much of the relevant literature and explained it all so well. Seriously, that blog post deserves to be a review paper; it could be submitted pretty much as-is, although it would be even better with his two other Alamosaurus posts integrated (this one, and this one). It’s great work, is what I’m saying, and it needs to be acknowledged.

In particular, I was struck by the note by Anonymous in 1941 on the discovery of a cervical vertebra 1.2 meters long. I’d never heard of that ref, and I’ve never seen that vert, but at 120cm it would be in the top 7 longest cervical vertebrae on the planet (see the latest version of the list in this post), narrowly beating out the 118-cm cervical of Puertasaurus. In fairness, the preserved cervical of Puertasaurus is probably a posterior one, and more anterior cervicals might have been longer. Then again, in the big Alamosaurus neck the longest verts are pretty darned posterior, so…we need more Puertasaurus.

EDIT a few hours later: Thanks to the kind offices of Justin Tweet, I’ve now seen Anonymous (1941), and the exact wording is, “A single vertebra, or neck joint bone, is three feet across, only two inches less than four feet long, and in its present fossilized state weighs 600 pounds.” ‘Two inches less than four feet long’ is 46 inches or a hair under 117cm, which puts the supposed giant cervical just behind Puertasaurus after all, but still firmly in the top 10. And depending on how one interprets the passage in Anonymous (1941), it might not have been any bigger than BIBE 45854–see this comment for details.

Big cervical showdown. From the top left: BYU 9024, originally referred to Supersaurus but more likely representing a giant Barosaurus (137cm); the single available cervical of Puertasaurus (118cm); a world-record giraffe neck (2.4m); Alamosaurus referred cervical series BIBE 45854, longest centra are ~81cm; Sauroposeidon holotype OMNH 53062, longest centrum is 125cm. This image makes it very clear that whatever Sauroposeidon was doing, it was a way different thing from Alamosaurus.

Crucially, the longest vertebrae in the BIBE 45854 series are about 80 or 81 cm long, which means that a 1.2-meter cervical would be half again as large. That is a pretty staggering thought, and that individual of Alamosaurus–assuming it was the same taxon as BIBE 45854, and not some other, longer-necked critter–would definitely be a contender for the largest sauropod of all time.

Illustrations here are of the big Alamosaurus cervical series from Big Bend, which was comprehensively described by Ron Tykoski and Tony Fiorillo in 2016, and which we have covered in these previous posts:

References

  • Anonymous. 1941. Find dinosaur neck bone nearly four feet long. The Science News-Letter 39(1):6–7.
  • Tykoski, R.S. and Fiorillo, A.R. 2016. An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America’s last giant sauropod. Journal of Systematic Palaeontology 15(5):339-364.

11 Responses to “Equatorial Minnesota on Alamosaurus

  1. Justin Tweet Says:

    Thank you very much for the compliments! I’ve always appreciated the work over here, so being recognized like this is an accomplishment.

    Checking through the AMNH’s online database, a couple of candidates present themselves. AMNH FR (or FARB) 3080 is a vertebra listed as Alamosaurus? sp. The stratigraphy is given as the upper Aguja, but that would need to be checked against modern stratigraphic definitions. There’s also 21579, cervical vertebrae and fragments collected by Brown, listed as just Saurischia (also from the Aguja).

  2. Matt Wedel Says:

    Fantastic! Now I have things to look for the next time I’m at the AMNH.

    …one thing belatedly occurred to me: Anonymous (1941) described the vert as, “three feet across, only two inches less than four feet long”, or roughly 92cm by 117cm. I note that the largest cervicals of BIBE 45854 are taller than long, and I can’t help but wonder if the dimensions reported by Anonymous are the biological width and length, or just the ‘width’ and ‘length’ of the specimen as it lay in its jacket. Because the last cervical of BIBE 45854 is 117.5cm tall from the bottom of the cervical rib to the top of the neural spine, and 98.4cm wide across the diapophyses, so in some orientations it’s a pretty good match for the dimensions reported by Anonymous (1941). If the choice is between, “news writer accidentally words brief report to suggest an unintended biological orientation”, and “hellacious Alamosaurus was half again as large as mounted giant in Dallas”, then I gotta say, the former is a lot more plausible.

  3. TA Holmes Says:

    Is the Anonymous (1941) vertebra really that hellacious? Using the 1.17m gives you an animal that’s about 45% longer and 3 times heavier than BIBE 45854, which is about the size of Argentinosaurus (~35 meters and ~70-80 tonnes). That’s real big, but fits with other reports of giant “Alamosaurus” material like the Fowler and Sullivan vertebrae.

  4. Matt Wedel Says:

    The vertebrae described by Fowler and Sullivan (2011) are little if any bigger than BIBE 45854. Their big cervical cotyle is 26×50 cm, compared to 29×42 cm for the last vert in the BIBE 45854 series. Their big caudal centrum has a max articular face of 26.5×32.5cm, which is big but not _that_ big. The new possibly-bigger-than-Patagotitan specimen described by Otero et al. (2021) has 3 proximal caudals that are all approximately 41x40cm. OMNH 1331, possibly a first caudal centrum from the giant apatosaurine, was about 40x49cm when complete, but apatosaurines are notoriously big-assed.

    A 1.17-meter-long cervical really would be a big deal because Alamosaurus is not a terribly long-necked sauropod, proportionally. As the second image in this post shows, if you scaled up BIBE 45854 until its cervicals were as long as those of Sauroposeidon (~1.2m), it would be ungodly huge. Maybe such a cervical exists, but extraordinary claims and all that.

  5. Ronald Says:

    The preserved cervical centrum of SMP VP-1850 in the 2011 Fowler & Sullivan paper has a max. diameter of 63 cm, estimated restored of 70 cm.

  6. Matt Wedel Says:

    The preserved cervical centrum of SMP VP-1850 in the 2011 Fowler & Sullivan paper has a max. diameter of 63 cm, estimated restored of 70 cm.

    That is partly true, but mostly misleading for the purposes of this discussion, for several reasons. Fowler and Sullivan (2011: Table 1) report 3 widths for that vertebra:
    – a preserved maximum centrum width (not diameter–and that’s an important distinction) of 63cm, estimated 70cm when intact;
    – a preserved maximum width across the parapophyses of 71cm;
    – a cotyle width of 50cm.

    The “preserved maximum centrum width” can’t correspond to either the cotyle width or the parapophysis width, because those are reported separately. It’s not super-clear what it does correspond to, but in the posterior view a bit of the posterior centro-diapophyseal lamina (PCDL) can be seen sticking out lateral to the centrum. I assume the “preserved maximum centrum width” is across the stumps of the PCDLs. Which is fine, that’s a useful bit of data to have, but (1) it’s not actually a centrum width, because the PCDL is technically part of the neural arch, and (2) it’s not comparable to any of the reported measurements of BIBE 45854. The closest thing it would be comparable to is the width across the diapophyses, but of course that measurement in SMP VP-1850 is going to be a gross underestimate because the PCDLs are so incomplete. The line-art reconstruction of the missing bits in Fowler and Sullivan (2011: fig 1A1) puts the width of the diapophyses between 85 and 90cm, compared to 98.4cm for the same measurement in the largest vertebra of BIBE 45854.

    The lack of comparability of the diapophysis and parapophysis stumps is why I focused on comparing cotyle dimensions, which is also what Fowler and Sullivan (2011) did in the text of their paper.

    So in sum, the “preserved maximum centrum width” of 63cm/70cm when complete is:
    – a width, not a diameter;
    – part of the neural arch, not part of the centrum;
    – not comparable to the cotyle measurements, which is what I and Fowler and Sullivan (2011) and everyone else tend to focus on;
    – does not necessarily indicate a vertebra any larger than BIBE 45854.

  7. Ronald Says:

    Thank you for your comprehensive answer. I checked the figure in the paper and indeed when the centrum is compared with the scale bar, it is nowhere near 63 cm diam.
    Question: to what extent was BIBE 45854 full-grown? Is it at all possible to estimate this on the basis of particular fused bones? Or is the unrestored specimen too incomplete for that? I read, for instance, that the AMNH Patagotitan was estimated at only 70-80% of full-grown (based on sacrum fusion?).

  8. Matt Wedel Says:

    Question: to what extent was BIBE 45854 full-grown? Is it at all possible to estimate this on the basis of particular fused bones?

    Ugh, that is an excellent question. I don’t know that it’s answerable. I’ve seen a fair number of authors write stuff like, “The specimen was probably close to fully grown, based on the complete fusion of the neural arches”, but that’s not necessarily true, I can think of loads of specimens that have fully or partially fused neural arches that are nowhere near fully grown. That needs to be a post of its own, or possibly a paper (or both).

    Vertebrae are tough, you can’t just section them and count the growth rings like you can with limb bones and ribs, because internal pneumatization will have destroyed all but the most recent growth lines, and external pneumatization may have remodeled away or otherwise modified at least some of the last growth lines. Even in unpneumatized vertebrae, the internal structure is mostly trabecular bone and marrow spaces, so probably no growth lines will be preserved. I actually have a plan to check on this in a project that will be launching later this year, so watch this space.

    I read, for instance, that the AMNH Patagotitan was estimated at only 70-80% of full-grown (based on sacrum fusion?).

    Oh, I hadn’t heard that. I’d assume based on limb bone histology, because sacral fusion is so variable that it’s hard to derive any hard-and-fast rules, even between individuals in the same population.

    But even if it’s based on limb bone histo, I’m not sure how we could possibly know how much growth was left, unless the growing bone could be fitted into a fairly complete, known growth curve, which I strongly suspect is not the case for Patagotitan.

  9. Ronald Says:

    Encouraged by your kind reply: I found that the ‘only 70% grown Patagotitan’ suggestion comes from a comment on your own SVPOW (!), here:
    https://svpow.com/2019/06/16/supersaurus-ultrasaurus-and-dystylosaurus-in-2019-part-2b-the-size-of-the-byu-9024-animal/

    From Illiterate Scholar.

    And then Mike Taylor makes some interesting comments with 6x fused or fusion in it.

    Would indeed be a very interesting study!

    As for the Alamosaurus centrum, I admit there was/is some wishful thinking on my part, regarding my favorite dinosaur. I would just like it to be in the select Argentinosaurus super-league. Of course there is still the Mexican tibia/fibula…

  10. Mike Taylor Says:

    I can think of loads of specimens that have fully or partially fused neural arches that are nowhere near fully grown. That needs to be a post of its own, or possibly a paper (or both).

    Isn’t it already?

  11. Matt Wedel Says:

    You keep doing that. The answer this time is also ‘no’, because there’s more data out there.


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