Biggest sauropod ever (part.... II)

By popular demand... it's the second part of the old, old, old (ver 1) article I wrote in 2006 on the obscure and poorly known mega-sauropod Amphicoelias fragillimus. Be sure to read part I first.

So, A. fragillimus was described in 1878 on the basis of an incomplete but enormous dorsal vertebra and the distal end of a femur [both reconstructed in the image below]. The details of these bones show that A. fragillimus was a diplodocoid, and thus related to more familiar taxa like Diplodocus and Apatosaurus. Despite its absurd size - suggesting (by comparison with other diplodocoids) a total length of 60 m - this material somehow vanished prior to 1921. Due in part to these facts (and also, perhaps, to its poorly publicised and unfamiliar-sounding - or 'crappy' - name), Amphicoelias fragillimus was to be all but forgotten in the decades that followed...

During the 1990s, little-known articles by John McIntosh (revered older statesman of sauropod research) and Greg Paul looked briefly at A. fragillimus. McIntosh (1998) went through Cope's inventories of the Garden Park discoveries (these records had been missed by Henry Osborn and Charles Mook in their 1921 review of Cope's sauropod collection) and found that, perhaps because the contents of several crates have no surviving records, the shipment of A. fragillimus to New York wasn't recorded. Paul (1994a, b) estimated the size of A. fragillimus based on the dimensions provided by Cope, suggesting (again, based on comparison with more completely known diplodocoids) a total length of 40-60 m, a weight of 100-150 tons, and that it would have been 9 m tall at the hips, and with thighs 3.8 m long [image below from here on Ultrazionale].

The news is that, at long last, a proper reappraisal of this mysterious giant has finally appeared [UPDATE: remember that the text you're reading was written and first published in 2006]: it's a new paper by Ken Carpenter of the Denver Museum of Nature and Science, and while, sadly, it doesn't report the discovery of a new, articulated A. fragillimus specimen, it does cover pretty much everything we know about this dinosaur (Carpenter 2006). By the way, Carpenter and colleagues have tried looking for additional remains of A. fragillimus, thus far without success. Actually, I have to note here the rumour that new A. fragillimus material has been discovered, and that it will be discussed at the 2008 Society of Vertebrate Paleontology meeting [UPDATE: here we are, two years later... and, needless to say, this never happened].

Was A. fragillimus a hoax?

Unsurprisingly, quite a few people have been sceptical about the existence of this all-too-conveniently lost mega-sauropod. Can we be sure that it ever really existed, or could it be that Cope was pulling a fast one in order to beat his rival, Othniel Charles Marsh [shown here], hands-down in an effort to describe the biggest sauropod? As attractive as this scenario might appear, hoaxing is highly, highly unlikely. Consider the following:-

-- Cope was very specific about all the discovery details of A. fragillimus. According to his field notes, it was collected in late 1877 by Oramel Lucas (described by Cope as his 'indefatigable friend') at Garden Park, specifically from quarry III, a site southwest of the hill known today as Cope's Nipple (Carpenter 2006). The rocks here yielded several other particularly large Morrison Formation dinosaurs (such as Camarasaurus supremus).

-- Furthermore, the shipment records discovered by McIntosh show that Oramel Lucas and his brother Ira knew of A. fragillimus and labelled some remains with this name (McIntosh 1998, p. 487 and p. 498). If it was a hoax, then the Lucas brothers must have been in on it too, which now makes it a conspiracy.

-- The conspiracy would have to extend even further, as an American Museum of Natural History catalogue number, AMNH 5777, was reserved for the A. fragillimus material.

-- The rivalry that existed between Cope and Marsh is also relevant here. As is well known, Marsh enjoyed making a very public fool of Cope when he made a technical error (Storrs 1994, Davidson 2002), and when he disagreed with Cope, or thought him wrong, Marsh was tediously pedantic in his criticisms (see Marsh's 1873 papers on dinoceratans, for example). Marsh never criticised, nor even questioned, the reality of A. fragillimus. Carpenter (2006) notes that 'Marsh is known to have employed spies to keep tabs on what Cope was collecting, and it is quite possible that he had independent confirmation for the immense size of A. fragillimus' (p. 134).

-- Cope's drawing of A. fragillimus is accurate-looking and elaborate, and his description refers to small detailed features, all of which conform in details with what we know of diplodocoid vertebrae (part of the description is reproduced at left: from here). He would have to have made all of this stuff up if the specimen was a hoax: it's not as if the only record of A. fragillimus is a scribbled fragment in a diary, saying 'On Tuesday I saw the biggest vertebra ever... it was thiiiiis big...'. Rather, the material is documented, in detail, in a proper technical paper. To hoax an entire paper of this sort would be severe science-crime, and there is no indication that Cope was unscrupulous or dastardly, or prepared to stoop this low.

-- It is noteworthy that workers well known for their methodical and conservative approach to sauropod studies (notably John McIntosh) have accepted Cope at his word. Osborn, who succeeded Cope as vertebrate palaeontologist for the US Geological Survey and is well known for speaking his mind when he had a problem with something, also never voiced doubts about A. fragillimus.

All of this is circumstantial, for sure, but I agree with Carpenter (and others) that the idea of Cope perpetrating a hoax of this magnitude is pretty much unthinkable. I think we have to assume that the specimens really existed. Therefore, they must have become lost or destroyed some time between 1878 (their discovery date) and 1921 (when Osborn and Mook failed to find them). As Carpenter (2006) points out, it in fact appears likely that the material was too fragile to survive, and that it crumbled to bits some time after its discovery. Matt Celeskey also noted this possibility. Cope commented on this fragility, writing 'in the extreme tenuity of all its parts, this vertebra exceeds this type of those already described, so that much care was requisite to secure its preservation' (p. 563), and his drawing also suggests that the vertebra had been subjected to extensive weathering and hence was already fragile. Indeed its fragile nature explains the specific name he chose for it.

Furthermore, 'preservatives had not yet been employed to harden fossil bones, the first of which was a sodium silicate solution used in O. C. Marsh's preparation lab at Yale University beginning in the early 1880s' (Carpenter 2006, p. 134). Support for the hypothesis that the material simply did not survive collection and storage comes from the fact that, within recent years, a Camarasaurus supremus vertebra collected from the same area is known to have crumbled into small useless fragments.

The other Amphicoelias

As I've now mentioned a few times, the detailed anatomy of the A. fragillimus vertebra (as figured by Cope) shows us that this sauropod was a diplodocoid. We can make a confident statement like this because it is relatively easy to distinguish the different sauropod clades on the basis of their vertebral anatomy, and A. fragillimus has all the distinctive anatomical features typical of diplodocoids. In fact it strongly resembles the vertebrae of the first named species of Amphicoelias, A. altus, which Cope described in February 1878.

A. altus is poorly known, but not as poorly known as A. fragillimus: it was first described for vertebrae, a pubic bone and a femur (Cope 1878), but a scapula, coracoid, ulna and partial skull were later referred to it. Based on these remains, it seems that A. altus was similar in size to Diplodocus carnegii and probably around 25 m long (Paul 1994a, b). It's particularly interesting in that its femora were markedly elongate and slender. Some workers have regarded A. altus as particularly close to Diplodocus, in which case it would be a diplodocid diplodocoid, and probably a diplodocine diplodocid diplodocoid. However, it has also been asserted that A. altus was a basal diplodocoid, and thus more archaic than diplodocids and other flagellicaudatan diplodocoids [adjacent image shows Diplodocus mount at Denver Museum of Nature and Science].

Was Cope right in referring his second Amphicoelias species to the same genus as the first? Several authors have thought so, and in fact have gone so far as to state that 'it is doubtful ... if the characters described by Cope warrant the placing of the type [of A. fragillimus] in another species different from A. altus' (Osborn & Mook 1921, p. 279), or 'there is no reason not to consider [A. fragillimus] a very large individual of A. altus' (McIntosh 1998, p. 502). If this is true then, like A. altus, it's reasonable to assume that A. fragillimus was also superficially Diplodocus-like, and with particularly elongate, slender femora (a shocking idea given the animal's size).

Carpenter argued in his 2006 paper that, in fact, A. fragillimus seems to have differed from A. altus in a number of anatomical details, and that the two might not have been congeneric after all. As he noted, this remains untestable in the absence of better remains however. Let's all hope and pray that a new generic name is up for grabs, and I don't want any 'superlative + saurus' nominations.

One final thing. What's with the image at the top of the page? I discovered it while googling Amphicoelias. Huh, in my day the only decent zoid was Hellrunner. The image at left is mostly irrelevant: that's Matt Wedel, and he is indeed posing with a diplodocoid vertebra... although it's not from an Amphicoelias.

For previous Tet Zoo posts on sauropods see...

• Gigantoraptor, Eocursor and... baby Toni
• The world's most amazing sauropod
• The horror that is LOLSAUROPODS
• The hands of sauropods: horseshoes, spiky columns, stumps and banana shapes
• Junk in the trunk: why sauropod dinosaurs did not possess trunks
• Sauropod dinosaurs held their necks in high, raised postures
• Thunder-Lizards: the Sauropodomorph Dinosaurs (a book review)
• Biggest.... sauropod.... ever (part.... I)
• Bonadonna's Diplodocus

And - if you're serious about sauropods - you really should be spending more time at SV-POW!

Refs - -

Carpenter, K. 2006. Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. New Mexico Museum of Natural History and Science, Bulletin 36, 131-137.

Cope, E. D. 1878. On the saurians recently discovered in the Dakota Beds of Colorado. The American Naturalist 12 (2), 71-85.

Davidson, J. P. 2002. Bonehead mistakes: the backround in scientific literature and illustrations for Edward Drinker Cope's first restoration of Elasmosaurus platyurus. Proceedings of the Academy of Natural Sciences of Philadelphia 152, 215-240.

McIntosh, J. S. 1998. New information about the Cope collection of sauropods from Garden Park, Colorado. Modern Geology 23, 481-506.

Osborn, H. F. & Mook, C. C. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3, 247-287.

Paul, G. S. 1994a. Big sauropods - really, really big sauropods. The Dinosaur Report Fall 1994, 12-13.

- . 1994b. Is Garden Park home to the world's largest known land animal? Tracks in Time 4 (5), 1.

Storrs, G. W. 1984. Elasmosaurus platyurus and a page from the Cope-Marsh war. Discovery 17 (2), 25-27.