Resizing Amphicoelias
11:43 pm
Last summer, a comment about the size of the newly-described South American sauropod Puertasaurus led me to investigate the size of Amphicoelias fragillimus, the name E. D. Cope gave to part of one gigantic sauropod vertebra found in Colorado in the 1870s. In a comment to that post, Jerry Harris dropped the hint that more information on A. fragillimus was in the works, and now at least part of what he alluded to has come to pass. A new paper by Ken Carpenter of the Denver Museum of Nature and Science reviews what is known of A. fragillimus, provides a revised size estimate, and discusses why so many sauropods got so darned big.
This paper has inspired a couple of very good posts on Darren Naish’s Tetrapod Zoology blog, and I’ll refer the reader here and here for his excellent summary of the history and validity of A. fragillimus. I’ll focus on the new size estimates, and why A. fragillimus was even larger than I had imagined.
My initial estimate of the size of A. fragillimus was made by comparing Cope’s reconstruction of the type vertebra to the vertebrae of local giant Seismosaurus hallorum (properly Diplodocus hallorum at this point, but more on that later). Scaling up a Seismosaurus to fit Cope’s estimate of a 6 to 7 foot tall A. fragillimus vertebrae results in an animal about 50 meters (160 feet) long.
As it turns out, Cope may have significantly underestimated the height of the vertebra of A. fragillimus. Carpenter compared Cope’s drawing of the Amphicoelias fragillimus specimen with material known from another, more reasonably-sized species of Amphicoelias, A. altus. Scaling an A. altus dorsal to fit the A. fragillimus material results in a whopping 2.7 meter (8.8 foot) tall bone!
From left to right:
- The diplodocid Seismosaurus hallorum dorsal 8 (after Herne and Lucas 2006),
- The diplodocid Amphicoelias fragillimus dorsal 9/10? as reconstructed by Cope 1878,
- The diplodocid Amphicoelias fragillimus dorsal 9/10? as reconstructed by Carpenter 2006, scaled from
- The diplodocid Amphicoelias altus dorsal 10? (after Carpenter 2006, modified from Osborn and Mook 1921),
- The titanosaur Puertasaurus reuili dorsal 2 after Novas et al 2005, Figure 2). Scale bar equals 1 meter.
Carpenter scaled up a Diplodocus to fit this new super-sized vertebra, and his Amphicoelias fragillimus measures a full 58 meters (190 feet) from snout to tail. The estimated mass of this mega-sauropod would be about 122,400 kg (about 270,00 lbs or 135 tons).
Here is the size comparison I made last summer, comparing the big diplodocids Seismosaurus hallorum (33 meters) and Amphicoelias fragillimus (my 50-meter estimate) to some of the largest titanosaurs, Argentinosaurus huinculensis (at 37.5 meters, the length of the skeletal reconstruction on display at the Fernbank Museum) and Puertasaurus reuili (at 40 meters, the upper estimate reported in the media). Click on the image for a larger version:
In Figure 3 of his paper, Carpenter shows a more detailed size comparison of mega- and super-sauropods (mega-sauropods are defined as those that reach or exceed 30 meters in length)—a copy of it is posted here. In addition to an enormous Amphicoelias, it shows Seismosaurus (C) and a silhouette of Argentinosaurus (F) based on the profile of the related titanosaur Saltasaurus. This new titanosaur shape changes their dimensions considerably, shrinking Argentinosaurus from 37.5 down to 30 meters in length.
Based on this information, I resized and revised and came up with the following size comparison (click for a larger version):
From left to right:
- The diplodocid Seismosaurus hallorum (skeleton on display at the NMMNHS–33 m. (110 ft.) long),
- The diplodocid Amphicoelias fragillimus (est 58 m. (190 ft.) long),
- Homo sapiens (1.8 m. (6 ft.) tall),
- African Elephant Loxodonta africana (4 m. (13 ft.) tall at the shoulder),
- The titanosaur Argentinosaurus huinculensis (est 30 m. (98 ft.) long),
- The titanosaur Puertasaurus reuili (shortest reported estimate 35 m. (115 ft.) long).
Note that, in this latest estimate, Seismosaurus completely fits under the tail of Amphicoelias fragillimus!
Further Reading:
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: pp. 131–137. PDF.
Cope, E. D. 1878. A new species of Amphicoelias. American Naturalist 12(8): pp. 563–564. JPG. HTML.
Herne, M. C. and Lucas, S. G. 2006. Seismosaurus hallorum: osteological reconstruction from the holotype. New Mexico Museum of Natural History and Science Bulletin 36: pp. 139–148.
Novas, F. E., Salgado, L., Calvo, J., and Agnolin, F. 2005. Giant titanosaur (Dinosauria, Sauropoda) from the Late Cretaceous of Patagonia. Rev. Mus. Argentino Cienc. Nat., 7(1): pp. 37–41. PDF.
Don’t forget the two posts at Tetrapod Zoology, and Matt Wedel (a.k.a. Doctor Vector) promises to weigh in on the topic, so you know that’s worth keeping an eye out for.
That’s insane. Questions immediately pop into my head. How fast did it grow? How could it have possibly been endothermic at that size? How could it even stand, given its significant tonnage?
_Fifty-eight meters long_?
That’s one honkin’ HUGE animal!
And there’s no reason to think the vertebra that Cope found was from a maximum-size individual. Others of the species might have gotten even larger. So much for the blue whale as “the largest animal that ever lived on Earth.”
One other line jumped out at me from the abstract of Carpenter’s paper. Carpenter wrote: “One possible cause for large body size in sauropods, based on studies of extant mammalian megaherbivores, may be due to increased gut size for more efficient digestion of low quality browse by hindgut fermentation.”
Later in the paper he says that diplodocids achieved larger gut size by simply enlarging the entire body, leading to the monstrous sizes achieved by “Seismosaurus” and _Amphicoelias fragillimus_. Doesn’t this imply that these dinosaurs gained at least enough additional nutrition from the increased gut capacity to feed their increased mass? _A. fragillimus_ is double the length of _Diplodocus carnegei_, which implies eight times the mass, which in turn implies eight times the need for feed. Does this make sense in light of the known or calculated values of the nutritive value for Late Jurassic plants?
Yup…the paper in the new NMMNH&S Bulletin was most of what I was talking about last year…one last little tidbit will show up at SVP in 2008 (yes, 08), and that will make all the drawings pale in comparison!
As for how A. fragillimus could get enough food with a gigantic stomach, the answer lies in a relationship between gut size and nutrition extraction from plant matter. Basically, the longer the food sits there, the more it is broken down and the more nutrients are extracted from it, and the larger the stomach, the longer the food sits there. Thus, sauropods seem to have been able to get more from less food than most herbivores may have. This, and other related aspects of sauropod paleobiology, were also covered recently in:
Engelmann, G.F., Chure, D.J., and Fiorillo, A.R. 2004. The implications of a dry climate for the paleoecology of the fauna of the Upper Jurassic Morrison Formation; pp. 297-308 in Turner, C.E., Peterson, F., and Dunagan, S.P. (eds.), Reconstruction of the Extinct Ecosystem of the Upper Jurassic Morrison Formation. Sedimentary Geology 167.
Amazing! I wonder how much it ate? How fast it lost heat? My nephew would probably ask how much gas it produced!
Sorry to double post, but would you mind if I put this image on my blog with a link back to yours?
I have serious doubts as to the size estimate, given that we don’t really know, and never will know, barring a complete specimen (highly unlikely to ever occur given the enormity of the animal even at minimum, the area of ground needed to be intact to preserve it, and the fact that fully articulated skeletons are almost non-existent in the fossil record)…the SHAPE, in life, of the animal. It could’ve had a highly tapered tail, neck, or both- which could make it yards and yards shorter than estimated.
Given the size of the known specimens, however, I’d caution a guess that it would likely have at least rivaled the blue whale in weight and certainly length would have likely been in excess of 120 feet in larger individuals.
Not that we should rule out a 190 foot animal- not too long ago, the top minds in science thought it IMPOSSIBLE for an animal the size of apatosaurus to support it’s (comparatively tiny) bulk without the aid of water, and couldn’t FATHOM and animal the size of argentinosaurus and the like. Yet they’re known to have existed, walked on land, held their tails above the ground, and even traveled together.
This is not the largest dinosaur! Argentinoasurus is, it weighed about 90 to 115 tons, but the blue whale can weigh 209 tons.
Oops, I went to say Argentinosaurus.