Category Archives: anatomy

Real or cast? If only it were that simple!

Norman Boss Brachyceratops courtesy Smithsonian archives

Norman Boss assembles  a “Brachyceratops” mount. White bones and portions thereof are sculpted. Image courtesy of the Smithsonian Institution Archives.

Back in January, London’s Natural History Museum incited a flurry of debate when it announced that Dippy, the Diplodocus skeleton that has graced the museum’s entrance hall for decades, will soon be retired and replaced with a blue whale. One of the recurring arguments in favor of the change has been that Dippy is not an original specimen – it’s a cast, or as some commentators have called it, “a fake.” As I argued last month, referring to a fossil cast in this way is a flagrant misrepresentation. An excellent post by Liz Martin covers this in more detail – “fake” implies deception, or something invented outright. Fossil casts are nothing of the sort. They are exact replicas of fossils, and they could not exist without the original specimens they are based on.

Nevertheless, the idea that fossil mounts are either original bones or casts is a bit of a false dichotomy. I’m as guilty as anyone of propagating this myth – it’s a simple way to assuage the fears of museum visitors that the fossil skeletons on display aren’t real. The truth is that most mounts include some amount of straight-up sculpted material. After all, the fossilized remains of vertebrate animals, particularly large ones, are almost never found articulated or anywhere near complete. The specimens chosen for museum mounts are among the absolute best available, but even they are not perfect. For instance, the NHM Dippy (actually one of many) is mostly a cast of a single Diplodocus specimen held at the Carnegie Museum of Natural History, but the forelimbs were reconstructed. When the mount was assembled, no Diplodocus forelimb material of comparable size was available, so Arthur Coggeshall and colleagues sculpted some based on smaller specimens.

Sculpted feet

The sculpted feet of the AMNH Tyrannosaurus. Photo by the author.

From Hadrosaurus, the first mounted dinosaur skeleton, to modern reconstructions like Anzu, fossil mounts as we know them would not be possible without some amount of informed reconstruction. Take the iconic Tyrannosaurus rex mount at the American Museum of Natural History, assembled in 1915. The skeleton is a composite of two T. rex specimens, neither of which included any of the bones of the feet. Rather than creating a skeleton that stopped short at the ankles, Adam Herman sculpted a set of feet based on Allosaurus, another large meat-eating dinosaur. When Tyrannosaurus feet were eventually discovered, the allosaur-inspired feet turned out to be a little too bulky – tyrannosaurs actually had relatively long, gracile toes. But it’s not like T. rex turned out to have hooves or wheels. In most respects, from the basic three-toed arrangement to the shape and position of each individual bone, Hermann’s hypothesized tyrannosaur feet were spot-on. In fact, they were so close that the museum didn’t bother updating them when the skeleton was remounted in 1995.

The sculpted portions of fossil mounts aren’t wild speculation. They are very reasonable hypotheses based on a solid understanding of skeletal anatomy. As anatomist Georges Cuvier wrote in 1798:

Today comparative anatomy has reached such a point of perfection that, after inspecting a single bone, one can often determine the class, and sometimes even the genus of the animal to which it belonged…this is because the number, direction, and shape of the bones that compose each part of an animal’s body are always in a necessary relation to all the other parts, in such a way that – up to a point – one can infer the whole from any one of them and vice versa.

Cuvier’s principle of the correlation of parts – the idea that all backboned animals are built on the same basic body plan – is fundamental to the science of paleontology. If we have the right forelimb of an animal, we know that it had a mirror-image left forelimb. If we find a skeleton with it’s skull missing, we can still be confident that it had a head. What’s more, specialists can often recognize the group an animal belongs to (and sometimes the species) from just a few bones or teeth. Salamander vertebrae have a characteristic hourglass shape. Frog limb bones have “double-barreled” cavities in cross section. Marsupial teeth have a stylar shelf. New world monkeys have an extra premolar in each quadrant of the mouth. With enough specialized knowledge of related taxa, it is entirely possible to produce an educated reconstruction of most any animal from a minority of its skeleton.

How much is too much?

Argentinosaurus and Giganotosaurus at the Fernbank Museum of Natural History. Source

But as far as mounted skeletons in museums go, how far can we take this? Is it reasonable to build a standing mount when only 50% of the skeleton is definitively known? What about 30%? 10%? By bone count, that’s about the percentage of fossils ever found from the sauropod Argentinosaurus. And yet, the Fernbank Museum in Atlanta has a (rather spectacular) Argentinosaurus mount in its lobby. The whole thing is, of course, a fiberglass sculpture, dutifully based on better-known relatives. This mount is probably a fair reconstruction of what a complete Argentinosaurus skeleton would look like (although see this list of inaccuracies at Paleoking), but some still might consider it misleading. Your mileage may vary.

Museums generally do a good job labeling reconstructions. In particular, The Carnegie Museum and the Royal Ontario Museum are to be commended for posting charts alongside mounted skeletons that show which bones are original, which are casts, and which are reconstructions. In other cases, a little more transparency would not be unwelcome. For example, the four skulls below appear to include at least as much plaster reconstruction as bone, but they are all labeled as original specimens.

Photos by the author.

Four heavily-reconstructed fossil skulls at AMNH. Clockwise from top: Eryops, Indricotherium, Ophiacodon, and Triceratops. Photos by the author.

This is ultimately more of a philosophical question than a scientific one. Museum mounts, regardless of the amount of sculpted material, are usually well-supported reconstructions of the animal in question. If new information shows that a mount is wrong – as sometimes happens – staff are undoubtedly aware and will correct it as soon as funding and bureaucracy allow (granted, that can take decades). But as I’ve argued before, fossil mounts are unique among museum exhibits in that they are both the specimens and the interpretive context. They are hypotheses, but are presented (or at least understood) as straightforward truth. With this paradox in mind, how much is a museum ethically obligated to share about a mount’s creation? How can we do this without spurring visitors to use the dreaded f-word?

Comments are open, as always, and I’d be thrilled to hear what readers think.

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Filed under AMNH, anatomy, dinosaurs, fossil mounts, mammals, museums, NHM, reptiles, sauropods, science communication, theropods

Missourium: Hiding in Plain Sight

A while back I wrote about Albert Koch, the 19th century showman who made a tidy profit assembling and touring chimeric composites of fossil bones. Koch’s monsters – an exaggerated mastodon called “Missourium” and two alleged sea serpents made from whale fossils – were a hit with the public but an embarrassment to scientists. At the time, ideas like extinction and the great age of the Earth were very new, and Koch’s fraudulent commodification of fossil evidence made it harder for legitimate researchers to be taken seriously.

The mastodon once called Missourium in the Mammal hall. Source

Is this mastodon at NHM actually the legendary Missourium? Source

One thing I breezed over in the previous post was the eventual fate of Koch’s creations. It is widely reported that the whales (which Koch alternatively called “Hydrargos” and “Hydrarchos”) met rather dramatic ends: one perished in the Great Chicago Fire of 1871, while the other was purchased by the Royal Anatomical Museum in Munich Berlin and was subsequently blown up during World War II. But what about Missourium? Following Simpson, I wrote that the mount was sold to the British Museum (now the Natural History Museum), and left it at that.

However, Mike Taylor recently asked whether Missourium might still be on display in South Kensington today:

I didn’t know that the “Missourium” was sold to the British Museum! Do you know what they did with it? I don’t suppose anyone has the specimen number? Is it possible that they got rid of all the fakery and mounted it in the mammal hall, and that it stands there today under the shadow of the whale?(Link to comment)

After some very modest digging, I found that Mike’s hunch was exactly right. General googling revealed that several authors, including McMillian, Debus, and Fuller, had concluded that the NHM mastodon and Missourium were one and the same, but none of them offered a proper citation. While I have no reason to doubt these authors, I still wanted a primary source. I eventually found that in a 1991 article by NHM preparator William Lindsay, which details the process of moving the mastodon to its current home in the Mammals Gallery, and confirms its identity as a remounted Missourium.

An insane illsutration that accompanied Koch's traveling exhibit.

This insane illustration of Missourium in its natural habitat accompanied Koch’s traveling exhibit.

As far as we know, Koch retrieved all the fossils that made up Missourium from a single Benton County, Missouri spring in 1840 (Hoy confirmed the locality and found several additional bones in 1871). Koch used the bones of at least two individuals to assemble a chimeric super-mastodon, which he displayed in St. Louis. Most notably, Koch spliced a number of extra vertebrae into the spinal column, extending the mount’s length to 32 feet. To appeal to local audiences – and to differentiate his creation from Peale’s mastodon – Koch named the beast Missourium, and proclaimed it to be the skeleton of the biblical Leviathan. In 1841, Koch sold his St. Louis showroom and took Missourium on tour, eventually winding up in the Egyptian Hall of Piccadilly, London.

Local specialists, including Gideon Mantell, were initially impressed by the display. However, attitudes soured in February 1842 when Richard Owen presented a scathing critique of Koch’s work to the Geological Society of London. In his lecture, Owen made some cursory remarks about the inaccurately articulated skeleton, but he was primarily concerned with confirming that Missourium was nothing more than a run-of-the-mill American mastodon. Owen was a trendsetter, then as well as now, and for decades afterward his fellow naturalists took every opportunity to take Koch to task. For example, James Dana allowed that “the credit is due him of having performed a great service to science by his collections”, but tore into Koch’s publications to prove that he “was quite ignorant of geology and without scientific training.”

It is therefore ironic that Owen himself gave Koch one of the biggest paydays of his life when he bought Missourium on behalf of the British Museum. In exchange for the skeleton, Koch made off with a $2000 downpayment (about $65,000 today), plus $1000 a year for the rest of his life. It seems museums have been paying extortion prices for display-caliber fossils for a long time.

Armature

Diagram of the mastodon’s internal armature. Figure 10 of Lindsay 1991.

Museum technicians, including an individual named J. Flower, disassembled Missourium and rebuilt it into a proper mastodon. Reduced to a length of 20 feet, the remounted skeleton (now OR15913) was placed in the historic fossil mammals exhibit and remained there for almost 150 years. In 1991, the mastodon was selected for inclusion in the new Mammals Gallery at NHM, which combines both fossil and modern specimens. Although William Lindsay and colleagues had only limited time to restore and move the skeleton, they gained fascinating insight into 19th century mounting practices. As shown above, the internal metal armature was virtually identical to 20th century counterparts. A hand-wrought iron beam threaded through each vertebra provided the mount’s central anchor point. Four additional iron bars skewered the appendicular elements and connected to the vertebral beam inside the pelvis and under the shoulder girdle. An enlarged foramen magnum allowed the vertebral beam to enter the back of the skull, which turned out to be composed almost entirely of papier-mâché. A real palate and set of upper teeth were buried in the paper cranium, supported by a cradle of wood and copper wire. Amazingly, an 1881 issue of The Weekly Dispatch used in a cursory repair to the skull was still legible.

historic photo of mastodon

Missourium remounted as a standard mastodon in the historic fossil mammals hall. Source

As to be expected from anything on display for a century and a half, the mastodon was in rough shape. As usual, vibration damage was the primary culprit, and Lindsay discovered that the spongy bone in the femur and cervical vertebrae had been crushed beneath the weight of the iron armature. Although NHM staff weren’t able to completely disarticulate the skeleton, they separated it into seven pieces for transport. A coating of polyvinyl acetate was applied to consolidate the fragile fossils, and larger cracks were filled in with putty. Meanwhile, the deteriorating replica skull was retired and replaced with a glass-reinforced plastic cast. The original tusks are still included in the display, however, which is unusual among proboscidian mounts.

Missourium was the third mounted fossil skeleton ever assembled, after Bru’s Megatherium and Peale’s mastodon. Although they’ve each been reconfigured and restored at various points in time, all three specimens are still on exhibit today. While any object that has been on public display for 150 years (or more) is fascinating, I find it especially compelling that so few fossil mounts have ever been taken off exhibit. Public demand, institutional inertia, and the challenges of safely disarticulating a historic mount all contribute to the incredible longevity of these displays, but time inevitably takes its toll on fragile fossils. I can’t help but wonder how many more generations of visitors will be able to view the mastodon that was once Missourium before a mounted display becomes untenable.

References

British Museum (1904). The History of the Collections Contained in the Natural History Departments of the British Museum. London, UK: British Museum (Natural History) and Longmans and Co.

Dana, J.D. (1875). On Dr. Koch’s Evidence with regard to the Contemporaneity of Man and the Mastodon in Missouri. The American Journal of Science and Arts 9:335-346.

Hoy, P.R. (1871). Dr. Koch’s Missourium. The American Naturalist 5:3:147-148.

Lindsay, W. (1991). “Mammoth” Task. Curator 34:4:261-272.

Owen, R. (1842). Report on the Missourium now exhibiting at the Egyptian Hall, with an inquiry into the claims of the Tetracaudodon to generic distinction. Proceedings of the Geologic Society of London 3:3:82.

Simpson, G.G. (1942). The Beginnings of Vertebrate Paleontology in North America. Proceedings of the American Philosophical Society. 86:1:130-188.

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Filed under anatomy, fossil mounts, history of science, mammals, museums, NHM

Museums and the Triceratops Posture Problem – Part 2

Triceratops at the National Museum of Natural History.

Triceratops “Hatcher” at the National Museum of Natural History. Photo by the author.

Back in July, I wrote about how the forelimb posture of ceratopsian dinosaurs like Triceratops has puzzled paleontologists for more than a century. Most quadrupedal dinosaurs held their front legs straight under their bodies, and it would make sense if Triceratops and its kin did the same. However, when researchers attempted to physically articulate skeletons for museum displays, they found that that the humerus would only fit properly with the scapula if it projected horizontally from the torso – like the sprawling limbs of a lizard. Over the years, new specimens, new research methods, and new technologies have all been used to help resolve this conundrum, but a consensus has not yet been reached. Of particular interest to me is the unusually central role mounted skeletons in museums have played in this biomechanical mystery. The previous post covered the historic Triceratops mounts; this entry will take a look at some more recent Triceratops displays in American museums.

The Hatcher Project

In 1998, a visitor looking at the Triceratops mount at the National Museum of Natural History happened to sneeze. To her alarm, the sneeze was enough to knock a small fragment of bone off the pelvis and onto the floor. The visitor thoughtfully informed security, and after a thorough conservation assessment by Kathy Hawks, it was determined that the 93-year-old mount needed to come off exhibit, and soon. The delicate fossils had served valiantly through 23 presidential administrations, but now it was time for the skeleton to be disassembled and preserved for posterity.

Retiring the classic Triceratops gave Ralph Chapman, head of the Museum’s Applied Morphometrics Laboratory, an opportunity to take on a project he had been germinating for some time. Chapman wanted to demonstrate the potential of 3-D scanning technology for paleontology research by creating a high-resolution digital duplicate of a dinosaur skeleton. Today, the process of making and studying digital copies of fossils is both widespread  and remarkably straightforward, but in the late 1990s it was practically science fiction. Nevertheless, the historic Triceratops was an ideal digitization candidate for several reasons. First, the digital assets would reduce handling of the delicate and aging original fossils. Second, exact copies of the scanned bones could be made from milled foam and plastics to create a replacement exhibit mount. Finally, a digital Triceratops would be a great opportunity to revisit the ceratopsid posture problem in a new way.

digital hatcher

A rendering of the digital Hatcher. Source

The ensuing Hatcher Project (the Triceratops was named in honor of John Bell Hatcher, who found the original fossils in the late 19th century) was a collaboration between Museum staff and several industry experts, including Lisa Federici of Scansite 3-D Services and Arthur Andersen of Virtual Surfaces, Inc. The first step was to place stickers on 100 key points on the Triceratops. These points were recorded with a surface scanner, so that the historic mount could be digitally recreated in its original pose. After that, fossil preparators Steve Jabo and Pete Kroehler carefully dismantled the skeleton. Each bone from the skeleton’s right side* was then scanned individually, producing 20 gigabytes of data (you’re supposed to gasp…again, this was the late 90s).

*Bones from the right side were mirrored to reproduce the left half of the skeleton. 

Since the original mount had been a somewhat disproportionate composite, the team made a few changes when building the new digital Hatcher. Some elements, including the undersized skull, were enlarged to match the rest of the skeleton. In addition, parts that had either been sculpted or were not actually Triceratops bones – such as the dorsal vertebrae and the hindfeet – were replaced with casts acquired from other museums. The result was the world’s first complete digital dinosaur, and shortly afterward, the first full-sized replica skeleton generated from digital assets.

Updated "Hatcher" mount's rarely seen right side. Source

Hatcher’s seldom seen right side was briefly exposed recently, before the mount was moved to a temporary second floor location. Source

In April 2000, the Hatcher team convened at NMNH to determine how the new replica mount would be posed. Chapman, Jabo, and Kroehler were joined by Kent Stevens of the University of Oregon, Brenda Chinnery of Johns Hopkins University, and Rolf Johnson of the Milwaukee Public Museum (among others) to spend a day working with a 1/6th scale model produced by stereolithography specialist Jason Dickman. The miniature Hatcher allowed the researchers to physically test the skeleton’s range of motion without the difficulty of manipulating heavy fossils.

The day was full of surprises. The team was impressed by the wide range of motion afforded by the ball and socket joint connecting the Triceratops skull to the atlas. They also found that the elbow joints could lock, which may have been helpful for shock absorption when the animal smashed things with its face. Nevertheless, when it came time to articulate the humerus and scapula, the team essentially validated Charles Gilmore’s original conclusion that sprawling forelimbs worked best (although the new Hatcher mount stands a little straighter than the historic version, and a lot straighter than the New York Triceratops). While other paleontologists had used indirect evidence (like evenly spaced trackways and wide nasal cavities for sucking down lots of oxygen) to support the idea that Triceratops was a straight-legged, fast-moving rhino analogue, articulating the actual bones showed once again that ceratopsid forelimbs had to sprawl.

Houston and Los Angeles Mounts

LACM Triceratops mount. Photo by Heinrich Mallison, many more here.

LACM Triceratops mount. Photo by Heinrich Mallison, many more here.

Hatcher is the Triceratops I am best acquainted with, and I can’t help but think of it as the definitive example of this animal. However, two new Triceratops mounts demonstrate a radically different take on ceratopsid posture. In 2011, the Natural History Museum of Los Angeles County completed a thoroughly renovated dinosaur hall, which features a brand-new Triceratops mount at its entrance. Like Hatcher, this skeleton is a composite of several specimens, in this case excavated in Montana by LACM teams between 2002 and 2004. Phil Fraley Productions, the exhibit fabrication company behind Sue and the Carnegie Museum dinosaurs, was responsible for mounting the fossils. The primary specimen (LACM 141459, which provided the skull and right forelimb) is notable because it included a completely intact and articulated front leg. Although the analysis of this important find has yet to be published, exhibit curator Luis Chiappe tellingly chose an erect, rather than sprawling, forelimb posture.

Meanwhile, the Houston Museum of Nature and Science opened its colossal, 30,000 square foot Hall of Paleontology in 2012. Among the dozens of mounted skeletons on display is Lane, reportedly the most complete Triceratops ever found. The museum purchased the skeleton from the Black Hills Institute, and the company also constructed the display mount. Robert Bakker, who curates the Hall of Paleontology, specifically requested that Lane be given a straight-legged, trotting pose. With two legs off the ground, this display emanates strength and speed.

"Lane" at Houston Museum

“Lane” at Houston Museum of Nature and Science. Source

So how did the Los Angeles and Houston exhibit teams manage to construct plausible-looking, straight-legged Triceratops mounts? Since full descriptions of either specimen have not been published, it’s hard to say for sure. From the look of it, however, the new mounts both have narrower, flatter rib cages (as suggested by Paul and Christiansen), which allows more room for the elbow. Likewise, the shoulder girdles are lower than Hatcher’s, and they seem to have been rotated closer to the front of the chest. Also note that the forelimbs of the Los Angeles and Houston mounts are not completely erect – they are strongly flexed at the elbow, as is typical of many quadrupedal mammals.

These new mounts don’t mean the Triceratops posture problem is resolved, though. The angle of the ribs and the position of the scapula are apparently both touchy subjects, so alternate interpretations are sure to arise in the future. After all, Triceratops forelimb posture isn’t just an esoteric bit of anatomical trivia: it has major implications for the speed and athleticism of an extremely successful keystone herbivore. Understanding the limitations on this animal’s movement and behavior can contribute to our understanding of the ecosystem and environmental pressures in late Cretaceous North America. As such, I am eagerly awaiting the next round in this 100-plus year investigation.

A big thank you to Rebecca Hunt-Foster and Ralph Chapman for sharing their time and expertise while I was writing this post!

References

Chapman, R. Personal communication.

Chapman, R., Andersen, A., Breithaupt, B.H. and Matthews, N.A. 2012. Technology and the Study of Dinosaurs. The Complete Dinosaur, 2nd Edition. Bloomington, IN: Indiana University Press.

Fujiwara, S. and Hutchinson, J.R. 2012. Elbow Joint Adductor Movement Arm as an Indicator of Forelimb Posture in Extinct Quadrupedal Tetrapods. Proceedings of the Royal Society 279: 2561-2570.

Hunt-Foster, R. Personal communication.

Paul, G.S. and Christiansen, P. 2000. Forelimb Posture in Neoceratopsian Dinosaurs: Implications for Gait and Locomotion. Paleobiology 26:3:450-465.

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Filed under anatomy, dinosaurs, fossil mounts, history of science, marginocephalians, museums, NMNH, reptiles

Museums and the Triceratops Posture Problem – Part 1

The Triceratops in the Hall of Extinct Monsters, circa 1911. Photo from NMNH on flickr.

The world’s first Triceratops mount at the United States National Museum, built in 1905. Photo courtesy of the Smithsonian Institution Archives.

We know more about dinosaurs today than previous generations of researchers would have ever thought possible. Who would have guessed that in the 21st century, we would have direct evidence for the color of some species, or a detailed understanding of the life history and ontogeny of others? Modern paleontologists can delve deeper into the biology and ecology of extinct animals than ever before, so it comes as a surprise when a very basic question about dinosaur physiology has gone without a definitive answer for well over a century.

For 125 years, paleontogists have struggled to understand how large ceratopsids like Triceratops held their forelimbs. Usually, someone with a good understanding of anatomy can assemble a tetrapod skeleton without much difficulty. Vertebrates are all built along the same basic body plan, and bones fit together in the same general way. However, the forelimb bones of Triceratops and its relatives are quite perplexing. The head of the humerus, which articulates with the scapula, is off-center and extends backward from the shaft. Meanwhile, the lesser tubercle, a tiny nubbin on a human humerus, is enormous and boxy. Taken together, these two traits make it so that if Triceratops held its arm erect and under its body, like most dinosaurs did, the humerus would either puncture the rib cage or be completely dislocated from the shoulder. The simplest way to solve this is to orient the humerus so that the arms project at right angles from the torso, like the sprawling limbs of a lizard. But this just looks wrong. First, ceratopsid hindlimbs are plainly meant to stand straight up. Sprawling forelimbs make Triceratops look mismatched, like the front end a tortoise sewn was to the back end of a rhino. Second, and perhaps more importantly, a sprawling posture would drastically inhibit speed and maneuverability in what is otherwise a very powerfully-built animal. The posture of Triceratops and its kin would ultimately have had a dramatic impact on the animal’s behavior, lifestyle, and ecological role.

Paleontologists haven’t spent the last century just scratching their heads over this problem. Ceratopsid forelimbs have inspired a considerable amount of research over the years, as scientists continue to develop new methods and new tools to explore the biomechanics of prehistoric animals. New technologies have been developed and refined specifically to help determine how Triceratops and its relatives walked and stood. Nevertheless, my intent with this post is not to thoroughly recount the history of ceratopsid forelimb research (if you’re interested, most of the articles referenced below are freely available online). Instead, I’d like to explore the central role museum displays have played in this debate. An artist drawing a two-dimensional image of Triceratops can fudge the orientation of the limbs (and many have), but the team building a mounted skeleton needs to know exactly how to articulate the bones. The ceratopsid posture question first arose in the process of building a mounted Triceratops skeleton for display, and museum mounts continue to be referenced by researchers looking to “ground truth” their ideas. While museum mounts usually exist primarily for education and display, in the case of the ceratopsid forelimb question these exhibits have long been central to the process of studying fossil evidence and creating knowledge.

Early Reconstructions

Marsh's 1891 restoration of Triceratops.

Marsh’s 1888 restoration of Triceratops.

O.C. Marsh published the first illustrated reconstruction of a Triceratops skeleton in 1888. Marsh was legendary in his attention to detail, and the restoration holds up reasonably well today – better, in fact, than his illustrations of Stegosaurus and “Brontosaurus.” Contemporary scientists had no complaints, even though Marsh had given the Triceratops vertical forelimbs. Other dinosaurs had erect limbs, as does the superficially similar modern rhino, so why shouldn’t Triceratops? Marsh’s reconstruction was brought to three-dimensional life in 1901, when the Smithsonian Institution commissioned a life-sized papier mache replica of a Triceratops skeleton for the Pan-American Exposition in Buffalo. Since the model was hand-sculpted, not casted from original fossils, artist F.A. Lucas had no trouble making Triceratops stand up straight, exactly as portrayed by Marsh. The model appeared again at a Smithsonian exhibit in St. Louis, but was apparently lost or destroyed shortly afterwards. In its place, newly hired United States National Museum preparator Charles Gilmore began work on a mounted Triceratops skeleton composed of original fossils.

St. Louis Expo

Straight-legged Triceratops model at the Pan American Expo in St. Louis. Source

Gilmore’s 1905 Triceratops mount was the first real skeleton of a ceratopsid ever assembled for display (first image). Like virtually all dinosaur mounts of the era, the skeleton was a composite of several specimens and a few sculpted pieces. All the Triceratops fossils at Gilmore’s disposal were collected by John Bell Hatcher in the late 19th century, and inherited by the Smithsonian as part of the Marsh collection. USNM 4842, a partial skeleton consisting mostly of a torso and pelvis, formed the basis for the mount, but at least six other individuals were also incorporated. Gilmore selected the skull because it was more complete and less distorted than the other Triceratops skulls available, but it was also on the small side compared to the body. Likewise, the left humerus was about 40% smaller than the right, and conspicuously three-toed Edmontosaurus hindfeet were used (no Triceratops feet had been found at the time). In the process of building his Triceratops, Gilmore had to make several changes to the idealized Triceratops envisioned by Marsh, most notably the orientation of the forelimbs. Not only was it apparently impossible to articulate the humerus in an upright position, but as Gilmore explained it, “a straightened form of leg would so elevate the anterior portion of the body as to have made it a physical impossibility for the animal to reach the ground with its head.”

The American Museum of Natural History produced their own Triceratops mount in 1923. Like its USNM predecessor, the AMNH Triceratops was a composite of several specimens. AMNH 5033, discovered by Barnum Brown in Montana and consisting of most of the dorsal vertebral column, ribs, and pelvic girdle, made up the largest portion of the mount. The skull was recovered by Charles Sternberg in Wyoming, and many of the appendicular bones were sculpted or cast from Smithsonian specimens. Preparator Charles Lang spent over 263 working days on the project, and much of that time was reportedly spent puzzling over the forelimbs. Lang studied living and preserved specimens of a variety of tetrapods, including rhinos, lizards, crocodiles, and tortoises, trying to find a living analogue for the strangely shaped ceratopsid bones. He ended up articulating the forelimbs so that they were even more widely splayed than Gilmore’s reconstruction, to the point that the back of the Triceratops slopes dramatically forward, and the head is almost dragging along the ground. In an accompanying paper, Henry Osborn asserted that “nothing short of a horizontal humerus and completely everted elbow would permit proper articulation of the facets.” By way of explanation, Osborn offered that this posture might have been helpful in withstanding a frontal impact.

triceratops

American Museum of Natural History Triceratops mount, circa 1959. Photo courtesy of the AMNH Research Library.

Together, the Washington and New York Triceratops mounts, with their mismatched tortoise-in-the-front, rhino-in-the-back posture, would come to define both popular and scientific conceptions of ceratopsids for the better part of a century. Other museums followed Gilmore and Lang’s lead and built sprawling ceratopsids of their own, including Richard Lull’s 1929 Centrosaurus at the Peabody Museum of Natural History and Kenneth Carpenter’s 1986 Chasmosaurus at the Academy of Natural Sciences. Even as recently as 1995, AMNH curators chose not to change a single bone on the historic Triceratops mount while modernizing their exhibit.

Voices of Dissent

Robert Bakker was one of the first to challenge the ceratopsid forelimb orthodoxy. In 1986, Bakker criticized Gilmore and Lull’s museum mounts and resurrected Marsh’s original interpretation of a straight-legged Triceratops. His reasoning was that the ceratopsid glenoid fossa (the concavity on the scapula that holds the head of the humerus) was more like the narrow cup of a horse or rhino than the wide trough of a lizard. Bakker went as far as to suggest that Triceratops and its kin might have been able to run or even gallop. Gregory Paul and others piled on, arguing that earlier researchers had run into trouble articulating Triceratops forelimbs because they had made the ribcage too broad. If the ribs were articulated so that the animal had flat flanks, the elbow apparently wouldn’t get in the way. Additional evidence for an upright stance came from a set of ceratopsid trackways described by Martin Lockley and Adrian Hunt. The trackways showed forefeet in line with the hindfeet, suggesting that front and back legs were not mismatched, after all.

This cast of the AMNH Triceratops at the Field Museum replicates the sprawling posture. Photo by the author.

This cast of the AMNH Triceratops at the Field Museum replicates the sprawling posture of the original. Photo by the author.

However, paleontologists like Peter Dodson were unmoved by these new arguments. Dodson proposed that the trackways had been misinterpreted: since ceratopsids are wider at the hips than at the shoulders, evenly spaced front and back prints should imply that the animal was holding its forelimbs out farther than its hindlimbs. Dodson was concerned that the rhino analogy was being taken too far: Triceratops looked like a rhino, so reasearchers were trying their hardest to make it move and behave like a rhino.

As Kenneth Carpenter explained in a comment last year, dinosaurs can do anything on paper, but physically assembling a skeleton forces you to confront the reality of what the bones can and cannot do. In the last decade, two new Triceratops mounts provided paleontologists the opportunity to re-explore this process, with more complete specimens and modern technology at their disposal. Next time, we’ll take a look at what the new Triceratops displays at the National Museum of Natural History and the Los Angeles County Natural History Museum can tell us about ceratopsid posture and lifestyle.

References

Bakker, R.T. 1986. The Dinosaur Heresies: New Theories Unlocking the Mystery of Dinosaurs and Their Extinction. New York, NY: Citadel Press.

Dodson, P. 1996. The Horned Dinosaurs: A Natural History. Princeton, NJ: Princeton University Press.

Fujiwara, S. 2009. A Reevaluation of the Manus Structure in Triceratops (Ceratopsia: Ceratopsidae). Journal of Vertebrate Paleontology 29:4:1136-1147.

Fujiwara, S. and Hutchinson, J.R. 2012. Elbow Joint Adductor Movement Arm as an Indicator of Forelimb Posture in Extinct Quadrupedal Tetrapods. Proceedings of the Royal Society 279: 2561-2570.

Gilmore C.W. 1905.The Mounted Skeleton of Triceratops prorsus. Proceedings of the U.S. National Museum 29:1426:433-435.

Makovicky, P. 2012. Marginocephalia. The Complete Dinosaur, 2nd Edition. Eds. Brett-Surman, M.K., Holtz, T.R. and Farlow, J.O. Bloomington, IN: Indiana University Press.

Osborn, H.F. 1933. Mounted Skeleton of Triceratops elatus. American Museum Novitates 654:1-14.

Paul, G.S. and Christiansen, P. 2000. Forelimb Posture in Neoceratopsian Dinosaurs: Implications for Gait and Locomotion. Paleobiology 26:3:450-465.

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Filed under AMNH, anatomy, dinosaurs, fossil mounts, history of science, marginocephalians, museums, NMNH, reptiles

First Full-Sized Dinosaurs: From Crystal Palace to Hadrosaurus

Last time, we covered how Albert Koch turned a tidy profit with his less-than-accurate fossil mounts, leading credible paleontologists to avoid involvement with full-sized reconstructions of extinct animals for much of the 19th century. With the exceptions of Juan Bautista Bru’s ground sloth and Charles Peale’s mastodon, all the fossil mounts that had been created thus far were horrendously inaccurate chimeras assembled by often disreputable showmen. Serious scientists were already struggling to disassociate themselves from these sensationalized displays of imaginary monsters, so naturally they avoided degrading their work further by participating in such frivolous spectacle.

The prevailing negative attitude toward fossil mounts among academics would begin to shift in 1868, when paleontologist Joseph Leidy and artist Benjamin Waterhouse Hawkins collaborated on a mount of Hadrosaurus, the first dinosaur to be scientifically described in America and the first dinosaur to be mounted in the world. While prehistoric animals were well known by the mid-19th century, the Hadrosaurus was so bizarre, so utterly unlike anything alive today, that it truly opened people’s eyes to the unexplored depths of the Earth’s primordial history. I have written about the Hadrosaurus mount before, but its creation was such a landmark event in the history of paleontology and particularly the public understanding of prehistory that it deserves to be contextualized more thoroughly.

Discovering Dinosaurs in Britain

In the early 1800s, American fossil hunters were busy poring over the bones mammoths, mastodons and other mammals. Across the Atlantic, however, it was all about reptiles. Scholars were pulling together the first cohesive history of life on earth, and Georges Cuvier was among the first to recognize distinct periods in which different sorts of creatures were dominant. There had been an Age of Mammals in the relatively recent past during which extinct animals were not so different from modern megafauna, but it was preceded by an Age of Reptiles, populated by giant-sized relatives of modern lizards and crocodilians. The marine ichthyosaurs and plesiosaurs unearthed by Mary Anning on the English coast were the first denizens of this era to be thoroughly studied, but they were soon followed by discoveries of terrestrial creatures. In 1824, geologist William Buckland received a partial jaw and a handful of postcranial bones found in the Oxfordshire shale. Recognizing the remains as those of a reptile, Buckland named the creature Megalosaurus, making it the first scientifically described non-avian dinosaur (honoring the unspoken agreement to ignore “Scrotum humanum”).

The partial jaw of Megalosaurus, the first named dinosaur.

The partial jaw of Megalosaurus, the first named dinosaur.

Of course, the word “dinosaur” did not yet exist. As covered by virtually every text ever written on paleontological history, it was anatomist Richard Owen who formally defined Dinosauria in 1842 as a distinct biological group. Owen defined dinosaurs based on anatomical characteristics shared by Megalosaurus and two other recently discovered prehistoric reptiles, Iguanodon and Hylaeosaurus (fatefully, and somewhat arbitrarily, he excluded pterosaurs and doomed paleontologists and educators to forever reminding people that pterodactyls are not dinosaurs). In addition to being an extremely prolific author (he wrote more than 600 papers in his lifetime), Owen was a talented publicist and quite probably knew what he was unleashing. The widely publicized formal definition of dinosaurs, accompanied by displays of unarticulated fossils at the Glasgow Museum, was akin to announcing that dragons were real. By giving dinosaurs their name, Owen created an icon for the prehistoric past that the public could not ignore.

“Dinosaur” soon became the word of the day in Victorian England. Looking to capitalize on this enthusiasm for paleontology, the Crystal Palace Company approached Owen in 1852 to oversee the creation of an unprecedented new exhibit. The company was building a park in the London suburb of Sydenham, meant to be a permanent home for the magnificent Crystal Palace, which had been built the previous year for the Great International Exhibition of the Works and Industry of All Nations. Concerned that the palace would not draw visitors to the park on its own, the Crystal Palace Company commissioned Owen and scientific illustrator Benjamin Waterhouse Hawkins to create a set of life-sized sculptures of dinosaurs and other prehistoric creatures, the first of their kind in the world. The sculptures were a tremendous undertaking: the Iguanodon, for instance, was supported by four 9-foot iron columns, and its body was built up with brick, tile and cement. Hawkins then sculpted its outer skin from more than 30 tons of clay. All told, more than a dozen animals were built, including Megalosaurus, Iguanodon, Hylaeosaurus and an assortment of marine reptiles and mammals.

The Crystal Palace dinosaurs under construction in Hawkin's studio.

The Crystal Palace dinosaurs under construction in Hawkin’s studio.

Queen Victoria herself presided over the opening ceremony of Crystal Palace Park in 1854, which was attended by 40,000 people. This was an important milestone because up until that point, only the broadest revelations in geology and paleontology made it out of the academic sphere. But as Hawkins himself put it, the Crystal Palace dinosaurs “might be properly described as one vast and combined experiment of visual education” (Hawkins 1853, 219). The general public could see firsthand the discoveries and conclusions of the most brilliant scientists of their age, in a format that could not only be readily understood and appreciated, but experienced. Full-sized reconstructions of prehistoric animals, including fossil mounts, continue to be built today for precisely this reason.

Recently restored Iguanodon sculptures. Wikimedia Commons.

Recently restored Iguanodon sculptures at Crystal Palace Park. Source

While the Crystal Palace dinosaurs are important historic artifacts and beautiful works of art in their own right, they have not aged well as accurate reconstructions. Owen only had the scrappiest of dinosaur fossils to work with, enough to conclude that they were reptiles and that they were big but not much else. As a result, the Megalosaurus and Iguanodon sculptures look like rotund lizards, as though a monitor lizard or iguana gained the mass and proportions of an elephant. By modern standards, these beasts look pretty ridiculous as representations of dinosaurs, but they were quite reasonable given what was known at the time, at least for a few years.

Dinosaurs of the Jersey Shore

And so at last Hadrosaurus enters the story. Just four years after the unveiling of the Crystal Palace sculptures, the first American dinosaur was found on a farm near Haddonfield, New Jersey (dinosaur footprints and teeth had been found earlier, but their affinity with the European reptiles was not recognized until later). William Foulke, a lawyer and geology enthusiast affiliated with the Philadelphia-based Academy of Natural Sciences, was at his winter home in Haddonfield when he paid a visit to his neighbor, John Hopkins. Hopkins told Foulke that he occasionally found large fossils on his land, which he generally gave away to interested friends and family members. With Hopkins’ permission, Foulke searched the site where the fossils had been found with the assistance of paleontology and anatomy specialist Joseph Leidy. Also a member of the Academy of Natural Sciences, Leidy is considered the founder of American paleontology and during the mid-1800s, he was the preeminent expert on the subject. At the Haddonfield site, Foulke and Leidy uncovered approximately a third of a dinosaur skeleton, including two  nearly complete limbs, 28 vertebrae, a partial pelvis, scattered teeth and two jaw fragments.

All known Hadrosaurus fossils, presently on display at the Academy of Natural Sciences.

All known Hadrosaurus fossils, presently on display at the Academy of Natural Sciences.

Now in possession of the most complete dinosaur skeleton yet found, Leidy began studying the fossils of what he would name Hadrosaurus foulkii (Foulke’s bulky lizard) in Philadelphia. The teeth in particular told Leidy that Hadrosaurus was similar to the European Iguanodon. Like IguanodonHadrosaurus was plainly an herbivore, and for reasons left unspecified Leidy surmised that it was amphibious, spending most of its time in freshwater marshes. Leidy noted that Hadrosaurus was a leaner and more gracile animal than Owen’s Crystal Palace reconstructions, but he was particularly interested in “the enormous disproportion between the fore and hind parts of the skeleton” (Leidy 1865). Given the large hindlimb and small forelimb, Leidy reasoned that Hadrosaurus was a habitual biped, and likened its posture to a kangaroo, with an upward-angled trunk and dragging tail. As such, we can credit Leidy for first envisioning the classic Godzilla pose for dinosaurs, which has been known to be inaccurate for decades but remains deeply ingrained in the public psyche.

Although the new information gleaned from Hadrosaurus made it clear that the Crystal Palace sculptures were hopelessly inaccurate, Leidy had been impressed by the Sydenham display and wanted to create a similar public attraction in the United States. Leidy invited Hawkins to prepare a new set of prehistoric animal sculptures for an exhibit in New York’s Central Park. Hawkins set up an on-site studio and began constructing a life-sized Hadrosaurus, in addition to a mastodon, a ground sloth and Laelaps, another New Jersey dinosaur. Unfortunately, Hawkins’ shop was destroyed one night by vandals, apparently working for corrupt politicians. What remained of the sculptures was buried in Central Park and the exhibit was cancelled.

Edit 4/20/2017: Leidy was not actually involved in planning the ill-fated Central Park display. Thanks to Raymond Rye for the tip!

The “Bulky Lizard” Mount

Instead of abandoning the project entirely, Hawkins and Leidy redirected the resources they had already prepared for the Central Park exhibit into a display at the Academy of Natural Sciences museum in Philadelphia. Leidy decided he wanted a mounted skeleton of Hadrosaurus, rather than a fully fleshed model as was originally planned. Such a display had not appeared in a credible museum since Charles Peale created his mastodon mount, but if anybody could get a fossil mount to be taken seriously, it was Leidy.

With only a partial Hadrosaurus skeleton to work with, Hawkins had to sculpt many of the bones from scratch, in the process inventing many of the mounting techniques that are still in use nearly a century and a half later. For instance, Hawkins created mirrored duplicates of the left limb bones for use on the animal’s right side, and reconstructed best-guess stand-ins for the skull, scapulae and much of the spinal column using modern animals as reference. Based on photographs like the one below, it appears that portions of the vertebral column were cast as large blocks, rather than individual vertebrae. The mount  was supported by a shaped metal rod running through the vertebrae, as well as a single vertical pole extending from the floor to the base of the neck. In fact, very little of the armature appears to have been externally visible, suggesting that making the skeleton as aesthetically clean as possible was a priority.

Hawkin's studio

Hadrosaurus under construction in Hawkins’ studio. Note the flightless bird mounts used for reference. From Carpenter et al. 1994.

The Hadrosaurus mount had a few eccentricities that are worth noting. First, the mount has seven cervical vertebrae, which is characteristic of mammals, not reptiles. Likewise, the scapulae and pelvis are also quite mammal-like. Hawkins was apparently using a kangaroo skeleton as reference in his studio, and it is plausible that this was the source of these mistakes. In addition, Hawkins had virtually no cranial material to work with (despite several repeat visits to the Haddonfield site by Academy members searching for the skull), so he had to make something up. He ended up basing the his sculpted skull on an iguana, one of the few exclusively herbivorous reptiles living today. Although fossils of Hadrosaurus relatives would later show that this was completely off the mark, it was very reasonable given what was known at the time.

The Hadrosaurus mount was unveiled at the Academy of Natural Sciences musuem in 1868, and the response was overwhelming. The typical annual attendance of 30,000 patrons more than doubled that year to 66,000, and the year after that saw more than 100,000 visitors. Traffic levels were so high that the Academy had to decrease the number of days it was open and enforce limits on daily attendance in order to prevent damage to the rest of the collection. Soon, the Academy was forced to relocate to a new, larger building in downtown Philadelphia, which it still occupies today.

The audience for the Hadrosaurus mount was expanded greatly in the 1870s by three plaster copies of the skeleton, which were sent to Princeton University in New Jersey, the Smithsonian Institution in Washington, DC and the Royal Scottish Museum in Edinburgh (the first dinosaur mount displayed in Europe). The Smithsonian copy had a particularly mobile existence: it was first displayed in  the castle on the south side of the National Mall, moved to the dedicated paleontology display in the Arts and Industries Building around 1890, and finally traded to the Field Museum in Chicago later in the decade. In Chicago, the Hadrosaurus was displayed in a spacious gallery alongside mounts of Megaloceros and Uintatherium, and it is in this context that the best surviving photographs of the Hadrosaurus mount were taken. Sadly, by the early 1900s all three casts had been destroyed or discarded by their host institutions, since they had either deteriorated badly or were deemed too inaccurate for continued display. The original Philadelphia mount was also dismantled, although the Hadrosaurus fossils are still at the Academy.

Hadrosaurus cast on display at the Field Museum. Field Museum Photo Archives.

Hadrosaurus cast on display at the Field Museum. Field Museum Photo Archives.

Why was the Hadrosaurus mount such a big deal? For one thing, it was different from previous fossil mounts in that it was the product of the best scientific research of the day. This was not the work of a traveling showman but a display created by the preeminent scientific society of the era, with all the mystique and prestige that came with it. Most importantly, however, the Hadrosaurus mount presented the first ever opportunity to stand in the presence of a dinosaur. By the mid-19th century, western civilization had had ample opportunity to come to terms with the fact that organisms could become extinct, but for the most part the fossils on display were similar to familiar animals like horses, elephants and deer. The Hadrosaurus, however, was virtually incomparable to anything alive today. It was a monster from a primordial world, incontrovertible evidence that the Earth had once been a very different place. By comparison, the Crystal Palace sculptures were essentially oversized lizards, and therefore fairly relateable.  The Hadrosaurus was the real turning point, the moment the public got their first glimpse into the depths of prehistory. For 15 years, the Hadrosaurus was the only real dinosaur on display anywhere in the world, so it is no wonder that people flocked to see it.

Of course, the Hadrosaurus was only the beginning of the torrent of dinosaur fossils that would be unearthed in the late 19th century. It would prove to be but a hint at the amazing diversity and scale of the dinosaurs that would be revealed in the American west, as well as the scores of fossil mounts that would soon spring up in museums.

References

Carpenter, K., Madsen, J.H. and Lewis, L. (1994). “Mounting of Fossil Vertebrate Skeletons.” In Vertebrate Paleontological Techniques, Vol. 1. Cambridge, UK: Cambridge University Press.

Leidy, J. (1865). “Cretaceous Reptiles of the United States.” Smithsonian Contributions to Knowledge. 14: 1-102. 

Waterhouse Hawkins, B. (1853). “On Visual Education as Applied to Geology.” Journal of the Society of Arts. 2: 444-449.

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Filed under anatomy, dinosaurs, field work, fossil mounts, history of science, museums, ornithopods, paleoart, reptiles

Extinct Monsters: Gilmore’s Diplodocus

Click here to start the Extinct Monsters series from the beginning.

More than 80 years ago, Smithsonian paleontologist Charles Whitney Gilmore supervised the installation of the mounted Diplodocus skeleton known as USNM 10865. In December 2014, that same skeleton was finally disassembled for conservation and eventual re-mounting.This post is about the history of this particular mount: where it came from, who put it together, and what it has and continues to tell us about prehistory.

Predecessor at CMNH

The story of the NMNH Diplodocus mount actually began in Pittsburgh, Pennsylvania around the turn of the century. In November of 1898, Steel tycoon-turned-philanthropist Andrew Carnegie read that the remains of a giant “Brontosaurus” had been discovered in Wyoming. Carnegie’s interest was piqued and the following year, he contributed $10,000 to the Carnegie Museum of Natural History (which he had founded two years earlier) to find a complete “Brontosaurus” – or something like it – for display in Pittsburgh. Perhaps proving that money can indeed buy anything, on July 4th, 1989 the CMNH team found a reasonably complete sauropod skeleton in Sheep Creek Basin, Wyoming. CMNH Curator of Paleontology John Bell Hatcher declared the specimen to be a new species, which he named for the Museum’s benefactor: Diplodocus carnegii.

Back in Pittsburgh, the task of preparing and mounting the fossils fell to preparator Arthur Coggeshall and his staff.  Creating a permanent armature for a delicate 84-foot skeleton was a monumental undertaking, beyond anything that had ever been attempted before. Coggeshall used a steel rod, shaped to the contours of the vertebral column, as the basis for the mount. Once the backbone was in place, the limbs, ribs, and other extremities were mounted on steel rods of their own and attached to the rest of the skeleton. The fossils were connected to the steel armature by drilling screws and bolts directly into the bone. Since the original Diplodocus carnegii skeleton was not complete, the mount was supplemented with fossils uncovered during subsequent field seasons at Sheep Creek and elsewhere in Wyoming.

The CMNH Diplodocus was unveiled in 1907 in a brand-new wing that had been constructed to display it. Although the American Museum of Natural History had by that point completed a sauropod mount of their own, the Pittsburgh display was well-received by paleontologists and laypeople alike. Not to be bested by the New York competition, Carnegie also commissioned eight Diplodocus replicas, which he donated to museums throughout Europe and Latin America.

The original CMNH Diplodocus mount, in the hall built specifically to accomodate it. Source

The original CMNH Diplodocus mount, in the hall built specifically to accommodate it. Source

This wave of publicity allowed the paleontology staff at CMNH and elsewhere to continue to undergo large-scale fossil hunting expeditions. In 1909, a team led by Earl Douglass hit the jackpot north of Jensen, Utah. At the site now known as Dinosaur National Monument, CMNH teams excavated over 300 tons of Jurassic fossils over 13 field seasons. The immensely productive “Dinosaur Quarry” site is thought to represent a prehistoric river bar, where dead animals from upsteam accumulated over time. In addition to an assortment of crocodiles and other small reptiles, this location has yielded remains of Apatosaurus, Diplodocus, Stegosaurus, Allosaurus and many other taxa. Although the site was far from exhausted, the CMNH team moved on in 1922, at which point paleontologist Charles Gilmore from the United States National Museum took over.

USNM Excavation at Dinosaur National Monument

Gilmore led the first USNM field season at Dinosaur National Monument in May of 1923. In their final year at the site, the CMNH team had located two partial sauropod skeletons. Gilmore opted to focus on excavating these “in order to secure a mountable skeleton” for display (Gilmore 1932). As with the CMNH team before them, the primary motivation of Gilmore’s team was not scientific research, but to bring back spectacular display specimens. Gilmore was unarguably a phenomenal scientist who made lasting contributions to our knowledge about prehistory, but this focus on impressive displays was typical of early 20th century paleontology. As such, valuable taphonomic and ecological data that would been collected by modern paleontologists was probably destroyed when unearthing this and other exhibition-caliber dinosaur specimens.

Once the excavation began, Gilmore decided that the Diplodocus skeleton dubbed specimen 355 was the best candidate for a mount. The skeleton consisted of an articulated vertebral column, from the 15th cervical to the 5th caudal, a separated but virtually complete tail, the pelvis, both pectoral girdles, much of the rib cage, both humeri, and a complete left hind limb. Unfortunately, the head and most of the neck had eroded out of the hillside and  long since weathered away. Some elements not preserved with specimen 355 were reportedly cherry-picked from another specimen at the same site. Again, this sort of selective excavation is discouraged today, but was typical at the time. On August 8, the team wrapped up and shipped 25 tons of material back to Washington, DC via railway.

Preparation, Mounting and Description

Preparing and mounting the Diplodocus was, according to Gilmore, the single most ambitious undertaking attempted by the department during his tenure.  In his words, “the magnitude of the task, by a small force, of preparing one of these huge skeletons for public exhibition can be fully appreciated only by those who have passed through such an experience” (Gilmore 1932).  Gilmore, along with preparators Norman Boss, Thomas Horne, and John Barrett, spent  2,545 working days over the course of six years preparing the skeleton for exhibition. Gilmore reported that his team  followed the method Arthur Coggeshall had developed at CMNH over 20 years earlier for mounting their sauropod. The vertebral column was assembled first, supported by a series of steel rods. This structure was mounted at the appropriate height on four upright steel beams securely anchored to the floor. Limbs and other extremities were subsequently added, with steel rods shaped to the contours of the fossils supporting each portion of the skeleton.

Diplodocus under construction, ca. 1930. Source

Diplodocus under construction, ca. 1930. Source

Missing parts of the skeleton, including the right hindlimb and the distal portions of the forelimbs, were filled in using casts of the Carnegie Diplodocus. According to Gilmore, the casted elements were colored “to harmonize with the actual bones but with sufficient difference to be at once distinguished from the originals” (Gilmore 1932). This is noteworthy, because the creators of other dinosaur mounts at that time had been known to deliberately disguise artificial elements by painting them to match the fossils. Although the Smithsonian Diplodocus was a composite of multiple specimens and therefore does not represent any single animal that actually existed, the decision to make the casted elements readily visible represents a degree of honesty and integrity that is more common in modern museum displays than it was in Gilmore’s time.

Gilmore presents plans for the in-progress Diplodocus mount at the 1927 Conference of the Future of the Smithsonian. Photo courtesy of the Smithsonian Institution Archives.

In the process of preparing and mounting the Diplodocus (at this point designated USNM 10865), Gilmore was able to further refine our understanding of sauropod physiology. Looking at the specimen, Gilmore was easily able to dismiss notions by earlier workers that Diplodocus had sprawled like a crocodile, asserting that “the crocodilian attitude for Diplodocus involves anotomical imposibilities” (Gilmore 1932). Additionally, since the entire dorsal portion of the vertebral column was present and intact, Gilmore determined that the presacral vertebrae (in the lower back) arch downward, toward the sacrum. The CMNH Diplodocus and AMNH Apatosaurus had been mounted with completely straight backs, so Gilmore was able to create a more accurate mount. Studying the articulated vertebral column also convinced Gilmore to raise the tail higher than in previous sauropod mounts. Although it would be decades before paleontologists started raising the tail completely clear of the ground, this was certainly a step in the right direction. Gilmore refrained, however, from definitively assigning USNM 10865 to a particular species of Diplodocus, since at the time (and to this day, apparently) the differences among the named species of this genus were unclear.

Exhibition and Legacy

USNM 10865 in the Hall of Extinct Monsters, circa 1932. Photo courtesy of the Smithsonian Institution Archives.

The completed Diplodocus skeleton was 70 feet, 2 inches long and 12 feet, five inches tall at the hips, making it about 14 feet shorter in length than its CMNH counterpart. The mount was introduced to the Hall of Extinct Monsters at the United States National Museum in 1931, positioned atop three pedestals so that visitors could walk right underneath it. The Diplodocus was placed right in the center of the  gallery, facing west so that it could stare down visitors as they entered the hall.

The unveiling of the Diplodocus mount was a big deal, but did not catch the public’s attention in quite the same way as its CMNH predecessor. After all, by 1931 several of the other major natural history museums had had sauropods on display for over two decades. Nevertheless, for residents and visitors in Washington, DC the new mount was an unforgettable look at the life of the past.

The Diplodocus, as it stood from 1963 through 1981. Image courtesy of the Smithsonian Institution Archives.

The Diplodocus, as it stood from 1963 through 1981. Image courtesy of the Smithsonian Institution Archives.

The Diplodocus was not moved during the 1963 modernization of the fossil exhibits, but the walkable area around the mount was significantly reduced. Visitors could no longer walk under the skeleton, or get as close to it. The Diplodocus was not moved during the 1981 renovation, either, but the neck support coming up from the floor was replaced by less intrusive cables suspended from the ceiling. In the new exhibit, the sauropod centerpiece was surrounded by contemporaneous friends from the Morrison Formation, including Stegosaurus, Camptosaurus, Camarasaurus and Allosaurus.

National Museum of Natural History in Washington, DC.

Diplodocus as it stood from 1981-2014. Photo by the author.

From 1931 to 2014, the Diplodocus remained an unchanging fixture of the Museum’s east wing. Although this specimen’s story has not been as widely told as that of the CMNH Diplodocus, the Smithsonian sauropod is certainly just as interesting. For more than 80 years, USNM 10865 has mesmerized generations of viewers with its size and elegance.  What’s more, this specimen, and the associated measurements and drawings meticulously prepared by Gilmore, are frequently referred to in publications by modern paleontologists. For its contributions to public education and to scientific inquiry, USNM 10865 is one to celebrate.

References

Brinkman, P.D. The Second Jurassic Dinosaur Rush: Museums and Paleontology in America at the Turn of the 20th Century. Chicago: University of Chicago Press, 2010.

Gilmore, C.W. “On a Newly Mounted Skeleton of Diplodocus in the United States National Museum.” Proceedings of the United States National Museum 81:1-21, 1932.

Gilmore, C.W. “A History of the Division of Vertebrate Paleontology in the United States National Museum.” Proceedings of the United States National Museum 90, 1941.

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Filed under anatomy, CMNH, dinosaurs, exhibits, Extinct Monsters, field work, fossil mounts, history of science, museums, NMNH, reptiles, sauropods

Medullary Bone and the Dinosaur-Bird Link

One of the coolest lines of evidence that birds are extant dinosaurs is the presence of medullary bone in multiple dinosaur species. Medullary bone (hereafter referred to as MB, to avoid confusion with the medullary surface) is a temporary tissue that forms on the interior surfaces of the long bones of birds. MB is identified by unique collagen organization: it is both densely mineralized and strongly vascularized. This structure helps MB serve its purpose as a readily retrieved source of calcium for use in forming eggshells, and prevents incapacitating bone resorption during this process. Among extant animals, MB is only found in mature female birds in the process of producing eggs. Its creation is triggered by hormones during the onset of ovulation, and it disappears during the laying process. Among extant animals, MB is only known in birds. However, in 2005 Mary Schweitzer and colleagues reported their discovery of medullary bone in a Tyrannosaurus rex individual. Lee and Werning followed up on this research in 2007 by reporting MB in the theropod Allosaurus and the ornithopod Tenontosaurus.

Medullary bone in modern Gallus and fossil Tyrannosaurus. From http://www.abc.net.au/science.

Since MB is unique to reproductively active females, most popular coverage of dinosaur MB  has focused on its potential use for determining the sex and life stage of individual dinosaur specimens. We shouldn’t, however, lose sight of the fact that MB is an independent line of evidence supporting a close phylogenetic relationship between dinosaurs and birds. Nearly all paleontologists agree that the evidence that birds are dinosaurs is overwhelming, and MB is but a drop in the ocean of shared characters between birds and dinosaurs. Nevertheless, it is noteworthy that few authors have attempted to challenge Schweitzer’s initial publication.

The only work I have found  that disputes Schweitzer and colleagues is the dissertation of Dr. Devon Quick  (.pdf link), in which Dr. Quick and Dr. John Ruben investigated the reliability of the methods used to recognize MB in the fossil record using extant animals. This is not, incidentally, the only work by Quick and Ruben challenging the dinosaur-bird connection. As a doe-eyed student, I’d like to take a shot at reviewing this paper. And since I’m posting it publicly, I of course welcome anyone who’d be so kind as to call me out for being wrong.

Quick and Ruben looked at cross-sections of the femora and tibiotarsi of a crocodilian (Alligator mississippiensis) and several birds. Scanning electron microscopy revealed that the medullary surfaces of the tibiotarsi of  reproductively active birds displayed the highly contoured and floccular texture that is characteristic of MB. Likewise, the male and non-reproductively active female birds displayed smooth medullary surfaces. In this regard, Quick and Ruben are in agreement with previous work. However, the authors also reported that the medullary cavity of the alligator femur contained “material superficially similar to…avian medullary bone” (Quick and Ruben 2008). This material was limited to the immediate diaphyseal side of the metaphysis, making it much less extensive than what was observed in birds. Since the alligator individual used in the study was a juvenile male, it was almost certainly not producing reproductively-specific MB. From this observation, the authors conclude from these data that a floccular texture may indicate early-stage bone mineralization and is not a reliable indicator of MB.

Quick and Ruben’s results are unconvincing in part due to a weak experimental design. Their conclusions are dependent on observations gleaned from a single alligator specimen, which is not an adequate sample. The authors’ conclusions would carry more weight if they had looked at multiple individuals. It would also be beneficial to compare males, females, adults and juveniles. Ideally, additionally crocodilian species ought to be included in the study, as well. Schweitzer and colleagues carried out a similar investigation, in which they looked for evidence of MB in multiple alligators, including gravid females, males and juveniles (Schweitzer et al. 2007). Schweitzer and colleagues found no evidence of MB, even with estrogen stimulation, and their larger sample size allows their study to carry more weight than that of Quick and Ruben. Furthermore, although Quick and Ruben assert that that “histological aspects of Tyrannosaurus tissues that are supposedly consistent with an avian-style reproductive physiology were not analyzed carefully”, they did not look at the Tyrannosaurus material as part of their study. Accordingly, no evidence is provided that the structures the authors observed on their alligator were synonymous with those observed by Schweitzer and colleagues on Tyrannosaurus. Finally, Quick and Ruben’s observations are focused on the floccular texture used to identify MB, when in fact Schweitzer and colleagues used several other indicators, including extensive vascularization, to identify MB in Tyrannosaurus. It is notable that the structure, thickness and texture of MB in modern birds varies considerably based on the specifics of the animal’s reproductive biology and the size of the taxa. Given that Tyrannosaurus is several orders of magnitude larger than most extant birds, some structural difference is to be expected (wow, that sentence had some serious science snark).

Quick and Ruben suggest that the floccular texture on the alligator bone may be the result of early-stage mineralization, which would be consistent with the sub-adult status of the individual they used in the study. The authors go on to speculate that a similar explanation might account for the evidence of MB in Tyrannosaurus. Again, it would have been helpful if the authors had amassed more examples of sub-adult archosaurs undergoing skeletal mineralization, and compared them directly to the Tyrannosaurus material in question, rather than merely speculating. If the Tyrannosaurus was forming MB, this would be consistent with information from lines of arrested growth in Tyrannosaurus and other dinosaurs, which indicates that dinosaurs became reproductively active before reaching adult size.

Having reached the somewhat tenuous conclusion that texture is not a reliable indicator of MB, Quick and Ruben go on to argue that even if MB is present in dinosaurs, the fact that it has been reported in both saurischians and ornithiscians “offers no particular insight into the phylogenetic origins of birds.” On the contrary, MB is an independently observable feature that unites the crown group Dinosauria with Avialae, and therefore supports the consensus that Avialae is bracketed by Dinosauria. At the very least, MB suggests marked similarity in reproductive strategies employed by birds and dinosaurs. As demonstrated by Schweitzer and colleagues, MB is not known in crocodilians. Quick and Ruben freely admit this, which makes their statement that MB “may well be a plesiomorphic trait that first evolved in basal archosaurs” nonsensical (Quick and Ruben 2008). The authors could theoretically argue that MB production is primitive but was lost in modern crocodilians, but there is no evidence for this.

Overall, Quick and Ruben’s work is hindered by weak experimental design and vague, unsupported conclusions. Given that a similar but more rigorous study regarding MB in crocodilians has already been carried out by Schweitzer and colleagues, Quick and Ruben’s interpretations are not convincing. Even the broadest interpretation of the available evidence indicates that MB originated after the divergence of crocodilymorphs from the main archosaur line. The phylogeny postulated by Schweitzer and colleagues remains most tenable, in which MB originated in early dinosaurs, and was inherited by ornithiscians, tyrannosaurids and modern birds (Schweitzer et al. 2005).

References

Lee, A. H. and Werning, S. “Sexual maturity in growing dinosaurs does not fit reptilian growth models.” 2007. PNAS 105:2:582-587.

Quick, D. E. and Ruben, J. A. “Amniote bone structure and longbone histology in birds, alligators and the theropod Tyrannosaurus rex.” 2008. Oregon State University.

Schweitzer, M. H., Elsey, R. M., Dacke, C. G., Horner, J. R. and Lamm, E. T. “Do egg-laying crocodilian (Alligator mississippiensis) archosaurs form medullary bone?” 2007. Bone 40: 1152-1158.

Schweitzer, M. H., Wittmeyer, J. L. and Horner, J. R. “Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex.”2005. Science 308: 1456-1460.

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January 20, 2012 · 6:26 am