Tag Archives: fossils

Framing Fossil Exhibits: Phylogeny – An Addendum

After I posted my slightly critical evaluation of the AMNH fossil halls last month, a reader suggested I take a look at Next of Kin by Lowell Dingus. Dr. Dingus was the project director for the 1995 renovation, and his book chronicles the decade-long process of overhauling these genre-defining exhibits. It also includes plenty of gorgeous photos of the AMNH fossil exhibits past and present. Although out of print, Next of Kin can be found online for next to nothing. If you find anything on this blog interesting, I would call this book required reading. I cannot recommend it enough.

Edwin Colbert designed this version of the Jurassic exhibit in 1956. This space is now the Hall of Saurichian Dinosaurs. Photo from Dingus 1996.

Next of Kin is full of fascinating information about the renovation, and the history of the halls in general. For instance, it was news to me that the original plan in 1987 was to modernize only the two fossil mammal halls. When William Moynihan took over as Director of AMNH the following year, however, he asked in a planning meeting why the dinosaur exhibits weren’t being renovated, and soon the project expanded to include all six halls on the 4th floor. Apparently the approaches to interpretation, aesthetics, and layout that characterize the exhibits today were already fully formed. The concept of a main pathway with branching alcoves representing individual clades was in place, so the exhibit team only needed to set the starting point back a ways to include the dinosaurs and the rest of the vertebrate family tree. Restoring the historic interior architecture, obscured since the 1950s, was also an early priority. Dingus relates how he wanted to eliminate the “black box” look of the midcentury exhibits and let natural light back into the halls. In my opinion, the well-lit, airy aesthetic is one of the standout features of the AMNH fossil halls, and one other museums might do well to emulate.

Dingus also points out a number of clever design choices that I missed during my last visit to the museum. For instance, the primate section was deliberately placed in the center of the mammal hall, to avoid the implications of directed evolution and human superiority that once marked the AMNH exhibits. Another cool feature is the use of minimalist metal armatures to suggest the size and shape of animals for which only limited material is available. This is an artful way to convey the dimensions of these species without resorting to fabricating most of the skeleton. Again, this is something I’d love to see more of at other museums.

Photo by the author.

Minimalist armatures suggest the size and shape of incomplete specimens. Photo by the author.

Still, I was most interested in reading Dingus’s rationale for the design and layout of the AMNH fossil halls. In my previous post, I argued that the phylogenetic arrangement was a worthwhile experiment, but in practice it may not be the most practical way to make the history of life meaningful to the museum’s primary audience. More than any other organizational scheme, phylogeny is the way biologists think about the natural world, and I applaud the effort to encourage visitors to look at fossils the way scientists do. However, even the most basic elements of evolutionary classification are specialized knowledge, and require a daunting amount of up-front explanation (especially when targeting multiple age groups). I don’t think this integrates well with the multi-entrance, non-linear exhibit space at AMNH.

During the initial planning stages of the AMNH renovation, Dingus and other staff toured several large-scale paleontology exhibits in North America and Europe. Dingus clearly did not like what he saw, lamenting that “some institutions rely heavily on easy-to-understand, anecdotal labels and robotic recreations of dinosaurs that appeal to the lowest common denominator of visitor intellect.” He rejected the “prominent contemporary school of exhibit design that advocates only giving the visitor what he or she asks for,” feeling strongly that his institution could do better. Referring to the renovation as a “scientific crusade,” Dingus was inspired to challenge his audience in a way that peer institutions did not. Dingus and his colleagues wanted to show visitors the real science behind paleontological reconstructions. The phylogeny-based arrangement was central to that goal, emphasizing rigorous anatomical analysis and empiricism in a field historically characterized by idle speculation.

Age of Man

The orientation hall is in the oldest of the 4th floor exhibit spaces. Until the 1960s, this space was occupied by the Hall of the Age of Man. Photo from Dingus 1996.

I agree wholeheartedly with all of this. There was a period in the 80s and 90s (I think the worst is behind us) when the trend toward visitor-focused, educational exhibits got mixed up with a push to make museums more competitive with other leisure activities. Customer enjoyment was valued above all else, even if it meant sacrificing the informative content and access to real specimens that made museums worthwhile institutions in the first place. The resulting displays were filled with paltry nonsense like simulators, pointless computer terminals, and the aforementioned robot dinosaurs*. These exhibits imitated amusement parks, but with only a fraction of the budget they quickly fell into disrepair and technological obsolescence. Despite being museums’ most important and unique resources, curators and research staff found themselves increasingly divorced from their institutions’ public faces.

*Fine, I admit robot dinosaurs are cool. But I’d prefer that they weren’t in museums.

Under these circumstances, a backlash is quite understandable. Nevertheless, it is a common mistake (which I am by no means accusing Dingus of making!) that a visitor-centered exhibit is the same as a frivolous one. When educators push for audience-focused exhibits, they have the same goal as curators: to communicate as much content as possible. Audience-focused exhibits aren’t about dumbing down or eliminating content. They’re about presenting content in a way that effectively reaches the museum’s diverse audience. The AMNH fossil halls would work well for an informed adult visitor with ample time to inspect every specimen and read every label. But this is not the typical audience for natural history museums, and unless AMNH is a major outlier, it’s not the core audience for these exhibits. Most visitors come in mixed-aged groups. The trip to the museum is a social experience, and interactions occur among visitors as much as they occur between visitors and the exhibits. The best museums anticipate and meet the needs of these visitors in order to provide a quality learning experience.


An updated version of the classic (and classically misleading) horse evolution exhibit. Photo by the author.

It’s admittedly fun to share horror stories about dumb comments overheard in museums. Who in this field hasn’t rolled their eyes at the parent who makes up an answer to their child’s question, when the correct information is on the sign right in front of them? And yet, some of the blame for this failed educational encounter should fall on the museum. Why was that parent unable to spot the relevant information with a quick glace? Can we design signage so that the most important information is legible on the move, or from across the room? Can we correct commonly misunderstood concepts in intuitive ways?

As Dingus argues, it’s important to aim high in the amount of information we want to convey. There’s nothing worse than a condescending teacher. But a carefully-honed message in common language will always be more successful than a textbook on the wall. Happily, this is the way the wind is blowing these days. In a strong reversal of the situation a decade ago, curators now work closely with educators on the front lines to produce exhibits that are both accessible and intellectually challenging. It’s been 20 years since AMNH opened the latest version of its fossil exhibits…perhaps a new and even better iteration is already on its way!


Dingus, L. (1996). Next of Kin: Great Fossils at the American Museum of Natural History. New York, NY: Rizzoli International Publications, Inc.


Filed under AMNH, education, exhibits, fossil mounts, mammals, museums, opinion, reviews, science communication, systematics

The Carnegie Quarry Diaspora

About 150 million years ago, a severe drought ravaged the western interior of North America. In eastern Utah, malnourished dinosaurs gathered near a dwindling river. Unwilling or unable to leave the water source, they eventually died of thirst or disease. When rain finally returned to the region, three or four successive flash floods washed dozens of animal carcasses into a relatively small depositional area to the southeast. Today, this site is known as the Carnegie Quarry at Dinosaur National Monument, and it is one of the most incredible fossil sites in the world.

Dinosaur National Monument interns collect data on the quarry wall.

Dinosaur National Monument interns collect data on the quarry wall. Source

Today, a structure encompassing a 180-foot section of the deposit (less than half its total length) allows visitors to view nearly 1400 dinosaur bones in situ. However, the fossils on display at Dinosaur National Monument represent only a portion of the material found at the Carnegie Quarry. Between the site’s discovery in 1908 and the establishment of the quarry wall exhibit, more than 20 reasonably complete dinosaur skeletons and dozens more incomplete specimens were excavated and distributed to museums in the US and Canada. No less than eleven mounted skeletons have been created from this material, and they are all still on display today. Although they are thousands of miles from their place of discovery and exhibited in four different cities, these mounts all represent individuals that lived and died in the same environment. They may have even encountered each other in life!

The Discovery

Earl Douglass was already an established fossil hunter when the Carnegie Museum of Natural History hired him in 1902. Late in the 1909 field season, Douglass was prospecting near the confluence of the Green and Yampa Rivers when he spotted a series of sauropod vertebrae eroding out of the rocks. Once Douglass and his crew began excavating the fossils, it became apparent that they had not just one remarkably complete dinosaur, but several. Douglass called it a “beautiful sight,” and CMNH director William Holland could barely contain his glee in his reports back to the Pittsburgh museum. Under Douglass’s management, CMNH crews worked at what became known as the Carnegie Quarry for 13 years. The dinosaur fossils were jumbled and often overlaid one another, so the excavators had to work on multiple skeletons simultaneously. The especially hard sandstone also slowed their work, and the team regularly resorted to huge horse-drawn plows and even dynamite to reach the fossils. Eventually railway tracks were installed to help transport blocks of sandstone out of the quarry.

In 1915, Holland successfully petitioned Woodrow Wilson to preserve the site as a national monument. CMNH crews continued to excavate until early 1923. At that point, their primary benefactor Andrew Carnegie had died, and funding for field work was dwindling. Other museums collected from the quarry periodically in the years that followed, but Douglass’s idea to contain the remaining fossils in an on-site museum was not realized until 1958.

The Mounts


CMNH Apatosaurus. Historic photo from McGinnis 1982; modern photo source.

Apatosaurus louisae – CM 3018

The CMNH Apatosaurus was the first dinosaur discovered at the Carnegie Quarry. After Douglass first spotted the articulated caudal vertebrae in August of 1909, his crew spent several months extracting the rest of the skeleton from the rocks. The excavation continued into early 1910, and by the time they were finished they had the most complete Apatosaurus ever found – a title the specimen holds to this day. Holland mounted the 77-foot skeleton alongside the museum’s Diplodocus in just three years, at the time a record for a sauropod mount.

Holland famously left his Apatosaurus headless for decades due to a disagreement with Henry Osborn of the American Museum of Natural History. Douglass recovered a skull that almost certainly belonged to the Apatosaurus, but Holland opted not to use it because it contradicted the sculpted head already in place on the AMNH Apatosaurus mount. After Holland’s death in 1932, museum staff quietly added a casted Camarasaurus skull as a placeholder. This was finally replaced with a proper Apatosaurus skull in 1979. More recently, the team at Phil Fraley Productions disassembled and restored the Apatosaurus, along with the rest of the classic CMNH dinosaurs. Since 2007, this specimen has been back on display in a more graceful modern pose.

Fancy fisheye photo.

AMNH Barosaurus. Source

Barosaurus lentus – AMNH 6341

When the CMNH team discovered this skeleton in 1912, they assumed it was yet another specimen of the well-known Diplodocus. It was harvested for parts, with portions sent to CMNH, the United States National Museum, and the University of Utah to supplement their displays. When the specimen turned out to be the more obscure sauropod Barosaurus, it languished in pieces for many years. Barnum Brown of AMNH was making a circuit of the fossil collections at various natural history museums when he rediscovered this specimen. Through a series of purchases and trades, the Barosaurus was reunited at AMNH in 1929.

Nevertheless, AMNH quickly abandoned plans to mount the Barosaurus – the museum already had a sauropod on display, and there wasn’t enough floor space for another one. It wouldn’t go on display until 1991, when Lowell Dingus conceived of the idea to mount the Barosaurus in a spectacular rearing pose as part of the renovation of the Theodore Roosevelt Rotunda. Peter May took on the project – one of the first mounts produced by his company Research Casting International. The resulting display, actually a cast, is the tallest free-standing dinosaur mount in the world.

ROM Barosaurus.

ROM Barosaurus. Source

Barosaurus lentus – ROM 3670

Douglass recovered a second partial Barosaurus skeleton in 1912, which consisted of a mostly complete torso and parts of each leg. It stayed in the CMNH collections for many years, until they traded it to the Royal Ontario Museum in 1962. ROM staff intended to mount the skeleton, but once again this was cancelled due to a lack of space. David Evans was developing a new ROM paleontology exhibit in 2007 when he learned that the museum had most of a Barosaurus sitting in its collections. With only weeks remaining before the exhibit’s opening, Evans tapped Research Casting International to mount the sauropod, supplemented with a replica neck and tail from the AMNH version.

Allosaurus fragilis – CM 11844

Several Allosaurus specimens are known from the Carnegie Quarry, but the one on display at CMNH is one of the largest. Douglass and his team excavated this 35-foot skeleton between 1913 and 1915. The mount was built in 1938. Although the specimen included a partial skull, the exhibit team swapped it with a cast of a more complete skull (also found in the Carnegie Quarry) from the collections of the University of Utah. This mount also includes casts of the arms of USNM 4734, an Allosaurus collected for O.C. Marsh.

Stegosaurus ungulatus – CM 11341

The CMNH Stegosaurus is a composite of several individuals excavated from the Carnegie Quarry between 1920 and 1922. Museum staff completed the 21 foot-long mount in 1940, using a skull cast from USNM 8612. Casts of this skeleton were distributed to several other museums at some point, one of which is on display at the University of Nebraska State Museum. Phil Fraley’s company remounted the CMNH original in 2007.

Carnegie Camarasaurus.

Carnegie Camarasaurus. Source

Camarasaurus lentus – CM 11338

This juvenile Camarasaurus is the most complete sauropod ever found. It is displayed as a relief mount almost exactly as it was discovered, with two exceptions. The left leg was swapped with a more complete one from another individual, and the tail was re-positioned to create a more aesthetically pleasing mount. Casts of this skeleton are displayed at museums throughout the United States, including Dinosaur National Monument, but the original is at CMNH. This specimen is also notable because its left scapula is preserved in its life position, making it a helpful model for skeletal reconstructions and exhibit mounts.

NMNH Camarasaurus. Photo by the author.

NMNH Camarasaurus. Photo by the author.

Camarasaurus lentus – USNM 13786

The second best Camarasaurus also comes from Carnegie Quarry, but it is a considerably larger individual. Only the tail and a few odds and ends were missing. CMNH kept the specimen for several years before trading it to USNM in 1933 for a set of Pliocene horse skeletons. Norman Boss prepared the specimen in full view of the public during the 1936 Texas Centennial Exposition – one of the first known examples of such an exhibit. The completed mount appeared at USNM in the 1950s, sporting the tail of another Camarasaurus. At over 30 feet long, this skeleton is one of the largest dinosaurs on display at the Smithsonian. Unfortunately, the death pose somewhat limits the effect. The Camarasaurus was taken off exhibit in late 2014 for conservation and remounting. When it returns, it will be standing on its feet for the first time in 150 million years, taking its rightful place as one of the museum’s most impressive dinosaurs.

DMNH Diplodocus. Source

DMNH Diplodocus. Source

Diplodocus longus – DMNH 1494

Since this Dipldodocus was found somewhat disarticulated, Douglass suggested that the carcass may have been twisted apart while rolling downstream. AMNH held on to this skeleton for some time before trading it to the Denver Museum of Nature and Science in 1936 for two mammoth skeletons. Preparator Phillip Reinheimer mounted the skeleton with the help of 40 workers assigned to the museum through the Works Progress Administration. Additional Diplodocus fossils collected by William DeWeese (actually the first dinosaur specimens acquired by the museum) were also used to complete the mount. The Diplodocus remained on view until 1989, when Ken Carpenter and others restored and remounted the sauropod, elevating its tail and making its neck sweep gracefully to the left. The improved mount has been on display since 1995.

CMNH Camptosaurus.

CMNH Camptosaurus. Historic photo from McGinnis 1982; modern photo source.

Camptosaurus aphanoecetes – CM 11337

Douglass found this controversial small ornithopod in 1922, and correctly matched it with an isolated leg several feet away. It was first identified as Camptosaurus medius, but in 2008 Ken Carpenter reassigned it to the new species C. aphanoecetes. A 2011 phylogenic study by Andrew McDonald moved this specimen to a new genus, Uteodon. Carpenter, however, asserts that McDonald’s analysis was based on an incorrectly associated Dryosaurus braincase.

CMNH staff assembled the fossils into a relief mount in 1940. The skull, hindfeet, and tail were all sculpted. During the 2007 renovation, the Phil Fraley Productions team extracted the fossils from the plaster slab, even managing to preserve the delicate ossified dorsal tendons. They then created a new, three-dimensional mount, which features a revised replica skull.

Modern photo by the author.

CMNH Dryosaurus. Historic photo from McGinnis 1982; modern photo by the author.

Dryosaurus altus – CM 3392

This Dryosaurus skeleton is the most complete of several collected at Dinosaur National Monument. The tail is missing, and given the completeness of the rest of the skeleton it may well have been destroyed when Douglass’s crew was blasting through rock to get to the bone layer. The Dryosaurus entered the CMNH collections in 1922, and was assembled as a 9 foot-long relief mount in 1940. In 2007, Fraley’s team removed the fossils from the plaster matrix, and just as they did with the Camptosaurus, constructed a standing mount. To date, this is the only mounted Dryosaurus specimen in the world. It is displayed alongside a juvenile Ceratosaurus cast acquired from Western Paleontological Laboratories.

National Museum of Natural History in Washington, DC.

NMNH Diplodocus. Photo by the author.

Diplodocus sp. – USNM 10865

The National Museum of Natural History’s Diplodocus was one of the last articulated skeletons removed from the Carnegie Quarry. When the CMNH crew closed up shop, Charles Gilmore of the Smithsonian moved in to recover one of the sauropod skeletons Douglass left behind. In 1923, Gilmore’s team excavated a partial Diplodocus, and also cherry-picked a few extra bones from an adjacent specimen. The process of mounting the skeleton at USNM took six years of continuous work, and Gilmore would later describe it as the most ambitious undertaking his department hadever attempted. The 70-foot Diplodocus mount was completed in 1931, and remained unchanged for more than 80 years. It was finally taken down in December 2014, and will return in a new pose in 2019.

Addendum: Mike Taylor recently called attention to a gorgeous map of the entire deposit prepared by Ken Carpenter, which was what prompted this post. Check it out here.


Carpenter, K. (2013). History, Sedimentology, and Taphonomy of the Carnegie Quarry, Dinosaur National Monument, Utah. Annals of the Carnegie Museum 81:3:153-232.

Dingus, L. (1996). Next of Kin: Great Fossils at the American Museum of Natural History. New York, NY: Rizzoli International Publications, Inc.

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

McGinnis, H.J. (1982). Carnegie’s Dinosaurs: A Comprehensive Guide to Dinosaur Hall at Carnegie Museum of Natural History, Carnegie Institute. Pittsburgh, PA: The Board of Trustees, Carnegie Institute.


Filed under AMNH, CMNH, collections, dinosaurs, DMNS, exhibits, field work, fossil mounts, history of science, museums, NMNH, ornithopods, sauropods, theropods, thyreophorans

Framing Fossil Exhibits: Phylogeny

This is the third part of an on-again, off-again series about organizational and interpretive approaches in large-scale paleontology exhibits (see the introduction and walk through time entries). This time, I’ll be discussing exhibits arranged according to phylogenetics – that is, the evolutionary relationships among living things. Natural history museums have displayed specimens according to their place on the tree of life since the days of Charles Wilson Peale, and more than any other organizational scheme, phylogeny is the way biologists think about the living world. Perhaps unsurprisingly, this arrangement was more common in the past, when exhibits were typically designed by and for experts. Examples of these old-school displays include the fossil mammal gallery at the Peabody Museum of Natural History and the paleontology halls at the University of Kansas Natural History Museum (neither has been thoroughly overhauled since the 1950s).

peabody mammals

The jargon-heavy signage in the Peabody Museum’s classic fossil mammal exhibit is probably ignored by most visitors. Photo by the author.

Modern natural history museums rarely attempt phylogenetic exhibits. In vertebrate paleontology, an understanding of the evolutionary relationships of animals as identified via minute anatomical details is fundamental to our science. However, most people simply don’t think about the world in this way. For example, I was halfway through my first semester teaching an undergraduate anatomy course when I realized that most of the class didn’t really understand what a mammal is. The students were familiar with the word “mammal” and could provide some examples, but they couldn’t articulate what sets mammals apart from other animals, and the relationship of mammals to other vertebrates within the tree of life was all new to them. It’s easy to forget that even the most basic elements of evolutionary classification are specialized knowledge, even among biology students.

Describing the history of life on Earth chronologically is relatively easy – museum visitors intuitively understand the forward progression of time. But scientific classification (as opposed to colloquial categorization) requires a lot of explanation up front, and it’s easy to overwhelm an audience with jargon. While not impossible (see Neil Shubin’s masterful Your Inner Fish), it is very difficult to explain phylogeny to a general audience in a relatable and approachable way.

In 1995, the American Museum of Natural History attempted to do just that with the most recent renovation of its historic 4th floor fossil halls. This evolutionary arrangement was a major change for AMNH, since this space had a “walk through time” layout for most of the 20th century. In the accompanying book Discovering Dinosaurs in the American Museum of Natural History, curators Norell, Gaffney, and Dingus explain that phylogenetics (and the cladistic methodology in particular) is the only way to approach the study of prehistoric life in an objective way. Patterns of evolutionary relationships revealed by cladistic analyses are hard evidence in a field of study traditionally characterized by idle speculation. Norell and colleagues argue that the new exhibit arrangement shows visitors the credibility and scientific rigor behind modern paleontology.

4th floor of AMNH.

Map of the fossil halls on the 4th floor of AMNH. Source

Communicating the rigorous and trustworthy nature of scientific conclusions is a worthy goal, and the choice to ground the AMNH exhibit in this way seems almost prophetic given the litany of speculation-heavy paleontology “documentaries” that have proliferated in the years since it opened. Scientific rigor is definitely a running theme here – sign after sign explains that popularly depicted dinosaur behaviors like parental care and pack-hunting are largely untestable speculation. To a degree, this label copy takes the fun out of an undeniably fun subject, but I can appreciate the effort to legitimize paleontological science in the public eye. Overall, the AMNH exhibits represent an attempt to train visitors to look at fossils the way scientists do, and the phylogenetic layout is central to that goal.

In the exhibit, visitors are meant to walk through a cladogram of chordates. You’ll pass through large halls dedicated to broad groups like saurischian dinosaurs and advanced mammals, while visiting smaller cul-de-sacs that  represent narrower clades like ornithomimids and testudines. A central black path guides you through the evolution of life, and centrally-situated pillars along your route identify major evolutionary innovations, such as jaws or the ability to reproduce on land. The insanely comprehensive vertebrate fossil collections at AMNH make this institution uniquely capable of putting so much diversity on display (although non-tetrapods are woefully underrepresented). Meanwhile, an open floor plan allows you to spend as much or as little time in each area as you wish, and ample natural lighting goes a long way toward making it possible to study specimens in detail.

follow the path for now

Pillars mark major evolutionary milestones in the Hall of Vertebrate Origins. Photo by the author.

path disappears among dinosaurs

The evolutionary pathway becomes considerably less obvious among the dinosaurs. Photo by the author.

Nevertheless, I agree with Brian Switek that the AMNH fossil halls don’t do the best job communicating the story of vertebrate evolution to their core audience. The underlying purpose of any exhibit structure is to provide meaning and context for objects – to help visitors see them as more than neat things to look at. According to visitor surveys, the default mode of understanding for most people passing through a paleontology exhibit is what I’ve been calling “dinosaur pageantry.” After seeing the exhibit, most visitors will recall a list of cool skeletons they saw. A few might consider which ones are meat-eaters and which ones are plant-eaters, but without further prompting that’s all we can usually expect from non-specialists. It’s the museum’s job to give visitors the intellectual tools to contextualize those fossils in a more sophisticated way, but there’s a fine line to walk. Provide too little information and nobody learns anything, but provide too much and the content is ignored. Unfortunately, the AMNH exhibits fall into the “overkill” category.

As discussed, phylogeny is complicated, often counter-intuitive, and largely unfamiliar to many visitors. To overcome this, the AMNH designers rely on a fairly long orientation film, which introduces the concept of categorizing organisms based on shared derived characteristics. There are a few problems with this. First there’s the film itself, which dives right into the traits that characterize different groups – like the stirrup-shaped stapes of derived mammals and the temporal fenestrae of archosaurs – without explaining why these traits are significant. To a layperson, these probably seem like really inconsequential things to hang a whole group on. The video also presents a cladogram of vertebrates without explaining how to read it. As Torrens and Barahona demonstrate, interpreting a phylogenetic tree is a specialized skill that many natural history museum visitors lack. Second, I saw no incentive or instruction to actually start my visit to the 4th floor in the orientation hall. There are no less than four entrances to the fossil exhibits, so many visitors won’t know there is an orientation film (I sure didn’t) until they’re halfway through the galleries. Finally, there’s the reliance on media in general: do we really want visitors to spend even a portion of their time in an exhibit full of real fossils watching a video in a darkened room? Telling visitors what to think in a narrated video is easy, but it’s not nearly as meaningful as showing them the same concept with specimens (or better yet, coaxing them to reach conclusions themselves).

Hall of Saurischian Dinosaurs, American Museum of Natural History. Photo by the author.

Iconic mounts in the Hall of Saurischian Dinosaurs are iconic. Photo by the author.

Within the actual fossil halls, interpretation remains stubbornly unapproachable. For example, the sign introducing proboscidians tells visitors that this group is defined primarily by eye sockets located near the snout. An observant visitor might wonder why scientists rely on such an obscure detail, as opposed to the obvious trunks and tusks. There’s a good teaching moment there concerning why some characteristics might face more selection pressure (and thus change more radically) than others, but instead visitors are only offered esoteric statements. Relatedly, the exhibit does little to prioritize information. Most label text is quite small, and there’s a lot of it. Compare this to Evolving Planet at the Field Museum, where there is a clear hierarchy of headings and sub-headings. Visitors can read the main point of a display without even stopping, and parents can quickly find relevant information to answer their charges’ questions (rather than making something up).

Evolving Planet also compares favorably to the AMNH fossil halls in its informative aesthetics and spatial logic. At FMNH, walls and signs in each section are distinctly color-coded, making transitions obvious and intuitive. Likewise, consistent iconography  – such as the mass extinction zones – helps visitors match recurring themes and topics throughout the exhibit. AMNH, in contrast, has a uniform glass and white-walled Apple Store aesthetic. It’s visually appealing, but doesn’t do much to help visitors navigate the space in a meaningful way.

edentates aren't real

Phylogenetic interpretations change quickly – Edentata is no longer considered a natural group. Photo by the author.

The phylogenetic layout introduces a number of other unique interpretive challenges. Since there is no temporal axis,  it’s often unclear whether the lineage in a particular cul-de-sac cluster went extinct, continued on, or gave rise to another group elsewhere in the exhibit. Visitors that want to know which animals lived contemporaneously are out of luck. Meanwhile, the exhibit sometimes uses modern animal skeletons to fill out displays where fossil examples are limited, such as bats and primates. While these are labeled, the text is too small to be seen from a distance. The evolutionary organization is also burdened by the fact that phylogenetics is a fast-moving and often changing field of study. While the order of geologic time periods will never change, the 20 year-old displays at AMNH are already out of date in several details. For example, there is a cul-de-sac devoted to edentates, which is now considered polyphyletic, and a cladogram in the Hall of Saurischian Dinosaurs incorrectly places tyrannosaurids among the carnosaurs.

Cows and broken videos

Glass architecture lets visitors see through displays and get a sense of what lies beyond. Photo by the author.

Neat comparison of mammal teeth. Too bad there's no obvious label.

This display is a great example of the diversity in mammal teeth, but it’s a confusing centerpiece for the Hall of Primitive Mammals. Photo by the author.

The AMNH fossil exhibits excel in many respects, chiefly in the amazing diversity and quantity of specimens on display. The exhibit throws a lot of good science at visitors, but falters in explaining why it matters. The point of all this is not to nit-pick the design choices at AMNH, but to reiterate that phylogenetically-arranged fossil exhibits are really hard to pull off. This is not the most intuitive way to introduce the history of life, or even the process of evolution. With so much background to cover, perhaps a more structured and linear layout would be better. In fact, a lot of my issues with the AMNH fossil exhibits seem to stem from a disconnect between the phylogenetic interpretive content and the wide-open aesthetics. Open exhibits can be great, but in this case it hinders the learning opportunities for self-guided groups of visitors. It’s difficult to imagine a typical visitor, arriving with their family or another mixed-age group, having the patience to make sense of it all. Regrettably, such visitors default to the dinosaur pageantry level of understanding, making all the work invested in creating a meaningful exhibit space for naught.


Norell, M, Gaffney, E, and Dingus, L. (1995). Discovering Dinosaurs in the American Museum of Natural History. New York, NY: Alfred A. Knopf, Inc.

Torrens, E. and Barahona, A. (2012). Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted? Evolution: Education and Outreach 1-25.


Filed under AMNH, dinosaurs, exhibits, fish, FMNH, fossil mounts, mammals, museums, opinion, reptiles, reviews, systematics

Dinosaurs on display in 2014

Instead of repeating last year’s navel-gazing, I’m going to try something a little more interesting with my obligatory year-in-review*. This post will recap 2014’s big events in museum paleontology – I’ve covered some of it before, but there’s plenty that I missed as well.

Out with the Old

artists conception

Concept art for the new NMNH fossil hall, opening 2019.

I don’t think it’s a stretch to say that the most important event in the world of fossil exhibits this year was the closing of the National Museum of Natural History’s east wing. This is the world’s most-visited natural history museum, and the fossil mounts on display here have been among the most widely-viewed anywhere. The east wing has been home to paleontology displays since the building opened more than a century ago, but until now it has never undergone a complete, wall-to-wall modernization. Since the halls closed in April, NMNH staff have made significant progress de-installing the old displays, including some mounted skeletons that have been on display for over 80 years. Over the next five years, this historic space will be restored to it’s original neo-classical glory, and eventually remade into a new chronicle of the history of life on Earth suitable for the 21st century.

NMNH was among the last of the classic American natural history museums to commit to a post-dinosaur renaissance overhaul (the American Museum of Natural History started the trend in 1995, followed by the Field Museum and the Carnegie Museum). All eyes are now on the Peabody Museum of Natural History, where the great hall of fossil reptiles still looks much as it did sixty years ago. A plan is in place for a $30 million renovation, and the museum is currently soliciting donations to fund the project. For now, however, New Haven is one of the last places in North America where visitors can still see early-20th century dinosaur mounts.

In With the New


Spinosaurus at the National Geographic Explorer’s Hall. Photo by the author.

Several new temporary and traveling fossil exhibits opened in the United States this year. The biggest splash was made by “Spinosaurus: Lost Giant of the Cretaceous”, which I reviewed in September. Premiering at the National Geographic Explorer’s Hall in Washington DC, this exhibit is science outreach on a grand scale. It debuted alongside a technical paper by Nizar Ibrahim and colleagues that redescribed the well-known Spinosaurus as a short-legged analogue to early whales. While there has been some skepticism about the paper’s conclusions, credit must be given for such an ambitious public display of up-to-the-minute research. The exhibit, which includes a 50-foot reconstruction of a swimming Spinosaurus skeleton, will be on display in Washington through April 12. After that, it begins its world tour in Germany.

Washington, DC got a second new paleontology exhibit this Fall in the form of “The Last American Dinosaurs” at NMNH. Focusing on the North American ecosystem that existed just before the Cretaceous-Paleogene extinction event, this exhibit will serve as an interim dinosaur attraction while the main fossil hall is being renovated. The Last American Dinosaurs is more than a stopgap, however – it’s a remarkably well-crafted look at ecology and the phenomenon of extinction, both in the past and in the present.

Other 2014 fossil exhibits of note include “Tiny Titans: Dinosaur Eggs and Babies” at the Peabody Museum, and “Pterosaurs: Flight in the Age of Dinosaurs” at AMNH. Tiny Titans didn’t feature any show-stopping fossil mounts, but it was nevertheless a charming, kid-friendly exhibit focused on how different groups of dinosaurs raised their young. I thoroughly enjoyed it, particularly the gorgeous artwork by Luis Rey. I missed my chance to check out Pterosaurs (it closes this week), so if you were able to see it please share your thoughts!

Mount of the Year

Sophie the Stegosaurus at the Natural History Museum in London. Source

Sophie the Stegosaurus at the Natural History Museum in London. Source

What was the coolest mounted fossil skeleton created this year? For the runner up, I’d pick the aforementioned Spinosaurus. Created by RCI and Acme Design under the direction of Paul Sereno’s lab at the University of Chicago, this replica skeleton embodies both the possibilities and pitfalls of digital technology. The Spinosaurus mount is based on a digital composite of laser-scanned fossils held in at least three countries, as well as scaled-up bones from related animals like Suchomimus, and a fair amount of sculpted material. On one hand, it’s incredible that a unified vision of this animal can be willed into three-dimensional existence. However, one could reasonably voice concern about presenting a somewhat controversial hypothesis in a format that implies authenticity. Virtually all fossil mounts are composites to some degree, but it seems we’re still working out the limits of how far this concept can be taken.

In contrast, I have no reservations in granting Mount of the Year to Sophie the Stegosaurus. Unveiled on December 4th at London’s Natural History Museum, this is the most complete Stegosaurus specimen known and the first example of this species to be displayed in Europe. It’s also the first new dinosaur skeleton to be added to historic NHM exhibit halls in more than a century. After the museum purchased the skeleton from a private dealer in 2013, Paul Barrett and Charlotte Brassey have been carefully examining (and laser-scanning) every inch of it for the better part of the last year. New data on the biomechanics and behavior of Stegosaurus is due out soon, but for now the public can enjoy the 18-foot skeleton in a dramatic display at the museum. In addition to the impressive work creating a dynamic pose with nearly invisible supports, I’m particularly taken by NHM’s outreach efforts, which explain the importance of this skeleton for a broad range of audiences.

All in all, 2014 was a pretty good year for paleontology on display. While fossil exhibits remained stagnant for much of the 20th century, the last decade plus has seen an explosion of displays to feed the public’s insatiable appetite for dinosaurs. Perhaps in the future we will call this time the second golden age of fossil mounts!

*For the record, Dinosours! got about 26,000 visitors last year, many of which I owe to the good people at Love in the Time of Chasmosaurs and SV-POW. My review of the Spinosaurus exhibit was by far the most popular post, followed by the two-parter on Triceratops posture and the true story of the mismatched “Brontosaurus” skull.


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Filed under AMNH, dinosaurs, exhibits, fossil mounts, museums, NMNH, opinion, theropods, thyreophorans

Displaying the Tyrant King – Part 2

Old meets new

Old meets new: The classic Carnegie T. rex (CM 9380) is now paired with a cast of Peck’s Rex (MOR 980). Photo by the author.

Start with Displaying the Tyrant King – Part 1.

In 1915, the American Museum of Natural History unveiled the first mounted skeleton of Tyrannosaurus rex ever constructed. The Carnegie Museum of Natural History followed suit with their Tyrannosaurus mount in 1941, and for most of the 20th century New York and Pittsburgh were the only places in the world where the tyrant king could be seen in person. Nevertheless, these displays propelled Tyrannosaurus to universal stardom, and the instantly recognizable dinosaur appeared in countless books, films, and other media for years to come.

The omnipresence of T. rex was secured in part by two additional museum displays, ironically at institutions that did not have any actual Tyrannosaurus fossils on hand. The Field Museum of Natural History commissioned Charles Knight to paint a series of prehistoric landscapes in 1928, the most recognizable of which depicts a face-off between Triceratops and a surprisingly spry Tyrannosaurus. In 1947, Rudolph Zallinger painted a considerably more bloated and lethargic T. rex as part of his Age of Reptiles mural at the Peabody Museum of Natural History. Both paintings would be endlessly replicated for decades, and would go on to define the prehistoric predator in the public imagination.

Rex Renaissance

Despite enduring public enthusiasm, scientific interest in dinosaurs declined sharply in the mid-20th century, and new discoveries were few and far between. This changed rather suddenly with the onset of the “dinosaur renaissance” in the 1970s and 80s, which brought renewed energy to the discipline in the wake of evidence that dinosaurs had been energetic and socially sophisticated animals. The next generation of paleontologists endeavored to look at fossils in new ways to understand dinosaur behavior, biomechanics, ontogeny, and ecology. Tyrannosaurus was central to the new wave of research, and has been the subject of hundreds of scientific papers since 1980. More interest brought more fossil hunters into the American west, leading to an unprecedented expansion in known Tyrannosaurus fossils. Once considered vanishingly rare, Tyrannosaurus is now known from over 50 individual specimens across a wide range of ages and sizes. Extensive research on growth rate, cellular structure, sexual dimorphism, speed, and energetics, to name but a few topics, has turned T. rex into a veritable model organism among dinosaurs.

RTMP 81.6.1, aka Black Beauty, mounted in relief at the Royal Tyrell Museum. Source.

RTMP 81.6.1, aka Black Beauty, mounted in relief at the Royal Tyrell Museum. Source

The most celebrated Tyrannosaurus find from the early years of the dinosaur renaissance came from Alberta, making it the northernmost and westernmost T. rex to date. The 30% complete “Black Beauty” specimen, so named for the black luster of the fossilized bones, was found in 1980 by a high school student and was excavated by paleontologist Phil Curie. The original Black Beauty fossils were taken on a tour of Asia before finding a permanent home at the newly established Royal Tyrell Museum in Drumheller, Alberta. In lieu of a standing mount, Black Beauty was embedded in a faux sandstone facade, mirroring the environment in which the fossils were found and the animal’s presumed death pose. This relief mount set Black Beauty apart from its AMNH and CMNH predecessors, and even today it remains one of the most visually striking Tyrannosaurus displays.  Since the original specimen consisted of less than half of a skeleton, much of this display is made up of sculpted bones, including the pelvis, scapula, and most of the ribs. The mounted skull is a cast, but the real skull is displayed behind glass nearby. A complete cast of Black Beauty in a traditional free-standing mount is also on display at the Swedish Museum of Natural History in Stockholm.

The World’s Most Replicated Dinosaur

Driven by the increased public demand for dinosaurs, many museums without Tyrannosaurus fossils of their own have purchased complete casts from other institutions. In 1986, the Academy of Natural Sciences in Philadelphia opened “Discovering Dinosaurs”, the world’s first major exhibit showcasing active, endothermic dinosaurs. The centerpiece of the exhibit was a cast of the original AMNH Tyrannosaurus, posed for the first time in the horizontal posture that we now know was the animal’s habitual stance. The following year, another AMNH cast appeared in the lobby of Denver Museum of Nature and Science in a strikingly bizarre pose, with one leg kicking high in the air. The mount’s designer Robert Bakker intended to push boundaries and demonstrate what a dynamic and energetic Tyrannosaurus might be capable of, although the mount has subsequently been described as dancing, kicking a soccer ball, or peeing on a fire hydrant. Meanwhile, The Royal Tyrell Museum prepared a mount of RTMP.81.12.1 (a specimen consisting of a relatively small number of postcranial bones) that was filled in with AMNH casts, including the highly recognizable skull.


Tyrannosaurus cast at the Denver Museum of Nature and Science. Source

Since the late 1990s, however, casts of another specimen have overtaken AMNH 5027 for the title of most ubiquitous T. rex. BHI 3033, more commonly known as Stan, was excavated in South Dakota in 1992 by the Black Hills Institute, a for-profit outfit specializing in excavating, preparing, and mounting fossils. Stan is significant for being over two-thirds complete and for including the best-preserved Tyrannosaurus skull yet found. BHI has sold dozens of casts of the Stan skeleton to museums and other venues around the world. At a relatively affordable $100,000 plus shipping, even small local museums and the occasional wealthy individual can now own a Tyrannosaurus mount. With over 50 casts sold as of 2017, Stan is, by a wide margin, the most duplicated and most exhibited dinosaur in the world.

Stan the Tyrannosaurus at the National Museum of Natural History. Photo by the author.

Stan the Tyrannosaurus at the National Museum of Natural History. Photo by the author.

All these new Tyrannosaurus mounts are forcing museums to get creative, whether they are displaying casts or original fossils. Predator-prey pairings are a popular display choice: for example, the Houston Museum of Natural Science T. rex is positioned alongside an armored Denversaurus, and the Los Angeles Natural History Museum matches the tyrant dinosaur with its eternal enemy, Triceratops. Meanwhile, the growing number of juvenile Tyrannosaurus specimens has allowed for family group displays. A second T. rex exhibit at LACM features an adult, subadult and baby, while the Children’s Museum of Indianapolis pairs a Stan cast with the original skeleton of Bucky, a “teenage” T. rex. The most unique Tyrannosaurus mount so far is certainly the copulating pair at the Jurassic Museum of Asturias.

Tyrannosaurus versus Denversaurus at the Houston Museum of Nature and Science. Photo by the author.

Each of these displays gives a substantially different impression of Tyrannosaurus. Depending on the mount, visitors might see T. rex as a powerful brute, a fast and agile hunter, or a nurturing parent (or a gentle lover). Each mount is accurate insofar that a real Tyrannosaurus probably adopted a similar stance at some point, but the museum’s choice of pose nevertheless influences visitors’ understanding of and attitude toward the dinosaur.

Restoring the Classics

With dozens of new Tyrannosaurus mounts springing up across the country and around the world, the original AMNH and CMNH displays began to look increasingly obsolete. Unfortunately, modernizing historic fossil mounts is an extremely complex and expensive process. The early 20th century technicians that built these displays generally intended for them to be permanent: bolts were drilled directly into the bones and gaps were sealed with plaster that can only be removed by manually chipping it away. What’s more, the cumulative effects of rusting armatures, fluctuating humidity, and vibration from passing crowds have considerably damaged historic mounts over the course of their decades on display.

AMNH 5027 was restored and remounted in 1995.

AMNH 5027 was restored and remounted in 1995. Photo by the author.

Despite these challenges, AMNH and CMNH have both been able to restore and update their classic Tyrannosaurus displays. While fossil mounts used to be built in-house, often by the same people who found and described those fossils, modern mounting projects are typically outsourced to specialist companies. Phil Fraley Productions, an exhibit fabrication company based in the Pittsburgh suburbs, was responsible for both T. rex restorations. At AMNH, Jeanne Kelly spent two years disarticulating and conserving each bone before Phil Fraley’s crew took over to build the new armature. The new mount not only corrected the dinosaur’s posture, but improved visitors’ view of the fossils by removing obstructive vertical supports. Instead, most of the skeleton’s weight is now supported by steel cables hanging from the ceiling.  Each bone is secured to an individual metal bracket, allowing researchers to easily remove elements for study as necessary. A new cast of the skull was also prepared, this time with open fenestrae for a more natural appearance. Rather than attempting to match the dramatic and showy T. rex mounts at other museums, the AMNH team chose a comparatively subdued stalking pose. A closed mouth and subtly raised left foot convey a quiet dignity befitting this historically significant display.

Historically, the 1941 CMNH Tyrannosaurus had never quite lived up to its New York predecessor. Although it incorporated the Tyrannosaurus type specimen, it was mostly composed of casts from the New York skeleton, and it sported an unfortunately crude replica skull. It is therefore ironic that CMNH now exhibits the more spectacular T. rex display, one which finally realizes Osborn’s ambitious plan to construct an epic confrontation between two of the giant predators. As they had with the AMNH mount, Phil Fraley’s team dismantled the original display and painstakingly removed many layers of paint, shellac, and plaster from the bones. Michael Holland contributed a new restored skull, actually a composite of several Tyrannosaurus skulls. The restored holotype T. rex now faces off with a cast of “Peck’s Rex”, a specimen recovered from Montana in 1997. Despite the difficulty of modernizing the historic specimen, the team reportedly developed a healthy respect for turn of the century mount-makers like Adam Hermann and Arthur Coggeshall, who developed the techniques for making enduring displays of fragile fossils that are still being refined today.

Continue to Displaying the Tyrant King Part 3.


Colbert, E.H., Gillette, D.D. and Molnar, R.N. “North American Dinosaur Hunters.” The Complete Dinosaur, Second Edition. Brett-Surman, M.K., Holtz, T.R. and Farlow, J.O., eds.Bloomington, IN: Indiana University Press.

Dingus, L. 1996. Next of Kin: Great Fossils at the American Museum of Natural History. New York, NY: Rizzoli International Publications, Inc.

Johnson, K. and Stucky, R.K. 2013. “Paleontology: Discovering the Ancient History of the American West.” Denver Museum of Nature and Science Annals, No. 4.

Larson, N. 2008. “One Hundred Years of Tyrannosaurus rex: The Skeletons.” Tyrannosaurus rex, The Tyrant King. Larson, Peter and Carpenter, Kenneth, eds. Bloomington, IN: Indiana University Press.

Naish, D. 2009. The Great Dinosaur Discoveries. Berkeley, CA: University of California Press.

Norell, M., Gaffney, E.S. and Dingus, L. 1995. Discovering Dinosaurs: Evolution, Extinction, and the Lessons of Prehistory.  Berkeley, CA: University of California Press.

Psihoyos, L. 1994. Hunting Dinosaurs. New York, NY: Random House, Inc.


Filed under AMNH, CMNH, dinosaurs, fossil mounts, history of science, museums, NMNH, paleoart, reptiles, theropods

What’s the deal with Astrodon?

In Laurel, Maryland, a trail of banners depicting a herd of the sauropod dinosaur Astrodon johnstoni leads the way to Dinosaur Park, the site of a historically significant fossil deposit. At the Maryland Science Center in Baltimore, a life-sized Astrodon sculpture towers over the “Dinosaur Mysteries” exhibit. And since 1998, Astrodon has been the official state dinosaur of Maryland, joining other state symbols like the black-eyed susan and Baltimore oriole. In short, Astrodon is a sort of mascot for mid-Atlantic paleontology. Named in 1858 for fossils found in a Prince George’s County iron mine, the appeal of Astrodon for Marylanders is obvious: it’s a home-grown dinosaur in a region that is not widely recognized for its fossil resources, and the story of its discovery also calls attention to the state’s industrial heritage.

But what sort of animal was Astrodon, and how much do paleontologists truly know about it? Compared to many other extinct animals found around the world, the fossil record for Astrodon is and always has been fairly poor. The name Astrodon was first bestowed upon nothing more than isolated teeth, and although other fragmentary remains attributed to Astrodon have been uncovered over the past 150 years, reconstructions of the Maryland sauropod are mostly derived from the fossils of relatives found elsewhere. What’s more, the name Astrodon has a convoluted history, having been applied haphazardly to fossils found across the country and even around the world. For these reasons, some paleontologists would prefer that the name Astrodon not be used at all.

Lacking a scientific consensus on what sort of animal the Maryland sauropod was or even what it should be called, I find myself in a difficult position as an educator. How can the messy and contentious taxonomy of Astrodon be condensed into something teachable? Is simplifying or downplaying this controversy doing our audience a disservice, and to what degree?

The taxonomic history of Astrodon

The first scientifically recognized North American dinosaur fossils were found in the Mid-Atlantic region, a scant 17 years after dinosaurs were first recognized as a biological group in 1842. Joseph Leidy’s Hadrosaurus from the New Jersey coast is credited as the first American dinosaur to be described, but Astrodon was a close second. During the mid-19th century, iron mining was big business in central Maryland. Miners extracted large boulders of siderite, or iron ore, from open pit mines throughout Prince George’s County, and these miners were the first in the region to discover dinosaur bones and teeth. The siderite was being mined from clay deposits now known as the Arundel Formation, part of the larger Potomac Group that extends throughout Maryland (the Potomac Group was laid down during the Early Cretaceous period, between 125 and 113 million years ago). Members of the Maryland Academy of Sciences recognized the fossils from the Arundel clay as similar to the English fossil reptiles that Richard Owen had recently unified as Dinosauria. In 1858, academy member Christopher Johnston published a description of a set of teeth from the iron mines in the American Journal of Dental Science, which he named “Astrodon” (Joseph Leidy turned this informal name into a proper binomial, Astrodon johnstoni, in his 1865 review of North American fossil reptiles).

Today, most paleontologists consider it poor judgment to name a new taxon based only on teeth. When scientists describe a newly discovered organism, they designate a type specimen, which is used to define that taxon in perpetuity. But when the type specimen is especially fragmentary, or only consists of a small part of the organism, it poses a problem for future researchers. In the case of Astrodon, no newly discovered fossils other than teeth can be confidently referred to the same species. In 1858, however, paleontological norms were very different. All dinosaur fossils known at the time were exceedingly incomplete: scientists knew that dinosaurs were reptiles and that they were very big and not much else. Any new fossils, even teeth, represented a major addition to our understanding of the life appearance and diversity of these extinct animals. For modern paleontologists, Johnston’s published description of the Astrodon teeth is vague and uninformative, but in his day, these fossils were distinct from anything else yet known.

Astrodon teeth lower left.

Astrodon teeth are on the lower left.

In December of 1887, famed paleontologist Othneil Charles Marsh sent his best fossil hunter, John Bell Hatcher, to search the area in Prince George’s County where Astrodon was discovered. Judging from Hatcher’s journal entries, he didn’t have a great time. It rained and snowed almost constantly, and on several days his team didn’t bother to show up for work. Although Hatcher managed to find numerous dinosaur, crocodile and turtle fossils, these finds did not match the quality of the fossils Hatcher had been finding in the western states, and no return trips were made. Nevertheless, Marsh saw fit to name two new dinosaur species from the material Hatcher collected: Pluerocoelus altus and Pluerocoelus nanus. Neither taxon was named for material that would be considered diagnostic if found today: P. altus was based on a tibia and fibula, while P. nanus was based on four nonadjacent vertebrae.

By this time, more complete dinosaur fossils from the American west were beginning to reveal a clearer picture of dinosaur diversity. Based on the shape and size of the fossils collected by Hatcher, Marsh determined that they belonged to sauropods, the group of long-necked herbivores that includes Diplodocus and Apatosaurus. More specifically, Marsh recognized that the Arundel sauropods were similar to “Morosaurus” (now called Camarasaurus) from Colorado. Today, the lineage of stocky, broad-nosed sauropods that includes Camarasaurus and its closest relatives are called macronarians. Unfortunately, by modern standards Marsh’s descriptions of P. altus and P. nanus are rudimentary in nature, and no distinguishing characteristics not common to all macronarian sauropods were offered.

Pleurocoelus elements. Image from NMNH Backyard Dinosaurs.

Pleurocoelus (or Astrodon?) fossils collected by Hatcher. Image from NMNH online exhibit Backyard Dinosaurs.

Contra Marsh, Hatcher suspected that there was only one sauropod in the Arundel Formation. P. altus and P. nanus were probably growth stages of one species, and the Astrodon teeth, now recognized as typical of macronarians, probably came from the same animal, as well. Since the International Code of Zoological Nomenclature decrees that the first published name given to a taxon has priority, Astrodon would take precedence over Pluerocoelus. Later, Charles Gilmore published a review of the Arundel fossils, in which he concurred with Hatcher that P. altus was a junior synonym of Astrodon, but retained P. nanus as a separate species.  

Then things started getting really complicated. While paleontologists were still debating how many sauropod species existed in the Arundel clay, Marsh and others had started naming lots of new species of Pluerocoelus. Fossils found in Texas, Oklahoma and even the U.K. were all thrown into the Pluerocoelus bucket, including P. montanusP. valdensisP. becklesii and P. suffosus. For much of the 20th century, Pluerocoelus was a classic wastebasket taxon, into which any and all sauropod fossils from early Cretaceous strata were casually thrown. Since the Pluerocoelus type specimens designated by Marsh were insufficient to define the taxon based on morphology, the name became little more than a temporal marker. Adding to the confusion, researchers continued to disagree over whether all these new Pluerocoelus species should be sunk into the earlier genus Astrodon.

In recent years, some progress has been made toward untangling this mess of early Cretaceous sauropods. There is a general consensus that fossils not found in Maryland’s Potomac Group differ substantially from the Arundel sauropods and should never have been referred to Pluerocoelus or Astrodon. New names have been proposed for the midwestern sauropods, including Astrophocaudia and Paluxysaurus. However, removing the non-Maryland fossils from the discussion merely returns us to the original set of problems: how many sauropods are represented in the Arundel clay, what were they like in life, and what should we call them?

Creating a coherent picture of Astrodon

Unfortunately, the answers to these questions depend on who you ask. The most thorough review of Arundel sauropods from the last decade was published by Kenneth Carpenter and Virginia Tidwell in 2005. Carpenter and Tidwell reaffirmed Hatcher’s conclusion that Pluerocoelus is synonymous with Astrodon, and that as the earliest published name, Astrodon has priority. This decision is apparently based only on the fact that the fossils came from the same stratum, however, since the Astrodon holotype cannot be compared to anything besides other teeth. For this reason, Michael D’Emic proposed in 2012 that the names Astrodon and Pluerocoelus are nomen dubia and should both be dropped entirely. Ultimately, neither solution is practical for identifying the sauropod fossils that continue to be collected from the Arundel Formation. Either we blindly refer any and all sauropod fossils to Astrodon, even though we lack a usable holotype, or we have no label available at all.  One solution would be to establish a new type specimen (called a neotype) for Astrodon, but this has yet to be done.

Both camarasaur and brachiosaur shaped Astrodon reconstructions are equally reasonable.

Both camarasaur and brachiosaur-shaped Astrodon reconstructions are reasonable. Artwork by Dmitry Bogdanov, via Wikipedia.

While many more sauropod fossils have been found in the Arundel clay since Hatcher’s 1887 expedition, we do not have enough material to fully elucidate what these animals looked like. Size estimates have varied enormously, from as little as 30 feet to as much as 80 feet in length. The assortment of fossil bones and teeth that have been found tell us we have a macronarian sauropod, and we can reconstruct its general shape based on more completely known relatives. However, macronarians were a fairly diverse bunch, ranging from the comparatively stocky camarasaurs to high-shouldered, elongate brachiosaurs. Carpenter and Tidwell describe the Arundel sauropod fossils, particularly the limb bones, as being fairly slender, but still more robust than those of Brachiosaurus. They do recognize, however, that nearly all known Arundel sauropod fossils come from juveniles, which may vary proportionally from adults. Because the precise affinities of Astrodon are unclear, artistic reconstructions vary substantially. The National Museum of Natural History’s Backyard Dinosaurs exhibit and website shows a camarasaur-shaped sauropod, while the life-sized sculpture at the Maryland Science Center is based on the brachiosaur Giraffatitan. At Dinosaur Park in Laurel, meanwhile, both versions are on display. More fossils, ideally cervical vertebrae or more complete adult material, are needed to clarify what the Arundel sauropod looked really like.

Teaching Astrodon

When I show people the teeth and partial bones attributed to Astrodon during public programs, I am almost always asked, “if that’s all you’ve found, how do you know what the whole animal looked like?”  As demonstrated by this post, it takes 1,700 words and counting to give a proper answer, which is too much for all but the most dedicated audiences. Nevertheless, to do anything less is to skip crucial caveats and information. Scientists are choosy about the words they use, filling explanations with “probablys” and “almost certainlys”, but they do so with good reason: when one’s job is to create and communicate knowledge, there is no room for ambiguity about what is and is not known. It is therefore just a bit dishonest to say that a large sauropod called Astrodon that was related to Brachiosaurus lived in Maryland, and yet I do so every week. How can I possibly sleep at night?

I’ll admit it can be difficult, but I get by because using one proviso-free name for the Maryland sauropod seems to be  informative and helpful to my audience. I only have people’s attention for so long, and I’d rather not spend that time on tangents about how Astrodon should really be called Pluerocoelus or why my use of either name is imprecise and problematic. I want visitors to walk away understanding how paleontologists assemble clues from sedimentary structures and anatomical comparisons to reconstruct ancient environments and their inhabitants. I’d like for visitors to practice making observations and drawing conclusions, and understand how paleontology is a meticulous science that can be relevant to their lives. “Paleontologists are weirdly obsessed with changing names” is not one of the most important things to know about paleontology.

Taxonomy, the science of naming and identifying living things, is unquestionably valuable. Biologists would be lost without the ability to differentiate among taxa. From my perspective, however, the public face of paleontology tends to overemphasize taxonomic debates in lieu of more informative discussions. There will always be somebody willing to argue whether Tarbosaurus bataar should be sunk into Tyrannosaurus, or to give incorrect explanations for why we lost “Brontosaurus.” In the end, though, these debates have more to do with people’s preferences than the actual biology of these animals. Astrodon may not be a diagnostic taxon in the strictest sense, but we need to call our fossils something, and taxonomic labels exist to be informative and useful. If asked, I’m always happy to provide the full story. But for the time being, Astrodon seems to be working just fine.


Carpenter, K. and Tidwell, V. 2005. Reassessment of the Early Cretaceous sauropod Astrodon johnstoni Leidy 1865 (Titanosauriformes). In Carpenter and Tidwell (eds.), Thunder-Lizards: The Sauropodomorph Dinosaurs. Bloomington, IA: Indiana University Press.

D’Emic M.D. 2012. Revision of the sauropod dinosaurs of the Lower Cretaceous Trinity Group, southern USA, with the description of a new genus. Journal of Systematic Paleontology, iFirst 2012, 1-20.

Gilmore, C.W. 1921. The fauna of the Arundel Formation of Maryland. Proceedings of the United States National Museum. 59: 581-594.

Kranz, P.M. Dinosaurs in Maryland. 1989. Published by Maryland Geological Survey, Department of Natural Resources, Educational Series No. 6.

Marsh, O.C. 1888. Notice of a New Genus of Sauropoda and Other New Dinosaurs from the Potomac Formation.

Please note that the usual disclaimer applies: views or opinions expressed here are mine, and do not reflect any institution with which I am affiliated.

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Filed under citizen science, Dinosaur Park, dinosaurs, field work, history of science, reviews, sauropods, systematics

Juan Bautista Bru and the First Fossil Mount

The first fossils ever assembled into a freestanding mount belonged to the giant ground sloth Megatherium. The fossils, which were unearthed near Luján in what is now Argentina, were described and mounted in 1795 by Juan Bautista Bru at the Royal Cabinet of Natural History in Madrid. But while the Megatherium mount played an important part in the history of paleontology and in our understanding of the changing Earth, the man who made it possible is scarcely mentioned in the literature. Instead, Bru’s work on Megatherium is typically overshadowed by the involvement of the much better known anatomist Georges Cuvier. Drawing principally from José López Piñero ‘s 1988 paper on Bru, this entry is intended to highlight and acknowledge Bru’s contribution to the practice of mounting fossils for public display.

Cuvier's adaptation of Bru's drawing.

Cuvier’s adaptation of Bru’s illustration of the Megatherium mount.

The Megatherium  in question was discovered  in 1789 in what was then the Viceroyalty of Rio de la Plata, on the banks of the Luján River, “a league and a half” from the town of the same name. As region was controlled by the Spanish monarchy at the time (although the Argentine War of Independence was not far off), it was standard procedure for viceroy Marqués de Lorento to ship the important find to Spain with all haste. Packed into seven crates, the nearly complete skeleton was delivered to the Royal Cabinet of Natural History in Madrid, which curated natural specimens from Spanish territories and was among the most respected scientific institutions in Europe.

By the late 1700s, the European Enlightenment was well established, and the pursuit of knowledge about the world through reason and scientific deduction rather than legend or dogma was popular among the societal elite. The study of natural history was deemed particularly important, and institutions like the Royal Cabinet which collected, quantified and published knowledge about the natural world were well-respected and well-funded. However, the meaning of the fossil record still eluded the top minds of the era. A century earlier, Nicolaus Steno had determined that fossils were the remains of once-living organisms, and by the late 1700s some naturalists were starting to come around to the idea that species that once existed had become extinct. Nevertheless, when the Megatherium arrived in Madrid, naturalists still lacked the most important part of the puzzle presented by the fossil record: an understanding of evolution and the interrelatedness of life on Earth.

The task of interpreting the Luján fossils went to Juan Bautista Bru, the “Artist and First Dissector” at the Royal Cabinet. Born in Valencia, Bru had initially tried his hand as a traditional artist, but found little success. After shifting his focus to natural science, Bru joined the Royal Cabinet in 1771 and remained there until his death in 1799. Bru primarily served as a scientific illustrator, combining his artistic skill with his extensive anatomical knowledge to produce gorgeously detailed drawings of biological specimens, as was required before photography became commonplace. He was also responsible for producing taxidermy pieces and occasionally, mounted skeletons of animals.  In 1777, Bru prepared and mounted the skeleton of an elephant that had died at the royal estate in Aranjuez, a task which doubtlessly provided useful practice for mounting the gigantic Megatherium.

Plate from Bru's monograph

Plate I from Bru’s Megatherium monograph.

Bru devoted four years to studying the Luján fossils, which were complete except for the animal’s tail. He completed his monograph in 1793, which included detailed descriptions of every skeletal element, in addition to 22 plates illustrating the bones from various angles. Among the illustrations was the completely articulated skeleton shown above, which is, incidentally, the first recorded instance of a skeletal drawing illustrating the living form of an extinct animal. Since the mounted skeleton did not go on display until 1795, it is unclear whether Bru based the illustration on the mount or vice versa. Unfortunately, little is known about how Bru created the Megatherium mount, and his drawing provides no information about the armature that supported the massive bones. Since Bru did not discuss the mount’s construction in his monograph, one can only surmise that the techniques he refined over the years building mounts of modern animal skeletons were applicable to the fossils. Wooden armatures were used to mount fossils in the early 1800s, and it is plausible that Bru pioneered this technique. Regardless of how it was supported, the  rhino-sized Megatherium mount was placed on a rectangular wooden platform in a room of the Royal Cabinet already devoted to fossils and minerals.

It is unclear why, but Bru never published his monograph, and this unfortunately resulted in him effectively being scooped by Georges Cuvier in 1796. A representative of the French government working in Santa Domingo acquired a set of proofs of Bru’s monograph and illustration, and passed them along to the Institut de France. The proofs made their way to Cuvier, who was well established as one of the world’s leading experts in anatomy and natural history. Although he had not yet seen the actual fossils, Cuvier wrote a brief article in the journal Magasin Encyclopedique on the South American creature, in which he coined the rather vague name Megatherium americanum, meaning American giant beast. Cuvier’s article was not without error (he claimed the fossils were found in Paraguay), but he did correctly recognize that the animal was an edentate* and was curiously similar to modern tree sloths**. In contrast, Bru’s description of the fossils, while thorough, contained no attempt at classification.

As it happened, Cuvier published a second important article on fossil animals in 1796: his Mémoires sur les espèces d’éléphants vivants et fossiles, in which he established that the mammoth fossils found in the Americas belonged to an extinct relative of modern elephants. The wave of attention Cuvier received that year for his contributions to the young field of paleontology apparently eclipsed any recognition of Bru’s multi-year study of the Megatherium. Bru ended up selling his monograph and illustrations to a publisher, and a translated version eventually appeared in a widely disseminated booklet with Cuvier’s Megatherium article in 1804, five years after Bru’s death.

Megatherium would continue to be important to 19th century paleontologists. Charles Darwin became interested in South American fossils during the second voyage of the HMS Beagle. In particular, the relationship between the extinct ground sloths and their modern relatives contributed to Darwin’s ideas about the succession of species over geologic time. In 1849, the British Museum produced a Megatherium mount of their own, a composite of two skeletons found very near to where the Spanish specimen was first discovered. Plaster casts of this mount would appear in museums on both sides of the Atlantic, and the original cast is still on display in London today (some of the fossils were destroyed during World War II). But while the discovery of Megatherium would be recounted often over the subsequent two centuries, it was Cuvier, not Bru, who was always given credit for introducing the animal to the world. Only in recent years has Bru’s name begun to circulate again in historical accounts.

The original Megatherium fossils have been remounted at the Museo Nacional de Ciencias Naturales. Image from TripAdvisor.

The original Megatherium fossils have been remounted at the Museo Nacional de Ciencias Naturales. Image from Virtual Tourist.

However, there is a bit of happiness at the end of this story. Unlike other early mounts like Peale’s mastodon and Hydrarchos, Bru’s Megatherium has survived to the present day. Remounted on a new steel armature in an approximation of the original quadrupedal pose, the Luján Megatherium fossils are on display at the Royal Cabinet’s spiritual successor, the National Museum of Natural Science in Madrid. On public display for a nearly uninterrupted 218 years, this specimen can  surely be said to have taken on a second life. It was once a giant beast that roamed across the ancient Argentinian plains, and now it is a monument to scientific achievement.

*Edentata is a historic paraphyletic group that includes sloths, anteaters, pangolins and aardvarks. Modern biologists recognize that the new world sloths and anteaters and old world pangolins and aardvarks are not closely related. The name Xenarthra is now used for sloths and their new world relatives.

**Cuvier was working many decades before Charles Darwin published On the Origin of Species, and as such, did not subscribe to the idea that species could change and diversify over time. It is therefore worth noting that while he recognized the similarity between Megatherium and modern sloths, he did not conceive of their relationship in an evolutionary sense (that is, related species sharing a common ancestor). 


Argot, C. (2008). Changing Views in Paleontology:
The Story of a Giant (Megatherium, Xenarthra). Mammalian Evolutionary Morphology. Pp 37-50.

López Piñero , J.M. (1988). Juan Bautista Bru (1740-1799) and the Description of the Genus Megatherium. Journal of the History of Biology. 21:1:147-163.

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Filed under fossil mounts, history of science, mammals, museums, paleoart