July 16, 2012 · 4:47 am

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

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July 11, 2012 · 8:56 am

Extinct Monsters: History of Smithsonian Fossil Exhibits

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

Upon his death in 1829, British scientist James Smithson left his fortune to the United States government to found “at Washington…an establishment for the increase and diffusion of knowledge.” Congress used Smithson’s estate to establish the publicly funded Smithsonian Institution in 1846, which has since grown into an expansive research institute and museum complex that is recognized the world over. Vertebrate paleontology has been an important part of the Smithsonian’s agenda since the beginning, and this article by Ray Rye provides a compelling history of the scientific staff and their research. This post will take a slightly different approach, summarizing the changing public face of Smithsonian paleontology in the form of its genre-defining exhibits.

In 1847, Joseph Henry, the Smithsonian’s first secretary, started construction on the original Smithsonian building, which today is colloquially known as “the castle.” The first vertebrate paleontology exhibit housed within its walls consisted of a trio of casted skeletons: the ground sloth Megatherium, the glyptodont Scistopleurum, and the tortoise Collossochelys. These exhibits were probably obtained through Ward’s Natural Science Establishment. The Smithsonian’s first skeletal mount made from original fossils was a Megaloceros, purchased from antiquities dealers Thomas and Sons in 1872.

Exhibits like this one at USNM were deemed incomprehensible and inspired early reform

Basilosaurus, Megatherium, and Megaloceros are visible in the southwest court of the first United States National Museum. Image courtesy of the Smithsonian Institution Archives.

1881 saw the completion of the original United States National Museum, next door to the castle (this structure is now called the Arts and Industries Building). The southwest court was dedicated to osteology and paleontology, and the existing skeletal mounts were placed here among rows of cases containing smaller specimens. At this point in time, the Smithsonian had very few permanent staff members, instead relying mostly on scholars serving in unpaid “honorary” positions to curate the growing national collection. Famed paleontologist O.C. Marsh (the beardier half of the “bone wars” rivals) was the honorary curator of vertebrate paleontology. Under contract with the United States Geological Survey, Marsh supervised numerous field expeditions to the American west and oversaw the collection of untold thousands of fossil specimens. When Marsh died in 1899 the fossils he collected for the government were relocated from Yale University (his home institution) to the Smithsonian.

Gilmore and the Hall of Extinct Monsters

Gilmore with Diplodocus vertebrae.

C.W. Gilmore with some Diplodocus vertebrae. Image courtesy of the Smithsonian Institution Archives.

Charles Whitney Gilmore was a student in mine engineering at the University of Wyoming when he became involved in the Carnegie Museum’s fossil hunting expeditions in 1899. Recognizing the young man’s enthusiasm and talent, John Bell Hatcher hired Gilmore immediately after his graduation in 1901. Gilmore worked with Hatcher for two field seasons, but in 1903 he moved to Washington, DC upon being offered a position as a full-time preparator at the USNM. He was promoted to Curator of Vertebrate Paleontology in 1924, and is fondly remembered as an exceptionally modest but extraordinarily productive scientist. As curator, Gilmore led sixteen fossil-hunting expeditions to the western interior. Gilmore’s most enduring contribution to paleontology, however, is his extensive body of descriptive publications on the Marsh fossils. His monographs on Apatosaurus, Camarasaurus, Ceratosaurus, and many others are still regularly cited today.

Along with preparators Norman Boss and James Gidley, Gilmore is responsible for creating most of the mounted dinosaur skeletons that are on display at the Smithsonian. The first dinosaur mount Gilmore and his team completed was Edmontosaurus, which went on display in the original USNM building in 1904. Gilmore would go on to supervise the construction of Triceratops (the first mount of this taxon in the world), Camptosaurus, Stegosaurus, Dimetrodon, Ceratosaurus, Diplodocus, and numerous other displays that have been enjoyed by generations of museum visitors.

extinctmonstersfront_1913

The Hall of Extinct Monsters, sometime before 1929. Image courtesy of the Smithsonian Institution Archives.

Congress authorized the construction of a new United States National Museum on the north side of the National Mall in 1911. In contrast to the Victorian style of the original building, the new museum sported neoclassical granite construction which matched the aesthetic of the other federal buildings. Exactly when the museum opened is the subject of some debate. Collections and offices began moving across the mall via horse and wagon in 1908, and part of the first floor opened to the public on March 17th, 1910. Nevertheless, it was not until 1911 that all the exhibit spaces were ready for visitors, including the evocatively titled “Hall of Extinct Monsters” in the museum’s east wing. This cavernous space devoted to fossil displays was primarily under Gilmore’s stewardship, and generally resembled a classic “cabinet of curiosity” approach to exhibit design. Gilmore and his team would gradually fill the Hall of Extinct Monsters will new specimens over the coming decades, culminating in the towering Diplodocus mount completed in 1932.

Modernization and Renaissance

Gilmore retired in 1945, and vertebrate paleontology research at the USNM, particularly in dinosaurs, quieted in his absence. Charles Gazin, Gilmore’s successor as Curator of Vertebrate Paleontology, specialized in mammals, and the museum remained without a curator specializing in dinosaurs until Matt Carrano was hired in 2003. In 1957, the USNM split into two subdivisions, the Museum of Natural History and the Museum of History and Technology. The Smithsonian’s history collections were moved to a new building next door, now called the National Museum of American History, and other collections gradually dispersed into 20-some other Smithsonian museums. The site of the disbanded USNM was officially renamed the National Museum of Natural History in 1967, and remains the home of natural sciences and anthropology.

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

The Hall of Fossil Reptiles lasted from 1962 to 1981. Image courtesy of the Smithsonian Institution Archives.

The Hall of Extinct Monsters persisted largely unchanged until 1962, when it was finally renovated as part of a Smithsonian-wide modernization project. The fossil exhibits were among the last to be updated, in part due to ambivalence from the paleontology curators. The department did not employ any staff members exclusively devoted to exhibit work, so the task of reinventing the displays was an added burden for the research staff. As such, the changes to the hall ended up being more cosmetic than structural. The largest mount, Gilmore’s Diplodocus, was too difficult to disassemble and move, so the new exhibit was designed around it. Solid earth tones and wall-to-wall carpet replaced the original neoclassical aesthetic. The John Elliot mural Diana of the Tides, positioned high on the east wall, was simply boarded over during construction (and has remained so ever since).

The 1981 renovation saw the addition of a mezzanine over the dinosaur exhibit. Source

In 1974, the addition of the Hall of Ice Age Mammals and the Rise of Man expanded the paleontology display space beyond the east wing. Further renovations took place in three stages starting in 1979. Entitled “Fossils: The History of Life”, the overhauled exhibit complex represented a significant departure from earlier iterations of this space. While the previous renovation arranged specimens according to taxonomy and curatorial specialties, “The History of Life” followed the evolutionary progression of fossil plants and animals through time. The new exhibits also differed from prior efforts in that they were not put together exclusively by curators. Instead, the design process was led by educators and exhibits specialists, who sought curatorial input at all stages. The new specimens and displays also required the once spacious hall to be carved up into a maze of small rooms and narrow corridors. Even with the additional floor space provided by a new balcony over the dinosaurs, the east wing had become quite crowded.

Of course, the science of paleontology has advanced by leaps and bounds since the 1980s, and NMNH staff have made piecemeal updates to the exhibits when possible. These changes include restorations of deteriorating mounts, the addition of a cast of Stan the Tyrannosaurus, and a few revised signs addressing the dinosaurian origin of birds and new dates for geologic time periods. Still, the east wing remained largely the same for over 30 years, and began to look a bit tired next to the brand-new exhibits that have opened at NMNH over the last decade.

Looking Ahead

The NMNH fossil halls closed on April 27th, 2014 for a five year renovation project. For the first time, the east wing was completely gutted and its underlying infrastructure overhauled. Aging specimens like the 1932 Diplodocus and the 1911 Ceratosaurus were be painstakingly disassembled and conserved, and the space itself was restored to its original Beaux Arts splendor. The re-imagined exhibit is arranged in reverse chronological order: visitors  start among mammoths and ground sloths in the Pleistocene and move backward in time through increasingly alien-looking versions of North America. Unlike the present exhibit, however, an open floor plan will allow visitors to get a sense of what they’re in for from the moment they walk into the hall.

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Mesozoic section of the new Hall of Fossils – Deep Time. Concept art on display in the Last American Dinosaurs exhibit at NMNH.

The overall theme is change over geologic time, highlighting the myriad ways that climate, geography, evolution, and other living and nonliving systems interact and shape the world’s environments. Not all the classic mounts will make it into the new space (Brachyceratops, Zygorhiza, and Stegomastodon are among the retirees), but there are many new additions, including the Nation’s T. rex.  The result will be a compelling mix of classic early 20th century museum aesthetics and modern visitor-focused educational strategies.

References

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 No. 90.

Rye, R. (2002.) History of the NMNH Paleobiology Department. http://paleobiology.si.edu/history/rye.html

Sues, H. and Marsh, D. (2013). Charles Whitney Gilmore: The Forgotten Dinosaur Hunter. http://paleobiology.si.edu/history/gilmore.html

Yochelson, E.L. (1985). The National Museum of Natural History: 75 Years in the Natural History Building. Washington, DC: Smithsonian Institution Press.

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Filed under collections, dinosaurs, exhibits, Extinct Monsters, fossil mounts, history of science, mammals, museums, NMNH, reptiles

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July 4, 2012 · 2:04 am

Extinct Monsters at NMNH

National Museum of Natural History in Washington, DC.

The dinosaurs at the National Museum of Natural History. Photo by the author.

Easily the best thing about living in the Washington, DC area is the plethora of free, public museums that make up the Smithsonian Institution. Tens of millions converge on the mall each year to this national center of learning, but for locals like myself, these museums are part of the backdrop of our lives. From field trips to rainy days to awkward first dates, the Smithsonian museums are an integral part of the DC experience. Still, I’d wager that I’ve spent more time at the museums than most residents, and the lion’s share of that time has been in the Paleobiology halls at the National Museum of Natural History.

When I was very young, my parents supported my interest in dinosaurs by taking me to the Museum at least monthly. Later, stopping at the Museum for a bit of quiet contemplation among the dinosaur mounts would prove irresistible whenever I was nearby. And over the course of two lengthy internships, I still occasionally took the long route across the Museum,  cutting through the Paleobiology hall to take another look at the abscess on the pelvis of the Camptosaurus, to check out something I’ve recently read about diplodocoid vertebrae for myself, or even to hear the all-too-familiar narration of the evolution of the horse one more time. In short, these galleries at NMNH have been and continue to be largely responsible for my life-long love of paleontology. They mean a lot to me.

It is no secret that NMNH has recently received a generous donation to renovate the Paleontology halls. The exhibits have changed incrementally over the course of my lifetime, including the remounting of at least three specimens and updated signage, but the exhibits are absolutely overdue for a major overhaul. In comparison to the NMNH’s new Ocean Hall and Hall of Human Origins, not to mention newer paleontology exhibits at peer institutions like CMNH and AMNH, the Paleobiology halls look quite tired. What’s more, the science of paleontology has exploded since the last major renovation in 1981, and there is tons of new information to cover.

It is an exciting time for the NMNH Paleobiology hall, but  looking into this exhibit’s past proves to be just as interesting. From the Smithsonian’s inheritance of fossils from government-funded expeditions of O.C. Marsh to the nationwide rush for dinosaur mounts in the early 20th century, to the dinosaur renaissance of the 1970s, the history of the Paleobiology hall mirrors the history of scientific and popular interest in prehistory over the past century. Many of the specimens in the hall have been on display longer than the NMNH building has existed, and seeing how their physical positioning and interpretation has changed over the years tells a fascinating story about the intersection of science, education and icons of American culture. In this series, I will attempt to tell that story as accurately as I can manage. Notable people and specimens will be introduced, and each iteration of the Paleobiology gallery will be explored.

A Road Map

Use this hub to explore the history of the NMNH Paleobiology halls. The following list will become links as the articles are completed.

Introduction

History of Paleobiology at the Smithsonian

The Marsh Dinosaurs, Part I

The Marsh Dinosaurs, Part II

Basilosaurus, Megaloceros, and Other Mammals

The Brachyceratops

Gilmore’s Diplodocus

Murals, Models and Dioramas

Selected References

“A Brief History.” Celebrating 100 Years. 2010. Smithsonian National Museum of Natural History. Accessed July 2, 2012.<http://www.mnh.si.edu/onehundredyears/brief_history.htm>

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. “The mounted skeleton of Triceratops prorsus.” Proceedings of the United States National Museum 29:433-435, 1905.

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.

“History of the Dinosaur Collection.” Dinosaurs. Department of Paleobiology, Smithsonian National Museum of Natural History. Accessed July 2, 2012. <http://paleobiology.si.edu/dinosaurs/index.html>

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June 20, 2012 · 9:41 am

Communicating Systematics, Part 2

In the previous post, I discussed how phylogenetic trees, while powerful and informative to trained eyes, can be misinterpreted by lay audiences. These misunderstandings are easy to diagnose, but actually finding solutions to the problem is challenging.

In a perfect world, every child would be introduced to evolutionary theory early and often in their obligatory science education, and everybody would be able to interpret phylogenetic trees the way scientists do. This is unlikely to happen anytime soon, especially in the United States, so educators are going to have to get creative. One option is to provide additional information to aid in the interpretation of the diagram. On the surface, adding more information is always an attractive prospect, but unfortunately it does not always work as intended. Attention spans are perilously short, and the goal of a visual representation should be to make the content immediately intuitive and easier to understand.

If conventional shapes and symbols in evolutionary trees are not getting the intended message across to target audiences, then perhaps we need to rethink how we are structuring these trees. I don’t have a catch-all solution, but the following might be enough to at least start a conversation.

Change the shape of the tree

Torrens and Barahona argue that many misinterpretations of trees stem from ideas of essentialism and teleology that are deeply ingrained in and continually reinforced by western culture. Likewise, equating up with good and down with bad is a recurring, internalized motif. Therefore, trees that illustrate evolution and diversification proceeding upward or to the right only encourage presuppositions of linear, goal-oriented evolution.

One solution that has been experimented with (at AMNH, for example) is to draw trees as circles (see below). This eliminates the problem of associating up with good and bad with down, or upward movement with progress. A circular “tree” has no orientation, and thus does not imply any taxa to be better than the rest. Personally, I find circle diagrams confusing to read, but I appreciate what they are intended to accomplish. A diagram of evolutionary relationships could theoretically take any shape, since the crucial information is in the branching order, not the nature of the lines.

A circular tree. From eplanetscience.com.

Be careful with representation of ancestors

 Many phylogenetic diagrams place specific fossil taxa at nodes along the tree in order to illustrate the course of evolution. This is informative of general evolutionary trends, but it can also be confusing. As a case in point, I just did an image search for a horse evolution diagram to use as an example, and found that many of the top results came from creationist websites. These sites aren’t worth linking to (although they are easy enough to find), but they erroneously assume that fossil taxa are thought to be directly ancestral to modern Equus caballus.  Evolutionary scientists think no such thing, but looking at the image below I can see how that conclusion could be reached.

This diagram of the evolutionary history of horses can lead to the mistaken assumption that earlier species are thought to be directly ancestral to later ones. That polytomy that leads to three unlabeled nodes doesn’t help either.

In a proper cladogram, taxa are only placed at the ends of branches. Direct ancestry is (almost) never inferred, because the scarcity of the fossil record prevents us from ever knowing exactly what evolved into what when. The cladogram below shows the relationships between the seven modern-day species of Equus. Systematists have determined a series of branching relationships based on anatomical and molecular data, and even provide a suggestion of when these divergences occurred, via the time scale. Each node represents a common ancestor that definitely existed, but we will probably never find or identify their fossils.

A cladogram of modern horse species. From Hooper Virtual Natural History Museum.

In this case, I would prefer if books or exhibits for popular audiences nixed images like the first one and instead went with cladograms that do not suggest specific ancestor-descendant relationships. Obviously the cladogram could be spiced up with colors and illustrations, but it is important to use a format that represents precisely what scientists do and do not know.

Always clarify orientation

Proboscidea phylogeny from academic.reed.edu.

Individuals well-versed in evolutionary science automatically read trees from the basal node out to the tips. Typically, and in the elephant phylogeny above, that would be from the bottom up. It can therefore come as a surprise (it certainly did for me) that non-specialists frequently attempt to read phylogenetic trees from left to right. Viewers may assume that the horizontal order of taxa across the top is significant, representing either the course of evolution or time. Neither would be correct, as Mammut on the far left and Mammuthus on the far right were roughly contemporaneous, and Loxodonta africana and Elephas maximus in the middle are the only extant elephants. Although it may not occur to specialists, it is a simple and necessary precaution to label the orientation of the tree and avoid such confusion.

Avoid calling anything “more evolved”

This is more of a nomenclature issue than a visual one, but poor graphics can exacerbate this misconception. All contemporary species, from sponges to frogs to humans, have been evolving for the same amount of time. An amphibian or reptile is not “primitive”; it is just as adapted to its environment as we are. Using this sort of terminology is attractive as a shortcut when referring to less-diverse sister groups to more-diverse clades, but it misrepresents the nature of evolution and should be discouraged.

References

MacDonald, Teresa E. “Communicating Phylogeny: Evolutionary Tree Diagrams in Museums.” 2010. Paper presented at the NARST (National Association for Research in Science Teaching).

Torrens, Erica and Barahona, Ana. “Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted?” 2012 Evolution: Education and Outreach 1-25.

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June 8, 2012 · 9:55 am

Communicating Systematics

In case you forgot, only 15% of Americans polled by Gallup accept that human beings evolved from other animals through natural processes*. This statistic has not changed meaningfully since Gallup started asking this question in 1982. This fact should be in the back of the mind of every science educator, and for that matter, every scientist, each and every day we go to work. It is a scientifically well-established fact that all life has evolved over long periods of time, and that all forms of life are related to each other. This fact is fundamental to our understanding of life on Earth. The goal of both educators and scientists is to expand our knowledge and awareness  of our world, and it is therefore disconcerting that so few people are willing (or have had to opportunity to) acknowledge the wealth of information that an understanding of evolution provides.

 *A couple complaints about that link. First, the phrasing of the question, “human beings evolved over millions of years from less advanced forms of life” (emphasis mine) is poor, read on for reasons why. Second, belief that humans evolved “with God’s guidance” does not seem like a meaningful distinction to me, and does not suggest a proper understanding of evolution.

The overwhelming number of people who do not accept evolution is intimidating. The fact that our politicians and leaders are often among this number is even more troubling.  It can be tempting to retreat into academia and  whine about the problem to our peers, or perhaps ignore it entirely. However, 30 years of unchanging results on the Gallup poll indicate that the issue is not going to go away. Both educators and scientists need to take the offensive and directly address misconceptions and misunderstandings about evolution, as well as find effective means to mitigate them.

Phylogenetic Trees

In the world of science education, one of the trickiest issues is supplying appropriate context. Although all good science can be explained in clear, readily-understandable language, most research still requires some background on the Big Ideas in science. Two huge examples are evolution by natural selection and the scientific method, which I briefly discussed here and here. Without an understanding of how scientific ideas or generated or how evolution works, discussing the finer points of, say, feeding strategies of tyrannosaurs is quite pointless. Unfortunately, even among people who accept the fact that evolution is a real phenomenon, this background all too often does not exist.

Educators need to supply the public with the context they need to understand current science, and one good area to focus is the reading of phylogenetic trees. A phylogenetic tree is a branching diagram that depicts inferred evolutionary relationships among organisms. A tree implicitly shows that included organisms descended and diversified from a common ancestor. As such, phylogenetic trees are a visual embodiment of evolutionary theory, and provide an informative narrative of the history of life.

As is often the case, David Hone has already provided a wonderful explanation of how scientists construct trees and how to read them correctly, so I’ll just drop that link and move on. The problem is that although evolutionary trees are often used to convey ideas in museum displays and general interest science articles, many lay-viewers are interpreting them inaccurately. Reading a tree requires practice and expertise that shouldn’t be taken for granted, because misinterpretations only provide fodder for the anti-evolution/anti-science lobby. Let’s go through the common misinterpretations one at a time (many of these are discussed in Torrens and Barahona 2012, a few are my own additions).

Evolution is goal-oriented. In fact, evolution is not progressive, but is the product of organisms adapting to their specific environment. When that environment changes, taxa that were once well-adapted often die out. Being “well-evolved” is therefore  fluid and transitory state. The misconception of directed evolution is probably related to ingrained western religious views of human superiority over nature. Rather annoyingly, cultural anthropologists often buy into the erroneous idea of progressive evolution, and attempt to use it as evidence that science is but one of many equally correct world-views.

There is a “main line” of evolution. This is largely the product of late 19th century drawings of trees of life which used literal trees as the basis of the diagram. Most famously, German natualist Ernst Haeckel illustrated the Systematischer Stammbaum des Menschen in his book Anthropogenie in 1874. In this drawing, the diversity of life is overlaid on a tree, which has a thick trunk running straight up to humans and other primates at the top. Again, this plays into concepts of human superiority and inevitability that have nothing to do with biological evolution.

Some contemporary species are more or less evolved than others. All contemporary species, from sponges to frogs to humans, have been evolving for the same amount of time, and are just as adapted to their environments as we are. Unfortunately, placing humans or mammals at the top or the right of phylogenetic trees seems to be an unshakable habit, even for systematists, which only encourages the notion that these taxa are somehow better.

Similarity among taxa always implies relatedness. Determining evolutionary relationships is a complex process. Modern systematists use huge matrices of independent characters to calculate the most parsimonious trees. Furthermore, Hennigean cladistics requires that relationships only be determined using synapomorphies (shared derived traits) rather than plesiomorphies (shared primitive conditions). Although the salmon and the lungfish below superficially appear more like one another than the cow, similarities like a fishy shape and a lack of a neck are primitive conditions, not specializations. The synapomorphies shared by the lungfish and cow, such as jointed limbs and the ability to breathe air, inform us that they shared a more recent common ancestor than either did with ray-finned fish.

A counter-intuitive cladogram. Subjective similarity does not always mean relatedness.

Change only occurs at nodes. The nodes in a phylogenetic tree do not represent literal evolutionary events. Rather, evolution is a continuous process. This is a case where I like to ask people who make this misconception, “how could we know that?” This can get people thinking about what evidence is available to scientists, what conclusions can be reached from these data, and what isn’t known.

Example taxa illustrated lower in the tree represent direct ancestors of taxa higher in the tree. It can be helpful to use fossil species to illustrate the general state of an evolutionary lineage at varying points in time (this is done all the time with diagrams of horse evolution). However, with few exceptions, the incomplete nature of the fossil record makes it impossible to know exactly which species were directly ancestral to others.

Traditional Linnean categories are directly applicable to trees. In fact, most  (sensible) modern systematists prefer the cladistic methodology, which requires that all groups be monophyletic (that is, made up of all descendents of a common ancestor, with no exclusions). For example, the traditonal Linnean definition of reptiles, which includes turtles, lizards, snakes, tuataras and crocodiles, is not monophyletic, because any cladistic unification of these taxa would also have to include birds.

The traditional definition of reptiles, which excludes birds, is paraphyletic.

This went on a bit longer than I expected, so I’m going to leave these issues hanging for the time being. But do not fret, I will finish this train of thought soon with a discussion of potential solutions to these misinterpretations that have been attempted, and some that may be attempted in the future.

References

MacDonald, Teresa E. “Communicating Phylogeny: Evolutionary Tree Diagrams in Museums.” 2010. Paper presented at the NARST (National Association for Research in Science Teaching).

Torrens, Erica and Barahona, Ana. “Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted?” 2012 Evolution: Education and Outreach 1-25.

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May 5, 2012 · 1:10 am

A brief history of mounted dinosaur skeletons

Mounted fossil skeletons, especially those of dinosaurs, are common at medium and large natural history museums. These mounts play a central role in the public’s perception of not only dinosaurs and other prehistoric animals, but of museums as well. However, just as dinosaurs are relatively new to science, fossil mounts have not always been a part of museums. The word dinosaur was coined in 1842 by British anatomist Richard Owen, based on a handful of fragmentary remains of large, extinct reptiles. Nevertheless, the study of dinosaurs did not start in earnest until 1865, when Joseph Leidy of Philadelphia’s Academy of Natural Sciences described Hadrosaurus, the first dinosaur found in the United States, and eventually, the first dinosaur skeleton to be mounted. The western frontier of North America proved to be a richer dinosaur hunting ground than Europe had been, and so vertebrate paleontology was among the first realms of science that American researchers could claim as their own.

The American fossil rush that followed came in two waves. In the 1870s, the field was dominated by the well-publicized but ultimately counterproductive feud between Othneil Charles Marsh of Yale and Edward Drinker Cope of the Academy of Natural Sciences. While these collectors amassed enormous collections of fossils for their respective institutions, their research remained largely out of the public eye.

1868 Hadrosaurus mount at the Academy of Natural Sciences. From http://www.naturalhistorymag.com.

The second wave came at the turn of the 20th century, and was intrinsically related to the rise of the large museums that sprang up in America’s cities at this time. The American Museum of Natural History in New York, the Carnegie Museum of Natural History in Pittsburgh, the Field Museum of Natural History in Chicago and other, similar institutions became involved in a fierce competition to find and display the largest dinosaur (Spalding 1993). At this point, the discipline of paleontology had been marginalized in American universities, in part because of a rising interest in experiment-driven “hard” sciences like molecular biology and physics, but also because the demands of space, labor and money required by paleontological research was prohibitive.

1905 Brontosaurus mount at AMNH. From Dinosaur Tracking.

Instead, paleontologists made their homes at the large natural history museums, which were backed by wealthy benefactors who were impressed by their collections of giant fossils. At the time, it was fashionable for wealthy businesspeople to donate extravagantly to cultural institutions, including museums, in the cities where they made their fortunes. To the benefactors, there was no doubt that paleontologists and their fossil specimens could draw larger crowds than a chemist or physicist ever could. Steel tycoon Andrew Carnegie is credited with conceiving of the idea to display a mounted dinosaur skeleton as the centerpiece of his new museum in Pittsburgh. Carnegie gave CMNH $10,000 to find a giant sauropod dinosaur, preferably just like the Apatosaurus (then called “Brontosaurus”) collected by Marsh 30 years earlier. Patrons of the other large museums followed suit, and by 1905 the Carnegie Museum, the American Museum and the Field Museum all had sauropod mounts on display, along with a menagerie of other dinosaurs and prehistoric animals.

Unfortunately, by modern standards these displays favored spectacle over good science. As mentioned, vertebrate fossils almost never found as complete skeletons, but as scattered and isolated elements. As such, the museum collectors were not racing to find a single, perfect skeleton, but to amass enough individual dinosaur bones to complete a mount. The early 20th century dinosaur mounts are typically composed of fossils found in rocks separated by hundreds of miles and millions of years in age. The collectors did not keep good records of where the fossils came from, so modern museum workers can only guess how many individual dinosaurs make up the mounts they have inherited. For example, the Stegosaurus at the Peabody Museum of Natural History is composed of at least five individuals, and researchers disagree whether the Giraffatitan  at Berlin’s Museum fur Naturkunde is made up of three or five different animals.

A preparator at AMNH assembles the “Brontosaurus” mount. From http://preparation.paleo.amnh.org/5/expeditions.

Additionally, the technicians that created the mounts were attempting something that had never been done before, and perhaps inevitably, poor choices were made during the construction process. Adam Hermann, lead fossil preparatory at the American Museum of Natural History during the early 20th century, used highly destructive techniques when creating fossil mounts. Fossils were connected to steel armatures by drilling screws and bolts directly into the bone, and broken bones and visible sections of the armature were hidden with liberal applications of plaster (Evander 2004). These practices turned out to be essentially irreversible, and modern workers are hesitant to attempt to dismantle old mounts for fear of destroying the fossils entirely.

The creation of the first fossil mounts was chiefly inspired by the vanity of museum benefactors, but their influence on audiences and their ability to draw crowds is undeniable. Although new dinosaur mounts have been constructed over the course of the 20th century, many, if not most, of the historic mounts remain on display, important not only as evidence of prehistoric life, but as icons of the history of science and museums in America.

References

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

Evander, Robert L. (2004.) “Armature Damage in a Mounted Specimen.” Presented at Society of Vertebrate Paleontology Annual Conference, Bristol, U.K.

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April 3, 2012 · 1:33 am

Their hands were everywhere: the Morrison Natural History Museum

Outside the Morrison Natural History Museum. Doesn’t look like much…

Last week, I had a fantastic experience at the Morrison Natural History Museum, a little gem tucked away in the tiny town of Morrison, Colorado, on the north side of Denver. Since its opening in 1985, the Museum has served as a local educational resource covering the region’s plentiful paleontological resources. According to its website, the Museum is primarily a teaching institution. An affiliated foundation raises funds to bring local students on field trips, in support of the Museum’s mission to nurture “an understanding of and respect for the deep past.” In keeping with this teaching institution, gentle touching of all the fossils and casts is encouraged. This policy, and the design choices that go with it, are what truly set the Morrison Museum exhibits apart.

Paleontologically-inclined people are of course familiar with the Morrison Formation, the sequence of Upper Jurassic beds that extends across much of the western United States. The formation, which extends some 600,000 square miles, was named for the town of Morrison, where fossils were first discovered in 1877. The Morrison formation is probably best known as the epicenter of the “bone wars” between Othniel Charles Marsh and Edward Drinker Cope, who each led competing teams of fossil hunters across the region, attempting to best one another’s discoveries. Marsh and Cope were affiliated with the Peabody Museum in New Haven and the Academy of Natural Sciences in Philadelphia, respectively, so the fossils they collected all ended up back east. Indeed, while the Morrison region is among the most important and productive places for finding dinosaurs in the country, comparatively few of the treasures found there have remained in the region. The Morrison Natural History Museum therefore exists, at least in part, as a dedicated local repository and interpretative center for the region’s natural history.

The 1st floor Jurassic exhibit.

The Museum’s exhibit space is tiny, only 2000 square feet, but it is chock full of awesome. The exhibition consists of three main rooms, each one representing a geological time period. In the first floor Jurassic gallery, highlights include partial casts of Allosaurus and Apatosaurus,  the holotype of Stegosaurus, trackways attributed to Stegosaurus and a baby sauropod, and some original 19th century lithographic prints from Marsh’s monographs. For those interested in the history of paleontology, and of science in general, those prints are particularly fascinating.

Infant sauropod trackway with model of probable trackmaker.

Cretaceous and Cenozoic exhibits are found on the second floor. Most of the objects here are casts, most notably full skeletons of Platycarpus and Pteranodon, and skulls of Triceratops, Tylosaurus and a Columbian Mammoth. There are also a number of live animals on display, including a very charismatic monitor lizard thoughtfully placed next to its close relatives, the mosasaurs.

Original 19th century lithograph prints of fossil illustrations by Marsh’s team.

The signs and labels in the exhibit are noteworthy for their succinctness and clarity. It can be extremely challenging for writers of museum copy to provide appropriate depth of content without confusing, boring or alienating audiences with too much text. Overlong and unfocused labels are particularly common in small museums, where most of the copy is written by a single curator bent on sharing everything he or she knows about a topic. On the other end of the spectrum, larger, committee-designed exhibit labels can be too brief, too simple and too narrowly focused on the exhibit’s educational goals to be of much use to anybody. Happily, the Morrison Museum avoids both of these pitfalls. Labels are simple and attractive, but still informative and up-to-date. I was rather impressed by the economical way in which they addressed the most important topics in paleontology.

An example of a brief but content-rich label.

Obviously, the fossils and other objects on display are fantastic, and many, like the trackways, are quite unique. However, as mentioned above, one of the most remarkable aspects of the Museum is that touching of all the fossils and casts is encouraged.  Few objects are behind glass; everything is out in the open for people to touch and examine up close. There are many in the museum field who would be horrified by such an arrangement. When putting objects on exhibit, it is a given that they are considered consumable. No matter what precautions are taken, anything put on display will inevitably suffer damage. Of course, the flip side is that exhibit designers want to allow visitors to get as close to the objects as possible. The Morrison Museum has taken this to the extreme. The fossils, many one them irreplaceable holotype specimens, are fully exposed to accidental or intentional abuse by visitors. This is a very bold move on the part of the Museum, and it makes the point that the knowledge visitors can gain from full access to objects is more valuable that the objects themselves.

I won’t lie, my initial reaction upon seeing this exhibit layout was open-mouthed horror. But after spending some time in the space, I think the Morrison Museum may be on to something. This is a great way to tap into the multiple intelligences of visitors. Obviously, this system only works because the Museum’s attendance is on the low side (I would hate to see what the summer hordes at NMNH or AMNH would do if they were allowed to run wild among the mounts),  but given these circumstances I think the open-access approach is a great educational tool.

Overall, I was very pleased with my visit to the Morrison Museum. The volunteer staff knowledgable, passionate and helpful, the exhibits were excellent, and the handful of other visitors passing through (mostly young children) seemed genuinely engaged. The Museum is well worth a stop for anyone in the Denver area, and may well be a worthwhile model for other museums to follow.

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March 15, 2012 · 6:13 am

Exhibits with an Agenda

I am currently part of a team preparing a small exhibit on sustainable energy for a Midwestern history museum. Our original goal was simple: to review the regional history of renewable energy production and use, in order to illustrate that “green living” is not a new concept. However, as with most creations of passionate people, the size and scope of the exhibit has expanded quite a bit, and the exhibit is now intended to be a more forceful argument for responsible energy use and the importance of being aware of one’s own energy footprint. There’s no denying this argument has always been an implicit part of the exhibit plan. In this part of the world, there is an unfortunate resistance to, if not outright demonization of progressive energy policy, and we absolutely want to undermine the assumptions and misconceptions that fuel this anti-green discourse. What has changed is that we’ve stopped hiding our agenda.

In his 1994 essay Evaluating the Ethics and Consciences of Museums, Robert Sullivan proposes that museums are “moral educators”. Either deliberately or through unconscious subtext, museums inherently shape the opinions, worldview and conception of self of their visitors. It is unavoidable that museum content will be shaped by subtextual ideologies and assumptions. Identifying and unpacking these biases is a huge issue (it’s basically the entire focus of the humanities for the last 50 years or so), but one can still exert a degree of control over which assumptions are expressed.

Museums are among the most trusted of media forms, and are widely considered to be far more reliable than books, television or newspapers. This public trust can be intimidating, but it does present a unique opportunity: if a museum takes a stand on an important issue, it will probably be taken seriously. Obviously, trust is not a resource to be squandered needlessly, but when wielded with care and deliberation it can be very powerful.

With our sustainable energy exhibit, we are trying very hard to harness that power in an effective way. The issues that surround energy use are very serious, as the availability and ready access of energy are critical to our modern economy, infrastructure, and way of life. Unfortunately, the discourse around renewable energy, diminishing fossil fuels and climate change is highly politicized. We want to be plain about the economic and environmental dangers that good, solid research tells us is in our future, and we want to call out sources of misinformation. Above all, we want to give people the intellectual tools to evaluate controversial issues for themselves, and to identify which arguments are backed by concrete evidence and which are not.

Our exhibit may well raise some eyebrows for taking a hard stance on a topic that many in this region consider to be “controversial”. I think this is a good thing. Museums really should not be playing the “both sides of the story” game that other media forms play when the evidence and experts clearly favor one camp. If we are avoiding asking our audiences hard questions, then we are not teaching, and we are not doing our job.

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February 3, 2012 · 10:24 am

WTF, AAA?

Over the past couple months, as I have hoped in vain that the folks at SV-POW will post cool stuff about sauropods again, I’ve learned a great deal about open-access publishing and the Research Works Act. Kudos to them for creating awareness. The sinister implications of the RWA are well documented around the web, so I’ll just provide the short version.

At present, taxpayer funded research institutions in the U.S., namely the NIH, require that research results must be freely accessible online. This is a reasonable requirement that is hard to argue against: if the public pays for science, the public should be able to see the results. However, this open-access policy gets in the way of the profits of the academic publishing industry. Publishers like Elsevier and Springer have astonishingly high profit margins of 36% or more, dwarfing even those of Apple, and they aim to keep them that way. Academic publishers have a pretty sweet scam going, in which (largely publicly funded) researchers supply the papers and the peer review for free, while the publishers take the full copyright, and charge $30-$50 to view a single article. All the publisher does is format the manuscripts into a physical volume, which is irrelevant since most people now access papers online. Enter RWA, an effort by publishers to push back against increasing awareness of their unnecessary and monopolistic role as gatekeepers of knowledge.

Until this point, the voices of dissent from the academic community seemed to paint a fairly straightforward picture. Researchers, who know the academic publishing industry well, are more-or-less unanimously opposed to the unbridled corporate greed represented by the RWA. But then this business happened (.pdf link). The American Anthropological Association, with which I’ve taken issue before, has thrown in its lot on the side of the publishers. The previously linked AAA statement was a response to the U.S. Office of Science and Technology Policy’s ongoing Request for Information (check out all the responses to date here). The AAA claims that there is currently no problem with the accessibility of research, and that it is unfair to undermine the right of publishers to sell their property at market value. Here are the choice quotes:

We write today to make the case that while we share the mutual objective of enhancing the public understanding of scientific enterprise and support the wide dissemination of materials that can reach those in the public who would benefit from such knowledge (consistent with our association’s mission), broad public access to information currently exists, and no federal government intervention is currently necessary.

Mandating open access to such property without just compensation and lawful procedural limits constitutes, in our view, an unconstitutional taking of private property – copyrighted material – an expropriation without fair market compensation. In our view, such a practice cannot and will not withstand judicial review.

Both of these arguments are nonsense. If the AAA believes that “those in the public who would benefit from such knowledge” currently have appropriate access to research, then their definition of the public must end at researchers at large institutions. As articulated at Neuroanthropology, this insular view is unhelpful and unacceptable, and it is particularly surprising that it is coming from a group of anthropologists. Do the non-profit groups anthropologists work with in developing countries not require access to papers? What about the people the research is about? Interested lay-people? Under the current system, and to an even greater extent should the RWA pass, anybody not affiliated with an institution with a well-funded library* has to pay exorbitant prices out of pocket to view research. As a result, the research remains largely in the academic sphere. Given the political nature of anthropologists in general, it is shocking that the AAA deems this acceptable.

*Side note: Even as a grad student, getting access to papers can be a real problem. Even large universities sometimes only provide access to volumes of journals within a certain date range, and when I’m doing field work or an internship, I can no longer get access.

The second quote is bunk because, as explained previously, the services provided by academic publishers are minimal, if not counterproductive to the dissemination of knowledge, and do not constitute anything that researchers could not do themselves in this information age.

As they did a year ago when they removed the reference to science from their mission statement, the AAA has demonstrated that their interests are not in sync with researchers. Honestly, I don’t know who they are trying to represent. They are working against the interests of serious researchers, advocacy groups who help the people anthropologists work with, and the dissemination of knowledge in general. AAA, please stop.

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Aside

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