Another year, and another major renovation of a historic paleontology exhibition is underway. The dinosaur and fossil mammal halls at the Yale Peabody Museum of Natural History (YPM) closed to the public on January 1st. The rest of the museum will follow in July, with a planned reopening in 2023. This will be the first comprehensive renovation of the museum since the current building opened in 1931, and the upgrades are long overdue. For decades, most of the YPM exhibits have been a museum of a museum—a time capsule preserving the state of natural science and museum design in the mid-20th century. The dinosaur hall in particular looks almost exactly as it did when Rudolph Zallinger completed the spectacular Age of Reptiles mural on the east wall in 1947 (a handful of newer specimens, revised labels, and video terminals notwithstanding).
The Great Hall of Dinosaurs upon my last visit in 2014.
It’s exciting to see ground breaking on the new museum and exhibits, because this renovation has been a long time in coming. Serious discussions were underway in 2010, if not earlier, and a set of conceptual images was released as part of a fundraising effort launched in 2013. It appears that a lot has changed since then. The scope of the renovation has expanded to encompass the whole museum, not just the paleontology exhibits. And certain details from the 2013 concept—such as a mezzanine in the dinosaur hall opposite the Age of Reptiles mural—have been dropped. Last year, YPM launched a dedicated website showcasing the latest renovation plans. It’s wonderful that the institution is committed to keeping their community involved in and informed about the transformation of a public space that is near and dear to so many.
Naturally, this renovation is an opportunity to take a deep dive into the YPM fossil displays, and look at the specimens, artwork, and people that defined this institution in the past and which will carry it into the future. Expect upcoming posts exploring the future of these exhibits, but for now let’s start with a look back at the exhibit that once was.
Rendering of the new dinosaur hall, as of late 2019. Source
YPM was founded in 1866 with a gift from George Peabody. Peabody was the uncle of O.C. Marsh, who had been appointed Professor of Vertebrate Paleontology at Yale that same year. Having been awarded tenure and his own museum, Marsh began to lead and send crews into the American west to collect fossils. Many of Marsh’s expeditions were under auspices of the U.S. Geological Survey, and those fossils eventually made their way to the Smithsonian. The remainder, however, entered the YPM collections, where they remain to this day.
After Marsh’s death in 1899, his student Charles Beecher took over vertebrate paleontology at YPM. Beecher was, in turn, succeeded by Richard Lull. Lull never met Marsh (and the two were quite different in many ways), but he nevertheless spent much of his career carrying on his predecessor’s legacy. Like his Smithsonian counterpart Charles Gilmore, Lull expanded Marsh’s often laughably brief descriptions into proper monographs, which are still used by paleontologists today. And like Gilmore, Lull put the Marsh fossils on public display, guiding the assembly of the mounted skeletons that have held court at YPM ever since.
Lull became director of YPM in 1922, and it was in this role that he oversaw the museum’s move from it’s modest original building to the larger, French Gothic-inspired structure where it currently resides. Construction of the new museum was completed in 1925, and Lull spent the next several years developing the dinosaur hall we know today. Marsh, for his part, disliked the idea of display mounts, considering it a waste of time and effort. And limited space at the old facility meant that only two large dinosaur mounts—Edmontosaurus and Stegosaurus—were assembled between 1900 and 1925. The new building, however, had a great hall specifically built to house the Marsh dinosaurs, so Lull and his team got to work filling it.
Camarasaurus and Camptosaurus
Camarasaurus and Brontosaurus mounted skeletons.
Most of the new mounts were assembled from fossils collected around 1880 at Como Bluff, Wyoming. Working for Marsh, William Reed and his crew amassed a treasure trove of Jurassic dinosaurs there, most famously the Brontosaurus holotype. Naturally, Lull devised Brontosaurus (YPM 1980) as the centerpiece of the dinosaur hall. Because of its size and complexity, it was the first of the new mounts to begin construction and took the longest to complete. The Brontosaurus was literally built into the floor: photos from the 1920s show a latticework of steel beams designed to spread its weight. Once the floor was installed, the Brontosaurus could not be moved.
In the meantime, preparator Hugh Gibb assembled two other mounts from Como Bluff material: Camarasaurus and Camptosaurus. The Camarasaurus (YPM 1910) is 21-foot juvenile, consisting of a complete vertebral column from the 2nd or 3rd cervical to middle of the tail, and most of the larger limb bones. The feet and most of the ribs are reconstructed, as is the skull, which is a fairly crude sculpture. In his 1930 publication discussing the mount, Lull commends Gibb for how closely his reconstruction matched the nearly complete and articulated juvenile Camarasaurus collected by the Carnegie Museum at what is now Dinosaur National Monument, despite the fact that Gibb had never studied that specimen. Lull only notes that the YPM mount has one fewer cervical and one fewer caudal than the Carnegie specimen, and that the reconstructed cervical ribs are much too short.
Camptosaurus and Camarasaurus mounted skeletons.
Gibb also assembled the Camptosaurus mount (YPM 1880), which he completed in 1937. Yet another specimen from Reed’s excavations at Como Bluff, the Camptosaurus is notable for how closely it mirrors Marsh’s illustrated reconstruction from 40 years earlier. It seems reasonable to assume this was a deliberate homage, although Gibb did follow Gilmore’s example and removed Marsh’s erroneous lumbar vertebrae. The sculpted skull, modeled after Iguanodon, was typical of Camptosaurus reconstructions at the time but is now known to be inaccurate.
Neither Camarasaurus nor Camptosaurus are slated to return in the renovated exhibit. Marsh originally designated both of these specimens as holotypes for “Morosaurus” (=Camarasaurus) lentus and Camptosaurus medius. Opinions on the validity of those particular species have changed over time, but it’s important that a new generation of paleontologists has an opportunity to study the original fossils up close, which has been virtually impossible in their mounted form.
Claosaurus
Relief mount of Claosaurus.
High on the west wall is one of YPM’s most overlooked dinosaurs. This relief mount represents the only confirmed remains of Claosaurus agilis (YPM 1190), a hadrosaur found in the marine deposits of western Kansas. Claosaurus is a bit of a taxonomic mess: Marsh initially announced this fossil as a new species of Hadrosaurus, before upgrading it to its own genus. Then, he decided to sink all of the much younger Lance Formation hadrosaur material (what is now called Edmontosaurus annectens) into the Claosaurus genus. It’s a difficult web to untangle, but Claosaurus is a real taxon that lived alongside animals like Pteranodon and Tylosaurus.
Lull and Wright describe the mount as “recent” in their 1942 monograph on hadrosaurs, so it must have been assembled after the move the current building. Most of the vertebrae and limb bones are real, but the skull is (obviously) a model built around a few fragments of jaw. Although it’s hard to see from the ground, the preservation is apparently poor, and most of the bones are crushed to some degree. Lull and Wright attest to the significance of Claosaurus as the earliest known true hadrosaur, but were clearly frustrated by the quality of the specimen. Perhaps modern paleontologists will have better luck, once it’s taken off display and returned to the collections.
Centrosaurus
The Centrosaurus half-mount and its Cretaceous buddies.
Variably known as Monoclonius flexus, Centrosaurus flexus, and Centrosaurus apertus, this ceratopsian skeleton (YPM 2015) was collected by Barnum Brown on the American Museum of Natural History’s extremely productive expeditions to the Belly River region in Alberta. I’m not sure when YPM acquired the fossil (presumably in a trade), but it was mounted and on display by 1929. At some point during the development of the fossil mammal hall, Lull became enamored of half-mounts like this one, in which the animal appears bisected along its sagittal line. Half the skeleton is assembled on one side, while a fleshed-out model is visible on the other. Several mammal specimens at YPM are displayed this way, but the Centrosaurus is the only dinosaur.
Lull discusses the choices made in reconstructing Centrosaurus at length in his 1933 monograph on ceratopsians. He describes the relief-mounted Centrosaurus at AMNH as an imperfect representation of the animal’s life appearance because it preserves the death pose it was found in. In contrast, the YPM version is reconstructed in a three-dimensional standing posture. Lull specifically points to his Centrosaurus‘s nearly straight neck and sprawling forelimbs (with the humerus nearly horizontal) as superior to the AMNH presentation. The issue of ceratopsian forelimb posture is still not completely resolved, but there is probably some truth to Lull’s sprawling reconstruction.
The life-reconstruction side of Centrosaurus, as figured in Lull 1933.
For the fleshed-out portion of the mount, Lull directed the artist to match the musculature and skin texture of iguanas and alligators. A loggerhead turtle was referenced for the mouth and beak. Lull chose to give the small processes on the lower edges of the frill a horny sheath, rather than the fleshy look popularized by Charles Knight. Overall, the life restoration is on the lean side compared to our modern understanding of ceratopsians, but many details—including the digitigrade fingers and forelimb posture—have held up well.
Next time, we’ll look at how historic specimens like Brontosaurus, Stegosaurus, and Deinonychus might be modernized for the new version of the hall.
References
Lull, R.S. 1930. Skeleton of Camarasaurus lentus recently mounted at Yale. American Journal of Science 19:105:1-5.
Lull, R.S. 1910. Stegosaurus ungulatus Marsh, recently mounted at the Peabody Museum of Yale University. American Journal of Science 30:180:361-377.
Lull, R.S. 1933. A Revision of the Ceratopsia or Horned Dinosaurs. New Haven, CT: Tuttle, Morehouse, and Taylor Co.
Lull, R.S. and Wright, N.E. 1942. Hadrosaurian Dinosaurs of North America. New York, NY: Geological Society of America.
Marsh, O.C. 1872. Notice on a new species of Hadrosaurus. American Journal of Science 3:16:301.
Marsh, O.C. 1890. Additional characters of the Ceratopsidae, with notice of new Cretaceous dinosaurs. American Journal of Science 39:233:418-426.
EXTINCT MONSTERS 
I believe the skull on the YPM Camptosaurus was modeled based on the one now referred to Theiophytalia, not Iguanodon.
To give you a history lesson, most skull restorations of Camptosaurus in the 20th century were based on the holotype of Theiophytalia kerri (YPM 1887)*, which was found in the Garden of the Gods locality in Colorado. However, Bakker (1998) noted that YPM 1887 was more derived than Camptosaurus and similar to styracosternan iguanodonts in having a heavily rugose snout, providing the first indication that it represented a new genus and species distinct from Camptosaurus. According to Brill and Carpenter (2006), the skull of Camptosaurus is a bit similar to that of Dryosaurus in the shape of the snout, but is still more derived.
So yes, the skull in the Camptosaurus YPM mount that is being taken down does look similar to Iguanodon, but was based on the holotype and only specimen of Theiophytalia. The Wikipedia article for Camptosaurus (https://en.wikipedia.org/wiki/Camptosaurus) has photos of Camptosaurus specimens at dino museums that are based on the skull reconstruction for Camptosaurus provided by Brill and Carpenter (2006).
*Gilmore (1909) referred the Theiophytalia holotype to “Camptonotus” amplus, unaware that the C. amplus holotype consists of only a foot. Bakker (1998) and Galton et al. (2015) recognized the Camptonotus amplus holotype belonged to Allosaurus, the latter authors referring to it as Allosaurus amplus.
Bakker, R. T. (1998). Dinosaur mid-life crisis: the Jurassic-Cretaceous transition in Wyoming and Colorado. In Lucas, Spencer G.; Kirkland, James I.; Estep, J. W. (eds.). Lower and Middle Cretaceous Terrestrial Ecosystems. 14. New Mexico Museum of Natural History and Science Bulletin. pp. 67–77.
Brill, K. & K. Carpenter (2006). A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus. In Carpenter, Kenneth (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington: Indiana University Press. pp. 49–67.
Galton, Peter M.; Carpenter, Kenneth; Dalman, Sebastian G. (2015). The holotype pes of the Morrison dinosaur Camptonotus amplus Marsh, 1879 (Upper Jurassic, western USA) – is it Camptosaurus, Sauropoda or Allosaurus?. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen. 275 (3): 317–335. doi:10.1127/njgpa/2015/0467.
Gilmore, C.W. (1909). Osteology of the Jurassic reptile Camptosaurus, with a revision of the species of the genus, and descriptions of two new species. Proceedings of the United States National Museum. 36 (1666): 197–332. doi:10.5479/si.00963801.36-1666.197.
Camptosaurus medius was sunk as a junior synonym of Camptosaurus dispar long ago, Camarasaurus lentus is still considered a valid Camarasaurus species, even though I’m still waiting for the planned revision of Camarasaurus alpha-taxonomy by Emanuel Tschopp and colleagues to be published.
The only known specimen of Claosaurus was washed out to sea by a river stream and must have been scavenged by sharks. The description of Eotrachodon in 2016 and ongoing work deciphering late Turonian-early Campanian hadrosaurid evolution in North America will probably help figure out what the skull of Claosaurus really looked like.