Back in October 2019, the North Dakota Geological Survey’s Paleontological Resource Protection Program (@NDGSPaleo) tweeted out a picture that sent a ripple of excitement through scientists and paleo enthusiasts alike. The photo showed the right manus (hand) of Dakota, an infamous Edmontosaurus annectens specimen. Dubbed a “dinomummy”, Dakota is unique for the large areas of uncollapsed skin and other features remaining in the fossil’s preservation. But beyond skin, what is so special about Dakota’s hand?
Answer: Dakota has a hoof.
To be more specific, there is a keratinized sheath over some of the digits (fingers) of the animal’s hand. Furthermore, other fingers were shown to be encased in a so-called “mitten” of skin. While on the surface this might not appear to be anything special, it actually has major implications for the lifestyle and behavior of Edmontosaurus, and possibly other hadrosaurs as well. It also raises a lot more questions than answers about the development of hoof-like structures and their functionality in non-mammalian animals.
The History of Dakota the Dino Mummy
Sixty-seven million years or so ago, an Edmontosaurus wandered through a humid North Dakota filled with conifers, ginkgo, angiosperm trees, and the occasional fern. In this warm climate, the large dinosaur found its way to a sandy channel of water, such as the bend of a river. It was at this location where the Edmontosaurus died, likely falling into the channel.
From the moment the Edmontosaurus died, a unique sequence of events unfolded. Sediment began rapidly burying the animal’s body. Once buried, the sediment and soil likely became waterlogged. This would have created a “mineral-rich soup” surrounding the body before more extensive decay began. All these minerals quickly swept around and within the animal’s skin, replacing the hide and other physical structures.
The fossil then waited patiently for sixty-seven million years.
In 1999, a teenager by the name of Tyler Lyson was out on his uncle’s ranch near Marmarth, North Dakota. On a routine search for fossils, he spotted what appeared to be hadrosaur vertebrae poking out of the base of a hill. At the time, Lyson decided not to excavate, but took note of the find and went on his way.
Five years later, he decided it was time to go back and excavate his earlier find. Lyson quickly realized he wasn’t dealing with a normal fossil. After discovering fossilized skin fragments, he contacted Dr. Philip Manning, a paleontologist at the University of Manchester in England. Dr. Manning agreed to help Lyson with the dig. By 2006, excavations were complete; in all, they pulled almost 15 total tons of initial material from the site.
Preparators and researchers began working on the fossil, whittling those 15 tons of material down to about five or so. The specimen, now nicknamed “Dakota,” eventually went on loan to the North Dakota Heritage Center. Eight years after the initial excavation, the Center ended up purchasing the privately-owned fossil for three million dollars. Lyson–now a vertebrate paleontologist for the Denver Museum of Nature & Science–used that money to establish an endowment fund for the Marmarth Research Foundation. Lyson’s foundation is intended to further the advancement of paleontology through education, curation of fossils, and research on fossil material.
From 2014 to the present, Dakota has remained in the care of the North Dakota Heritage Center. Currently, they are cleaning the specimen for a brand new exhibit opening in February 2020. With this cleaning and new exhibit, the intent is to provide better lighting and climate conditions, make sections of the fossil easier to view, and highlight interesting features. In addition to having Dakota on display, the folks at NDGS Paleo are continuing to research and understand the fossil more in-depth.
The Scoop on Dakota’s Hand
Dakota is already a very unique specimen whose remains have altered the way we understand Edmontosaurus (and potentially other hadrosaurs as well). The level of preservation has allowed for a more three-dimensional understanding of the animal’s body shape. In addition, researchers have been able to calculate muscle sizes and determine just how fast Dakota could run. All of this information has changed how we perceive these hadrosaurs, but this recent unveiling of Dakota’s hand has the capacity to alter our understanding even further.
To understand exactly what’s going on with Dakota’s right hand, let’s break it down a little more concretely. First, the most important thing about the manus is that there is a “hoof-like” nail on the third digit. This is significant because lineages outside mammals have not historically shown evidence of hooves. The fact that a dinosaur has a convergent and/or similar feature is very compelling.
Moving on from the hoof, much of the hand is encased in what NDGS Paleo has dubbed a “mitten” of skin. There is no thumb (or first digit) and the second digit has a more spade-like nail. The mitten also encases the fourth digit. The fifth digit is not within the mitten, and has no nail.
Understanding the Implications
All of the features of Dakota’s hand lead to an important revelation: Edmontosaurus were not moving their fingers individually. Rather, their hands more likely acted as a single unit. But what exactly does that mean for how we understand these hadrosaurs?
To really get a sense of what the hoof-like nail and mitten mean, it’s worth looking at the function of hooves and analogous extant animals. The hoof–a feature seen almost exclusively in ungulate mammals–is defined as the tip of a toe strengthened by a thick keratin covering. For ungulates, the hoof performs many functions, including:
- Supporting the animal’s weight
- Dissipating energy impact as the hooves strike the ground or surface
- Protecting tissues and bones within the hoof capsule
- Providing traction
Given these known functions of hooves, how would the sheath over the Edmontosaurus’ fingers (and the mitten) be beneficial to the animal? It’s worth considering the evolution of horses as a point of comparison.
Extant horses have one hoof that covers a singular toe. Their ancestors started out with five toes, and lost them as time went . According to researchers, there appears to be some sort of correlation between the loss of toes and the increase in body mass. As horses got bigger, their side toes shrunk and their middle digits changed accordingly. This change allowed even larger horse species to evolve and stand on one toe successfully.
It’s not an exact one-to-one comparison, but we can consider the story of horse evolution as a starting point to contextualize Edmontosaurus’ hoof-like structure. In their prime, full-grown Edmontosaurus grew to sizes that rivaled that of Tyrannosaurus rex. Estimates suggest they could have grown more than 15 meters long and weigh between 10-15 tons. It’s entirely possible the mitten and keratinized sheath, which caused the hand to act more as a singular unit, might have developed in response to size and growth adaptations in Edmontosaurus.
There is a wrench in this idea, though. If the hands had evolved as an adaptation for load-bearing, this would put into question the gait of these animals. Paleontologists recognize Edmontosaurus as mainly bipedal with quadrupedal faculties. There are fossil trackways that seem to confirm this idea. However, this idea is not set in stone.
A study by Sellers et al. published in 2009 used computer models to evaluate different gait alignments for Edmontosaurus. The study did not definitively claim a quadrupedal gait was more likely, but it did argue that it should not be discounted. Although this is not a slam dunk, it provides room to question and investigate how these hadrosaurs moved around. Were Edmontosaurus spending more time on four limbs than previously thought? More research is necessary to unlock this mystery.
Dakota’s Future
Dakota certainly created a great deal of buzz online, and its unique preservation will continue to amaze and delight folks for years to come. The North Dakota Heritage Center will be unveiling its new exhibit for the fossil in 2020. Meanwhile, researchers are continuing to probe into the mysteries of the fossil. NDGS Paleo tweeted in December 2019 that the hand was brought to the University of Texas at Austin for CT scanning. One of the tweets explained how the resulting data will be used, saying:
“These CT data will allow us to correlate the soft tissue features on the surface with features of the bone underneath. Eventually, we will digitally segment out the bones in the scans and 3D print them so we can put a model of the bones right next to the real skin.”
They have since teased some images of the CT results, but it seems it will remain under wraps until more studies have been completed on the images.
There’s certainly a lot more that Dakota can tell us about Edmontosaurus, hadrosaurs in general, and the late Cretaceous. What we already know about the fossil is sensational. It is an invaluable contribution to the field of paleontology. We all should stay tuned to see what else Dakota will reveal to us in the future.
Thank you to NDGS Paleo, who were kind enough to let me use some of their images and write about Dakota. Go follow them on Twitter @NDGSPaleo.
Header image: ‘Edmontosaurus regalis, E. annectens’ by Abelov2014, Deviantart. (CC BY 3.0)
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References/Further Reading
Associated Press in Bismarck. “Dakota the Duckbilled Dinosaur, Aged 67 Million, Finds a Home in Bismarck.” The Guardian. Guardian News and Media, October 21, 2014. https://www.theguardian.com/us-news/2014/oct/21/dakota-ducbkilled-dinosaur-home-bismarck.
Choi, Charles Q. “Scientists Flesh Out Fossilized Tissues from Mummified Dinosaur.” Scientific American. Scientific American, June 30, 2009. https://www.scientificamerican.com/article/scientists-flesh-out-foss/.
Currie, Philip J., and Kevin Padian. Encyclopedia of Dinosaurs. San Diego: Academic Press, 1997.
“Dakota the Dinomummy.” North Dakota Heritage Center. Accessed February 21, 2020. https://statemuseum.nd.gov/exhibits/corridor-history/skylights/dakota.
“Dinosaur Mummy Found With Fossilized Skin And Soft Tissues.” ScienceDaily. ScienceDaily, December 3, 2007. https://www.sciencedaily.com/releases/2007/12/071203103349.htm.
Manning, Phillip L., Peter M. Morris, Adam Mcmahon, Emrys Jones, Andy Gize, Joe H. S. Macquaker, George Wolff, et al. “Mineralized Soft-Tissue Structure and Chemistry in a Mummified Hadrosaur from the Hell Creek Formation, North Dakota (USA).” Proceedings of the Royal Society B: Biological Sciences 276, no. 1672 (2009): 3429–37. https://doi.org/10.1098/rspb.2009.0812.
This blog needs updating with more posts.