By Nora Lowe
Beneski Natural History Museum is a treasure trove that houses skeletons, minerals, and even meteorites. However, Beneski’s hidden gem is past the picturesque mammoth skeleton, down the stairs, and around the corner, where an unassuming room actually boasts one of the world’s largest collections of fossil dinosaur tracks.
As the Museum Educator, Alfred Venne is an enthusiastic spokesperson for these ancient objects. His job is to make the exhibit accessible for all types of audiences, including those with limited background knowledge. On a recent October afternoon, Venne did just that, inviting an ASN reporter (myself) into the collection for a generous crash course in ichnology (the study of fossilized tracks) as it relates to the backstories of some of his favorite items.
Read on to learn more about the track room from your own living room.
Stop 1: The Track-Book
Pictured here is a replica of a track-book, the real version of which is mounted on the wall above. Venne explained that every rock in the exhibit used to be mud, and when the mud dried, a microbial layer on top died. That material provided some integrity to the dried mud and would sit through the dry season. The next wet season would deposit a new layer of mud on top, and the cycle would begin anew. This iterative process refers to what Venne called “the right kind of deposition.” With proper sediment layering, an animal’s impact is captured and recorded. If the impact made by the creature gets buried deep enough, the whole entity lithifies, or turns to stone. Luckily for us, these same layers of deposition that preserved the tracks so beautifully can be peeled apart like pages of a book with a knife and hammer. The aforementioned layer of microbial material then becomes “a plane of fracture.” Venne likened it to writing on carbon copy paper.
The end result is two-fold: an impression and a natural cast. The impression is the mineralized impact an organism left behind. By contrast, a cast is formed when sediment fills in that mold and recreates the negative space’s shape. Venne said a young child visiting the museum once came up with a perfect analogy — the impression is like an “innie” belly button, and the cast is like an “outie.” With those bases covered, we were ready to venture further into the collection.
Stop 2: Raindrop Impressions
This item originated in South Hadley, which Venne joked is “literally a stone’s throw” away. It has more to tell than meets the eye, providing helpful indicators about the era’s climate. These “crater markers” captured a singular, specific event. We know this because if it had rained continuously, the marks would have been washed away. In fact, you can even tell which direction the wind was blowing based on the lips around each drop’s impression. Additionally, we can observe there are raindrop impressions inside the footprints themselves. This means the creature had to have walked this way before it started raining. After the rain, the sun quickly dried it, and it sat for months, suggestive of a dry season. When the next wet season finally arrived, Venne supposed “all the nooks and crannies were filled in, protecting it under layers of mud and more sediment until it finally lithified.”
Importantly, a number of factors created the climatic conditions for mud to accumulate. When supercontinent Pangea split apart about 200 million years ago, Europe and Africa moved off one way, while North America moved the other, leaving the Atlantic Ocean to fill in between. However, in some places, a failed rift formed when the separation wasn’t complete. This created a valley, like the Pioneer Valley we’re in, where mud could collect.
“And it just happened that mud was collecting at the same time dinosaurs were around,” Venne noted.
Stop 3: Interference Ripple Marks
Interference ripple marks are formed when shallow water, such as from a pond or small lake, dries out. Simultaneously, winds blow from one direction, pushing water up against the lakeside before it bounces back. “These standing waves go back and forth,” Venne clarified. Just like with raindrop impressions, those ridges get filled in and buried during the wet season. Splitting along its layer of deposition as per usual, we get the visible impression and cast.
Stop 4: Sidewalk Slabs
These two squares were cut to be sidewalks in Greenfield, just twenty minutes north of the College. The town was installing their first-ever sidewalks when a young man named Dexter Marsh noticed these curious marks. He decided to consult the town doctor, James Dean, in 1835, who surmised they were footprints. He, in turn, brought it to the state geologist who happened to be Amherst College professor Edward Hitchcock.
Hitchcock started out looking in the substrate for bones, but they hadn’t survived exposure to wet-dry seasons. When Pangea split, New England was left with footprints, but the more moist environment in England was conducive to preserving both bones and footprints. We can match them up pretty well, which explains why the dinos depicted in the collection are actually from across the Atlantic in England.
In terms of direct clues beyond footprints, though, Hitchcock did find coprolite (a.k.a. fossilized poop), which had the same chemical signature as bird poop. Therefore, Venne summarized, “Hitchcock believed he had bird scat and bird footprints, thus evidence of ancient birds.” The word dinosaur hadn’t even been coined yet, after all.
Relatedly, Nancy Pick (‘83) wrote a book on Hitchcock entitled Curious Footprints: Professor Hitchcock’s Dinosaur Tracks & Other Natural History Treasures at Amherst College. In it, she investigates his loyalty to the bird hypothesis, an idea eventually “tossed on the sea of difficulty” (Pick p. 4). Venne joked that Hitchcock nevertheless deserves some credit: “science suggests today that the last living dinosaurs are birds. So Hitchcock was on the right track.”
More broadly, Hitchcock is the reason we have today’s distinguished track collection in the first place. Hitchcock amassed upwards of 1,200 slabs, with over 10,000 marks that he worked to identify, including 50 ichnospecies. In his time, he also communicated with Darwin.
Hitchcock, as the third president of the College, wanted to sustain his legacy by storing the track-list in what is now Appleton Dormitory. Post-WWII, the tracks moved to Charles Pratt, which was then the campus’ Earth Sciences and Museum building. Finally, the collection moved to Beneski in 2006. Many of the items are mounted as shown to minimize points of contact and thus stress. However, some researchers bring their own lighting, as different angles make different details visible. Venne recalled one scientist even using the equivalent of an engine hoist to lift a slab to position it for three-dimensional rendering, which involves taking about one thousand images.
You might be wondering why the collection hasn’t grown substantially since Hitchcock’s time. The answer is most work is done in situ now, so we can document a site using 3D imagery. Whereas in the past, “everything was pulled out of the ground.”
“There wasn’t as much effort to study it in place” as there is today.
Stop 5: Trace Feather Marks
Modern research on these items really began in the 20th century. Paul Olson from Columbia University, whom Venne described as a “foremost authority on ichnology,” published on feather marks in the sample pictured above: one of the earliest indicators of feathers in the fossil record.
“The small keel and striations off the side suggest feather marks,” Venne elaborated. This salient, landmark study implied dinosaurs were warm-blooded and indeed performed thermoregulation.
By and large, we should care about these fossils in Venne’s eyes because they illuminate the past. They lend intel on ancient climates (i.e., paleoclimates) as well as the life and behaviors of individual organisms.
“You can see where these critters were sitting, where they were swimming, where they were playing, if they were moving slow or fast, if something rolled around, and how they interacted, among other things,” Venne emphasized. “You can actually get a sense of a moment in time.”
Visit the museum to inspect the items mentioned for yourself! Beneski’s hours are:
- Tuesday – Friday, 10 AM – 4 PM
- Saturday – Sunday, 10 AM – 5 PM