The Silurian Reef
By Sue Lawton
The old limestone quarry in the town where I grew up was an enticing playground for a nature-obsessed introvert. I spent many happy hours scrambling up mounds of limestone chunks and tromping along the riverbank and ponds of the park, picking up rocks and frogs and finding ancient treasures. Given that it was previously used as a landfill, some of the treasures were old tires and very outdated soda cans. But others were clearly much older. Much, much older.
I collected a few fossils here and there, secretly hoping some of them were parts of dinosaurs, despite the fact that many were clearly seashell-shaped. One in particular had a scaly texture I thought might be dinosaur skin. However, with the invention of the internet, I eventually found pictures of similar fossils and was finally able to identify most of what I found as chorals and other reef organisms from the Silurian. My dinosaur quarry was actually the remains of a tropical sea, which seemed fantastical given the weather in Wisconsin. When I was very small, Lake Michigan, in my mind, was an ocean. Adults frequently corrected me, saying it was lake. Now, as it turned out, there had been an ocean there after all. Just a few hundred million years in the past.
Fossils from MPM’s collection (Left) and fossils from Sue’s personal collection (Right) which are very definitely not dinosaurs.
I was still disappointed at the lack of Wisconsin dinosaurs, which had apparently been eaten up by glaciers. The museum was still the only place to see dinos. But interestingly, as one snakes through the Third Planet exhibit, there is also a lovely reconstruction of a Silurian Reef based on Wisconsin’s fossils. The diorama, complete with watery rippling light, is filled with corals, sponges, crinoids, and trilobites. I sadly never found any trilobites in that old quarry, but did find one in a creek bed in a neighboring town.
It is wonderful to sit on the long, carpeted bench across from the reef diorama and just take it in. The soft whirring of the light rippling mechanism fills the space, as families wander past, not noticing the quiet person sitting there in the dark. A large, cone-shaped nautiloid (orthoceras) silently grabs an unfortunate trilobite in its tentacles. If you stare at it long enough, the crinoids almost seem to sway in the gentle waves. Almost.
A mesmerizing scene filled with peaceful sea life, and also some nightmare creatures that can best be described as cornucopias of terror.
Some Observations and Responses from Ven:
During my time collecting specimens in the Milwaukee area, the beaches have been a bountiful source of minute curiosities. In the sands of Bradford Beach and Doctor’s Park, the sheer quantity of small objects, both naturally occurring and human in origin, is impressive and an endless source of inquiry. For example, among the sand grains, one finds thousands of black and white striped shells from extant species of mussels. These are apparently not originally lake dwellers, but ocean invaders brought in on ships and recreational water craft. There are so many shells that their broken shards mix to an almost indistinguishable texture within the sand. Within this mixture, tiny, rock disks can be discerned, along with a mishmash of stranger shapes. After consulting a local geologist, it seems they are remnants of ancient species of crinoids and bryozoans. These were also ocean organisms, but they lived hundreds of millions of years before the zebra mussel invasion. It presents an interesting juxtaposition; the quantity of ancient crinoids must have rivaled the current populations of mussels. Perhaps in another hundred million years, some other scientist or collector will come upon the zebra mussel fossils and wonder if this was once an ocean. It would be fun to see what diorama the future fossils inspire; would it include reconstructions of the broken beer bottle fragments along with the colonies of mussels?
Looking at the Silurian Reef diorama at MPM helps to complete the picture of the city’s past. Or one of its pasts at any rate. As for my own collections, I’ve opted to display the fossils in a glass-topped case and have made illustrations of the crinoids and bryozoans. One day, when the rift is repaired, I will take these collections back to Damos Nuhl to be housed in the museums of my homeland. A complete comparison study of earth organisms and those of Nuhl would yield exciting results, especially into the subject of convergent evolution. I believe we have something very similar to trilobites, but need a closer look at the fossils to be sure.
A page from Ven Loetz’s field journal, written in Hwalkan.