Plate Tectonics 100 Year Anniversary
This year marks the centennial anniversary of the theory of plate tectonics with the publication of “The Origin of Continents and Oceans” by German explorer and geophysicist Alfred Wegener, now a true legend. His data-driven hypothesis and analyses were highly criticized and discounted by entrenched mindsets, and mostly forgotten until the 1960s. The fossil record, generally, and trilobites, particularly played a pivotal role in mapping drfting, collisions and breakups of continents across geologic time. How the theory all came together is summarized in a 2013 Nature paper: Naomi Oreskes, Nature 501, 27–29; 2013.
The two trilobites above are, respectively, Dicranurus hamatus elegantus, from the Haragan Formation, Coal County, Oklahoma, and Dicranurus monstrosus, from the Laatchana Formation deposits near Alnif, Morocco. Both fossil sites are dated to the lower Devonian period about 400 million years ago. Their resemblance is nothing short of remarkable, despite now separated by the Atlantic Ocean and more than 4000 miles. The similarity is because the Morocco of today was in the continental shelf of Gondwana during the Devonian, and Oklahoma was in the continental shelf of Euramerica (also called Laurussia), separated by the Paleotethys Sea (as shown here); these landmasses were drifting together as the supercontinent Pangaea was forming. The fossil sites were thus proximal and at comparable latitudes, suggesting they shared the same marine environments. The comparable species likely share common ancestry and occupy the same or closely related genera. Are they the same species – could they interbreed? Who knows, at a minimal, they share a very close common ancestor. What a difference a century made for Alfred Wegener.
Still not convinced about plat tectonics? There are many examples of DEvonian trilobite commonality between Morocco and Oklahoma among diverse trilobite orders: Lichida; Phacopida; Proetida; and Corynexochida. Maybe I’ll pst those here another day. Of course, some folks will never be convinced, think the Earth is but 10,000 years old, that humans and dinosaurs co-existed, and all that rubbish – well, denial is not just a river in Egypt.