Field Season 2015
In the footsteps of A.S. Romer: filling a 20 million year gap in tetrapod evolution
The evolution of tetrapods (four-legged animals) from fish-like precursors was a pivotal event in Earth's History, with repercussions that still thunder today. Exactly when and how tetrapods left the water for life on terra firma is still, however, poorly understood. Our lack of resolution around this major transition stems from a sparse fossil record for ~20 million years at the commencement of the Carboniferous Period (Mississippian series, 360-340 million years ago) - an interval historically designated 'Romer's Gap' after the eminent Harvard paleontologist A.S. Romer. It has been argued that the fossil gap is a ramification of low atmospheric oxygen levels during the early stages of the Carboniferous, which precluded tetrapods from exploring land environments. But, the recent discovery of significant numbers of fossil sites in Scotland (as well as Nova Scotia), suggests Romer's Gap may be the result of a collection bias. Please visit the TW:eed Project to learn more about Romer’s Gap and the Scottish material.
In the summer of 2015, the Pierce Lab worked in collaboration with Cambridge University and the TW:eed Project to explore early Carboniferous outcrops in West Virginia, USA, in the hopes of further filling in Romer’s Gap and expanding our knowledge of early tetrapod evolution in the Americas. In the early Carboniferous, West Virginia sat in a basin that saw continuous sedimentary deposition and today is home to extensive rock outcrop, making it a prime location for the potential discovery of tetrapod fossils. In fact, evidence already exists in the MCZ Vertebrate Paleontology Collections that tetrapods were roaming the West Virginia landscape over 300mya. In the 1950s, A.S. Romer sent out a field crew to explore West Virginia and they collected an assortment of fossils; unfortunately, the specimens remained dormant in cabinet drawers for over half a century.
Using the detailed 1950s field notebook as a framework, we followed in the footsteps of A.S. Romer in an attempt to rediscover the old localities in West Virginia and further explore the miles of outcrop across the state. The 2015 field team was led by Stephanie E. Pierce (MCZ, Harvard) and consisted of Carboniferous tetrapod expert Timothy Smithson (Zoology Museum, Cambridge), geological conservator Sarah Finney (Sedgwick Museum, Cambridge) and geologist Gordon Baird (New York at Fredonia). The expedition took the team across the West Virginian mountains, countryside and gorges for 2.5 very hot and humid weeks. The '15 team rediscovered many of the old localities, plus a number of new fossil sites, in addition to meeting a range of amazing and supportive local enthusiasts.
Please watch this space for updates as we process the new fossil material.
We thank the MCZ and the Putnam Expedition Grant for funding this paleontological field work. And special thanks to local geologist and fossil enthusiast Bob Peck.
Famous Sideling Hill outcrop that encompasses the Devonian-Carboniferous boundary.
All images copyright Stephanie Pierce