Archive for June 10th, 2016

Team Dorset finishes its fieldwork

June 10th, 2016

1 Snuffbox serpulidssSherborne, England — Cassidy Jester (’17), Tim Palmer and I today finished our fieldwork. Cassidy is now set for her Senior Independent Study project with plenty of specimens, observations, photographs and ideas to last the next 10 months. This morning we visited the Burton Bradstock beach exposure of the snuffboxes, meeting our great colleague Caroline Buttler (Department of Natural Sciences, Amgueddfa Cymru – National Museum Wales, Cardiff) and her husband Simon for lunch on the outcrop. It was great fun, and Caroline had additional discoveries for us, including the exfoliated snuffbox layer shown above with serpulid worm tubes.

2 Ammonite gastropod snuffboxesWe had time to look for more fossils associated with the snuffboxes. Above you see a gastropod on the left and an ammonite on the right, with snuffbox bits scattered about.

3 Burton Bradstock pendentWe also found many examples of burrow systems with cryptic pendent iron-rich layers, including those shown above. (I rotated the image 180° because the block we studied on the beach is upside-down.)

4 Maiden Castle rampartsOn the way back to our lodgings near Sherborne we stopped by the Iron Age hill fort Maiden Castle, a portion of the massive earthen ramparts of which are shown above.

Our collecting, measuring and describing is done. Most of the work for this project, of course, will be in the Wooster geology labs. We will have delightful memories of our sunny days in Dorset, and the invaluable assistance of our colleagues Bob Chandler and John Whicher. I am personally most grateful for the geological and navigational skills of Tim Palmer, our wonderful companion and astute advisor. Without him none of this could be done.

Crew in Whicher MuseumThe Dorset crew in the Whicher Museum. From the left, Bob Chandler, Mark Wilson, Tim Palmer, John Whicher, and Cassidy Jester (’17).

Wooster’s Fossil of the Week: A fracture-shaped bioerosion trace from the Pliocene of Cyprus

June 10th, 2016

Caedichnus_01_scale_Mark 500This past semester I worked with three colleagues on a massive trace fossil review paper, which we hope meets success in the next month or so. My primary job on the team was to sort out bioerosion traces, especially those that are macroscopic. As always with such studies, I learned a great deal when forced to do a systematic literature review. One of the ichnogenera new to me was Caedichnus, a wedge-shaped excision found primarily in gastropod shells. It was only described last year by Stafford et al. (2015). Above is an example we happened to have in our collections. Note the fractured margins in this Fusinus shell aperture from the Pliocene of Cyprus. It was likely made by a predatory crustacean (such as a crab or lobster) bashing away at the shell to get to the living snail inside. The predator may have been successful in this case since there is no sign of healing in the snail shell.
Fusinus Cyprus Pliocene 500Above is an undamaged Fusinus showing a complete aperture. This snail also had its travails, though. Note the round, incomplete borehole just above the aperture. This was made by some kind of drilling predator, likely a naticid snail.

These shells come from the 1996 Wooster-Keck expedition to Cyprus with Steve Dornbos (’97) and me. Like the rest of the Cypriot specimens on this blog, it is from the Nicosia Formation (Pliocene) exposed on the Mesaoria Plain in the center of the island. This specimen comes from the “Exploration” locality described in Dornbos and Wilson (1999).

References:

Dornbos, S.Q. and Wilson, M.A. 1999. Paleoecology of a Pliocene coral reef in Cyprus: Recovery of a marine community from the Messinian Salinity Crisis. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 213: 103-118.

Molinaro, D.J., Stafford, E.S., Collins, B.M., Barclay, K.M., Tyler, C.L. and Leighton, L.R. 2014. Peeling out predation intensity in the fossil record: A test of repair scar frequency as a suitable proxy for predation pressure along a modern predation gradient. Palaeogeography, Palaeoclimatology, Palaeoecology 412: 141-147.

Stafford, E.S., Dietl, G.P., Gingras, M.P. and Leighton, L.R. 2015. Caedichnus, a new ichnogenus representing predatory attack on the gastropod shell aperture. Ichnos 22: 87-102.

Stafford, E.S., Tyler, C.L. and Leighton, L.R. 2015. Gastropod shell repair tracks predator abundance. Marine Ecology 36: 1176-1184.