Recently Fred Croxen wrote me the following:
I???m a professor of geosciences at Arizona Western College in Yuma, Arizona. I recently returned from a vacation in Ecuador and while I was exploring the western coast I visited Isla de la Plata, an island about 40 km west-northwest of Puerto Lopez. See image below:
While touring the island I came upon an excavation that workers were digging for trail maintenance. In the wall of the excavation were exposed land snail shells. The shells appeared to be buried between 1.5 to 3 meters below the former surface in several horizons. The sediments were a mix of alluvial and colluvial deposits in a steep canyon. I have attached an image of the site. The guide informed me that these snails were introduced by early peoples. I???m not sure of the validity of that claim. The shells are definitely old but probably not fossil sensu strictu. In any event, I salvaged one of the shells of which I supply images.