2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 193-7
Presentation Time: 9:45 AM

LATE MIOCENE CHONDRICHTHYANS FROM LAGO BAYANO, PANAMA WITH IMPLICATIONS FOR A MARINE CONNECTION BETWEEN THE CARIBBEAN AND PACIFIC


PEREZ, Victor J., Geological Sciences, University of Florida, Gainesville, FL 32611, PIMIENTO, Catalina, Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, HENDY, Austin J.W., Natural History Museum of Los Angeles, 900 Exposition Blvd, Los Angeles, CA 900007, MACFADDEN, Bruce J., Florida Museum of Natural History, University of Florida, PO Box 117800, Gainesville, FL 32611, GONZALEZ-BARBA, Gerardo, University of Baja California Sur, La Paz, 23080, Mexico and HUBBELL, Gordon, Jaws International, Gainesville, FL 32611, victorjperez@ufl.edu

This novel description of the chondrichthyan fauna of the late Miocene Chucunaque Formation in Lago Bayano, Panama reveals a prolific and highly diverse assemblage. Extensive field efforts resulted in 1426 identifiable dental remains and six non-dental elements; comprising at least 38 taxa, of which at least 12 are new to the documented fossil record of Panama. Comparisons with modern analogs indicates a littoral environment dominated by generalist species (~73%) characterized by having a cutting-grasping type dentition, and a surprisingly large component of mobulid rays (~12%) specialized for filter-feeding. A weighted paleobathymetric analysis estimates a mean average depth of 99 m with a mean maximum depth of 195 m. Previous studies have suggested that the Chucunaque Formation of Lago Bayano had a greater Pacific Ocean affinity based on foraminifera, making this the first Miocene chondrichthyan fauna described from the Pacific shelf of Panama and, consequently, a pivotal piece of evidence in the controversial history of the Central American Seaway. Among the 38 identified taxa, at least 20 bear a morphology comparable to extant species; of which 15 have mixed biogeographic distributions in the present-day Atlantic and Pacific, three are restricted to the Atlantic, and two are restricted to the Pacific. Roughly contemporaneous Caribbean-affiliated fauna, such as that of the Gatun Formation and Alajuela Formation, also exhibit chondrichthyan assemblages with mixed biogeographic affinities; which provides support for the previously purported seaway, ~9 to 10 million years ago, connecting the Pacific Ocean to the Caribbean Sea.
Handouts
  • MeasuringMeg_GSAposter.pdf (1.7 MB)
  • GSA2015_BayanoSharks.pdf (2.4 MB)