Where: Panama (9.3° N, 80.0° W: paleocoordinates 9.1° N, 79.1° W)

• coordinate stated in text

When: Chagres Sandstone Formation, Messinian (7.2 - 5.3 Ma)

• Microfossils place the Chagres Formation in calcareous nanofossil zone NN11 and planktonic foraminiferal zones M13b-M14, suggesting an age range between 8.52 to 5.57 Ma, i.e., Tortonian to Messinian in age (Collins et al., 1996). Hendy et al. (in press) obtained a Sr date of ∼7.64 Ma from a single mollusc shell that was collected stratigraphically below the unit where the type specimen of Isthminia was discovered. This result, however, conflicts with planktonic foraminiferal data. The top of the Toro Point Member of the Chagres Formation includes co-occurring Globorotalia margaritae Bolli & Bermu ́dez, 1965 and G. lenguaensis Bolli, 1957. Collins et al. (1996) indicating an astronomically calibrated age (Wade et al., 2011) of 6.13–6.08 Ma. Globoquadrina dehiscens Chapman, Parr & Collins, 1934 has an age range of 23.2–5.8 Ma (Wade et al., 2011) and occurs throughout the stratigraphic section, including Panama Paleontology Project locality (PPP) 1099 (Collins et al., 1996), which is located less than 1 kilometer from STRI locality 650009, and coeval with the type specimen of Isthminia. Because the Pin ̃a Facies is stratigraphically above the Toro Member in the Chagres Formation, these observations therefore constrain the age of the type specimen of Isthminia to 6.1–5.8 Ma (Messinian).

Environment/lithology: marine; lithology not reported

Size class: macrofossils

Primary reference: N. D. Pyenson, J. Velez-Juarbe, C. S. Gutstein, H. Little, D. Vigil and A. O'Dea. 2015. Isthminia panamensis, a new fossil inioid (Mammalia, Cetacea) from the Chagres Formation of Panama and the evolution of ‘river dolphins’ in the Americas. PeerJ 3:e1227 [M. Uhen/M. Uhen/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 172931: authorized by Mark Uhen, entered by Mark Uhen on 01.09.2015

Creative Commons license: CC BY (attribution)