Where: Peru (14.4° S, 75.9° W: paleocoordinates 15.3° S, 71.8° W)

When: Chilcatay Formation, Burdigalian (20.4 - 16.0 Ma)

• The holotype of M. ukupachai MUSM 2545 was discovered in the Chilcatay Fm, dated from the latest Oligocene to the earliest Middle Miocene on the basis of diatoms, foraminifers and molluscs [34–37]. In the Western Ica Valley area, the age of this formation can be constricted to the Early Miocene (approx. 19–18Ma), through biostratigraphic and 40Ar/39Ar analyses ([20,22], new data). The age of MUSM 2545 is here further constricted to 18.78 ± 0.08 Ma (early Burdigalian) on the basis of a volcanic ash layer sample dated by 40Ar/39Ar. Although the fragmentation of outcrops (characterized by small isolated patches of Chilcatay Fm) in this area of the Pisco Basin did not allow for a precise correlation of the horizon of the M. ukupachai holotype with the dated ash layer, strong similarities between the lithologies outcropping in the two areas and especially the discovery near the ash layer of another (uncollected) skeleton most likely belonging to the same species as MUSM 2545 supports the age of 18.78 ± 0.08 Ma provided for the M. ukupachai holotype.

Environment/lithology: marine; diatomaceous siltstone

Size class: macrofossils

Primary reference: G. Bianucci, G. Bosio, E. Malinverno, C. Muizon, I. M. Villa, M. Urbina, and O. Lambert. 2018. A new large squalodelphinid (Cetacea, Odontoceti) from Peru sheds light on the Early Miocene platanistoid disparity and ecology. Royal Society Open Science 5(4):172302 [M. Uhen/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 192828: authorized by Mark Uhen, entered by Mark Uhen on 20.04.2018

Creative Commons license: CC BY (attribution)