Latest Pacific Basin record of a bony-toothed bird (aves, Pelagornithidae) from the Pliocene Purisima Formation of California, U.S.A.

Abstract

ABSTRACT Fossils of pelagornithids (bony-toothed birds) have been reported from strata of Paleocene to Pliocene age, and from every continent. The extreme fragility of pelagornithid bones has no doubt contributed to their geographically and temporally sporadic record, and thus it has been difficult to appreciate any long-term phylogenetic trends through geologic time for this group. We report a well-preserved partial humerus of the gigantic bird Pelagornis from the late Neogene Purisima Formation of central California. Due to its incompleteness, we refrain from naming a new species. This fossil is fortuitously bracketed by two ash beds, which have been correlated with volcanic rocks at 3.35 ± 0.05 Ma and 2.5 ± 0.2 Ma, indicating a middle to late Pliocene age for this fossil. This fossil extends the record of the pelagornithids in the Northeast Pacific, previously only known up until the early late Miocene (10–12 Ma). This fossil is the latest record of a pelagornithid for the Pacific Basin, and additionally represents the latest reliably dated pelagornithid record worldwide. This record suggests that the pelagornithids survived until the end of the Pliocene, and became extinct during the ocean restructuring and climatic upheavals that caused the demise of many other groups of marine vertebrates at that time.