For Fossil Friday this week here’s a couple of pygmy sperm whale earbones from the recently acquired Rita McDaniel collection at the Mace Brown Museum of Natural History. McDaniel led mine tours into the Lee Creek Mine (Aurora PCS phosphate mine, North Carolina) for many years, and collected a substantial amount of fossil material from the middle Miocene Pungo River Limestone and the younger overlying lower Pliocene Yorktown Formation. The Yorktown Formation has produced one of the most important assemblages of Pliocene marine vertebrate fossils worldwide and is an important point of comparison for students of shark, fish, seabird, seal, and cetacean evolution.
The modern dwarf and pygmy sperm whales (Kogia simus and Kogia breviceps) are tiny sperm whales clocking in at only 2.5-3.5 meters long (approximately the size of a bottlenose dolphin), a fraction of the size of the more publicly known giant sperm whale (Physeter macrocephalus ) of Moby Dick fame (20 meter length). Both species of Kogia are rarely seen alive, and little information is known about their behavior or ecology. Similar to the extant giant sperm whale the fossil record includes many other extinct genera within the family Kogiidae and demonstrates that they evolved from somewhat larger ancestors, with a higher diversity in the late Miocene and Pliocene.
At the Lee Creek Mine, a larger kogiid whale is known from a well-preserved skull from the Pliocene Yorktown Formation – Aprixokogia kelloggi – which primitively retained upper teeth. When this species was named, hundreds of isolated well-preserved inner ear bones (periotics/petrosals) were also known, but not associated with the skull. Because of the lack of overlapping parts, the earbones were simply identified as Kogiidae indeterminate. These earbones are quite a bit larger and more robust than extant Kogia spp., which has dainty little periotics.
A new study published by Jorge Velez-Juarbe, Aaron Wood, and Catalina Pimiento reevaluates kogiid earbones from the Yorktown Formation of North Carolina and Bone Valley Formation of Florida, and reports previously unrecognized periotics of modern Kogia from the Yorktown Formation, preserved side-by-side with a larger, less modernized pygmy sperm whale (Aprixokogia). These earbones of Kogia are much more rare than the larger variety, and we were lucky enough to receive one of these in our recent donation. Check out our earbone of Kogia side by side with the larger unidentified kogiid – a puzzle answered by this new paper from our colleagues!
Jorge Vélez-Juarbe, Aaron R. Wood & Catalina Pimiento (2016): Pygmy
sperm whales (Odontoceti, Kogiidae) from the Pliocene of Florida and North Carolina, Journal
of Vertebrate Paleontology, DOI: 10.1080/02724634.2016.1135806 [Full Article]