Miocene marine macropaleontology of the fourth bore Caldecott Tunnel excavation, Berkeley Hills, Oakland, California, USA Author Charles L. Powell, Ii Author Clites, Erica C. Author Poust, Ashley W. text PaleoBios 2022 36 1 34 journal article 10.5070/P9361044567 0031-0298 13750345 EFED8DE6-E976-43A5-BD7B-F478EF0B6FF9 MAMMALIA INDET. FIG. 34 UCMP 270019 and 270092 are partial mid-shaft fragments of what appear to be pinniped ribs. They resemble pinniped ribs in cross-sectional shape and marrow cavity area, but we cannot fully rule out small odontocete cetaceans with ribs of similar size. Possible candidate taxa for these elements include the smaller early imagotariine walruses, enaliarctine pinnipedimorphs, now known to survive along the West Coast as late as 16.6 Ma (Poust and Boessenecker 2018), and a number of smaller cetacean taxa. Due to the age uncertainty of the Tsm at this locality, the size overlap among the ribs of multiple marine mammal taxa, and the minimal anatomy preserved we feel this justifies only attribution to the Mammalia .