Acila, H. Adams & A. Adams, 1858

Charles L. Powell, Ii, Clites, Erica C. & Poust, Ashley W., 2022, Miocene marine macropaleontology of the fourth bore Caldecott Tunnel excavation, Berkeley Hills, Oakland, California, USA, PaleoBios 36, pp. 1-34 : 6-7

ACILA H. & A. ADAMS, 1858

FIG. 5

covered by sediment, its valve shape is unlike that of a mature Acila . Still, the size and sculpture match well with Aci. empirensis Howe, 1922 and it is provisionally (cf.) identified as that species. Neontologists have synonymized Aci. empirensis under Aci. castrensis ( Bernard 1983, Valentich-Scott 1998, Coan et al. 2000), however molluscan paleontologists have kept the two species separate (Roth 1979, Moore 1983). Here we follow the paleontologists view until a detailed study of modern and fossil specimens can be performed. Acila empirensis has only been reported from the Wildcat Group in California (Ogle 1953) although both Faustman (1964) and Roth (1979) dispute this, citing Acila from the Wildcat Group as Aci. castrensis . However, Aci. empirensis has been found throughout the Pacific northwest. In Alaska it occurs in the middle Miocene Bear Lake Formation (Marincovich and Powell 1989, Detterman et al. 1996), the middle Miocene Tachilni Formation (Marincovich and Powell 1989, Detterman et al. 1996) and the Pliocene Milky River Formation ( Blodgett et al. 2008). In Canada it is known from the Miocene to possibly Pliocene Skonun Formation (White et al. 1994). In Washington State it is known from the Montesano Formation (Schenck 1936) and the Empire Formation of Oregon ( Howe 1922, Schenck 1936). The above occurrences indicate a middle Miocene to early Pliocene age for Aci. empirensis .

Figures

Figure 5. Acila cf. Aci. empirensis Howe, left valve. Tsm Caldecott Tunnel fauna. Hypotype from UCMP locality IP13003, UCMP 410923.