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80 & Contributions in Science, Number 520 Squires: Pico Formation Paleontology

Figures 4–8 Selected outcrops of the megafossiliferous, shoreface storm-lag deposits in the upper part of the Pico Formation in the Newhall area. 4.
Channel, filled with fossils, vicinity of LACMIP locality 17913, pencil 13 cm length. 5. Channelized lens of fossils, pebbles, and small cobbles, vicinity of
LACMIP locality 7757, hammer 32.5 cm length. 6. Top of channel fill with pectinid fragments, cobbles, and a complete Zonaria (Neobernaya) spadicea
(Swainson, 1823) (same specimen shown in Figs. 68, 69), LACMIP loc. 7752, pencil 13 cm length. 7. Part of a lens of Turritella cooperi showing
bimodal-preferred orientation, LACMIP loc. 7752, scale bar 15 mm. 8. Part of a fossiliferous lens with valves of Argopecten invalidus and scattered
pebbles, LACMIP loc. 7757, scale bar 20 mm.

relative stratigraphic positions are shown on Figure 2, are from The species found at the greatest number of localities and in
an interval approximately 130 m thick in the upper part of the the greatest numbers, are the following: Turritella cooperi
shoreface facies west of the Beacon Fault. This interval contains Carpenter, 1864, Argopecten invalidus, Calicantharus humer-
scattered lenses of megafossils. The species and their relative osus (Gabb, 1869), Glossaulax reclusiana (Deshayes, 1839),
abundance are listed in Table 1, along with information about Myrakeena veatchii (Gabb, 1866), and Here excavata (Carpen-
the occurrence of paired valves of the bivalves. The listed ter, 1857). Paired valves are common, especially for Argopecten
megafauna consists of 83 species: one brachiopod, 36 bivalves, invalidus, Myrakeena veatchii, Trachycardium (Dallocardia)
40 gastropods, one scaphopod, one crab (partial leg), one quadragenarium (Conrad, 1837), Callithaca tenerrima (Carpen-
barnacle, one sea urchin (spine), one shark (ray tooth), and one ter, in Gould and Carpenter, 1857), Saxidomus nuttalli Conrad,
land plant (pine cone). All these taxa are illustrated here (Figs. 9– 1837, Tresus nuttallii (Conrad, 1837), and Panopea abrupta
106). The ray tooth and pine cone occur together in the same (Conrad, 1849).
hand specimen. A few epibionts were also found but are badly
weathered: some small patches of an encrusting bryozoan and SYSTEMATICS
some minute tubes of an encrusting annelid (spirorbid) were
detected on the same brachiopod specimens from LACMIP Phylum Mollusca Linnaeus, 1758
loc. 17918. These poorly preserved taxa are not illustrated here Class Bivalvia Linnaeus, 1758
because of their very limited taxonomic information. Boreholes Family Pectinidae Rafinesque, 1815
are scarce. Those made by sponges? or algae? are present on some Genus Argopecten Monterosato, 1889
oyster valves, those made by predatory gastropods occur on a Argopecten Monterosato, 1889:20
few bivalves. Preservation differs greatly among the mollusks. Plagioctenium Dall, 1898:696
Calcitic pectinids, oysters, and turritellas are well preserved,
whereas aragonitic mollusks are commonly poorly preserved due TYPE SPECIES. Pecten solidulus Reeve, 1853, by subsequent
to weathering. Some of the very weathered, small-sized mollusks designation (Monterosato, 1899:193) 5 Pecten ventricosus G.B.
are especially prone to disintegration upon touch. Sowerby II, 1842, not Pecten circularis G.B. Sowerby I, 1835