CSUN Loc. 548, Simi Arroyo (Eocene of the United States)

Where: Ventura County, California (34.3° N, 118.7° W: paleocoordinates 35.0° N, 104.7° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Llajas Formation, Lutetian (47.8 - 41.3 Ma)

• Immediately below the "Stewart Bed", middle of the Llajas Formation, "Domengine" stage, top of CP12a calcareous nannoplankton zone, lower Lutetian stage, Middle Eocene, C21r chron.

• bed-level stratigraphic resolution

Environment/lithology: transition zone or lower shoreface; lithified, argillaceous siltstone and bioturbated sandstone

• The "Stewart bed" is located in a section of transition from shallow-marine to outer slope and shelf facies. A nearshore environment is interpreted for that portion of the shallow-marine (transgressive) facies which consists of laminated beds alternating with bioturbated beds. In such cases, the finely laminated sand represents storm-influenced stratification, and the biogenic reworking is the inter-storm activity. Shell fragments commonly are concentrated as channel lags in surge channels. Fossils were apparently subjected to wave action because the apices of elongate shells such as Turritella are bimodally oriented in opposite directions. The deeper the water, the less amount of laminated sandstone and the more amount of bioturbated sandstone. Such areas, which were farther below effective wave base, existed 1) where the shallow-marine (transgressive) facies grades into the outer shelf to slope facies and 2) in the shallow-marine (regressive) facies. One of the deepest-water shallow-marine beds was the "Stewart bed."
• Alternating laminated and bioturbated sandstones grading into muddy siltstone.

Size class: macrofossils

Preservation: mold/impression

Reposited in the LACM

• Collected by R.L. Squires, (1978) and CSUN paleontology classes in the 1980's-1990's and G. Slak (1997-1998)

Primary reference: R. L. Squires. 2001. Additions to the Eocene megafossil fauna of the Llajas Formation, Simi Valley, southern California. Contributions in Science (Natural History Museum of Los Angeles County) 489:1-40 [A. Miller/A. Hendy/A. Hendy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 51922: authorized by Austin Hendy, entered by Austin Hendy on 04.07.2005, edited by Jonathan Marcot and Patricia Holroyd

Creative Commons license: CC BY (attribution)

Taxonomic list

• Exhaustive for mollusca, corals, arthropoda, and includes other groups where obvserved; list compiled from meticulous search of the invert collections at the LACM, private collections and fieldwork.
Malacostraca
 Decapoda - Scyllaridae
Parribacus caesius n. sp. Squires 2001 decapod
 Decapoda - Cymonomidae
Eonomus californianus n. gen. n. sp.1
Eonomus californianus n. gen. n. sp.1 Nyborg et al. 2017 crab
 Decapoda - Raninidae
Raninoides slaki n. sp. Squires 2001 crab
 Decapoda - Panopeidae
Glyphithyreus weaveri2 Rathbun 1926 crab
 Decapoda - Macropipidae
"Portunites insculpta" = Portunites insculptus
"Portunites insculpta" = Portunites insculptus Rathbun 1926 crab
Rhynchonellata
 Terebratulida - Terebrataliidae
Terebratalia aff. batequia Sandy et al. 1995
Bivalvia
 Ostreida - Flemingostreidae
"Ostrea idriaensis" = Acutostrea idriaensis2
"Ostrea idriaensis" = Acutostrea idriaensis2 Gabb 1869 oyster
 Ostreida - Pteriidae
Pteria pellucida Gabb 1864 pearl oyster
 Ostreida - Pinnidae
Pinna lewisi2 Waring 1914 oyster
 Carditida - Carditidae
Venericardia (Pacificor) hornii2 Gabb 1864 clam
as Venericardia (Pacificor) hornii calafia
 Cardiida - Gastrochaenidae
Gastrochaena ? dubitata Hanna 1927 clam
 Cardiida - Psammobiidae
"Gari texta" = Gari (Gobraeus) texta
"Gari texta" = Gari (Gobraeus) texta Gabb 1864 clam
 Cardiida - Cardiidae
"Nemocardium linteum" = Nemocardium (Nemocardium) linteum2 Conrad 1855 cockle
Gastropoda
 Neogastropoda - Turridae
"Fusiturricula (Crenaturricula) crenatospira" = Crenaturricula crenatospira2
"Fusiturricula (Crenaturricula) crenatospira" = Crenaturricula crenatospira2 Cooper 1894 turrid
as Fusiturricula (Crenaturricula) crenatospira domenginica
 Neogastropoda -
Domenginella claytonensis2 Gabb 1864 snail
 Stromboidea - Strombidae
Platyoptera pacifica Squires and Demetrion 1990 true conch
 Calyptraeoidea - Calyptraeidae
Calyptraea diegoana2 Conrad 1857 slipper shell
 Sorbeoconcha - Turritellidae
Turritella andersoni2 Dickerson 1916 turret shell
as Turritella andersoni lawsoni
Turritella uvasana2 Conrad 1865 turret shell
as Turritella uvasana applinae
Turritella buwaldana2 Dickerson 1916 turret shell
Scaphopoda
 Dentaliida - Dentaliidae
Cephalopoda
 Nautilida - Nautilidae
Kummelonautilus sp. Matsumoto 1984 nautiloid
Chondrichthyes
 Myliobatiformes - Myliobatidae
? Myliobatis sp. Cuvier 1816 eagle ray
Echinoidea
 Camarodonta - Temnopleuridae
Anthozoa
 Scleractinia - Caryophylliidae
Trochocyathus stantoni Vaughan 1900 stony coral
Orthophragmina
  -
"Pseudophragmina (Proporocyclina) clarki" = Orthophragmina clarki2
"Pseudophragmina (Proporocyclina) clarki" = Orthophragmina clarki2 Cushman 1920
Palaeopinnixa
  -