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.
Foraminifera
 Nummulitacea - Asterocyclinidae
"Pseudophragmina (Proporocyclina) clarki" = Pseudophragmina clarki2
"Pseudophragmina (Proporocyclina) clarki" = Pseudophragmina clarki2 Cushman 1920
Anthozoa
 Scleractinia - Caryophylliidae
Trochocyathus stantoni Vaughan 1900 stony coral
Cephalopoda
 Nautilida - Nautilidae
Kummelonautilus sp. Matsumoto 1984 nautiloid
Gastropoda
 Neotaenioglossa - Calyptraeidae
Calyptraea diegoana2 Conrad 1855 slipper shell
 Cerithioidea - Turritellidae
Turritella buwaldana2 Dickerson 1916 turret shell
Turritella uvasana2 Conrad 1855 turret shell
as Turritella uvasana applinae
Turritella andersoni2 Dickerson 1916 turret shell
as Turritella andersoni lawsoni
 Sorbeoconcha - Strombidae
Platyoptera pacifica Squires and Demetrion 1990 true conch
 Neogastropoda - Clavatulidae
"Fusiturricula (Crenaturricula) crenatospira" = Crenaturricula crenatospira2
"Fusiturricula (Crenaturricula) crenatospira" = Crenaturricula crenatospira2 Cooper 1894 snail
as Fusiturricula (Crenaturricula) crenatospira domenginica
 Neogastropoda - Clathurellidae
Domenginella claytonensis2 Gabb 1864 snail
Bivalvia
 Ostreida - Pteriidae
Pteria pellucida Gabb 1864 pearl oyster
 Ostreida - Pinnidae
"Pinna lewisi" = Pinna (Pinna) lewisi2
"Pinna lewisi" = Pinna (Pinna) lewisi2 Waring 1914 oyster
 Ostreida - Ostreidae
"Ostrea idriaensis" = Acutostrea idriaensis2
"Ostrea idriaensis" = Acutostrea idriaensis2 Gabb 1869 oyster
 Cardiida - Cardiidae
"Nemocardium linteum" = Nemocardium (Nemocardium) linteum2, "Acanthocardia (Schedocardia) brewerii" = Schedocardia brewerii2
"Nemocardium linteum" = Nemocardium (Nemocardium) linteum2 Conrad 1855 cockle
"Acanthocardia (Schedocardia) brewerii" = Schedocardia brewerii2 Gabb 1864 cockle
 Cardiida - Psammobiidae
"Gari texta" = Gari (Gobraeus) texta
"Gari texta" = Gari (Gobraeus) texta Gabb 1864 clam
 Cardiida - Gastrochaenidae
Gastrochaena ? dubitata Hanna 1927 clam
 Carditida - Carditidae
Venericardia (Pacificor) hornii2 Gabb 1864 clam
as Venericardia (Pacificor) hornii calafia
Scaphopoda
 Dentaliida - Dentaliidae
Rhynchonellata
 Terebratulida - Terebrataliidae
Terebratalia aff. batequia Sandy et al. 1995
Malacostraca
 Decapoda - Scyllaridae
"Parribacus caesius n. sp." = Llajassus caesius
"Parribacus caesius n. sp." = Llajassus caesius 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 - Euryplacidae
"Glyphithyreus weaveri" = Orbitoplax weaveri2
"Glyphithyreus weaveri" = Orbitoplax weaveri2 Rathbun 1926 crab
 Decapoda - Macropipidae
Portunites insculpta Rathbun 1926 crab
 Decapoda - Raninidae
Raninoides slaki n. sp. Squires 2001 crab
Echinoidea
 Camarodonta - Temnopleuridae
Chondrichthyes
 Myliobatiformes - Myliobatidae
? Myliobatis sp. Cuvier 1816 eagle ray