Computer Media (SDSNH 3278) (Eocene of the United States)

Also known as Poway, in part

Where: San Diego County, California (32.8° N, 117.1° W: paleocoordinates 33.5° N, 103.1° W)

• coordinate based on nearby landmark

• small collection-level geographic resolution

When: Scripps Formation (La Jolla Group), Lutetian (47.8 - 41.3 Ma)

• From the lowermost part of the section. A single bed, 50-70 cm thick, approximately 11m below the Friars-Stadium contact. Magnetochron C21n (early Lutetian) at the Computer Media section, according to Walsh et al. (2005). The land-mammal assemblage from locality 3278 contains the insectivore Crypholestes?, a genus apparently endemic to

•southern California and only confidently identifed from strata of early Uintan "Age" (middle Eocene) (Novacek, 1976). The fossil assemblage from locality SDSNH 3278 contains molluscan taxa indicative of the middle Eocene "Transition Stage" of West Coast provincial molluscan biostratigraphy (Clark and Vokes, 1936; as refined by Givens and Kennedy, 1979). In terms of correlation with the standard European section, Givens (1974), Givens and Kennedy (1979), Saul (1983), and Squires (1984, 1987) considered the middle Eocene "Transition Stage" to be correlative with the middle part of the Lutetian Stage.

• bed-level stratigraphic resolution

Environment/lithology: shoreface; fine-grained, medium, shelly/skeletal, gray, conglomeratic sandstone

• The co-occurrence of both complete, delicate shells (e.g., the gastropods Diodora and Zachrysia) and abraded shells (e.g., the bivalves Barbatia and Corbicula) and the co occurrence of ecologically mixed (e.g. marine species and terrestrial species; sandy bottom species and rocky rubble species), as well as the lack of articulated bivalves, suggests post-mortem transportation of shell material to a common site of deposition (i.e., a storm-bed accumulation). Sand-rich/pebbly nature, mixture of terrestrial and marine components, and presence of plant-rich mudstone (probable lagoon) a few meters higher, suggest shoreface environment.
• Fine to medium sandstone, gray, fossiliferous, with basal cobble conglomerate. At the base of the fossiliferous bed is pebble conglomerate with fossils tightly packed in among the clasts as whole and fragmented shell material. The pebble conglomerate grades upward into a pebbly sandstone where shells are unoriented and "floating" in the matrix. The lower contact of the bed is undulatory and erosional, and the upper contact is gradational.

Size class: macrofossils

Preservation: original aragonite, original calcite

Collected by B.O. Riney in 1985

Primary reference: S. L. Walsh. 1991. Eocene mammal faunas of San Diego County. Pacific Section SEPM 68:161-178 [J. Alroy/J. Alroy/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 16712: authorized by John Alroy, entered by John Alroy on 12.04.1997, edited by Mark Uhen and Patricia Holroyd

Creative Commons license: CC BY (attribution)

Taxonomic list

• originally assigned to Friars Fm.; see Walsh 1996b
at the base of the Computer Media section of Walsh et al. 1996
unclassified
  -
Foraminifera
 Rotalioidea - Elphidiidae
Labyrinthus
  -
Labyrinthus ? sp.2 Kobluk 1979
Anthozoa
 Scleractinia - Turbinoliidae
Turbinolia pusillanima3 Nomland 1916 stony coral
Gymnolaemata
 Cheilostomata - Onchoporidae
Bivalvia
 Nuculanida - Nuculanidae
"Nuculana (Saccella) aff. gabbi" = Nuculana gabbii3
"Nuculana (Saccella) aff. gabbi" = Nuculana gabbii3 Conrad 1866 pointed nut clam
 Nuculida - Nuculidae
Acila (Truncacila) decisa3 Conrad 1855 divaricate nutclam
 Mytilida - Mytilidae
 Ostreida - Ostreidae
Acutostrea idriaensis3 Gabb 1869 oyster
 Arcida - Glycymerididae
 Arcida - Arcidae
Barbatia sp.3 Gray 1842 clam
 Carditida - Carditidae
 Solenida - Solenidae
Solena (Eosolen) novacularis3 Anderson and Hanna 1925 clam
 Cardiida - Tellinidae
Tellina aff. townsendsis3 tellin clam
n. sp.
Tellina soledadensis3 Hanna 1927 tellin clam
"Tellina lebecki" = Tellina (Phyllodina) lebecki3 Anderson and Hanna 1925 tellin clam
"Tellina castacana" = Tellina (Angulus) castacana3 Anderson and Hanna 1925 tellin clam
 Cardiida - Donacidae
? Donax sp.3 Linnaeus 1758 clam
 Cardiida - Mactridae
""Spisula" bisculpturata" = Mactromeris bisculpturata3
""Spisula" bisculpturata" = Mactromeris bisculpturata3 Anderson and Hanna 1925 clam
 Cardiida - Veneridae
 Cardiida - Corbiculidae
 Pholadida - Corbulidae
Corbula (Carycorbula) dickersoni3 Weaver and Palmer 1922 clam
Scaphopoda
 Dentaliida - Dentaliidae
Dentalium sp.3 Linnaeus 1758 tusk shell
Gastropoda
 Opisthobranchia - Cylichnidae
 Stylommatophora - Camaenidae
Zachrysia fraterna n. sp.2 Roth 1988 land snail
 Neotaenioglossa - Calyptraeidae
Calyptraea diegoana3 Conrad 1855 slipper shell
 Architaenioglossa - Ampullinidae
Eocernina hannibali3 Dickerson 1914 snail
Pachycrommium clarki3 Stewart 1927 snail
 Sorbeoconcha - Vitrinellidae
Vitrinella cf. leeta3 Hanna 1927 snail
 Sorbeoconcha - Ficidae
Ficopsis remondii3 Gabb 1864 fig shell
subspecies crescentensis
 Neogastropoda - Olividae
Olivella mathewsonii3 Gabb 1864 olive snail
 Sorbeoconcha - Naticidae
Sinum obliquum3 Gabb 1864 moon snail
Neverita (Neverita) globosa3 Gabb 1869 moon snail
 Cerithioidea - Turritellidae
Turritella buwaldana3 Dickerson 1916 turret shell
 Cerithioidea - Melanopsidae
Loxotrema turritum3 Gabb 1869 snail
 Cerithioidea - Pleuroceridae
 Cerithioidea - Thiaridae
? Thiara sp.3 Röding 1798 snail
 Lepetellida - Fissurellidae
 Neritoidea - Neritidae
Cephalopoda
 Nautilida - Aturiidae
Aturia sp.3 Bronn 1838 nautiloid
Reptilia
 Loricata -
Pristichampsus sp.3 Gervais 1853 crocodilian
 Crocodylia - Gavialidae
cf. Tomistoma sp.3 Müller 1846 false gharial
Mammalia
 Theriamorpha - Sespedectidae
? Crypholestes sp. Novacek 1980 placental
 Theriamorpha - Herpetotheriidae
Peratherium sp.3 Aymard 1850 marsupial
 Didelphimorphia - Didelphidae
Actinopteri
 Siluriformes - Ariidae
Ariidae indet.3 Berg 1958 Ariid catfish
otolith
Chondrichthyes
 Carcharhiniformes - Triakidae
cf. Galeorhinus sp.3 de Blainville and Prévost 1816 school shark