Turonian Scaphites

Turonian Scaphitoid Cephalopods
from the Mancos Shale in East-Central Utah
(All Macroconchs)

Shown from youngest (on top) to oldest
Rib counts are from the body chamber only
best viewed full screen
all about natural size

Scaphites whitfieldi Cobban 1951
    Numerous evenly spaced ribs on body chamber, phragmocone slightly compressed.
    Ribs average 52 secondaries, 8 primaries.
    Found high in the Juana Lopez Member (or lower Main Body) S.E. of Green River
    associated with Prionocyclus novamexicanus.

Scaphites cf. S. whitfieldi
A few less ribs on body chamber, phragmocone not compressed.
Associated with Prionocyclus wyomingensis East of Clawson.

Scaphites ferronensis Cobban 1951
    Fewer primary ribs on body chamber, ribs more closely spaced on curved part.
    Ribs average 46 secondaries, 5 primaries.
    Associated with Prionocyclus wyomingensis East of Ferron and Castle Dale

Scaphites cf. S. ferronensis
    A few more primary ribs than typical S. ferronensis, and the ribs on the curved
    part are a little stronger.
    Found along the Juana Lopez Member outcrop from East of Ferron to the Colorado border
    associated with Prionocyclus wyomingensis.

Scaphites warreni Meek and Hayden 1860
    Strong ribs on straight part of body chamber, more closely spaced and finer on curved part.
    Ribs average 34 secondaries, 8 primaries.
    Found below the beds containing S. cf. S. ferronensis in the Juana Lopez Member S.E. of Green River

Scaphites cf. S. carlilensis
Ribs just slightly closer spaced on curved part of body chamber
Associated with Prionocyclus macombi in the Juana Lopez Member S.E. of Green River

Scaphites carlilensis Morrow 1935
    Strong evenly spaced ribs on body chamber.
    Ribs average 28 secondaries, 10 primaries
    Associated with Prionocyclus hyatti in the lower Ferron Sandstone near Mounds

Jacobs, David K., Landman, Neil H., Chamberlain, Jr., John A., 1994 , Ammonite shell shape covaries with facies and hydrodynamics: Iterative evolution as a response to changes in basinal environment Geology 22: 905-908, report that two dimorphs of S. whitfieldi occur in different facies, a compressed dimorph in nearshore, sandy facies, and a depressed dimorph in muddy, offshore or basinal facies. I have found just the opposite to occur in the Mancos Shale, the depressed form (S. cf. S. whitfieldi) in nearshore, sandy facies, and the compressed form (S. whitfieldi) in offshore, muddy facies. This makes me wonder if S. whitfieldi found in eastern Utah are two dimorphs the same age, or two species of different age?