Comparison of Russian Neospirifer cameratus and Texas Neospirifer alatus

The species used in this comparison are the most common Neospirifer              
species in latest Pennsylvanian strata of the two regions, respectively.
The Russian specimen is from basal Gzhelian strata of the Rusavkino
Formation at the type section of the Gzhelian stage in Russia and the
Texas specimen is from mid Gzhelian age deposits of the Wayland Shale
in Texas, on the Eastern Shelf of the Midland Basin. The fossil horizon
at Gzhel consists of interbeds of limestone and shale, whereas the
Wayland Shale is entirely a mudstone deposit.

Both specimens have fasciculation (bundling of ribs) and the blunt
terminations of the hingeline with a D-shaped valve outline that is
the combination of characters used to identify Neospirifer cameratus.
However, there are also differences in characters that indicate the
species are different. The Texas specimen of N. alatus has more and
narrower ribs and stronger bundling of ribs than the Gzhel specimen.
The Gzhel specimen of N. cameratus has a sharply defined sulcus
groove on the beak in contrast to the wider and less sharp sulcus on
the beak. Some of the difference is due to the larger size of the
Texas specimen (5 cm vs. 4 cm for the Gzhel specimen), but it is
certainly a different species. Neospirifer alatus has a long winged
hingeline (alate condition) as juvenile that is only weakly developed
in Russian N. cameratus.

Click on pictures to magnify

    
Neospirifer cameratus, Gzhel, beak view         Neospirifer alatus, Texas, beak view

    
Neospirifer cameratus, Gzhel, brachial view     Neospirifer alatus, Texas, brachial view

    
Neospirifer cameratus, Gzhel, pedicle view       Neospirifer alatus, Texas. pedicle view

     
Neospirifer cameratus, Gzhel, side view            Neospirifer alatus, Texas, side view

     
Neospirifer cameratus, Gzhel, front view            Neospirifer alatus, Texas, front view

Comparison of Russian Neospirifer cameratus and Texas Neospirifer alatus

Beak view:
The Gzhel specimen has a shorter hingeline than the Texas specimen
and the ends are more blunt. The Gzhel specimen has fewer and larger
ribs than the Texas specimen and they are grouped into less distinct
bundles.

Brachial valve:
The Gzhel specimen has angular ends on the hingeline that keep a
similar angle during growth, but the Texas specimen has wing-like
extensions on the ends of the hingeline as a juvenile, changing to a
blunt tip only as an adult. The Gzhel specimen has larger ribs on the
brachial valve than the Texas specimen and the larger ribs do not
group into bundles until a later growth stage, whereas the Texas
specimen develops bundled ribs early in growth. Both specimens
lack fasciculation (bundling of ribs) on the outer parts of the wings.

Pedicle valve:
The Gzhel specimen has a narrow and sharply defined sulcus groove
whereas the Texas specimen has a wider sulcus with smoothed margins.
Strong fasciculation occurs on the juvenile part of the Texas specimen,
but fasciculation nearly disappears on the adult part of the shell. Both
specimens show a change from more alate (wing-like) juvenile shell to
more rounded margins without wings on the adult shell.

Side view:
Both specimens show the same profile and same amount of inflation.
The Texas specimen has a more incurved beak, but that is probably a
result of being a little older and at a later growth stage than the Gzhel
specimen. Both specimens show distinct growth lines. The Gzhel
specimen is probably 6 years old at the time of death.

Front view:
Both specimens show the same outline and ribbing patterns in this
orientation. This view of these brachiopods does not provide enough
information to distinguish between the two species. The similarity of
inflation, shape and size of these specimens indicates the life habits
of these two species were the same or very similar.

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