38
Fawnsfoot, Truncilla donaciformis
Description: This is a small mussel,
seldom getting much over 50mm. The
shell is thick and has a somewhat
triangular outline. The anterior end is
rounded while the posterior end is
pointed. The posterior ridge is
rounded. When you put both valves
together, the posterior slopes form a
flattened area. The beaks of the two
valves curl around until they meet
each other. The beak sculpture is a
series of fine looped ridges. The nacre
is white. The exterior can vary from
greens, browns, tans or yellowish with
numerous green rays. The rays may
have darker zig-zag markings within
them.
Similar species: Juvenile Deertoe
are similar to the Fawnsfoot though
adults get much larger. The
Fawnsfoot tends to be more elongate
and its posterior ridge isn't as sharp.
The Fawnsfoot may have visible beak
sculpture consisting of several fine
looped ridges that the Deertoe does
not have.
Hosts: Freshwater drum, sauger
Conservation status: G5, N5, S3. Its
status in Nebraska is indeterminate.
They may be present in the Missouri
River.
Habitats used: Large rivers or the
lower reaches of medium-sized
streams in sand or gravel (Cummings
and Mayer 1992). Small and large
rivers (Oesch 1995). Large and
medium- sized rivers in sand or mud.
Can adapt to lake or embayment
environment. (Parmalee and Bogan
1998). Rivers and lakes in packed
sand and gravel. Rarely found in
smaller streams (Watters et.al. 2009).
Distribution: Widespread in
Mississippi River basin. From Texas
north into Minnesota, through the
Great Lakes states into Pennsylvania
then following the Appalachians
through Mississippi to the Gulf.
Collection notes: The Fawnsfoot has
only been found in the Missouri.
There is an archeological record from
Sarpy County.
Comments: This is a very small
mussel that prefers large rivers so
records may be scant for that reason.
Archeological data suggests it has
always been rare in this state. That it
is seldom found in smaller streams
may indicate that its host fish is a big
river fish.
