Rivavipes Mustoe et al. 2012
JUNIOR SYNONYM(S): N/A
DESCRIPTION: Large plantigrade tridactyl bird tracks showing
robust oval heel pad and three elongate digits. Hallux
impression is not present. Phalanges in the shape of
elongate triangles, rather than parallel sided. Digit III is
elongate relative to digits II and IV, which are approximately
equal in length. Heel pad deeper proximally than
distally.
Digit I (hallux) impressions are seldom present. Phalanges
are broad, with most footprints showing merging of
impressions for the heel pad and digits II–IV. Ungual impressions
show the presence of a small triangular claw, but tracks
commonly have indistinct digit terminations, as either an acute
or a rounded apex. Tridactyl shape typically fairly symmetric.
Interdigital angles for digits II–IV are less than 90 degrees.
Track widths measured from apices of digits II and IV are
10–15 cm. Interdigital angles for digits II–III and III–1V are variable,
typically between from 32 to 45 degrees. Interdigital angles
for digits II–IV range from 60 to 85 degrees. Digits II and IV
are approximately equal in length, and approximately 0.8 the
length of digit III. For footprints that preserve distinct ungual
impressions, digits II–IV each terminate in a small equilaterally
triangular toenail.
BEHAVIOR(S): Repichnia
ENVIRONMENTAL SETTINGS: Continental; terrestrial; subtropical
POSSIBLE TRACEMAKERS: Diatryma (=
Gastornis)
GEOLOGIC RANGE: Lower Eocene
ADDITIONAL REFERENCES:
REMARKS: Ichnogenus has the same description as the ichnospecies
Rivavipes giganteus. Description, environmental setting, possible tracemaker and geologic range written by Dr. George Mustoe of Western Washington University.