A
well-preserved
left
theropod
metatarsal
I
from
the
Campanian
Mesaverde
Formation
of
Wyoming
is
described
and
identified
as
belonging
to
a
caenagnathid,
representing
first
occurrence
this
clade
formation.
The
specimen
unique
in
being
relatively
small,
but
featuring
suite
characters
(triangular
shaft,
less
constriction
between
shaft
distal
condyle,
spherical
condyle)
that
are
seen
larger
examples
Caenagnathidae
such
Anzu
wyliei
or
“Macrophalangia
canadensis”.
This
suggests
previously-observed
differences
small
large
caenagnathids
not
solely
result
allometry,
may
represent
phylogenetically
informative
variation.
Although
limited,
new
lends
some
support
hypothesis
canadensis”
does
Chirostenotes
pergracilis.
Furthermore,
important
establishing
presence
within
fauna,
which
remains
poorly
known.
Journal of Vertebrate Paleontology,
Journal Year:
2023,
Volume and Issue:
43(5)
Published: Sept. 3, 2023
The
Upper
Cretaceous
Horseshoe
Canyon
Formation
of
Alberta,
Canada,
is
among
the
best-studied
paleoecosystems
in
North
America.
However,
its
microvertebrate
paleocommunity
structure
relatively
poorly
known,
partly
because
it
lacks
abundant
microsites
other
deposits
Alberta.
An
unusual
microsite
(FTS-2)
from
Horsethief
Member
described
that
produces
anuran
and
troodontid
material,
alongside
perinatal
material
ornithischians
tyrannosaurs.
Anuran
specimens
representing
a
minimum
two
separate
taxa
metatherian
molar
suggest
these
components
fauna
were
more
diverse
than
currently
recognized.
assemblage
similar
to
three
American
sites
produce
teeth
dinosaurs.
environmental
taphonomic
conditions
vary,
supporting
notion
mixed
biotic
abiotic
factors
driving
association
troodontids
perinates.
In
part,
this
may
stem
nesting
preferences
between
dinosaurs,
as
collected
all
suggests
proximity
sites.
Sites
such
FTS-2
are
important
for
revealing
rare
small
paleoecosystems,
hold
promise
interactions
parts
fauna.
A
well-preserved
left
theropod
metatarsal
I
from
the
Campanian
Mesaverde
Formation
of
Wyoming
is
described
and
identified
as
belonging
to
a
caenagnathid,
representing
first
occurrence
this
clade
formation.
The
specimen
unique
in
being
relatively
small,
but
featuring
suite
characters
(triangular
shaft,
less
constriction
between
shaft
distal
condyle,
spherical
condyle)
that
are
seen
larger
examples
Caenagnathidae
such
Anzu
wyliei
or
“Macrophalangia
canadensis”.
This
suggests
previously-observed
differences
small
large
caenagnathids
not
solely
result
allometry,
may
represent
phylogenetically
informative
variation.
Although
limited,
new
lends
some
support
hypothesis
canadensis”
does
Chirostenotes
pergracilis.
Furthermore,
important
establishing
presence
within
fauna,
which
remains
poorly
known.