SPHENOPHRYNE - American Museum of Natural History

2000 ZWEIFEL: PARTITION OF SPHENOPHRYNE
53
unwebbed, relative lengths 4 3 5 2
1, all with discs larger than those of fingers,
that of fourth toe about twice width of
penultimate phalanx; subarticular elevations
low, rounded, scarcely evident; inner metatarsal
elevation small, elongate, rounded.
Skin smooth above and below except for
very weak, diagonal postorbital fold.
Purplish brown above in preservative with
a few darker flecks, weak, convergent dark
lines in the scapular region, and an ill-defined
dark stripe above the postocular fold.
The fingers and toes are marked with dark
and light in no particular pattern. The ventral
ground color is pale tan with gray-brown
mottling from chin to posterior tip of abdomen
as well as beneath the limbs. The intensity
of the mottling is slightly less on the
abdomen than elsewhere.
VARIATION IN TYPE SERIES: Populations referred
to A. rivularis have different maximum
body sizes. The sample from Western
Province includes apparently immature
males (no vocal slits) of 30.2 and 31.5 mm,
mature males of 35.7 and 36.5 mm, females
just maturing at 35.9 and 36.9 mm, and adult
females of 39.1 to 49 mm. Several males
from Mt. Hunstein, East Sepik Province, in
the range of 39–45 mm lack vocal slits
whereas others 42–45 mm have them.
Whether this indicates variability in the vocal
apparatus of adult males or variability in size
at maturity is not evident, but the greater size
of males in this sample is clear. The series
of females from Mt. Hunstein includes a juvenile
as large as 44.0 mm, one maturing at
44.8 mm and adults 47.6–51.5 mm. Proportions
of specimens in the two major samples
are quite similar (table 2). Regression data
are in table 3.
In life, frogs from Western Province were
scarcely more distinctively colored than in
preservative, being olive-brown above with
darker brown markings, a faint lumbar ocellus,
and the tympanic area pale yellowish tan.
Undersides were gray-brown with faint darker
mottling most evident on the chin. The iris
is dark golden brown above and below the
horizontal pupil, little differentiated from the
dorsal color.
REFERRED SPECIMENS: SAMA 6385–6403,
6409–6414, 6416–6418, collected by Barry
Craig at Busilmin, West Sepik Province, on
May 7, 1965. I lack a complete suite of measurements
on these specimens and thus could
not make critical comparisons. Although I
exclude them from paratype designation, it is
likely that they represent this species.
ILLUSTRATIONS: 3rd finger terminal phalanx,
fig. 71O; premaxilla, fig. 63F; sacral
region, fig. 73A; vomer, fig. 65N; skull, fig.
68A; hand and foot, fig. 56A.
CALL: Through the courtesy of Stephen
Richards, I have tape recordings of the calls
of two individuals of this species and have
examined one of the voucher specimens. The
call (fig. 79B, table 5) is a series of harsh
notes each about 0.06–0.08 sec long, composed
of six to eight pulses, and repeated at
a rate of about three notes per second. Individual
notes characteristically begin with a
long pulse, followed by others half its length
(fig. 80C), although occasional notes have all
the pulses approximately the same length
(see Vocalizations). The dominant frequency
is approximately 2600 Hz in one instance
and 2700 in the other. One complete call (i.e.,
initiated after recording began and terminated
voluntarily) lasted 1 min 25 sec; the other
(presumably incomplete) call was at least 38
sec long. Both frogs called from beside small
creeks. The air temperature recorded for one
call was 21.3C.
Stephen Richards recorded one of the
frogs at 1600 m on Mt. Stolle, West Sepik
(Sanduan) Prov., the other about 5 km west
of Tabubil (elevation about 600 m by my estimate
and close to the type locality), Western
Prov. The localities are about 75 km
apart.
COMPARISONS WITH OTHER SPECIES: Austrochaperina
rivularis is compared with two
similar species—macrorhyncha and palmipes—in
the accounts of those species. The
two species basipalmata and derongo are
smaller, with maximum male and female sizes
approximating the sizes at which rivularis
matures. Presence of toe webbing distinguishes
basipalmata, and average tibia
length, eye, hand, and disc sizes are smaller
in derongo.
HABITAT AND HABITS: The frogs found at
Finalbin, when uncovered from beneath
leaves lying beside small streams in mossy,
hilly forest, jumped into the water and swam
well in attempting escape. Except for the