SPHENOPHRYNE - American Museum of Natural History

110 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253
Fig. 67. Dorsal (upper) and ventral views of skulls of Oxydactyla and Austrochaperina. A. O.
stenodactyla, AMNH A92802. B. O. coggeri, AMNH A140874. C. A. brevipes, AMNH A130527. Scale
bars measure 4 mm.
ranges from 0.293 to 0.500 (table 14). In 15
species the ratio is 0.400, two single-specimen
samples slightly exceed this figure at
0.412 and 0.425, and one sample (N 6)
averages 0.410 (range 0.382–0.448). Two
other samples of five and six specimens each
have similar variation but much lower
means.
Within the assemblage, Sphenophryne cornuta
stands out with more greatly expanded
diapophyses. Its mean (0.467) and range
(0.446–0.500, N 3) are markedly displaced
from those of other species. Only Austrochaperina
derongo (mean 0.410, range
0.382–0.448, N 6) approaches cornuta.
COCCYX: The coccyx articulates freely on
paired sacral condyles in all specimens. In
none of the specimens are there well-developed
diapophyses (figs. 72, 73). The two
largest single-species samples, Austrochaperina
derongo and Oxydactyla stenodactyla
(N 6) each include individuals with no
trace of diapophyses and others with one
short pair, which is the maximum extent seen
in any specimen. Therefore, I find nothing in
the morphology of the coccyx of systematic
utility.
PECTORAL GIRDLE: Evolutionary modifications
of the microhylid pectoral girdle involve
the reduction or deletion of ventral elements,
any of which of the complete firmisternal
primitive set of ventral elements
(exemplified by Rana) except the coracoids
may be involved. The girdles of the species
studied here, examined by dissection in species
for which cleared-and-stained specimens
were not available, are among the more
primitive in the family. They have in common
the most complete set of elements of
any Australopapuan microhylid (Genyophryninae
and Asterophryinae) in that they possess
bony coracoids and elongate clavicles,
cartilaginous procoracoids, and a cartilaginous
sternal plate (see Zweifel, 1985b: fig.
51, for two typical examples). A number of
genera of Madagascar and Asia are more