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lis hypotarsi along the shaft flat and virtually absent; shaft dorsoplantarly
compressed; depression on plantar face; fossa
metatarsi I distinct; and trochleae metatarsi II and IV with
equal distal extension. This suite of features separates the
Megapodiidae from other living and most extinct Galliformes.
The fossil and other Megapodiidae differ from the Quercymegapodiidae
by having the crista metatarsi medialis projecting
further plantarly, trochlea metatarsi II not globular, and
trochleae metatarsi II and IV with equal distal extension (characters
from Mourer-Chauvire, 1992). In species of the Gallinuloididae
the depression on the plantar surface is more extensive
than in the Megapodiidae.
The Megapodiidae also differ from the Columbidae by lacking
an indentation on the medial border of the shaft distal to the
fossa metatarsi I and by having the sulcus hypotarsi in the same
dorsoplantar line as the eminentia intercondylaris (in proximal
view) rather than offset laterally; also, the trochlea metatarsi II
is more in the same lateromedial line as trochleae metatarsi III
and IV (in distal view) instead of being recessed plantarly and
rotated medially.
The fossil exhibits a suite of characters unlike those found in
other genera of the Megapodiidae, for which reason it is recognized
as a new genus.
Ngawupodius, new genus
TYPE SPECIES.—Ngawupodius minya, new species, by original
designation and monotypy.
ETYMOLOGY.—Ngawu, in South Australia an Aboriginal
name for the Malleefowl Leipoa ocellata (see Peter and Peter,
1993), and -podius, Latinized Greek, "footed," in allusion to
the similarities between the tarsometarsi of these taxa.
DIAGNOSIS.—The proximal end is medially flared less than
in Megapodius or Progura but is more so than in Alectura. The
shape and size of the cotyla medialis are about the same as the
cotyla lateralis in proximal view; the dorsal rim is not produced
as far dorsally, and the medial rim is thin, unlike the conditions
in Leipoa or Alectura. The sulcus hypotarsi is proportionally
small in proximal view compared with all the modern taxa. The
robustness of the lateral side of the hypotarsus in proximal
view is blocky, unlike that in Megapodius. The plantar extension
of the crista medialis hypotarsi is greater than in Alectura,
Talegalla, Aepypodius, or Macrocephalon but is less than in
Megapodius, Eulipoa, or Leipoa. The relative plantar extension
of the crista lateralis hypotarsi differs from that in Alectura,
Talegalla, Aepypodius, or Progura in being about one-half that
of the crista medialis. The distally projecting process on the
distal end of the hypotarsus is smaller than that in Megapodius.
The dorsoventral compression of the shaft is greater than in Talegalla
or Aepypodius. The sides of the shaft are relatively parallel
and do not widen toward the distal end, unlike Alectura,
Leipoa, Aepypodius, Talegalla, Macrocephalon, or Progura.
The relative development of the tuberositas M. tibialis cranialis
is shorter in the fossil than in the modern forms. The fossa
metatarsi I is not as distinct as in Megapodius, Leipoa, or
Progura and has little medial extension. The trochleae are
gracile and are not swollen as in the other genera, particularly
Megapodius. The trochlea metatarsi II is at the same level as
the trochlea metatarsi IV, rather than slightly above, when
viewed either distally (unlike Megapodius, Leipoa, or Talegalla)
or dorsally (unlike Megapodius, Leipoa, Aepypodius, or
Progura). The trochlea metatarsi II is neither inflated nor globular
as it is in Megapodius or Eulipoa, and it does not diverge
strongly medially, unlike Alectura, Leipoa, Aepypodius, Talegalla,
Macrocephalon, or Progura. The trochlea metatarsi IV
does not project laterally, unlike Megapodius or Eulipoa. The
articular groove of the trochlea metatarsi IV is moderately well
developed, more so than in Alectura, Leipoa, Aepypodius, Talegalla,
or Progura, but is less distinct than in Megapodius.
Ngawupodius minya, new species
FIGURE 1A-C
HOLOTYPE.—Complete right tarsometatarsus, Paleontology
Collection of the Museum of Victoria (MV), Melbourne,
P160493. Collected by I. Parker on 12 May 1979.
TYPE LOCALITY.—South end of Lake Pinpa, South Australia
(31°08'31"S, 140°12'47"E; T.H. Rich, pers. comm., 1996).
HORIZON.—Namba Formation, Ericmas Fauna, late Oligocene.
ETYMOLOGY.—Minya, in South Australia an Aboriginal
word for "small" (Reed, 1977); for the purposes of nomenclature,
minya should be considered to be without gender.
DIAGNOSIS.—As for the genus.
DESCRIPTION.—The fossil is from an adult bird because the
surface lacks porosity, the tarsal cap is completely fused to the
proximal end of the metatarsals, the hypotarsus is fully formed,
and the metatarsals are fully fused over their entire length. In
immature Leipoa ocellata, the tarsometatarsi may approach the
size in that of adult birds yet still be highly porous and incompletely
fused.
Total length 40.2 mm; proximal width 8.1 mm; distal width
9.5 mm; distal depth 5.7 mm. Eminentia intercondylaris low,
about same height as rim of cotyla medialis; both higher than
rim of cotyla lateralis. Depth of crista hypotarsi medialis about
one-half that of proximal end of bone (proximal depth to hypotarsus
4.4 mm; proximal depth with hypotarsus 8.0 mm), with
laterally directed projection at end. In proximal view, sulcus
medialis hypotarsi slightly laterad of eminentia intercondylaris,
three shallow sulci lateralis hypotarsi and two low cristae lateralis
hypotarsi on rather square hypotarsus. In lateral view, hypotarsus
short (5.1 mm). Ridge extending distally from hypotarsus
on facies plantaris very low. Shaft broad (midshaft width, 4.3
mm; shaft width at proximal edge of fossa metatarsi I, 4.5 mm)
but dorsoplantarly flattened (midshaft depth, 2.6 mm; shaft
depth at proximal edge of fossa metatarsi I, 2.8 mm), markedly
so on medial side; lateral margin straight, medial margin somewhat
concave distally to fossa metatarsi I; distal to fossa produced
more medially. Fossa metatarsi I elongate (5.8 mm). Fos-