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NUMBER 89 203
The fossil is larger than the known tarsometatarsal specimens
of Quercymegapodius {Q. depereti: total length 30.0 mm,
distal width 5.8 mm, distal depth 3.75 mm; Mourer-Chauvire,
1992).
Discussion
GEOGRAPHIC SETTING AND GEOLOGY
Northeastern South Australia has produced a number of important
fossil sites, ranging in age from Oligocene-Miocene to
Pleistocene, many of which have yielded avian remains. The
fossil megapode was recovered from Lake Pinpa, one of several
localities in the Tarkarooloo Basin where outcrops of the
Namba Formation are exposed. The formation is divisible into
two members, the upper resting disconformably on the lower.
Green claystones and dolomitic claystones at the top of the
lower member have yielded vertebrate remains designated as
the Pinpa Fauna. A sequence of thin-bedded, fine- to mediumgrained
sands cut into the lower member, and it is these basal
sands of the upper member that have produced the Ericmas
Fauna (type locality Ericmas Quarry, Lake Namba;
3ri2'S,140°14'E), from which the megapode bone was recovered.
For details of the geology, dating, and other vertebrate remains,
see Callen and Tedford (1976), Tedford et al. (1977),
Woodburne et al. (1985), and references therein.
The age of the Ericmas Fauna was originally placed at middle
Miocene on the basis of its position above the Pinpa Fauna,
and, where there are comparable species, species in the Ericmas
Fauna appear less primitive. The lower member of the
Namba Formation contains pollen floras similar to Balcombian-Batesfordian
(middle Miocene) deposits in Victoria and
South Australia. Tedford et al. (1977) put a maximum age of
ca.14-16 Ma on vertebrates higher in the formation. Woodburne
et al. (1985) considered the Ericmas Fauna to be middle
Miocene in age. Subsequent work, however, has led to a revision
of these dates. Studies on the central Australian Etadunna
Species
Ngawupodius minya
Megapodius reinwardt
Megapodius eremita
Megapodius freycinet
Megapodius pritchardi
Megapodius cumingii
Megapodius nicobarensis
Eulipoa wallacii
Macrocephalon maleo
Alectura lathami
Talegalla jobiensis
Talegalla fuscirostris
Aepypodius bruijni
Aepypodius arfakianus
Leipoa ocellata
Progura gallinacea
Formation (East Lake Eyre Basin), considered to be roughly
contemporaneous with the Namba Formation, led Woodburne
et al. (1993) to place its age at late Oligocene. These authors
considered the Ditjimanka Fauna (Lake Palankarinna) from the
Etadunna Formation and the Ericmas Fauna to be "approximate
correlatives" (ca. 24-26 Ma).
The Lake Pinpa site, like most others in central Australia, is
characterized by lacustrine/fluviatile deposits. The bones have
been disarticulated post-mortem and have been transported
varying distances. The faunal summary by Rich et al. (1991)
showed that there was a large aquatic component, represented
by several species of lungfish {Neoceratodus), teleost fish, chelid
turtles, crocodiles, the primitive platypus Obdurodon insignis
Woodburne and Tedford (1975), and a dolphin (Rhabdosteidae).
Terrestrial forms included marsupials of the
families Dasyuridae, Phascolarctidae, Diprotodontidae, Pseudocheiridae,
and Petauridae. The only other bird thus far reported
was assigned to the Anseriformes (Rich et al., 1991) and
has not yet been studied. In contrast, the Pinpa Fauna has abundant
bird remains, including grebes, pelicans, cormorants, waterfowl,
rails, burhinids, and flamingos.
RECONSTRUCTION OF Ngawupodius AND ITS ENVIRONMENT
Living megapodes were used as the basis of an attempt to reconstruct
the general size and proportions of Ngawupodius. Because
skeletons of certain taxa were not available, published
tarsal measurements from skins were substituted; these give
close approximations of the length of the tarsometatarsus.
Weights and body lengths are less precise measurements but
can serve as approximate indicators of size and permit some
rough values to be obtained; data were taken from Marchant
and Higgins (1993), Jones et al. (1995), and specimens.
The tarsometatarsus of Ngawupodius is smaller in absolute
terms than those of other described taxa (Table 1; Figure 1). It
TABLE 1.--Measurements ( mm ) of the tarsometatarsus in Ngawupodius minya and recent species of megapodes,
giving mean (x), range, and sarr pie size (n).
X
40.2
59.8
64.6
69.2
58.6
67.0
68.2
61.2
87.6
96.9
87.7
-
108.4
97.0
75.3
-
Total length
range
-
-
-
-
58.1-59.0
61.1-72.8
-
-
86.6-88.6
88.2-103.3
85.0-90.4
-
-
-
71.2-76.7
-
n
1
1
1
1
2
2
1
1
2
5
2
- 1
1
3
-
X
8.1
10.6
11.9
12.7
9.2
11.6
12.9
10.2
16.0
17.6
14.8
-
16.2
14.8
15.9
25.5
Proximal width
range
-
- --
9.0-9.4
10.3-12.9
- -
15.9-16.0
16.5-18.6
14.7-14.8
-
-
-
15.3-16.3
-
n
1
1
1
1
2
2
1
1
2
5
2
- 1
1
3
1
X
9.5
12.2
13.7
14.0
10.8
13.5
14.3
12.3
16.7
18.1
16.3
16.0
17.9
16.0
17.5
28.4
Distal width
range
-
-
-
-
10.8
12.2-14.8
-
-
16.1-17.2
16.5-18.7
15.4-17.1
-
- -
16.1-18.3
-
n
1
1
1
1
2
2
1
1
2
6
2
1
1
1
3
1
X
4.3
4.5
5.2
5.4
3.9
5.4
5.9
4.5
6.2
7.3
6.3
5.3
6.8
6.2
6.8
-
Midshaft width
range
-
-
-
-
3.8-3.9
4.6-6.1
-
-
6.0-6.3
7.1-7.7
5.8-6.7
-
-
-
6.5-7.1
-
n
1
1
1
1
2
2
1
1
2
3
2
1
1
1
2
-