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Fossil emus



The honorable Darren Naish requested that I forward this to the list.



Emus have quite a good fossil record with definite members of the Dromaiinae being known as early as the Pliocene (note that in this discussion I follow most other recent authors in regarding Dromaiinae and Casuariinae as sister- taxa within the Casuariidae). Sibley & Ahlquist (1990) proposed on the basis of DNA-DNA hybridisation that dromaiines and casuariines diverged during the Late Oligocene (c. 25 mya). Patterson & Rich (1987) reviewed all fossil emus and this work should be your first stop if you're interested in the fossil history of the group.

_Emuarius_ from the Late Oligocene to Late Miocene of
Australia - originally placed within _Dromaius_ - has more
recently been argued to be a basal dromaiine outside
_Dromaius_ (see Boles 1992, 1997, 2001). _Emuarius_
combines features of cassowaries (e.g., femur, skull) with
those of emus (e.g., feet, tibiotarsus) and consequently its
generic name is a deliberate combination of 'emu' and
'_Casuarius_': on occasion Boles has even referred to
_Emuarius_ as a 'cassomu' or 'emuwary'. Two species are
presently known: _D. gidju_ from the Late Oligocene-early
Late Miocene of Riversleigh, Queensland; Early Miocene
Wipajiri Formation of South Australia; and Late Miocene of
Alcoota, Northern Territory, and _E. guljaruba_ from the
Late Oligocene Etadunna Formation of South Australia.

The oldest known casuariines (cassowaries) are from the
Pliocene of Papua (Plane, 1967). Other fossil cassowaries
are known from the Pleistocene of New South Wales and
Papua.

Charles De Vis named several fossil emu species, all from
the Pleistocene Darling Downs of Queensland, during the
1880s and 90s. _Dromaius patricius_ was based on an
assortment of bones, not all of which were avian: only a
partial tibiotarsus referred to this species is definitely from
an emu (De Vis, 1888, 1892, 1905) and it was shown by
Patterson & Rich (1987) to be indistinguishable from the
corresponding bone of _D. novaehollandiae_. De Vis
regarded _D. patricius_ as appreciably larger than _D.
novaehollandiae_ but in fact all the emu material of _D.
patricius_ overlaps in size with that of _D.
novaehollandiae_. A second species, _D. gracilipes_ (based
on a distal left tibiotarsus (De Vis, 1892)), is also
indistinguishable from the corresponding element of _D.
novaehollandiae_. _Metapteryx bifrons_, regarded by De
Vis (1892) as a giant kiwi and based on a partial left
tarsometatasus, is also a fossil emu and was shown by
Patterson & Rich (1987) to, again, be indistinguishable
from _D. novaehollandiae_.

What appears to be the only valid species of entirely fossil
emu, _D. ocypus_, is from the Pliocene Mampuwordu
Sands of Lake Palankarinna, South Australia (Miller, 1963).
Only known from a damaged tarsometatarsus (though a
partial femur and partial tibiotarsus were later referred to
this species), _D. ocypus_ is smaller than both Pleistocene
and modern _D. novaehollandiae_ and it differs from _D.
novaehollandiae_ in having a more strongly convex
proximal intercotylar region.

Finally, the extant species _D. novaehollandiae_ is known
from abundant Pleistocene records and there are even
questionable Late Pliocene sites yielding this species (e.g.,
Cooper Creek, SA; Lake Kanunka, SA). Pleistocene sites
that have yielded fossil _D. novaehollandiae_ include
Darling Downs (Queensland) as discussed above, Bingara
(NSW), Lake Callabonna (SA), Lake Menindee (NSW),
Naracoote (SA), Thorlindah (Queensland), and Wombeyan
Quarry (NSW). For the full details on all of these records
see Patterson & Rich (1987). These fossils show that _D.
novaehollandiae_ had appeared by the start of the
Pleistocene at least (1.6 mya) and possibly by the Late
Pliocene (somewhere around 2-3 mya).

Several Pleistocene adult _D. novaehollandiae_ specimens
were smaller than living emus. This suggests that this
species underwent some periods of dwarfism in its history,
perhaps due to climatic or other palaeoenvironmental
factors.

Fossils of both historically extinct emus, the King Island
(_D. ater_) and Kangaroo Island emus (_D. baudinianus_),
are known but are poorly dated: they are probably Holocene
but may be Late Pleistocene. How old these two species are
is unknown but it is likely that both were recently evolved
island endemics: Patterson & Rich (1987) write 'We favour
the idea that speciation on King and Kangaroo Island could
have taken place in very little time geologically speaking.
Strong selection for dwarfism quite likely occurred after
these emus became isolated at the beginning of the last
interglacial (i.e., the Holocene)' (p. 99). Incidentally both
_D. ater_ and _D. baudinianus_ can be distinguished from
_D. novaehollandiae_ on the basis of skull characters.

The taxonomic status of the (also extinct) Tasmanian emu
(_D. diemenensis­_) is uncertain and whether this form was
part of _D. novaehollandiae_ or a distinct taxon remains
debated. Tasmanian emu fossils are known from the
Pleistocene (Scott, 1932). While the body size of the
historical Tasmanian emu population is controversial (there
is uncertainty as to whether it was a dwarf relative to _D.
novaehollandiae_), the Pleistocene Tasmanian fossils are
the same size as extant _D. novaehollandiae_.

Refs --

Boles, W. E. 1992. Revision of _Dromaius gidju_ Patterson
and Rich 1987 from Riversleigh, northwestern Queensland,
Australia, with a reassessment of its generic position.
_Science Series Natural History Museum of Los Angeles
County_ 36, 195-208.

Boles, W. E. 1997. Hindlimb proportions and locomotion of
_Emuarius gidju_ (Patterson & Rich, 1987) (Aves:
Casuariidae). _Memoirs of the Queensland Museum_ 41,
235-240.

Boles, W. E. 2001. A new emu (Dromaiinae) from the Late
Oligocene Etadunna Formation. _Emu_ 101, 317-321.

De Vis, C. W. 1888. A glimpse of the post-Tertiary
avifauna of Queensland. _Proceedings of the Linnean
Society of New South Wales_ 3, 1277-1292.

De Vis, C. W. 1892. Residue of the extinct birds of
Queensland as yet detected. _Proceedings of the Linnean
Society of New South Wales_ 6, 437-456.

De Vis, C. W. 1905. A contribution of the extinct avifauna
of Australia. _Annals of Queensland Museum_ 6, 3-25.

Miller, A. H. 1963. Fossil ratite birds of the late Tertiary of
South Australia. _Records of the South Australia Museum_
13, 413-420.

Patterson, C. & Rich, P. V. 1987. The fossil history of the
emus, _Dromaius_ (Aves: Dromaiinae). _Records of the
South Australia Museum_ 21, 85-117.

Plane, M. D. 1967. Stratigraphy and vertebrate fauna of the
Otibanda Formation, New Guinea. _Bureau of Mineral
Resources, Geology and Geophysics (Australia) Bulletin_
184, 1-64.

Scott, H. H. 1932. The extinct Tasmanian emu.
_Proceedings of the Royal Society of Tasmania_ 1932, 103-
107.

Sibley, C. G. & Ahlquist, J. E. 1990. _Phylogeny and
Classification of the Birds: A Study in Molecular
Evolution_. Yale Univ. Press (New Haven & London).

--
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

http://web.port.ac.uk/departments/sees/staff/NaishD.htm
email: darren.naish@port.ac.uk
tel: 023 92846045

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