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A new emu (Dromaiinae) from the Late Oligocene Etadunna Formation


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A new emu (Emuarius guljaruba, sp. nov.) is described from the Late Oligocene Etadunna Formation (Ngama Local Fauna), based on a complete tarsometatarsus. While exhibiting evidence of cursorial abilities advanced over those of cassowaries (Casuarius), this taxon was not as cursorially adapted as the living Emu (Dromaius novaehollandiae). This taxon is provisionally referred to the genus Emuarius, although a definite generic assignment cannot be made.
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© Royal Australasian Ornithologists Union 2001 10.1071/MU00052 0158-4197/01/040317
Emu, 2001, 101, 317–321
A new emu (Dromaiinae) from the Late Oligocene Etadunna Formation
Walter E. Boles
Division of Vertebrate Zoology, Australian Museum, 6 College Street, Sydney, NSW 2000;
and School of Biological Sciences, University of New South Wales, NSW 2052, Australia.
Abstract. A new emu (Emuarius guljaruba, sp. nov.) is described from the Late Oligocene Etadunna Formation
(Ngama Local Fauna), based on a complete tarsometatarsus. While exhibiting evidence of cursorial abilities
advanced over those of cassowaries (Casuarius), this taxon was not as cursorially adapted as the living Emu
(Dromaius novaehollandiae). This taxon is provisionally referred to the genus Emuarius, although a definite generic
assignment cannot be made.
Emus (Dromaius) are one of the most characteristic elements
of the modern Australian avifauna. There is only a single
living species, D. novaehollandiae, although the Tasmanian
population (possibly specifically distinct) and two dwarf
species, D. baudinianus (Kangaroo Island) and D. ater (King
Island), have gone extinct within the past 200 years. There
have been several nominal fossil species erected, primarily
by C. W. De Vis towards the end of the 19th century (De Vis
1888, 1892). The fossil record of emus was reviewed by
Patterson and Rich (1987), who reduced D. patricius De Vis,
1888, D. gracilipes De Vis, 1892 and the putative kiwi
Metapteryx bifrons De Vis, 1892 to the synonymy of the
living D. novaehollandiae. The only previously described
palaeospecies they accepted was D. ocypus, described by
Miller (1963) from a tarsometatarsus from the Pliocene-aged
Mampuwordu Sands at Lake Palankarinna, South Australia
(Palankarinna Local Fauna).
In addition, Patterson and Rich (1987) described a new
species, D. gidju, from the Lake Ngapakaldi Leaf Locality,
South Australia (Wipajiri Formation; Kutjamarpu Local
Fauna), considered to be early Miocene. This was based on
an associated distal tibiotarsus, proximal tarsometatarsus
and shaft, and complete pes. Boles (1992) reported a femur
from the type locality of D. gidju. He considered that this
belonged to the same species, but noted that, while the lower
limb was very emu-like, the femur retained characteristics of
the cassowaries (Casuarius). The dichotomy between the
Casuariinae and Dromaiinae represents the acquisition in the
latter of a more cursorially modified lower hindlimb (tibio-
tarsus and tarsometatarsus), as evidenced by the relative
elongation of both bones and other associated characters.
Within the Dromaiinae, Boles (1992) recognised a second
dichotomy between taxa that had acquired modifications of
the upper hindlimb (femur) and those that had not, repre-
sented by the genera Dromaius and Emuarius, respectively.
Emuarius has the advanced lower limb but retained the prim-
itive character states of the upper limb; that is, it is a combi-
nation of the cassowary-like femur and the derived emu-like
tibiotarsus and tarsometatarsus.
Specimens referred to Emuarius gidju have subsequently
been found in the Late Oligocene–early Late Miocene of
Riversleigh, Queensland (Boles 1992, 1997). Two specimens
from the Late Miocene deposits at Alcoota, Northern
Territory, were first mentioned by Patterson and Rich (1987)
as Dromaius indeterminate, and cannot be distinguished
from Emuarius from other sites; they are now considered to
belong to E. gidju (Vickers-Rich and Rich 1993; personal
observation). This gives a known temporal range for this
species of Late Oligocene to Late Miocene.
Described herein is a new emu based on a complete tarso-
metatarsus, mentioned initially (‘an emu leg bone’) by
Pledge (1984) among taxa comprising the Ngama Local
Fauna recovered from Mammalon Hill.
Geology and Geography
Mammalon Hill is located near the north end of the western side of
Lake Palankarinna, South Australia (28°41S, 138°24E). Fossils at this
site have been recovered from the Etadunna Formation. On the basis of
the mammalian component of the fauna, five faunal divisions of this
Formation can be recognised (A–E, from the bottom to the top, respec-
tively). Faunal Zone D, from which the emu fossil was recovered, crops
out at Mammalon Hill. It lies between Zones C and E, with a range of
marsupials intermediate in their state of evolution between those in
these zones. Pledge (1984) recognised the Ngama Local Fauna for the
fossils from Zone D, as typified at Mammalon Hill. On the basis of
ektopodontid and pseudocherid possums (Marsupialia), the age of this
site is considered to be between the Etadunna Formation Faunal Zones
A–C and the Kutjamarpu Local Fauna (Rich et al. 1991). A depauperate
pollen flora immediately below the site was interpreted as mid-Miocene
(Truswell and Harris 1982); subsequently, magnetostratigraphic data
placed the age of the Etadunna Formation at 24–26 million years ago
(Woodburne et al. 1993). Avian families represented in the Ngama
Local Fauna include Anatidae, Accipitridae, Rallidae, Burhinidae,
Palaelodidae, Phoenicopteridae and Columbidae; most have yet to be
studied, but are consistent with the depositional environment being
318 W. E. Boles
primarily lacustrine, with limited fluviatile situations. For further infor-
mation on the geology, age and vertebrate taxa recovered from the
Ngama Local Fauna, see Stirton et al. (1961), Pledge (1984), Rich et al.
(1991), Woodburne et al. (1993) and references therein.
Measurements were made with digital calipers and rounded to the
nearest 0.1 mm. Osteological nomenclature follows Baumel and
Witmer (1993), including the use of ‘dorsal’ and ‘plantar’ to designate
the ‘front’ and ‘back’ of the tarsometatarsus, respectively.
Systematic palaeontology
The Mammalon Hill specimen (P23977) is held in the
palaeontological collection of the South Australian Museum
(SAM), as are the holotypes of E. gidju and D. ocypus. The
specimen described here consists of a left tarsometatarsus,
nearly complete other than minor loss of material somewhat
distal to the midpoint where the reconstructed proximal and
distal portions connect and on the plantar side of the cotyla
medialis. There is slight abrasion to the dorsal surfaces of tro-
chleae metatarsi II and III, and trochlea metatarsi II has been
reconstructed; otherwise there is little crushing or distortion.
The tarsometatarsus is known for all species of Dromaius
and for Emuarius gidju, thus permitting direct comparisons
with this specimen. Examination of the Mammalon Hill Emu
shows that it warrants recognition as a new species. Because
Emuarius and Dromaius are separated by character states of
the femur, in the absence of this element it is not possible to
definitively refer the new specimen to either genus. Rather
than make the assumption that the Mammalon Hill Emu pos-
sessed a derived femoral morphology, this taxon is provi-
sionally allocated to Emuarius, although in the following
discussion, comparisons are made with species of both
genera. (Although D. ocypus is, like E. guljaruba, known
only from the tarsometatarsus, its possession of an advanced
stage of reduction of trochlea metatarsi II allows it to be
placed in Dromaius.)
Emuarius guljaruba, sp. nov.
SAM P23977, a complete left tarsometatarsus with minor
damage (Fig. 1).
Type locality
Mammalon Hill, the north end of the west side of Lake
Palankarinna, South Australia (28°41S, 138°24E).
Formation, age and fauna
Etadunna Formation (Late Oligocene); Ngama Local Fauna
(= Etadunna Formation Faunal Zone D).
This species is separated from Dromaius and Emuarius gidju
by the following suite of characters: the distal end is propor-
Fig. 1. Tarsometatarsi of fossil and Recent dromaiines, dorsal view. (A) Emuarius gidju
(proximal end, holotype: SAM P26779, Leaf Locality, Kutjamarpu Local Fauna; distal end,
AM F78587, Gag Site, Riversleigh); (B) Emuarius guljaruba (holotype: SAM P23977,
Mammalon Hill, Ngama Local Fauna); (C) Dromaius ocypus (holotype: SAM P13444,
Lawson Quarry, Palankarinna Local Fauna); (D) Dromaius novaehollandiae (Recent). Bar
equals 50 mm. Distal tarsometatarsus in (A) added to photograph digitally.
A new emu from the late Oligocene 319
tionally narrow relative to the proximal end, the shaft is
slightly compressed anteroposteriorly but markedly com-
pressed mediolaterally on its distal half, and the trochlea
metatarsi II is not reduced relative to the other trochleae.
The reconstructed length of the tarsometatarsus is about
equal to that of the holotype of Dromaius ocypus and
approaches the predicted length for Emuarius gidju (Boles
1997) (Table 1). Morphologically, the proximal end is similar
to that of both Emuarius and other species of Dromaius, but
in size it is considerably larger than E. gidju, approaching
D. ocypus. The eminentia intercotylaris is low and broad.
The sulcus extensorius is moderately deep and rather broad,
although it is not as deep distally as in D. ocypus. While the
shaft does not have the pronounced degree of anteroposterior
compression that characterises E. gidju, it is somewhat more
compressed than in D. novaehollandiae, particularly on the
distal half of the medial side, where it is more rounded on the
plantar surface, rather than as a raised, flattened platform as
in D. novaehollandiae. Otherwise, E. guljaruba resembles
D. ocypus and D. novaehollandiae in the structure of its
plantar surface. The distal end of the shaft is mediolaterally
compressed, particularly relative to the proximal end. The
lateral borders of the shaft converge to about the midpoint,
then are roughly parallel distally, until the divergence of the
distal end. In contrast to the proximal end, the distal end is
much smaller than in either D. ocypus or D. novaehollandiae,
but is similar to that of E. gidju. This specimen, although
about the same length as the holotype of D. ocypus (SAM
P13444), has a relatively and absolutely much smaller troch-
lea metatarsi III, particularly in width, a shorter trochlea met-
atarsi IV, a longer trochlea metatarsi II and a less splayed
distal end (trochleae metatarsi II and IV are less divergent).
The sides of trochlea metatarsi III, as preserved, are roughly
parallel, not diverging distally as in the other species of Dro-
maius, although this may be influenced by wear. The incisu-
rae intertrochlearis are narrow.
guljaruba’; Bagandji language, lower Darling region of
New South Wales, meaning ‘emu’ (Hercus 1982), consid-
ered a noun in apposition.
The absence of a femur of guljaruba means that it is not pos-
sible to allocate this taxon to either Emuarius or Dromaius
with certainty, which admits two possible interpretations.
The first is that two species of Emuarius were contempora-
neous in the Late Oligocene (Fig. 2). Although not yet known
from the same deposits as Emuarius gidju, the Ngama Local
Fauna, of which guljaruba is part, overlaps in time with
several of the Riversleigh local faunas in which gidju occurs.
The other possibility is that guljaruba represents the oldest
known species of Dromaius, extending the fossil record of
this genus to the Late Oligocene. In neither case is it obvious
what ancestor–descendent relationships, if any, existed
between guljaruba and any species of the Dromaiinae.
Fossils considered to be emus by Patterson and Rich (1987)
are known from much of the intervening period between gul-
jaruba and D. ocypus, but much of this material was consid-
ered by these authors to be indeterminate below generic
level. As that study was conducted before the recognition of
Emuarius, the indeterminate femoral specimens merit
further examination.
Because Emuarius gidju had acquired the derived
morphology of the lower hindlimb, Boles (1992) considered
that it post-dated the cladistic event between emus and
Table 1. Tarsometatarsal measurements for Emuarius guljaruba compared with those of Emuarius gidju and species of Dromaius
All measurements are in millimetres. The estimated length for E. gidju is taken from Boles (1997), based on the holotype (SAM P26779) for the
roximal end and AM F78587 (Riversleigh: Gag Site: Dwornamor Local Fauna) for the distal end. Other measurements for E. gidju are summarised
from Boles (1992, 1997, and unpublished data). Measurements for D. novaehollandiae are summarised from Patterson and Rich (1987)
Emuarius gidju Emuarius guljaruba Dromaius ocypus Dromaius novaehollandiae
Length est. 340 c. 335 362 322–422
Proximal width 36.8–37.9 44.3 48.1 47.2–54.0
Depth, cotyla medialis 19.1–22.9 26.6 >25.3 25.4–27.6
Depth, cotyla lateralis >16.8–18.5 c. 26.3 19.9–23.7
Depth, dorsal side of area
intercotylaris across hypotarsus
27.2–c. 29.5 37.9 >35.6 36.0–41.3
Minimum shaft width 19.8 11.6–17.3
Distal width 44.1–c. 47.4 c. 46.9 53.3 47.4–54.6
Width, trochlea metatarsi II >9.5–10.5 12.6 11.8 9.0–11.1
Depth, trochlea metatarsi II >10.5–15.5 >15.1 18.1 13.0–17.6
Width, trochlea metatarsi III 17.6–21.7 20.6 27.8 21.9–28.9
Depth, trochlea metatarsi III 19.3–21.7 20.6 26.1 19.0–24.3
Width, trochlea metatarsi IV >12.2–14.5 >15.4 15.0 12.2–14.9
Depth, trochlea metatarsi IV 13.4–c. 15.5 >>13.4 18.0 14.3–17.2
320 W. E. Boles
cassowaries, and, although probably close to the mutual
ancestor of these groups, could not itself have been that
ancestor. The Late Oligocene occurrence of E. guljaruba
adds support to this conclusion. Boles (1992) noted that the
conclusion of Sibley and Ahlquist (1990), based DNA–DNA
hybridisation data, of a cassowary–emu division at 20–25
million years ago, was too recent to account for Emuarius.
The recently proposed divergence date of 35–38 million
years ago by Cooper et al. (2001) is more reasonable.
Boles (1992, 1997) remarked upon the proportions of the
hindlimb elements of Emuarius gidju relative to those of the
more primitive cassowaries and their implications about this
bird’s mode of locomotion. Some characters of the hindlimb
of E. gidju are more similar to either Casuarius or Dromaius,
while others are intermediate in structure between living
members of these genera. Notably, E. gidju exhibited three
morphological correlates with advanced cursoriality relative
to the condition in Casuarius: overall lengthening of the
lower hindlimb elements, lengthening of the tarsometatarsus
relative to the tibiotarsus, and a reduction in the relative size
of digit II. For these reasons, Boles (1992, 1997) considered
that this taxon appeared to mark in the Casuariidae a stage in
the transition from a generalised cursor to more specialised
cursorial locomotion. From this, he suggested that the
increased cursoriality may have been related to the occur-
rence of more open habitat in addition to the rainforest
usually considered to have been present.
Emuarius guljaruba has the same modifications of the tar-
sometatarsus that led Boles (1992, 1997) to infer developing
cursoriality in Emuarius relative to Casuarius. In comparison
to D. ocypus and D. novaehollandiae, the trochlea metatarsi II
of E. guljaruba does not exhibit marked reduction (similar to
E. gidju, but more so than in Casuarius), indicating that spe-
cialisation for open-country locomotion was still at a much
lower stage of development. Nonetheless, the longer, more
slender tarsometatarsus of E. guljaruba compared with Cas-
uarius is suggestive of an animal capable of more rapid loco-
motion, and thus the presence of more open habitat, although
this is not the only explanation for the lengthened lower limb
element (see Boles 1997). Obviously there is still much to be
learnt about the early stages of emu evolution.
I particularly thank Mr N. Pledge, Curator of Fossils, South
Australian Museum, for allowing me to work on this
specimen and for discussion and information on the age and
geology of the Mammalon Hill locality, Mr T. Peters, South
Australian Museum, for taking the photograph, and
Mr J. Peters, Birds Australia, for information on the
Aboriginal name. Ms S. Cowan prepared the specimen. This
paper has benefited considerably from comments by an
anonymous referee, which assisted in the clarification and
refinement of the ideas presented here.
Boles, W. E. (1992). Revision of Dromaius gidju Patterson and Rich,
1987, with a reassessment of its generic position. In ‘Papers in Avian
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Boles, W. E. (1997). Hindlimb propor tions and locomotion of
Emuarius gidju (Patterson & Rich, 1987) (Aves: Casuariidae).
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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
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Miller, A. (1963). Fossil ratite birds of the late Tertiary of South
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Fig. 2. Chronological occurrence of Dromaius and Emuarius, based
on Miller (1963), Patterson and Rich (1967), Boles (1992, 1997) and
this work. The Recent dwarf species D. ater and D. baudinianus have
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A new emu from the late Oligocene 321
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Manuscript received 23 October 2000; accepted 2 March 2001
... All three species inhabit the island of New Guinea, and the Southern Cassowary's range extends into northeastern Queensland, Australia, and some adjacent islands. No casuariiform fossils are known before the Late Oligocene [333], and thus far there is no indication that any other palaeognath lineage has ever been present in Australia (Figure 7, Table 6). One of these early fossil Casuariiformes, Emuarius gidju [337], had a temporal range spanning from approximately 24 Ma to 15 Ma and is known from a large number of specimens [341]. ...
... Emuarius guljaruba, from the 24.1 Ma late Oligocene Etadunna Formation [333][334][335][336], is known from a single complete left tarsometatarsus [333]. It is larger than E. gidju and most likely a separate species, but its allocation to Emuarius remains provisional because no femur has yet been discovered. ...
... Emuarius guljaruba, from the 24.1 Ma late Oligocene Etadunna Formation [333][334][335][336], is known from a single complete left tarsometatarsus [333]. It is larger than E. gidju and most likely a separate species, but its allocation to Emuarius remains provisional because no femur has yet been discovered. ...
Full-text available
The extant diversity of the avian clade Palaeognathae is composed of the iconic flightless ratites (ostriches, rheas, kiwi, emus, and cassowaries), and the volant tinamous of Central and South America. Palaeognaths were once considered a classic illustration of diversification driven by Gondwanan vicariance, but this paradigm has been rejected in light of molecular phylogenetic and divergence time results from the last two decades that indicate that palaeognaths underwent multiple relatively recent transitions to flightlessness and large body size, reinvigorating research into their evolutionary origins and historical biogeography. This revised perspective on palaeognath macroevolution has highlighted lingering gaps in our understanding of how, when, and where extant palaeognath diversity arose. Towards resolving those questions, we aim to comprehensively review the known fossil record of palaeognath skeletal remains, and to summarize the current state of knowledge of their evolutionary history. Total clade palaeognaths appear to be one of a small handful of crown bird lineages that crossed the Cretaceous-Paleogene (K-Pg) boundary, but gaps in their Paleogene fossil record and a lack of Cretaceous fossils preclude a detailed understanding of their multiple transitions to flightlessness and large body size, and recognizable members of extant subclades generally do not appear until the Neogene. Despite these knowledge gaps, we combine what is known from the fossil record of palaeognaths with plausible divergence time estimates, suggesting a relatively rapid pace of diversification and phenotypic evolution in the early Cenozoic. In line with some recent authors, we surmise that the most recent common ancestor of palaeognaths was likely a relatively small-bodied, ground-feeding bird, features that may have facilitated total-clade palaeognath survivorship through the K-Pg mass extinction, and which may bear on the ecological habits of the ancestral crown bird.
... Qld: Riversleigh LSO, Hiatus South, Patterson and Rich (1987), White Hunter Boles (1992, 1997c, 2001a Meredith (1991) gives no other clues about these birds; their diversity is documented later in the record. The Graculavidae is a potentially unnatural assemblage of unrelated forms with similar postcranial skeletons, which resemble that of the living stone-curlews (Burhinidae) (Olson and Parris, 1987). ...
... The presence of several taxa of the palaeognathous Casuariidae (Emuarius, Dromaius) at the same time is strongly indicative that this lineage had been established well before it began to diversify in Australia (Patterson and Rich, 1987;Boles, 1992Boles, , 2001a. Results from DNA sequencing imply that the closest relatives to the Casuariidae among living birds are the kiwis (Apterygidae) of New Zealand (Cooper et al., 1992;van Tuinen et al., 1998;Haddrath and Baker, 2001). ...
... Casuariidae Boles (1992Boles ( , 1997aBoles ( , 2001a Stirling (1913), Stirling and Zietz (1896, 1900, Rich (1979) Miller (1963a), Rich et al. (1987) There is no fossil evidence of this. The marsupial fauna would have been constrained in the same way, although with even less chance of colonization from outside. ...
... Chionoides australiensis is only the second shorebird to be described from the late Oligocene-early Miocene lake deposits of South Australia (see De Pietri et al. 2015). This rich, South Australian avifauna also includes palaeognaths (Boles 2001), a megapode (Boles & Ivison 1999), anseriforms (Worthy 2009;De Pietri et al. 2016b), flamingos and palaelodids (Miller 1963;Baird & Vickers-Rich 1998), and cormorants and other waterbirds (Miller 1966;Worthy 2011Worthy , 2012. As with N. sansomae, the chionoidean affinities of Chionoides australiensis are supported by the ventral deflection of the medial portion of the acrocoracoid ('tuberculum brachiale'), among other features. ...
The Chionoidea are a small, southern hemispheric shorebird clade that today includes the Magellanic Plover (Pluvianellidae) and two species of sheathbills (Chionidae). Here we describe the first fossil remains attributable to this group. The two newly described species, the early Miocene Neilus sansomae gen. et sp. nov. from New Zealand and the late Oligocene Chionoides australiensis gen. et sp. nov. from South Australia, are overall more similar to sheathbills, but the mosaic of characters shared with both Chionidae and Pluvianellidae preclude referral to either lineage. Attribution of fossils this age to these lineages also conflicts with divergence dates based on molecular data, as the split between the Magellanic Plover and sheathbills is hypothesised to be more recent. We therefore suggest that these Australasian, plover-size species represent the first record of stem-group taxa within Chionoidea.
... Since the middle Miocene, Struthio constitutes the most common taxon in most African and Eurasian assemblages ( Sauer 1972, Mourer Chauviré et al. 1996, Hou et al. 2005). In Australasia, the oldest ratite record is of Emuarius gidju and E. guljaruba from the late Oligocene-early Miocene of South Australia ( Patterson & Rich 1987, Boles 1992, 2001). In New Zealand, the basal Apterygidae Proapteryx micromeros, and indeterminate Dinornithiformes were described from the early Neogene ( Tennyson et al. 2010, Worthy et al. 2013). ...
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Agnolin, F.L., July 2016. Unexpected diversity of ratites (Aves, Palaeognathae) in the early Cenozoic of South America: palaeobiogeographical implications. Alcheringa 41, xxx–xxx. ISSN 0311-5518. Ratitae is represented in South America exclusively by Rheidae. Recently, the oldest purported fossil rheid, Diogenornis fragilis, was attributed by several authors to various other ratite clades. A new revision of museum fossil specimens from Argentina has resulted in the discovery of several ratite specimens that clearly do not belong to Rheidae, but resemble other clades. The newly identified specimens derive from Paleogene and Miocene strata. The great diversity of non-rheid Patagonian ratites ended via extinction of several groups by the late Miocene, probably owing to enhanced aridity that also favoured the dispersal of arid-adapted rheids. The new specimens described here reinforce the hypothesis that the traditional vicariant biogeographical model, which proposes ratite clades originated exclusively before the breakup of the Gondwana supercontinent, is questionable owing to the unexpected diversity of various ratite clades in South America, and also in Europe and Africa. This might indicate that the history of Ratitae was more complex than previously envisioned. Federico L. Agnolin* [[email protected]], Laboratorio de Anatomía Comparada y Evolución de los Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Ángel Gallardo, 470 (1405), Buenos Aires, Argentina. *Also affiliated with: Fundación de Historia Natural ‘Félix de Azara’, Departamento de Ciencias Naturales y Antropología, Universidad Maimónides, Hidalgo 775 (C1405BDB) Ciudad Autónoma de Buenos Aires, República Argentina.
The affinities of the taxa included in the present chapter have long been—and for most parts still are—difficult to resolve. The Opisthocomiformes (hoatzins) remain a phylogenetic enigma and are recovered in disparate positions in different analyses of molecular data. Several other notoriously difficult-to-place taxa, such as the Columbiformes (doves), Musophagiformes (turacos), Cuculiformes (cuckoos), and Otidiformes (bustards), form a clade in analyses of molecular sequences, for which the name Columbaves was proposed. Opisthocomiformes and the taxa of the Columbaves resulted in close proximity to the Strisores (nightjars, swifts, hummingbirds, and allies) in some molecular analyses. The exact interrelationships between these birds are, however, controversially resolved in different analyses, none of which recovered a clade including all of the above taxa. Whereas the fossil record of the Opisthocomiformes and the taxa of the “Columbaves” is very sparse, the Strisores are abundantly represented in various Paleogene fossil sites in Europe and North America. These fossils not only shed light on the evolutionary history of the higher-level taxa they belong to but also show that various groups of the Strisores with a geographically restricted extant range had a much wider distribution in the past.
The three clades discussed in the following are obtained in varying positions in current phylogenetic analyses, and their inclusion in the present chapter is not meant to reflect close affinities. It should be mentioned, however, that some analyses supported a sister group relationship between the Mirandornithes and the Charadriiformes, and others recovered a clade including the Charadriiformes and the Gruiformes. Some extinct taxa of the Gruiformes are well represented, but the Mirandornithes and Charadriiformes have a rather scant early Paleogene fossil record even though various Mesozoic and early Paleogene fossils were identified as flamingos or “transitional Charadriiformes” by earlier authors.
The Tinamiformes were long considered to be the sister group of the flightless palaeognathous birds, which were classified as “ratites”. However, current molecular analyses congruently supported a clade including the Tinamiformes, Casuariiormes, and Apterygiformes. Accordingly, flightlessness must have evolved independently within several palaeognathous lineages, as has already been assumed by some earlier authors. The distribution of extant palaeognathous birds is mainly restricted to the Southern Hemisphere, but several fossil taxa were reported from the Paleogene of Europe and North America. Most interesting from an evolutionary point of view are various long-legged, crane-like birds from Eurasia and North America, which are likely to be stem group representatives of the Struthioniformes. Rheiformes and Casuariiformes have a Paleogene fossil record in their current ranges, whereas Paleogene fossils of the Tinamiformes, Dinornithiformes, Apterygiformes, and Aepyornithiformes have not yet been found.
Many readers will be acquainted with phylogenetic terminology and avian osteology, and it is beyond the scope of the present work to provide an in-depth overview of these topics, each of which could fill a book on its own. For those less familiar with essential terms and definitions, these are outlined in the present chapter, which also introduces major features of the skull and some of the limb and pectoral girdle bones. Current hypotheses on the interrelationships of extant birds are reviewed, which constitute a phylogenetic framework for the study of fossil taxa. In order to set the following chapters on Paleogene birds into a full context, the Mesozoic fossil record of neornithine birds is furthermore discussed and an overview is given of major Paleogene fossil localities.
A new, diminutive species of dromaiine casuariid, Dromaius arleyekweke, is described from dispersed skeletal elements from the late Miocene Waite Formation of the Northern Territory, Australia. Remains of D. arleyekweke, sp. nov., have been found from the Ongeva Local Fauna in the Alcoota Scientific Reserve, but most remains come from the stratigraphically lower Alcoota Local Fauna where they form part of a densely fossiliferous series of mingled bone beds. Previously, remains of the new species had been referred to the basal dromaiine genus, Emuarius, but phylogenetic appraisal of new specimens indicates that the species shared a more recent common ancestor with the extant Dromaius novaehollandiae than it did with the type species of Emuarius, E. gidju. Consequently, the new species is placed in the genus Dromaius as its oldest known member. Derived characters of D. arleyekweke that are shared with D. novaehollandiae to the exclusion of E. gidju include a distally flattened external condyle of the distal end of the tibiotarsus and a more elongate tarsometatarsus, with marked transverse compression of the midshaft and a weakly impressed median sulcus on trochlea metatarsi II. Casuariid evolution shows a trend of increasingly cursorial hind limb proportions on the emu lineage, but D. arleyekweke has a tarsometatarsus that is more elongate than that of D. novaehollandiae. This implies nonlinear evolution of cursoriality in dromaiines and that D. arleyekweke evolved extreme cursorial proportions independently of D. novaehollandiae, or that a high degree of cursoriality evolved early in Dromaius and was reversed in the Pliocene D. ocypus.
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The recently extinct Malagasy elephant birds (Palaeognathae, Aepyornithiformes) included the largest birds that ever lived. Elephant bird neuroanatomy is understudied but can shed light on the lifestyle of these enigmatic birds. Palaeoneurological studies can provide clues to the ecologies and behaviours of extinct birds because avian brain shape is correlated with neurological function. We digitally reconstruct endocasts of two elephant bird species, Aepyornis maximus and A. hildebrandti, and compare them with representatives of all major extant and recently extinct palaeognath lineages. Among palaeognaths, we find large olfactory bulbs in taxa generally occupying forested environments where visual cues used in foraging are likely to be limited. We detected variation in olfactory bulb size among elephant bird species, possibly indicating interspecific variation in habitat. Elephant birds exhibited extremely reduced optic lobes, a condition also observed in the nocturnal kiwi. Kiwi, the sister taxon of elephant birds, have effectively replaced their visual systems with hyperdeveloped olfactory, somatosensory and auditory systems useful for foraging. We interpret these results as evidence for nocturnality among elephant birds. Vision was likely deemphasized in the ancestor of elephant birds and kiwi. These results show a previously unreported trend towards decreased visual capacity apparently exclusive to flightless, nocturnal taxa endemic to predator-depauperate islands.
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Dromaius gidju Patterson and Rich 1987, from the Mio­ cene Kurjamarpu local fauna of central Ausrralia, was described on the basis of associated hindlimb elements. New hindlimb material from the type locality and from Oligocene/Miocene deposits in Riversleigh, northwestern Queensland, are referred ro this taxon. Tibiotarsal and tarsometatarsal remains of D. gidju are more similar ro those of emus than those of cassowaries, whereas the femora are more similar to femora of cassowaries. All hindlimb elements of D. gidju show some affinity ro both cassowaries and emus. The combination of hindlimb characters indicates an earlier stage in the development of increased cursoriality, so [ propose a new genus for this taxon, Emuarius, which is interpreted ro be nearer the mutual ancesror of the emu and cassowary lineages than any other described form.
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Using proximal and distal fragments, the length of the tarsometatarsus of Emuarius gidju is estimated and compared to that of other hindlimb elements. From these proportions and other hindlimb morphology, the inferred locomotory mode of E. gidju is compared with Recent casuariids. Emuarius gidju appears to have been more cursorially adapted than Casuarius and dwarf Dromaius, suggesting at least some open habitat in the Riversleigh palaeoenvironment. Using the relationship between weight and least circumference of the femur and tibiotarsus in Recent birds, the weight of E. gidju is suggested to have been 19-21kg.
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Field work recently completed in the Lake Eyre Basin, South Australia, has resulted in the development of a land mammal (marsupial) biostratigraphy of the Etadunna Formation. Whereas traditional interpretations of the age of this sequence suggest it is about 15 m.y. old, new information indicates that the Etadunna likely is 24–26 m.y. old. In either case, it appears possible to document a four-fold fossil mammal zonation of this rock unit at lakes Palankarinna, Kanunka, Pitikanta, and Ngapakaldi, in a composite section of strata that spans at least 30 m. Magnetostratigraphic data for the same succession are generally consistent with the correlation of the Etadunna Formation sites at Lake Palankarinna with of those at lakes Kanunka, Pitikanta, and Ngapakaldi to the north, as based on paleontological information. The magnetic polarity zonation of these Etadunna Formation strata is consistent with a correlation to the world magnetic polarity time scale at about 24–26 m.y. This is the first fine-scale zonation based on fossil land mammals for strata of late Oligocene age in Australia. The combined mammal and magnetic data show promise of developing the Etadunna Formation as a reference standard for land mammal correlations within Australia and the relation of these to land mammal zonations beyond the Australian continent.