The position of Palaeotis weigelti within the ratites is supported by this analysis on the
basis of the following derived characters (listed as given by Lee et al. 1997): 24 (obturator
process of the ischium fused with the pubis to form a complete obturator foramen); and
30 (anterior metatarsal groove [of tarsometatarsus] deep and narrow for its entire length).
Furthermore, and as seen in the Dinornithidae, Struthio and Rhea (Lee et al. 1997:203),
the external and internal cotylar surfaces of the tarsometatarsus are concave in Palaeotis
(derived state 2 for Lee et al. character 29). Additional characters hypothesized to support
this grouping, but not preserved in Palaeotis, include: 33 (surface of the anterior
interarticular area of the cnemial crest of the tibiotarsus mediolaterally compressed); and
38 (internal condyle of tibiotarsus projected anteriorly relative to external condyle in
distal view). However, several characters hypothesized on the basis of this analysis to be
derived within palaeognaths in general (i.e. Tinamidae and more derived terminals) are
also seen primitively in Palaeotis. These include the presence of posterior lateral processes
on the sternum (character 2) and a trochanteric crest on the femur that extends
proximally beyond the level of the iliac facet (character 41).
GalloanseraeAnseriformesThe Order Anseriformes comprises the extant waterfowl, the screamers, ducks, and
geese, and has a putative fossil record extending into the latest Cretaceous (e.g. Howard
1955; Olson and Parris 1987; Olson 1999). From the Lower Eocene Green River
Formation of North America comes perhaps the most famous of all fossil neornithines,
Presbyornis pervetus. For many years, Presbyornis was thought to be somehow ‘intermediate’
in its morphology, providing evidence for an evolutionary link between a number of
traditional avian orders by the time of the earliest Eocene (e.g. Olson and Feduccia 1980;
Feduccia 1995). The recent inclusion of Presbyornis within cladistic analyses of the
Anseriformes has demonstrated that this taxon can be placed well within the order,
closely related to the Anatidae (extant true ducks; Ericson 1997; Livezey 1997, 1998).
Because of the incompleteness of the putative Cretaceous records (Hope 2002), Presbyornis
and another Lower Eocene taxon, Anatalavis oxfordi Olson, present the earliest partially
complete fossil records for the Anseriformes (Figure 12.5).
On the basis of the analysis presented by Livezey (1997, 1998), I coded the preserved
cranial and postcranial morphology of Anatalavis oxfordi in light of the proposal made by
Olson (1999) that this taxon is basal within Anseriformes, closely related to the extant
magpie-goose Anseranas. Results of this analysis, the first to consider the relationships of
the London Clay taxon in a cladistic context, instead supports a more derived placement
for Anatalavis oxfordi within Anseriformes, as the sister taxon to Presbyornis and Anatidae.
Hence, two well-preserved anseriform taxa known from the Lower Eocene have been
placed convincingly within the order on the basis of cladistic analysis (Figure 12.5).
This placement for Anatalavis oxfordi within the Anseriformes is unambiguous, and on
the basis of a number of cranial features, including the presence of a long and ventrally
terminating lamina basiparasphenoidale (character 3 of Livezey 1997), this position is
recovered by parsimony analysis. Anatalavis is the sister taxon of the extant true ducks
276 GARETH J.DYKE