PalaeognathsAt the base of Neornithes (Cracraft and Clarke 2001; Figure 12.2), the Palaeognathae
include the flightless ratites—emu, ostrich, cassowary, and kiwi—as well as the volant
tinamous. Although controversy exists regarding precise relationships within
palaeognaths, especially within the ratites, most workers agree that tinamous are the basal
sister-taxon with respect to the remaining ratite birds (e.g. Cracraft 1974; Bledsoe 1988;
Lee et al. 1997; Haddrath and Baker 2001; Cooper et al. 2001; Figure 12.4). Despite
controversy surrounding the results of some molecular analyses, the only recent
morphological phylogenetic analysis to include these birds remains that of Lee et al.
(1997), although a number of their characters were derived from the earlier work of
Bledsoe (1988).
The known fossil record of these birds is extensive. Unwin (1993), for example, listed
first occurrences for palaeognath families that extend from at least the Lower Eocene to
Recent. Furthermore, some workers have postulated the presence of these birds in the
Mesozoic (e.g. Kurochkin 1999), but records remain problematic largely as a result of their
poor preservation (Hope 2002) and uncertain phylogenetic position (Chiappe and Dyke
2002). So far, little material from the Eocene has been considered within a phylogenetic
context, but the members of the ‘Lithornithidae’ (Houde 1988) and the taxon Palaeotis
weigelti are particularly poorly understood. Although known under a number of
alternative names since the 1840s, Houde’s (1988) analysis of the relationships of early
Tertiary lithornithids, such as Lithornis and Paracathartes, led to the proposal that these
forms represent part of a flighted basal divergence within the Palaeognathae (significant
because most of the extant members of this clade have lost the ability to fly). The affinities
of Palaeotis, on the other hand, have engendered much debate. Although, originally, this
taxon was named by Lambrecht (1928) from a single right tarsometatarsus, Palaeotis is
Figure 12.4 Consensus phylogeny depicting relationships among Palaeognathae on the basis of
morphological characters and including selected fossil taxa (Lithornis and Palaeotis; see text for details
and sources). Numbers listed at nodes correspond to characters as listed by Lee et al. (1997);
asterisks indicate fossil taxa scored on the basis of more than one specimen (see text for details).
274 GARETH J.DYKE