THE EVOLUTIONARY HISTORY AND PHYLOGENETIC RELATIONSHIPS OF THE SUPERFAMILY PLATANISTOIDEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 467

usually flat, and usually oval-shaped part of the premaxilla. This is a character of all
Odontoceti (Barnes, 1990:21; 2006:38, character 10; and see Au, 2002: Figure 1).
11. Posterolateral sulcus absent [0]; or present [1]. This sulcus originates from the
premaxillary foramen, traverses posterolaterally to the lateral side of the premaxilla,
and usually demarcates the anterolateral and lateral sides of the premaxillary sac
fossa (Barnes, 1978:13, 2006:38, character 11; modified from Muizon, 1988b; and
Geisler & Sanders, 2003:104, character 72).
12. Posteromedial sulcus of premaxilla absent [0]; or present [1]. This sulcus originates
from the premaxillary foramen, traverses posteromedially toward the medial side of
the premaxilla, and usually demarcates the anteromedial edge of the premaxillary sac
fossa (Barnes, 1978:13; 2006:38, character 12).
13. Anteromedial sulcus of premaxilla absent [0]; or present [1]. This sulcus originates
from the premaxillary foramen and traverses anteromedially toward the medial side
of the premaxilla (Barnes, 1978:13, 2006:38, character 13).
14. Lateral surface of maxilla dorsal to alveolar row and immediately anterior to
antorbital notch thickened and expanded laterally to form a flange [0]; or lateral
margin of maxilla immediately anterior to antorbital notch relatively thin and
anteroposteriorly nearly straight [1]. This character is present in Odontoceti only.
Most of the earliest-occurring Odontoceti (as exemplified by Agorophius pygmaeus,
see Fordyce, 1981) have this lateral expansion of the lateral margin of the maxilla,
and it is considered here to be a character that is shared among stem Odontoceti. The
loss of this lateral flare of the edge of the maxilla among more derived clades of
Odontoceti is a derived character state (Barnes, 2006:38, character 14).
15. Maxilla covers anterior part of supraorbital process of frontal and does not contact
nuchal crest [0]; or extends posteriorly so far as to make contact with the nuchal crest
[1]. For this analysis, we scored simply whether or not the maxilla reaches the nuchal
crest (Barnes, 2006:38, character 15; modified from Geisler & Sanders, 2003:104,
character 77).
16. Mesorostral groove open dorsally [0], or roofed over at least in part by the medial
margins of the premaxillae [1]. The structure is labeled by Rommel (1990: Figure 2),
and was explained by Barnes (2006:38, character 16). The plesiomorphic character
state is present in Agorophius pygmaeus (see Fordyce, 1981) and in Allodelphis
pratti (see Fig. 1A herein), and the derived character state is present in Zarhachis
flagellator (see Kellogg, 1924: pl. 1; and see Figure 9A herein) and in Platanista
gangetica (see Van Beneden & Gervais, 1868-1880:pl. XXXI, Figures 2a, 9a; and
see Figure 11A herein).
17. Right and left parietal bones make contact along their medial margins on the dorsal
surface of the brain case [0]; or right and left parietals are separated in dorsal
exposure of the cranial surface by posterior extension of maxillae to contact the
nuchal crest [1]; (see Barnes, 1990:21, node 17; 2006:38, character 17).
18. Ascending process of each premaxilla contacts only the lateral side of its respective
nasal bone [0]; or ascending process of premaxilla extends posteriorly to a point that
is posterior to the posterior end of its respective nasal bone [1]. The derived character
state is shown by the right premaxilla of the specimens of Zarhachis flagellator (see
Kellogg, 1926:pl. 2; and Figure 9A herein). (Character explained by Barnes,
2006:38-39, character 18.)