Orbital Form and Patterns of Covariation
Herpestids, felids, and pteropodids—all exhibit positive correlations between orbital convergence and skull size (also procyonids and tupaiids - Table 3).
6 To eliminate the chance that an enlarged masticatory complex in folivorous didelphimorphs would differentially influence the position of the lower orbital margin, and thus an evaluation of variation in orbital convergence across this clade (Cartmill, 1972), no such species are included.
7 Orbital convergence species means for four cheirogaleids and two tarsiids are from Ross (1995). Means for three galagids and two lorisids are based on adult data collected by the authors or Ross (1995). Linear dimensions for all nocturnal primate faunivores were taken by the authors.
Family, n |
Orbital |
Orbital |
Orbital |
convergence |
frontation |
convergence | |
versus |
versus |
versus orbital | |
nasion-inion |
nasion-inion |
frontation | |
chord4 |
chordb | ||
Felidae (31 taxa, 208 adults) |
0.257* |
—0.479**** |
0.261* |
Herpestidae (28 taxa, 183 adults) |
0.415***' |
-0.041ns |
0.309** |
Pteropodidae (64 taxa, 277 adults) |
0.644**** |
—0.207**^ |
0.112ns |
Procyonidae (11 taxa, 88 adults) |
0.560***' |
—0.662***f |
0.419* |
Tupaiidae (5 taxa, 21 adults) |
0.770***g |
—0.409* |
0.151ns |
a Significance levels: **** = p<0.01; *** |
= p< 0.05; ** = p< |
0.10; * = p< 0.15; ns |
= p< 0.15. |
b Comparisons versus other cranial measures differ little.
c When restricted to only diurnal species (n = 27) and thus a single activity cycle, r= 0.556 at p<0.01. d Due to two larger-sized outlier species, pteropodids exhibit a negative correlation between orbital frontation and size. With these data excluded, the correlation is no longer significant (p>0.15). eWhen restricted to only nocturnal species (n = 8) and thus a single activity cycle, r = 0.838 at p < 0.01. -This represents the value with one large-sized outlier species eliminated from the sample (n=10). Analysis of all 11 sister taxa results in a nonsignificant correlation (r = -0.273; p > 0.15). gWhen restricted to only diurnal species (n = 4) and thus a single activity cycle, r = 0.989 at p < 0.01.
b Comparisons versus other cranial measures differ little.
c When restricted to only diurnal species (n = 27) and thus a single activity cycle, r= 0.556 at p<0.01. d Due to two larger-sized outlier species, pteropodids exhibit a negative correlation between orbital frontation and size. With these data excluded, the correlation is no longer significant (p>0.15). eWhen restricted to only nocturnal species (n = 8) and thus a single activity cycle, r = 0.838 at p < 0.01. -This represents the value with one large-sized outlier species eliminated from the sample (n=10). Analysis of all 11 sister taxa results in a nonsignificant correlation (r = -0.273; p > 0.15). gWhen restricted to only diurnal species (n = 4) and thus a single activity cycle, r = 0.989 at p < 0.01.
Of these three clades, only larger-sized pteropodids and herpestids with greater convergence tend to have postorbital bars (Figure 7). Contrary to predictions of the NVPH (Cartmill, 1970, 1972), felids do not show a link between postorbital bar formation and orbital convergence (Noble et al., 2000; Ravosa et al., 2000a).
Felids also exhibit a negative correlation between orbital frontation and skull size (also procyonids and tupaiids - Table 3), with postorbital bar formation bars tending to characterize only smaller, more frontated cats (Figure 8A). Herpestids with greater orbital frontation also tend to possess bony postorbital bars (Figure 8B). Pteropodids, however, do not exhibit this pattern (Noble et al., 2000; Ravosa et al., 2000a). In addition, size-related decreases in orbital frontation are not observed in the less-encephalized mongooses and fruit bats (cf., Figures 8B and 9).
Felids, basal euprimates, and extant primate nocturnal predators exhibit significantly greater orbital convergence than plesiadapiforms, tupaiids, der-mopterans, pteropodids, and herpestids (Figure 10; significant Y-intercept difference or transposition of the euprimate/felid LS line above that for the remaining mammalian clades - ANCOVA, p< 0.001) (Ravosa and Savakova, 2004; Ravosa et al., 2000a). In tupaiids, procyonids, and herpestids, nocturnal predators (Ewer, 1973; Nowak, 1999; Zeveloff, 2002) display higher
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Nasion-inion chord (mm) 30 40 50 60 70 80 Nasion-inion chord (mm)
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