Calede et al.—Ecomorphology of Leptarctus oregonensis
Table 5. Scores of taxa included in the principal component analysis and the canonical variate analysis as well as eigenvector values of morphological indices included in the principal component analysis.
Genus Aonyx
Arctonyx
Enhydra Gulo Gulo
Ictonyx
Leptarctus Lontra Martes Meles
Mellivora Mephitis Mephitis Mustela Mydaus Neovison Procyon Spilogale Taxidea Taxidea
Bassariscus Eira
collaris astutus barbara lutris gulo gulo
striatus
oregonensis canadensis americana meles
javanensis vison lotor
capensis mephitis mephitis putorius
P4LB/P4W P4PM/P4W PRBL/P4W M1BL/M1W M1LL/M1W
putorius taxus taxus
Species capensis
PC1
−0.911530614 0.085914478 0.832440664 −2.368483476 1.852748264 −2.030140212 2.620096805 −0.608973297 1.998590696 1.692836563 −0.468252994 −0.325773921 0.51682178 0.39878171 0.49847656
1.144645841 1.647203135 −0.519195735 −1.304719953 1.461062243 −2.066374582 −1.94593127 −2.800651525 0.39355477 1.041334508 −2.034587463 1.82016016
PC2
0.252596813 0.821865267 −0.129191698 −0.88507069 −3.276707452 −0.38395489 −0.677495972 0.322106142 2.047765907 −0.12329943 −0.059244871 0.921151411 −1.673780322 0.821248443 0.385021739 0.287538968 1.601989345 0.151240109 −0.887987831 1.735136404 −0.515202488 −0.735724903 0.422186372 0.670732562 0.181859122 0.541679592 0.213042194
ecology of L. oregonensis. The dental and bullar morphologies of mustelids are critical to understanding their phylogenetic relationships (Wolsan, 1993; Wang et al., 2004; Robles et al., 2010). UOMNH F-35458 provides new information on the morphology of the tympanic projections of L. oregonensis. These tympanic projections are most similar to those of L. ancipidens from the Hemingfordian of Florida. Nevertheless, the tympanic projections of the two taxa differ by the complex dorso-posterior morphology of the projections in L. oregonensis. This morphology is unique to L. oregonensis. The dental morphology of L. oregonensis is also most similar to that of L. ancipidens. These combined morphological simila- rities in bullar and dental morphology likely reflect a close relationship between L. oregonensis and L. ancipidens. These two taxa have been suggested before to be synonyms (Olsen, 1957), but Baskin (1998, 2005) and Korth and Baskin (2009) recognized L. oregonensis and L. ancipidens as different based on the more primitive dentition and the larger size of L. ancipidens (Korth and Baskin, 2009). The different morphologies of the tympanic projections of the bullae we describe herein confirm that latter interpretation. The two taxa are also differentiated by dental characters of the P4 and M1, including a weaker parastyle and smaller hypocone in the P4 of L. oregonensis and aM1 wider than long with a stronger lingual cingulum in L. ancipidens than in L. oregonensis (Downs, 1956; Olsen, 1957). In addition to interspecific differences, UOMNH F-35458
also provides the opportunity to assess the intraspecific variation within Leptarctus oregonensis. UOMNH F-35458 cannot be distinguished in dental or cranial morphology from the type specimen LACM (CIT) 206. However, there are several differ- ences in cranio-dental morphology between UOMNH F-35458 and AMNH 18241. These differences are concentrated in the frontals, cranial foramina, auditory region, and the P4. The frontals of the Olcott Formation specimen are flatter than those
CV1
3.010792 −5.18304 −4.51498 −2.30036 −0.16584 7.499997 −2.24381 −3.01527 3.919618 2.428348 2.69331 4.018278 −2.46399 −2.40093 2.451315 1.544694 −3.04604 −2.65708
−3.3393
0.788451 2.028929 0.946916
CV2 −0.2524 −0.616
−1.8048 −0.21806 −0.76377 −0.7393 −1.25203 0.424547 −0.92224 0.159057 −1.12248 1.390738 −1.04986 2.603353 0.963185 −0.53943 −1.22042
1.593181 1.60614
-0.40011 1.290391 0.870301
301
of the newly described Mascall specimen. The parasagittal crests they bear originate farther posteriorly in the Olcott Formation specimen and diverge posteriorly rather than remaining parallel to one another as in UOMNH F-35458. The infraorbital foramen is rounder and larger inUOMNH F-35458. The mastoid process and the eustachian canal are larger in UOMNH F-35458. The dentary-squamosal articulation is stronger in UOMNH F-35458. The width of the posterior-most basin of P4 of the Olcott and Mascall specimens differ with the former in exhibiting a larger basin. The paracone is higher in UOMNHF-3554. Additionally, the proportion of theM1 differs between the two specimens, with the molar of the Mascall specimen squarer than that of the Olcott Formation specimen. Nevertheless, the two specimens likely represent
individuals from a single species. Korth and Baskin (2009) proposed that there could be sexual dimorphism in Leptarctus oregonensis. They suggested that this sexual dimorphism might involve L. primus and L. oregonensis. The combination of differences in the tympanic and dental morphologies between the two taxa supports those as strictly different species. It may be that the differences in morphology between the specimens from the Mascall and Olcott formations represent sexual dimorphism, which has been documented in many species of extant mustelids (Lee and Mill, 2004 and references therein). However, the concurrent morphologies among the Mascall specimens and among the Great Plains specimens may support, instead, the hypothesis that this intraspecific variation represents variation over the species’ geographical or temporal range (the Olcott and Mascall specimens may not be exactly con- temporaneous). Additional specimens are needed to settle this issue. This additional material of Leptarctus oregonensis
suggests that early leptarctines were crushing animal-dominated omnivores. The skull of L. oregonensis is broad across the zygomatic arches. Broad crania are typically associated with
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204
