Figure 1.
Location of fossil occurrences of Pelagiarctos.
Map of A) California and B) North America, and C) Map of southern California showing the location of Sharktooth Hill (Round Mountain Silt) and the “Topanga” Formation. Abbreviations: Az., Arizona; Nev., Nevada.
Figure 2.
Comparison of A) Pelagiarctos sp. (SDNHM 131041) in dorsal aspect, and the holotype specimen of Pelagiarctos thomasi (LACM 121501) in B) dorsal and C) lateral aspect.
Table 1.
Table of known fossils of Pelagiarctos. Pelagiarctos sp. is from the “Topanga” Formation (This study), while all other material listed is from the Sharktooth Hill Bonebed, Round Mountain Silt (Barnes, 1988).
Figure 3.
Left mandible of SDNHM 131041, Pelagiarctos sp. SDNHM in A) lateral, B) medial, and C) dorsal aspect.
Figure 4.
Right mandible of SDNHM 131041, Pelagiarctos sp. Mandible of SDNHM 131041 in A) lateral, B) medial, and C) dorsal aspect.
Table 2.
Measurements of Pelagiarctos sp., SDNHM 131041.
Figure 5.
Lower dentition of SDNHM 131041, Pelagiarctos sp. Lower premolars in A) labial, B) lingual, and C) occlusal aspect.
The M1 and P1 alveoli, and C1 and I3 are depicted in D) labial and E) mesial aspect.
Figure 6.
Dentition of SDNHM 131041, Pelagiarctos sp. A) Illustration of lower premolars in lingual aspect.
B) line drawing of P2 in lingual aspect, showing cusp homologies.
Figure 7.
Comparison of Pelagiarctos sp. mandible with other Miocene “imagotariine” odobenids.
A) Mandible of Pelagiarctos sp. (SDNHM 131041) in lateral (top) and dorsal (bottom) aspect; “Topanga” Formation, Orange County, California. B) Mandible of Imagotaria downsi (USNM 23858) in lateral (top) and dorsal (bottom) aspect; reflected image of right mandible; Santa Margarita Sandstone, Santa Cruz County, California. C) Mandible of Proneotherium repenningi (USNM 314628) in lateral (top) and dorsal (bottom) aspect; Astoria Formation, Lincoln County, Oregon. D) Mandible of Pontolis magnus (USNM 335563), in lateral (top) and dorsal (bottom) aspect; reflected image of right mandible; Empire Formation, Coos County, Oregon. Scale bars equal 5 cm.
Figure 8.
Strict consensus tree of odobenid relationships.
Bootstrap support and Bayesian posterior probabilities are labeled adjacent to nodes (above and below, respectively). Odobenidae and subfamilies and tribes within Odobenidae are labeled to the right. Extinct taxa are labeled with ‘†’.
Figure 9.
Hypothesized sequence of mandibular and dental character transformations during odobenid evolution.
Dental characters shown on left cladogram, and mandibular characters shown on right cladogram, with diagrams of mandibles adjacent to taxon names; white indicates unknown morphology. Character acquisition and loss mapped directly from results of cladistic analysis, with the exception of “short tooth row”, which was mapped a posteriori.
Figure 10.
Relationship between body weight and calculated trophic level among modern pinnipeds.
Taxa with strong sexual dimorphism are represented by separate points for male and female taxa. Note that the greatest body weight is associated with the highest and the lowest trophic levels, and the lack of a clear trophic level trend for lower body weights.