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TITLE: Systematics, stratigraphy, and chronology for mammalian fossils (Late Arikareean to Hemingfordian) from the uppermost John Day Formation, Warm Springs, Oregon
AUTHOR: Lowell Dingus
JOURNAL: PaleoBios
PUBLISHED: Jan 31, 1990
NOTES: no. 47-48
ABSTRACT: Eighteen taxa of fossil mammals were collected from three geographic clusters of localities with Member I, the stratigraphically highest member in the western facies of the John Day Formation near Warm Springs, Oregon. The taxa include: Archaeolagus cf. macrocephalus, Mesogaulus aff. M. vetus, Entoptychus individens, ?Palaeocastor, Tomarctus or Euoplocyon, Parahippus aff. P. leonensis, Parahippus pawniensis, Anchitherium sp., Archaeohippus sp., cf. Floridaceras whitei, Cynorca sociale, Merychochoerus cf. matthewi, Merychyus (Merychyus) cf. arenarum, Merychyus (Merychyus) calaminthus, Michenia deschutensis n. sp., cf. Hypertragulus, Leptomerycini, Barbouromeryx (Bouromeryx) submilleri. Based on biochronologic correlations, nine taxa suggest a late Arikareean age for the fauna from Warm Springs: Entoptychus individens, Archaeolagus cf. macrocephalus, Merychyus cf. arenarum, Merychyus calaminthus, Merycochoerus cf. matthewi, Michenia deschutensis n. sp., and probably ?Palaeocastor, cf. Hypertragulus, and Leptomerycini. The new species of Camelidae, Michenia deschutensis, represents an intermediate stage of evolution between Michenia exilis and Michenia agatensis from the late Arikareean faunas of the Marsland (= upper Harrison) Formation of Nebraska. One taxon, Parahippus aff. P. leonensis, appears to be more primitive than its early Hemingfordian relative, P. leonensis. Three taxa are most closely related to early Hemingfordian forms: Mesogaulus aff. M. vetus, Parahippus pawniensis and cf. Floridaceras whitei. Only one form appears to be most closely related to a late Hemingfordian taxon, Barbouromeryx (Bouromeryx) submilleri. Six stratigraphic sections were measured to order the localities superpositionally; however, lithostratigraphic correlations have not yet been clearly established in all cases. Although the evidence is sketchy, two distinct biostratigraphic levels may be recognizable, one dominated by late Arikareean taxa and the other characterized by younger, possibly Hemingfordian, taxa. Two K-Ar age determinations were obtained from plagioclase phenocrysts contained within tuffs interbedded in the sections. The stratigraphically lower tuff, more closely associated with the late Arikareean forms, yielded an age of 22.7 ± 2.7 Ma, whereas the stratigraphically higher tuff, more closely associated with the possible Hemingfordian forms, yielded an age of 23.4 ± 3.3 Ma.
COLLECTION: PaleoBios Archive Public
ID: 197

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