Halfway Hollow (Lapoint Member) (Eocene of the United States)

Where: Uintah County, Utah (40.2° N, 109.9° W: paleocoordinates 42.3° N, 100.7° W)

• coordinate based on political unit

When: Duchesne River Formation, Duchesnean (40.4 - 37.2 Ma)

• member-level stratigraphic resolution

Environment/lithology: terrestrial

Primary reference: O. A. Peterson. 1934. List of species and description of new material from the Duchesne River Oligocene, Uinta Basin, Utah. Annals of Carnegie Museum 23(7):373-389 [J. Alroy/J. Alroy/J. Marcot]more details

PaleoDB collection 16847: authorized by John Alroy, entered by John Alroy on 21.09.1998, edited by Jonathan Marcot

Creative Commons license: CC BY (attribution)

Taxonomic list

• lists of Kay 1957 and Emry 1981 do not pertain to individual localities in the Lapoint Mbr.; most of the other records are from Titanothere Quarry in Twelve Mile Wash, about two miles to the east
NOTE: this is NOT equivalent to the Halfway Fauna, synonym of the Dry Gulch Creek Member fauna (see)
zircon FT dates of 32.2 +/- 3.2, 28.7 +/- 2.0, 33.7 +/- 5.6, 32.9 +/- 4.5, 35.2 +/- 1.6, and 36.9 +/- 1.8 Ma reported by Bryant et al. 1989 are discordant with much more precise K-Ar and Ar-Ar dates reported by Prothero and Swisher 1992; best date is one of 39.74 +/- 0.07 Ma (Ar-Ar) for the Lapoint Tuff, "at the contact between the Dry Gulch Creek and Lapoint Members"
Lapoint Mbr. records of unclear status: "Diplobunops (?)" Peterson 1931d from "well up in the Duchesne... in Half-way Hollow"; "Dyscritochoerus lapointensis" type of Gazin 1956b; same as "Helohyus (?)" of Peterson 1934b from "Lapoint Horizon" (no other data) "Epitriplopus medius" Peterson 1934b: referred specimens from "well up in the Duchesne Oligocene... Lapoint horizon" (no other data, but not the Titanothere Quarry); apparently overlooked by Emry 1981, who excludes this species from the Lapoint Duchesnehippus intermedius Rasmussen et al. 1999b: new specimen from "the Lapoint Member" Protoreodon cf. pumilus Rasmussen et al. 1999b: new specimens from "the Lapoint fauna" Mytonomys robustus Wood 1962: "C.M. 9343 from the Duchesne River... Duchesnean"
I have failed to find any later mention of the first and third of these specimens (CM 11853 and 11916)
Mammalia
 Rodentia - Eomyidae
Protadjidaumo typus n. sp.4 Burke 1934 rodent
from "Lapoint horizon... Fourteen miles west of Vernal... one-half mile north of Vernal-Lapoint road"
 Rodentia - Cylindrodontidae
Pareumys guensburgi n. sp.2 Black 1970 rodent
coordinates show that this is in Halfway Hollow
 Perissodactyla - Hyracodontidae
Hyracodon medius1 Peterson 1934 odd-toed ungulate
 Perissodactyla - Rhinocerotidae
Penetrigonias dakotensis6 Peterson 1920 rhinoceros
"Lapoint fauna, Uinta Basin, Utah"
 Carnivora - Miacidae
Miocyon sp.3 Matthew 1909 carnivoran
"Miacidae or Amphicyonidae" of Emry 1981 from lower Lapoint Mbr. in Halfway Hollow; i.d. seconded by Hunt 1996
 Ungulata - Agriochoeridae
Agriochoerus maximus5 Douglass 1902 agriochoerid
lower Lapoint Mbr. in Halfway Hollow DUPLICATE REF 1438 or 1439