Protospermophilus, GAZIN, 1930

Maguire, Kaitlin Clare & Schmitz, Joshua X. Samuels and Mark D., 2022, The fauna and chronostratigraphy of the middle Miocene Mascall type area, John Day Basin, Oregon, USA, PaleoBios 35, pp. 1-51 : 20

PROTOSPERMOPHILUS GAZIN, 1930

Protospermophilus oregonensis DOWNS, 1956

Holotype —Left dentary with i1, p4 through m3 and without coronoid and condylar processes, UCMP 39093 .

Paratype —Left p4, UCMP 40241 .

Occurrence — UCMP V 4828.

Description —The type and paratype are described in Downs (1956) and Black (1963).

Remarks — Downs (1956) assigned the species to Arctomyoides Bryant, 1945 and Black (1963) reassigned it to Protospermophilus . The locality, UCMP V4828, is in deposits typical of a marginal lacustrine environment and possibly from the earliest sections of the formation ( Downs 1956). We did not visit this site because it is on inaccessible private land; however, the other Mascall sites in the area (which were visited) are in the Lower Mascall, consistent with the interpretation in Downs (1956).

Protospermophilus malheurensis GAZIN, 1932

FIG. 10

Referred specimen —Left M1, JODA 6416.

Occurrence —JDNM-4.

Description —The M1is quadrate with four transverse lophs. It is assigned to this taxon based on the following: all of the lophs unite at the protocone; the anteroloph is convex anteriorly and attaches to the protocone lingually; the protoloph is straight and has a small protoconule; the metaloph is convex posteriorly, has a distinct metaconule and unites with the protocone, but narrows dramatically lingually; the posteroloph is expanded lingually to form an incipient hypocone ( Goodwin 2008), is convex posteriorly and outward from the protocone, and unites with the metacone labially. There is a small mesostyle between the paracone and metacone.

Remarks —This is the first occurrence of this species in the Mascall Formation. It was recovered as float 2 m below the Mascall Tuff in the type area. The species was originally described as Sciurus tephrus by Gazin (1932) from the contemporaneous Skull Springs locality (Butte Creek Volcanis Sandstone Formation) in southeastern Oregon.

Figures

Figure 10. Protospermophilus malheurensis left M1 in occlusal view, JODA 6416. Scale bar=1mm.