Class Mammalia Order Lagomorpha Family Ochotonidae

OCHOTONA

Specimens of Ochotona were recovered from six sites in Porcupine Cave (appendix 14.1): Badger Room, Generator Dome, table 14.1

North American fossil Ochotona of Pliocene (Latest Hemphillian and Blancan) and Early Pleistocene (Irvingtonian) Age

Location

Species/Morph

Reference; Remark

Hemphillian

McKay Reservoir

spanglei

Shotwell (1956); type

Blancan

Unwily Coyote

Small

P. Bjork (pers. comm., 1997)

Irvingtonian

Cape Deceit

whartoni,/large

Guthrie and Matthews (1971); type

Cathedral Cave

Small

C. J. Bell and J. I. Mead (field notes)

Cumberland Cave

Small

Guilday (1979); Mead and Grady (1996)

Hamilton Cave

Small

Mead and Grady (1996)

Porcupine Cave

Small

This chapter

Trout Cave

Small

Guilday (1979); Pfaff (1990, 1991); Mead and Grady (1996)

note: Rancholabrean-age localities are numerous, and descriptions of them can be found in Mead (1987) and Mead and Spaulding (1995). The small morph may also be referred to as O. princeps-like.

note: Rancholabrean-age localities are numerous, and descriptions of them can be found in Mead (1987) and Mead and Spaulding (1995). The small morph may also be referred to as O. princeps-like.

Mark's Sink, the Pit, Velvet Room, and Will's Hole. This chapter makes available the preliminary information about Ochotona from these localities. We are not positive that we have any taxon other than O. princeps. We have taken a liberal approach in describing these specimens by emphasizing subtle differences, particularly isolated teeth. The statistical study necessary to unequivocally differentiate the species has not been carried out and is beyond the scope of this chapter. Clearly what is needed for a satisfactory statistical analysis is abundant specimens from well-dated stratigraphic layers, but this is not possible for the present study. Examination of additional specimens may support the validity of the differences we highlight here, signaling a more complex evolutionary history of the pikas in North America. Alternatively, further material may indicate that the differences we note are merely geographic variation within a slowly evolving taxon.

OCHOTONA CF. O. PRINCEPS (RICHARDSON, 1828)

DESCRIPTION AND COMMENTS The specimens from Mark's Sink are from a medium to small pika, perhaps smaller than most of the extant O. princeps. The following are characteristics observed on all the mandibles from Mark's Sink. The ascending ramus of the mandible is somewhat short and wide, inclined slightly posteriorly. The coronar tubercle is well developed. The upper surface of the ascending ramus is wide anteriorly and becomes sharply narrow posteriorly. The angular part of the mandible is rather wide at its base. There is a well-developed crest on the base of the labial side. The angular opening is not deep and wide. Specimens DMNH 41347,

36492, and 37095 are small (alveolar lengths of p3-m3, respectively: 7.1, 7.2, 7.3 mm); however, some specimens from upper levels in Mark's Sink are about the same size, as is typical of O. princeps (see Mead and Grady, 1996:figure 2A). It appears that the pikas from deeper in the excavation might belong to a smaller form; however, this has not yet been documented statistically.

The size of the Lp3 (UCMP 173763) from the Pit corresponds to that of recent O. princeps. The anteroconid of the p3 is large, with wide confluence with the posteroconid (figure 14.2A). The anterointeral side of the anteroconid is much longer than on the other side. The rather short anteroexternal side has a very shallow depression. The enamel is developed on the anterior side of the anteroconid, being of almost the same thickness on both the anterointernal and anteroexternal sides. The anteroexternal and anterointernal folds between anteroconid and posteroconid are of the same depth and are filled with thin cement. The posteroconid is wider than long. Its lingual side, with a very shallow depression, is much shorter than the labial side. The posteroexternal fold of the tooth is filled with thick cement. Thick enamel surrounds the posteroconid, which is thin on its posterointernal portion (figure 14.2A).

Specimens from Will's Hole are all from a small ochotonid, as large as the extant O. princeps. The diastema of the specimens is short in comparison with that of modern specimens.

Specimens from the DMNH Velvet Room excavation are nearly identical in proportions to those from extant O. princeps. The ascending ramus is rather high with a developed coronar tubercle on the anterior face. The upper surface is wide on the anterior portion and becomes sharply narrow

P3

FIGURE 14.2 Drawings of select Ochotona teeth from Porcupine Cave. (A) Ochotona cf. princeps, Lp3 (UCMP 173763) from the Pit (G2 L10). (B) Ochotona sp. Trout Cave form, Lp3 (UCMP 173773) from the Pit (G1 L3). (C) Ochotona sp. Trout Cave form, Lp3 (in mandible; DMNH 10397) from the Velvet Room (G5 L7). (D) Ochotona sp. Trout Cave form, Rp3 (UCMP 173765) from the Pit (G1 L3). (E) Ochotona sp. Trout Cave form, LP3 (UCMP 173764) from the Pit (G3 L4). (F) Ochotona sp. Trout Cave form, RP3 (UCMP 173766) from the Pit (G3 L6).

posteriorly. In modern specimens this upper surface of the ramus is not as wide and gradually narrows posteriorly.

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