THE PLIOCENE (BLANCAN) ALWAYS WELCOME INN HYPOLAGUS

Brannon Farner and Jay Van Tassell

Science Department, Eastern Oregon University, One University Boulevard, La Grande, OR 97850, jvantass@eou.edu

Abstract:  The presence of an anterior reentrant on a right lower third Hypolagus premolar found in May 2010 at the Always Welcome Inn in Baker City, Oregon, suggests that the Always Welcome Inn hare is either H. oregonensis (first described in the ~6-7 m.y.-old McKay Reservoir fauna near Pendleton, Oregon) or H. ringoldensis (first described in the ~4.3 m.y.-old White Bluffs fauna from the Hanford, Washington, area. Measurements of the anterior-posterior length, width, and the incision of the posterior-external reentrant indicate that the Always Welcome Inn Hypolagus is most closely related to H. ringoldensis.  More specimens are needed to determine if the Always Welcome Inn Hypolagus is a form intermediate between H. oregonensis and H. ringoldensis.

Introduction

Van Tassell and others (2007) described three rabbit (hare) fossils from the Pliocene (~4.8-4.3 Ma) Always Welcome Inn fossil site in Baker City, Oregon: 1) a metatarsal or metacarpal, 2) a broken incisor, and 3) an upper first molar.  Van Tassell and others (2007) noted that the upper first molar resembles those of the hares Hypolagus gidleyi, one of the fossil hares found in the Hagerman beds of Idaho, and Hypolagus vetus, a species found in the Rattlesnake Formation of Oregon, but it was not possible to identify which species the Always Welcome hare belongs to because fossil hare classifications are based largely on lower second and third premolars, not upper first molars.

              Eastern Oregon University student Brannon Farner found a partial lower right jaw with a third premolar (p3) of the hare Hypolagus on May 26, 2010 in a cross-bedded sand layer 6.75-7 m above the base of the Always Welcome Inn sequence.  This new fossil (Figure 1) provides the information needed to decide which species the Always Welcome Inn Hypolagus belongs to.

Figure 1.  Jaw fragment (left) and occlusal view of lower right third molar of the hare Hypolagus, Eastern Oregon University

                 specimen EO-1210.

Methods

The hare jaw and tooth were photographed and then washed in distilled water and cleaned with a brush.  The jaw disintegrated during the cleaning and the tooth separated from the remaining jaw fragments.

              Measurements were made of the anteroposterior length (APL), the width (Wp3), the depth of the posteroexternal reentrant (PER), the depth of the anteroexternal reentrant (AER) and the angle of deflection of the PER were made off of these photographs (Figure 2 and Table 1).  The occlusal surface of the tooth was traced off of the photographs and the tracing was copied onto transparency paper and reversed for comparison with lower left p3s of common species of Hypolagus.

Figure 2.  Left:  Diagram showing the terminology of the occlusal surface of lower third hare premolar molars (modified 

                           from White, 1987).  The abbreviations are as follows:  AR = anterior reentrant; PER = Posteroexternal

                           reentrant; AER = Anteroexternal reentrant; TH = Thick enamel in PER; and TN = thin enamel in PER.

                 Right:  Diagram of the occlusal surface of a hare lower third premolar illustrating measurements were made

                          (modified from White, 1987).   The measurements are:  anteroposterior length F,G; width A-E; depth of

                           posteroexternal reentrant (PER) B-E; depth of anteroexternal rentrant (AER) C-E.  Note the line of 

                           orientation, D.

Table 1.  Comparison of the Always Welcome Inn Hypolagus lower third molar with

measurements by White (1987) of H. oregonensis and H. ringoldensis lower third molars.

Systematic Paleontology

Family LEPORIDAE Gray, 1821

Subfamily ARCHAEOLAGINAE Dice, 1929

Genus   Hypolagus Dice 1917

Diagnosis (from White, 1987, p. 430)-- Size small to medium; p3 with shallow to deep AER and deep PER, both filled with cement, and usually without AR.

Remarks--The Always Welcome Inn p3 has an anterior reentrant, a characteristic shown by only two Hypolagus species: H. oregonensis and H. ringoldensis (White, 1987).  H. oregonensis is found in the ~6-7 m.y.-old McKay Reservoir site in Pendleton, Oregon, ~90 miles northwest of the Always Welcome Inn and H. ringoldensis is found in the ~4.3 m.y.-old White Bluffs and ~3-2.8 m.y.-old Taunton localities near Hanford, Washington, 170 miles northwest of the Always Welcome Inn site (Gustafson, 1978; White, 1987; White and Morgan, 1995)

              The anteroposterior length (APL) of the Always Welcome Inn Hypolagus p3 is 3.85 mm, within the ranges of both H. oregonensis and H. ringoldensis cited by White (1987) but closer to the mean APL of H. ringoldensis than H. oregonensis.  The width of the third premolar (Wp3) is 3.09 mm, which is at the upper limit of the range of widths for H. oregonensis and close to the mean width of H. ringoldensis  The incision of the anteroexternal reentrant (AER) of the Always Welcome Inn p3 is 16.2%, within the range for both H. oregonensis and H. ringoldensis, and the incision of the posteroexternal reentrant (PER) is 56.6%, greater than the range for H. oregonensis and very close to the mean value for H. ringoldensis.  The PER deflection of the Always Welcome Inn p3 is ~9° in an anterior direction, within the range for H. ringoldensis.  The AER and PER of the Always Welcome Inn p3 are straight.  78% of H. ringoldensis p3s have straight AERs and 60% have straight PERs.  The AER and PER of the Always Welcome Inn Hypolagus are not crenulated, like 72% (AER) and 60% (PER) of the p3s of H. ringoldensis.  The thin enamel in the PER (TH) is straight in the Always Welcome Inn Hypolagus, like 36% H. oregonensis and 70% of H. ringoldensis p3s.  The anterior reentrant (AR) of the Always Welcome Inn Hypolagus is strongly incised, a characteristic shared by 40% of H. ringoldensis p3s.

Discussion and Conclusions

The overall characteristics of the Always Welcome Inn lower right third molar are most similar to H. ringoldensis.  This suggests a close tie between the ~4.8-4.3 Ma Always Welcome Inn and the ~4.3 Ma White Bluffs hares.  It is possible that the Always Welcome Inn Hypolagus is an intermediate form between H. ringoldensis from the McKay Reservoir fauna in Pendleton, Oregon, and the younger H. ringoldensis (Figure 3).  More Hypolagus teeth need to be found at the Always Welcome Inn site to test this hypothesis.

Figure 3.  Suggested phyologeny of North American Archaeolaginae modified from White (1987) to include the Always Welcome Inn Hypolagus (AWI).

Acknowledgments

              We are grateful to Richard and Lynne Langrell and their family for allowing us to dig fossils at the Always Welcome Inn and for their support and enthusiasm throughout the course of the Always Welcome Inn research.  We also appreciate the assistance of the members of Eastern Oregon University's spring 2010 Historical Geology class in unraveling the mystery of the identity of the Always Welcome Inn Hypolagus.

References Cited

Gustafson, E.P., 1978, The vertebrate faunas of the Pliocene Ringold Formation, south-central Washington:  University of Oregon, Museum of Natural History, Bulletin 32, p. 1-63.

Van Tassell, J., Bergey, E., Davis, C., Grimshaw, B., Kisselburg, J., Ledgerwood, R., Miller, S., Morris, C., Steele, J., Wehymiller, C., Ferns, M.L., Smith, G.R., McDonald, H.G., Mead, J.I., and Martin, R.A., 2007, Early Pliocene (Blancan) Always Welcome Inn local fauna, Baker City, Oregon:  Oregon Geology, v. 68, no. 1, p. 3-23.

White, J.A., 1987, The Archaeolaginae (Mammalia, Lagomorpha) of North America, excluding Archaeolagus and Panolax:  Journal of Vertebrate Paleontology, v. 7, no. 4, p. 425-450.

White, J.A., and Morgan, N.H., 1995, The Leporidae (Mammalia, Lagomorpha) from the Blancan (Pliocene) Taunton local fauna of Washington:  Journal of Vertebrate Paleontology, v. 15,no. 2, p. 366-374.