Bretzia Fry and Gustafson, 1975

Emery-Wetherell, Meaghan M. & Schilter, Joseph F., 2020, A new early occurrence of Cervidae in North America from the Miocene-Pliocene Ellensburg Formation in Washington, USA, Palaeontologia Electronica (a 08) 23 (1), pp. 1-11 : 3-6

Bretzia Fry and Gustafson, 1975 cf. Bretzia sp.

Referred specimens. UWBM VP 117138 , a partial right mandible with m2 and m3, and associated p2. Comparative material. We compared this specimen to jaws of extant Odocoileus hemionus from the state of Oregon that are curated at the University of Oregon Museum of Natural History : B-21654, B-21655, B-21660, B-21672, B-21677, B-

EMERY-WETHERELL & SCHILTER: NEW OLD DEER FROM WASHINGTON

21681, B-21687, B-21688, B-21690, and B-21693. Measurements and character coding are available in Appendix 1.

Occurrence. Locality C2907, a vertical outcrop of the Ellensburg Formation and Thorp Formation, capped by Pleistocene loess and soils. Other nondiagnostic material was found at the locality, including bone scraps and a disassociated fragment of enamel. All vertebrate material was found in the paleosol underlying the Ellensburg gravel deposits.

Description. The strong ectostylid on m2 and m3, clear molar metastylids, and unfused molar postmetacristid and pre-entocristid place this mandible firmly in the family Cervidae . Of the three species previously known from the Pliocene and Pleistocene of Central Washington, UWBVM VP 117138 is close in size to both Bretzia pseudalces and Odocoileus ensifer ( Fry and Gustafson, 1975) . Odocoileus ensifer is very similar in size and morphology to Odocoileus hemionus ( Fry and Gustafson, 1975) , and may be a junior synonym ( Anderson and Wallmo, 1984). Given this and the lack of dental material for Odocoileus ensifer , we compared our material to Odocoileus hemionus as per Gustafson (2015), as well as Odocoileus lucasi as figured in Morejohn and Dailey (2004). Bretzia nebrascensis ( Gunnell and Foral, 1994) is also a possibility, but only antlers have been described, and thus a comparison with our material was not possible. Eocoileus gentryorum (Webb, 2000) and Capreolus constantini (Vislobokova et al., 1995; Jiménez-Hidalgo and Bravo-Cuevas, 2014) are also considered here.

The measurements taken on both molars of UWBM VP 117138 are within two standard deviations of all measurements of Odocoileus , Eocoileus , and Capreolus molars ( Table 1). Two standard deviation contain 95 % of possible measurements in a normal distribution (Zar, 1999), and thus is useful as a cutoff for expected variations from the average size. Molar widths of UWBM VP 117138 are within two standard deviations of the measurements taken on the molars of Bretzia , but are smaller than two standard deviations of the lengths reported by Gustafson (2015). Artiodactyl teeth do decrease in length as they are worn ( Emery-Wetherell and Davis, 2018), and the significantly worn molars of UWBM VP 117138 may be the cause of their smaller size. It is also worth noting that the Coefficients of Variation (CV) provided by Gustafson (2015) for m2 and m3 lengths of Bretzia (m2: CV = 6.06 %; m3: CV = 4.67 %) are smaller than those we measured for Odocoileus (m2: CV = 7.81 %; m3: CV = 18.27 %), and are much smaller than is typical for artiodactyl teeth ( Emery-Wetherell and Davis, 2018). Given that, it is possible that the averages and standard deviation reported by Gustafson (2015) are conservative, and that measurements taken on UWBM VP 117138 are within two standard deviations of all dental measurements of both species.

Morphologically, the molars of UWBM VP 117138 are most similar to those of Bretzia ( Table 2). Both m2 and m3 of UWBM VP 117138 have a prominent ectostylid. Ectostylids are present in both Bretzia and Odocoileus , but are often absent in Odocoileus ( Gustafson, 2015) . Of the 10 Odocoileus jaws evaluated by the authors, none had an ectostylid as robust as that of UWBM VP 117138, five were lacking the m3 ectostylid, and six were lacking an m2 ectostylid.

Like Bretzia and Capreolus, UWBM VP 117138 has a cingulid on m3. Like Odocoileus hemionus , Odocoileus lucasi , and Eocoileus gentryorum, UWBM VP 117138 does not have a cingulid on m2 ( Table 2). Molar cingulids are highly variable in single-location samples of fossil artiodactyl dentition and their absence or presence may not be diagnostic ( Emery et al., 2016). It is, therefore, possible that while UWBM VP 117138 did not have an m2 cingulid, other members of the population did, and this absence may not be diagnostic.

The p2 of UWBM VP 117138 is within two standard deviations of the lengths and widths of Bretzia , Capreolus , and Odocoileus hemionus , but exceeds two standard deviations of the average width of Eocoileus and is nearly half the length of Odocoileus lucasi ( Table 1). The CV of p2 widths of Eocoileus reported by Vislobokova (1995) was 9.6 %, which is similar to the measured variation in Odocoileus in this study and is closer to what is expected for a mid-sized artiodactyl ( Emery-Wetherell and Davis, 2018), and therefore the difference in size between our specimen and Eocoileus is likely biologically meaningful. Odocoileus lucasi is considerably larger, with a p2 length approximately twice as long as any of the other species we considered - on par with the size of Cervus elaphus . This is far outside the expected size range for our specimen, and disqualified O. lucasi as a possible identification.

Morphologically, the p2 has a strong paraconid, similar to Eocoileus and Bretzia , and dissimilar to Capreolus (Vislobokova, 1995; Webb, 2000; Gustafson, 2015). Gustfason (2015) reports the paraconid as being present in Bretzia , and either absent or weakly present in Odocoileus hemionus . In our sample of Odocoileus hemionus , five of nine specimens with a p2 had no obvious paraconid, two had a weakly present paraconid, and two had a prominent paraconid, confirming the findings of Gustafson (2015). The figured p2 of Odocoileus lucasi in Morejohn and Dailey (2004) is worn, but appears to have a prominent paraconid as well.

Overall, the specimen morphologically overlaps with many cervid species of the same age ( Table 2) and is similar in size to most as well ( Table 1). The closest morphological match is Bretzia or Odocoileus hemionus . As there is considerable morphological similarity to Bretzia , which is found in the nearby and similarly-aged Ringold Formation, we have tentatively assigned UWBM VP 117138 to cf. Bretzia .