Sullivan et al., eds., 2011, Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin 53. 610 SYSTEMATICS OF THE MUSK DEER (ARTIODACTYLA: MOSCHIDAE: BLASTOMERYCINAE) FROM THE MIOCENE OF NEVADA DONALD R. PROTHERO Department of Geology, Occidental College, Los Angeles, CA 90041 Abstract—The North American musk deer (family Moschidae, subfamily Blastomerycinae) were an important element of many faunas during the Miocene. They were recently revised by Prothero (2008), who reduced dozens of named species to only 8 species distributed among 6 genera. Two samples from early-middle Miocene faunas of Nevada, however, were not assessed in the 2008 revision. These include the type series of Blastomeryx mollis Merriam, 1911, from the early Barstovian (early middle Miocene) Virgin Valley and High Rock faunas, and specimens from the late Hemingfordian (late early Miocene) Massacre Lake fauna that Morea (1981) thought represented a new genus and 1 or 2 new species. These specimens are re-examined in light of the improved sample size and taxonomy of other Miocene blastomerycines, and it is clear that neither study was based on inadequate comparisons with enough specimens. Based on the modern taxonomy of blastomerycines, these Nevada samples are assigned to Problastomeryx primus (Matthew, 1908), a common primitive early-middle Miocene blastomerycid in North America. Blastomeryx mollis Merriam, 1911 is rendered a junior synonym. INTRODUCTION mens were photographed with a Nikon 5700 digital camera, and edited in Photoshop. Cope (1874) described the first known fossils of North American Institutional abbreviations: AMNH = American Museum of musk deer. He based the taxon Blastomeryx gemmifer on a fragmentary Natural History, New York; F:AM = Frick Collection, AMNH; UCMP jaw with an m3 from the Barstovian of Colorado. Originally, he thought = University of California Museum of Paleontology, Berkeley; UCR = it was a small ruminant, possibly a primitive merycodont pronghorn. University of California, Riverside, vertebrate fossil collection (now But when Matthew (1908) described more complete material of curated at UCMP). Blastomeryx (now Problastomeryx) primus with enlarged upper canine tusks, it became clear that Blastomeryx was a cervoid of some kind. By SYSTEMATIC PALEONTOLOGY 1926, Matthew had described Machaeromeryx and noted its similarities Blastomeryx mollis Merriam, 1911 to musk deer, but did not formally transfer the group to the family Moschidae. Subsequent authors (reviewed by Prothero, 2008, p. 207) Type specimens: UCMP 11564, left ramus with p3-m3 (Fig. 1); assigned the blastomerycines to either the palaeomerycids (i.e., the North co-type, UCMP 11567, ramus with p4-m3; both from the lower Virgin American dromomerycines) or to various cervoid groups. Finally, Webb Valley beds (Merriam, 1911, fig. 57). and Taylor (1980) formally assigned the blastomerycines to the Referred material: From the Virgin Valley area (early Moschidae, and this assignment was followed by McKenna and Bell Barstovian), UCMP locality 1065: UCMP 11565, isolated m3; UCMP (1997, p. 421) and Prothero (2008). Due to this long-standing taxonomic 10661, dentary fragment with teeth; UCMP 11541, isolated tooth; confusion, a large number of blastomerycine specimens (especially jaws UCMP 11566, dentary fragment; UCMP 11665, maxilla with P2-3. and teeth with no diagnostic cranial appendages or large canines) were From the High Rock Canyon localities (early Barstovian), UCMP local- often confused with palaeomerycids, such as the dromomerycines, which ity 1107: UCMP 12609, jaw fragment with p3 and the alveolus of p2 are very similar in dental morphology to blastomerycines, but are very (figured in Merriam, 1911, fig. 58); UCMP 12607, jaw fragment. different in cranial features. In addition, the Berkeley online catalog refers UCMP 24301, a At the time of my blastomerycine revision (Prothero, 2008), I had horn core, to Blastomeryx mollis, which was collected by Chester Stock not yet seen the University of California material of blastomerycines in 1920 and identified by Ruben Stirton in 1944. However, this cannot be from the Miocene of Nevada (both UC Museum of Paleontology and correct since musk deer don’t have horns or antlers. It is instead prob- former UC Riverside collections) , so I commented (p. 210), “In addi- ably referable to one of the dromomerycids reported from the Virgin tion, there are numerous UCMP specimens that have not yet been stud- Valley beds by Merriam (1911). ied, but will probably prove to be B. gemmifer. Some are from the Virgin Discussion: Merriam (1911, p. 278-279) proposed the taxon Valley beds (e.g., UCMP 40998, 41013, 41020) and the High Rock Blastomeryx mollis based on a holotype specimen (UCMP 11564) con- Canyon localities (e.g., UCMP 12607, 12609, 24301), which are from sisting of a left mandibular fragment with p3-m3 from the “lower Virgin the early Barstovian of northwest Nevada.” Valley beds, Virgin Valley, Nevada,” collected in 1909 (Fig. 1). Merriam Since that time, I have studied these specimens of Miocene musk (1911) never illustrated the primary type specimen, UCMP 11564. deer and borrowed some of the material to make direct side-by-side Instead, he illustrated (1911, figs. 56-58, p. 279) the co-type, UCMP comparisons with the much larger and more complete collections in the 11567, a ramus with p4-m3, and two other referred specimens: UCMP AMNH. It is now possible to make some determinations about the 11575, an isolated m3; and UCMP 12609, a jaw fragment with p3 and taxonomic status of these poorly understood taxa. the alveolus of p2 (the latter from High Rock Canyon). As a diagnosis, he wrote: “in the slightly greater length of the tooth row, relatively larger METHODS size of the premolars or smaller size of the m3, and the absence of p1 immediately anterior to p2 the Nevada form differs from B. olcotti. From In January 2009, I examined specimens from several collections B. primus it differs in the oval form of p4, in a slightly longer tooth row, and made detailed measurements to determine whether the stated size and probably in the anteroposterior diameter of the premolars” (p. 279). comparisons in the literature were backed up by metric data. All metric Merriam (1911) mostly compared the material to Blastomeryx data, statistics and plots were generated in Excel spreadsheets. Speci- 611 FIGURE 1. Primary type specimen of “Blastomeryx mollis,” UCMP 11564, in A, lateral and B, crown views. Photos by P. Holroyd, courtesy UCMP. primus Matthew 1908, and Blastomeryx olcotti Matthew 1908, both of useful. The supposed loss of p1 (probably a retained dp1, as in many which are now considered synonyms of Problastomeryx primus by mammals) has proven to be highly variable across the ungulates, and no Prothero (2008, p. 212). As Stirton (1944, p. 641) noted, the large size, longer serves as a useful character (Prothero, 2005; Prothero and Sanchez, Palaeomeryx folds, unreduced premolars, and prominent protocones on 2008). The actual condition of the p1 in B. mollis is unknown, since the P2-3 suggest the specimens belong to a primitive taxon with relatively type material is too incomplete to determine its presence or absence. unreduced premolars and Palaeomeryx folds. However, Stirton suggested Merriam (1911) could only infer that the p1 was not immediately in that it be assigned to Parablastomeryx gregorii, a large Clarendonian front of the p2, but it was either separated by a diastema or absent. The taxon, which makes less sense than an assignment to the late Heming- “triangular form” of the p4 in B. mollis versus the “oval form” of p4 in P. fordian-Barstovian taxon Problastomeryx primus. For example, the length primus is also highly variable across the specimens when one examines of the tooth row and relatively unreduced premolar row (Fig. 2) places the much larger collections of musk deer in the AMNH collections. UCMP 11564 (the primary holotype) in the midst of the cluster of P. Thus, there is no reason to regard Merriam’s “Blastomeryx mollis” primus specimens or possibly within B. gemmifer, but outside the size as anything other than a junior synonym of Problastomeryx primus cluster of the much larger P. gregorii, or the much smaller P. advena. (Matthew, 1908). Likewise, Merriam’s (1911) comment about the small size of the m3 is The taxonomic status of the late not borne out by measurements of more specimens (Fig. 3). In size, the Hemingfordian Massacre Lake Blastomerycinae m3 overlaps not only with P. primus but also with P. advena and B. gemmifer, so this character is not very diagnostic. In an unpublished UCR doctoral dissertation, Morea (1981) ana- The other characters that Merriam (1911) mentioned are not very lyzed the late Hemingfordian Massacre Lake fauna (UCMP locality 612 dissertations in their databases. Since this paper analyzes the taxonomic status of the early-middle Miocene musk deer of western Nevada, it is appropriate to examine Morea’s unpublished taxonomy and see if it is justified and should be formally published, or whether it is invalid. Morea (1981, p. 180-188) provided detailed descriptions of all the UCR material (now in the UCMP) he referred to his new genus and made numerous comparisons with the UCMP material from the Virgin Valley. Unfortunately, however, he apparently did not have the time or resources to compare his material with the much better collections in the AMNH. Such comparisons might have been difficult in any case because the taxonomy of blastomerycines has been a mess since the 1930s, with dozens of invalid taxa that were sorted out by the revision of Prothero (1998). In addition, Morea seemed to confuse these specimens with palaeomerycids and make inappropriate comparisons to material from an entirely unrelated family, a common problem before Webb and Taylor (1980) clarified the differences between Moschidae and the aletomerycine and dromomerycine Palaeomerycidae. Thus, Morea’s comparisons and diagnoses break down when the much larger collections of the AMNH (mostly from Great Plains localities worked by the Frick Laboratory, FIGURE 2.