Sullivan et al., eds., 2011, Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin 53. 610 SYSTEMATICS OF THE MUSK (ARTIODACTYLA: : BLASTOMERYCINAE) FROM THE OF NEVADA

DONALD R. PROTHERO

Department of Geology, Occidental College, Los Angeles, CA 90041

Abstract—The North American (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 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 . 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 , 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 ) 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, 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. Bivariate plot of blastomerycine lower tooth rows (m1-3 molar plus Matthew’s and Cope’s original material) are considered. row length vs. p2-4 premolar row length). Symbols: Large solid diamond For example, Morea’s (1981) diagnosis of his new genus began = “Blastomeryx mollis;” small open squares = Blastomeryx gemmifer; with “premolars large relative to molars”. As noted by Prothero (1998) solid triangles = Problastomeryx primus; large open circles = Pseudo- and also above, the presence of a relatively long premolar row is a primi- blastomeryx advena; small solid diamonds = Parablastomeryx gregorii. tive character among blastomerycines, and occurs in Parablastomeryx and Problastomeryx, while the premolars are reduced in the rest of the blastomerycines. Unfortunately, none of the Massacre Lake specimens has a complete p2-4 preserved, but the m1 length of 29.2 mm places it in the size range of P. primus, B. gemmifer, and possibly P. advena (Fig. 2). A comparison of UCMP 319167 with the holotypes of Blastomeryx “medius” (now referred to B. gemmifer) and Parablastomeryx gregorii (Fig. 4) show that it is in fact a good match in size for the m1-3 and ramus dimensions of B. gemmifer, but the unreduced premolars are similar to the much larger taxon P. gregorii. Morea’s (1981) diagnostic characters of “reduced metastylid” and “hypoconid fold” are much more difficult to assess, since they are only preserved on relatively unworn teeth. The type material of “B. mollis” is too worn to tell if these characters justify the inclusion of Merriam’s taxon in Morea’s new genus. Examination of the material in the AMNH and F:AM collection shows that these characters are highly variable, present on some specimens of B. gemmifer and not on others from the same locality, and present even on Clarendonian forms like Parablastomeryx gregorii. Morea (1981) also mentioned the Palaeomeryx fold, which is a highly variable feature primitive in many ruminant teeth, and lost within later lineages (Prothero, 2008; Prothero and Liter, 2008). FIGURE 3. Bivariate plot of blastomerycine m3 dimensions. Symbols: large open triangle = “Blastomeryx mollis”; large open square = UCMP Finally, the “large and highly compressed ectostylid” appears to be 316459 from Massacre Lake; small solid diamonds = Longirostromeryx highly variable as well and can be found in some (but not all) specimens wellsi; small solid squares = Longirostromeryx clarendonensis; small in the much larger sample of B. gemmifer and in P. gregorii. In short, open triangle = Parablastomeryx gregorii; x = Blastomeryx gemmifer; there appear to be no diagnostic characters for the Massacre Lake sample small open circle = Pseudoblastomeryx advena; small solid circle = that are not either primitive for blastomerycines, highly variable, or Problastomeryx primus. impossible to determine on all but the least worn specimens. Likewise, there is no justification for inclusion of Merriam’s (1911) taxon “B. 6160, now dated at 16.4-17.3 Ma by Prothero et al., 2008) and described mollis” in a new genus based on the Massacre Lake sample. . three specimens of blastomerycine from locality RV7043: UCR 19167 Similarly, the proposed new species for the Massacre Lake sample [= UCMP 319167], a left mandible with p3-m2 and partial m3; UCR also seems unjustified. Morea (1981) only compared the Massacre Lake 16459 [= UCMP 316459], a right ramus with m3; and UCR 19223 material to Merriam’s Virgin Valley material, and not to any other [= UCMP 319223], an isolated right m1 or m2. Morea (1981) consid- blastomerycines from elsewhere in North America, so it suffers from ered these specimens to represent a new genus and species diagnosable insufficient comparisons and failure to account for variability within a by “premolars large relative to molars; lower molars with: robust population. Morea (1981,p. 180) distinguished the Massacre Lake sample metastylid; well-developed Palaeomeryx fold; hypoconid fold, and large from the Virgin Valley specimens based on only the following characters: and compressed ectostylid” (Morea, 1981, p. 180). He also referred “smaller in size; teeth more brachydont; premolars with robust Merriam’s “Blastomeryx mollis” to his new genus. Although Morea’s metaconids; molars with larger and more compressed ectostylids; and taxonomy was never formally published, the possible existence of a new less curved mandibular ramus.” The defining character of “smaller size” taxon of blastomerycine was noted in Table 1 of Prothero et al. (2008), is meaningless, since the m1-3 length of 29.2 mm actually falls com- and in some of the online database faunal lists for Massacre Lake. It is pletely within the size range of Blastomeryx gemmifer, Problastomeryx also becoming more common for compilers to use unpublished taxa from primus, and P. advena (Fig. 2). In some measures, like m3 dimensions 613 (Fig. 3), the Massacre Lake specimens are actually larger than the Virgin their curvatures cannot be reliably compared to more complete rami in Valley material and fall within the size range of the much larger the AMNH and F:AM collections. Clarendonian form P. gregorii. This is apparent when the specimens are Finally, Morea (1981, p. 187-188) designated all the upper teeth compared side-by-side with the better samples from the AMNH (Fig. from the same locality (RV7043) as yet another new species of his new 4), and the ramus most closely matches specimens of B. gemmifer or P. genus. He did not formally name this new species, because there were no primus in dimensions. lower teeth in this sample to compare with the majority of the taxa that The other cited characters are also non-diagnostic when enough are based on lower jaw and tooth characters. As he noted, the upper additional material is examined and variability is taken into account. The tooth material is somewhat larger than the lower teeth he assigned to his teeth of UCMP 319167 do indeed appear more brachydont than some new genus, and he actually compared it to the primitive palaeomerycid blastomerycines, but this may largely be due to greater wear, because of taxon Barbouromeryx, which is not a musk deer at all (Prothero and those of UCMP 316549, which is less worn, appear to be hypsodont Liter, 2008). In fact, the upper teeth show no real diagnostic features that and comparable to other blastomerycines. The character “premolars with rule out whether they are blastomerycines or palaeomerycids, so they robust metaconids” is highly variable and strongly affected by wear. could be assigned to a number of taxa. The majority of the diagnostic UCMP 319167 has premolars that are more worn, so the metaconids are characters listed by Morea (1981, p. 187-188) are found within the reduced to a robust pillar, but p4 of Merriam’s holotype of “B. mollis” normal range of variation of High Plains taxa such as B. gemmifer and P. also has a robust metaconid, even though it is only moderately worn. In gregorii (Fig. 5). There is no reason to rule out the possibility that they addition, robust metaconids can be seen on the premolars of less worn are indeed the upper dentitions of the same taxon as the blastomerycine specimens of B. gemmifer, B. “medius” and P. gregorii (Fig. 4). The lower dentitions at the same locality, since the size variation of these character “molars with larger and more compressed ectostylids” are highly lower jaw specimens overlaps with the uppers. They could also pertain variable even within the UCR collection from Massacre Lake, and a to a primitive palaeomerycid like Barbouromeryx as well. Whatever similar level of variability can be seen in the AMNH and F:AM collec- these teeth represent, there is no clear evidence that they represent a tion of B. gemmifer and P. gregorii. Finally, the assertion that the ramus separate species distinct from those that have been previously named. is “less curved” is impossible to evaluate on the Massacre Lake speci- In summary, there is no reason to recognize a new genus or species mens, since two are only short ramal fragments with only 2-3 teeth, and of blastomerycine in the Massacre Lake fauna. The lower jaw material is

FIGURE 4. Comparison of rami of blastomerycines in lateral view. Top, holotype of Blastomeryx “medius” (= B. gemmifer), AMNH 18955. Middle, UCMP 319167 from Massacre Lake. Bottom, holotype of Parablastomeryx gregorii, AMNH 31360. Scale bar in cm. 614

FIGURE 5. Comparison of upper teeth of blastomerycines. Top, UCMP 316925, from Massacre Lake. Bottom, AMNH 31360, holotype of Parablastomeryx gregorii. Scale bar in cm. largely undiagnostic, but based on the size, the unreduced premolars and synonym of Problastomeryx primus (Matthew, 1908). A new taxon Palaeomeryx folds, and the late Hemingfordian age of the sample, it is from the late Hemingfordian Massacre Lake fauna is also unsupportable, most likely referable to Problastomeryx primus. The upper jaw and most of the diagnostic material probably pertains to Problastomeryx tooth material is completely undiagnostic, but some specimens could be primus, although some of the upper teeth discussed by Morea (1981) upper teeth of the lower-tooth taxon “Nemomeryx vyaensis.” Other may actually pertain to a palaeomerycid like Barbouromeryx, and may upper teeth may not even belong to a musk deer at all, but instead to the not be a musk deer at all. late Hemingfordian palaeomerycid Barbouromeryx. Whatever this up- per tooth material is, it is not a distinct species. ACKNOWLEDGMENTS CONCLUSION I thank P.A. Holroyd for allowing me to study the UCMP and former UCR material and for permission to use the photos she took for Two taxa of extinct musk deer have been proposed from the early- my Fig. 1. I thank J. Flynn, Meng Jin, D. Diveley, and S.K. Bell for middle Miocene beds of northwestern Nevada. These taxa were based on access to specimens in their care. I thank E.B. Davis, M.O. Woodburne, fragmentary materials, and without adequate comparisons to other larger and P.A. Holroyd for helpful reviews of this paper. I thank P. Linse for samples of musk deer fossils from other collections and from regions her improvements on Figures 4 and 5. This research was supported by other than Nevada. Merriam’s (1911) “Blastomeryx mollis” from the grants from the Donors of the Petroleum Research Fund of the American early Barstovian Virgin Valley beds is invalid, and most likely a junior Chemical Society. 615 REFERENCES

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