NAMERICAN MUSEUM Novttates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET NEW YORK, N.Y. 10024 U.S.A. NUMBER 2596 JUNE 4, 1976 BERYL E. TAYLOR AND S. DAVID WEBB Miocene Leptomerycidae (Artiodactyla, Ruminantia) and Their Relationships 4 AMERICAN MUSEUM Norntates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2596, pp. 1-22, figs. 1-7, tables 1-5 June 4, 1976 Miocene Leptomerycidae (Artiodactyla, Ruminantia) and Their Relationships BERYL E. TAYLOR1 AND S. DAVID WEBB2 ABSTRACT Leptomerycidae, previously thought to have Montana and possibly South Dakota is trans- survived only into the Arikareean, are here recog- ferred to the Leptomerycidae from incertae sedis nized from the medial Miocene (late Hemingford- in the Cervidae. ian into Valentinian) deposits of New Mexico, The relationships between these late Lepto- Texas, and Nebraska. These late-surviving Lepto- merycidae and contemporaneous Blastomery- merycidae belong to the species Pseudoparablas- cinae are shown to be remote despite several tomeryx scotti and P. francescita, previously parallel features in common. Separation of the assigned to the Blastomerycinae. Likewise, Pro- family Leptomerycidae from the family Hyper- nodens silberlingi from Arikareean deposits in tragulidae is advocated. INTRODUCTION The small Oligocene traguloid, Leptomeryx additional evidence to support the Leptomeryci- evansi, is probably the most abundant ungulate dae as.a distinct family and to recognize the sur- in the vast collections of fossil vertebrates from vival of two leptomerycid genera into much the White River Badlands of South Dakota (Clark younger stages of the Miocene. Neither of the and Guensberg, 1970, p. 412). Leptomeryx was genera here recognized as Leptomerycinae are thought to have become extinct by the end of new taxa. Rather, they are transferred from the Oligocene until Matthew (1926, p. 4) recog- other assignments within the Cervidae, in one nized the survival of one species into the early case from the more progressive immigrant sub- Miocene, in his "Lower Rosebud" beds and family Blastomerycinael (Frick, 1937), and in "Lower Harrison" deposits. Later Cook (1934, p. 155) described a new species of Leptomeryx 1 Blastomerycinae Frick, 1937, New Rank (=Blasto- merycini) [including Longirostromerycinae Frick, 1937 (L. agatensis) from the "Lower Harrison forma- and Parablastomerycinae Frick, 1937.] Frick's (1937) tion" of Nebraska. Such early Miocene occur- taxonomic arrangement recognized "Divisions" with rences have been confirmed more recently by names ending in "ini" as an intermediate rank between Macdonald's (1963, 1970) studies in the family and subfamily. With the exception of Pseudo. Wounded Knee parablastomeryx, we recognize all taxa included in area in South Dakota. Frick's revision of the "Blastomerycini" as belonging The purpose of the present paper is to provide to the Blastomerycinae. ' Frick Associate Curator, Department of Vertebrate Paleontology, the American Museum of Natural History. 2Curator, of Fossil Vertebrates, Florida State Museum; Professor of Zoology and Geology, University of Florida, Gainesville. Copyright © The American Museum of Natural History 1976 ISSN 0003-0082 / Price $1.60 2 AMERICAN MUSEUM NOVITATES NO. 2596 the other from an uncertain status within the we follow Gazin's (1955) cogent argument. As Cervidae (Koemer, 1940; Simpson, 1945). This he noted (pp. 12, 43, and 55) "striking dissimi- new evidence raises the question of how these larities in details of dentition" indicate separate later leptomerycines survived the period when origins for the Hypertragulidae and the Lepto- great herds of blastomerycines and dromo- merycidae, in which case "retaining these in the merycines spread so abundantly across North same family . is untenable." Moreover, we find America, but it does not provide a clear answer. that fundamental cranial and postcranial differ- Evidently their Oligocene level of abundance had ences also support Gazin's conclusion (see declined severely during the Miocene. Possibly Relationships, p. 19). Subsequent transfer of they survived as relicts in forested habitats. various late Eocene genera from Gazin's Lepto- merycidae to become early members of the ACKNOWLEDGMENTS Protoceratidae, as advocated by Wilson (1974, p. 30) and partly anticipated by Romer (1966, Our thanks to Drs. Malcolm C. McKenna and p. 283), does not affect this, for such a reduction Richard H. Tedford for reading the manuscript in generic content of the Leptomerycidae does and for giving helpful suggestions. We are grate- not alter its phylogenetic relationship to the ful to Dr. John H. Ostrom of the Peabody Hypertragulidae. It is ironic that Scott's (1899, Museum, Yale University for lending us the type p. 15) original usage of "Leptomerycidae" in- of Pronodens silberlingi. The illustrations were cluded the hypertragulids at subfamily level. prepared by Mr. Raymond J. Gooris, and the Another curiosity about the name "Leptomery- manuscript was typed by Miss Janice Ebenstein. cidae" is Scott's (1945, p. 229) attribution of the name to Osbom. In the present paper we deal ABBREVIATIONS only with the subfamily Leptomerycinae. The Institutional: possibility that the subfamily Archaeomerycinae AMNH, Department of Vertebrate Paleontology, should be included in the Leptomerycidae will the American Museum of Natural History be considered in a separate contribution. F:AM, Frick American Mammals, Department of Vertebrate Paleontology, the American Muse- um of Natural History SUBFAMILY LEPTOMERYCINAE ZITTEL, 1893 FBAM, Frick Barbour, American Mammals, De- partment of Vertebrate Paleontology, the PRONODENS KOERNER, 1940 American Museum of Natural History YPM, Peabody Museum, Yale University Figure 1C-E Pronodens Koerner, 1940, p. 842, pl. 2, figs. 3. Used in Figures: Leptomeryx obliquidens Lull, 1922, p. 115: PS, postsymphysis specimen referred by Matthew, 1926, p. 4. Used in Measurements and Statistics: Type Species. Pronodens silberlingi Koemer, N, sample size 1940. OR, observed range Included Species. Type species only. X, mean Type. YPM 13952, left incomplete mandibu- S, standard deviation lar ramus with I1-I2, I3-C (alveoli), and P2-M3 V, coefficient of variation (broken) recorded from the Fort Logan Forma- tion (Arikareean) Section 4, R. 10 N., T. 5 E., SYSTEMATICS Meagher County, Montana. ORDER ARTIODACTYLA OWEN, 1848 Known Distribution. Arikareean of Montana and South Dakota. SUBORDER RUMINANTIA SCOPOLI, 1777 Tentatively Referred. AMNH 13824, right INFRAORDER TRAGULINA FLOWER, 1883 partial maxilla with P2-M2, listed by Matthew, 1926, from "Lower Rosebud beds near No Flesh FAMILY LEPTOMERYCIDAE ZITTEL, 1893 Creek, Pine Ridge Indian Reservation, S. Da- In retaining the Leptomerycidae as a family kota." 1976 TAYLOR AND WEBB: LEPTOMER YCIDAE 3 Revised Diagnosis. Differs from Leptomeryx ening of the anterior part of the mandibular in loss of P1 ; shorter diastema between C and P2; ramus. These include the abbreviation of the post posterior extension of symphysis to a point canine-P2 diastema and the posterior shifting of below anterior root of P2; relatively smaller pre- the symphysis and mental foramen to a point be- molars; a reduction in size of paraconid on pre- low the anterior part of P2. The loss of P1 may molars; and more posterior position of mental also be associated with the foreshortening of the foramen below anterior border of P2. diastema. Furthermore, we have observed that Differs from Pseudoparablastomeryx in its P2 -P4 are less elongate and relatively smaller than larger size; diastema between C and P2 less in Leptomeryx with a proportionally shorter elongate, more robust and dorsoventrally deeper; paraconid accounting, at least, for a part of this mental foramen situated less anteriorly and be- reduction in size. A prominent and labially pro- neath anterior border of P2; and symphysis ex- jecting hypoconid is present on P3 and P4 of tended more posteriorly with posterior border both the type of Pronodens silberlingi and the beneath anterior root of P2 . above Leptomeryx (cf. L. mammifer) mandibu- Discussion. Koerner (1940) initially described lar ramus (F:AM 95493). Although the wom Pronodens and placed it in the Cervidae. The molars of the type of P. silberlingi closely re- type of P. silberlingi is an incomplete mandibular semble those of Leptomeryx, extreme wear ramus and the only specimen known to him. In precludes any detailed comparison of morpho- the generic diagnosis Koerner listed the following logical features. characters: strongly procumbent, tusklike inci- Matthew (1926, p. 4) referred an upper jaw sors, the unusually short diastema between the (AMNH 13824) from the Lower Rosebud beds canine and P2, and the posterior position of the to Leptomeryx obliquidens Lull and observed mental foramen along with the posterior exten- that the jaw is slightly smaller than Lull's type. sion of the posterior border of the mandibular Regarding AMNH 13824 Frick (1937, p. 624) symphysis, both to a point below the anterior stated, "there may be considerable doubt as to part of P2. Koerner (1940, p. 844) stated, "In the allocation of the partial cheek-tooth series spite of the unusual character of the incisors, from the middle Tertiary deposits between Pronodens is undoubtedly one of the pecorans. the Leptomerycini and the Blastomerycini." The general features of the grinding teeth and the Frick noted that the lingual midroot and proto- absence of P,,