AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 98:447-470 (1995 New Notharctine (Primates, Adapiformes) Skull From the Uintan (Middle Eocene) of San Diego County, California GREGG F. GUNNELL Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 481 09-1079 KEY WORDS Californian primates, Cranial morphology, Haplorhine-strepsirhine dichotomy ABSTRACT A new genus and species of notharctine primate, Hespero- lemur actius, is described from Uintan (middle Eocene) aged rocks of San Diego County, California. Hesperolemur differs from all previously described adapiforms in having the anterior third of the ectotympanic anulus fused to the internal lateral wall of the auditory bulla. In this feature Hesperolemur superficially resembles extant cheirogaleids. Hesperolemur also differs from previously known adapiforms in lacking bony canals that transmit the inter- nal carotid artery through the tympanic cavity. Hesperolemur, like the later occurring North American cercamoniine Mahgarita steuensi, appears to have lacked a stapedial artery. Evidence from newly discovered skulls ofNotharctus and Smilodectes, along with Hesperolemur, Mahgarita, and Adapis, indicates that the tympanic arterial circulatory pattern of these adapiforms is charac- terized by stapedial arteries that are smaller than promontory arteries, a feature shared with extant tarsiers and anthropoids and one of the character- istics often used to support the existence of a haplorhine-strepsirhine dichot- omy among extant primates. The existence of such a dichotomy among Eocene primates is not supported by any compelling evidence. Hesperolemur is the latest occurring notharctine primate known from North America and is the only notharctine represented among a relatively diverse primate fauna from southern California. The coastal lowlands of southern California presumably served as a refuge area for primates during the middle and later Eocene as climates deteriorated in the continental interior. Hesperolemur probably was an immigrant taxon that entered California from either the northern (Wyo- mingmtah) or southern (New Mexico) western interior during the middle Eocene o 1995 Wiley-Liss, Inc. Terrestrial fossil mammals from the more recent reviews of Eocene terrestrial Eocene Sespe Formation of southern Califor- mammals from southern California. nia were first described in a series of papers The San Diego Natural History Museum by Stock (1932,1933a-d, 1934a-d, 1935a-d, has been conducting fieldwork in the greater 1936a-c) and Wilson (1935). Shortly after- San Diego area for the past several years ward, mammals were described from Eocene (Walsh, 1991). During the course of this rocks in the greater San Diego area (Stock 1937, 1938; Wilson, 194Oa-c). Golz (1976), Golz and Lillegraven (1977), Lillegraven Received September 26, 1994; accepted June 21, 1995. (1976), Kelly (1990), Mason (1990), Kelly Address reprint requests to Gregg F. Gunnell, Museum ofpale- et al. (19911, and Walsh (1991) have provided ontology, University of Michigan, Ann Arbor, MI 48109-1079. 0 1995 WILEY-LISS, INC 448 G.F. GUNNELL fieldwork, a primate skull was discovered tube, while those that are not enclosed in from rocks of early Uintan age. The purpose bone are referred to as grooves. of this paper is to describe the new primate, to compare it with other notharctid and ada- Comparative samples pid primates from North America and Eu- Comparisons of the new California pri- rope, and to provide a summary of primate mate were made with a wide range of adapi- faunas from San Diego and Ventura counties. forms, either with original specimens or high Institutional abbreviations and designa- quality casts. Included in these comparisons tions used in the text are as follows: AMNH, were the following: European adapiforms: American Museum of Natural History, New Adapis parisiensis (UM 63301, 63302, Cam- York, Ny; BMNH, Natural History Museum, bridge M.538, Montauban-4); Agerinia ro- London, United Kingdom; CM, Carnegie selli (Unnumbered holotype and Cecilie Museum of Natural History, Pittsburgh, PA; 4241); Anchomomys gaillardi (UL L-46bis); Halle, Geiseltal Museum, Halle, Germany; Anchomomys stehlini (Basel En-1); Caeno- Louis, Private collection of P. Louis, Cormicy, pithecus lernuroides (NHB Eh 597-728); France; MNHN, Museum National d’His- Cantius eppsi (BMNH 13773, 15145, 15147, toire Naturelle, Paris, France; MPM, Mil- 29639); Cantius sauagei (Louis Collection waukee Public Museum, Milwaukee, WI; Mu 155-158, 160, MNHN Av 4846, 5907, NHB, Basel, Naturhistorisches Museum, 7702, Gr 98); Cercamonius brachyrhynchus Basel, Switzerland; PLV, Laboratorium voor (Basel Qv 619);Donrussellia gallica (MNHN Actuopaleontologie, Katholieke Universi- Av many unnumbered teeth); Donrussellia teit, Louvain, Belgium; SDSNH, San Diego louisi (MNHN Av 4731,4845,5664 and un- Society of Natural History, San Diego, CA; numbered teeth from Avenay and Grauves); TMM, Texas Memorial Museum, Austin, TX; Europolemur klatti (Halle-unnumbered UALP, University of Arizona, Laboratory of dentaryfrom Geiseltal and Halle 4238,4292, Paleontology, Tucson, AZ;UCMP, University 4304, 7325, 7396); Leptadapis magnus (Ba- of California, Museum of Paleontology, sel Qv 545,920, MNHN Qu 10943);Pericono- Berkeley, CA; UL, University of Lyon, Lyon, don (= Anchomomys?)pygmaeus (Basel En France; UM, University of Michigan, Mu- 367, Halle 7418, MNHN Bchs 494);Pronycti- seum of Paleontology, Ann Arbor, MI; USGS, cebus gaudryi (MNHN unnumbered holo- United States Geological Survey, Denver, type skull, Qu 11057); Protoadapis curuicus- CO; USNM, United States National Mu- pidens (AL 5182, 5719); Protoadapis filholi seum, Washington, DC; YPM, Yale Peabody (PLV 35); Protoadapis russelli (MNHN Av Museum, New Haven, CT. 4644,5759);Protoadapis sp. (MNHN Gr 150 and unnumbered teeth from Bouxwiller); MATERIALS AND METHODS North American adapiforms: Cantius abdi- tus (many specimens in UM collections, Measurements and nomenclature AMNH 4734); Cantius angulatus (AMNH All tooth measurements were taken with 55505, 55510, 55515); Cantius frugiuorus dial calipers under a binocular microscope (AMNH 16210, 55501, 86296, CM 37448); and recorded to the nearest tenth millimeter. Cantius mckennai (many specimens in UM Length (L) measurements record maximum collections); Cantius ralstoni (many speci- mesiodistal tooth dimensions, and width (W) mens in UM collections); Cantius tor- measurements record maximum buccolin- resi (many specimens in UM collections); gual breadth. Upper teeth are designated by Copelemur australotutus (USNM 22261, tooth position with superscripts and lower 411833); Copelemur praetutus (USNM 411- teeth by subscripts with I = incisor, 882, 411886, YPM 14698); Copelemur tutus C = canine, P = premolar, and M = molar. (AMNH 16205, 55462, UALP 11377-8); All measurements of arterial canal widths Mahgarita steuensi (TMM 41578-9);Nothar- were made using a binocular microscope ctus robinsoni (many specimens in UM col- with an optical micrometer at X 10. Arterial lections); Notharctus tenebrosus (many spec- pathways referred to as canals are those sur- imens in UM collections); Pelycodus jarrouii rounded by bone and manifest as a hollow (CM 37453, USGS 6549);Smilodectes graci- CALIFORNIAN NOTHARCTINE SKULL 449 lis (USNM 17994,21815,YPM 12904, many Etymology. Latin, hesperus, west, and le- specimens in UM collections); Smilodectes mur, ghost of the departed. mcgrewi (many specimens in UM collec- Discussion. Franzen (1987) has pro- tions). Comparisons were also made with the posed resurrecting Trouessart’s (1879) fam- plesiadapiform taxa Plesiadapis cookei (UM ily Notharctidae to include all adapiforms 87990) and Ignacius gruybullianus (UM except Adapis, Leptadapis, and Cryptad- 68006). apis, which remain in the family Adapidae. This arrangement accounts for the divergent characteristics of Adupis, Leptadapzs, and RESULTS Cryptadapis while recognizing the funda- mental similarities of other adapiforms. Systematic paleontology Most North American notharctids are placed Order Primates Linnaeus, 1758 in the subfamily Notharctinae, differen- Suborder Prosimii Illiger, 1811 tiated from European notharctids (Cerca- Infraorder Adapiformes Szalay and moniinae) mainly by the presence of proto- Delson, 1979 cone folds, metaconules, and mesostyles on Family Notharctidae Pouessart, 1879 upper molars. The lone North American ex- Subfamily Notharctinae Trouessart, ception is Muhgarita, which is placed within 1879 cercamoniines based on the presence of a cingular (“true”) hypocone and an absence of metaconules and mesostyles on upper Hesperolemur, gen. nov. molars. While Hesperolemur is generically distinct Notharctus (Lillegraven, 1980). from other North American notharctines, it ope species. Hesperolemur actius, sp. clearly shares common ancestry with the nov. taxa in this subfamily (Cantius, Pelycodus, Diagnosis. Hesperolernur differs from all Copelemur, Notharctus, and Smilodectes). other known adapiforms in lacking canals Like these taxa, Hesperolemur has upper enclosing the internal carotid arterial sys- molars with protocone folds and strong met- tem within the tympanic cavity and in hav- aconules, both characteristics that stand in ing the anterior third of the ectotympanic contrast to cercamoniines and adapids. Cra- and the anterior crus fused to the internal nially, Hesperolemur is similar to Notharctus surface of the lateral wall of the auditory in most features, differing substantially only bulla; it differs from adapids (Adupis and in the disposition of the tympanic