Small Oligocene Amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora) Robert M

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2001 Small Oligocene Amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora) Robert M. Hunt Jr. University of Nebraska-Lincoln, [email protected]

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Hunt, Robert M. Jr., "Small Oligocene Amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora)" (2001). Papers in the Earth and Atmospheric Sciences. 548. https://digitalcommons.unl.edu/geosciencefacpub/548

This Article is brought to you for free and open access by the Earth and Atmospheric Sciences, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in the Earth and Atmospheric Sciences by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. NoVltatesAME RICAN MUSEUM P U BLISH ED BY THE AMERICAN M USEU M OF NATURAL HI S TORY CENTRAL PA RK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 333 1. 20 pp .• II fi gures. 2 tables April 26. 2001

Small Oligocene Amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora)

ROBERT M . HUNT. JR.'

ABSTRACf North AlIl l!rican amphicyonid camivorans are important members of the mid-Cenozoic ter restrial carnivore community during the latc Eocene to latc Miocene (Duchcsncan to C laren donian). Species range in size from < 5 kg to > 200 kg. Among the smallest and rarest amphicyonids are Oligocene species of Paradaphoelllls Wortman and Matthew, found al a few localities in the Great Plains and the Pacific Northwest. Puradaphoen liS is known from only 10 individuals placed in 3 species (P. mininlll.f; P. tooheyi. n. sp.: P. clIspigerus). representing a single lincage ranging from the Orellan to Arikareean. The existence of three skulls, one with associated mandibles, allows the identification of d iagnostic basicranial and dental traits that place the genus in the Amphicyonidae. Basicranial anatomy, including a rudimenlary ectotympanic auditory bulla. distinguishes the genus from more abundant small contemporary canids. such as II ~Jperoc)'on . The species of ParadaphoenuJ most likely adopted ecological roles similar to the smaller li vi ng foxes.

INTRODUCTION O ligocene were relatively small « 20 kg) carnivores, but by the early to mid-Miocene Amphicyonid carnivores are a geographi a number of lineages exceeded 100 kg and cally widespread family of mid-Cenozoic had become the dominant predators of the arctoid carnivorans ranging in size from < 5 Ho larctic continents (Hunt. 1996. 1998). kg 10 > 200 kg. Although known from Eur The earlie st North American amphicyon asia. North America, and Africa. most fossil s ids are Duchesnean (late Eocene) fossils re have co me from western Europe and the ferable to D aphoellllS lambei. a small (2- 4 Unjted States. The oldest North American kg) carnivore occurring from southern Can amphicyonids from the late Eocene and early ada to Texas (Hunt. 1996). DapllOenus rang-

, Research Associa,e. Di vision of Paleonlo logy. American Museum of Natural History; Professor. Geological Sci ences; and Curator. Vert ebrate Pal CQntology. Un ivcrsi.y of Nebr.tska, Lincoln. NE 68588·0549.

Copyri ght C Amcrican Museum of Natu r.tl History 2001 ISSN 0003-0082 I Pri ce $2.70 2 AMERICAN MUSEUM NOVITATES NO. 3331 es from the Duchesnean to the early Arika- siomorphic molars that resemble those of Eu- reean and is the most common North Amer- ropean Cynodictis from Quercy in France. ican Paleogene amphicyonid. The Duches- The previously undescribed Whitneyan and nean D. lambei is the smallest species of this early Arikareean Paradaphoenus fossils, rep- lineage and is a likely ancestor to all later resented by only two mandibles and an un- Daphoenus. After the appearance of Da- associated maxilla from Nebraska and South phoenus in the early Duchesnean, Daphoen- Dakota, warrant the naming of a new species, ictis and Brachyrhynchocyon ®rst occur in P. tooheyi. the late Duchesnean and early Chadronian, A functional interpretation of the teeth, respectively, coexisting with Daphoenus skull, and postcranial skeleton suggests that throughout the Chadronian: all of these gen- Paradaphoenus was a small terrestrial om- era are small, fox-sized carnivores (ϳ4±10 nivore lacking cursorial specializations, and kg). Daphoenictis and Brachyrhynchocyon probably able to climb when necessary. become extinct at the end of the Chadronian, These characteristics would be compatible but Daphoenus persists into the Orellan (ear- with a wooded habitat, whether savanna or ly Oligocene), and progressively increases in riverine gallery forest. Its basicranial anato- size during the Whitneyan. By the early Ari- my establishes it as a member of the Am- kareean (late Oligocene), Daphoenus ap- phicyonidae (Hunt, 1998). proaches the size (ϳ20±30 kg) of a small wolf (Hunt, 1996). ABBREVIATIONS Much less familiar to paleontologists is another lineage of very small amphicyonids, Anatomical Paradaphoenus Wortman and Matthew, A alisphenoid 1899, entirely restricted to North America. ac alisphenoid canal The genus ®rst appears in Orellan sediments BO basioccipital of the Great Plains, continues through the BS basisphenoid Whitneyan, and terminates in the early or ca pit for anterior crus of ectotympanic mid-Arikareean. Members of this lineage in- E caudal entotympanic crease only slightly in size over ϳ6 million F facet on petrosal promontorium for ec- years, never exceeding 3±4 kg, and are the totympanic smallest New World amphicyonids. Their re- gf postglenoid foramen mains were often placed in disparate taxa or h hypoglossal (condyloid) foramen L middle lacerate foramen went unrecognized in collections. m mastoid The North American hypodigm of Para- me mastoid-exoccipital suture daphoenus includes the remains of just 10 P petrosal promontorium individuals (®g. 1), allocated to 3 species, P. plf posterior lacerate foramen minimus (Hough, 1948a) and P. tooheyi,n. pp paroccipital process sp., from White River and lower Arikaree ps basioccipital embayment for inferior sediments of Nebraska and South Dakota, petrosal venous sinus and a terminal species, P. cuspigerus (Cope, SQ squamosal 1878), from the John Day beds of Oregon. T ectotympanic Fortunately, the genus is represented by three x partial M3 alveolus skulls with well-preserved teeth and basi- Institutional crania. Paradaphoenus cuspigerus is based on two skulls from the John Day beds, one AMNH American Museum of Natural History, of which (the holotype, ®g. 2) includes both New York, NY mandibles of the same individual, demon- LACM Los Angeles County Museum of Nat- strating a critical association between lower ural History, Los Angeles, CA UNSM University of Nebraska State Museum, and upper teeth. The Orellan species, Para- Lincoln, NE daphoenus minimus, is oldest and is repre- NMB Naturhistorisches Museum, Basel, sented by a skull, several isolated mandibles, Switzerland and the only known postcranial material at- SDSM South Dakota School of Mines and tributable to the lineage; it has dentally ple- Technology, Rapid City, SD 2001 HUNT: OLIGOCENE AMPHICYONIDS 3

Fig. 1. Geographic distribution of Paradaphoenus in North America: all fossils are from Oligocene sediments of the central Great Plains (White River and Arikaree Groups, P. minimus, P. tooheyi) and Oregon (John Day Formation, P. cuspigerus).

SYSTEMATICS and early Arikareean of western Nebraska; ORDER CARNIVORA BOWDICH, 1821 Orellan and early Arikareean of southwestern South Dakota; early or mid-Arikareean of DIVISION ARCTOIDEA FLOWER, 1869 central Oregon. FAMILY AMPHICYONIDAE TROUESSART, 1885 DIAGNOSIS: Smallest (Ͻ 3±4 kg) North American amphicyonid carnivorans with m1 Paradaphoenus Wortman and Matthew, lengths of 8.3±9.4 mm; rudimentary auditory 1899 bulla formed by a slightly in¯ated ossi®ed TYPE SPECIES: Paradaphoenus cuspigerus ectotympanic that does not fully enclose the (Cope, 1878). middle ear; dental formula 3-1-4-3/3-1-4-3; INCLUDED SPECIES: Paradaphoenus cuspi- P4 length short relative to combined lengths gerus, Paradaphoenus minimus (Hough, of M1-2 (P4L/M1-2L: Orellan, 80.8%; early 1948a), Paradaphoenus tooheyi, new spe- Arikareean, Great Plains, 77.6%; early or cies. mid-Arikareean, Oregon, 67.7±73.2%); P4 KNOWN DISTRIBUTION: Orellan, Whitneyan, with abbreviated protocone relative to Da- 4 AMERICAN MUSEUM NOVITATES NO. 3331

Fig. 2. (A) Cranium and mandibles of the genoholotype of Paradaphoenus (P. cuspigerus, AMNH 6852) from the John Day Formation, Oregon (in lateral view); (B) stereophotographs of the same individual, initially ®gured by Cope (1884, P1. 68, ®gs. 1±4) as Amphicyon cuspigerus. Scale bar in this and all subsequent ®gures is 1 cm in length unless otherwise noted.

phoenus, Hesperocyon, and Cynodictis;M1 DISCUSSION: The fossils of Paradaphoenus with well-developed meta- and paraconules fall into four samples of decreasing geologic as in Cynodictis; M2 prominent and the cen- age: (1) an Orellan sample, comprising the tral member of an upper molar row that grad- holotype cranium of ``Daphoenus'' minimus ually diminishes in size from M1-3; m1 with Hough 1948a (®g. 3, AMNH 39099) from basined talonid, m1 paraconid blade not an- near Scenic, South Dakota, and four isolated teriorly extended (it is extended in Hesper- mandibles from western Nebraska (®g. 4, ocyon); prominent rectangular m2 with ba- UNSM 25030, 25305, 26139; UNSM 25148 sined talonid and anterolabial swelling of the not illustrated), all from White River sedi- cingulum (m1-2 talonids are markedly en- ments; (2) an isolated Whitneyan mandible larged with prominent basins in Whitneyan from White River sediments of western Ne- and Arikareean species, less so in Orellan); braska (®g. 4, UNSM 26130, P. tooheyi,n. postorbital/preorbital length ratio ϳ2:1 (table sp.), with its molar dentition evolved beyond 1). Lower molars become wider in younger that of the Orellan specimens, but not to the species; upper molars are correspondingly degree observed in the early Arikareean fos- enlarged (table 2). sils; (3) a mandible from lower Arikaree sed- 2001 HUNT: OLIGOCENE AMPHICYONIDS 5

Fig. 3. Stereophotographs of the holotype cranium (in ventral view) of Paradaphoenus minimus (AMNH 39099), Orellan, White River Group, South Dakota. For abbreviations in this and subsequent ®gures, see p. 2. iments, Wagner Quarry, Dawes Co., Nebras- the basined molar talonids), a character ka (UNSM 6002-92, holotype of P. tooheyi, found in the younger species of the genus. n. sp.), and a maxilla of the same species This broadening of the molars is ®rst ob- from the Sharps Formation of South Dakota served in the only Whitneyan specimen of (LACM 21649, P. tooheyi, n. sp.), both of Paradaphoenus, a mandible with p2-m1 early Arikareean age (®g. 5); (4) the cranium (UNSM 26130), and becomes most pro- and associated mandibles (®g. 2, AMNH nounced in the lower molars of the Arika- 6852, genoholotype) of Paradaphoenus cus- reean mandibles (®g. 6). The Orellan fossils pigerus (Cope, 1878), and a referred cranium include the smallest individuals of the Par- of the same species (AMNH 6853, holotype adaphoenus lineage, based on dental mea- of ``Amphicyon'' entoptychi Cope, 1879) surements and the size of the only known from the John Day beds, central Oregon, Orellan cranium (AMNH 39099, table 1, both fossils unfortunately lacking exact basilar length ϳ8.8 cm). The plesiomorphic stratigraphic data, but probably of late early features of the molars warrant retention of to mid-Arikareean age. Geographic and Hough's (1948a) species minimus for the Or- stratigraphic information for these fossils is ellan hypodigm. presented in appendix 1. The early Arikareean fossils from South The Orellan cranium and mandibles are Dakota and Nebraska include a maxilla with the geologically oldest remains of the genus M1-2 (alveoli or broken roots of P3-4, M3) and retain the most plesiomorphic dentition. from the Sharps Formation of southwestern These mandibles show no transverse broad- South Dakota, and an isolated mandible with ening of m1-2 (in particular, no widening of p4-m2 (alveoli of p1-3, canine root) from a 6 AMERICAN MUSEUM NOVITATES NO. 3331

Fig. 4. Mandibles of Paradaphoenus from the White River Group, western Nebraska: (A) Labial viewÐtop, P. tooheyi, Whitneyan, UNSM 26130; middle, P. minimus, Orellan, UNSM 25305; bottom left and right, P. minimus, Orellan, UNSM 25030 and 26139. (B) Lingual viewÐtop, P. tooheyi, UNSM 26130; middle, P. minimus, UNSM 25305; bottom left and right, P. minimus, UNSM 25030 and 26139 (stereophotographs). lower Arikaree channel ®ll (Wagner Quarry) 1981 (reported by J. R. Macdonald [1970] to in northwestern Nebraska (®g. 5). The be equivalent to SDSM Loc. V5359, near the Sharps maxilla was discovered in the collec- middle of the Sharps Formation). The Wag- tion of the Los Angeles County Museum, ner Quarry mandible was found in 1992 dur- and is from LACM Wounded Knee Loc. ing a UNSM excavation of a basal Arikaree 2001 HUNT: OLIGOCENE AMPHICYONIDS 7

TABLE 1 Preorbital, Postorbital, and Basilar Lengths of Paradaphoenus Crania (in mm)a

Taxon Museum no. Preorbital Postorbital Ratio Basilar Paradaphoenus cuspigerusb AMNH 6852 36.4 70.2 1.93 94.8 Paradaphoenus cuspigerus AMNH 6853 ϳ38 68.3 1.80 ϳ100 Paradaphoenus minimusb AMNH 39099 ϳ30 66.2 2.20 ϳ88 a Preorbital length is measured from the tip of the premaxilla to the anterior border of the orbit; postorbital length is measured from the anterior border of the orbit to the occipital condyle. b Holotype.

¯uvial channel ®ll cut into sediments of the or can be directly correlated with, the type White River Group near Chadron, Nebraska; areas of the Orellan, Whitneyan, and Arika- associated mammals included anthracothere, reean land mammal ages. The recent discov- entelodont, rhinoceros, nimravid, and several ery and identi®cation of the Whitneyan and rodents. early Arikareean fossils from Nebraska and Whitneyan and early Arikareean Parada- South Dakota allowed a more accurate age phoenus fossils from Nebraska and South estimate for the John Day specimens, which Dakota, although differing in age, are mor- previously were dif®cult to date. These new phologically similar, and are placed in a new fossils also document successive evolution- species, Paradaphoenus tooheyi (appendix ary stages in the Paradaphoenus dentition 2), intermediate in the form of m1-2 between during the Orellan to Arikareean interval that P. minimus and P. cuspigerus. The new spe- support the placement of the three known cies is named for Dr. Loren Toohey of Mid- species in a single lineage. land, Texas, who has contributed for over 60 This scenario is based on an observed pro- years to UNSM ®eld excavations in Nebras- gressive alteration in the form of m1-m2. For ka, and participated in the 1992 Wagner example, the recently discovered Wagner Quarry excavation that discovered the holo- Quarry mandible of P. tooheyi has an m2 type. morphology likely to have been derived from Fortunately, the Great Plains fossils of the plesiomorphic m2 of the Orellan P. min- Paradaphoenus can be placed in established imus. In the Wagner Quarry m2, the trigonid stratigraphic sequences that either are within, is reduced and crowded to the front of the

Fig. 5. Stereophotographs of the maxilla (LACM 21649, Sharps Formation, South Dakota) and holotype mandible (UNSM 6002-92, lower Arikaree Group, Nebraska) of early Arikareean P. tooheyi, n. sp., known only from the central Great Plains. Note alveoli for well-developed M3 in maxilla. 8 AMERICAN MUSEUM NOVITATES NO. 3331

is apparently somewhat younger, possibly of late early to mid-Arikareean age, based on the observation that the amount of change in the molar teeth between P. tooheyi from Wagner Quarry and P. cuspigerus is rather modest. Lower Arikaree sediments at Wag- ner Quarry are probably time equivalent to lower Arikaree ¯uvial rocks of the Gering Formation at Wildcat Ridge in the southern Nebraska panhandle, dated at ϳ28.1±28.3 Ma (Tedford et al., 1996; MacFadden and Hunt, 1998). John Day P. cuspigerus would necessarily postdate this interval, but the amount of time involved is uncertain. Gray tuffaceous siltstone adhering to the skulls could have been derived from a number of tuffaceous units within the upper John Day Formation, but the exact horizon is indeter- minate. A speculative upper age limit for the Paradaphoenus lineage, based on the sum of present evidence, is estimated at ϳ25±23 Ma. Fig. 6. Stereophotographs of the lower dentition of holotypes of Paradaphoenus tooheyi (left, DENTITION UNSM 6002-92) and P. cuspigerus (right, AMNH 6852) in occlusal view. Note wider molars and Incisors: No specimens of the Orellan or more anteriorly placed m2 trigonid in AMNH Whitneyan species of Paradaphoenus pre- 6852. serve either upper or lower incisors. The anterior rostrum of the only known Orellan skull (AMNH 39099) is missing, and none tooth, and the talonid is widened and more of the mandibles retains the anterior part with prominently basined, relative to the P. min- incisor alveoli. imus m2, in which the unreduced trigonid oc- The early Arikareean Wagner Quarry cupies the anterior half of m2 and the talonid specimen preserves the anterior part of the is not expanded. In the holotype mandible of left mandible: although no incisors remain, the John Day P. cuspigerus, the widening of there is a large i3 alveolus, but the part of the molars observed in the Wagner Quarry the dentary with the i1-2 alveoli was lost. mandible is even more pronounced (®g. 6): In the P. cuspigerus holotype mandible, a the m2 trigonid of the John Day species re- partial, poorly de®ned i3 alveolus lies inter- mains crowded to the anterior end of the nal to the canine root. However, the upper tooth as in the Wagner Quarry mandible, but incisor row in the premaxillae preserves an the m2 talonid is even more expanded. The intact acuminate I3, slightly recurved and lower carnassial also is broadened, particu- without accessory cusps. I1-2 progressively larly the basined talonid. The upper molars decrease in size internal to I3, but are broken of the two John Day crania (AMNH 6852, off at their roots. 6853) also demonstrate this trend (®g. 7), for Canines: No canines are preserved in the they are enlarged and broadened relative to Orellan or Whitneyan fossils. The Wagner the upper molars in the maxilla from the Quarry Arikareean mandible retains a robust, Sharps Formation of South Dakota (®g. 5). slightly laterally compressed canine root (5.3 The John Day crania, then, are unlikely to ϫ 3.2 mm). The mandible of the P. cuspi- be of earliest Arikareean age, because their gerus holotype also contains a robust, some- molars are more derived than those in the what laterally compressed canine root (5.5 ϫ Wagner Quarry mandible and Sharps For- 2.8 mm), but the crown was lost. The deli- mation maxilla. The John Day P. cuspigerus cate upper canine of the holotype (AMNH 2001 HUNT: OLIGOCENE AMPHICYONIDS 9

6852) is laterally compressed (4.5 ϫ 3.3 whereas diastemata between the other pre- mm), and although incomplete, shows the molars are negligible. There is a progressive posterior and anterointernal longitudinal decrease in size from P3 to P1; this is also enamel ridges typical of amphicyonids. seen in the Arikareean Paradaphoenus skulls Premolars: Only one Orellan mandible from the John Day beds (®gs. 7B, 7C). (UNSM 25305, ®g. 4) retains any part of a P4 in all Paradaphoenus skulls (AMNH premolar; all other mandibles are broken an- 39099, 6852, 6853) is a short, robust carnas- terior to m1. UNSM 25305 retains the base sial, surrounded by a pronounced cingulum. of p4 (for dental measurements, see table 2), P4 has a prominent but abbreviate protocone which suggests that the premolars in the Or- that in occlusal view is nearly con¯uent with ellan Paradaphoenus minimus were similar the medial face of the carnassial; the proto- to the laterally compressed premolars in the cone is not strongly extended toward the younger species of the genus. The only man- midline as in, for example, Hesperocyon and dible of Whitneyan age (P. tooheyi, UNSM Daphoenus. 26130, ®g. 4) retains p2-4 and a single-root- P2-4 in the John Day skulls (AMNH 6852, ed p1 alveolus. Here p2-4 are elongate, lat- 6853, ®g. 7) are very similar to these teeth erally compressed teeth separated by very in the Orellan skull (AMNH 39099). AMNH short diastemata; each premolar has a rela- 6852, the P. cuspigerus holotype, preserves tively low central cusp, an extended posterior P1-4, the only complete upper premolar row heel with a small posterior cingulum cusp, known in the genus. P1 is a small, laterally and a slightly extended anterior cingulum; compressed tooth with an anteriorly placed there is a small anterior cingulum cusp on main cusp. P4 retains the diagnostic shape p2-4. seen in all other specimens; however, the en- Although the Wagner Quarry mandible circling cingulum is even more pronounced. (UNSM 6002-92, ®g. 5) retains only p4, this Molars: Upper molars are present in the tooth is somewhat taller and less elongate Orellan and Arikareean skulls of Parada- relative to the Whitneyan p4 of UNSM phoenus (®g. 7), and also in the Arikareean 26130. Also, the dimensions of the p2-3 al- maxilla from the Sharps Formation (®g. 5). veoli in the Wagner Quarry mandible indi- In these specimens the molars are largely un- cate that these premolars were not as elon- worn, with a well-de®ned cusp pattern; gate as in the Whitneyan specimen. In fact, AMNH 6853 is an exception, with somewhat the Wagner Quarry mandible and the holo- worn molars. Both John Day skulls and the type mandible of the John Day P. cuspigerus Sharps Formation maxilla have three upper (AMNH 6852, ®gs. 2, 6) share shorter premolars. M3 is actually present in AMNH molars without evident diastemata, relative 6853, and this tooth is represented by alveoli to the Whitneyan mandible. The John Day P. in the Sharps maxilla and in AMNH 6852. cuspigerus mandible preserves p2-4: each In the Orellan AMNH 39099 an indentation premolar has a principal cusp placed slightly in the posterior border of the left maxilla forward of center descending to a posterior suggests M3 was initially present (®g. 3, x). heel that increases in size from p2 to p4; a Thus, Paradaphoenus retained three upper prominent, somewhat laterally placed poste- molars throughout its known range, and rior accessory cusp occurs on p4 but is ab- Wortman and Matthew (1899:129) included sent on p2-3. A ®ne enamel ridge descends the presence of M3 in their de®nition of the the anterior face of each premolar: it is de- genus. ¯ected to the anterointernal margin of p2, In all the skulls and in the maxilla, the less so on p3, and continues directly forward molars diminish in size from M1 to M3. to the anterior border of p4. However, there is a proportional size increase Only P3-P4 are adequately preserved in in M2 relative to M1 between the Orellan the Orellan skull (AMNH 39099, ®g. 7A). In and Arikareean species. This is particularly lateral view, P3 is triangular, with a small evident in the John Day species, P. cuspi- heel, but lacking a posterior accessory or cin- gerus, in which the M2 is conspicuously en- gulum cusp. P2 is separated from P1 by a larged (®g. 7). diastema 4.3 mm in length in AMNH 39099, The distinguishing features of M1-2 are: 10 AMERICAN MUSEUM NOVITATES NO. 3331

Fig. 7. Stereophotographs of the upper dentition (palatal view) of (A) Paradaphoenus minimus (AMNH 39099, holotype) from the Brule Formation, South Dakota, and (B, C) Paradaphoenus cuspi- 2001 HUNT: OLIGOCENE AMPHICYONIDS 11

Fig. 8. Stereophotographs of the cranium (in ventral view) of the amphicyonid Cynodictis cf. lon- girostris, Quercy district, France (NMB Q.V. 412); M3 is absent in this individual. The basicranium preserves the anterior half of the ectotympanic bulla and the deep embayment in the lateral margin of the basioccipital, presumably for an expanded inferior petrosal venous sinus.

(a) the presence of prominent para- and The M1 of Paradaphoenus is very similar metaconules, particularly on M1Ðin addi- in cusp pattern to the M1 of Cynodictis (®g. tion, there is often an accessory cusp on the 8), yet M2 in the latter is much more reduced postprotocrista lingual to the metaconule and M3 is often absent, although Teilhard (also present in Cynodictis); (b) a parastylar (1915) reported the presence of M3 in some cusp with a narrow stylar region and cingu- individuals of European Cynodictis. lum on M1, and a more reduced stylar region There are three lower molars in Parada- on M2, evidenced by the strong labial place- phoenus. Only an Orellan mandible (UNSM ment of the M2 paracone and metacone (the 25030, ®g. 4) and the holotype mandible of stylar region and parastyle are less reduced P. cuspigerus retain m3. These two speci- in Cynodictis); (c) M1-2 transversely extend- mens represent the oldest and youngest spe- ed by development of a thick lingual cingu- cies of the Paradaphoenus lineage, and the lum and shelf; and (d) the lingual margin of transformation of m3 over this interval is re- M2 does not extend as far medially as does lated to the broadening of m2-3 that char- the lingual margin of M1. acterizes the genus. In the Orellan species,

← gerus from the John Day Formation, Oregon: (B) AMNH 6853, referred; (C) AMNH 6852, holotype. Note the enlarged M2 in both skulls of P. cuspigerus and the presence of M3 in AMNH 6853. A partial M3 alveolus exists in AMNH 39099 (see ®g. 3). 12 AMERICAN MUSEUM NOVITATES NO. 3331 Ð Ð Ð Ð Ð 24.1 22.8 27.6 25.2 25.6 2.4 3.2 5.5) 5.0 c ϫ ϫ ϫ ϫ Ð Ð Ð Ð alv 3.1 4.2 (3.4 (2.7) 3.6 3.8 3.9 3.7 4.3 4.4 6.87.5 8.1 alv 8.6 ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ 5.2 5.1 5.2 5.7 5.3 5.5 5.8 5.7 4.5 Paradaphoenus 4.3 4.2 4.2 4.2 4.44.5 5.2 Ð9.7 Ð9.3 4.1 10.3 10.5 24.6 ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ 8.3 9.4 9.3 7.4 7.5 8.7 8.7 6.2 (8.4) b 3.2 2.5) 3.2 3.6 5.64.0) 6.8 5.6 5.7 (3) 9.0 ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ ϫ Ð Ð 7.4 9.3 8.8 6.7 6.6 (6.3 (8.3 TABLE 2 2.62.8) 7.3 2.7 2.92.5) 8.8 3.0 3.2 of the Dentition of North American a ϫ ϫ ϫ ϫ ϫ ϫ ϫ Ð Ð Ð Ð 6.3 5.8 6.2 (6.7 (5.6 W in mm) 2) ؋ 2.1 6.8 2.1 2.2 6.2 2.1 2.1 ϫ ϫ ϫ ϫ ϫ ϫ Ð Ð Ð Ð Ð (5.3 4.7 5.1 4.5 1.3) 5.6 1.5) 1.5) 1.8 ϫ ϫ ϫ ϫ Ð Ð Ð Ð Ð Ð P1 P2 P3 P4 M1 M2 M3 P1-4L Measurements (L 3.3 (3.3 (2.7 width. ϫ length ϭ alveolus(i) present. estimated measurement. W ϭ ϭ ϫ Museum no. p1 p2 p3 p4 m1 m2 m3 p1-4L L () alv UNSM 26130 (2 UNSM 6002-92 AMNH 6852 UNSM 25305 UNSM 25030 UNSM 26139 UNSM 25148 AMNH 39099 Ða b c 4.6 LACM 21649 AMNH 6852 AMNH 6853 Whitneyan Arikareean Orellan Orellan Arikareean 2001 HUNT: OLIGOCENE AMPHICYONIDS 13 the m3 trigonid with normally proportioned ridges. In P. cuspigerus, m2-3 have become cusps occupies the anterior half of the tooth; small crushing platforms accompanying the the trigonid is wider than the smaller talonid. expanded M2-3 in the maxilla. However, in AMNH 6852 the m3 trigonid is The characteristic form of the Parada- displaced to the anterior end, the entire tooth phoenus m1 is altered only by a progressive is broadened, and the talonid is deeply ba- broadening of the tooth over time. Through- sined and wider than the trigonid. out the range of the genus, the form of the The m2 re¯ects the same transformation as trigonid and the placement of its cusps m3, but this is even more pronounced. The changes very little. The paraconid is not ad- transition from a normally proportioned m2 vanced anteriorly as it is in canids, hence the to the widened m2 with trigonid crowded to trigonid cusps remain in the same relative the front is demonstrated by three mandibles: positional relationship. However, in the UNSM 25305 (P. minimus, ®g. 4), UNSM Whitneyan mandible (UNSM 26130) the m1 6002-92 (P. tooheyi, ®g. 5), and AMNH talonid is broadened and develops a promi- 6852 (P. cuspigerus, ®g. 6). In the Orellan nent basin, and the trigonid is slightly dimin- P. minimus (UNSM 25305), the m2 trigonid ished in height relative to the Orellan sample. occupies slightly more than 50% of the oc- In the early Arikareean, the m1 talonid of the clusal surface; the three trigonid cusps are Wagner Quarry mandible (UNSM 6002-92) placed at the corners of an equilateral trian- is slightly widened relative to the Whitneyan gle, and the trigonid is noticeably wider than m1, but otherwise m1 proportions are simi- the talonid. The narrow basin of the talonid lar. In the John Day m1 (AMNH 6852) the is bordered by hypoconid and entoconid entire carnassial is wider, but here the talonid ridges. The anterointernal corner of m2 pro- is conspicuously broadened and the talonid trudes as a low shoulder, and the three tri- basin attains its maximum development. gonid cusps diminish in size from the large Thus, the trend observed in the dentitions protoconid to a smaller metaconid to a small of Paradaphoenus from the Orellan into the yet distinct paraconid. Arikareean involved a slight increase in size, The proportions of m2 in the early Ari- accompanied by progressive broadening of kareean Wagner Quarry mandible (P. tooh- the molars, particularly evident in the altered eyi, UNSM 6002-92) are much different form of M2/m2. In addition, the short, robust from the Orellan m2. The trigonid occupies carnassials retain a distinctive form in which only ϳ40% of the occlusal surface and is con®ned to the anterior part of m2. The pro- the abbreviated protocone of P4 is not me- toconid and metaconid are accentuated, dially extended, and the paraconid blade of whereas the paraconid is diminished in m1 maintains its plesiomorphic orientation height relative to the Orellan species. The an- and has not migrated anteriorlyÐParada- terolabial corner of m2 protrudes even more phoenus differs from small contemporary ca- than in the Orellan mandible. Because the nids such as Hesperocyon in these carnassial talonid is broadened, with a larger basin, m2 traits. has a more rectangular occlusal outline than It is particularly interesting that the teeth in the Orellan m2. of some living foxes have converged on the AMNH 6852 (P. cuspigerus) represents dental pattern seen in the younger species of the end member in this trend to broaden and Paradaphoenus. For example, the second enlarge m2-3 in the Paradaphoenus lineage molars of the North American Gray Fox, (®g. 6). Its m2 trigonid is strongly crowded Urocyon cinereoargenteus, are enlarged rel- to the front of the tooth, more toward the ative to M1/m1; the P4 is short with abbre- anterolingual corner; an expansion of the an- viate protocone, and the premolars and ca- terolabial shoulder completes the rectangular nines are similar in form to these teeth in form of m2. A cingulum surrounds m2, par- John Day P. cuspigerus (Hough, 1948b). ticularly prominent labially, where it also However, despite the dental similarities, ba- contributes to the squaring of the tooth. The sicranial anatomy demonstrates that these talonid is very broad and strongly basined, small amphicyonids and small canids are with developed entoconid and hypoconid only distantly related. 14 AMERICAN MUSEUM NOVITATES NO. 3331

BASICRANIUM body weights for Orellan to Arikareean Par- adaphoenus is estimated at ϳ1±3 kg. The three known skulls of Paradaphoenus Because two of the three Paradaphoenus (AMNH 39099, AMNH 6852, 6853) have skulls are crushed, details of cranial anatomy, well-preserved basicrania, including the au- such as suture pattern, are dif®cult to inter- ditory regions. An Orellan skull of P. mini- pret. However, general anatomical propor- mus (®g. 3), originally described by Hough tions and structures are evident. In life, these (1948a) as Daphoenus minimus, is slightly small carnivores were narrow-snouted and crushed dorsoventrally, but is otherwise in- dolichocephalic. The postorbital length is tact except for the anterior rostrum and the nearly two times the preorbital (table 1), in- auditory bullae, which have been lost. The dicating cranial proportions like those of Arikareean skull of the John Day P. cuspi- many primitive arctoid, cynoid, and aeluroid gerus holotype (®g. 2, AMNH 6852) is un- carnivorans. Although the volume of the crushed, includes both mandibles, and pre- braincase is somewhat greater in Arikareean serves not only the auditory region but also P. cuspigerus relative to Orellan P. minimus, the right auditory bulla in life position (®g. the cerebrum has not overgrown the cerebel- 9). The second P. cuspigerus skull from the lum to the extent seen in living canids of John Day (AMNH 6853) also includes the similar body size, such as the smaller foxes. right bulla in life position, but was dorso- The form of the cranium is not signi®cantly ventrally crushed and is lacking much of the different from that of an early canid such as dorsal surface of the rostrum, orbital region, Hesperocyon. and braincase. Its basicranium is one of the The auditory bulla and its relationship to best preserved parts of this skull (®g. 10). surrounding basicranial elements distinguish- These skulls demonstrate the small size of es Paradaphoenus from small contemporary Paradaphoenus. Basilar lengths of the three canids such as Hesperocyon. The osseous known crania are: 94.8 mm, AMNH 6852 bulla more completely encloses the auditory (holotype); ϳ100 mm, AMNH 6853; ϳ88 region in Hesperocyon relative to Parada- mm, AMNH 39099 (table 1). This range is phoenus. Even in very young juveniles of similar to skulls of European Cynodictis (®g. Hesperocyon, the auditory bulla is fully os- 8, NMB Q.V. 412, ϳ109 mm; also Teilhard, si®ed and completely encompasses the au- 1915, P1. II, ϳ100 mm; Petter, 1966). ditory region, including the petrosal promon- Basilar lengths for Paradaphoenus (ϳ88± torium. This enclosure is accomplished by 100 mm) are smaller than those of the larger the application of an ossi®ed caudal entotym- living foxes and jackals:ÐVulpes vulpes panic element to the inner edge of the ecto- (basilar length of 125±137.5 mm, N ϭ 12), tympanic, and the extension of this caudal Urocyon cinereoargenteus (110.4±119.1, N entotympanic to the margins of the posterior ϭ 7), Canis mesomelas (137±141 mm, N ϭ auditory region. Caudal entotympanic expan- 2), and Alopex lagopus (119.2, N ϭ 1). Par- sion (resulting from posterior in¯ation of the adaphoenus more closely approaches the bulla) during ontogeny in Hesperocyon is in- smaller foxes, Vulpes velox (105±106 mm, N dicated by the lesser degree of caudal ento- ϭ 2) and Fennecus zerda (78.6±83.5 mm, N tympanic in¯ation in the juvenile (UNSM ϭ 3). The skulls of late Eocene and Oligo- 25700) than in the adults (UNSM 25402, cene Hesperocyon from the White River 25704). However, in both juvenile and adult beds of North America are often somewhat Hesperocyon, the posterior auditory region is smaller, ranging between 80 and 90 mm. always completely enclosed by the bulla. The Fennec foxes of north Africa are the small- caudal entotympanic is closely applied est living canids, with body weights of 1±2 against mastoid and occipital bones, and as kg. The Swift Fox (Vulpes velox) is some- a result, the only openings exiting the pos- what larger at 1.8±3 kg (Nowak, 1991). Al- terior auditory region are the posterior lac- though the species of Paradaphoenus are not erate and stylomastoid foramina. In Para- as large-brained as these small living canids, daphoenus the posterior auditory region is body size relative to basilar length of skull not completely enclosed by the ossi®ed bul- is probably comparable, hence the range of la; the posteromedial corner of the petrosal 2001 HUNT: OLIGOCENE AMPHICYONIDS 15

Fig. 9. Stereophotographs of the basicranium of Paradaphoenus cuspigerus (AMNH 6852, holotype), John Day Formation, Oregon: (A) ventral view; (B) lateral view. is exposed, and the ossi®ed bulla extends at ed, relative to the ectotympanic of contem- most 1±2 mm behind the point of attachment porary Daphoenus, suggesting that a small of the tympanohyal. amount of ectotympanic growth has occurred The ossi®ed bulla of Paradaphoenus ap- in Paradaphoenus in an attempt to more ful- pears to be formed by the ectotympanic ly enclose the auditory region. Because the alone, whereas in Hesperocyon, an ossi®ed presence of an ossi®ed caudal entotympanic caudal entotympanic is added to the ectotym- is certain in Hesperocyon, where it can be panic (®g. 11). The ectotympanic of Para- observed in older juveniles (UNSM 25700), daphoenus is slightly wider and more in¯at- it probably does not occur in Paradaphoen- 16 AMERICAN MUSEUM NOVITATES NO. 3331

Fig. 10. Stereophotographs of the basicranium of Paradaphoenus cuspigerus (AMNH 6853, referred), John Day Formation, Oregon: (A) ventral view; (B) lateral view. us, although the possible presence of a small, and only slightly posteriorly in¯ated ecto- narrow, laminar caudal entotympanic at- tympanic bone. tached to the medial rim of the ectotympanic The petrosal and surrounding middle ear (as in Ursus americanus, Hunt 1974, ®gs. 13, region can be observed in all three Parada- 14) cannot be entirely ruled out in Parada- phoenus skulls. In the two John Day skulls, phoenus. Nevertheless, in comparing the bul- the bulla has been lost from the left auditory lae of Arikareean Paradaphoenus (AMNH region, providing a clear view of the middle 6852, 6853) to juvenile Hesperocyon bullae ear (this area is slightly crushed and dis- (in which the ectotympanic and caudal en- placed in AMNH 6853). The auditory re- totympanic can be certainly identi®ed) and to gions of the John Day skulls and the Orellan the bullae of adult carnivorans (Daphoenus, Paradaphoenus skull are extremely similar, Nandinia), in which an ossi®ed ectotympanic although the Orellan species was smaller in is present as a separate element, it seems body size. In addition, the form of the petro- most probable that the bulla of Parada- sal and the detailed anatomy of the auditory phoenus is formed exclusively by a widened region of the Orellan P. minimus are also 2001 HUNT: OLIGOCENE AMPHICYONIDS 17

Fig. 11. Comparison of ontogenetic elements contributing to the auditory bulla of the small amphicyonid Paradaphoenus (left) and the canid Hesperocyon (right). T, ectotympanic; E, caudal entotympanic. comparable to the larger Orellan amphicyon- The basioccipital is wide relative to the nar- ids Daphoenus vetus and D. hartshornianus. row basioccipital of Oligocene canids in Thus, a common basicranial structure is which the expanding bulla restricts the width shared by the Oligocene North American of the basicranial axis. The plesiomorphic Daphoenus and Paradaphoenus that places state of the Paradaphoenus auditory region them within the Amphicyonidae. is indicated by the broad basioccipital, the The form of the petrosal promontorium is rudimentary auditory bulla, and by the lack similar in these amphicyonids. All are of the of any extension of the middle ear cavity be- arctoid type, in which the posterior promon- hind the promontorium and mastoid process torium is slightly elevated, its surface grad- (in many living aeluroids the middle ear cav- ually sloping dorsad anteriorly. There is no ity is extended posteriorly by in¯ation of the ventral process of the promontorium as seen caudal entotympanic). in aeluroid carnivorans (Hunt, 1989). By The widened ectotympanic of the P. cus- comparing damaged and undamaged petro- pigerus holotype (AMNH 6852) indents the sals of Paradaphoenus and Daphoenus,itis tympanic wing of the alisphenoid, creating a evident that the medial part of the promon- moderately deep depression on its surface. torium in these genera is a rather fragile can- Lateral to this depression is the postglenoid cellous extension of the bone directly en- foramen for the external jugular vein and closing the cochlea. In some individuals this posterior to it, a prominent pit for the anterior medial part is broken open to reveal internal crus of ectotympanic. The indentation for the cancellae. alisphenoid and the depth of the pit for the In the skulls of Paradaphoenus, the me- anterior crus are much more developed in dial margin of the petrosal contacts the edge AMNH 6852 relative to AMNH 39099, the of the basioccipital, but there is no suturing Orellan species, indicating that the ectotym- of petrosal to basioccipital as occurs in ca- panic was not as broadened and in¯ated in nids. The margin of the basioccipital is deep- the Orellan P. minimus. ly excavated for the inferior petrosal venous Because the ectotympanic is in life position sinus (Hunt, 1977; Hunt and Barnes, 1994). in the John Day Paradaphoenus skulls, its re- 18 AMERICAN MUSEUM NOVITATES NO. 3331 lationship to the petrosal promontorium and pigerus. Teeth of the oldest species, P. min- to adjacent basicranial bones can be deter- imus, are little modi®ed and unspecialized. mined. In both skulls, the inner margin of the Molars of P. tooheyi are the ®rst to show the ectotympanic broadly contacts the basioccip- broadening that typi®es the descendant spe- ital, resting against it, and in AMNH 6853 the cies of Paradaphoenus. The broadened mo- basioccipital margin is de¯ected ventrad to lars of the youngest species, John Day P. support the ectotympanic. Furthermore, the cuspigerus, are more derived than the molars posterointernal margin of the ectotympanic in of either P. minimus or P. tooheyi from the AMNH 6853 rests against the promontorium Great Plains. just anteromedial to the round window where The recent discovery of P. tooheyi from it produces a ¯at facet; on the left promon- Whitneyan and early Arikareean sediments torium of AMNH 6853, this facet is conspic- ®lls both a temporal and morphological gap uous (®g. 10). In AMNH 6852 the ectotym- between P. minimus and P. cuspigerus. The panic closely approaches the promontorium temporal range of the genus is estimated to and the edge of the ectotympanic is con®g- be from ϳ34 Ma to possibly as young as ured to ®t against its surface, but contact is ϳ23±25 Ma, but the upper range limit is un- not made, because tuffaceous silt intervenes certain because of the absence of detailed to prevent the seating of the ectotympanic stratigraphic data for the John Day fossils. against the promontorium. Because of a dam- Three skulls of Paradaphoenus are known aged promontorium in AMNH 39099, the (an Orellan skull of P. minimus and two John presence of a similarly placed facet in the Or- Day skulls of P. cuspigerus), and they ade- ellan species is uncertain. quately preserve skull form, dentition, and It is interesting that the form of the pos- basicranium. The two John Day skulls also teromedial face of the ectotympanic that con- retain the auditory bulla. Basicranial anato- tacts the promontorium is somewhat differ- my re¯ects the amphicyonid pattern and is ently shaped in AMNH 6852 and 6853; in similar to that of the early amphicyonids, addition, the basicranium of AMNH 6853 is Daphoenus and Cynodictis. slightly larger in size and more robust than Despite similarities in skull form, body that of AMNH 6852. Whether this is the re- size, and dentition, basicranial anatomy dis- sult of intraspeci®c or sexual variation, and/ tinguishes small amphicyonids such as Par- or due to a temporal difference, is unknown adaphoenus (North America) and Cynodictis because of the lack of detailed stratigraphic (Europe) from contemporary small hespero- information for these two skulls. Neverthe- cyonine canids in North America. From their less, the form of the ectotympanic, its rela- earliest appearance, canids fully enclose the tionship to the promontorium, the embayed auditory region with an ossi®ed auditory bul- lateral margin of the basioccipital, and the la formed by an ectotympanic and a caudal plesiomorphic state of the auditory region entotympanic. An ossi®ed caudal entotym- separates Paradaphoenus from contempo- panic exists as a discrete element applied to rary canids, and allies the genus with the the inner edge of the ectotympanic in juve- Amphicyonidae. nile Hesperocyon; the subsequent growth and in¯ation of this caudal entotympanic, com- SUMMARY AND CONCLUSIONS pletely enclosing the auditory region, is the hallmark of the Canidae. In Paradaphoenus This report summarizes all known fossil and other contemporary North American Ol- material of the genus Paradaphoenus from igocene amphicyonids, only the ectotympan- North America. These fossils appear to be- ic is ossi®ed, and in Paradaphoenus it ap- long to a single lineage of very small am- pears to be the only bulla component, at most phicyonids (ϳ1±3 kg) that ranged from the only slightly broadened and in¯ated, leaving Paci®c Northwest eastward to the central the posterior promontorium exposed. Based Great Plains. The lineage includes three spe- on the capsular form of the Paradaphoenus cies: the Orellan P. minimus; the Whitneyan ectotympanic, the existence of additional ®- to early Arikareean P. tooheyi, n. sp.; and the brous or cartilaginous contributions from the late early or possibly mid-Arikareean P. cus- tympanic membrane are considered unlikely, 2001 HUNT: OLIGOCENE AMPHICYONIDS 19 and the auditory bulla appears to be formed Skolnick. For helpful reviews of the manu- entirely by an ossi®ed ectotympanic element. script, I particularly appreciate the comments Using extant small foxes (e.g., Vulpes ve- of Bruce MacFadden (University of Florida), lox, Fennecus zerda) as analogs, the species Matt Joeckel (Bellevue University), and Ted of Paradaphoenus are interpreted as small, Fremd (John Day Fossil Beds National Mon- foxlike carnivores that preyed upon small ver- ument), and two anonymous reviewers. tebrates, but also relied on insects, eggs, fruits, and seeds in season. Their interaction REFERENCES and possible competition with the small con- Cope, E. D. temporary hesperocyonine canids remains 1878. On some characters of the Miocene speculative, but if the relative representation fauna of Oregon. Paleontol. Bull. 30: of fossils of small canids and Paradaphoenus 1±16. in the North American record is an accurate 1879. Second contribution to a knowledge of re¯ection of their abundance in Oligocene en- the Miocene fauna of Oregon. Paleon- vironments, the canids must have far outnum- tol. Bull. 31: 1±7. bered these small amphicyonids. Wang (1994) 1884. The Vertebrata of the tertiary forma- lists 5 Orellan, 8 Whitneyan, and at least 14 tions of the West. Rep. US Geol. Surv. early Arikareean hesperocyonine canids in Territories, Vol. 3. Washington, DC: Gov't. Printing Of®ce, 1009 pp., 75 North America. Even if the actual number of plates. hesperocyonine species is to some degree ex- Hough, J. R. aggerated, the canids are clearly more diverse. 1948a. A systematic revision of Daphoenus After the Arikareean land mammal age, small, and some allied genera. J. Paleontol. fox-sized amphicyonids are extinct in North 22(5): 573±600. America, yet a variety of small canids (Ͻ 20 1948b. The auditory region in some members kg) thrive in the early, medial, and late Mio- of the Procyonidae, Canidae, and Ur- cene, most species failing to attain large body sidae. Bull. Am. Mus. Nat. Hist. 92(2): size (80±100 kg). In the early and medial 67±118. Miocene, as well as the early part of the late Hunt, R. M., Jr. 1974. The auditory bulla in Carnivora: an an- Miocene (Clarendonian), these smaller canids atomical basis for reappraisal of carni- are accompanied by large amphicyonids and vore evolution. J. Morphol. 143: 21±76. hemicyonine ursids, which at that time dom- 1977. Basicranial anatomy of Cynelos Jour- inate the niche for large predatory carnivorans dan (Mammalia, Carnivora), an Aqui- in North America. tanian amphicyonid from the Allier Ba- sin, France. J. Paleontol. 51: 826±843. ACKNOWLEDGMENTS 1989. Evolution of the aeluroid Carnivora: signi®cance of the ventral promontorial For their efforts in the 1992 excavation of process of the petrosal, and the origin Wagner Quarry that produced the holotype of basicranial patterns in the living families. Am. Mus. Novitates 2930: 32 mandible of Paradaphoenus tooheyi, n. sp., pp. I thank Loren Toohey, Rob Skolnick, and 1996. Amphicyonidae (Chapter 23). In D. Xiao-feng Chen. Permission to excavate Prothero and R. J. Emry (eds.), The ter- Wagner Quarry was generously given by Mr. restrial Eocene-Oligocene transition in Walt Montague, Chadron, Nebraska. For loan North America: 476±485. London: of the skulls of Paradaphoenus cuspigerus Cambridge Univ. Press. from the John Day beds of Oregon and the 1998. North American Tertiary Amphicyoni- skull of P. minimus from the White River dae. In C. Janis, K. Scott, and L. Jacobs Group, South Dakota, I am grateful to R. H. (eds.), Tertiary mammals of North Tedford and M. C. McKenna (AMNH). Fig- America: 196±227. London: Cam- bridge Univ. Press. ures 1 and 11 were prepared by UNSM il- Hunt, R. M., Jr., and L. G. Barnes lustrator Angie Fox; preparation of the Par- 1994. Basicranial evidence for ursid af®nity adaphoenus skulls was capably undertaken of the oldest pinnipeds. In A. Berta and by Ellen Stepleton, and the holotype man- T. A. DemeÂreÂ (eds.), Contributions in dible of P. tooheyi was prepared by Rob marine mammal paleontology honoring 20 AMERICAN MUSEUM NOVITATES NO. 3331

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APPENDIX 1 (Stratigraphic and Locality Data) Orellan Whitneyan 1) AMNH 39099, Lower Oreodon beds, Brule 6) UNSM 26130, Brule Fm., 30 feet below Fm., southwest of Sheep Mountain, near Scenic, Brule-Gering contact, E1/2, section 36, T.20N., South Dakota, collected by J. Bird, 25 July 1940. R.56W., Banner Co., Nebraska. 2) UNSM 25305, Orella ``A'', Brule Fm., UNSM Loc. Sx-25, northwest of Crawford, Ne- braska. Arikareean 3) UNSM 25030, Orella ``A'', Brule Fm., 7) UNSM 6002-92, Wagner Quarry, excavated UNSM Loc. Sx-26, northwest of Crawford, Ne- in a lower Arikaree Group ¯uvial channel ®ll in- braska. cised in White River Group sediments, southwest 4) UNSM 25148, Orella Member, Brule Fm., of Chadron, Nebraska. UNSM Loc. Sx-14, northwest of Crawford, Ne- 8) LACM 21649, Sharps Fm., LACM Loc. braska. 1981, Wounded Knee area, South Dakota, col- 5) UNSM 26139, Brule Fm., White River lected by J. R. Macdonald, 23 July 1962. Group, Scottsbluff Co., Nebraska. 9) AMNH 6852, John Day Fm., John Day val- ley, Oregon. 10) AMNH 6853, John Day Fm., John Day val- ley, Oregon.

APPENDIX 2 Differential diagnosis of Paradaphoenus tooh- imus in which crowding does not occur; m2 proto- eyi, n. sp.: and metaconids accentuated, and paraconid dimin- P4 length/ M1-2 length, 77-78% relative to 80- ished, relative to P. minimus; m2 width 4.3 mm 81% for P. minimus and 67-74% for P. cuspigerus; relative to 3.6±3.9 mm in P. minimus; m1-2 tal- m1-2 talonids transversely broadened with promi- onids not as expanded as in P. cuspigerus;m1 nent basins relative to P. minimus which lacks width 4.4±4.5 mm relative to 5.2 mm in P. cus- broadly basined talonids; m2 trigonid reduced and pigerus; M1-2 not as enlarged and transversely crowded to the front of the tooth relative to P. min- broadened as M1-2 of P. cuspigerus (table 2).