Significance of the ventral promontorial process of the petrosal, and the origin of basicranial patterns in the living families

32 p. : ill. ; 26 cm.Includes bibliographical references (p. 30-32)

Aeluroid carnivore evolution

24 p. : ill., 1 map ; 26 cm.Includes bibliographical references (p. 23-24).The living Asian linsang, Prionodon pardicolor, shares marked anatomical similarities in basicranium and dentition with the extinct Oligocene aeluroid, Palaeoprionodon lamandini, from the Quercy fissures, France. The living African linsang, Poiana richardsoni, is similar yet slightly more derived in basicranial traits relative to Prionodon pardicolor, and also has basicranial and dental features indicating a relationship to the living genets (Genetta). The basicranial and auditory anatomy of a series Palaeoprionodon-Prionodon-Poiana can be interpreted as a morphocline showing the progressive alteration of the form of the petrosal and auditory bulla from the plesiomorphic aeluroid state in the Quercy fossils to a derived condition typical of the linsangs (Prionodon, Poiana) and living genets (Genetta). The basicranial anatomy of Genetta, including the structure of the petrosal and auditory bulla, is typical of other species of the Viverridae. The other lineages of living viverrids are believed to have undergone a similar transformation in their basicranial anatomical pattern from the plesiomorphic state present in Oligocene aeluroids, exemplified by Palaeoprionodon, to the modern patterns typical of the living subfamilies (including the endemic Malagasy viverrid genera)

Viverrid affinities of the Miocene carnivoran Herpestides

34 p. : ill. ; 26 cm.Includes bibliographical references (p. 33-34

Diversity of the earliest aeluroids from Eurasia (Quercy, Hsanda-Gol) and the origin of felids

65 p. : ill. ; 26 cm.Includes bibliographical references (p. 62-65).The oldest known fossil aeluroids are from Lower Oligocene sediments in France (Quercy) and Upper Eocene-Lower Oligocene sediments in Mongolia. These small (< 5 kg) carnivorans are primarily represented by mandibles, with hypercarnivorous dentitions in almost all lineages. The six aeluroid genera from France and those from Mongolia share a common dental pattern despite their geographic separation near the extremes of the Eurasian landmass. This similarity is not surprising, however, because faunal exchange across Eurasia at this time is documented not only by populations of small aeluroids but also by small arctoid carnivorans. Basicrania of Oligocene aeluroids are preserved only in the Quercy deposits. The auditory regions of two genera from Quercy (Palaeoprionodon, Stenoplesictis), and of two additional aeluroid genera (Stenogale, Proailurus) known only from mandibles at Quercy (but matched with congeneric mandibles with associated basicrania from early Miocene sediments at St.-Gérand), reveal a common basicranial morphotype. The living African palm civet Nandinia binotata retains a basicranial and auditory anatomy closely approaching the ancestral aeluroid morphotype. European paleontologists working with the Quercy faunas have regarded several of these aeluroids as early members of the Viverridae and Felidae. However, basicrania of the Quercy and St.-Gérand aeluroids share a common petrosal morphology overprinted by anatomically distinctive and evolutionarily divergent auditory bulla types that differ from those of living felids and viverrids. These basicranial patterns suggest their recent common ancestry more strongly than they support any potential affinity with living viverrids and felids. Among the Quercy crania, only Palaeoprionodon shares significant similarities with a living viverrid, the Asian linsang Prionodon. No early felid crania are known from Quercy deposits. The oldest known basicrania with derived features indicative of felid affinity are those of Proailurus lemanensis and Stenogale julieni, from St.-Gérand, France. They share a derived petrosal morphology that incorporates a uniquely configured bony flange on the medial border of the promontorium. Proailurus lemanensis, long considered to be an ancestral felid, has a particularly distinctive, dorsally depressed petrosal flange produced by auditory bulla hypertrophy. This Proailurus pattern may be derived from the more plesiomorphic basicranium of Stenogale julieni, and together the two genera could be included in a felid subfamily Proailurinae, or, alternatively, the proailurines could be limited to Proailurus and its descendant taxa. Living felids share a morphologically uniform petrosal morphology that lacks the medial flange of the promontorium present in Proailurus and Stenogale. In the living felids the flange is either suppressed and/or reoriented so that it bears no resemblance to the archaic petrosal type. However, the oldest known early and mid-Miocene New World felids (Ginn Quarry, Echo Quarry) described in this study retain archaic petrosals more similar to the petrosal of Proailurus than those of living felids. The origin of the derived petrosal of living felids has yet to be identified among the fossil felids of the later Neogene. The auditory region of the oldest known New World felid (latest early Miocene) from Ginn Quarry, Nebraska, retains a more plesiomorphic petrosal than known in St.-Gérand Proailurus, yet the Ginn Quarry cat is geologically younger. The existence of these two archaic petrosal morphs in early Miocene felids suggests that at least one other felid lineage was present in the early Miocene in addition to Proailurus lemanensis. The subfamily Stenoplesictinae (including Stenoplesictis and Palaeoprionodon) is a paraphyletic taxon lacking reliable derived traits to unite its genera, and the name is no longer employed. The origins of the Herpestidae and Hyaenidae are not illuminated in any way by fossils from Quercy or from Mongolia, and the oldest members of these families are not recorded in the Oligocene

Aeluroid Carnivora

74 p. : ill. ; 26 cm.Includes bibliographical references (p. 71-74).Evolutionary lineages among living and extinct Carnivora can be identified by a diagnostic pattern of ontogenetic elements forming the auditory bulla enclosing the middle ear, best observed in newborn and juvenile animals. However, in the fossil record, the delicate unfused bulla parts of very young carnivorans are rarely preserved. Thus bulla composition in extinct lineages is difficult to determine unless juveniles with well-preserved auditory bullae can be found. Discovery in 1981 of an intact cranium of a juvenile aeluroid carnivoran (Dinictis) from the White River Group (Oligocene) in northwestern Nebraska has resulted in an improved understanding of bulla structure in Nimravidae, extinct catlike carnivorans of the Oligocene and Miocene of the northern continents. Bulla structure indicates that nimravids are not close relatives of the living cats (Felidae), nor are they ancestral to them. Analysis of the auditory region supports the view of Piveteau (1931) and Teilhard (1945) that two major radiations (nimravids, felids) of catlike mammals have occurred on the northern continents during the last 35 to 40 million years. The auditory bulla of Dinictis is formed by three ontogenetic elements: (1) a small bony rostral entotympanic with septate lateral margin confined to the anterointernal comer of the auditory region; (2) a bony planar ectotympanic with highly produced styliform process developed to close the anteroexternal bulla wall; (3) a caudal entotympanic divided into ossified dorsal and cartilaginous ventral parts, forming the anterointernal, medial, and posterior walls and ventral floor of the bulla. These elements join during ontogeny to produce a single chambered bulla lacking a true septum bullae. However, the anterointernal bulla wall of Dinictis contains a small vertically oriented partition formed by entotympanic elements here named the proseptum, a structure previously mistaken for the septum bullae of felids. Nimravid auditory bullae are derivable from an aeluroid morphotype bulla formed by three ontogenetic elements: a ventrally concave septate rostral entotympanic, a crescentic nearly planar ectotympanic, and a single small probably L-shaped caudal entotympanic without inflected ventral edge, the latter element intervening between ectotympanic and rostral entotympanic. Intervention of the caudal entotympanic between ectotympanic and rostral entotympanic is termed the athictic condition, and occurs in nimravids and Nandinia. In viverrids, herpestids, and hyaenids, a thictic condition is achieved by fusion of ectotympanic with rostral entotympanic, excluding the caudal entotympanic from the space between them. In felids, this ectotympanic-rostral entotympanic contact is delayed into later ontogeny, resulting in the bradynothictic condition. Thictic and bradynothictic bullae of viverrids, herpestids, hyaenids, and felids can be derived from the athictic morphotype bulla. The African aeluroid Nandinia binotata is the only living carnivoran in which the structure of the auditory region closely approaches the projected aeluroid morphotype; the bulla of Nandinia is representative of a primitive state from which all living and fossil aeluroid bullae can be derived

Temnocyonine radiation.

153 p. : ill., maps ; 26 cm.This study describes and summarizes the Temnocyoninae (Mammalia, Carnivora), a subfamily of amphicyonid carnivores of considerable diversity and singular comorphology within Cenozoic faunas of North America. In temnocyonines, we see the first carnivorans to occupy an ecological niche as large cursorial predators. The subfamily is confined to the Arikareean NALMA, ranging in age from the latest early Oligocene to the early Miocene. Distributed from the Pacific Northwest to the Great Plains and Florida, there are four genera (Temnocyon, Mammacyon, Delotrochanter n. gen., Rudiocyon n. gen.) and 12 species, of which eight are newly described (Temnocyon subferox, T. fingeruti, T. macrogenys; Rudiocyon amplidens; Mammacyon ferocior; Delotrochanter petersoni, D. oryktes, D. major). Among the specimens examined are eight skulls, three with intact basicranial morphology that establish the presence of a plesiomorphic arctoid auditory region in the subfamily. Temnocyonine dentitions and postcranial skeletons reveal a blend of morphological characteristics not previously nor subsequently seen among the Carnivora. From a stem species, Temnocyon altigenis, there evolve both large hypercarnivorous (Temnocyon) and durophagous forms (Mammacyon, Delotrochanter); these genera share a derived dentition that defines the Temnocyoninae. Delotrochanter oryktes n. sp., an early Miocene species, was found in a den, suggesting a possible burrowing capability and sheltering of offspring. The John Day basin of Oregon and the central Great Plains (western Nebraska, southeast Wyoming) are the source of most temnocyonine fossils; a few have been found in southern California and Florida, indicative of a continent-wide distribution. Temnocyonines have often been confused with canids, however their basicranial anatomy places them securely within the Amphicyonidae. First discovered in the 1870s, only [about] 30 individuals comprise the entire record of the subfamily. Many were found in proximity to radioisotopically calibrated tuffs and ignimbrites and/or were closely associated with mammals of established biochronologic age. Thus, most species can be placed in a temporal context. With rare exception, the fossils represent isolated occurrences, hence estimates of variation within a population are lacking. Cursorial postcranial features characterize several lineages (Mammacyon, Delotrochanter) and probably were present in other temnocyonines known only from dental remains. Late Oligocene Mammacyon ferocior and early Miocene Delotrochanter oryktes evolved uniquely configured crushing cheek teeth and cursorial limbs, combining distinctive dental and skeletal traits in a manner not seen in any living carnivore. These species are interpreted as large durophagous predators with craniodental characteristics that parallel living hyaenids (Crocuta crocuta) and postcranial adaptations approaching those of cursorial canids such as the wolf (Canis lupus). Expansion of semiarid grasslands and savanna during the late Oligocene and early Miocene in the central Great Plains seems to have favored the evolution of these wide-ranging durophagous amphicyonid carnivores. Analysis of the jaws of temnocyonines employing Therrien's method of beam analysis demonstrates pronounced bending strength focused beneath the crushing dental battery in the molar region. Similarly, the canines and mandibular symphysis manifest an ability to resist strong parasagittal, transverse, and torsional forces occurring during prey capture and feeding. Temnocyonines share a pronounced similarity in dentition with European haplocyonine beardogs, which doubtless are their sister group among the Amphicyonidae. Some haplocyonines also show cursorial tendencies. Examination of European material, however, reveals subtle dental distinctions indicating that the evolution of the two subfamilies proceeded separately yet in parallel in Europe and North America

Oligocene amphicyonids

20 p. : ill., 1 map ; 26 cm.Includes bibliographical references (p. 19-20).North American amphicyonid carnivorans are important members of the mid-Cenozoic terrestrial carnivore community during the late Eocene to late Miocene (Duchesnean to Clarendonian). Species range in size from 200 kg. Among the smallest and rarest amphicyonids are Oligocene species of Paradaphoenus Wortman and Matthew, found at a few localities in the Great Plains and the Pacific Northwest. Paradaphoenus is known from only 10 individuals placed in 3 species (P. minimum; P. tooheyi, n. sp.; P. cuspigerus), representing a single lineage ranging from the Orellan to Arikareean. The existence of three skulls, one with associated mandibles, allows the identification of diagnostic basicranial and dental traits that place the genus in the Amphicyonidae. Basicranial anatomy, including a rudimentary ectotympanic auditory bulla, distinguishes the genus from more abundant small contemporary canids, such as Hesperocyon. The species of Paradaphoenus most likely adopted ecological roles similar to the smaller living foxes

John Day Formation

90 p. : ill. (1 col.), maps ; 26 cm.Includes bibliographical references (p. 69-72).The John Day Formation of north-central Oregon preserves a succession of speciose, superposed Oligocene through early Miocene mammalian faunas that establish the sequence of mid-Cenozoic mammalian evolution within the Pacific Northwest. Upper John Day rock units initially described by Merriam (1900, 1901) in the Kimberly and Haystack Valley areas were later divided into lower (Kimberly) and upper (Haystack Valley) members by Fisher and Rensberger (1972). We focused our study on the lithostratigraphic succession within the Haystack Valley Member. Rocks previously included in the Haystack Valley Member can be subdivided into four unconformity-bounded, genetic lithostratigraphic units that range in age from ~24 to ~18 Ma, three of the units incorporating age-diagnostic mammalian faunas. We have identified two principal depositional units within the Haystack Valley Member of Fisher and Rensberger south of Kimberly: (1) Johnson Canyon Member--late or latest Arikareean tuffaceous siltstones and fine sandstones (~?19-22.6 Ma) with fluvial monomictic intraformational pebble gravels, well exposed along the west wall of the John Day valley; (2) Rose Creek Member--coarse polymictic welded tuff-bearing gravels, debris flows, coarse obsidian-shard tuffs, and fine-grained tuffaceous units, yielding early Hemingfordian mammals (~18.2-18.8 Ma), deposited in angular unconformity on lower units of the John Day Formation along the east wall of the John Day valley. At Balm Creek in the type area of the Haystack Valley Member, the southern limb of the Balm Creek syncline exhibits the most complete local section of upper John Day rocks, here comprising three members: (1) a revised Haystack Valley Member made up of early late Arikareean ribbed tuffs (~23.5-23.8 Ma) with monomictic welded tuff conglomerate channels, overlain by a gray massive airfall marker tuff (GMAT); (2) Balm Creek Member--tuffaceous late Arikareean siltstones and fine sandstones interbedded with lacustrine tuffs, overlain by stacked fluvial fining-upward sequences and gray airfall tuffs; (3) Rose Creek Member--coarse polymictic welded tuff-bearing gravels, debris flows, lacustrine units, and fine-grained tuffaceous sediments, believed to correlate to the fossiliferous early Hemingfordian unit south of Kimberly. The complexity of upper John Day rocks (evidenced by marked lithofacies variation within multiple unconformity-bounded subunits, punctuated by numerous paleosols) suggests an early Miocene depositional regime with more varied local environments and pronounced episodic sedimentation relative to the more uniform Oligocene environments documented by lower John Day strata. Whereas the lower John Day Formation consists of fine-grained volcaniclastic sediments that were deposited in basins with minimal topographic relief, the upper John Day Formation is characterized by a succession of increasingly coarse fluvial channel fills, as well as compression appears to have triggered fluvial incision and valley filling from ~24 Ma to at least ~19 Ma. Extension in latest John Day times resulted in the development of half-grabens or grabens both in Haystack Valley and south of Kimberly, ensuring the preservation of upper John Day sediments. Significantly, a final episode of normal faulting appears to have immediately preceded the earliest eruption of Picture Gorge Basalt, as evidenced by flows of the Twickenham Member (PGBS) abutting against vertical fault scarps south of Kimberly. The faunas of the upper John Day units thus play a critical role in dating a complex sequence of tectonic events which preceded the onset of Columbia River Basalt Group flooding in the early Miocene

Hyaenid affinities of the Miocene carnivoran Tungurictis spocki from Inner Mongolia

25 p. : ill., map ; 26 cm.Includes bibliographical references (p. 24-25

Neogene amphicyonid Borocyon.

95 p. : ill. (1 col.), map ; 26 cm. Includes bibliographical references (p. 84-87).In the early Miocene, endemic North American amphicyonids of the subfamily Daphoeninae evolved a lineage of large beardogs adapted for prey pursuit over open terrain. Three species comprise this lineage, here placed in the genus Daphoenodon, subgenus Borocyon Peterson, 1910, the sister subgenus to the daphoenine beardog Daphoenodon (Daphoenodon). These species (Borocyon robustum, B. niobrarensis, B. neomexicanus, n. sp.) are distinguished by limbs modified for fore-aft motion and parasagittal alignment contributing to a lengthened stride. These adaptive features are most evident in the terminal species, B. robustum, where the forelimb is conspicuously elongated. The species of Borocyon increase in body size from small B. neomexicanus, known only from the latest Arikareean of northern New Mexico, through earliest Hemingfordian B. niobrarensis from western Nebraska and southeast Wyoming, to B. robustum, likely the keystone predator of its guild. Borocyon robustum (~ 100-150 kg) was the most widely distributed, occurring during the early Hemingfordian from the Pacific Northwest through the Great Plains to the Florida Gulf Coast. Regional aridity prevalent in the North American midcontinent during the Arikareean may have contributed to the emergence of Borocyon by providing an appropriate niche for a long-legged, open-country predator. The skeleton of Borocyon robustum, based on composite elements acquired over many decades, reveals a carnivoran unlike any living pursuit predator. The species displays a mosaic of postcranial features that parallel limb elements of both highly evolved cursors (Canis lupus, Acinonyx jubatus) and large, ambush felids (Panthera leo, P. tigris). Skeletal traits contributing to its efficient locomotion include: proportionately lengthened forelimbs, the parasagittal radioulnar articulation with the humerus, an elongate radius and ulna, a modified carpal structure, and paraxonic elongate metapodials of the fore- and hindfoot, as well as details of the anatomy of femur, tibia, and proximal tarsals. These postcranial features indicate a large digitigrade predator with a number of anatomical parallels in the forelimb to running pursuit predators such as the wolf, but there are also musculoskeletal adaptations of the shoulder and hindlimb that compare with those of large, living felids. Skull, dentition, and mandibular anatomy are similar to those of living wolves. However, Borocyon robustum, on average a much larger carnivore, placed even greater emphasis on a pattern of dental occlusion and toothwear suggesting both carnivory and durophagous habits. Physiological attributes of Borocyon that may have contributed significantly to its adaptive program as a pursuit predator remain unknown