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A large collection of dentigerous jaws quarried from the Gao Mine locality, late Paleocene, Paskapoo Formation, central Alberta, Canada, documents a new species of the early Paleogene phenacodontid “condylarth” Ectocion Cope, 1882. The new species, Ectocion stockeyae, the smallest of the genus, occurs well before the abrupt global warming at the Paleocene–Eocene Thermal Maximum, an event purportedly causing the rapid evolution of “dwarfed” mammals, including a species of Ectocion; however, there is no evidence of increased temperatures at Gao Mine to account for the small size of Ectocion stockeyae, raising questions of the relationship between temperature and body size in Ectocion. Ectocion stockeyae also exhibits sexual dimorphism of the canines, a pattern in mammals often associated with a population structure in which the males are relatively few and polygynous, resulting in intense male rivalry for mating success. The sample of Ectocion stockeyae from Gao Mine includes a substantial majority of “juvenile” individuals retaining deciduous posterior premolars, many even after eruption of the molars had been completed, suggesting short life spans, accelerated growth, and rapid dental development in this species as expressed in Schultz’s Rule.

We describe the tympanic anatomy of the petrosal of Deltatherium fundaminis, an enigmatic Paleocene mammal based on cranial specimens recovered from New Mexico, U.S.A. Although the ear region of Deltatherium has previously been described, there has not been a comprehensive, well-illustrated contribution using current anatomical terminology. The dental and cranial anatomy of Deltatherium is a chimera, with morphological similarities to both ‘condylarth’ and ‘cimolestan’ taxa. As such, the phylogenetic relationships of this taxon have remained elusive since its discovery, and it has variably been associated with Arctocyonidae, Pantodonta and Tillodontia. The petrosal of Deltatherium is anteriorly bordered by an open space comprising a contiguous carotid opening and pyriform fenestra. The promontorium features both a small rostral tympanic process and small epitympanic wing but lacks well-marked sulci. A large ventral facing external aperture of the canaliculus cochleae is present and bordered posteriorly by a well-developed caudal tympanic process. The hiatus Fallopii opens on the ventral surface of the petrosal. The tegmen tympani is mediolaterally broad and anteriorly expanded, and its anterior margin is perforated by a foramen for the ramus superior of the stapedial artery. The tympanohyal is small but approximates the caudal tympanic process to nearly enclose the stylomastoid notch. The mastoid is widely exposed on the basicranium and bears an enlarged mastoid process, separate from the paraoccipital process. These new observations provide novel anatomical data corroborating previous hypotheses regarding the plesiomorphic eutherian condition but also reveal subtle differences among Paleocene eutherians that have the potential to help inform the phylogeny of Deltatherium.

Evolutionary relationships of the endemic South American ungulates (SANUs), both to each other and to other major placental clades, have been robustly debated for more than a century. Morphological...

The end‐Cretaceous mass extinction allowed placental mammals to diversify ecologically and taxonomically as they filled ecological niches once occupied by non‐avian dinosaurs and more basal mammals. Little is known, however, about how the neurosensory systems of mammals changed after the extinction, and what role these systems played in mammalian diversification. We here use high‐resolution computed tomography (CT) scanning to describe the endocranial and inner ear endocasts of two species, Chriacus pelvidens and Chriacus baldwini, which belong to a cluster of ‘archaic’ placental mammals called ‘arctocyonid condylarths’ that thrived during the ca. 10 million years after the extinction (the Paleocene Epoch), but whose relationships to extant placentals are poorly understood. The endocasts provide new insight into the paleobiology of the long‐mysterious ‘arctocyonids’, and suggest that Chriacus was an animal with an encephalization quotient (EQ) range of 0.12–0.41, which probably relied more on its sense of smell than vision, because the olfactory bulbs are proportionally large but the neocortex and petrosal lobules are less developed. Agility scores, estimated from the dimensions of the semicircular canals of the inner ear, indicate that Chriacus was slow to moderately agile, and its hearing capabilities, estimated from cochlear dimensions, suggest similarities with the extant aardvark. Chriacus shares many brain features with other Paleocene mammals, such as a small lissencephalic brain, large olfactory bulbs and small petrosal lobules, which are likely plesiomorphic for Placentalia. The inner ear of Chriacus also shares derived characteristics of the elliptical and spherical recesses with extinct species that belong to Euungulata, the extant placental group that includes artiodactyls and perissodactyls. This lends key evidence to the hypothesized close relationship between Chriacus and the extant ungulate groups, and demonstrates that neurosensory features can provide important insight into both the paleobiology and relationships of early placental mammals.

Phenacodontidae are a group of archaic ungulates in the early Paleogene and are considered to play an important role in the origin of some other ungulates, including perissodactyls. The early Eocen...

During the early evolution of Equoidea, two families co-existed, Equidae and Palaeotheriidae. Both groups show a similar ancestral molar morphology and evolved from bunodont to lophodont or selenolophodont (lophodont with crescent-shaped cutting edge in some form) respectively, with a clearly pronounced ectoloph. Fossils of the here studied brachydont equids and palaeotheriids are known from the early Eocene to the middle Miocene in North America and Eurasia. Due to the rich fossil record, dental evolution and related functional shifts can be investigated in detail in each family. In this study, we focused on changes in the different masticatory paths, identified different functions within the power stroke and evaluated the efficiency of the different modes in mastication to correlate tooth morphology to the potential palaeodiets. The analysis is based on three-dimensional (3D) polygonal surface scans, allowing the detailed investigation of morphological features. The results show that primitive equoids possess well-developed cutting and shearing structures, despite being generally referred to as simply bunodont. These structures enable the primitive forms to break down structural plant parts more efficiently than for example Phenacodus (‘condylarth’ outgroup), showing simple rounded cusps, and therefore representing a more primitive type of bunodont dentition. It is general consensus that the diet of the more derived early equoids shifts to a higher percentage of tough plant parts and they adopt different strategies to efficiently comminute those parts. Equids emphasise cutting and shearing both buccally and lingually, trending towards a one-phase power stroke, a pattern resembling that of modern hypsodont Equidae. Our results suggest that the derived brachydont equids specialised to consume leaves rather than grasses. In comparison, derived palaeotheriids mainly emphasise shearing and cutting function buccally and a distinct grinding function in a two-phase power stroke. The combination of different functions suggest a broader diet different from only leaves, likely including twigs or hard fruits.

Fieldwork conducted in the Wasatch Formation in and around Fossil Butte has yielded a diverse assemblage of early Eocene vertebrates. Fossil vertebrates are distributed through three discrete stratigraphic intervals within the uppermost 180 m of the main body of the Wasatch Formation underlying the Green River Formation. These assemblages were derived primarily from fluvial overbank mudstone units overprinted with variably well-developed paleosols. The lowest (20 m) and highest (60 m) sections are characterized by less mature and more hydromorphic paleosols, whereas the middle section (100 m) is typified by more mature paleosols and more abundant channel sandstones.The combined assemblages contain at least 46 species of mammals. Faunal characteristics include high abundances of equid perissodactyls and a relatively high abundance and diversity of notharctines primates, an apparent absence of omomyid primates, relatively high rodent diversity, and relatively diverse and abundant artiodactyls. One new genus (Eoictopsnew genus) and three new species (Eoictops novacekinew species,Palaeosinopa lacusnew species, and ?Notoparamys blochinew species) are included in the Fossil Butte assemblage. Also recorded are late occurrences of two hyopsodontid condylarths and an early occurrence of a rare phenacodontid condylarth. The relatively high abundances of equids and notharctines suggest that vertebrate samples were derived from relatively open paleohabitats that included forested areas along water courses.All three assemblages contain characteristic Lysitean (Wasatchian biochron Wa-6) elements, but the occurrence of the palaeotheriid perissodactylLambdotheriumin the uppermost horizon indicates a Lostcabinian (Wa-7) age for at least the top of the Wasatch Formation. The overlying predominantly fish-bearing Fossil Butte Member of the Green River Formation also containsLambdotheriumand is therefore Wa-7 in age as well.

Few areas preserve the Cretaceous–Paleogene (K–Pg) boundary and earliest Paleocene (Puercan) mammalian faunas better than Colorado9s Denver Basin. Research conducted decades ago described a diverse Puercan fauna from the Denver Basin, but many would agree that the best-known fauna in the basin—the Littleton fauna—probably represents a late early-Puercan (i.e., late Pu1) assemblage. Renewed collecting of fossil mammals from Denver Museum of Nature & Science (DMNH) loc. 2560 in the Denver Formation on the eastern side of the Denver Basin—approximately nine meters stratigraphically above the K–Pg boundary—has produced a Puercan faunal assemblage containing isolated teeth of at least nine species of fossil mammal. Based upon its faunal composition, low diversity, absence of taxa characteristic of middle and late Puercan faunal assemblages, and close stratigraphic proximity to the K–Pg boundary, the fauna from DMNH loc. 2560 probably represents a Puercan fauna that is earlier than the Littleton fauna. It is most similar to early Puercan (Pu1) faunas in Wyoming and northeast Montana. We document the occurrence of three species of the multituberculate Mesodma ( M. ambigua, M. formosa , and M. hensleighi ), the cimolodont Cimexomys minor , the marsupial Thylacodon montanensis , and four species of archaic ungulate (or ‘condylarth’), including Protungulatum donnae , Oxyprimus sp., Baioconodon nordicus , and Maiorana sp. The presence of P. donnae defines the onset of the Puercan age, while Oxyprimus, Maiorana , and B. nordicus are restricted elsewhere to Pu1. C. minor is known from Lancian and early Puercan (Pu1) localities. The faunal assemblage from DMNH loc. 2560 indicates that the characteristic, low-diversity Pu1 fauna found in Montana and Wyoming extended as far south as Colorado. Additionally, we report the occurrence of the ‘condylarth’ Ampliconus browni from the South Table Mountain locality (DHMH loc. 2814) near Golden, Colorado. Its presence corroborates research by others that this locality is probably temporally correlative to the late early-Puercan (late Pu1) Alexander locality south of Denver, Colorado (UCM loc. 77267 [UCM = University of Colorado Museum of Natural History]). Our research provides a more complete picture of early Puercan mammalian diversity in the Denver Basin and a means to temporally correlate early Puercan faunas from Montana to Colorado.

Mammals underwent a profound diversification after the end-Cretaceous mass extinction, with placentals rapidly expanding in body size and diversity to fill new niches vacated by dinosaurs. Little is known, however, about the brains and senses of these earliest placentals, and how neurosensory features may have promoted their survival and diversification. We here use computed tomography (CT) to describe the brain, inner ear, sinuses, and endocranial nerves and vessels of Carsioptychus coarctatus, a periptychid "condylarth" that was among the first placentals to blossom during the few million years after the extinction, in the Paleocene. Carsioptychus has a generally primitive brain and inner ear that is similar to the inferred ancestral eutherian/placental condition. Notable "primitive" features include the large, anteriorly expanded, and conjoined olfactory bulbs, proportionally small neocortex, lissencephalic cerebrum, and large hindbrain compared to the cerebrum. An encephalization quotient (EQ) cannot be confidently calculated because of specimen crushing but was likely very small, and comparisons with other extinct placentals reveal that many Paleocene "archaic" mammals had EQ values below the hallmark threshold of modern placentals but within the zone of nonmammalian cynodonts, indicative of small brains and low intelligence. Carsioptychus did, however, have a "conventional" hearing range for a placental, but was not particularly agile, with semicircular canal dimensions similar to modern pigs. This information fleshes out the biology of a keystone Paleocene "archaic" placental, but more comparative work is needed to test hypotheses of how neurosensory evolution was related to the placental radiation. Anat Rec, 302:306-324, 2019. © 2018 Wiley Periodicals, Inc.

Procreodi is an order of Paleocene and Eocene mammals thought to lie at the base of the radiation of the paraphyletic ‘condylarths.’ Taxa within the order have been linked to the origins of other c...

Isolated cheek teeth from the late Puercan (early Paleocene) Split Lip Flats local fauna, from the head of Willow Wash, Nacimiento Formation, San Juan Basin, represent a new genus and species of hyopsodontid “condylarth”, Chacomylus sladei. The teeth are small, bunodont, and are remarkable for the enlargement of the protocone, pronounced exodaenodonty, and high degree of attritional wear caused by transverse shearing or grinding. Although C. sladei bears a superficial resemblance to the apheliscine apheliscid Gingerichia, a preliminary phylogenetic analysis confirms that it is a hyopsodontid, closely related to the Puercan hyopsodontids Valenia wilsoni and Litomylus orthronepius.

Neither pre-Cenozoic crown eutherian mammals (placentals) nor archaic ungulates (“condylarths”) are known with certainty based on the fossil record. Herein we report a new species of the Paleocene archaic ungulate (“condylarth”) Protungulatum from undisputed Late Cretaceous aged rocks in Montana USA based on an isolated last upper premolar, indicating rare representatives of these common early Tertiary mammals appeared in North America a minimum of 300 k years before the extinction of non-avian dinosaurs. The other 1200 mammal specimens from the locality are characteristic Late Cretaceous taxa. This discovery overturns the current hypothesis that archaic ungulates did not appear in North America until after the Cretaceous/Tertiary (K/T) boundary and also suggests that other reports of North American Late Cretaceous archaic ungulates may be correct. Recent studies, including ours, cannot determine whether Protungulatum does or does not belong to the crown clade Placentalia.

The Paleocene locality of Punta Peligro (Hansen Member of the Salamanca Formation) in Argentina has yielded not only 'condylarths' but also an extraordinary assemblage of therian mammals derived from Laurasian immi- grants and non-therian mammals, relicts of the Mesozoic Gondwanan radiation. The materials, a left jaw fragment with the talonid of the second molar and the third molar, and an isolated upper molar, allow the revalidation of Raulvaccia peligrensis considered previously as a junior synonym of Escribania chubutensis. In addition to other characters, Raul- vaccia strongly differs from E. chubutensis in its lesser size, the development of the m3 talonid, the presence of a hypocristid, and a postcristid. Originally Raulvaccia and Escribania were considered as Mioclaenidae, Kollpaniinae, together with other ungulates from the Santa Lucia Formation, from the early Paleocene locality of Tiupampa in Bolivia. In contrast to the Tiupampan 'condylarths,' Raulvaccia shares derived characters with E. chubutensis, particularly in the upper molars, such as a strong parastyle and the presence of hypocone located close to, but well differentiated from the protocone. These characters support a previous hypothesis which argues for the removal of the Peligran 'condylarths' from the more primitive Kollpaniinae, and sustains its relationship to the exclusively South American Didolodontidae. The revalidation of Raulvaccia peligrensis shows that the diversity of placental mammals during the earliest known Paleocene in Patagonia was greater than previously thought, and supports for the early differentiation of the Didolo- dontidae.

The Punta Peligro fauna includes some of the oldest Cenozoic South American mammals, and the oldest ones for Patagonia. In addition to frogs, turtles, and crocodiles, an unusual mammalian assemblage is formed by a mixture of Mesozoic lineages of Gondwanan origin and therians (eutherians and metatherians) derived from Laurasian immigrants. This paper describes new remains of the Didolodontidae ‘condylarth’ genusEscribaniaBonaparte, Van Valen & Kramarz, 1993. The new material includes an isolated right lower third molar with talonid morphology different from the homologous structure of the type speciesEscribania chubutensisBonaparte, Van Valen & Kramarz, 1993, justifying the recognition of a new species. The derived nature of the didolodontid ‘condylarths’ from the Banco Negro Inferior, their differences with the Mioclaenidae Kollpaniinae from the early Paleocene of Tiupampa, and the record ofbona fidelitoptherns in the Banco Negro Inferior (BNI) suggest an early radiation of the panameriungulates.

Evolutionary stasis has often been explained by stabilizing selection, intrinsic constraints, or, more recently, by spatially patterned population dynamics. To distinguish which of these mechanisms explains a given case of stasis in the fossil record, stasis must first be rigorously documented in a high-resolution stratigraphic time series of fossil specimens. Furthermore, past studies of evolutionary mode in fossil mammalian lineages have often been limited to univariate traits (e.g., molar crown area). It is reasonable to assume that tooth shape, a multivariate trait, reflects important additional aspects of tooth form and function. Here we present the results of a geometric morphometric analysis of the lower dentition of the Paleocene-Eocene condylarth speciesEctocion osbornianuscollected from the Bighorn and Clarks Fork Basins of northwestern Wyoming. Tooth margin shape, cusp configuration, and shearing crest shape were digitized for the last lower premolar, p4, and for two lower molars, m1 and m3. Multivariate statistical tests of evolutionary mode were used to analyze the change in shape variance over time in addition to the magnitude and direction of shape change. Test results characterize the shape time series as consisting of counteracting changes with less change than expected under a random walk (i.e., stasis). The temporal structure of shape variance implies that the sampledE. osbornianusmost likely represent a single population, which is not concordant with the population dynamic mechanism of stasis. Stabilizing selection and/or intrinsic constraints remain as the mechanisms that could explain stasis in the lower dental shape ofE. osbornianusdespite the variable environmental conditions of the Paleocene–Eocene.

A recent Internet search revealed the homonymy of the generic name Paulacoutoia, which was proposed by Cifelli (1983:3) for a South American didolodontid ‘condylarth’ of the Itaboraian South American Land Mammal Age (late Paleocene–early Eocene), whose type species P. protocenica was previously assigned by Paula Couto (1952) to Ernestokokenia Ameghino, 1901. This generic separation was confirmed by later studies (e.g., Cifelli, 1993; Gelfo, 2006, 2010; Gelfo and Sige,´ 2011). Notwithstanding, the name Paulacoutoia was erected previously by Purper (1979) for a Miocene ostracod (Crustacea) genus (see Thompson Reuters, 2008; Global Name Index, 2010). Currently, Paulacoutoia is a junior objective synonym of the ostracod genus Cyprideis Jones, 1857 (see Munoz-Torres et al., ˜ 1998; Whatley et al., 1998). Because the generic name Paulacoutoia is preoccupied, according to Articles 52, 53, and 60 of the current edition of the International Code of Zoological Nomenclature (1999), the name of the extinct didolodontid becomes a junior homonym, and it must be rejected and replaced. Fil: Cifelli, Richard L.. Sam Noble Museum; Estados Unidos Fil: Ortiz Jaureguizar, Edgardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We report here the discovery of the first well identified “condylarths” from Africa, from the phosphatic beds of Ouled Abdoun Basin, Morocco, of probable early Ypresian age, which have also yielded the oldest known proboscidean. Abdounodus hamdii n. gen., n. sp. and Ocepeia daouiensis, gen. et sp. nov., show closest relationships with Mioclaenidae and Phenacodonta respectively. Both taxa also have resemblances with South American primitive ungulates, especially Abdounodus which resembles kollpaniine mioclaenids in several derived features, mostly related to a similar crushing specialization. However divergent specializations in Abdounodus and kollpaniines strongly suggest their parallelisms, in accordance with their age disparity. Some features of Abdounodus appear to be even original with respect to known mioclaenids. Though Ocepeia shares peculiar derived features with phenacodontids, it is strikingly specialized in its secondarily simplified p4, indicating sister-taxa relationships within Taxe...

The Chappo Type Locality in southwestern Wyoming has produced an extensive Tiffanian (late Paleocene) mammalian fauna. Thirty-three genera and 39 species of mammals are represented at Chappo, including three newly recognized taxa, a ?lipotyphlan insectivore Palaeoryctes cruoris, sp. no v., an erinaceomorph insectivore Cedrocherus aceratus, sp. nov., and an arctocyonid condylarth Lambertocyon gingerichi, sp. nov. Comparison with other middle and late Tiffanian localities suggests that Chappo represents a transitional Ti3–Ti4 fauna. The presence of mature paleosol horizons at Chappo indicates deposition on a distal floodplain. Faunal analysis (including body size distribution, trophic structure, and taxonomic diversity) indicates that the Chappo sample consists of small- to medium-sized mammals dominated by omnivores and insectivores. The relatively low frequency of frugivores indicates less forested, more open conditions. Diversity indices suggest that middle Tiffanian mammalian diversity was only...

The modern effect of climate on plants and animals is well documented. Some have cautioned against assigning climate a direct role in Cenozoic land mammal faunal changes. We illustrate 3 episodes of significant mammalian reorganization in the Eocene of North America that are considered direct responses to dramatic climatic events. The first episode occurred during the Paleocene–Eocene Thermal Maximum (PETM), beginning the Eocene (55.8 Ma), and earliest Wasatchian North American Land Mammal Age (NALMA). The PETM documents a short (Hyopsodus. Rather than being “optimum,” the EECO began the greatest episode of faunal turnover of the first 15 m.y. of the Cenozoic.

The unexpected discovery of mammals such as the earliest known proboscidean Phosphatherium escuilliei in the Ouled Abdoun phosphate Basin (Morocco), which is otherwise renowned for its very rich marine vertebrate fauna, has opened major new perspectives on the early African placental fauna. It was the impetus for several field parties by us between 1997 and 2001 which has allowed this survey of the geological, stratigraphic and paleontological context of Phosphatherium localities. This is the first important paleontological field work dealing with higher vertebrates in the Ouled Abdoun Basin since the work of C. Arambourg. Most of the material of Phosphatherium and other Ouled Abdoun mammals was found by local people searching for fossils for dealing, in an area where the economy is widely dominated by the mining development, in addition to more traditional but very poor agricultural resources. All Phosphatherium remains were found in the northeasternmost quarries of the Ouled Abdoun Basin, from a restricted quarrying area called Grand Daoui (fig. 3). In all Grand Daoui recognized localities (8), the mammals come from the lowermost Eocene level. The stratigraphically re-situated mam-malian material was found in a bone-bed of the level called "Intercalaire Couches II/I" which is dated as early(iest) Ypresian on the basis of its relative stratigraphic position and its selachian fauna. At present, the occurrence of several mammal horizons in the "Intercalaire Couches II/I" (and Couche I ?) cannot be excluded, but their age difference seems not significant according to both the associated selachian taxa and the mammalian material, in present data. The bone-bed is very rich in macro-vertebrates. It includes especially large teeth of the shark Otodus obliquus which are the subject of very active research for dealing, and which explains the recent discovery of mammals such as Phosphatherium., Nos recherches de terrain permettent de restituer le contexte géologique et stratigraphique d'origine des loca-lités à Phosphatherium escuilliei (Proboscidea) du bassin à phosphates des Ouled Abdoun au Maroc. Le matériel de P. escuilliei et de plusieurs autres mammifères provient des exploitations de Grand Daoui (NE du bassin). Nos observations montrent que leur niveau d'origine est un bone-bed situé à la base de l'Intercalaire Couche II/I daté classiquement de l'Yprésien inférieur. Ces niveaux du début de l'Eocène marquent l'installation d'une nouvelle mégaséquence dans la série phosphatée qui a partiellement remanié les niveaux sous-jacents du Thanétien. Cela explique la présence de séla-ciens du Thanétien dans la gangue de P. escuilliei et sa datation initiale du Paléocène. L'étude des sélaciens associés au nouveau matériel mammalien récolté confirme l'âge éocène basal de P. escuilliei avec l'identification de plusieurs espè-ces de l'Yprésien inférieur. La présence exceptionnelle de mammifères dans les Ouled Abdoun dénote d'une tapho-nomie particulière des restes continentaux dans les dépôts phosphatés. Ceux-ci ont été transportés dans le bassin depuis l'arrière-pays continental proche dans des conditions de faible énergie hydrodynamique, probablement sous forme de cadavres flottés. Au total le matériel récolté dans les carrières de Grand Daoui documente 7 espèces de mammifères dont un créodonte, deux proboscidiens, deux « condylarthres », et deux espèces indéterminées décrites ici. L'une est un des plus anciens hyracoïdes signalés. P. escuilliei est très largement prédominant parmi ces mammifères. La faune de vertébrés qui leur est associée comprend des restes d'oiseaux signalés pour la première fois dans les bassins à phosphates d'Afrique. Ce sont les plus anciens oiseaux connus en Afrique et parmi les premiers représentants des groupes marins modernes.

Meniscotherium is a relatively small condylarth that is considered unusual in having a specialized dentition consisting of molarized posterior premolars and selenodont-lophodont molars (Figure 1). It unites this specialized dentition with a very generalized skeleton (Williamson and Lucas, 1992). Two species of Meniscotherium are recognized, M. chamense and M. tapiacitum (Williamson, 1989; Williamson and Lucas, 1992). M. chamense from the San Jose Formation of the San Juan Basin, New Mexico probably was about 58 cm in length and ranged from between 4.88–9.76 kg in body weight. M. tapiacitum was approximately 70% the size of San Juan Basin M. chamense in linear dimensions (about 41cm in length) and probably weighed between 1.7 and 3.3 kg (Williamson and Lucas, 1992). The apparently erratic occurrence of Meniscotherium has long been noted (Van Houten, 1945) and the presence/absence of Meniscotherium in the San Jose Formation was believed to be controlled by the depositional environment as reflected in particular facies association (Granger, 1914; Simpson, 1948b; Gazin, 1952, Gazin, 1962, Gazin, 1965a, Gazin, 1965b). Meniscotherium is often found in large concentrations in the San Jose Formation, New Mexico and as a result, it is one of the best known early Paleogene condylarths.

The first known members of the order Artiodactyla appeared suddenly throughout the Holarctic region at the beginning of the Eocene. They are characterized by distinctive cursorial skeletal specializations. Owing to their abrupt appearance and the lack of transitional forms, the origin of the order is problematic. Descent from a "condylarth," specifically the arctocyonid Chriacus, has been suggested based on dental resemblances, but until now postcranial anatomy seemed to preclude close relationship between Arctocyonidae and Artiodactyla. A middle Paleocene specimen of a small arctocyonid (?Chriacus) reported here is much more similar to the oldest artiodactyl, Diacodexis, in the derived condition of the hindlimb, reviving the possibility that Artiodactyla evolved from an arctocyonid.

Cetaceans evolved from mesonychid condylarths, a cat-like, hooved carnivore, during the mammalian radiation, an explosive period of species development (Barnes et al., 1985; Lipps and Mitchell, 1976). In the Eocene, an amphibious condylarth entered the shallows of the warm, teeming Tethys Sea and stayed. This ancestral condylarth was equipped with a conventional land mammal ear. In the intervening 50 to 60 million years, auditory evolution paralleled that of the rest of the creature and the ancestral terrestrial ear underwent extraordinary modifications. As cetaceans developed into full, obligate aquatic mammals, unable to move, reproduce, or feed on land, their ears changed into highly effective transducers of water-borne sound. In fact, modern cetacean auditory systems are sufficiently specialized that they may no longer be able to encode air-borne signals.

Mammal faunas from five outcrop sections in the Tienen Formation (Dormaal, Orp-le-Grand, Hoegaarden, Erqueiinnes, and Levai), representing the Paleocene-Eocene transition in Belgium, have been analysed (Smith 1999). The study of the Dormaai fauna, the nchest and most diversified among these, permitted to speciQ reference level MW of the mammalian biochronological scale for the European Paleogene (SchmidtKittler 1987). This fauna is characterised by the first occurrence of modem mammal groups among which the most typical species are: Teilhardina belgica (euprimate), Diacodexis gigasei (artiodactyl), Microparamys nanus (rodent), Miacis latouri (miacid carnivore), Prototomus n. sp. D, and Afia n. sp. E (hyaenodontid creodonts). These CO-occur with species of persisting primitive groups, such as Paschatherium dolloi (hyopsodontid condylarth), Landenodon woutersi (arctocyonid), Platychoerops georgei (plesiadapid primate), Palaeosinopa russelli (pantolestid), and Apatemys teilhardi (apatotherid). Recent excavations in the stratotype of the Dormaal Sand Member (see Smith & Smith 1996) have led to a better understanding of the biodiversity and the palaeobiogeographical affinities of the mammal fauna at the Paleocene/Eocene boundary in Belgium. About 14,000 teeth have been identified, per ta i~ng to fifty-five taxa, including 37 genera, 20 families, and 13 orders. About 99% of the specimens, belonging to fifty taxa, come from Dormaal. The palaeoecological analysis of the Dormaai m m mal fauna, microfaunas and floras (Steurbaut et al. 1999) indicates a warm and humid ciimate in a wooded area, dominated by a large nver system. This environment was rich in insects as showed by the numerous forest mammal species with insectivomus and arboreai tendencies. Of the 37 mamrnal genera discovered in Belgium, 25 are also present in the other MP7 localities of North Europe. Only 12 are known from southem Europe. Paradoxically, at least 22 genera are comrnon with North Arnerica. The Asiatic faunas are not well known but at least five genera are common with East Asia. The close palaeobiogeographical affinities of the marnmals within the Anglo-FrancoBelgian Basin suggest that there were faunal exchanges throughout that area, resulting from the existence of land bridges between England and the rest of NW Europe. Our observations also confirm Marandat's (1997) hypothesis that two geographically or climatologically isolated provinces existed in Europe at the PaleoceneEocene boundary: The Anglo-Franco-Belgian Basin in the north and the peri-mesogean basins in the south. The strong affinities between the North European and North Amencan faunas aiso c o n f m the hypothesis that a land bridge via Greenland existed between these areas (Kurten 1966). The low afinities between the European and Asian faunas suggest that there was no direct land connection between these continents and that the few cornrnon genera should have crossed the Bering Strait, North Arnenca, and Greenland. A few genera, persisting

Palaeodiversity and relationships of all groups of Australian mammals are reviewed. The fossil record spanning this time is of variable quality. 'Dark Ages' about which nothing is known in terms of Australian mammal evolution include the late Triassic to late Jurassic, late Cretaceous to late Paleocene and middle Eocene to middle Oligocene. Very little is known about the early Cretaceous and late Miocene. The late Oligocene to middle Miocene record documents the highest levels of biodiversity known for the continent, comparable to that which characterises the lowland rainforests of Borneo and Brazil. Order Monotremata spans at least the last 110 million years and includes four families. The enigmatic Ausktribosphenos from 115 million-year-old sediments in Victoria may represent an archaic monotreme, specialised peramurid or previously undocumented order of mammals but is unlikely to represent a placental as suggested in the initial description. Order Microbiotheria is represented in the early Eocene (~55 mya) by two genera similar in morphology to early Eocene taxa from Argentina. Order Peramelemorphia spans the early Eocene to Holocene and includes at least five families. Order Dasyuromorphia spans at least the late Oligocene to Holocene and includes at least three families. Other dasyuromorphian-like marsupials are indeterminate in terms of family-level affinities. Order Notoryctemorphia spans the early Miocene to Holocene with one family. Order Yalkaparidontia spans the late Oligocene to middle Miocene with one genus. Order Diprotodontia spans the late Oligocene to Holocene, represented throughout by three major groups: Phalangerida (eight families), Vombatomorphia (seven families) and Macropodoidea (at least three families). A possible placental condylarth (Tingamarra) has been recorded from the early Eocene. An archaeonycteridid bat (Australonycteris) is known from the early Eocene. Among bats, the late Oligocene to middle Miocene is dominated by rhinolophoids, many of which have European, Asian and African affinities. Mystacinids, megadermatids, hipposiderids and molossids are well-represented in the Oligocene to Miocene deposits. Vespertilionids are uncommon in the Oligocene to Miocene but become more diverse in the Pliocene to Holocene. Emballonurids and rhinolophids appear for the first time in the Plio-Pleistocene. Pteropodids are unknown prior to the Holocene. Murids span the early Pliocene to Holocene. In the oldest assemblage at Riversleigh, one undescribed lineage resembles archaic forms otherwise only known from the fossil records of Africa and Eurasia.

A comparison of the morphology and wear of the chewing surfaces among archaic Paleocene herbivores suggests that a compressive type of interaction between opposing chewing surfaces was becoming a dominant mode of chewing, unlike the translative (grinding or shearing) mechanisms common in Eocene and later herbivores. In part, the evidence for this conclusion is that most of the wear occurs on horizontal surfaces centered at the tips of the cusps and pronounced unidirectional striae tend to be lacking in these areas. In the diverse early Paleocene periptychid condylarths, multidirectional striae occur on the wear surfaces and there is a measured loss of directionality of the crests and enamel edges from the condition in the earliest condylarth, the Late Cretaceous Protungulatum. The patterns are even more random in the later Paleocene phenacodontids, suggesting that this was a broad characteristic for the larger Paleocene condylarths.Efficiency (that is, the volume of food processed per stroke) in compressional chewing systems is theoretically proportional to the area of the opposing surfaces, with large, relatively flat surfaces optimal, whereas in translational systems linear structures are dominant. The reduction in alignment of striae and in linearity of topographic features of the chewing surfaces is consistent with an increasing dominance of compressive chewing from the condition characteristic of palaeoryctid and probably other Cretaceous insectivores in which both compression and shearing occurred between opposing surfaces. The change was brought about by expanding surface areas at the expense of edge length, which was accomplished independently and differently by the phenacodontids and the periptychids, one by increasing both the cylindrical shape and size of the cusps, the other by increasing the cylindrical shape and converging the cusps. The retention of large paraconules and metaconules in the upper molars, cusps essentially lost in the periptychids, preadapted the phenacodontid pattern for later development of the oblique lophodonty and translatory chewing component characteristic of perissodactyls (horses and their relatives), the dominant herbivores of the Eocene.

A new specimen of arctocyonid condylarth from the early Eocene (Clarkforkian) of Wyoming is represented by the anterior part of the snout and lower jaws. Molar teeth are lacking, but the size and spacing of the premolars most closely resemble those in the early Eocene arctocyonid Thryptacodon antiquus ; hence, the specimen is best referred to that species. The new specimen is most remarkable in preserving a well-developed tooth comb that closely resembles the tooth comb of Madagascan lemurs. Dental homologies of the teeth in the comb are different in cf. Thryptacodon and lemurs, and the tooth comb in the two is clearly a result of evolutionary convergence. Considering the whole dentition, a close modern analogue for Thryptacodon is the procyonid Nasua , which also has an incipient tooth comb. Nasua , like lemurs, uses its tooth comb for both food gathering and grooming.

The late Miocene La Venta fauna of the upper Magdalena valley, Colombia, includes remains of a giant condylarth, here described as Megadolodus molariformis n.g. n.sp., and a primitive notoungulate allied to the isotemnids. Both forms represent late survival of early Tertiary mammalian types.

The purpose of this note is to give some evidence on the group from which artiodactyls originated. It is less complete than I would have liked, but several other people are working on the same subject with other kinds of evidence and have seen a draft of this note, and publication seems the best way to avoid awkwardness. The earliest known artiodactyls are distinguished from condylarths especially by the structure of the tarsus. Schaeffer (1947, 1948) and Guthrie (1968) have described this, and Schaeffer gave a good account of its probable evolution from the condylarth condition. McKenna (1960) found an intermediate situation in one aspect of an earliest Eocene astragalus which was found isolated and therefore cannot be surely identified. Guthrie (1968) did not consider this specimen. Paleocene members of the Hyopsodontidae have usually been regarded as ancestral to the artiodactyls, and this view has had almost complete acceptance since Simpson (1937). Jepsen (1930) had provisionally regarded the late Paleocene genus Phenacodaptes as an artiodactyl, but Simpson transferred it to the Hyopsodontidae (cf. also Van Valen, 1967). Cope (1882a, p. 188; 1882b) had placed Mioclaenus as the basal artiodactyl. This genus is now regarded as a hyopsodontid, but the species from which Cope made his conclusion belongs to Diacodexis, the stem artiodactyl. Schlosser (1923) had included the hyopsodontid Haplomylus in the stem artiodactyl family Dichobunidae and Gregory (1910) had advocated an origin from Paleocene hyopsodontids. One of the two genera Gregory mentioned, however, was Protogonodon, which I regard as a synonym of Loxolophus and which is now placed in the Arctocyonidae. Earle (1893; Osborn and Earle, 1895) had also suggested Protogonodon as an artiodactyl ancestor, but only for the selenodont groups. And Mathew (1909, p. 845) thought artiodactyls probably came from unknown creodonts similar to the Mesonychidae. Other work has shown the Mesonychidae to be a derivative of early arctocyonids. Louis (1963) thought that the Paleocene or earliest Eocene genus Microhyus was an artiodactyl. As noted by Teilhard (1927), Microhyus is similar to Orthaspidotherium, a condylarth probably referable to the Meniscotheriidae. Like other meniscotheriids, Microhyus does not seem especially similar to Diacodexis, the most primitive known artiodactyl, although it is convergent to some more advanced genera. Diacodexis has not yet even evolved a hypocone. Pearson (1927) compared the basicranium of Pleuraspidotherium favorably with that of early artiodactyls and Russell (1964) also thought a special relationship was possible, but the similarities seem to be in primitive characters, as Russell thought for the similarities of Arctocyonides and Bunophorus. Other early views, such as Cope's influential derivation (1883, 1885, 1887) of artiodactyls from the insectivore Pantolestes,' seem implausible now. My view most closely approximates that of Earle (1893).

SUMMARY. 1 A survey is made of the milk-molars of Perissodactyla and Condylarthra with a view to determining the evolutionary trends. 2 Molarization of the milk-molars takes place in a variety of ways, which may be grouped into three main types: (a) the condylarthran type, found also in Plagiolophus, (b) the type found in the Equidae and Brontotheriidae, and (c) that found in the Tapiroidea and Rhinocerotoidea. Each of these types has a characteristic order of development of the cusps. The condylarthran type is considered to be the most primitive. 3 From a study of the wear of the teeth, it is concluded that the occlusal movement in all Perissodactyla is transverse (ectal). The characteristic features of occlusion in the various families are discussed. 4 During molarization the talonid becomes intercalated between two trigonids, the intercalation taking place at a relatively late stage in type (a), earliest in type (b) and at an intermediate stage in type (c). The buccal parts of the trigonid and talonid become functional before the lingual parts. 5 The Palaeotheriidae (excluding Pachynolophus and Propachynolophus) are regarded as a distinct family that retains condylarth features of the milk dentition to a late date, and cannot be derived from Hyracotherium. With the exception of Plagiolophus, they show in their milk-molars transitional stages leading to the conditions found in other perissodactyls. 6 The hypothesis is put forward that the order of development of the cusps depends upon their different sensitivities to the graded morphogenetic conditions in the developing jaw. Correlated evolution of the upper and lower teeth suggests that occlusion has a morphogenetic basis which affects both jaws. 7 The concepts of homology due to descent from a common ancestral structure, homology due to parallel evolution, and serial homology are considered to be closely related and not sharply separable in practice.

Variation in the mammalian dentition is highly informative of adaptations and evolutionary relationships, and consequently has been the focus of considerable research. Much of the current research exploring the genetic underpinnings of dental variation can trace its roots to Olson and Miller’s 1958 book Morphological Integration. These authors explored patterns of correlation in the post-canine dentitions of the owl monkey and Hyopsodus, an extinct condylarth from the Eocene. Their results were difficult to interpret, as was even noted by the authors, due to a lack of genetic information through which to view the patterns of correlation. Following in the spirit of Olson and Miller’s research, we present a quantitative genetic analysis of dental variation in a pedigreed population of baboons. We identify patterns of genetic correlations that provide insight to the genetic architecture of the baboon dentition. This genetic architecture indicates the presence of at least three modules: an incisor module that is genetically independent of the post-canine dentition, and a premolar module that demonstrates incomplete pleiotropy with the molar module. We then compare this matrix of genetic correlations to matrices of phenotypic correlations between the same measurements made on museum specimens of another baboon subspecies and the Southeast Asian colobine Presbytis. We observe moderate significant correlations between the matrices from these three primate taxa. From these observations we infer similarity in modularity and hypothesize a common pattern of genetic integration across the dental arcade in the Cercopithecoidea.

Previous interpretations of early horse brains were based on an incorrectly identified fossil endocast, now believed to be from a condylarth. Newly prepared endocasts of Hyracotherium, the oldest horse and one of the earliest perissodactyls, reveal a relatively larger brain, with a more expanded neocortex, than existed in the condylarth ancestors of perissodactyls. Fifty million years ago, horse brains had suprasylvian, ectolateral, and lateral sulci, but the frontal lobe was undeveloped.

Fossil vertebrate remains were found on the northwest limb of the San Jose anticline south of the Rio Tetuan and approximately 10 kilometers northeast of Chaparral, Tolima, in the upper Magdalena region, Colombia. They were discovered in a thin lense of bone breccia within a blue-gray clay member (La Cira zone) of the Gualanday (Brazalosa) series. The type La Cira from the middle Magdalena was called upper Oligocene by A. A. Olsson as based on a fresh-water invertebrate fauna. The mammal remains from Chaparral indicate a relationship close to the Deseado lower Oligocene of Argentina. Tentative faunal list: Chelonian, crocodilian, ground-sloth, toxodont (? Proadinotherium), litoptern (? Prothesodon), astrapothere (near Uruguaytherium), and ? condylarth. End_of_Article - Last_Page 131

The mammalian order Condylarthra includes a heterogeneous assemblage of smallto medium-sized archaic omnivores and herbivores. Most families in the order flourished in the Paleocene and became extinct early in the Eocene. A few lineages, however, developed crucial adaptations which led to their emergence as new orders of mammals, one of which was the Perissodactyla. The origin of the Perissodactyla is better documented than that of any other order of mammals and provides an excellent opportunity to study the emergence of a major taxon. Dental evidence indicates that perissodactyls were derived from the condylarth family Phenacodontidae. To view in proper perspective the evolutionary changes which led to the origin of the Perissodactyla, it will be necessary to survey the adaptive radiation of the Phenacodontidae. The oldest true phenacodontid condylarth, Tetraclaenodon, first appears in faunas of middle Paleocene age, and by the beginning of the late Paleocene appears to have radiated into three main groups, represented respectively by Phenacodus, Ectocion, and an as yet unknown proto-perissodactyl. Forms transitional between Tetraclaenodon and Phenacodus (primitive species of Phenacodus), and between Tetraclaenodon and Ectocion (the genus Gidleyina) are known, but no intermediates between Tetraclaenodon and the most primitive known perissodactyl, the early Eocene genus Hyracotherium, have yet been found. However, Tetraclaenodon is the most advanced form which is still unspecialized enough to have given rise to Hyracotherium. (The occurrence of incipient mesostyles in a small number of Tetraclaenodon specimens does not preclude this possibility; the alternative hypothesis, that proto-perissodactyls and Tetraclaenodon were independently derived from a still more primitive common ancestor, requires an additional complicating factor-an independent acquisition of molar hypocones by perissodactyls and phenacodontids.) Thus, in the absence of evidence to the contrary, Tetraclaenodon may be considered directly ancestral to perissodactyls. The major morphological changes involved in the evolution of the Tetraclaenodon stock into Phenacodus, Ectocion, and Hyracotherium, fall into two functional categories, one concerned with mastication and the other with locomotion. MASTICATION Dentition

Periptychus is the archetypal genus of Periptychidae, a clade of prolific Paleocene ‘condylarth’ mammals from North America that were among the first placental mammals to radiate after the end-Cretaceous extinction, remarkable for their distinctive dental anatomy. A comprehensive understanding of the anatomy of Periptychus has been hindered by a lack of cranial and postcranial material and only cursory description of existing material. We comprehensively describe the cranial, dental and postcranial anatomy of Periptychus carinidens based on new fossil material from the early Paleocene (Torrejonian) of New Mexico, USA. The cranial anatomy of Periptychus is broadly concurrent with the inferred plesiomorphic eutherian condition, albeit more robust in overall construction. The rostrum is moderately elongate with no constriction, the facial region is broad, and the braincase is small with a well-exposed mastoid on the posterolateral corner and tall sagittal and nuchal crests. The dentition of Periptychus is characterized by strongly crenulated enamel, enlarged upper and lower premolars with a tall centralised paracone/protoconid. The postcranial skeleton of Periptychus is that of a robust, medium-sized (~20 Kg) stout-limbed animal that was incipiently mediportal and adopted a plantigrade stance. The structure of the fore- and hindlimb of Periptychus corresponds to that of a typically terrestrial mammal, while morphological features of the forelimb such as the low tubercles of the humerus, long and prominent deltopectoral crest, pronounced medial epicondyle, and hemispherical capitulum indicate some scansorial and/or fossorial ability. Most striking is the strongly dorsoplantarly compressed astragalus of Periptychus, which in combination with the distal crus and calcaneal morphology indicates a moderately mobile cruropedal joint. The anatomy of Periptychus is unique and lacks any extant analogue; it combines a basic early placental body plan with numerous unique specializations in its dental, cranial and postcranial anatomy that exemplify the ability of mammals to adapt and evolve following catastrophic environmental upheaval.

The use of high-resolution stratigraphical control in studying the species sequencing patterns of early Eocene mammals has recently been demonstrated by Gingerich et al.1–5. These studies have documented the nature of the tempo and mode of evolution and have stimulated the debate between adherents of phyletic gradualism and punctuated equilibria6. All studies have been largely verticalist (evolutionary) in outlook, equating change within a single basin of deposition with evolution. However, when I applied these techniques to the early Eocene condylarth, Phenacodus, I found a strong lateral (biogeographical and ecological) component influencing the sequencing of species in a single basin. I report here that Phenacodus species are relatively static in size and morphology throughout the local section studied, and two of these show statistically significant discontinuities in temporal range. The clumped re-entry of these species after local disappearance along with the introduction of other new taxa points to ecological control of vertical events within a local section.

Study of the early Cenozoic Hoback formation adds detail to the Laramide history of central western Wyoming. The recently discovered late Torrejonian, Battle Mountain vertebrate faunule, low in the formation, includes a new condylarth, Tetraclaenodon transitus. Additions to the intermediate Dell Creek faunule include a new insectivore, Elpidophorus minutulus. Additional mammals from three other localities are described. In combination with earlier studies, stratigraphic thickness, faunal ages, and faunal levels provide estimates of sedimentation rates and times of orogeny. The Hoback formation is a thick deposit of fluviatile, palludal, and lacustrine materials that accumulated in a subsiding orogenic trough. Sedimentation was very rapid, probably beginning and accelerating in Torrejonian, culminating during late Torrejonian, then decelerating during Tiffanian, Clarkforkian, and Graybullian times prior to a late phase of orogeny. Sediment was derived locally from western, mid-Laramide highlands which began to rise in the early Torrejonian; the uplift culminated between the middle and end of the Torrejonian. Orogenic phases were relatively brief but intense. The area of deposition was much lower, forested, temperate, humid, locally swampy with some lakes, and largely inhabited by a forest-dwelling mammalian fauna. The Cliff Creek thrust which overrode the Hoback formation is internally complex, with distinct fold-fault sets trending parallel with, perpendicular to, or acute to the thrust trace. Fold axes in the overridden western part of the Hoback formation roughly parallel the thrust trace and are concealed locally beneath the thrust. Local deformation severely distorted the conglomeratic materials in the formation.