Showing papers in "Journal of Mammalian Evolution in 2005"

Fossil Evidence and the Origin of Bats

Abstract: The phylogenetic and geographic origins of bats (Chiroptera) remain unknown. The earliest confirmed records of bats date from the early Eocene (approximately 51 Ma) in North America with other early Eocene bat taxa also being represented from Europe, Africa, and Australia. Where known, skeletons of these early taxa indicate that many of the anatomical specializations characteristic of bats had already been achieved by the early Eocene, including forelimb and manus elongation in conjunction with structural changes in the pectoral skeleton, hind limb reorientation, and the presence of rudimentary echolocating abilities. By the middle Eocene, the diversification of bats was well underway with many modern families being represented among fossil forms. A new phylogenetic analysis indicates that several early fossil bats are consecutive sister taxa to the extant crown group (including megabats), and suggests a single origin for the order, at least by the late Paleocene. Although morphological studies have long placed bats in the Grandorder Archonta, (along with primates dermopterans, and tree shrews), recent molecular studies have refuted this hypothesis, instead strongly supporting placement of bats in Laurasiatheria. Primitively, proto-bats were likely insectivorous, under-branch hangers and elementary gliders that exploited terminal branch habitats. Recent work has indicated that a number of other mammalian groups began to exploit similar arboreal, terminal branch habitats in the Paleocene, including multituberculates, eulipotyphlans, dermopterans, and plesiadapiforms. This may offer an ecological explanation for morphological convergences that led to the erroneous inclusion of bats within Archonta: ancestral archontan groups as well as proto-bats apparently were exploiting similar arboreal habitats, which may have led to concurrent development of homoplasic morphological attributes.

The Taxonomic and Evolutionary History of Fossil and Modern Balaenopteroid Mysticetes

Abstract: Balaenopteroids (Balaenopteridae + Eschrichtiidae) are a diverse lineage of living mysticetes, with seven to ten species divided between three genera (Megaptera, Balaenoptera and Eschrichtius). Extant members of the Balaenopteridae (Balaenoptera and Megaptera) are characterized by their engulfment feeding behavior, which is associated with a number of unique cranial, mandibular, and soft anatomical characters. The Eschrichtiidae employ suction feeding, which is associated with arched rostra and short, coarse baleen. The recognition of these and other characters in fossil balaenopteroids, when viewed in a phylogenetic framework, provides a means for assessing the evolutionary history of this clade, including its origin and diversification. The earliest fossil balaenopterids include incomplete crania from the early late Miocene (7‐10 Ma) of the North Pacific Ocean Basin. Our preliminary phylogenetic results indicate that the basal taxon, “Megaptera” miocaena should be reassigned to a new genus based on its possession of primitive and derived characters. The late late Miocene (5‐7 Ma) balaenopterid record, except for Parabalaenoptera baulinensis and Balaenoptera siberi, is largely undescribed and consists of fossil specimens from the North and South Pacific and North Atlantic Ocean basins. The Pliocene record (2‐5 Ma) is very diverse and consists of numerous named, but problematic, taxa from Italy and Belgium, as well as unnamed taxa from the North and South Pacific and eastern North Atlantic Ocean basins. For the most part Pliocene balaenopteroids represent extinct species and genera and reveal a greater degree of morphological diversity than at present. The Pleistocene record is very limited and, unfortunately, fails to document the evolutionary details leading to modern balaenopteroid species diversity. It is evident, however, that most extant species evolved during the Pleistocene. Morphological and molecular based phylogenies support two competing hypotheses concerning relationships within the Balaenopteroidea: (1) balaenopterids and eschrichtiids as sister taxa, and (2) eschrichtiids nested within a paraphyletic Balaenopteridae. The addition of fossil taxa (including a new Pliocene species preserving a mosaic of balaenopterid and eschrichtiid characters) in morphological and “total evidence” analyses, offers the potential to resolve the current controversy concerning the possible paraphyly of Balaenopteridae.

Effects of Quaternary Climatic Change on Speciation in Mammals

Abstract: An ongoing controversy in evolutionary biology is the extent to which climatic changes drive evolutionary processes. On the one hand are “Red Queen” hypotheses, which maintain that climatic change is less important than biotic interactions in causing evolutionary change. On the other hand are “Court Jester” models, which recognize climatic change as a very important stimulus to speciation. The Quaternary Period (the last 1.8 million years), characterized by multiple climatic changes in the form of glacial–interglacial transitions, offers a fertile testing ground for ascertaining whether cyclical climatic changes that operate at the 100,000-year time scale appreciably influence evolutionary patterns in mammals. Despite the increased potential for isolation of populations that should occur with multiple advances and retreats of glaciers and rearrangement of climatic zones, empirical data suggests that speciation rates were neither appreciably elevated for Quaternary mammals, nor strongly correlated with glacial–interglacial transitions. Abundant evidence attests to population-level changes within the Quaternary, but these did not usually lead to the origin of new species. This suggests that if climatic change does influence speciation rates in mammals, it does so over time scales longer than a typical glacial–interglacial cycle.

Organization of the Olfactory and Respiratory Skeleton in the Nose of the Gray Short-Tailed Opossum Monodelphis domestica

Abstract: The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily supports olfactory and respiratory epithelia, the vomeronasal organ, and the nasal gland. This scaffold is built by the median mesethmoid, and the paired vomer and ethmoid bones. The mesethmoid ossifies within the nasal septum cartilage. The bilateral ethmoid segregates respiratory and olfactory regions, and its geometry offers insight into the functional, developmental, and genomic organization of the nose. It forms through partial coalescence of separate elements known as turbinals, which in Monodelphis comprise the maxilloturbinal, nasoturbinal, five endoturbinals, and two ectoturbinals. Geometry of the ethmoid increases respiratory mucosal surface area by a factor of six and olfactory mucosal surface by nearly an order of magnitude. Respiratory epithelium warms and humidifies inspired air, recovers moisture as air is exhaled, and may help mediate brain temperature. In contrast, the olfactory skeleton functions as a series of small funnels that support growth of new olfactory neurons throughout life. Olfactory mucosa lines the mouth of each funnel, forming blind olfactory recesses known as the ethmoid cells, and neuronal axons are funneled from the epithelium through tiny olfactory foramina in the cribriform plate, into close proximity with target glomeruli in the olfactory bulb of the brain where each axon makes its first synapse. The skeleton may thus mediate topological correspondence between odorant receptor areas in the nose with particular glomeruli in the olfactory bulb, enabling growth throughout life of new olfactory neurons and proper targeting by their axons. The geometric arrangement of odorant receptors suggests that a measure of volatility may be a component in the peripheral olfactory code, and that corresponding glomeruli may function in temporal signal processing. Supporting visualizations for this study are available online at www.DigiMorph.org.

Phylogenetic Relationships of Extinct Cetartiodactyls: Results of Simultaneous Analyses of Molecular, Morphological, and Stratigraphic Data

Abstract: Although some recent morphological and molecular studies agree that Cetacea is closely related to Hippopotamidae, there is little consensus on the phylogeny within Cetartiodactyla. We addressed this problem by conducting two analyses: (1) a simultaneous cladistic analysis of intrinsic data (morphology and molecules) and (2) a stratocladistic analysis, which included morphological, molecular, and stratigraphic data. Unlike previous simultaneous analyses, we had the opportunity to include data from the recently described hindlimbs of protocetid and pakicetid cetaceans. Our intrinsic dataset includes 73 taxa scored for 8,229 informative characters, of which 208 are morphological and 8,021 molecular. Both analyses supported the exclusion of Mesonychia from Cetartiodactyla and a close phylogenetic relationship between Hippopotamidae and Cetacea. Many polytomies in the strict consensus of the most parsimonious trees for the intrinsic dataset can be attributed to differing positions for Raoellidae, which in some trees is the sister-group to Cetacea. Pruning Raoellidae and 18 other taxa from all most parsimonious produced a fully resolved agreement subtree, which indicates that the Old World taxa Cebochoerus and Mixtotherium are successive stem taxa to Whippomorpha (i.e., Cetacea + Hippopotamidae). The main result of adding stratigraphic information to the intrinsic dataset was that we found fewer most parsimonious trees, which in most respects were congruent with a subset of the shortest trees for the intrinsic dataset. Our stratocladistic analysis supports species of Diacodexis as the most basal cetartiodactyls, a clade of suiform cetartiodactyls, a monophyletic Tylopoda that includes Protoceratidae, and a monophyletic Carnivora. We were unable to identify any pre-Miocene stem taxa to Hippopotamidae, thus its ghost lineage is still 39 million years long. The relatively low Bremer support for many nodes in our trees indicates that our phylogenetic hypotheses should be subjected to further testing.

Mammalian Faunal Dynamics During the Last 1.8 Million Years of the Cretaceous in Garfield County, Montana

Abstract: This study provides an analysis of biotic change in successive mammalian communities during the last 1.8 million years of the Cretaceous (67.3–65.58 Ma) from the Hell Creek Formation in Garfield County, Montana. Results show changes in relative abundances of species, mean individual body size, and to some extent taxonomic composition through the Hell Creek Formation. These results are interpreted as “normal” mammalian responses to fluctuating temperatures during the latest Cretaceous. By contrast, the extinction of 22–27 mammalian species at or near the Cretaceous-Tertiary (K-T) boundary cannot be explained by the coincident cooling interval alone. At the scale of temporal resolution available, these fossil data are inconsistent with an extended gradual pattern of extinction (linear-response) and are most consistent with either a non-linear response pattern for the K-T extinction, resulting from the accumulated stress of multiple long- and short-term environmental perturbations (e.g., climate change, sea-level regression, volcanism, an extraterrestrial impact), or a single, short-term cause (an extraterrestrial impact).

A New European Marsupial Indicates a Late Cretaceous High-Latitude Transatlantic Dispersal Route

Abstract: The first record of an undoubted opossum-like marsupial from the Mesozoic of Europe indicates an invasion from North America at the end of Late Cretaceous (Maastrichtian). The new 66.1 million-year-old marsupial, Maastrichtidelphys meurismeti n. gen., n. sp., represented by a right upper molar, comes from the type Maastrichtian of The Netherlands. The Maastricht marsupial exhibits affinities with earlier (early Maastrichtian) North American herpetotheriids providing definitive evidence of a high-latitude North Atlantic dispersal route between North America and Europe during the latest Cretaceous. Previously, the first major interchange for marsupials was thought to have occurred nearly 10 million years later in the Eocene. The occurrence of this new marsupial in Europe implies that at some time during the latest Cretaceous, sea level and climatic conditions must have been sufficiently favorable to allow for such a high-latitude dispersal. The fragmentary remains of hadrosaurid and theropod dinosaurs, as well as boid snakes from northwestern Europe which have affinities with North American taxa help substantiate assumptions made by the occurrence of the herpetotheriid marsupial in Maastricht.

New Study on Dental and Skeletal Features of the Cretaceous “Symmetrodontan” Mammal Zhangheotherium

Abstract: A new partial skeleton of the Cretaceous “symmetrodontan” mammal Zhangheotherium quinquecuspedens from the Yixian Formation of Liaoning, China has shed light on the dental and skeletal features of this taxon. The new fossil is a juvenile individual of late growth stage, preserved with interesting features of the premolar replacement. This fossil also provides new information on the vertebral column, the pelvis, the hindlimb and pes. Zhangheotherium has a typical diphyodont replacement of its premolars that is characterized by an alternating pattern (p1 → p3 → p2). This alternating replacement of premolars is a derived condition shared by Dryolestes, Slaughteria, and some basal eutherians, and differs from the plesiomorphic sequential replacement of anterior postcanines in eutricondontans, in most multituberculates and in stem mammaliaforms. The calcaneus and astragalus in the ankle joint of Zhangheotherium lack superposition. This shows that the trechnotherian clade, of which Zhangheotherium is a basal taxon, has retained the primitive condition of mammaliaforms in which the astragalus is in juxtaposition with the calcaneus. Coupled with recent evidence from the earliest metatherians and eutherians, this suggests that the superposition of astragalus and calcaneus evolved in parallel in metatherians and eutherians.

Mammalian Faunal Succession in the Cretaceous of the Kyzylkum Desert

Abstract: Both metatherians and eutherians are known from the Early Cretaceous (Barremian, 125 mya; million years ago) of China, while eutherian-dominated mammalian faunas appeared in Asia at least by the earliest Late Cretaceous (Cenomanian, 95 mya). The approximately 99–93 my old (Cenomanian) Sheikhdzheili l.f. from western Uzbekistan is a small sample of only eutherians, including three zhelestids and a possible zalambdalestoid. The much better-known 90 my old (Turonian) Bissekty l.f. at Dzharakuduk iin central Uzbekistan includes 15 named and unnamed species, based on ongoing analyses. Of these, 12 are eutherians represented by at least the three groups—asioryctitheres, zalambdalestids, and zhelestids—plus an eutherian of uncertain position—Paranyctoides. Zalambdalestids and zhelestids have been argued to be related to the origin of the placental gliriforms (Euarchontoglires) and ferungulates (Laurasiatheria), respectively. Although there are four previously recognized metatherians, we believe three are referable to the deltatheroid Sulestes karakshi and the fourth, Sailestes quadrans, may belong to Paranyctoides. There is one multituberculate and one symmetrodont in the Bissekty l.f. While comparably aged (Turonian) localities in North America have somewhat similar non-therians, they have more metatherians and no eutherians. The next younger localities (early Campanian, ∼80 mya) in North America have both a zhelestid and Paranyctoides, suggesting dispersal of eutherians from Asia. At Dzharakuduk, the approximately 85 my old (late Turonian/Coniacian) Aitym l.f. is much less well known than the Bissekty l.f., but yields nearly identical taxa, with two non-therians, one metatherian, and six eutherians.

Anatomy of the Cranial Endocast of the Bottlenose Dolphin, Tursiops truncatus, Based on HRXCT

Abstract: Endocranial surfaces, volumes, and interconnectivities of extant and fossil odontocetes potentially offer information on the general architecture of the brain and on the structure of the specialized cetacean circulatory system. Although conventional methods for acquiring such data have generally involved invasive preparation of the specimen, particularly in the case of fossils, new tomographic technologies afford nondestructive access to these internal morphologies. In this study we used high-resolution X-ray computed tomography (HRXCT) to scan a skull of the extant Tursiops truncatus (Cetacea: Odontoceti). We processed the data to reveal the cranial endocast and details of internal skeletal architecture (data at www.digimorph.org). Major features that can be discerned include aspects of the specimen's hypertrophied retia mirabilia, the major canals and openings of the cranial cavity, and the relationship of the brain and endocranial circulatory structures to the surrounding skeleton. CT data also provide information on the shape of the brain that may be lost in conventional anatomical preparations, and readily provide volumetric and linear measurements of the endocast and its individual segments. These results demonstrate the utility of HRXCT for interpreting the internal cranial anatomy of both extant and fossil cetaceans.

Locking Yourself Out: Diversity Among Dentally Zalambdodont Therian Mammals

Abstract: We review the evolution of dental zalambdodonty across therian mammals. Among zalambdodonts, there is little or no occlusion between the protocone and talonid basin and one of the central cusps of the upper molars (metacone or paracone) and the talonid basin of the lower molars are lost or reduced. Over two dozen genera of therian mammals show zalambdodont molars, including tenrecids, chrysochlorids, Solenodon, the marsupial mole Notoryctes, the extinct placentals Apternodus, Oligoryctes, Parapternodus, and Koniaryctes, and the extinct marsupials Necrolestes and Yalkaparidon. The chiropteran Harpiocephalus is nearly zalambdodont. Transformation series provided by paleontological or ontogenetic data, plus occlusal relationships, can be used to determine the homology of molar cusps in zalambdodont taxa. Zalambdodont dental specialization does not appear to have led to ecological specialization. With the important exception of golden moles and tenrecs, dentally zalambdodont taxa are less speciose than their nonzalambdodont sister taxa.

On the Occlusal Fit of Tribosphenic Molars: Are We Underestimating Species Diversity in the Mesozoic?

Abstract: The complex occlusal fits between tribosphenic teeth are a rich source of information for taxonomic, phylogenetic, and evolutionary analysis. The degree of fit between upper and lower cheek teeth has been used to refer specimens to species-level taxa, but statistical data on occlusal fit in relation to taxonomic identity have been lacking. We used landmarks on upper and lower first molars of 20 bat populations representing 16 species to assess the degree of occlusal fit (1) between teeth from the same individual; (2) between teeth from different individuals belonging to the same populations; and (3) between teeth belonging to different populations. We found that the fit of teeth belonging to different populations was significantly worse than between those of the same population and that the degree of misfit increased linearly with time since common ancestry, albeit with substantial variance. We used our comparisons to assess the species-level diversity within Batodon, the smallest known placental mammal from the Cretaceous. Our data suggest, with caveats, that instead of belonging to a single species, the specimens assigned to Batodon represent at least two species as different as those belonging to different genera or families of living bats.

Deciduous Dentitions of Eocene Cebochoerid Artiodactyls and Cetartiodactyl Relationships

Abstract: Deciduous lower premolars (milk teeth) of the Eocene artiodactyl family Cebochoeridae possess accessory denticles and are remarkably similar to both deciduous and adult teeth of the cetacean family Basilosauridae, suggesting that morphological characters of juvenile dentitions are important to understanding the phylogenetic origin of whales and morphological transitions in the cetartiodactyl lineage. Incorporation of these new characters into a larger phylogenetic analysis of morphological characters of artiodactyls, mesonychids, and basal and recent whales supports a monophyletic Cetartiodactyla, but does not directly support a whale–hippo relationship. However, the presence of accessory denticles on some artiodactyl dentitions weakens the morphological support for a monophyletic Artiodactyla, suggesting either that whales and cebochoerids may be more closely related than had been thought, or that cebochoerids share a developmental pathway with cetaceans.

Updating and Recoding Enamel Microstructure in Mesozoic Mammals: In Search of Discrete Characters for Phylogenetic Reconstruction

Abstract: The previously unknown enamel microstructure of a variety of Mesozoic and Paleogene mammals ranging from monotremes and docodonts to therians is described and characterized here. The novel information is used to explore the structural diversity of enamel in early mammals and to explore the impact of the new information for systematics. It is presently unclear whether enamel prisms arose several times during mammalian evolution or arose only once with several reversals to prismless structure. At least two undisputed reversions or simplifications are known—in the monotreme clade from Obdurodon to Ornithorhynchus (via Monotrematum?), and (perhaps more than once) within the clade from archaeocete to a variety of odontocete whales. Similarly, both prismatic and nonprismatic enamel is present among docodonts. Seven discrete characters showing enough morphological diversity to be of potential importance in phylogenetic reconstructions may be identified as a more appropriate summary of enamel microstructural diversity among mammaliaforms than the single character “prismatic enamel-present/absent” employed in recent matrices. Inclusion of five of these characters in the matrix of Luo et al. (2002) modifies the original topology by collapsing several nodes involving triconodonts and other nontribosphenic taxa. There is considerable support for prismatic enamel as a synapomorphy of trithelodonts plus Mammaliamorpha, and multituberculates appear to have small or “normal” sized prisms as the ancestral condition, with some (as yet) enigmatic changes to nonprismatic structure in some basal members of the group and the appearance of “gigantoprismatic” structure as an autapomorphic state of less inclusive clades. Other potential qualitative characters and the need for attaining appropriate methods to incorporate quantitative features may be important for future analyses.

A Tachyglossid-Like Humerus from the Early Cretaceous of South-Eastern Australia

Abstract: A partial right humerus has been recovered from the Early Cretaceous (Albian) Eumeralla Formation at Dinosaur Cove in south-eastern Australia. General morphology, size and the presence of a single epicondylar foramen (the entepicondylar) suggest that the bone is from a mammal or an advanced therapsid reptile. The humerus is similar in size, shape and torsion to the equivalent bone of extant and late Neogene echidnas (Tachyglossidae) but, contrary to the situation in extant monotremes, in which the ulna and radius articulate with a single, largely bulbous condyle, it bears a shallow, pulley-shaped (i.e. trochlear-form) ulnar articulation that is confluent ventro-laterally with the bulbous radial condyle. This form of ulnar articulation distinguishes this bone from the humeri of most advanced therapsids and members of several major groups of Mesozoic mammals, which have a condylar ulnar articulation, but parallels the situation found in therian mammals and in some other lineages of Mesozoic mammals. As in extant monotremes the distal humerus is greatly expanded transversely and humeral torsion is strong. Transverse expansion of the distal humerus is evident in the humeri of the fossorial docodont Haldanodon, highly-fossorial talpids and some clearly fossorial dicynodont therapsids, but the fossil shows greatest overall similarity to extant monotremes and it is possible that the peculiar elbow joint of extant monotremes evolved from a condition approximating that of the fossil. On the basis of comparisons with Mesozoic and Cainozoic mammalian taxa in which humeral morphology is known, the Dinosaur Cove humerus is tentatively attributed to a monotreme. However, several apparently primitive features of the bone exclude the animal concerned from the extant families Tachyglossidae and Ornithorhynchidae and suggest that, if it is a monotreme, it is a stem-group monotreme. Whatever, the animal's true affinity, the gross morphology of its humerus indicates considerable capacity for rotation-thrust digging.

Incisor Schmelzmuster Diversity in South America's Oldest Rodent Fauna and Early Caviomorph History

Abstract: Investigation of the enamel microstructure of 20 isolated rodent incisors from the ?Eocene Santa Rosa local fauna (Peru) yielded exclusively schmelzmuster with multiserial Hunter–Schreger bands (HSB). All three subtypes of multiserialHSB with parallel, acute angular, and rectangular interprismatic matrix (IPM) that were previously reported for caviomorph rodents are present. Two lower incisors with rectangular IPM can be attributed to the Octodontoidea, a caviomorph superfamily exhibiting this highly derived enamel type. The plesiomorphic pauciserial condition that characterizes early Paleogene rodents such as North American Ischyromyoidea (including “Franimorpha”) has not been detected. It is therefore probable that the founder populations of South American Caviomorpha already possessed a derived incisor schmelzmuster with multiserial HSB that is shared with African Thryonomyoidea. Because on the North American continent a possible stem-lineage representative of Caviomorpha with multiserial HSB has never been detected, incisor enamel microstructure supports the hypothesis of an African origin of Caviomorpha from a common ancestor shared with Thryonomyoidea.

Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus

Abstract: Desmostylians are enigmatic, extinct, semiaquatic marine mammals that inhabited coastlines of the northern Pacific Rim during the late Oligocene through middle Miocene. Principal components analysis (PCA) of trunk and limb proportions provides a rational multivariate context for separating living semiaquatic mammals on three orthogonal axes: a size axis (PC-I), a degree of aquatic adaptation axis (PC-II), and a forelimb- versus hind-limb-dominated locomotion axis (PC-III). The necessary skeletal measurements are available for Desmostylus hesperus but not for other desmostylians. Among species similar in size to Desmostylus in the study set, the one most similarly proportioned is the polar bear. Projection of Desmostylus on PC-II shows it to have been more aquatic than a polar bear (indicated by its relatively short ilium and femur, combined with relatively long metapodals and phalanges). Projection of Desmostylus on PC-III suggests that its aquatic locomotion was even more forelimb-dominated than that of a bear (indicated by its relatively long metacarpal III and corresponding proximal phalanx, combined with a relatively short metatarsal III and corresponding proximal phalanx). Desmostylians were different from all living semiaquatic mammals, and desmostylians are properly classified in their own extinct order, but their skeletal proportions suggest that bears provide an appropriate baseline for imagining what desmostylians were like in life.

Microstructural Reinforcement in the Canine Enamel of the Hyaenid Crocuta crocuta , the Felid Puma concolor and the Late Miocene Canid Borophagus secundus

Abstract: In bone-eating carnivores such as the hyena Crocuta crocuta, the tooth enamel contains a secondary vertical prism decussation phyletically derived from the wavelike horizontal decussation of primitive carnivores. The structure resists fracture under vertical, oblique, and horizontal tensile stresses, owing to the following modifications of the primitive structure. Positions of wave crests and of wave troughs are synchronized in the vertically successive layers of decussating prisms. Prisms in each successive layer run in a common direction at the crests and in a common but reversed direction at the troughs. Between the crests and troughs, prisms in obliquely slanting layers often retain their primitively reversed prism directions. Near the enamel–dentine junction (EDJ), irregular horizontal decussation is retained. In the upper canine of C. crocuta, a consumer of large bones, secondary vertical decussation is largely confined to the labial and anterior sides of the crown toward the tip where modeling of the static stresses predicts the tensile stresses to be highest and aligned vertically. In Puma concolor, which does not consume large bones, secondary vertical decussation is absent, indicating stress magnitude to be a critical factor in the selection for secondary vertical decussation. The canine enamel in Borophagus secundus, an extinct canid with derived aspects of skull and dental shape like those in hyenas, has dental structures similar to those in C. crocuta but which differ in several ways. The wavelike shapes of the decussation planes are better developed in transverse sections in B. secundus than in C. crocuta, suggesting either the folds are less modified or they dip at a steeper angle. Secondary vertical decussation in B. secundus is more extensive around the circumference of the canine than in C. crocuta, related to a difference in cross-sectional shape of the tooth. Vertical prism decussation may have been more frequently attained in carnivorous mammals than in ungulates because of the more random orientation of dental stresses which creates a selective advantage for wavy decussation planes—a structural transition to vertical decussation.

The Enamel Microstructure of the Early Eocene Pantodont Coryphodon and the Nature of the Zigzag Enamel

Abstract: An additional method for the investigation of the microstructure of enamel is described using the teeth of Coryphodon, Uintatherium, Entelodon, and Crocuta. Under low magnification natural surfaces or sections of teeth display details of the enamel microstructure when the light guide effect of prisms is used. Under the same low magnification even more details were obtained from sputter-coated surfaces of sections. The method is of particular significance for the investigation of large teeth with thick enamels when structures are somewhat irregular. The new method provides a better general survey, where scanning electron microscope images often show confusing details. The enamel of Coryphodon shows oblique lines of nested chevrons that are similar, to some degree, to the zigzag enamel in Crocuta, but a distinct asymmetry between ascending and descending lineaments was observed. This specific Coryphodon -enamel was also found in Uintatherium and Entelodon. This enamel type, which evolved several times in parallel, cannot be attributed to a specific diet, but must be regarded as one of the several ways to strengthen the enamel against breakage.

First Record of Stygimys (Mammalia, Multituberculata, Eucosmodontidae) from the Paleocene (Puercan) Part of the North Horn Formation, Utah, and a Review of the Genus

Abstract: A single tooth referred to Stygimys kuszmauli recovered at the Gas Tank Hill locality from Puercan strata of the North Horn Formation represents the first record of Stygimys from Utah. S. kuszmauli now occurs in both proposed north–south late Puercan biogeographic provinces, which reduces statistical support for provinciality. A new species from Texas, Stygimys vastus, is described. Of the five species previously referred to Stygimys, S. kuszmauli, Stygimys camptorhiza, Stygimys jepseni, and Stygimys teilhardi are valid, but Stygimys cupressus is synonymous with S. kuszmauli. The type of S. jepseni is restricted to a single p4 as the m1 thought to be from the same individual represents another multituberculate genus. Five sites, including Gas Tank Hill that comprise the Gas Tank Hill Local Fauna are widely dispersed in slumped strata which may differ in age, are located in a mostly floodplain depositional setting, and are small surface collected samples. Therefore, biogeographic analyses that compare the Gas Tank Hill Local Fauna to large samples collected from channel fills using screenwash techniques should be employed with caution. Stygimys has a relatively broad geographic and geochronologic distribution, but it is usually rare in Late Cretaceous and Early Paleocene mammalian assemblages. The recent recovery of Stygimys after more than 60 years of collecting in the North Horn Formation suggests that further sampling in other non-marine basins in Western North America will eventually yield additional specimens of the genus.

Problems with Paleocene Palynozones in the Rockies: Hell's Half Acre Revisited

Abstract: The scheme of palynostratigraphic zonation most widely applied to interbasinal correlation of Paleocene rocks in the Rocky Mountain region of North America is fundamentally flawed. In its initial publication (based on juglandaceous fossil pollen), basic principles of biostratigraphy were violated, the taxonomy was typological, and the phylogenetic analysis was methodologically unsound. Youngest parts of Paleocene time were not sampled during development of the zonation, and the basal two zones involved strata of Cretaceous age. Implications of paleoenvironmental influences on sequences of palynostratigraphic occurrences were not considered. Subjective assertions at many levels remain neither verifiable nor falsifiable, because data from specimens utilized in the published formulation of Paleocene palynozones P1–P6 cannot be reliably tied in their defining area to identifiable stratigraphic sequences at known positions in actual rocks. A rigorous and geologically useful palynological zonation for Paleocene strata in the Rockies is possible, and its development should be pursued. Procedurally, however, any such scheme must (1) be constructed according to sound principles of biostratigraphy; (2) contain accurate information about locations and stratigraphic positions of all samples; and (3) provide publicly accessible and verifiable taxonomic data on compositions of all samples.

The Heretic in Darwin's Court: The Life of Alfred RusselWallace. By Ross A. Slotten. New York: Columbia University Press. 2004. 602 pp. $39.50 (cloth). ISBN 0-231-13010-4

Abstract: As a Yale graduate student enrolled in a seminar entitled “The History of Physical Anthropology” I was asked to write a biography of an important figure from that discipline’s past. I chose Alfred Russel Wallace. The faculty in charge informed me that Wallace was a “flake” and that I should find another individual who was considered a bit more orthodox (I ended up doing my paper on W.E. Le Gros Clark). I begin my review with this anecdote as it encapsulates, I believe, the conventional wisdom regarding Wallace’s significance. Sure, he codiscovered a viable mechanism for evolutionary change, but he then went on to conduct a lengthy investigation into the “science” of spiritualism (and related areas such as mesmerism, hypnotism, etc.), and became an ardent critic of government vaccination programs. I am pleased to report that after reading Dr. Slotten’s fine biography, I have been disabused of this superficial and patently unfair assessment. In keeping with other biographers of Wallace, Slotten examines Wallace’s formative years and later place in Victorian society in comparison with Darwin. Whereas the latter was comfortably upper class, Wallace was born into a large Welsh family that often struggled financially. At the age of 13 he was forced to move to London and apprentice with his older brother, John. Wallace experienced urban, working class life, consequently developing a lifelong affection for political socialism that would inform much of his activities later in life. In fact, Slotten makes the interesting point that Wallace’s internalization of working class values and “position” might have influenced his later deference to Darwin regarding the issue of priority in discovering natural selection. Nonetheless, Darwin and Wallace maintained a longstanding personal relationship, mostly via written correspondence as they only met in person on a handful of occasions (the first not until 1862). This correspondence is well documented in Slotten’s book, and 150 years later the enormous gravity of these simple letters is palpable. As a surveyor’s apprentice, Wallace’s peripatetic work allowed him to indulge his passion for the natural world. Not satisfied with restricting his collecting to the British Isles, he planned a trip to the Neotropics along with Henry W. Bates, later renowned for his research into species mimicry. After spending five years exploring the Amazon River basin, Wallace lost most of his collections when his ship went down in the Sargasso Sea on his return voyage. Yet after only a few months at home, he began planning an ambitious journey to the Malay Archipelago that would last eight years. This is in contrast to Darwin,

Macaque Societies: A Model of the Study of Social Organization. Edited by Bernard Thierry, Mewa Singh andWerner Kaumanns. Cambridge: Cambridge University Press. 2004. 418 pp. $120.00 (cloth). ISBN 0-521-81847-8

Abstract: Readers of Macaque Societies lacking close familiarity with the primate behavioral biology literature, particularly research conducted with captive social groups, will find this edited volume odd. The back cover blurb and introductory chapter claim to explore “the nature and evolution of macaque social organization.” However, where are the detailed phylogenetic analyses of behavior, genetics, and morphology? While scant mention is made of selective regimes, quantitative evolution or biogeography, several prominent discussions refer to vague “deterministic” processes. Many of the 15 chapters, each with an appended, somewhat forlorn, separately authored text box, lack any hypothesis, much less presentation of testable alternative hypotheses. Either explicitly or implicitly, the premise of about one-third of the entries is that the approximately 20 congeners of the Old World monkey genus Macaca represent a clade best treated as a single phylogenetic unit, while another third of entries emphasize robust between-species divergence in character traits. The remaining topical accounts invoke both striking similarity and dissimilarity among macaques in the course of their arguments. As a primate biologist, I hasten to advise that nonspecialists should not interpret Macaque Societies as representing the state of evolutionary studies of nonhuman primates. A more subtle deconstruction is required. Instead, this volume embodies the clash of competing scientific paradigms. The editors, and several other contributors, notably Preuschoft, Chapais, Butovskaya, and Mason, and their students, incarnate perhaps the last hurrah of structural-functionalism as first formulated by anthropologists and other social scientists of the late 1800s versus the costs-benefit optimizations of inclusive fitness now prevalent. While giving lip service to evolution and selection, the fundamental concern of Thierry, Singh, and Kaumanns is identification of cybernetic mechanisms allowing the maintenance of a stable, “functioning” social organization. In effect, the grail of the editors’ quest is to understand the emergence of group-level structures in macaque sociality, such as dominance and matrilineal rank inheritance, despite inherent cycles of reproduction, mortality, aggression, and dispersal among the individuals comprising these groups. Evolutionary processes need not and are not to be invoked for description of group survival and welfare. For these intellectual descendents of Durkheim and Radcliffe-Brown, the static concepts of phylogenetic inertia and internal constraints are ultimately more critical to understanding macaque behavior and biology than terms such as directional selection, drift,