New Uintan primates from Texas and their implications for North American patterns of species richness during the Eocene

New omomyid fossils from the Purple Bench locality of the Devil's Graveyard Formation, middle Eocene (Uintan) of southwest Texas, are described. One specimen represents a new genus and species, herein named Diablomomys dalquesti. This new species is allocated to the tribe Omomyini, sister taxon to Omomys and Chumashius. A second specimen represents a range extension of the Utah species Mytonius hopsoni to the Trans-Pecos region of Texas. Previously, only one omomyid species (Omomys carteri) had been documented from Purple Bench and other late Uintan localities in the Devil's Graveyard Formation. These new omomyid fossils are of particular significance because Purple Bench is stratigraphically intermediate between the older late Bridgerian/early Uintan localities and the younger Duchesnean localities of Trans-Pecos Texas. With a more southerly location in the continental United States, the Devil's Graveyard Formation amplifies our understanding of patterns of North American primate richness at a time when the higher-latitude sites of the western interior were undergoing significant climatic cooling and increases in seasonality with commensurate faunal reorganization. Although the Uintan (approximately 46.5-40Ma) was a time in which anaptomorphine richness decreased dramatically, the results of this analysis suggest that Uintan omomyine richness is higher than was previously appreciated, particularly at lower latitudes.     

Sexual selection,genital morphology,and copulatory behavior in male Galagos

Variations in penile morphology among galago species are pronounced and complex. Comparative studies of galagos and other primate species show that elongation of the baculum (os penis)is associated with copulatory patterns involving a prolonged period of intromission. The enlarged penile “spines” of male galagos may be important in maintaining a genital “lock” during copulation. In primate species where females mate with a number of partners, sexual selection may have favored the rapid evolution of such features of penile morphology and masculine copulatory behavior. It is suggested that evolution of complex penile morphologies in galagos has been influenced by sexual selection and that such morphological variations are extremely useful in taxonomic studies.     

Middle Eocene habitat shifts in the North American western interior: A case study

There has been great interest in the global warming events that heralded the onset of the Eocene and particularly the response of mammalian faunas to these events. However, little information is available on the subsequent deterioration of tropical habitats in the interior of North America after these major warming episodes. The decline of tropical habitats is thought to have begun during the middle Eocene in the interior of North America, but until now, no studies have been able to document the details of this event. Recent fossil collection and stratigraphic studies from sites in southwestern Wyoming and northeastern Utah that span the middle Eocene offer a unique opportunity to evaluate changes in habitat in the western interior. Using a discriminant function analysis, habitats were reconstructed for a sequence of eight stratigraphically controlled middle Eocene assemblages. Adaptive profiles (diets, substrate use, and body masses) of fossil mammal communities were statistically compared to those of extant faunas from a variety of Neotropical habitats. Previously published magnetostratigraphic data from Utah provided a means to correlate our stratigraphic sections to the geomagnetic polarity time scale and the oxygen isotope record. The discriminant model shows that there was a significant change in the mammalian community ecology near the end of the late middle Eocene that is likely reflective of a habitat shift. When correlated to the time scale and oxygen isotope record, this key transition from forested habitats typical of the tropical early Eocene to more open woodlands began about 42 million years ago in this region of the Rocky Mountains.     

The Fayum primate forest: Did it exist?

The primates have the reputation of being essentially arboreal, forest-adapted animals. Yet there are many genera and species that inhabit an extremely wide array of non-forest habitats. Nevertheless, palaeoprimatologists often tend to depict fossil primate habitats as being more arboreal and more forest-like than is justified by the facts. It is worthwhile, therefore, to reconsider some current interpretations. In this paper, evidence of the Fayum Oligocene primate deposits are reviewed and discussed. The following conclusions emerge:(1) The large number of primate species indicates that the Fayum ecosystem was an optimum or near-optimum habitat for primates. (2) The lithological characteristics point to a sahélien type of climate. (3) The calcified and silicified root systems, having diameters up to 4 cm, suggest a sahélien type of shrub, bushland and/or small-tree vegetation. (4) The large fossilized logs cannot have grown on the spot and apparently represent driftwood from a more humid climatic belt in the south, as is indicated by damage resulting from fluvial transportation and by palaeobotanical data. (5) There may have been some minor patches or strips of medium-height forests and/or wood-lands in the Fayum delta, but there is no evidence of these.Thus the tall forest in which the earliest known African primates are currently supposed to have lived probably never existed. Grounds for this conclusion were presented by Unger 121 years ago, by Beadnell 75 years ago and by Kräusel 41 years ago, but sank into oblivion. The classic image of the primates as arboreal specialists seems to have interfered with seeing the facts. However, more extensive verification of the evidence by means of palaeobotanical research is still required. The fossil material to do so is readily available.     

Substrate Size and Primate Forelimb Mechanics: Implications for Understanding the Evolution of Primate Locomotion

International Journal of Primatology - Did the anatomical and locomotor specializations of primates evolve in response to requirements of locomotion and foraging on thin branches? Laboratory...     

Patterns of evolution among lower Jurassic crinoids

The crinoid families Isocrinidae and Pentacrinitidae are well represented in the British Lower Jurassic, allowing a detailed investigation of their evolution at this time. The pseudopelagic pentacrinitids diverged from the benthic isocrinids during the Triassic. Seirocrinus arose from Pentacrinites through hyper‐morphosis prior to the start of the Jurassic but both genera subsequently show extreme evolutionary conservatism, perhaps attributable to constraints imposed by their unusual life‐style. From a single species in the Hettangian, the benthic isocrinids diversified in the Sinemurian and Carixian. A “central lineage”;, comprising three species of Chladocrinus, evolved along a peramorphocline by “intermittent anagenesis”;, prolonged periods of evolutionary stasis punctuated by short periods of gradualistic change. Two main offshoots, Balanocrinus and Hispidocrinus gen. nov., represent shifts into new habitats. Balanocrinus arose through progenesis, with subsequent evolution along a paedomorphocline, while Hispidocrinus may have arisen through extreme peramorphosis, although its spinose brachials are an evolutionary innovation. Both genera show an apparently punctuated mode of evolution. There is some correlation between morphology and faciès, and also between the emergence of new species and times of high sea level. Benthic isocrinids appear to have been greatly affected by the early Toarcian anoxic event but the pseudopelagic pentacrinitids were not.