Past vegetation and climate of the Mogollon Rim Area, Arizona

This study reconstructs vegetation and climate encompassing pre-full glacial and Holocene time for the Mogollon Rim region of Arizona. Implications for the southwestern United States are discussed. Pine species (some currently disjunct) or species groups are identified. Two lakes were cored, the sediments were analyzed for pollen content, and dates were obtained by radiocarbon analysis. Hay Lake (2780 m) is surrounded by mixed conifer forest in the White Mountains, Arizona (34°N and 109°30'W). Jacob Lake (2285 m, 34°25' N and 110°50' W) is surrounded by ponderosa pine forest. Extrapolated dates for basal sediments are approximately 42,000 B.P. and 20,000 B.P. for Hay Lake and Jacob Lake respectively. Based on pollen, local vegetation at Hay Lake between approximately 42,000 and 29,000 B.P. consisted of mixed conifer forest dominated by Pinus aristata, P. flexilis and/or P. strobiformis with Picea codominant. Of the identified pine species, 98% are haploxylon and most are pinyon pine. Pinyon pine was more widespread at lower elevations than today. The proposed 1 Mid-Wisconsin climate has greater winter precipitation and summers cooler than today. However, the climate was warmer and probably drier than the full-glacial. Treeline was above the site. The period 29,000 to 25,000 B.P. is climatically and vegetationally transitory to the full glacial. Yellow pines (p. ponderosa/contorta) are present for the first time and Picea pollen increases from previous levels. The full glacial (25,000 to 13,700 B.P.) at Hay Lake is characterized by an association of Picea and Gramineae pollen and at Jacob Lake by Picea and Artemisia pollen. A high elevation parkland at the forest-tundra ecotone surrounded Hay Lake. Open coniferous forest surrounded Jacob Lake. A conservative estimate of treeline depression is 570 m. Winters during the full glacial were warmer and wetter and summers were cooler and drier than today. The early and middle Holocene is characterized by an increase in open vegetation and in herbaceous pollen taxa; Artemisia at Hay Lake and Gramineae at Jacob Lake. The climate was cooler and wetter than today but less so than during the Pleistocene. Iron-mottled sediments and a hiatus in the pollen record at Jacob Lake (between about 11,850 and 900 B.P.) together with expansion of Artemisia at Hay Lake represent overall drought during the middle Holocene when compared with today although summer monsoons may have been intensified. Modern pollen assemblages begin at Hay Lake about 1700 B.P. and are not datable at Jacob Lake. The transition to modern conditions may have resulted from increased fire frequency at Hay Lake and from fire suppression by early settlers at Jacob Lake.hydrology collectio

Oldest placental mammal from sub-Saharan Africa: Eocene microbat from Tanzania - evidence for early evolution of sophisticated echolocation

A partial skeleton of a new fossil microbat, Tanzanycteris mannardi, is the oldestplacental mammal found in sub-Saharan Africa. It came from early Lutetian (46 Ma)lake sediments in north-central Tanzania. T. mannardi has enlarged cochleae indicat-ing it was capable of a highly derived form of echolocation. Modern bats sharing simi-lar morphology are capable of precise navigation in dense forest undergrowth. Thephylogenetic relationships of T. mannardi are unclear. It shares character states withEocene Hassianycterididae, with extant Microchiroptera, and with Rhinolophoideawithin Microchiroptera. T. mannardi is important in documenting early evolution ofsophisticated bat echolocating abilities and demonstrating that Tanzanian crater lakesoffer an opportunity for future discoveries of Eocene mammals from the African interi

Oldest placental mammal from sub-Saharan Africa: Eocene microbat from Tanzania - evidence for early evolution of sophisticated echolocation

A partial skeleton of a new fossil microbat, Tanzanycteris mannardi, is the oldestplacental mammal found in sub-Saharan Africa. It came from early Lutetian (46 Ma)lake sediments in north-central Tanzania. T. mannardi has enlarged cochleae indicat-ing it was capable of a highly derived form of echolocation. Modern bats sharing simi-lar morphology are capable of precise navigation in dense forest undergrowth. Thephylogenetic relationships of T. mannardi are unclear. It shares character states withEocene Hassianycterididae, with extant Microchiroptera, and with Rhinolophoideawithin Microchiroptera. T. mannardi is important in documenting early evolution ofsophisticated bat echolocating abilities and demonstrating that Tanzanian crater lakesoffer an opportunity for future discoveries of Eocene mammals from the African interi