Search

Middle Miocene mammals are known from ~15 million-year-old sediments exposed along the Panama Canal of Central America, a region that otherwise has an exceedingly poor terrestrial fossil record. These land mammals, which represent a part of the ancient terrestrial herbivore community, include an oreodont Merycochoerus matthewi, small camel-like protoceratid artiodactyl Paratoceras wardi, two horses Anchitherium clarencei and Archaeohippus sp., and two rhinos Menoceras barbouri and Floridaceras whitei. Bulk and serial carbon and oxygen isotope analyses of the tooth enamel carbonate allow reconstruction of the ancient climate and ecology of these fossil mammals. Ancient Panama had an equable climate with seasonal temperature and rainfall fluctuations less than those seen today. The middle Miocene terrestrial community consisted predominantly, or exclusively, of C3 plants, i.show $132#e., there is no evidence for C4 grasses. Statistically different mean carbon isotope values for the mammalian herbivores indicate niche partitioning of the C3 plant food resources. The range of individual carbon isotope analyses, i.show $132#e., δ13C from -15.9 to -10.1‰, indicates herbivores feeding on diverse plants from different habitats with extrapolated δ13C values of -29.9 to -24.2‰, possibly ranging from dense forest to more open country woodland. The ecological niches of individual mammalian herbivore species were differentiated either by diet or body size. [ABSTRACT FROM AUTHOR]

Herbivory first evolved in terrestrial mammals during the late Cretaceous, ∼100 million years ago (Mya). Of the ∼35 ordinal-level clades of extinct or extant eutherian mammals from the New World, ∼24 have been adapted to herbivory in one form or another. Dental adaptations for specialized terrestrial browsing are first recognized during the early Cenozoic (Paleocene-Eocene). Mammalian herbivores adapted for grazing did not become widespread in the New World until the middle Cenozoic; it seems that this adaptation and the spread of grasslands occurred during the late Oligocene (30 Mya) in South America ∼10 million years earlier than in North America (20 Mya). Carbon isotopic evidence from fossil herbivore teeth indicates that C3 plants predominated until the late Miocene (∼8 Mya). Thereafter, C3 and C4 terrestrial communities diversified. Late Pleistocene extinctions ∼10,000 years ago decimated the diversity of mammalian herbivores, particularly those of larger body size. [ABSTRACT FROM AUTHOR]

Presents information on the discovery of a donkey-sized, three-toed, primitive horse, Protohippus gidleyi, from the Ecor Rouge Sand at the Mauvilla site in southern Alabama. Details on the discovery; Information on the genus Protohippus; Information on the study of the fossil.

Reports on discoveries concerning the diets, ecology, and extinction of ancient horses that lived in central Florida. Example of macroevolution that is found in the fossil record of horses; Carbon isotopic and tooth microwear data that provides information on the diet of the horses; Traditional morphological studies of tooth crown height; Species included in the six late Hemphillian Bone Valley horses.

The article discusses the techniques that museums must use to make way for donations such as large amounts of books. These techniques to maximize museum space include rail systems, movable carriages, and the use of shelving compactors. The installation of compactors allows the organization of museum libraries, so more museum space is liberated for exhibitions.

Many Cenozoic terrestrial fossil sites worldwide rely on land mammal evolution (biochronology) for temporal calibrations. Within marine depositional environments, strontium isotope compositions from invertebrate fossils are often used for enhanced temporal resolution. Here we demonstrate that strontium isotope ratios from fossil shark tooth enameloid can quantitatively calibrate ages at sites containing both marine and non-marine fossils. Analysis of REEs in the same samples provides data for understanding the taphonomic histories of the specimens and allows for identification of specimens that were likely reworked. Using Neogene shark teeth, we resolve a ∼ 600,000-year age difference between two late Miocene Florida sites previously binned together within the latest Hemphillian (Hh4) North American Land Mammal Age (NALMA) based solely on biochronology. This refinement brackets the Nme2 sea level lowstand, providing further calibration for the Great American Biotic Interchange (GABI) between South and North America. These examples emphasize the significance of strontium isotope ratios preserved in fossil shark teeth for global Neogene calibrations, especially in sites with marine/non-marine intercalations. [Display omitted] • The first use of strontium isotope ratios from shark tooth enameloid to calibrate ages of Florida fossil sites. • Sr isotopes derived from Neogene shark teeth resolve ∼600,000-yr mean age difference between two Hh4 Florida fossil sites. • REE analyses complement Sr-dating to assess taphonomic variance among specimens in the same deposit. • Phosphatic shark tooth enameloid is a reliable alternative to carbonate fossils for strontium dating. • Sr-dating can calibrate land mammal ages of hard-to-date fossil localities with marine/non-marine deposits globally. [ABSTRACT FROM AUTHOR]

The article reports that Thomas Huxley, an early advocate of Darwinian evolution, visited the U.S. in 1876 on a lecture tour and had planned to talk about evidence for evolution based on a fragmentary sequence of fossil horses from Europe. One of Huxley's first stops was at Yale, where he studied the fossil horse collection assembled by the paleontologist O.C. Marsh during expeditions to the western territories. Since the late 19th century, the 55-million-year phytogeny of horses has been cited as definitive evidence of long-term "quantum" evolution, now called macroevolution. It is the study of higher-level evolutionary patterns that occur on time scales ranging from thousands to millions of years.