Diversification and biogeography of the one-toed horses Onohippidium and Hippidion

In this report we describe a large sample of Onohippidium galushai, new species, from the Late Hemphillian (Early Pliocene) of western Arizona, one ramus of Hippidion sp. from the Early Hemphillian (Late Miocene) of the Texas High Plains, and one ramus of cf. Hippidion sp. from the Irvingtonian (Late Pliocene to Early Pleistocene) of southern California. These one-toed horses were previously thought to have been confined to Plio-Pleistocene deposits of South America. Onohippidium from Arizona possesses a retracted nasal notch, deep preorbital facial fossae, and dental pattern diagnostic of South American representatives of this genus. Hippidion from Texas and California exhibit the dental characters, especially in the deep ectoflexids, seen in South American representatives of this genus. This is the first report of these horses from North America. The presence of Onohippidium and Hippidion in North America demonstrates that diversification of these endemics occurred prior to dispersal to South America during the Pleistocene great faunal interchange

New World hipparions

195 p. : ill., map ; 26 cm.Includes bibliographical references (p. 189-195)."Hipparions are a polyphyletic assemblage of three-toed horses that lived during the Miocene and Pliocene in the Old and New worlds. Four hipparion genera are recognized from Central and North America, they are: Hipparion sensu stricto, Neohipparion, Nannippus, and Cormohipparion. Of the 41 previously named species of New World hipparions, 15 are referred to the existing genera and the remaining 26 species names are considered to be either junior synonyms, incertae sedis, nomina nuda, or nomina dubia. One new species, Hipparion shirleyi, is described from the late Barstovian of the Texas Gulf Coastal Plain. This paper presents the systematics of New World hipparions in a scheme that principally includes an integration of quantitative and qualitative dental and cranial characters such as the configuration of the dorsal preorbital fossa. Statistical analyses of crania and dentitions provide determinations of the amount of character variation for North American hipparions. The hipparion from Mt. Léberon in southern France, Hipparion prostylum de Christol, 1832, is the genotypic species of Hipparion sensu stricto. In the New World, Hipparion sensu stricto is represented by three species; H. shirleyi, new species, H. tehonense (Merriam), 1916a, and H. forcei Richey, 1948, collectively known from the late Barstovian to the early Hemphillian of North America. Six species comprise the genus Neohipparion: N. coloradense (Osborn), 1918, N. affine (Leidy), 1869, N. trampasense (Edwards), 1982, N. leptode Merriam, 1915a, N. eurystyle (Cope), 1893, and N. gidleyi Merriam, 1915a, collectively known from the Clarendonian through late Hemphillian of Central and North America. Four species comprise the genus Nannippus: N. minor (Sellards), 1916, N. ingenuus (Leidy), 1885, N. beckensis Dalquest and Donovan, 1973, and N. peninsulatus (Cope), 1885, collectively known from the Clarendonian through late Blancan of Central and North America. In the New World, the genus Cormohipparion consists of three species, C. goorisi MacFadden and Skinner, 1981, C. sphenodus (Cope), 1889, and C. occidentale (Leidy), 1856, collectively known from the early Barstovian through early Hemphillian of North America. Hipparions are closely related to, or arose from, at least two separate taxa within the merychippine horse complex. The earliest North American hipparion, C. goorisi, is known from the 15-million-year old early Barstovian Gulf Coastal Plain of Texas. The peak of hipparion diversity in North America occurred about 12 to 8 1/2 million years ago during the height of the Clarendonian chronofauna. Hipparion diversity dropped during the Hemphillian. Only the genus Nannippus is known from the Blancan. Some previous workers state that all Old World hipparions were monophyletically descended from the oldest Old World species H. primigenium. However, based on similar hipparion facial morphotypes represented in both the Old and New worlds, it is possible that there were at least two hipparion dispersal events across Beringia, resulting in a polyphyletic assemblage in the Old World"--P. 5

Amateur Paleontological Societies and Fossil Clubs, Interactions with Professional Paleontologists, and Social Paleontology in the United States

Considerable interest exists among lifelong learners in the USA about fossils and the science of paleontology. Unlike some other science-related groups, e.g., astronomy and ornithology, interest in fossils among amateur paleontologists is primarily focused within local clubs and societies with little national coordination. This paper presents the results of formative evaluation of the FOSSIL project, conducted after the project “Kickoff” meeting held at the NAPC (North American Paleontological Convention) in 2014. FOSSIL is developing a national networked community of practice that includes amateur and professional paleontologists. Our research indicates that more than 60 amateur fossil clubs and societies exist in the USA, of which almost 40 have elected to be part of the FOSSIL network. Overarching goals of this program include enhanced collaborations between amateurs and professionals, knowledge-building about paleontology, access to resources for lifelong learning, and development a viable learning community of practice focused on topics of common and societal interest, such as collections (including digitization), evolution, climate change, and K-12 outreach. In addition to more traditional means such as list-serves and newsletters, FOSSIL is developing an online community (myFOSSIL) and using social media (Facebook and Twitter) to foster communication and interactions among stakeholders, and thus promoting the concept of “social paleontology”

Rise of the Andes

The surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening, leading to their gradual rise. Recent studies of the Andes indicate that their elevation remained relatively stable for long periods (tens of millions of years), separated by rapid (1 to 4 million years) changes of 1.5 kilometers or more. Periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable, dense lower lithosphere after long-term thickening of the crust and lithospheric mantle

Body mass predicts isotope enrichment in herbivorous mammals

Carbon isotopic signatures recorded in vertebrate tissues derive from ingested food and thus reflect ecologies and ecosystems. For almost two decades, most carbon isotope-based ecological interpretations of extant and extinct herbivorous mammals have used a single diet–bioapatite enrichment value (14‰). Assuming this single value applies to all herbivorous mammals, from tiny monkeys to giant elephants, it overlooks potential effects of distinct physiological and metabolic processes on carbon fractionation. By analysing a never before assessed herbivorous group spanning a broad range of body masses—sloths—we discovered considerable variation in diet–bioapatite d13C enrichment among mammals. Statistical tests (ordinary least squares, quantile, robust regressions, Akaike information criterion model tests) document independence from phylogeny, and a previously unrecognized strong and significant correlation of d13C enrichment with body mass for all mammalian herbivores. A single-factor body mass model outperforms all other single- factor or more complex combinatorial models evaluated, including for physiological variables (metabolic rate and body temperature proxies), and indicates that body mass alone predicts d13C enrichment. These analyses, spanning more than 5 orders of magnitude of body sizes, yield a size-dependent prediction of isotopic enrichment across Mammalia and for distinct digestive physiologies, permitting reconstruction of foregut versus hindgut fermentation for fossils and refined mean annual palaeoprecipitation estimates based on d13C of mammalian bioapatite

Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama

BACKGROUND: As we know from modern species, nursery areas are essential shark habitats for vulnerable young. Nurseries are typically highly productive, shallow-water habitats that are characterized by the presence of juveniles and neonates. It has been suggested that in these areas, sharks can find ample food resources and protection from predators. Based on the fossil record, we know that the extinct Carcharocles megalodon was the biggest shark that ever lived. Previous proposed paleo-nursery areas for this species were based on the anecdotal presence of juvenile fossil teeth accompanied by fossil marine mammals. We now present the first definitive evidence of ancient nurseries for C. megalodon from the late Miocene of Panama, about 10 million years ago. METHODOLOGY/PRINCIPAL FINDINGS: We collected and measured fossil shark teeth of C. megalodon, within the highly productive, shallow marine Gatun Formation from the Miocene of Panama. Surprisingly, and in contrast to other fossil accumulations, the majority of the teeth from Gatun are very small. Here we compare the tooth sizes from the Gatun with specimens from different, but analogous localities. In addition we calculate the total length of the individuals found in Gatun. These comparisons and estimates suggest that the small size of Gatun's C. megalodon is neither related to a small population of this species nor the tooth position within the jaw. Thus, the individuals from Gatun were mostly juveniles and neonates, with estimated body lengths between 2 and 10.5 meters. CONCLUSIONS/SIGNIFICANCE: We propose that the Miocene Gatun Formation represents the first documented paleo-nursery area for C. megalodon from the Neotropics, and one of the few recorded in the fossil record for an extinct selachian. We therefore show that sharks have used nursery areas at least for 10 millions of years as an adaptive strategy during their life histories

Effects of Global Warming on Ancient Mammalian Communities and Their Environments

Current global warming affects the composition and dynamics of mammalian communities and can increase extinction risk; however, long-term effects of warming on mammals are less understood. Dietary reconstructions inferred from stable isotopes of fossil herbivorous mammalian tooth enamel document environmental and climatic changes in ancient ecosystems, including C(3)/C(4) transitions and relative seasonality.Here, we use stable carbon and oxygen isotopes preserved in fossil teeth to document the magnitude of mammalian dietary shifts and ancient floral change during geologically documented glacial and interglacial periods during the Pliocene (approximately 1.9 million years ago) and Pleistocene (approximately 1.3 million years ago) in Florida. Stable isotope data demonstrate increased aridity, increased C(4) grass consumption, inter-faunal dietary partitioning, increased isotopic niche breadth of mixed feeders, niche partitioning of phylogenetically similar taxa, and differences in relative seasonality with warming.Our data show that global warming resulted in dramatic vegetation and dietary changes even at lower latitudes (approximately 28 degrees N). Our results also question the use of models that predict the long term decline and extinction of species based on the assumption that niches are conserved over time. These findings have immediate relevance to clarifying possible biotic responses to current global warming in modern ecosystems

Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula

Before the formation of the Central American Isthmus, there was a Central American Peninsula. Here we show that southern Central America existed as a peninsula as early as 19 Ma, based on new lithostratigraphic, biostratigraphic and strontium chemostratigraphic analyses of the formations exposed along the Gaillard Cut of the Panama Canal. Land mammals found in the Miocene Cucaracha Formation have similar body sizes to conspecific taxa in North America, indicating that there existed a terrestrial connection with North America that allowed gene flow between populations during this time. How long did this peninsula last? The answer hinges on the outcome of a stratigraphic dispute: To wit, is the terrestrial Cucaracha Formation older or younger than the marine La Boca Formation? Previous stratigraphic studies of the Panama Canal Basin have suggested that the Cucaracha Formation lies stratigraphically between the shallow-marine Culebra Formation and the shallow-to-upper-bathyal La Boca Formation, the latter containing the Emperador Limestone. If the La Boca Formation is younger than the Cucaracha Formation, as many think, then the peninsula was short-lived (1–2 m.y.), having been submerged in part by the transgression represented by the overlying La Boca Formation. On the other hand, our data support the view that the La Boca Formation is older than the Cucaracha Formation. Strontium dating shows that the La Boca Formation is older (23.07 to 20.62 Ma) than both the Culebra (19.83–19.12 Ma) and Cucaracha (Hemingfordian to Barstovian North American Land Mammal Ages; 19–14 Ma) formations. The Emperador Limestone is also older (21.24–20.99 Ma) than the Culebra and Cucaracha formations. What has been called the “La Boca Formation” (with the Emperador Limestone), is re-interpreted here as being the lower part of the Culebra Formation. Our new data sets demonstrate that the main axis of the volcanic arc in southern Central America more than likely existed as a peninsula connected to northern Central America and North America for much of the Miocene, which has profound implications for our understanding of the tectonic, climatic, oceanographic and biogeographic history related to the formation of the Isthmus of Panama