Hypsodonty, horses, and the spread of C 4 grasses during the middle Miocene in southern California

ABSTRACT Background: C 4 grasses were not abundant in North America during the middle Miocene (c. 15 Ma). They did not become abundant until around 7 Ma. One can analyse stable carbon (

High variability within pet foods prevents the identification of native species in pet cats' diets using isotopic evaluation

Domestic cats preying on wildlife is a frequent conservation concern but typical approaches for assessing impacts rely on owner reports of prey returned home, which can be biased by inaccurate reporting or by cats consuming prey instead of bringing it home. Isotopes offer an alternative way to quantify broad differences in animal diets. By obtaining samples of pet food from cat owners we predicted that we would have high power to identify cats feeding on wild birds or mammals, given that pet food is thought to have higher C isotope values, due to the pervasive use of corn and/or corn by-products as food ingredients, than native prey. We worked with citizen scientists to quantify the isotopes of 202 cat hair samples and 239 pet food samples from the US and UK. We also characterized the isotopes of 11 likely native prey species from the southeastern US and used mixing models to assess the diet of 47 cats from the same region. Variation in C and N isotope values for cat food was very high, even within the same brand/flavor, suggesting that pet food manufacturers use a wide range of ingredients, and that these may change over time. Cat food and cat hair from the UK had lower C values than the US, presumably reflecting differences in the amount of corn used in the food chains of the two countries. This high variation in pet food reduced our ability to classify cats as hunters of native prey, such that only 43% of the animals could be confidently assigned. If feral or free ranging cats were considered, this uncertainty would be even higher as pet food types would be unknown. Our results question the general assumption that anthropogenic foods always have high C isotope values, because of the high variability we documented within one product type (cat food) and between countries (US vs. UK), and emphasize the need to test a variety of standards before making conclusions from isotope ecology studies

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

Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA

New dates obtained from the bone collagen of mammals from the deposits in Potter Creek Cave, Shasta County, California, USA, show that these fossils were emplaced over the last 30,000 yr. The dates support the assignment of the fauna in the cave to the late Pleistocene and are contemporaneous to the dates obtained from the fauna of Samwel Cave located 5 km to the north. These new dates do not support previous radiocarbon dates suggesting a Holocene extinction of the extinct bovid Euceratherium collinum, and demonstrate that this and other megafauna were not present in the vicinity after the terminal Pleistocene.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

AMS Radiocarbon Dates from Pleistocene and Holocene Mammals Housed in the New York State Museum, Albany, New York, USA

The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

New AMS Radiocarbon Dates from Late Pleistocene Mastodons and Mammoths in New York State, USA

During the Last Glacial Maximum (LGM) about 25,000 yr ago, the area of what is now New York State (USA) was almost entirely covered by the Laurentide Ice Sheet (LIS; Dyke et al. 2002). Subsequent habitation of this area after the melting of the LIS necessitates dispersal of fauna, and the timing of the dispersal of particular species may aid in the understanding of how the modern ecosystems of New York were assembled. Mastodons and mammoths represent the most abundant post-LGM Pleistocene megafauna recovered in New York. However, many of the specimens have not been dated. This paper presents a set of dates from bone and tooth dentine collagen of late Pleistocene mastodon (n = 7) and mammoth (n = 3) specimens housed in the Vertebrate Paleontology Collections at the New York State Museum, Albany, New York, USA.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Isotopes reveal limited effects of middle Pleistocene climate change on the ecology of mid-sized mammals

a b s t r a c t To better understand how past climatic change influenced mammalian communities, we used fossils from the Pit Locality of Porcupine Cave, to evaluate how two taxa responded to climatic events spanning two glacial-interglacial transitions of the middle Pleistocene in Colorado. We analyzed the isotopes of carbon, oxygen and strontium in 84 specimens of rabbits and marmots to infer (1) if feeding and habitat preferences differed across glacial-interglacial transitions, and (2) whether these taxa responded similarly and synchronously to climatic events. Our results showed no significant differences in any of the isotopic values within taxa across levels. Stable carbon isotope values revealed a C 3 -dominated environment around Porcupine Cave during the middle Pleistocene, similar to what is present around the cave today. Oxygen isotopes did not change significantly across levels suggesting consistent water sources over time and preventing any correlation to the Marine Isotope Stages. Marmots did show significantly more positive oxygen isotope values than rabbits over most of the Pit levels likely indicative of hibernation. Lack of significant change in Sr isotopes indicates similarity in habitat range through time, or homogenization of landscape Sr values due to atmospheric inputs. These results suggest that middle Pleistocene climatic change had a negligible effect on the ecology of the sampled individuals around Porcupine Cave. The effects of climate on mammals are complex and these results cannot be extrapolated globally; research is needed to differentiate how global climate change affects mammals in different regions and of different life history to provide insight into how current global warming will affect extant species

Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis.

Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation