Dietary Ecology of Pleistocene Quaternary Camels

Dietary ecology of Pleistocene camelids: Influences of climate, environment, and sympatric taxa

Authors:

Yann et al

Abstract:

Wild members of Camelidae live in some of the most arid environments, including North Africa, Arabia, the Gobi Desert of China and Mongolia and high elevation environments in the Andes Mountains. A better understanding of the paleoecology of the three most abundant Pleistocene camelids (Camelops, Hemiauchenia, and Palaeolama) may clarify modern adaptations to arid environments. Mammalian tooth enamel δ13C values were used to compare diets of co-occurring species in California, Texas, and Florida and δ18O values were used to investigate climate. Carbon isotope analysis suggests Camelops was likely an opportunistic browser that consumed both C3 and C4 browse/CAM plants, potentially consuming C4 browse (e.g., saltbush). Hemiauchenia had an opportunistic and highly generalized diet, while Palaeolama was a specialized forest browser. Stable oxygen isotopes and aridity index values suggest that Ingleside was warmer than McKittrick Brea, but there are no significant differences in aridity between the two sites. Co-occurrence data from the Paleobiology Database suggest that Palaeolama was restricted to forested environments as it occurred with two browsers, Tapirus and Odocoileus, at 90.5% of all sites. Camelops and Hemiauchenia both co-occurred with a broader range of taxa, further suggesting these camelids lived in diverse habitats. The generalized diet of Hemiauchenia, the likely ancestor of modern South American camelids, allowed for the adaptations of extant Lama and Vicugna to survive in the arid environments of the Andes Mountains. Collectively, these data clarify the dietary ecology of extinct camelids and provide insight into the potential importance of generalist diets for increased resilience to changing environments and/or climates.

Camels Originally Domesticated in Southern Arabia

Burger and her team succeeded in answering this question. The group of researchers analysed up to 7,000-year-old DNA from bones of wild and early-domesticated dromedaries and compared the samples with the genetic profiles of modern dromedary populations from around the world. For the first time, it was possible to identify the Southeast Arabian Peninsula as the region of first domestication. "Our results appear to confirm that the first domestication of wild dromedaries occurred on the southeast coast. This was followed by repeated breeding of wild dromedaries with the early-domesticated populations," Burger explains. The wild ancestor of today's dromedary had a geographically limited range and went extinct around 2,000 years after the first domestication.

link.

Studying the Evolution of the Horse's Spine

Modern horses are expert runners. They reach top speeds using a special running gait in which they hold their back stiff as they move. A new study published today reveals that tiny fossil ancestors of modern horses may have moved quite differently to their living counterparts.

"Horses provide a perfect case-study on the evolution of running because they have such an amazing fossil record", explains author Dr. Katrina Jones, a post-doctoral researcher in Harvard's Museum of Comparative Zoology. Dating back over 50 million years, the oldest horse ancestors were no bigger than a house cat. From those ancient horse ancestors, some lineages evolved larger sizes, grazing habit and limbs that were specialized for running. This new study suggests that the stiff-backed gait of modern horses likely evolved to save energy while running as horses got bigger through their evolution.

"For over a century, researchers studied the feet of fossil horses to explain how they evolved features specialized for running," explains Jones, "but very little is known about how the backbone might be involved in this famous transition." Four-legged mammals tend to move their lower back during running to help increase speed and regulate breathing. But horses are unusual because they restrict the motion of their lumbar spine to a single joint near their rump. Jones wanted to find out if this unusual pattern was shared by extinct horses, and how increasing size in horse evolution may have affected their back mobility and running style.

To understand the evolution of the back in fossil horses, Jones first examined the anatomy and mobility of the spine in modern domestic horses. The shape of the vertebral joints--bony connections between the vertebrae--help determine how much motion occurs at each joint. Armed with this information, Jones then measured the shape of vertebral joints in 16 species of fossil horses spanning their full size and age range.

link.

A Chalicothere Found in Mioecene Neogene Japan

Femur of Schizotheriinae (Perissodactyla, Chalicotheriidae) from the Lower Miocene Hiramaki Formation of the Mizunami Group in Gifu Prefecture, central Japan

Sadly, no abstract available.

The Siberian Unicorn Found a Refugium, Surviving until 29,000 Years ago

The beautiful title "Siberian unicorn" belongs to Elasmotherium sibiricum - an elasmotherium Siberian rhinoceros, which as previously thought became extinct 350,000 years ago. Nowadays the researchers of Tomsk State University (TSU) figured out that the "unicorn" found his last refuge "only" 29,000 years ago in Kazakhstan. The article, describing the new location of the fossil mammals in the Pavlodar Irtysh, was published in February 2016 in the American Journal of Applied Science.

"Most likely, in the south of Western Siberia it was a refúgium, where this rhino had preserved the longest in comparison with the rest of its range. There is another option that it could migrate and dwell for a while on the more southern areas," said Andrey Shpanski, a paleontologist at TSU. These conclusions were made due to research of the rhinocero's skull, found near Kozhamzhar village in Pavlodar region (Kazakhstan). The skull is well preserved: there are some cracks but no trace of pelletization, gnawing, and exfoliation. The fossils of the "unicorn" were examined by radiocarbon AMS-method analysis in the laboratory 14CHRONO Centre for Climate, the Environment, and Chronology (School of Geography, Archaeology and Palaeoecology; Queen's University Belfast; Belfast, UK). It turned out that the skull belonged to the animals that died 29,000 years ago. "Most likely, it was a very large male of very large individual age (teeth not preserved). The dimensions of this rhino today are the biggest of those described in the literature, and the proportion are typical," said the University's scientist.

link.

More Than one Species of Chalicothere Present in Miocene Neogene Oregon

New material of Moropus (Perissodactyla, Chalicotheriidae, Schizotheriinae) from the early Hemingfordian Rose Creek Member of the John Day Formation, Oregon, U.S.A.

Authors:

Coombs et al

Abstract:

A juvenile maxilla of Moropus with DP3–M1, collected from the early Hemingfordian (He1) Picture Gorge 36 local fauna of the Rose Creek Member of the John Day Formation of Oregon, U.S.A., is the best-preserved chalicothere specimen yet collected from the John Day Basin. It also provides additional understanding of early Miocene Schizotheriinae (Perissodactyla, Chalicotheriidae) in western North America. Although Coombs et al. attributed all of the John Day chalicotheres to Moropus oregonensis, the new specimen resembles in size and morphology some of its early Hemingfordian contemporaries from the Runningwater Formation of the Great Plains and is referred to Moropus sp. Moropus sp. can thus be added to the oreodont Merycochoerus magnus, the amphicyonid Daphoenodon (Borocyon) robustum, the dromomerycid Barbouromeryx, the moschid Parablastomeryx schultzi, and the equid Parahippus pawniensis as John Day taxa with close relatives in the early Hemingfordian of the Great Plains. Further, the identification of the fragmentary chalicothere fossils from the John Day Formation is made more complex by the likely presence of more than one species there during the early Miocene.

Eocene Paleogene Eohippus Found With Fossil Fetus

Description of a Well Preserved Fetus of the European Eocene Equoid Eurohippus messelensis

Authors:

Lorenz Franzen et al

Abstract:

The early Middle Eocene locality of Grube Messel, near Darmstadt (Germany), is famous for its complete vertebrate skeletons. The degree of preservation of soft tissues, such as body silhouettes, internal organs and gut contents, is frequently remarkable. The present specimen was analyzed for remnants of the reproductive system. Classic anatomy and osteology and high-resolution micro-x-ray were applied to describe the fetus of the European Eocene equoid Eurohippus messelensis. Scanning electronic microscopy (SEM) was used for determination of soft tissue remnants. The fetus is the earliest and best-preserved fossil specimen of its kind. The postcranial fetal skeleton is almost complete and largely articulated, allowing the conclusion that the pregnant mare was in late gestation. The apparent intrauterine position of the fetus is normal for the phase of pregnancy. Death of mare and fetus were probably not related to problems associated with parturition. Soft tissue interpreted as the uteroplacenta and a broad uterine ligament are preserved due to bacterial activity and allow considerations on the evolutionary development of the structures.

More Evidence South American Notoungulates are Perissodactyls

Ancient collagen reveals evolutionary history of the endemic South American ‘ungulates’

Author:

Buckley

Abstract:

Since the late eighteenth century, fossils of bizarre extinct creatures have been described from the Americas, revealing a previously unimagined chapter in the history of mammals. The most bizarre of these are the ‘native’ South American ungulates thought to represent a group of mammals that evolved in relative isolation on South America, but with an uncertain affinity to any particular placental lineage. Many authors have considered them descended from Laurasian ‘condylarths’, which also includes the probable ancestors of perissodactyls and artiodactyls, whereas others have placed them either closer to the uniquely South American xenarthrans (anteaters, armadillos and sloths) or the basal afrotherians (e.g. elephants and hyraxes). These hypotheses have been debated owing to conflicting morphological characteristics and the hitherto inability to retrieve molecular information. Of the ‘native’ South American mammals, only the toxodonts and litopterns persisted until the Late Pleistocene–Early Holocene. Owing to known difficulties in retrieving ancient DNA (aDNA) from specimens from warm climates, this research presents a molecular phylogeny for both Macrauchenia patachonica (Litopterna) and Toxodon platensis (Notoungulata) recovered using proteomics-based (liquid chromatography–tandem mass spectrometry) sequencing analyses of bone collagen. The results place both taxa in a clade that is monophyletic with the perissodactyls, which today are represented by horses, rhinoceroses and tapirs.

This came out just a hair behind the other paper.   I wonder which one was submitted first?

Mystery Solved: South American Ungulates (NotoUngulates) are Crown Perissodactyls (Horse, Rhino Cousins)

Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates

Authors:

Welker et al

Abstract:

No large group of recently extinct placental mammals remains as evolutionarily cryptic as the approximately 280 genera grouped as ‘South American native ungulates’. To Charles Darwin , who first collected their remains, they included perhaps the ‘strangest animal[s] ever discovered’. Today, much like 180 years ago, it is no clearer whether they had one origin or several, arose before or after the Cretaceous/Palaeogene transition 66.2 million years ago or are more likely to belong with the elephants and sirenians of superorder Afrotheria than with the euungulates (cattle, horses, and allies) of superorder Laurasiatheria . Morphology-based analyses have proved unconvincing because convergences are pervasive among unrelated ungulate-like placentals. Approaches using ancient DNA have also been unsuccessful, probably because of rapid DNA degradation in semitropical and temperate deposits. Here we apply proteomic analysis to screen bone samples of the Late Quaternary South American native ungulate taxa Toxodon (Notoungulata) and Macrauchenia (Litopterna) for phylogenetically informative protein sequences. For each ungulate, we obtain approximately 90% direct sequence coverage of type I collagen α1- and α2-chains, representing approximately 900 of 1,140 amino-acid residues for each subunit. A phylogeny is estimated from an alignment of these fossil sequences with collagen (I) gene transcripts from available mammalian genomes or mass spectrometrically derived sequence data obtained for this study. The resulting consensus tree agrees well with recent higher-level mammalian phylogenies. Toxodon and Macrauchenia form a monophyletic group whose sister taxon is not Afrotheria or any of its constituent clades as recently claimed , but instead crown Perissodactyla (horses, tapirs, and rhinoceroses). These results are consistent with the origin of at least some South American native ungulates from ‘condylarths’, a paraphyletic assembly of archaic placentals. With ongoing improvements in instrumentation and analytical procedures, proteomics may produce a revolution in systematics such as that achieved by genomics, but with the possibility of reaching much further back in time.

pop sci link.

Horses, Equids Have a Complicated Evolutionary History

Speciation with gene flow in equids despite extensive chromosomal plasticity

Authors:

Jónsson et al

Abstract:

Horses, asses, and zebras belong to a single genus, Equus, which emerged 4.0–4.5 Mya. Although the equine fossil record represents a textbook example of evolution, the succession of events that gave rise to the diversity of species existing today remains unclear. Here we present six genomes from each living species of asses and zebras. This completes the set of genomes available for all extant species in the genus, which was hitherto represented only by the horse and the domestic donkey. In addition, we used a museum specimen to characterize the genome of the quagga zebra, which was driven to extinction in the early 1900s. We scan the genomes for lineage-specific adaptations and identify 48 genes that have evolved under positive selection and are involved in olfaction, immune response, development, locomotion, and behavior. Our extensive genome dataset reveals a highly dynamic demographic history with synchronous expansions and collapses on different continents during the last 400 ky after major climatic events. We show that the earliest speciation occurred with gene flow in Northern America, and that the ancestor of present-day asses and zebras dispersed into the Old World 2.1–3.4 Mya. Strikingly, we also find evidence for gene flow involving three contemporary equine species despite chromosomal numbers varying from 16 pairs to 31 pairs. These findings challenge the claim that the accumulation of chromosomal rearrangements drive complete reproductive isolation, and promote equids as a fundamental model for understanding the interplay between chromosomal structure, gene flow, and, ultimately, speciation.

Cambaytherium thewissi: a Basal Perissodactyl From Ypresian Eocene Paleogene India

Working at the edge of a coal mine in India, a team of Johns Hopkins researchers and colleagues have filled in a major gap in science's understanding of the evolution of a group of animals that includes horses and rhinos. That group likely originated on the subcontinent when it was still an island headed swiftly for collision with Asia, the researchers report Nov. 20 in the online journal Nature Communications.

Modern horses, rhinos and tapirs belong to a biological group, or order, called Perissodactyla. Also known as "odd-toed ungulates," animals in the order have, as their name implies, an uneven number of toes on their hind feet and a distinctive digestive system. Though paleontologists had found remains of Perissodactyla from as far back as the beginnings of the Eocene epoch, about 56 million years ago, their earlier evolution remained a mystery, says Ken Rose, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine.

Rose and his research team have for years been excavating mammal fossils in the Bighorn Basin of Wyoming, but in 2001 he and Indian colleagues began exploring Eocene sediments in Western India because it had been proposed that perissodactyls and some other mammal groups might have originated there. In an open-pit coal mine northeast of Mumbai, they uncovered a rich vein of ancient bones. Rose says he and his collaborators obtained funding from the National Geographic Society to send a research team to the mine site at Gujarat in the far Western part of India for two weeks at a time once every year or two over the last decade.

The mine yielded what Rose says was a treasure trove of teeth and bones for the researchers to comb through back in their home laboratories. Of these, more than 200 fossils turned out to belong to an animal dubbed Cambaytherium thewissi, about which little had been known. The researchers dated the fossils to about 54.5 million years old, making them slightly younger than the oldest known Perissodactyla remains, but, Rose says, it provides a window into what a common ancestor of all Perissodactyla would have looked like. "Many of Cambaytherium's features, like the teeth, the number of sacral vertebrae, and the bones of the hands and feet, are intermediate between Perissodactyla and more primitive animals," Rose says. "This is the closest thing we've found to a common ancestor of the Perissodactyla order."

Cambaytherium and other finds from the Gujarat coal mine also provide tantalizing clues about India's separation from Madagascar, lonely migration, and eventual collision with the continent of Asia as the Earth's plates shifted, Rose says. In 1990, two researchers, David Krause and Mary Maas of Stony Brook University, published a paper suggesting that several groups of mammals that appear at the beginning of the Eocene, including primates and odd- and even-toed ungulates, might have evolved in India while it was isolated. Cambaytherium is the first concrete evidence to support that idea, Rose says. But, he adds, "It's not a simple story."

link.

Examining Perissodactyl Enamel Isotopes to Determine Eocene-Oligocene Paleogene Climate

Eocene-Oligocene Latitudinal Climate Gradients in North America inferred from Stable Isotope Ratios in Perissodactyl Tooth Enamel

Authors:

Zanazzi et al

Abstract:

The Eocene-Oligocene transition (~ 34 Ma) was one of the most pronounced episodes of climate change of the Cenozoic. In order to investigate this episode of global climate cooling in North America, we analyzed the carbon and oxygen stable isotope composition of the carbonate component of 19 perissodactyl (horse and rhino) tooth enamel samples from the Eocene-Oligocene rocks of the Cypress Hills Formation (southwestern Saskatchewan, Canada); we then compared the results with previously published data from the US Great Plains (Nebraska, South Dakota, and Wyoming).

Average (± 1σ) perissodactyl enamel δ13C values (vs. V-PDB) in the Eocene (-8.8 ± 0.3‰) and Oligocene (-9.0 ± 0.3‰) are indistinguishable, suggesting no major change in mean annual precipitation in Saskatchewan across the transition. The δ13C values in Saskatchewan indicate the presence of arid ecosystems and are slightly higher than those in the US Great Plains, suggesting drier conditions at higher latitudes. With respect to oxygen isotopes, average (± 1σ) perissodactyl enamel δ18O values (vs. V-SMOW) in the Eocene (19.8 ± 2.0‰) and Oligocene (20.1 ± 3.6‰) are also indistinguishable, suggesting no change in the δ18O of meteoric precipitation across the transition in Saskatchewan. Enamel δ18O variability is much larger in the Oligocene vs. Eocene, indicating a large increase in temperature seasonality. This increase in enamel δ18O variability is much larger than that recorded in the US Great Plains, suggesting that higher latitudes are more sensitive to major episodes of climate change with respect to temperature seasonality. Finally, our data indicate no major change in the Oligocene vs. Eocene latitudinal gradient in local water δ18O in North America, which suggests no change in mean annual temperature gradients across the transition. This result supports the hypothesis that ascribes the climate change of the transition with a drop in atmospheric pCO2 because climate models show that this mechanism produces uniform cooling at mid-latitudes.

Eocene Paleogene Anthracobunids are Stem Perissodactyls

Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls

Authors:

Cooper et al

Abstract:

Anthracobunidae is an Eocene family of large mammals from south Asia that is commonly considered to be part of the radiation that gave rise to elephants (proboscideans) and sea cows (sirenians). We describe a new collection of anthracobunid fossils from Middle Eocene rocks of Indo-Pakistan that more than doubles the number of known anthracobunid fossils and challenges their putative relationships, instead implying that they are stem perissodactyls. Cranial, dental, and postcranial elements allow a revision of species and the recognition of a new anthracobunid genus. Analyses of stable isotopes and long bone geometry together suggest that most anthracobunids fed on land, but spent a considerable amount of time near water. This new evidence expands our understanding of stem perissodactyl diversity and sheds new light on perissodactyl origins.

Radinskya is a Sister Taxon to Perissodactyls

On the skull of Radinskya (Mammalia) and its phylogenetic position

Author:

Holbrook

Abstract:

The skull of the Paleocene mammal Radinskya is redescribed here, based on direct study of the type and only specimen. A number of inaccuracies from previous studies are corrected. Radinskya possesses two potential synapomorphies with perissodactyls, namely, posteriorly broad nasals and a small, laterally facing exposure of the mastoid process of the periotic. The phylogenetic position of Radinskya is examined using matrices from three studies, two that originally included Radinskya and for which the scores for Radinskya are corrected, and another recent study of archaic ungulates that did not originally include Radinskya. In addition, a new analysis is performed combining data from all three previous studies, including modifications based on the present study. Reanalyses of the three previous studies give conflicting results regarding the issue of perissodactyl ancestry, placing Radinskya as sister taxon to perissodactyls, as sister taxon to a perissodactyl-phenacodontid clade, or as part of a polytomy with perissodactyls and paenugulates. The results of the new analysis (1) place perissodactyls closer to Radinskya than to phenacodontids; (2) place Hyracoidea and Proboscidea (i.e., Paenungulata) as sister taxa to Perissodactyla; (3) do not support inclusion of Radinskya in Phenacolophidae; and (4) are equivocal in placing Lophocion as the phenacodontid closest to perissodactyls. These results thus support neither an Asian nor a North American origin for perissodactyls. Future studies should examine the origins of perissodactyls and other ‘ungulates’ in a broader taxonomic context, in order to more directly address discrepancies between results supported by morphological data and those derived from molecular data.

Coelodonta nihowanensis: a New Species of Woolly Rhinoceros From Pleistocene Quaternary China

Juvenile skulls and other postcranial bones of Coelodonta nihowanensis from Shanshenmiaozui, Nihewan Basin, China

Authors:

Tong et al

Abstract:

Shanshenmiaozui in the Nihewan Basin of China is the locality that has produced the richest sample of Coelodonta nihowanensis material, including a nearly complete juvenile skull and mandible as well as various other cranial, mandibular, and postcranial bones. All of the cranial and mandibular specimens belong to individuals around 1.5 years old. On the basis of both qualitative morphological characters and osteometric measurements, the new specimens can be provisionally referred to the species Coelodonta nihowanensis. They also fall within the range of variation seen in late Pleistocene Coelodonta antiquitatis, but are distinct from this species in having developed cingula, relatively low-crowned teeth either with or without very thin cement on the surface, vestigial lower incisors, less backward-curved protolophs, and more slender limb bones. The newly discovered juvenile skull of Coelodonta nihowanensis from Shanshenmiaozui represents the only known complete juvenile skull of an early member of Coelodonta, and therefore has great significance for understanding the development and evolution of the genus. Extensive comparisons with all other Coelodonta species, and with extant rhinoceroses, indicate that the new specimens are much more similar to the true woolly rhino Coelodonta antiquitatis than to any other taxon.

Hipparion phlegrae: a new Species of Miocene Neogene Horse From Greece

Hipparion phlegrae, sp. nov. (Mammalia, Perissodactyla): a new species from the Turolian locality of Kryopigi (Kassandra, Chalkidiki, Greece)

Authors:

Lazaridis et al

Abstract:

A new hipparion species, Hipparion phlegrae, sp. nov., is described on the basis of both morphological characters and metrical data as a member of Hipparion s.s. It is compared with H. dietrichi, H. prostylum, and similar forms of the Greco-Iranian province. The age of the Kryopigi fauna is discussed as Turolian on the basis of the hipparion assemblage, whereas the coexistence of a small Cremohipparion referred here as C. matthewi/nikosi indicates that H. phlegrae, sp. nov., is probably a derived species in respect to H. prostylum. The decreased size of the H. phlegrae and the short and wide muzzle are discussed for Hipparion s.s. during the Turolian period. Phylogenetic relationships of the new species and related taxa are reconstructed and also considered.

A new Species of Hipparion Horse Found in Miocene Neogene Greece

Hipparion phlegrae, sp. nov. (Mammalia, Perissodactyla): a new species from the Turolian locality of Kryopigi (Kassandra, Chalkidiki, Greece)

Authors:

Lazaridis et al

Abstract:

A new hipparion species, Hipparion phlegrae, sp. nov., is described on the basis of both morphological characters and metrical data as a member of Hipparion s.s. It is compared with H. dietrichi, H. prostylum, and similar forms of the Greco-Iranian province. The age of the Kryopigi fauna is discussed as Turolian on the basis of the hipparion assemblage, whereas the coexistence of a small Cremohipparion referred here as C. matthewi/nikosi indicates that H. phlegrae, sp. nov., is probably a derived species in respect to H. prostylum. The decreased size of the H. phlegrae and the short and wide muzzle are discussed for Hipparion s.s. during the Turolian period. Phylogenetic relationships of the new species and related taxa are reconstructed and also considered.

Some Surprising Bits About Horse Evolution from Ancient DNA

Ancient DNA retrieved from extinct horse species from around the world has challenged one of the textbook examples of evolution – the fossil record of the horse family Equidae over the past 55 million years.

The study, published today in the Proceedings of the National Academy of Sciences, involved an international team of researchers and the Australian Centre for Ancient DNA (ACAD) based at the University of Adelaide.

Only the modern horse, zebras, wild asses and donkey survive today, but many other lineages have become extinct over the last 50,000 years.

ACAD Director Professor Alan Cooper says despite an excellent fossil record of the Equidae, there are still many gaps in our evolutionary knowledge. "Our results change both the basic picture of recent equid evolution, and ideas about the number and nature of extinct species."

The study used bones from caves to identify new horse species in Eurasia and South America, and reveal that the Cape zebra, an extinct giant species from South Africa, were simply large variants of the modern Plains zebra. The Cape zebra weighed up to 400 kilograms and stood up to 150 centimetres at the shoulder blades.

"The Plains zebra group once included the famous extinct quagga, so our results confirm that this group was highly variable in both coat colour and size."

Lead author of the paper, Dr Ludovic Orlando from the University of Lyon, says the group discovered a new species of the distinct, small hippidion horse in South America.

"Previous fossil records suggested this group was part of an ancient lineage from North America but the DNA showed these unusual forms were part of the modern radiation of equid species," Dr Orlando says.

A new species of ass was also detected on the Russian Plains and appears to be related to European fossils dating back more than 1.5 million years. Carbon dates on the bones reveal that this species was alive as recently as 50,000 years ago.

"Overall, the new genetic results suggest that we have under-estimated how much a single species can vary over time and space, and mistakenly assumed more diversity among extinct species of megafauna," Professor Cooper says.

"This has important implications for our understanding of human evolution, where a large number of species are currently recognised from a relatively fragmentary fossil record.

"It also implies that the loss of species diversity that occurred during the megafaunal extinctions at the end of the last Ice Age may not have been as extensive as previously thought.

Paper is located here.

Browsing Horse Found in Panama Canal Zone

Rushing to salvage fossils from the Panama Canal earthworks, Aldo Rincon, paleontology intern at the Smithsonian Tropical Research Institute, unearthed a set of fossil teeth. Bruce J. MacFadden, curator of vertebrate paleontology at the Florida Museum of Natural History, University of Florida in Gainesville, describes the fossil as Anchitherium clarencei, a three-toed browsing horse, in the May 2009 issue of the Journal of Paleontology.

By far the most complete fossil of a horse collected at the site in excavations spanning the last century, characteristics such as the shape of the teeth confirm the identity of two earlier finds and indicate that this horse was primarily a forest-dwelling browser living in the area between 15 and 18 million years ago. This evidence supports MacFadden's earlier proposal that the habitat was probably a mosaic of relatively dense forest and open woodlands. The presence of this browsing horse in Panama significantly extends the southern tip of its range from previous finds from roughly the same period in Florida, Nebraska and South Dakota.

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