Eurygnathohippus woldegabrieli: A New Horse Species From Pliocene Neogene Ethiopia

A new species of fossil horse from 4.4 million-year-old fossil-rich deposits in Ethiopia,
Eurygnathohippus woldegabrieli, was about the size of a small zebra, Eurygnathohippus woldegabrieli, had three-toed hooves and grazed the grasslands and shrubby woods in the Afar Region, according to its naming in the Journal of Vertebrate Paleontology.

The horse fills a gap in the evolutionary history of horses but is also important for documenting how old a fossil locality is and in reconstructing habitats of human forebears of the time, said Scott Simpson, professor of anatomy at Case Western Reserve's School of Medicine, and co-author of the research. "This horse is one piece of a very complex puzzle that has many, many pieces."

The researchers found the first E. woldegabrieli teeth and bones in 2001, in the Gona area of the Afar Region. This fossil horse was among the diverse array of animals that lived in the same areas as the ancient human ancestor Ardipithecus ramidus, commonly called Ardi.

link.

Wortmania otariidens: A Puercan Paleocene Stylinodontidae Taeniodont

New Specimens of the Rare Taeniodont Wortmania (Mammalia: Eutheria) from the San Juan Basin of New Mexico and Comments on the Phylogeny and Functional Morphology of “Archaic” Mammals

Authors:

Thomas E. Williamson and Stephen L. Brusatte

Abstract:

Background

Taeniodonta is a clade of Late Cretaceous – Paleogene mammals remarkable for their relatively extreme cranial, dental, and postcranial adaptations and notable for being among the first mammals to achieve relatively large size following the Cretaceous-Paleogene mass extinction. Previous workers have hypothesized that taeniodonts can be divided into two clades: Conoryctidae, a group of small-bodied taeniodonts with supposedly “generalized” postcranial skeletons, and Stylinodontidae, a group of large-bodied, robust animals with massive forelimbs and claws adapted for scratch-digging. However, many taeniodont taxa are poorly known and few are represented by postcranial material, leaving many details about their anatomy, biology, and evolution ambiguous.

Methodology/Principal Findings

In this paper, we describe three new specimens of the rare taxon Wortmania otariidens from the early Paleocene (Puercan) of New Mexico. Among these specimens is one that includes remarkably complete cranial and dental material, including associated upper and lower teeth, and another that consists of partial forelimbs. These specimens allow for an updated anatomical description of this unusual taxon, supply new data for phylogenetic analyses, and enable a more constrained discussion of taeniodont biology and functional morphology.

Conclusions/Significance

The new specimen of Wortmania that includes associated upper and lower teeth indicates that previous interpretations of the upper dentition of this taxon were not accurate and the taxon Robertschochia sullivani is a junior synonym of W. otariidens. New specimens that include partial forelimbs indicate that Wortmania is very similar to later, large-bodied taeniodonts, with marked and distinctive adaptations for scratch-digging. Comparisons with other taeniodont taxa that include postcranial material suggest that all taeniodonts may have had scratch-digging adaptations. A phylogenetic analysis shows that Schowalteria and Onychodectes are basal taeniodonts, Stylinodontidae (including Wortmania) is monophyletic, and a monophyletic Conoryctidae (but not including Onychodectes) is only recovered when certain characters are ordered.

Hat tip to Matt Celesky, whom I am given to understand, found the  partial skull and really ought to bring back the Hairy Museum.

Extinction of Sirenia of Europe and North Africa

The disappearance of the European/North African Sirenia (Mammalia)

Authors:

1. Gonçalo Prista (a)
2. Mário Estevens (c)
3. Rui Agostinho (d)
4. Mário Cachão (a, b)

Affiliations:

a. Centre of Geology of the University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal

b. Faculty of Sciences of the University of Lisbon, Geology Department, Campo Grande, 1749-016 Lisbon, Portugal

c. Almada City Council, Departamento de Estratégia e Gestão Ambiental Sustentável Ecoteca de Almada - Casa Municipal do Ambiente R. Bernardo Francisco da Costa, nº 40 e nº 42 2800-029 Almada, Portugal

d. Faculty of Sciences of the University of Lisbon, Physics Department, Campo Grande, 1749-016 Lisbon, Portugal

Abstract:

Sirenia inhabited the coastal waters of Europe and North Africa from the Eocene until the end of the Pliocene. They are the only herbivorous marine mammals, and their presence in the European/North African realm is supported by almost 400 fossil records. Their dependence on seagrass, as well as their ecological needs, limited their capability to adapt to the climate changes that occurred during the Cenozoic. Their disappearance from European and Mediterranean shores occurred in two different steps: 1) the European Atlantic extinction, related to global cooling and fragmentation of the seagrass meadows, which greatly reduced sirenia habitats and resources; 2) their disappearance from the Mediterranean, linked not to declining resources but to the onset of continental glaciations in the northern hemisphere.

Geology Influencing Mammal Evolution in Mioecene Neogene North America?

Possible regional tectonic controls on mammalian evolution in western North America

Authors:

1. Malinda L. Kent-Corson (a)
2. Anthony D. Barnosky (b)
3. Andreas Mulch (c, d, e)
4. Marc A. Carrasco (b)
5. C. Page Chamberlain (f)

Affiliations:

a. Division of Earth Sciences, Nanyang Technological University, 639798, Singapore

b. Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA 94709, USA

c. Biodiversity and Climate Research Centre (BiK-F), 60325 Frankfurt, Germany

d. Institute of Geosciences, Goethe University Frankfurt, 60438 Frankfurt, Germany

e. Senckenberg Research Institute, 60325 Frankfurt, Germany

f. Department of Environmental Earth System Science, Stanford University, Stanford, CA 94305, USA

Abstract:

Previous work has suggested that tectonically active regions act as speciation pumps for mammals and plant species, but little is known about how fast or widespread tectonism must be in order to directly influence evolution. Here, we use oxygen and hydrogen isotopic data from Miocene sedimentary deposits to characterize the topographic evolution of the southern Columbia Plateau/Snake River Plain and northern Rocky Mountain regions during the Yellowstone hotspot passage, with the ultimate goal of understanding whether topographic changes caused by the hotspot influenced mammalian evolution within those regions. We conducted oxygen isotope analyses of 130 samples of lacustrine, and paleosol carbonate from Miocene stratigraphic sections that span much of the northern Rocky Mountain region, and combined these data with previously published isotopic records. Collectively these isotopic data show that caldera formation associated with the Yellowstone hotspot has modified regional topography and rearranged drainages along the track of the hotspot, and that the hotspot has left a topographic depression in its wake.

We explore the extent to which these topographic changes influenced or are decoupled from diversity changes exhibited by the local mammal faunas and conclude that the passage of the hotspot and consequent surface uplift created rainshadows in the lee of high-elevation calderas and/or generated large volumes of volcanic materials, influencing soils and vegetation. Collectively, that may explain a possible rise in mammal diversity in the CP/SRP region at ~ 14 Ma, coincident with a drop in diversity in the NRM. It is still unclear, however, how different taphonomic pathways and sample-standardization problems are influencing apparent diversity peaks at this temporal and geographic resolution.

Parallel Evolution Between Dogs and Hyenas

Extinctions and Evolution: Red Queen Hypothesis is Correct

The death of individual species is not the only concern for biologists worried about groups of animals, such as frogs or the "big cats," going extinct. University of California, Berkeley, researchers have found that lack of new emerging species also contributes to extinction.

"Virtually no biologist thinks about the failure to originate as being a major factor in the long term causes of extinction," said Charles Marshall, director of the UC Berkeley Museum of Paleontology and professor of integrative biology. "But we found that a decrease in the origin of new species is just as important as increased extinction rate in driving mammals to extinction."

The results apply to slow change over millions of years, Marshall cautions, not rapid global change like Earth is now experiencing from human activities. Yet the findings should help biologists understand the pressures on today's flora and fauna and what drove evolution and extinction in the past, he said.

The results, published June 20 in Science Express, come from a study of 19 groups of mammals either extinct or, in the case of horses, elephants, rhinos, and others, are in decline from a past peak in diversity. All are richly represented in the fossil record and had their origins sometime in the last 66 million years, during the Cenozoic Era.

The study was designed to test a popular evolutionary theory called the Red Queen hypothesis, named after Lewis Carroll's character who in "Through the Looking Glass" described her country as a place where "it takes all the running you can do, to keep in the same place."

In biology, this means that animals and plants don't just disappear because of bad luck in a static and unchanging environment, like a gambler losing it all to a run of bad luck at the slot machines. Instead, they face constant change – a deteriorating environment and more successful competitors and predators – that requires them to continually adapt and evolve new species just to survive.

Though the specific cause of declining originations and rising extinctions for these groups is unclear, the researchers concluded that their demise was not just dumb luck.

"Each group has either lost, or is losing, to an increasingly difficult environment," Marshall said. "These groups' demise was at least in part due to the loss to the Red Queen, that is, a failure to keep pace with a deteriorating environment."

Marshall and former post-doctoral fellow Tiago Quental found that the groups were initially driven to higher diversity until they reached the carrying capacity of their environment, that is, the maximum number of species their environment can hold, after which their environment deteriorated to the point where there was too much diversity to be sustained, leading to their extinction.

"In fact our data suggest that biological systems may never be in equilibrium at all, with groups expanding and contracting under persistent and rather, geologically speaking, rapid change" he said.