Author Archives: LS

New member of giant panda lineage found in Spain

Kretzoiarctos gen. nov., the Oldest Member of the Giant Panda Clade.

Abella J, Alba DM, Robles JM, Valenciano A, Rotgers C, et al.

The phylogenetic position of the giant panda, Ailuropoda melanoleuca (Carnivora: Ursidae: Ailuropodinae), has been one of the most hotly debated topics by mammalian biologists and paleontologists during the last century. Based on molecular data, it is currently recognized as a true ursid, sister-taxon of the remaining extant bears, from which it would have diverged by the Early Miocene. However, from a paleobiogeographic and chronological perspective, the origin of the giant panda lineage has remained elusive due to the scarcity of the available Miocene fossil record. Until recently, the genus Ailurarctos from the Late Miocene of China (ca. 8–7 mya) was recognized as the oldest undoubted member of the Ailuropodinae, suggesting that the panda lineage might have originated from an Ursavus ancestor. The role of the purported ailuropodine Agriarctos, from the Miocene of Europe, in the origins of this clade has been generally dismissed due to the paucity of the available material. Here, we describe a new ailuropodine genus, Kretzoiarctos gen. nov., based on remains from two Middle Miocene (ca. 12–11 Ma) Spanish localities. A cladistic analysis of fossil and extant members of the Ursoidea confirms the inclusion of the new genus into the Ailuropodinae. Moreover, Kretzoiarctos precedes in time the previously-known, Late Miocene members of the giant panda clade from Eurasia (Agriarctos and Ailurarctos). The former can be therefore considered the oldest recorded member of the giant panda lineage, which has significant implications for understanding the origins of this clade from a paleobiogeographic viewpoint.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048985?imageURI=info:doi/10.1371/journal.pone.0048985.g003

__________________________________
Laura

Feathered ornithomimosaur and T. rex dining habits

These are way cooler than Pleistocene waterpigs. ;P :]

Collected from Ben Creisler’s message to Dinosaur Maling List (dinosaur (at) usc.edu)

New in Science:

Darla K. Zelenitsky, François Therrien, Gregory M. Erickson, Christopher L. DeBuhr, Yoshitsugu Kobayashi, David A. Eberth, and Frank Hadfield (2012):
Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins.
Science 338(6106): 510-514
DOI: 10.1126/science.1225376
http://www.sciencemag.org/content/338/6106/510.abstract

Previously described feathered dinosaurs reveal a fascinating record of feather evolution, although substantial phylogenetic gaps remain.
Here we report the occurrence of feathers in ornithomimosaurs, a clade of non-maniraptoran theropods for which fossilized feathers were previously unknown. The Ornithomimus specimens, recovered from Upper Cretaceous deposits of Alberta, Canada, provide new insights into dinosaur plumage and the origin of the avian wing. Individuals from different growth stages reveal the presence of a filamentous feather covering throughout life and winglike structures on the forelimbs of adults. The appearance of winglike structures in older animals indicates that they may have evolved in association with reproductive behaviors. These specimens show that primordial wings originated earlier than previously thought, among non-maniraptoran theropods.

On the Nature site:

“How to eat a Triceratops” (with illustrations)
http://www.nature.com/news/how-to-eat-a-triceratops-1.11650

Apparently some cool stuff was presented in the SVP meeting… :/

–Mikko

Pleistocene hippopotamuses and climate-driven body size changes

Were Pleistocene hippopotamuses exposed to climate-driven body size changes?

Paul P. A. Mazza & Adele Bertini

This study proposes a working hypothesis that Mediterranean hippopotamuses, and perhaps European ones as well, reduced their size, sometimes even drastically, from the ‘Mid-Pleistocene Revolution’ (MPR, c.1.2–0.5 Ma) to the Late Pleistocene. In contrast to the Early Pleistocene, during this time period glacial/interglacial cycling was dominated by a 100-ka periodicity, with more extended glacial phases (up to 85 ka) alternating with shorter interglacial phases (up to 15 ka). These changes seem to have somehow affected the size of hippopotamuses. While relatively larger hippopotamuses have been found in warmer and somewhat more humid intervals, data seem to indicate that they might not have grown as large under less favourable conditions, namely during colder and comparatively drier times. This is a possible response to climate-driven fluctuations in food availability, but Pleistocene habitat fragmentation may also have had an influence. Environmental break-up during the late Quaternary led to the isolation of megafauna populations, which underwent modifications similar to those observed in insular mammals. Although the amount of remains available is still limited, it is nonetheless a fact that hippopotamuses changed their body size through time, normally becoming smaller. If the conclusions are confirmed as data continue to accumulate, hippopotamuses might cast doubt on the generality of Bergmann’s rule.

http://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.2012.00285.x/abstract

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Laura K.

Damn, this is HOT!! – Lethally Hot [Sea] Temperatures During the Early Triassic Greenhouse

Review:

http://www.sciencemag.org/content/338/6105/336.full

Bottjer, D. J., 2012: Life in the Early Triassic Ocean.
–Science: Vol. 338, #6105, pp. 336-337 [doi: 10.1126/science.1228998]

Abstract:

“In the next 100 years, it is projected that Earth will move to a greenhouse climate state. The future ocean will not only be hotter but also more acidic and will contain extended zones with reduced oxygen. Study of past periods of global warming helps to project what Earth and its biota will be like in this new state and what the journey to that state will entail. On page 366 in this issue, Sun et al. show that beginning with the end-Permian mass extinction (∼252.6 million years ago) and continuing for the next 5 million years, Earth’s oceans were extremely hot, with stressful and commonly lethal effects on ocean life.”

Article.

Sun, Y., Joachimski, M. M., Wignall, P. B., Yan, C., Chen, Y., Jiang, H., Wang, L. & Lai, X., 2012: Lethally Hot Temperatures During the Early Triassic Greenhouse.
–Science: Vol. 338, #6105, pp. 366-370 [doi: 10.1126/science.1224126]

Abstract:

“Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis.”

–Mikko

A pliosaur that could have made a T. rex whimper

It’s official: A giant marine reptile that roamed the seas roughly 150 million years ago is a new species, researchers say. The animal, now named Pliosaurus funkei, spanned about 40 feet and had a massive 6.5-foot-long skull with a bite four times as powerful as Tyrannosaurus rex.

“They were the top predators of the sea,” said study co-author Patrick Druckenmiller, a paleontologist at the University of Alaska Museum. “They had teeth that would have made a T. rex whimper.”

Combined with other fossil finds, the newly discovered behemoth skeletons of P. funkei paint a picture of an ancient Jurassic-era ocean filled with giant predators.

In 2006, scientists unearthed two massive pliosaur skeletons in Svalbard, Norway, a string of islands halfway between Europe and the North Pole. The giant creatures, one of which was dubbed Predator X at the time, looked slightly different from other pliosaurs discovered in England and France over the last century and a half.

Now, after years of painstaking analysis of the jaw, vertebrae and forelimbs, the researchers have determined that Predator X is in fact a new species, and they have officially named it for Bjorn and May-Liss Funke, volunteers who first discovered the fossils.

The pliosaurs, marine reptiles that prowled the seas 160 million to 145 million years ago during the Jurassic period, had short necks, tear-shaped bodies and four large, paddle-shaped limbs that let them “fly through the water,” Druckenmiller told LiveScience.

The new species likely lived closer to 145 million years ago and ate plesiosaurs, related long-necked, small-headed reptiles.

http://www.msnbc.msn.com/id/49448852/ns/technology_and_science-science/#.UH-sRWlra9U

Reference: E. M. Knutsen, P. S. Druckenmiller, and J. H. Hurum. 2012. A new species of Pliosaurus (Sauropterygia: Plesiosauria) from the Middle Volgian of central Spitsbergen, Norway. Norwegian Journal of Geology 92:235-258 (can be downloaded from http://www.geologi.no/njg/currentissue/)

__________________________________
Laura K. Säilä

Clade Age and Species Richness in Eukaryotic Tree of Life 

No fossil record included in this study (it is discussed briefly) but interesting paper in any case.

- Laura

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Clade Age and Species Richness Are Decoupled Across the Eukaryotic Tree of
Life

Daniel L. Rabosky, Graham J. Slater, Michael E. Alfaro

Abstract  
Explaining the dramatic variation in species richness across the tree of
life remains a key challenge in evolutionary biology. At the largest
phylogenetic scales, the extreme heterogeneity in species richness observed
among different groups of organisms is almost certainly a function of many
complex and interdependent factors. However, the most fundamental
expectation in macroevolutionary studies is simply that species richness in
extant clades should be correlated with clade age: all things being equal,
older clades will have had more time for diversity to accumulate than
younger clades. Here, we test the relationship between stem clade age and
species richness across 1,397 major clades of multicellular eukaryotes that
collectively account for more than 1.2 million described species. We find no
evidence that clade age predicts species richness at this scale. We
demonstrate that this decoupling of age and richness is unlikely to result
from variation in net diversification rates among clades. At the largest
phylogenetic scales, contemporary patterns of species richness are
inconsistent with unbounded diversity increase through time. These results
imply that a fundamentally different interpretative paradigm may be needed
in the study of phylogenetic diversity patterns in many groups of organisms.

http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001381