Who Did It First? Sponges or Comb Jellies? #365papers – 2017 – 83

#365papers for March 24, 2017

Simion, Philippe, Baruain, Jager, Richter, Di Franco, Roure, Satoh, Queinnec, Ereskovsky, Lapebie, Corre, Delsuc, King, Worheide, and Manuel, 2017, A large and consistent phylogenomic dataset supports sponges as the sister group to all other animals: Current Biology, http://dx.doi.org/10.1016/j.cub.2017.02.031

What’s it about?

There is interest in which, of the most simple multicellular animals that live today, were the first to appear. Which are the most primitive? Which are ancestral to all other multicellular animals? Sponges and comb jellies are the simplest, most primitive animals alive today. Which came first? This paper provides new results suggesting sponges came first. Continue reading

Everything You Know About Dinosaurs Is Wrong – #365papers – 2017 – 81

#365papers for March 22, 2107

Baron, Norman, and Barrett, 2017, A new hypothesis of dinosaur relationships and early dinosaur evolution: Nature, v. 543, p. 501-506.

What’s it about?

Every person who has learned much about dinosaurs knows that dinosaurs are divided into two groups: the saurischians (lizard-hipped) and the ornithischians (bird-hipped). They also know that modern birds are actually saurischians dinosaurs, not ornithischians like you would think.

Now, based on what these authors have found, every person who knows the above things are now WRONG. Continue reading

Midges Versus Pollen for Understanding Past Climate – 365papers – 2017 – 79

#365papers for March 20, 2017

Samartin, Heiri, Joos, Renssen, Franke, Bronnimann, and Tinner, 2017, Warm Mediterranean mid-H0locene summers inferred from fossil midge assemblages: Nature Geoscience, v. 10, p. 207-212.

What’s it about?

Many global climate records show an episode of warming between 9000 and 5000 years ago. However, in the eastern Mediterranean region, the usual tools used to estimate temperature (in this case pollen) suggested that this was a cooler interval. The authors use fossilized larval chironomids (non-biting midges) found in lake deposits as another means to estimate summertime temperatures. The midges do show the expected warmth. Continue reading

Hypercarnivory, Tooth Development, and Evolutionary Dead Ends – #365papers – 2017 – 78

#365papers for March 19, 2017

Sole and Ladeveze, 2017, Evolution of the hypercarnivorous dentition in mammals (Metatheria, Eutheria) and its bearing on the development of tribosphenic molars: Evolution & Development, v. 19, p. 56-68.

What’s it about?

This paper discusses the teeth of carnivorous mammals, in particular the carnassials, or cutting teeth, characteristic of a meat-eating diet. These are the long, bladelike teeth toward the back of a dog or cat’s jaw, that come together with a scissor-like action to snip off bits of meat. Mammals from many different groups (including marsupials) have developed carnassial teeth.

The degree to which these teeth are blade like or still possess some of the crushing and puncturing features of ancestral mammals is an indication of how dependent on meat the mammal is. Cats, for example, lack the crushing and puncturing structures and are thus ‘hypercarnivores.’ Dogs in contrast, still have these ancient structures and are known to have a broader, more flexible diet. Continue reading

Global Warming; Shrinking Mammals – #365papers – 2017 – 76

#365papers for March 17, 2017

D’Ambrosia, Clyde, Fricke, Gringerich, Abels, 2017, Repetitive mammalian dwarfing during ancient greenhouse warming events: Science Advances, v. 3, e1601430.

What’s it about?

Rapid global warming in Earth’s past had occurred more than once. The most commonly studied episode occurred 55 million years ago, at the boundary between the Paleocene and Eocene epochs (Paleocene Eocene Thermal Maximum, PETM). Several other episodes have happened, including the ETM2 and H2 episodes which are discussed in this paper.

Dwarfing of mammalian species has been documented at the PETM. This paper shows dwarfing of mammals also occurred at the ETM2. Continue reading

Rocks and Fossils in the Uinta Basin, Getting it in Order – #365papers – 2017 – 74

#365papers for March 15, 2017

Townsend, Friscia, and Rasmussen, 2006, Stratigraphic distribution of upper middle Eocene fossil vertebrate localities in the eastern Uinta Basin, Utah, with comments on Uintan biostratigraphy: The Mountain Geologist, v. 43, p. 115-134.

What’s it about?

This paper is a synthesis of over 100 years worth of research in the Uinta Basin, making a huge effort to sort out how the rocks and fossils correlate and to get everything in the correct chronologic order. Continue reading

Appearance and Spread of Modern Forests in Asia and North America – #365papers – 2017 – 72

#365papers for March 13, 2017

Baskin and Baskin, 2016. Origins and relationships of the mixed mesophytic forest of Oregon-Idaho, China, and Kentucky: Review and synthesis: Annals of the Missouri Botanical Gardens, v. 101, p. 525-552.

What’s it about?

Modern forests of North America and Asia are remarkably similar in the species of trees present, but there is no obvious connection between the two. This paper discusses the lead hypotheses to explain the similarities Continue reading

The Middle Eocene Climatic Optimum in the Northern Hemisphere – #365papers – 2017 – 67

#365papers for March 8, 2017

Jovane, Florindo Coccioni, Dianares-Turell, Marsili, Monechi, Roberts, Sprovieri, 2007, The middle Eocene climatic optimum event in the Contessa Highway section, Umbrian Apennines, Italy: GSA Bulletin, v. 119, p. 413-427.

What’s it about?

This paper like others I’ve read recently discusses the abundance of single-celled organisms in the ocean called foraminifera (forams). The overall abundance of different species plus isotopic analysis of the fossils themselves can provide insights about climate during the middle Eocene. Continue reading

The Paleocene-Eocene boundary in deep ocean foraminifera – #365papers – 2017 – 65

#365papers for March 6, 2017

Thomas and Shackleton, 1996, The Paleocene-Eocene benthic forminiferal extinction and stable isotope anomalies, in Knox, Corfield, Dunay, eds., Correlation of the Early Paleogene in Northwest Europe: Geological Society Special Publication n. 101, p. 401-441.

What’s it about?

This paper examines the abundance and geochemistry of single-celled organisms called foraminiferans (forams) that were living in the oceans around 55 million years ago. Forams are still present today worldwide. They make little tiny calcite skeletons (called tests) that can be used to identify the species and then can be analyzed.

Using these foram skeletons, the authors identified the many species that lived in the ocean before and after the Paleocene-Eocene boundary and recognized some extinctions associated with the boundary. With geochemical analysis, they showed that there are some significant anomalies (rapid, unexpected changes) at the Paleocene-Eocene boundary. Continue reading

Knowing a Snail’s Diet from the Chemistry of its Shell – #3650papers – 2017 – 62

#365papers for March 3, 2017

Prendergast, Stevens, Hill, Hunt, O’Connell, and Barker, 2015, Carbon isotope signatures from land snail shells: Implications for palaeovegetation reconstruction in the eastern Mediterranean: Quaternary International, in press.

What’s it about?

This paper discusses the use of carbon isotopes in the shells of land snails to interpret what the snails were eating. To do this, they studied wild snails for which they could also measure the carbon isotopes of potential food sources. Continue reading