Reading the Fossil Record: Look at the Rocks – #365papers – 2017 – 86

#365papers for March 27, 2017

Matthews, Liu, and McIlroy, 2017, Post-fossilization processes and their implications for understanding Ediacaran macrofossil assemblages; in Brasier, McIlroy, and McLoughlin, eds, Earth System Evolution and Early Life: a Celebration of the Work of Martin Brasier: Geological Society, London, Special Publication 448, 19 pp.

What’s it about?

Ediacaran fossils represent the oldest fossils of multicellular life, from between 580 and 541 million years ago (the Ediacaran Period). This paper discusses how the preservation of the fossils – the rock processes of deposition, erosion, deformation etc – affect our interpretations of the organisms. Continue reading

Some New Mammals from Ancient New Mexico – #365papers – 2017 – 85

#365papers for March 26, 2017

Williamson, Brusatte, Secord, and Shelley, 2016, A new taeniolabidoid multituberculate (Mammalia) from the middle Puercan of the Nacimiento Formation, New Mexico, and a revision of taeniolabidoid systematics and phylogeny: Zoological Journal of the Linnean Society, v. 177, p. 183-208.

What’s it about?

This paper discusses a group of large multituberculates that lived during the Paleocene (approximately 66 – 55 million years ago). Multituberculates, alas, are extinct, but resembled rodents in many ways. They were distinguished by their multi-cusped teeth (that looked a little like Legos) and blade-like premolars.

The right upper fourth premolar of Ptilodus gnomus. Notice the rows of pointed cusps, characteristic of multituberculates.

SEM image of the type specimen of the multituberculate Fractinus palmorem UW 27063 from locality V-90043. This is the blade-like tooth that is also common to multituberculates.

Taeniolabidoids would have been squirrel to marmot sized – as a group much larger than most other multituberculates. Continue reading

Evolving Teeth with Single Genes – #365papers – 2017 – 84

#365papers for March 25, 2017

Harjunmass, Seidel, Kakkinen, Renvoise, Corfe, Kallonen, Zhang, Evans, Mikkola, Salazar-Ciudad, Klein, and Jernvall, 2017, Replaying evolutinary transitions from the dental fossil record: Nature, v, 512, p. 44-48.

What’s it about?

This paper considers the complex shape of rodent molars. They show through gene manipulation how the complex rodent tooth came from a simpler, basic mammal shape. All that was required was to change the timing and duration of a single gene. Continue reading

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

Are Photos Enough to Name a Species – #365papers – 2017 – 82

#365papers for March 23, 2017

Garraffoni and Frietas, 2017, Photos belong in the taxonomic Code: Science, v 355, p. 805

Gutierrez and Pine, 2017, Specimen collection crucial to taxonomy: Science, v. 355, p. 1275.

What’s this about?

The International Code for Zoological Nomenclature lays out the requirements for naming a new species of animal. Included in this this the requirement of a preserved specimen Ithe type) to be kept at a museum for reference. Garraffoni and Frietas argue that for specimens that don’t preserve well (that is, they break down and can’t be effectively studied after preservation), that a photograph or photographs should stand in instead of a preserved specimen. Gutierrez and Pine argue back that even if a specimen is reduced to goo, it should still be required if only for the possibility of DNA preservation. 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

Birth of the Amazon River – #365papers – 2017 – 80

#365papers for March 21, 2017

Hoorn, Bogota-A, Romero-Baez, Lammertsma, Flantua, Dantas, Dino, Carmo, and Chemale, 2017, The Amazon at sea: Onset and stages of the Amazon River from a marine record, with special reference to Neogene plant turnover in the drainage basin: Global and Planetary Change.

What’s it about?

The authors of this paper use data from an ocean core collected in the delta of the Amazon River to determine when the Amazon River began to deposit sediments into the ocean and also when it began to carry sediments all the way from the Andes Mountains. 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

Putting All the Data Together Makes a More Complete History – #365papers – 2017 – 77

#365papers for March 18, 2017

Feakins, Levin, Liddy, Sieracki, Eglinton, and Bonnefille, 2017, Northeast African vegetation change over 12 m.y.: Geology, v. 41, p. 295-298.

What’s it about?

The authors combine pollen and isotopic data from fossil leaf waxes from an ocean core with soil carbonate data from northeast Africa to better understand the origin and composition of grasslands in northeast Africa over the last 12 million years. Continue reading