What if We’re Wrong About Placoderms? – #365papers – 2018 – 57

Zhu, Yu, Ahlberg, Choo, Lu, Qiao, Qu, Zhao, Jia, Blom, and Zhu, 2013, A Silurian placoderm with osteichthyan-like marginal jaw bones: Nature, v. 502, p. 188-193

What’s it about?

I reported on another paper with Zhu as lead author sometime last week. That paper provided evidence that certain dermal bones (the dentary and maxilla), traditionally viewed as synapomorphies for the crown osteichthyes may also be present in placoderms. This is the first paper in which Zhu reported this observation.Continue reading “What if We’re Wrong About Placoderms? – #365papers – 2018 – 57”

Plants and Animals Don’t Respond to Climate Change the Same Way – #365papers – 2018 – 54

Wing and Harrington, 2001, Floral response to rapid warming in the earliest Eocene and implications for concurrent faunal change: Paleobiology, v. 27, p. 539-563

What’s it about?

The Paleocene-Eocene boundary is marked by a period of rapid global warming and co-occuring changes in mammals in response to the warming, including the appearance of seemingly dwarfed species and the rise of important mammal groups like the hoofed mammals and primates. The authors here use fossilized pollen from rocks known to bracket the Paleocene-Eocene boundary and discuss the changes in plants during this important episode of climate change.Continue reading “Plants and Animals Don’t Respond to Climate Change the Same Way – #365papers – 2018 – 54”

The Value of Fossils from the Margins of Basins – #365papers – 2018 – 53

Muldoon and Gunnell, 2012, Omomyid primates (Tarsiiformes) from the Early Middle Eocene at South Pass, Greater Green River Basin, Wyoming: Journal of Human Evolution, v. 43, p. 479-511

What’s it about?

Much of this paper is a description of a new species of early primate, along with a description of the primate fauna from South Pass, Wyoming, which is on the edge of the Green River Basin. This particular fauna is important because it is on the edge of a geographical basin, so it includes a mixture of animals that prefer flat plains and those that prefer upland areas.Continue reading “The Value of Fossils from the Margins of Basins – #365papers – 2018 – 53”

How Do Teeth and Jaws in Placoderms Grow? – #365papers – 2018 – 52

Rucklin, Donoghue, Johanson, Trinajstic, Marone, and Stamponi, 2012, Development of teeth and jaws in the earliest jawed vertebrates: Nature, v. 491, p 748-752

What’s it about?

Using tomographic data, the authors tease the different growth stages of the lower jaws of placoderms apart and show that the development of teeth are separate from the development of the jaw bone itself.Continue reading “How Do Teeth and Jaws in Placoderms Grow? – #365papers – 2018 – 52”

How Long Have Sharks Been Shark-y? – #UREES270 – 2018

Coates, Finarelli, Sansom, Andreev, Criswell, Tietjen, Rivers, and La Riviere, 2018, An early chondrichthyan and the evolutionary assembly of a shark body plan: Proceedings of the Royal Society B, v. 285, 20172418

What’s it about?

This paper provides a new description of a 385-million-year-old fish called Gladbachus. This fish has characteristics of what we consider sharks and other characteristics that align it with placoderms and bony fishes. With this new description, the authors do a new cladistic analysis that shows what the primitive shark condition looked like and also shows that an enigmatic group called the Acathodii are likely along the same lineage as sharks.Continue reading “How Long Have Sharks Been Shark-y? – #UREES270 – 2018”

Whence Come the Teeth of Vertebrates? – #365papers – 2018 – 51

Smith, 2003, Vertebrate dentitions at the origin of jaws: when and how pattern evolved: Evolution & Development, v. 5, p. 394-413

What’s it about?

Smith presents an argument that all teeth in vertebrates share a common origin, even though they look remarkably different, using evidence from growth lines in fossils, as well as developmental studies of modern fishes to support this. Continue reading “Whence Come the Teeth of Vertebrates? – #365papers – 2018 – 51”

Wait? What Part of the Pharynx Becomes the Jaw? – #UREES270 – 2018

Cerny, Lwigale, Ericsson, Meulemans, Epperlein, and Bronner-Fraser, 2004, Developmental origins and evolution of jaws: new interpretation of “maxillary” and “mandibular”: Developmental Biology, v. 276, p. 225-236

What’s it about?

Historically, it has been thought that the upper part of the first branchial (gill) arch becomes the upper jaw (maxillary) and the lower part of the first arch becomes the lower jaw (mandibular). By tracing neural crest cells in the embryos of axolotls and chickens, the authors show that both the upper and lower jaws develop from the lower part of the first arch, and that the upper part becomes the trabecular cartilage, which is part of the skull.Continue reading “Wait? What Part of the Pharynx Becomes the Jaw? – #UREES270 – 2018”

Waves of Extinction Add Up – #365papers – 2018 – 47

Wang and Zhong, 2018, Estimating the number of pulses in a mass extinction: Paleobiology, 1-20

What’s it about?

The problem with the rock record is that it is incomplete. This means that what was really a gradual extinction could look abrupt, or that a large-scale mass extinction can look like it was spread out. The authors of this paper present a method by which it is possible to determine how many pulses or waves of extinction added up to what we consider a mass extinction.Continue reading “Waves of Extinction Add Up – #365papers – 2018 – 47”

Footprints Tell a Tale of Everyday Life – #365papers – 2018 – 46

Altamura, Bennett, D’Aout, Gaudzinski-Windheuser, Melis, RAynolds, and Mussi, 2018, Archaeology and ichnology at Gombore II-2, Melka Kunture, Ethiopia: everyday life of a mixed-age hominin group 700,000 years ago: Scientific Reports, v. 8, 2815

What’s it about?

At a 700,000 year old archaeological site, mixed in with the footprints of hippos, birds, and various hoofed mammals are the footprints of people, ranging from adult to toddler. The presence of different ages of humans with evidence of animals and many archaeological specimens tells us that this reflects what everyday life may have looked like for people 700,000 years ago.Continue reading “Footprints Tell a Tale of Everyday Life – #365papers – 2018 – 46”

Sensing Electric Fields: It’s a Vertebrate Thing! – #365papers – 2018 – 45

King, Hu, and Long, 2018, Electroreception in early vertebrates: survey, evidence and new information: Palaeontology, 1-34.

What’s it about?

Electroreception, the ability to detect electric fields such as those generated by other fish swimming nearby, is a common vertebrate ability. It has been argued that bone initially evolved to act as an insulator for electroreceptors to improve their effectiveness. This paper is a review of what the bone evidence for electroreception is, and shows that it appears unlikely that bone evolved first as an insulator in vertebrates.Continue reading “Sensing Electric Fields: It’s a Vertebrate Thing! – #365papers – 2018 – 45”