We Know Sea Level Rise is Getting Faster – #365papers – 2018 – 48

Nerem, Beckley, Fasullo, Hamlington, Masters, and Mitchum, 2018, Climate-change-driven accelerated sea-level rise detected in the altimeter era: Proceedings of the National Academy of Sciences

What’s it about?

Sea level is rising. In fact, it’s rising faster and faster. Using satellite data, the authors show that this is the case, even when variations from volcanic events and ‘ordinary’ ocean shifts (like El Nino) are taken into account. Continue reading

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

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

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

Placoderms, Dentary Bones, and the Origin of the Jaw – #UREES270 – 2018

Zhu, Ahlberg, Pan, Zhu, Qiao, Zhao, Jia, and Lu, 2016, A Silurian maxillate placoderm illuminates jaw evolution: Science, v. 354, p. 334-336.

What’s it about?

Placoderms are among the earliest vertebrates to have full-blown jaws. These jaws are develop from cartilagenous precursors that were once gill arches (or may have supported gills – that’s a whole ‘nuther discussion there). In more advanced bony fishes, like the common fishes we keep as pets, there are dermal bones that overlay these cartilagenous precursors: the dentary on the lower jaw and the maxillae over the upper jaw.

Until recently, it was thought that placoderms lacked these dermal bones. This paper is a description of the second species of placoderm that appears to have dentaries and maxillae. Continue reading

Migrating Marsupials of the Pleistocene – #365papers – 2018 – 44

Price, Ferguson, Webb, Feng, Higgins, Nguyen, Zhao, Joannes-Boyau, and Louys, 2017, Seasonal migration of marsupial megafauna in Pleistocene Sahul (Australia-New Guinea): Proceedings of the Royal Society B, v. 284: 20170785

What’s it about?

Seasonal migrations are seen in many large mammals. In modern animals, however, such migrations are not observed in marsupials. The authors put together geochemical data from rocks and fossil to show that the massive wombat-like extinct marsupial Diprotodon migrated seasonally as far as 100 km each way. Continue reading

Did the Chixulub Impact Make the Oceans Erupt More? – #365papers – 2018 – 43

Byrnes and Karlstrom, 2018, Anomalous K-Pg-aged seafloor attributed to impact-induced mid-ocean ridge magmatism: Science Advances, v. 4: eaao2994

What’s it about?

The Chixulub Impact is the event linked to the extinction of the dinosaurs. The authors here show that at the same time as the impact, ocean floor spreading increased for just a little while. They hypothesize that the seismic waves caused by the impact resulted in the mobilization of molten rock, leading to this increase in volcanic activity. Continue reading

Sampling Bias Changes Everything – #365papers – 2018 – 42

Dunne, Close, Button, Brocklehurst, Cashmore, Lloyd, and Butler, 2018, Diversity change during the rise of tetrapods and the impact of the ‘Carboniferous rainforest collapse’: Proceedings of the Royal Society B, v 285, 20172730

What’s it about?

The Carboniferous Period was a time of great forests which aided the diversification of early four-legged land vertebrates (tetrapods). At the end of the Carboniferous, the forested habitat was fragmented during an event called the ‘Carboniferous rainforest collapse’ (CRC). This fragmentation had strong effects on the continued diversification of tetrapods, however interpretations of this diversification may be in error due to sampling bias.

The authors here carefully assess tetrapod diversity, taking into account spatial and temporal biases in the fossil record, showing that there was a reduction of diversity during the CRC, but that diversity and connectedness between forest fragments increased after the CRC. Continue reading

Who Are the Heterostraci? – #UREES270 – 2018

Randle and Sansom, 2017, Phylogenetic relationships of the ‘higher heterostracans’ (Heterostraci: Pteraspidiformes and Cyathaspididae), extinct jawless fishes: Zoological Journal of the Linnean Society, v. 181, p. 910-926

What’s it about?

The Heterostraci are armored jawless fishes that are a sister group (evolutionary offshoot, if you will) to the lineage that later led to fishes with jaws. This paper is a discussion of how the various species of fish tucked into the Heterostraci are actually related. Continue reading

Anaspids, Jawless Fish Whose Armor Tell Us Where They Belong – #UREES270 – 2018

Keating and Donoghue, 2016, Histology and affinity of anaspids, and the early evolution of the vertebrate dermal skeleton: Proceedings of the Royal Society B, v. 283: 20152917

What’s it about?

The anaspids were a group of early, jawless fishes with bony armor covering their bodies. The authors discuss the structure of the bony armor and complete analyses to determine where anaspids actually fit into the evolutionary history of vertebrates. Continue reading