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

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

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

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 “Who Are the Heterostraci? – #UREES270 – 2018”

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

Making Sense of Species Concepts – #365papers – 2018 – 41

Aldhebiani, 2017, Species concept and speciation: Sauti Journal of Biological Sciences, DOI: 10.1016/j.sjbs.2017.04.013

What’s it about?

The author here discusses several of the various concepts for defining species and the reasons why scientists would use one over another.Continue reading “Making Sense of Species Concepts – #365papers – 2018 – 41”

Defining and Distinguishing Species of Organisms – #365papers – 2018 – 40

de Queiroz, 2007, Species concepts and species delimitations: Systematic Biology, v. 56, 879-886.

What’s it about?

Species is a difficult concept in biology, even if it seems straightforward. The author of this paper shows that it really is as simple as it seems, but the means of distinguishing one species from another. The problem isn’t in the definition of species but in the distinction among species.Continue reading “Defining and Distinguishing Species of Organisms – #365papers – 2018 – 40”

Putting Together the Tetrapod Vertebra – #365papers – 2018 – 39

Pierce, Ahlberg, Hutchinson, Molnar, Sanchez, Tafforeau, and Clack, 2013, Vertebral architecture in the earliest stem tetrapods: Nature, v. 494, doi: 10:1038/nature11825

What’s it about?

In mammals, each vertebra is a single bone. However, these apparently singular bones are actually composed of several bones that are sutured together. This paper explores the individual bones that get fused together, and their origins in the transitional forms between fish and terrestrial tetrapods (four legged animals, e.g. amphibians, reptiles, birds, and mammals).Continue reading “Putting Together the Tetrapod Vertebra – #365papers – 2018 – 39”

Methods for Extracting Proteins from Fossils: Paleoproteomics – #365papers – 2018 – 38

Cleland and Schroeter, 2018, A comparison of common mass spectrometry approaches for paleoproteomics: Journal of Proteome Research, DOI: 10.1021/acs.jproteome.7b00703

What’s it about?

Recently, there has been great discussion about the extraction of proteins from fossils. This paper outlines various methods, and their strengths and weaknesses, for extracting proteins from ancient bones.Continue reading “Methods for Extracting Proteins from Fossils: Paleoproteomics – #365papers – 2018 – 38”

Fossil Mammals and the Rocks that Contain them at Fossil Butte, Wyoming – #UREES270 – 2018

Gunnell, Zonneveld, and Bartels, 2016, Stratigraphy, mammalian paleontology, paleoecology, and age correlation of the Wasatch Formation, Fossil Butte National Monument, Wyoming: Journal of Paleontology, v. 90, p. 981-1011

What’s it about?

This paper contains a discussion of the mammalian paleontology at Fossil Butte National Monument, Wyoming. The authors examined and identified at least 46 species of fossil mammals from 29 localities within rocks of the Wasatch Formation at Fossil Butte. Using techniques of stratigraphy, the authors correlated all the localities in order from oldest to youngest. Further, they used the species present and clues from the rocks themselves to interpret the ancient environment in which the mammals lived.Continue reading “Fossil Mammals and the Rocks that Contain them at Fossil Butte, Wyoming – #UREES270 – 2018”