by Carl Strang
This week’s literature notes focus on selected papers from last year on the Mesozoic Era. These papers covered assorted topics; there were enough studies of early birds and feathered dinosaurs that I will treat them separately.
Jones, Marc EH, et al. 2013. Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara). BMC Evolutionary Biology 13 (1): 208 DOI: 10.1186/1471-2148-13-208 From a ScienceDaily article. Fossil jaws from the Middle Triassic show that reptiles representing the common ancestor of lizards, snakes and the tuatara were among the new groups to emerge in the wake of the end-Permian mass extinction.
Peter A. Hochuli and Susanne Feist-Burkhardt. 2013. Angiosperm-like pollen and Afropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland). Frontiers in Plant Science, DOI: 10.3389/fpls.2013.00344 From a ScienceDaily article. This pollen, which appears to belong to an insect- (probably beetle-) pollinated plant, comes from a time 100 million years before the previous accepted evolution of flowering plants. It provides a fossil anchor for the earlier end of the range of molecular clock pointers from other studies.
Varricchio, David J., Frankie D. Jackson, Robert A. Jackson, Darla K. Zelenitsky. 2013. Porosity and water vapor conductance of two Troodon formosus eggs: an assessment of incubation strategy in a maniraptoran dinosaur. Paleobiology 39 (2): 278 DOI: 10.1666/11042 They found that this small carnivorous dinosaur incubated partly buried eggs, not burying them completely like crocodiles. This conclusion is drawn in part because of egg-in-nest fossils, and largely because the fossils’ relatively few, small eggshell pores that limit moisture loss are like those of incubated eggs and unlike buried ones.
Blackburn, Terrence J., et al. 2013. Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province. Science 340:941-945. They have dated basalt samples around the edges of the Atlantic Ocean, looked at the rock just above and below those layers, and have connected the mass extinction that marked the end of the Triassic Period with a series of massive lava flows triggered by the rift that opened the Pangaea supercontinent and began to create the Atlantic Ocean as North America, South America and Africa split apart. They date the extinction at 201,564,000 years ago. The eruptions consisted of 2.5 million cubic miles of lava, in 4 major flows. Three of the flows occurred within 13,000 years, at the same time as the extinctions, which can be dated within 20,000 years at this point.
Bonnan, MF, et al. 2013. What lies beneath: sub-articular long bone shape scaling in eutherian mammals and saurischian dinosaurs suggests different locomotor adaptations for gigantism. PLoS ONE 8(10): e75216. doi:10.1371/journal.pone.0075216 Gigantic sizes were achieved more often in dinosaurs than in mammals. This study found that dinosaurs had relatively thick cartilage pads in load-bearing joints, making gigantism more frequently workable.
Bell, Phil R., Federico Fanti, Philip J. Currie, Victoria M. Arbour. 2013. A mummified duck-billed dinosaur with a soft-tissue cock’s comb. Current Biology DOI: 10.1016/j.cub.2013.11.008 From a ScienceDaily article. They describe a mummified fossil Edmontosaurus regalis with a previously unknowable soft-tissue “cock’s comb” structure on the top of its head.
Maiorino, L, A.A. Farke, T. Kotsakis, P. Piras. 2013. Is Torosaurus Triceratops? Geometric morphometric evidence of Late Maastrichtian ceratopsid dinosaurs. PLoS ONE 8(11): e81608. doi:10.1371/journal.pone.0081608 They did a comparative developmental study of fossils originally named Torosaurus and two species of Triceratops. Their measurements indicate different developmental trajectories for the two genera, and they reject the recent suggestion that Torosaurus is simply a more mature Triceratops.