Better Specimens, Better Techniques, Better Understanding of the Sauropodomorpha – #365papers – 2018 – 17

Chapelle and Choiniere, 2018, A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha) based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha: PeerJ, v. 6, e4224

What’s it about?

Using CT scanning techniques, the authors were able to pull apart all the bones of a sauropodomorph dinosaur called Massospondylus. The sauropodomorphs are a group of dinosaurs that include all the sauropods (the ‘long necks’ if you’re a fan of The Land Before Time), and their more primitive ancestors.

By examining all the bones of the skull one at a time, the authors were able to better understand the actual relationships between Massospondylus and other primitive sauropodomorphs. Continue reading

Isotopes and Interpretations: Are We Getting it Right? – #365papers – 2018 – 15

Kohn and McKay, 2012, Paleoecology of late Pleistocene-Holocene faunas of eastern and central Wyoming, USA, with implications for LGM climate models: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 326-328, 42-53.

What’s it about?

Here, the authors compare values of carbon and oxygen isotopes from multiple species (herbivores and carnivores) from a single site to understand how these isotopes reflect environmental variables like annual precipitation and temperature, and how all the animals interacted with each other and the environment. Understandings gathered from the isotopic results were compared to what is known from modern, living animals and to the results from climate models. Continue reading

Color Vision in Cretaceous Birds – #365papers – 2018 – 14

Tanaka, Zhou, Zhang, Siveter, and Parker, 2017, Rods and cones in an enantiornithine bird eye from the Early Cretaceous Jehol Biota: Heliyon, v. 3, e00479

What’s it about?

A fossilized bird (as yet unidentified except to know it’s an enantiornithine bird) was found to have well-preserved structures in its eye, especially a fossilized retina. Using various methods (including scanning electron microscopy and specialized light microscope techniques) the authors were able to not only identify rods and cones in the retina, but were also able to determine that this bird was able to see in color. Continue reading

When the Structure of Bones Tell You How Animals Breathed – #365papers – 2018 – 13

Lambertz, Bertozzo, and Sander, 2018, Bone histological correlates for air sacs and their implications for understanding the origin of the dinosaurian respiratory system: Biology Letters, v. 14, 20170514

What’s it about?

Modern birds are known for having a system of air sacs throughout their bones, allowing birds to circulate air through their bodies in one direction (rather than air simply going in and out of the lungs as breathing works in mammals). This unidirectional flow of air allows birds to maximize the amount of oxygen extracted from the air they breathe.

In birds, the air sacs are openings in bones that are all connected to the lungs. There are air sacs in vertebrae and wing bones among other places. Many other animals have hollow places in bones that are not associated with air sacs. These openings served to lighten the weight of the bones.

The authors show that there are structures in the bone surrounding the open spaces that distinguish air sacs from other openings. Continue reading

Inside the Heads of Extinct Marine Reptiles – #365papers – 2018 – 12

Voeten, Reich, Araujo, and Scheyer, 2018, Synchrotron microtomography of a Nothosaurus marchicus skull informs on nothosaurian physiology and neurosensory adaptations in early Sauropterygia: PlosONE, v 13, e0188509

What’s it about?

This paper is about the use of syncrotron radiation to make images of the inside of the fossilized skull of a marine reptile. Using contrasts in density, the authors were able to distinguish between bones of the skull and originally empty places where the brain, nerves, and blood vessels would have gone. Continue reading

Carnivore Guilds: Are They the Same Everywhere? – #365papers – 2018 – 11

Croft, Engelman, Dolgushina, Wesley, 2017, Diversity and disparity of sparassodonts (Metatheria) reveal non-analogue nature of ancient South American mammalian carnivore guilds: Proceedings of the Royal Society B, v. 285, 20172012.

What’s it about?

The phrase ‘carnivore guild’ refers to the ecological roles of carnivores (animals that feed on other vertebrates) in a particular region. In most modern areas where many carnivorous mammals co-exist, some are hypercarnivores (like cats), some are mesocarnivores (like dogs), and some are hypocarnivores (like armadillos). These last two groups (meso- and hypocarnivores) would be more loosely categorized as omnivores, with hypocarnivores only very rarely consuming other vertebrates, despite having the capability of doing so more often.

In this paper, the authors compare modern mammalian carnivore guilds with the extinct marsupial carnivore guild of ancient South America, to see if the general proportions of hyper-, meso-, and hypocarnivores are about the same. They find that the South American carnivore guild is substantially different from modern guilds. Continue reading

Acanthodian Fishes and the Origins of Sharks – #365papers – 2018 – 10

Coates, Finarelli, Sansom, Andreev, Criswell, Tietjen, Rivers, 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?

Using modern tomographic techniques, the authors were able to examine the head and gill skeleton of a fossil fish called Gladbachus. The authors were able to see many characteristics that are both in common with acanthodian (so-called “spiny sharks”) and modern sharks. Continue reading

Can We Prove That Some Mammals ‘Hid Out’ During Glacial Times? – #365papers – 2018 – 9

Ntie, Davis, Hils, Mickala, Thomassen, Morgan, Vanthomme, Gonder, and Anthony, 2017, Evaluating the role of Pleistocene refugia, rivers and environmental variation in the diversification of central African duikers (genera Cephalophus and Philantomba): BMC Evolutionary Biology, v. 17.

What’s it about?

Researchers have suggested that during glacial times, tropical forests receded into restricted regions, wherein tropical forest animals were able to survive. After the glaciers receded, the forests spread again and the forest animals dispersed across the landscape. These restricted forested regions are called refugia. Because of the extended separation of the refugia, it is thought that animals and plants within would evolve and become distinct from those in other refugia.

This paper looks at a group of tiny deer called duikers. These deer live only in the thick forests of Africa. Through the study of fossil and modern DNA from duikers, these scientists studied the regional and subtle differences in DNA to attempt to prove or disprove the hypothesis that refugia existed in central Africa. Continue reading

Oxygenating the Oceans in the Early Cambrian – #365papers – 2018 – 8

Zhang, Chang, Khan, Feng, Denelian, Clausen, Tribovillard, and Steiner, 2017, The link between metazoan diversity and paleo-oxygneation in the early Cambrian: An integrated palaeontological and geochemical record from the eastern Three Gorges Region of South China: Palaeogeography, Palaeoclimatology, Palaeoecology.

What’s it about?

The Cambrian is the period of Earth’s history in which many of the modern groups of multicelluar organisms appeared in the fossil record for the first time. Some have argues that this also when these groups first appeared (the so-called “Cambrian Explosion”), but that’s not necessarily the case and is a good topic for another blog post. Rocks in South China provide a good record of this period of time and the authors show that the amount of oxygen in the ocean (and therefore in the atmosphere) fluctuated frequently during this important period of time. Continue reading

Comparing Modern and Fossil Diving Birds – #365papers – 2018 – 7

Bell, Wu, and Chiappe, in press, Morphometric comparison of the Hesperornithiformes and modern diving birds: Palaeogeography, Palaeoclimatology, Palaeoecology.

What’s it about?

The Hesperornithiformes are toothed birds that lived during the Cretaceous period. They are not directly related to modern birds, but clearly were birds that lived near water and foraged by diving, similar to modern cormorants, loons, grebes, and some ducks. In the past, some scientists have considered hesperornithiforms most similar to grebes and loons, but this paper shows that cormorants are a better modern analogue. Continue reading