Category Archives: Science

Skulls and Brains of Early Mammalian Ancestors – #365papers – 2017 – 102

#365papers for April 12, 2017

Araujo, Fernandez, Polcyn, Frobisch, and Martins, 2017, Aspects of gorgonopsian paleobiology and evolution: insights from the basicranium, occiput, osseous labyrinth, vasculature, and neuroanatomy: PeerJ 5:e3119; DOI:10.7717/peerj.3119

What’s it about?

Gorgonopsians were land-dwelling vertebrates that existed early on along the lineage that eventually gave rise to mammals and to us. They did not yet possess classically mammalian features, in particular the structure of the middle ear, but they did share in common with us a skull shape called synapsidy. This feature distinguishes all mammals and their ancestors from other ‘reptiles’ like dinosaurs, lizards, snakes, and turtles, as well as birds.

The authors of this paper used Propagation Phase Contrast Synchrotron Radiation-based micro-Computed Tomography (a technique a little like a CAT-scan or an MRI) to examine two fossil gorgonopsian skulls. With this method, they were able to essentially take apart the bones of the skull and study their relationships. They were also able to look at the shape of the brain itself, as well as determining where the major blood vessels went and examine the structure of the inner ear.Continue reading “Skulls and Brains of Early Mammalian Ancestors – #365papers – 2017 – 102”

Before Long Snouts: An Early Phytosaur – #365papers – 2017 – 101

#365papers for April 11, 2017

Stocker, Zhao, Nesbitt, Wu, and Li, 2017, A short-snouted, Middle Triassic phytosaur and its implications for the morphological evolution and biogeography of Phytosauria: Nature Scientific Reports, 7:46028, DOI:10.1038/srep46028

What’s it about?

Phytosaurs are crocodile-looking marine reptiles from the Miocene. They are unique in having a long snout with the nares (nose openings) on the top of the skull, rather than on the tip of the snout. Here, a new phytosaur is described that has a short snout and the nares aren’t on the top of the head. It’s definitely a phytosaur due to other diagnostic skeletal features of the skull and limbs, and appears to represent an early stage of evolution where the characteristic snout and nostril position are not yet developed.Continue reading “Before Long Snouts: An Early Phytosaur – #365papers – 2017 – 101”

After the Disaster: Ecological Succession 555 Million Years Ago – #365papers – 2017 – 100

#365papers for April 10, 2017 — The 100th paper for 2017!

Reid, Garcia-Bellindo, Payne, Runnegar, and Gehling, 2017, Possible evidence of primary succession in a juvenile-dominated Ediacara fossil surface from the Flinders Ranges, South Australia: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 476, p. 68-76.

What’s it about?

The oldest fossils of multicellular organisms on Earth come from the Ediacara biota (575-541 million years ago). Such fossils are found globally, but were first described from the Flinders Ranges of South Australia.

The authors here describe a new locality in the Flinders Ranges that have many well-preserved Ediacaran fossils. Most of these fossils are smaller than the same species found at other localities. There is also an unexpected dominance of one species, Dickinsonia. This combined evidence suggests that this locality preserves an ecosystem that was developing not long after some environmental catastrophe. Thus, this is a primary successional fauna.Continue reading “After the Disaster: Ecological Succession 555 Million Years Ago – #365papers – 2017 – 100”

The Relationships of Ants and Bees and Stinging Wasps – #365papers – 2017 – 98

#365papers for April 8, 2017

Branstetter, Danforth, PIlls, Faircloth, Ward, Buffington, Gates, Kula, and Brady, 2017, Phylogenomic insights into the evolution of stinging wasps and the origins of ants and bees: Current Biology, v. 27, p. 1019-1025.

What’s it about?

The focus of this paper is to understand the relationships between wasps, ants, and bees, to see where the development of the complex social structures of ants and bees fall in the relationships, and where pollen eating (what makes bees, bees), fits into those relationships.

Turns out that bees and ants are subgroups in the larger group of stinging wasps.Continue reading “The Relationships of Ants and Bees and Stinging Wasps – #365papers – 2017 – 98”

A Little Giant from John Day – #365papers – 2017 – 96

#365papers for April 6, 2017

Mihlbachler and Samuels, 2016, A small-bodied species of Brontotheriidae from the middle Eocene Nut Beds of the Clarno Formation, John Day Basin, Oregon: Journal of Paleontology, v. 90, p. 1233-1244.

What’s it about?

This is a description of a new species of brontothere, giant rhino-like mammals from the middle Eocene (about 44 million years ago). This new species, Xylotitan, is actually small, as brontotheres go – only about the size of a modern tapir.Continue reading “A Little Giant from John Day – #365papers – 2017 – 96”

How Aridity Drove Plants to Deal with Air in their ‘Veins’ – #365papers – 2017 – 95

#365papers for April 5, 2017

Larter, Pfautsch, Domec, Trueba, Nagalingum and Delzon, 2017, Aridity drove the evolution of extremem embolism resistance and the radiation of the conifer genus Callitris: New Phytologist, doi: 10.1111/nph.14545

What’s it about?

Callitris is a conifer (evergreen) that lives in Australia. Many members of this genus live in highly arid areas and have to cope with long dry spells. These dry spells can result in air being drawn into the xylem (water conducting channels) of the trees. Just like in humans, air bubbles in the xylem (or air in our blood vessels) can be fatal. In both cases, an air bubble is called an embolism

It turns out that there is a relationship between a tree’s ability to resist embolisms and the history of the tree’s ancestors. Trees whose ancestors grew in more arid environments have greater resistance to embolisms.Continue reading “How Aridity Drove Plants to Deal with Air in their ‘Veins’ – #365papers – 2017 – 95”

Tall Teeth and Grazing Diets – #365papers – 2017 – 94

#365papers for April 4, 2017

Feranec and Pagnac, 2017, Hypsodonty, horses, and the spread of C4 grasses during the middle Miocene in southern California: Evolutionary Ecology Research, v. 18, p. 201-223.

What’s it about?

Modern horses have very tall (hypsodont) teeth. This is thought to be an adaptation for grazing, because chewing grass wears down teeth faster than chewing the leaves off a tree.

A fossil horse tooth from Natural Trap Cave. The grinding surface is on the left. Only about 1/5 of this tooth stuck above the gum line.

Paleontologists use the height of the tooth (its hypsodonty) to distinguish animals that grazed from those that ate bushes, shrubs, and trees (called browsing).

Isotopically, grasses look different from leaves from bushes. This chemical difference gets recorded into teeth.

The authors use isotopes from early horses that are hypsodont to show that tall teeth are related to doing more grazing.Continue reading “Tall Teeth and Grazing Diets – #365papers – 2017 – 94”

Puppy Play Bows Don’t Always Mean the Same Thing – #365papers – 2017 – 93

#365papers for April 3, 2017

Byosiere, Espinosa, Marshall-Pescini, Smuts, and Range, 2016, Investigating the function of play bows in dog and wold puppies (Canis lupus familiaris, Canis lupus occidentalis): PLOS one, v. 11, e0168570.

What’s it about?

Dog owners are familiar with the friendly play bow of their dogs, with the front legs outstretched and the rump high in the air. Where pet dogs are concerned, this is usually associated with playing – the kind of playing that doesn’t look much like playing but more like two dogs are going to kill each other. Ok, well maybe just my dogs.

Wolves (adults and puppies) also use the play bow. The question posed by the authors is what purpose does the play bow serve.Continue reading “Puppy Play Bows Don’t Always Mean the Same Thing – #365papers – 2017 – 93”

Feelings. Tyrannosaurid feelings – #365papers – 2017 – 92

#365papers for April 2, 2017

Carr, Varricchio, Sedlmayr, Roberts, and Moore, 2017, A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system: Nature Scientific Reports. DOI:10.1038/srep44942.

What’s it about?

This paper describes a new member of the Subfamily Tyrannosaurinae from the late Cretaceous of Montana. Two important things came from this study:

  1. The different species of tyrannosaurids that occur at different times may be the result of evolution along a single lineage, a process called anagenesis
  2. The structure of the skull suggests that the face of this tyrannosaurid was highly sensitive to touch.

Continue reading “Feelings. Tyrannosaurid feelings – #365papers – 2017 – 92”

When the Environment Changed, Animals Made Skeletons – #365papers – 2017 – 90

#365papers for March 31, 2017

Wood, Ivantsov, and Zhuravlev, 2017, First macrobiota biomineralization was environmentally triggered: Proceedings of the Royal Society B, v 284: 201700059

What’s it about?

It’s skeletons that we mostly see in the fossil record. The fossil record prior to the advent of mineralized skeletons (bones and shells, for example) is pretty sparse. Here, the authors show some very early organisms with skeletons (from around 550 million years ago) that have similar counterparts that lack the skeletons. Skeletons appear to have developed during times of environmental change, when minerals naturally grew around the bodies of the originally soft-bodied animals. Later, organisms took charge of this mineral growth to build the complex skeletons that we see in modern animals and plants.Continue reading “When the Environment Changed, Animals Made Skeletons – #365papers – 2017 – 90”