To cap off the PLOS ONE 10 Year Anniversary collection series, we decided to focus our efforts on the PLOS ONE Editorial Board – a sizable group of accomplished scientists that has allowed us to
We are excited to announce that PLOS will be exhibiting at the Society of Vertebrate Paleontology 2014 Annual Meeting from 5-8th November in Berlin. This is only the second time that the meeting takes place outside North America, and the … Continue reading
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The exceptional gigantism of sauropod dinosaurs has long been recognized as an important stage in the evolution of vertebrates, the presence of which raises questions as to why no other land-based lineage has ever reached this size, how these dinosaurs functioned as living animals, and how they were able to maintain stable populations over distinct geological periods.
We are pleased to announce the publication of a PLOS Collection featuring new research on the complex Evolutionary Cascade Theory that attempts to answer these questions and explain how the unique gigantism of sauropod dinosaurs was possible. The fourteen papers that make up the collection address sauropod gigantism from a number of varied disciplinary viewpoints, including ecology, engineering, functional morphology, animal nutrition, evolutionary biology, and paleontology.
Sauropod dinosaurs were the largest terrestrial animals to roam the earth, exceeding all other land-dwelling vertebrates in both mean and maximal body size. While convergently evolving many features seen in large terrestrial mammals, such as upright, columnar limbs and barrel-shaped trunks, sauropods evolved some unique features, such as the extremely long necks and diminutive heads they are famous for. Dr Martin Sander, Professor of Paleontology at Universität Bonn and coordinating author for this series of 14 papers, said of the collection:
“This new collection brings together the latest research on the biology of sauropod dinosaurs, the largest animals to ever walk on Earth. Having been extinct for 65 million years, reconstructing sauropod biology represents a particular challenge. Using a wide array of scientific expertise, often from seemingly unlikely fields, has led to some amazing insights. For example, principles of soil mechanics have been used to ‘weigh a dinosaur’ based on its trackways, whilst the latest in computer modeling can make a dinosaur walk again.
The ultimate question underlying this research is how sauropods were able to evolve their uniquely gigantic body size. The wide-ranging disciplines covered in the collection means that there is a -broad, multi-disciplinary audience for the research, as well as general interest in dinosaurs; therefore, we felt that it was essential to publish such a volume in a leading open-access journal such as PLOS ONE to ensure the widest possible dissemination of our work.”
Readers are able to download “Sauropod Gigantism: A Cross-Disciplinary Approach” not only as a PDF but also as an ebook (.mobi and .epub formats) from the collection page. It will also be available on Flipboard (search “PLOS Collections”).
Collection Image: Kent A. Stevens, University of Oregon
Earlier this month we gave you cuddling between affectionate lions. Lest we become overwhelmed by the desire to cuddle one of these (albeit adorable) feline predators ourselves, here is a look at exactly what one of their clawed paws could do to us, including to one of our toughest components: bone. In a PLOS ONE study published earlier this month, researchers tested the ability of claws to scratch the surface of bone. The effects of claw damage are often overlooked because claws are made of a material softer than bone. Contrary to expectations, however, these researchers found that claws produced recognizable bone damage.
The setup was simple: let a Kansas zoo tiger participating in their enrichment program spend an afternoon leisurely playing with carefully nested cow thigh bones, also called femora. To ensure that the cow femora were only accessible to tiger claws and not to tiger teeth, researchers bolted femora down into a log that was narrowly hollowed out—preventing the big cat from sticking his snout in.
The result: impressively lacerated cow femora. Once tiger playtime was over, researchers removed the log, unbolted the femora, and microscopically examined the bone. Four scratches were clearly visible upon the bone’s surface. The scanning electron microscope (SEM) image below further highlights the depths of the tiger claw handiwork.
In this particular gouge, the main diagonal chasm in the image, the gulf made by the tiger’s claw penetrated the outer covering and subadjacent bone into the bony matrix. As we can see, tiger claws can do some damage.
Damage done to bone, however, is for the most part attributed to the effects of a predator’s teeth and not its claws, the reason being that measures of scratch resistance adhere to a so-called Mohs scale of mineral hardness. The Mohs scale is graded, with talc (1) as the softest material and diamond (10) as the hardest. On the scale, harder materials damage softer materials, but not vice versa. And in our case, bones are, in fact, harder than claws. Claws are made of the protein keratin—the same stuff is in hair, wool, nails, horns, and hooves—which scores a meager 2.5 on the Mohs scale. Bone, on the other hand, scores a much more formidable 5.0.
The current research, however, shows that we can expand our understanding of scratch resistance and mineral hardness to include the effects of softer materials striking harder materials, as long as we consider the kinetic energy involved, like the action of a tiger swatting or grabbing with its paw. In essence, more could be going on in the fossil record than previously thought.
Paleontologist and PLOS ONE Section Editor Andy Farke points out in the PLOS ONE blog The Integrative Paleontologist that fossils inevitably resurface as imperfect objects, which is, in part, what makes them so interesting: These fossils bear the visible marks in postpartum decay of a long and varied history. When studying bone narratives, paleontologists encounter everything from water damage to the bore marks of little critters. Including big-critter claw marks in the repertoire of possible bone modifications broadens this narrative and evidences, as the researchers themselves so aptly put it, the power of the claw.
Rothschild BM, Bryant B, Hubbard C, Tuxhorn K, Kilgore GP, et al. (2013) The Power of the Claw. PLoS ONE 8(9): e73811. doi:10.1371/journal.pone.0073811
Image 2: doi:10.1371/journal.pone.0073811
Image 3: doi:10.1371/journal.pone.0073811
The small but sharp-toothed Thrinaxodon probably spent much of its time dining on its Triassic cohabitants, but a study published today reports a pristine fossil of the meat-eater apparently peacefully sharing its burrow with a small amphibian – until they were both buried in a flood.
The researchers uncovered the odd couple through non-destructive imaging 0f a burrow cast from South Africa, where the animals appeared to have died together. In the image of the cast itself, along with the ghostly outlines of the animal skeletons you can see that layer 1 is the original bed of the burrow, and layers 2 and 3 correspond to subsequent “pulses” of the flooding event.
The two skeletons are remarkably complete and well-preserved (in the image above Thrinaxodon is shown in brown, and the amphibian in grey), and the artifact provides an excellent opportunity to study the interactions between two different species. Given Thrinaxodon‘s carnivorous ways, it may at first seem most likely that the amphibian was about to be eaten for lunch, but its undisturbed skeleton and lack of expected bite marks rule out this possibility, the authors write. They also conclude that the flood responsible for burying the animals couldn’t have randomly washed the amphibian into the burrow once the animals were already dead because the burrow’s opening was too small.
To find the most likely answer, the researchers turned to modern creatures for insight. They note that animals today will live in a burrow built by another species if it is abandoned, if they can chase away the host, or if the host tolerates their presence. The Thrinaxodon was still in the den, so neither of the first two possibilities seem to apply in this case, leaving the last option as the most likely. As strange as it may seem, it appears that for whatever reason the Thrinaxodon graciously tolerated its amphibian partner’s presence.
If you want to see more, this video shows how the authors virtually dissected the burrow using synchrotron scanning to create an exquisitely detailed reconstruction of the burrow’s contents without cracking it open.
Citation: Fernandez V, Abdala F, Carlson KJ, Cook DC, Rubidge BS, et al. (2013) Synchrotron Reveals Early Triassic Odd Couple: Injured Amphibian and Aestivating Therapsid Share Burrow. PLoS ONE 8(6): e64978. doi:10.1371/journal.pone.0064978
Fossil records show that pterosaurs of all sizes and shapes flew through the skies of China and Central Asia about 145 to 66 million years ago. A new species of small pterosaurs described in a PLOS ONE paper reveals that western Europe may have had a similar diversity of these ancient animals. Author Darren Naish discusses the importance of the new species, named Vectidraco.
How did you begin studying dinosaurs (or pterosaurs in particular)?
Most of my research is and has been based on the Lower Cretaceous fossils that come from the Isle of Wight and elsewhere in southern England. The rocks here are famous for their dinosaurs, but fossil crocodilians, marine reptiles like plesiosaurs and rare pterosaurs are found here too. I’ve always been interested in pterosaurs and for several years have had a special research interest in a highly peculiar pterosaur group called the azhdarchoids – I’ve been working continuously on this group since 2007 or so and have been especially interested in their ecology, functional anatomy and evolutionary relationships. The finding of a new azhdarchoid in the Lower Cretaceous rocks of the Isle of Wight thus combined several of my special interests.
Where and how did you find the new fossil described in your study?
Most Cretaceous Isle of Wight fossils come from a rock unit termed the Wealden Supergroup. The new specimen – we’ve called it Vectidraco – is from a different, younger unit called the Atherfield Clay Formation, and as such it’s (so far as we know) only the second pterosaur reported from this unit.
I should say that the discovery of Vectidraco itself is interesting in that the find was made by a young girl, Daisy Morris (aged just 5 at the time!), while she was on holiday with her family. Daisy’s family wanted this fossil to be studied and cared for properly, so they did what I and many of my colleagues would say is “the right thing” and donated it to The Natural History Museum in London. So, we only know of Vectidraco thanks to Daisy: for this reason we named it in her honour. It’s full name is Vectidraco daisymorrisae.
What was previously known about this group of flying reptiles, the azhdarchoid pterosaurs?
So far as we know right now, azhdarchoids are unique to the Cretaceous period (that is, they were alive between about 145 and 66 million years ago) and all were toothless. They’re actually a pretty diverse group of pterosaurs, with some – like the tapejarids – being relatively small, withwingspans of about 3 feet or slightly less and others – namely the azhdarchids – being gigantic, withwingspans of more than 32 feet.
Tapejarids have short, deep snouts while azhdarchids have incredibly long, pointed jaws, and other kinds of azhdarchoid were intermediate between these two groups. Particularly good azhdarchoid fossils are known from South and North America and China, but their remains have been found right across Europe, Asia and Africa too.
Working out what azhdarchoids did when they were alive has been one of the great questions about the group, but it seems that they were mostly omnivores or carnivores that lived in terrestrial environments.
The paper describes the new fossil as “small-bodied”. How much larger are other known pterosaurs of this kind usually?
Azhdarchoids span a diversity of species that range from ‘small-bodied’ all the way up to gigantic. The biggest kinds – like the famous Quetzalcoatlus from Texas – were something like 10 feettall at the shoulder and over 450 pounds heavy while small ones, and Vectidraco is one of them, had wingspans of just 30 inches or so and would have been similar in size to crows or gulls. I would say that Vectidraco belonged to an azhdarchoid group where small size was normal and widespread, with large and even giant size evolving in other azhdarchoid lineages.
How did you determine that the new fossil belonged to the same group as these other specimens?
Vectidraco is known only from its pelvis, but even with only a pelvis to go on, we could see several features of the new specimen that made it especially azhdarchoid-like, mostly to do with the weird anatomy of the big, T-shaped bony structure that projects upwards and backwards from the rear part of the pelvis. In an effort to better test the idea that Vectidraco is an azhdarchoid, we included it in a few different phylogenetic analyses and it came out as an azhdarchoid in these too. It also has several unique features, not seen in any other pterosaurs, and for these reasons we were able to name it as a new species.
How does this discovery change what we know about this group of pterosaurs?
We’ve known for a while that small-bodied azhdarchoids lived in western Europe during the Early Cretaceous: a new species called Europejara olcadesorum was described in PLOS ONE last year. Now we’ve found that Vectidraco lived in the same region during the same period, so we’re seeing a pattern: small-bodied azhdarchoids were living alongside longer-snouted, small-bodied pterosaurs and also alongside large, toothy kinds called ornithocheiroids.
This is essentially the same kind of pterosaur community that we see in Chinese rocks of the same age – the great difference is that the Chinese fossils are relatively numerous, and frequently preserved as complete or near-complete skeletons. In fact, one of the things that we comment on in our paper is the fact that western Europe’s pterosaur assemblage looks far less rich than that of China due to differences in the way these fossils were preserved. Chinese pterosaur and small dinosaur fossils were buried rapidly by volcanic ash and hence preserved whole, while those of western Europe were usually broken apart on floodplains, extensively scavenged, and eventually preserved in fragmentary form.
The western European and Chinese assemblages might actually have contained similar sorts of species, but the conditions local to both places meant that their fossil records ended up being very different.
Read more about this exciting new fossil at Darren Naish’s own blog, Tetrapod Zoology.
Citation: Naish D, Simpson M, Dyke G (2013) A New Small-Bodied Azhdarchoid Pterosaur from the Lower Cretaceous of England and Its Implications for
Pterosaur Anatomy, Diversity and Phylogeny. PLoS ONE 8(3): e58451. doi:10.1371/journal.pone.0058451
Vullo R, Marugán-Lobón J, Kellner AWA, Buscalioni AD, Gomez B, et al. (2012) A New Crested Pterosaur from the Early Cretaceous of Spain: The First European Tapejarid (Pterodactyloidea: Azhdarchoidea). PLoS ONE 7(7): e38900. doi:10.1371/journal.pone.0038900
Images: Specimen and speculative reconstruction of Vectidraco from 10.1371/journal.pone.0058451, Life restoration of the head of Europejara from 10.1371/journal.pone.0038900