STL Science Center

STL Science Center

22 February 2017

Turtle Anatomy

As mentioned yesterday, there are two major divisions of turtles aside from binning the animals as freshwater, marine, or tortoise. There are other aspects of the anatomy of Stupendemys that are just as important as the way which it retracted its neck and head. Most of the anatomy that has been described is related to the shell of the turtle as the enormous shell was most readily preserved and fossilized. Additionally, materials such as the humerus, pelvic girdles, and an incomplete set of vertebral elements have been found and described. The "problem" with this turtle is that its anatomy is not that much different from modern turtles as to point out anything exciting or overwhelmingly primitive about Stupendemys. The turtle is remarkably enormous though, with the humeri measuring 310 cm and 340 cm in S. souzai and S. geographicus respectively.
Photo by Ryan Somma at American Museum of Natural History. CC BY-SA 2.0

21 February 2017

Types of Turtles

There are two types of turtles in this world, marine and freshwater notwithstanding: pleurodira and cryptodira. Pleurodiran turtles retract their heads into their shells by bending their necks in the axial lpane whereas cryptodiran turtles lower their necks and retract their heads into their shells. The majority of living turtles are cryptodiran turtles, but there are notable groups of pleurodirans as well. Stupendemys is one such notable member of the pleurodira. the anatomy of this system of hiding its head has been described in many papers, notably in Scheyer and Sanchez-Villagra 2007 and the slightly older de Broin, et al. 1993. The initial description of the turtle is not online; however, the description of the second species named, Stupendemys souzai, is available online. This is a good reference for not only the anatomy of the genus, but also general turtle anatomy, as modern knowledge of turtles is used to more accurately describe the fossil by the authors Bocquentin and Melo.

20 February 2017

Big Turtle, Little Star

There is an awful void of popular knowledge about Stupendemys. The name alone, meaning Astonishing Turtle, would seem to require more coverage than the turtle has received on the internet, in documentaries, or in movies and television. The giant turtle is shown some love in the amateur video sphere as more than one fossil enthusiast has dedicated some time to describing the turtle and sharing illustrations and other recreations in their videos. The most informational of these videos was posted by a user from the United Kingdom known as The Sarcastic Raptor who posts videos about games as often as videos about extinct animals. Enjoy his description and the images he has found for his video below.

19 February 2017

Fresh Prince of Turtles

Freshwater turtles are capable of growing to large sizes in some genera if allowed to continue to growing for along time and not killed at young ages. The past is littered with the remains of giant turtles, both freshwater and marine. One of the largest genera of these freshwater turtles was the turtle Stupendemys. Consisting of two acknowledges species (S. geographicus Wood 1976 and S. souzai Bocquentin & Melo, 2006), Stupendemys carapaces averaged 1.80 m (5.9 ft) long with the largest individual approaching an estimated 3.3 m (11 ft) long carapace; an estimate that makes this turtle larger than the largest marine turtle Archelon. These two species are of similar size with S. souzai being described as smaller and have both been recovered from South America; S. geographicus from Venezuela and S. souzai from Brazil. Thought to be an enormous grazer and terrible swimmer, it has been hypothesized that Stupendemys used its weight to control its buoyancy and keep it grounded in the vegetation of the calm slow moving riverbeds it would have inhabited. There are hypotheses that the habitat of the turtle may have lacked significant predators, allowing the animal to reach the sizes that it did, but regardless of the validity of these hypotheses, this was an enormous turtle as we can see below with this replica carapace:
Unattributed photo found online

18 February 2017

Giants of the Lost World

Donald Prothero has taught multiple generations of paleontologists, biologists, and science enthusiasts in his 35 year career. He has written more papers and books than I can count and I, along with many others in the field, have read a great deal of his work over the years and know his contributions to the field quite well. I was recently offered the opportunity to read and review his latest book, Giants of the Lost World: Dinosaurs and Other Extinct Monsters of South America (Smithsonian Books, 2016) and I am quite honored to share my impressions of the book with all of you here today.

I am a big fan of art and figures in scientific books and so the first thing that I do with any book is check out the cover and thumb through the illustrations. This book, from the artistic standpoint, does not disappoint the modern reader. Images are clearly captioned and placed in appropriate places in coordination with the narration of the book. Photographs, reconstructions, and supporting graphics (phylogenetic trees, maps, etc.) are all black and white, save 16 color plates which also include computer generated models of some taxa. These illustrations are high quality, modern scientific interpretations of extinct animals which, for readers that enjoy visuals when they read scientific books, enhance the reader's understanding of the worlds that are being discussed in this book. What's more, the book's sources for illustrations are taken, often, from the internet; an innovative approach to sourcing illustrations.

I say worlds in reference to the illustrations rather than "the world" because the narrative of this book is not simply the history of South America, but the history of the lands that South America bordered, touched, and influenced (or has been influenced by) in terms of both flora and fauna. Additionally, global extinctions are discussed at the global scale, as they should be. The treatments of the debate over the modes and scopes of great extinctions like that at the Cretaceous- Paleogene boundary is intense with details of geology, biology, and physics explained that caused specific events to occur as we know them from the fossil record. The well laid foundation of historical events in the book is key to discussions of the flora and fauna of different eras and this history is very well detailed. The language of the history is scientific, but easy to approach for casual science enthusiasts like many of the readers of this blog. However, seasoned scientists can appreciate the professional language and how it is made accessible to not only scientists but also the general public in a manner that is professional and respectful.

The treatment of the animals in this books is likewise respectful and equal across taxa. A paleontologist focusing on fossil rhinoceroses and other mammals for a great portion of his career, one might expect Donald Prothero to be extremely biased toward the mammals that he discusses in the book. It is true that a good portion of the book does discuss mammals, their rise to dominance over the landscape, and the many different stages of their evolution; however, reptiles, dinosaurs, and birds receive considerable attention as well and there are even mentions of amphibians and marine life.

This book is written for a popular audience and discusses and describes extremely high level concepts in a manner that is accessible, fun, and well illustrated. The work is educational but entertaining such that it is an easy read. The chapters can be read as stand alone units but together represent a rich history of a continent, its animals and plants, and the world in which it is a part. This is a book that should be read by professional and casual paleontologists that love mammals, reptiles, birds, and the overall pursuit of more knowledge.

17 February 2017

Life Sized Models

A model of Nqwebasaurus existing somewhere in the world is inevitable. The fact that it is in South Africa should be of very little surprise given that the fossils were discovered there. This model pre-dates the knowledge of the ubiquity of feathers and as such is quite a basic scaly dinosaur, but feathers in theropods this basal have not been ruled out as entirely possible as yet. The anatomy described in the papers we read this week is evident in this model. The digits of the manus appear to be quite exaggerated; however, in looking at the fossil we can see that the digits are fairly elongated. Impressively, the opposable digit is very well modeled here, making the forelimb look that much more terrifying. Possessing feathers or not possessing them, the models and illustrations we have seen this week of Nqwebasaurus are all equally interesting and make this basal coelurosaurian look quite dynamic.
Photo by William De Klerk

16 February 2017

Famous Tongue Click

Nqwebasaurus is the only dinosaur with a name that includes a tongue click. It is also the only basal coelurosaurian from South Africa and one of the earliest theropods found in the entirety of the continent. These two reasons for popularity have fueled inquiry and interest in Nqwebasaurus but its name is difficult to say and spell, which has stalled some of the general popularity that the dinosaur has been subjected to or affected by (depending on your stance). The strange general popularity lack for this dinosaur even makes the illustrations of the dinosaur somewhat rare. There are interesting facts that are less well known about the dinosaur that could make it even more interesting or popular with the general (non-scientist) populace. One of these is the lesser stressed identification of possible gastroliths in the abdomen of the dinosaur, pointing to an herbivorous diet. Gastroliths are stones that are smoothed by mechanical manipulation in a muscular organ such as a gizzard or crop. These stones are used to grind tough fibrous foods so that an animal does not need to chew and rechew and chew its food again to break down the strong vegetation to get at the nutrients contained within.