STL Science Center

STL Science Center

24 February 2018

Gigantic Murderer

The Permian landscape was filled with enormous therapsids. As we have discussed in past entries (see Moschops), the therapsids are the group of synapsids that includes mammals and their descendants. During the Permian the group of therapsids known as dinocephalians were a small, but mildly successful group for about 10 million years (270 - 260 million years ago). Some of these animals were absolutely terrifying in appearance, possibly because they look like nothing currently living on the planet. One of the more alien looking, and named, dinocephalians of the Middle Permian was the 5 m (16.4 ft) long Titanophoneus potens Efremov, 1938. The name Titanophoneus translates to "Titanic murderer" and the large carnivore prowled the Middle Permian with an 80 cm (2.62 ft) long skull and teeth to match (in that they are huge, not 80 cm long).
©Dmitry Bogdanov
Titanophoneus & Ulemosaurus

23 February 2018

A Turtley Picture

A lot of images online are non-descript turtles; sometimes freshwater turtles manage to sneak into the search results for Desmatochelys. A number of unidentified, both artist and subject, turtles also appear, making finding an accurate interpretation as well as attributing that interpretation almost impossible in some ways. Regardless, a lot of turtle illustrations are really great, for a number of different reasons. The underwater lighting in most of these images that I have looked at today is wonderfully done, which further enhances the natural majesty of these giant marine turtles. Desmatochelys in action looks, no matter the artist, like many other sea turtles as they swim through the scene in which they are depicted. This version of Desmatochelys is fairly majestic, but has a few non-majestic characteristics as well (I think it might be the angle of the head).

21 February 2018

Turtle Bits Everywhere

The 2007 Colombian skeletons that were described by Cadena and Parham 2015 consisted of at least four individuals; four skulls that are either entirely or nearly entirely complete were among these remains. The holotype from this set of remains of Desmatochelys padillai consists of one of the incomplete skulls as well as portions of the neck (hyoid and vertebrae 3-8), both forelimbs with incomplete digits, the left shoulder girdle, and most of the upper (carapace) and lower (a partial hyoplastron and hypoplastron) shell. Two additional partial shells were also recovered in 2007. The remains constitute the oldest known marine turtle at approximately 120 million years old; the next oldest fossil marine turtle is an animal known as Santanachelys gaffneyi at 95 million years old.

These turtles were not tiny marine animals either. The Colombian fossils had heads that, at their largest, measured 320 mm (12 in) long and 216 mm (8.5 in ) wide (specimen FCG–CBP 01). The known material of the carapace of this specimen measured approximately 1660 mm (2.17 ft) long and 1353 mm (4.44 ft) wide. As we can see below, this was a rather large and impressive turtle.
©Edwin Cadena

20 February 2018

The Turtle Papers

The history of Desmatochelys is a very well-documented one, with many of the fossils described and analyzed a variety of ways. Some of these descriptions of course include Williston 1894 and Cadena and Parham, 2015. The Cadena and Parham article is fairly long and highly detailed and, thankfully for us, hosted online by the University of California system; the article appeared in PaleoBios which is published by the University of California Museum of Paleontology. A lot of this article discusses the phylogenetics of marine turtles and these sections are accompanied by enormous colorful figures and phylogenetic trees. Much of the discussion contained therein is the result of studies that came before Cadena and Parham, allowing these authors to make the inferences that they detail in their article. Many of those arguments and discussions were originally written by Elizabeth Nicholls in the early 1990's. Nicholls, 1992 detailed an incomplete specimen of D. lowi discovered on Vancouver Island on the Pacific coast of Canada. That specimen marked the first discovery of a marine vertebrate from the Cretaceous along the Pacific coast. In her discussion of turtle specimens Nicholls argued that more specimens of marine turtles discovered in Cretaceous rocks belonged to the genus Desmatochelys and her work on the turtles is inherent in the efforts and descriptions of later marine turtles and Desmatochelys specimens specifically.

18 February 2018

Turtle Facts

Desmatochelys is a somewhat popular turtle. Being the oldest known fossil sea turtle most likely only enhances the popularity of the fossil. However, the fossil has few fact pages and videos online. One of the only human-voiced videos on YouTube is the GeoBeats News video shown below. Enjoy the video today and tomorrow we will look at some of the other videos. Later in the week we will discuss some of the facts that we know about Desmatochelys, where they came from, and how we know what we know.

17 February 2018

The Oldest Sea Turtle

©Jorge Blanco
Desmatochelys is the oldest sea turtle known to science. Consisting of two species, D. lowi Williston 1894 and D. padillai Cadena and Parham, 2015, Desmatochelys is known mostly from Colombian fossils of D. padillai recovered in 2007. However, D. lowi is known from a very well preserved specimen from Nebraska described by Williston in 1894 and potential remains recovered from Kansas in 2008. The reason that the 2007 discoveries and their 2015 description are more well-known is because they are more current, very well preserved, and the description includes an extensive list of characters and depth. All of the known specimens of this turtle genus are amazing, so it really is difficult to say any one is better than the other specimens and each has its merits. As an example, the 2008 Kansas specimen of D. lowii has a very well preserved skull and the humerus is slightly different from Williston's Nebraska specimen of 1894. Variance, preservation, and preparation could account for this, however we may never know exactly why they appear different.

Regardless of their preservational states, the specimens of D. padillai from Colombia was recovered from rocks that are Lower Cretaceous or upper Barremian-lower Aptian, approximately 120 million years old, in age. These fossils make Desmatochelys the oldest known fossil sea turtle by approximately 25 million years. All of the fossils, from all three locations, make Desmatochelys one of the most well represented fossil sea turtles as well. As the week goes on we will list out the specimens and describe this turtle. Today, enjoy this Cretaceous landscape and its giant sea turtle.

16 February 2018

Giant Skeletons

One of the best skeletal reconstructions I have ever seen is that of Futalognkosaurus as illustrated by Nima Sassani. The image is enormous and I am going to link it here rather than describe the image in great detail. Enjoy this enormous dinosaur and its enormous skeleton.