STL Science Center

STL Science Center

12 July 2019

Week of Moving

When Keichousaurus came across my screen the first time I thought it was an impressive appearing nothosaur but that it had a funny little head. Then I realized everything about this aquatic reptile was small, and a little funny. Its rudimentary flippers still appear to be mostly pes and manus, rather than true flippers, and its elongate neck with a short faced head is almost somewhat comical. Most of these fossils are found as entirely complete animals. Their intriguing morphology and the completeness with which they are often found, as well as the fact that specimens are not much longer than 2.7m (and many smaller specimens are known), Keichousaurus fossils are highly sought after as attainable collector's pieces. Though their abundance makes this possible, it does not necessarily make it acceptable. The variation of known fossils is, as with any animal group, appreciable. The morphological variation that has been lost due to the sale, or simply retention by finders, of these fossils to collectors hurts population studies as well as our knowledge of the evolution of aquatic reptiles overall. However, we do know a lot about Keichousaurus, as this WizScience video shares:

06 July 2019

Returns and New Beginnings

I am back to having the time to write a little bit here and there every day. There are many good animals to start with as we restart these (mostly) daily entries. I decided that, since this is the restart of this blog we should go back to the roots of the roots of the first project I worked on after the inception of this page. The only way that makes sense is to talk about an animal that is a member of the group that gave rise to the animals that I originally worked on. My first project was describing a set of plesiosaur vertebrae, and the animals that preceded the plesiosaurs were a group that we call the nothosaurs. One genus, Keichousaurus (consisting of K. hui Young 1958 and K. yuananensis Young 1965), was first discovered in China in 1958 by Hu Chengzhi and described by C. C. Young. This genus, like other nothosaurs, possess a long neck and tail, short head (relatively), and paddle-like hind and forelimbs; the forelimbs being more paddle-like were thought to be more important in locomotion than the hindlimbs. This locomotion was also thought to resemble that of plesiosaurs and has been described as "underwater flight", though this is still largely hypothetical at present. The holotype species (K. hui) is represented by numerous fossil animals, including pregnant individuals indicating live birth or ovoviviparity (hatching in the uterus and being "born" live) in Keichousaurus.

We might think these animals would be quite large, given that their plesiosaur descendants are quite large animals. However, many of these nothosaurus are extremely small, ranging from 15-30 cm (6-12 in) in length. There are individuals known to reach 2.7m. Despite the long neck and tail that we see in illustrations of Keichousaurus, that long neck is actually quite short, in respect to what we usually think of for long-necked animals (think of giraffes and long-necked dinosaurs, as examples). Of course, that neck is relatively long for these small animals!

©Nobu Tamura

09 February 2019

Fancy Pets

The "Mexican Walking Fish" (Ambystoma mexicanum) is probably one of the first non-mammalian animals that I ever interacted with (aside from actual fish) in an extended capacity. My mother was tasked with feeding the Ambystoma in one of Indiana University Bloomington's biology research labs back in the late 1980's. This is also where I first hung out (I was maybe 8 so "was tolerated" may be a better description) with graduate students and learned how to play Tetris, but those are stories for another time. We generally do not call Ambystoma Mexican Walking Fish, which is good because in the traditional nomenclature sense they are actually salamanders and not fish at all. Most know them as those strangely adorable pink aquatic pets known as Axolotl.

The story of Axolotl is amazing, endearing, and almost somewhat ridiculous; but we are not going to learn much more about Axolotl today as they are a means to an end for us here. I will share that they love uncooked beef liver. Also, I was inspired to talk about them today because a friend that works at the Boston Museum of Science shared a post about an upcoming exhibit featuring these adorable little salamanders. Salamanders in general are fairly recognizable by most, though there is sometimes confusion over names (e.g. newt vs. salamander) and appearance (think Axolotl vs. any other generic "salamander" that comes to mind). We could discuss how newts are salamanders and why Axolotl look different from Tiger Salamanders (which they are closely related to), but we are going to talk, now that we all have a picture of salamanders in our heads, about fossil salamanders from the Permian known as Apateon.

Senckenberg Museum of Frankfurt
Photo  by Ghedoghedo

Often preserved as flat impressions on slabs, these Permian temnospondyls are primitive amphibians that, like the Axolotl, are neotenic; meaning that they retain juvenile traits, such as the external gills seen in Axolotls, in their mature adult forms. This is often referred to as pedomorphosis also. Researchers have shown that these traits are retained in large numbers of these animals and they were so populous that we have a wide swath of ontogenetic or life cycle examples of animals in this genus to show that we are not just looking at odd young from many different groups. We have, of course, living examples to draw from as well. Many interesting things are known from these fossils, but probably one of the most intriguing things, to me, is the number of large group fossils and the detail in both the large group fossil assemblages and single animal fossil slabs that exist for Apateon. The genus Apateon actually consists of 7 species with Apateon pedestris von Meyer 1840 containing the holotype for the genus. As with many exquisitely preserved slab fossils, Apateon was originally discovered in Germany, a country with a rich history of excellent freshwater fossil diversity and preservation, and specimens have been dated from 295.0 to 290.1 million years ago.

Apateon pedestris Natural History Museum, Bonn University
Photo by Ghedoghedo

The skeleton of these Permian amphibians can be seen in this image from the Natural History Museum of Bonn University, which is actually quite a feat. The skeletons of Apateon are very weakly ossified, so the identifiable vertebrae, ribs, and limbs are truly exceptional and speak directly to the preservation of the fossil. Additionally, the orbits are fairly identifiable and, because we can see where the eyes would have been, we can see that the snout and the area of the skull directly caudal, or behind the eyes, are very short. We can say that Apateon had a very small head rostrocaudally (front to back) but also a very wide skull and very large eyes. If we turn our attention to those limbs we can just make out the digits. We know from more splayed out fossils of the limbs that there were four digits on the forelimb (on the "hand") and the hindlimb as well.

02 February 2019

Groundhog Day

In 2014 a fossil skull from Madagascar introduced us to a "groundhog-like" mammal of the Late Cretaceous. The animal was named Vintana sertichi in Krause et. al, 2014. This mammal was estimated to weigh approximately 9.1 kg (20 lbs) and was relatively short, as we can see in Nobu Tamura's reconstruction below. Flanges found in the skull are not well understood and appear to have no homologous structure in modern relatives, but their purpose could still be discovered with more discoveries of the fossils or further investigation into the family as a whole. Regardless, the endocast of the brain did reveal very large olfactory bulbs. We know from this that Vintana had a good sense of smell and likely used this trait actively and frequently in its normal day to day life. It may seem that a single skull of a small mammal is not that important, however, mammologists and mammal paleontologists think this skull is pretty amazing. The reason that they feel this way is because this fossil skull represents possibly the best preserved skull of any gondwanatheres; a group of southern hemisphere cynodonts that lived from the Cretaceous to the Miocene. Actually, another interesting facet of Vintana is that, though it was discovered in Madagascar off the east coast of the African continent, it belongs to the mammalian sudamericidae family which translates literally to the South American family of mammals. In fairness, a largenumber of gondwanatheres belong to this family and have been discovered in Africa, making Vintana not the first and probably not the last
©Nobu Tamura

19 January 2019

Animals Not Often Known

This week I decided that we really ought to get a little bit of knowledge into an odd group of animals that we have never looked at before. We have explored a lot of marine animals including fish, mammals, and reptiles. There is a set of aquatic mammals that we have not yet explored. This group of marine mammals is known, largely, today as the "sea cows." One of the genera that best represents the group is a globally known genus called Metaxytherium. The genus Metaxytherium consists of 8 species (M. albifontanum Vélez-Juarbe and Domning, 2014; M. arctodites Aranda-Manteca et al., 1994; M. crataegense Simpson, 1932; M. floridanum Hay, 1922; M. krahuletzi Depéret, 1895; M. medium Demarest, 1822 (type species); M. serresii Gervais, 1847 and M. subapenninum Bruno, 1839) represented from the Miocene into the Pleistocene. Dugongs, the family (Dugongidae) of organisms to which Metaxytherium belongs, is a capable of living in both marine (salt) and freshwater systems and Metaxytherium was not an exception with taxa being discovered in both coastal and inland fossil deposits. Metaxytherium looks, skeletally, very similar to extant manatees and dugongs; you can see the skeleton of M. floridanum below.
Photo by Ryan Somma

05 January 2019

Fossils and Parrots

When one searches fossil parrot two things appear. One is a report of a partial tarsometatarsus (a bone in the foot) from Siberia that was dated to 16-18 MYA. This is interesting, but it is a very small part of a parrot. A proto-parrot from Wyoming also appears regularly in the search list. This animal, shown below, does not have the familiar head shape of parrots, but does possess other features of parrots and is a whole bird; though it is in the typical bird state of a fossil which is to say that it is nearly pressed entirely flat. This fossil comes from the Fossil Butte Member of Green River Formation and has exceptional preservation, despite the crushed nature of the fossil. If you were to look closely at the neck you can see tracheal rings, the cartilage circles that keep the trachea ("windpipe") open so animals can breathe. Other fossil parrots are known to science, but many of them are associated with much older discoveries, so the papers describing these finds are not high on the search returns. These include parrots found in the Miocene of Nebraska (Wetmore 1926), New Zealand and Australia (latest paper: Worthy et al. 2011), and the Czech Republic (Mlíkovský 1998). There are other papers describing fossil parrots as well, but some describe the same finds mentioned above or are reviews of what we know about the parrot fossil record.
Cyrilavis colburnorum photo by Ian N. Cost

24 December 2018

Enjoy some Images

Today, enjoy some imagery of Temnodontosaurus. Also, enjoy some toy reviews. The second video is a model from CollectA and is particularly interesting as it includes a pup in the process of being born; it is admittedly a little odd.

Also enjoy this short clip that is said to portray Temnodontosaurus. Because there are not a lot of Temnodontosaurus videos, definitely spend some time checking out this cartoon about Mary Anning as well.