STL Science Center

STL Science Center

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.

23 December 2018

Short on Facts

I always find it to be a little odd when there are few places to find facts on what should otherwise be a fairly well-known animal. Considering Temnodontosaurus' place in fossil finding history and its giant eyes, it ought to be a little bit more well-known online. However, aside from a few tribute videos and some animation tests, there are almost no videos online. There are also fewer fact pages than we would normally expect for such an important fossil animal. There is a short encyclopedia entry on KidzSearch (a site we have not used lately) and a very slightly longer entry on the Ancient Animals Wiki. A more informative source of information that includes a slightly more in depth article and a list of facts can be found on Prehistoric Wildlife, a site we have found useful to learn from for a long time around here.

22 December 2018

Celebrating Lyme Regis

©Dmitry Bogdanov
The holotype of Temnodontosaurus platyodon (originally Ichthyosaurus platyodon) is approximately 6.1 m (20 ft) long and was discovered in 1821. Although the name means "cutting tooth lizard" the fossil is best known for two radically different reasons. The first is that the orbits and the 25 cm diameter sclerotic rings indicate that the eyes were approximately 20 cm (8 in) in diameter, making these the second largest known eyes in any animal. Prior to a 2008 dissection of a rare Colossal Squid (Mesonychoteuthis hamiltoni) which has eyes approximately 27 cm (11 in) in diameter Temnodontosaurus had the largest known eyes. The second most important reason that Temnodontosaurus is well remembered is because this large ichthyosaur was one of the first fossils found by Joseph and Mary Anning in 1811; it was initially described as a crocodile. Joseph outlived Mary by a few years, but Mary was the true force in the family fossil collecting business despite being largely deleted from the literature of the time by the geologists to whom she sold her fossils. Anning also led geologists (including Buckland, Agassiz, Owen, and Conybeare among others) on expeditions, taught them how to collect fossils from Lyme Regis, and trained their field assistants and wives how to collect fossils. Temnodontosaurus may be well known for being discovered by the Annings, having large eyes, and being one of the first known ichthyosaurs, but it is not the best known of Anning's discoveries; that distinction belongs to (depending on who one asks) either her 1823 discovery of Plesiosaurus, or her 1828 discovery of what later became known as Dimorphodon. During this week we will talk a little about Temnodontosaurus and Mary Anning both every day. The reason for that, for those interested, is that many of Anning's discoveries were made or published during December and her life was actually strangely influenced by the month. Additionally, it was recently announced (14 December) that a movie based on part of her life, titled "Ammonite" will begin production in March 2019. Anning and December seem intertwined and Temnodontosaurus was her first big find. It all goes together for a fitting end to the year.

Also, I just realized this is blog post #2500. Hooray!