STL Science Center

STL Science Center

20 August 2017

Mega Facts

Megalibgwilia is an unusual animal for a variety of reasons. Some of these reasons are detailed in the facts that are know about the animal and shared on various websites and fact pages. There are a number of sites we have used before and many that many among us may have never heard of before that host files, short essays, and illustrations of the two species of this genus. The first of these familiar sites which appears in a search is the Dinopedia. Despite this animal clearly being a monotreme, a type of non-placental mammal now represented by only extant echidnas and the Platypus, the Dinopedia entry is fairly comprehensive and discusses Megalibgwilia almost identically as sources like Wikipedia. This makes it neither more nor less useful than Wikipedia of course. Wikispecies entries for the animals are taxonomically useful, but again, this information can be found in Wikipedia as well. A slightly more detailed history of taxonomy is available on the Fossilworks site which also provides some locality details for known fossils as well. One of the most interesting new sites is the Australian Broadcasting Corporation's site discussing the extinction of megafauna in Australia. While it does not specifically discuss Megalibgwilia exclusively, this site does discuss the environment it lived in and how it may have been subjected external and internal pressures leading to its extinction.

19 August 2017

Monotreme Party

In looking for  new animal this week we are going out of our normal range and into the time of the mammals. Becoming extinct approximately 50,000 years ago during the Pleistocene, the tachyglossid (a group that includes the extant genera of Echidnas) Megalibgwillia consists of two species, M. ramsayi (Owen, 1884) and M. robusta (Dun, 1896), and represents the oldest known echidna genus found. Both species are often referred to as the "giant echidna" but recent evidence shows that they are approximately the same size as the largest living echidnas rather than immense fossil animals, respective to extant echidna. Both species are represented by largely complete fossils and, because we know basically what the animals looked like, we can state that they were most likely as bizarrely intriguing as extant echidnas.

17 August 2017

Somewhat Well-Known

Conchoraptor has made a larger impact than many other dinosaurs. It is still not a widely known dinosaur, but it is known throughout the dinosaur community to a greater extent than many other dinosaurs. Conchoraptor is a dinosaur that is more well-known online than it is in most other media. It has appeared in books, illustrations, and has been featured in a few privately made tribute videos, but it does not appear in any games, movies, or documentaries. Having little to share in the vein of popular culture, there is at least a single private video that can, and is, shared here to show a variety of illustrations of Conchoraptor. As always, remember that these videos sometimes mislabel taxa unintentionally and that some of the images may not represent Conchoraptor as well as others. These images are open to interpretation as well.

16 August 2017

Feathers and Genders

At least one site mentions that Conchoraptor remains have been discovered with attached feathers. These feathers have been described sparingly, but have been described as sexually dimorphic characters of Conchoraptor. Sexually dimorphic characters are typically most reliable in adult animals. The assumption with the assertion that the feathers represent dimorphism is that they most likely came from adult specimens. One of the hypotheses of discerning adults from juveniles and sub-adults in Conchoraptor is less concerned with feathers and sexual dimorphism and more concerned with the crest on the cranium. Most oviraptorids possess a large crest along the midline of the skull that is larger rostrally than caudally. The original material lacks a crest entirely and remains recovered later also appear to lack crests or possess very minimal crests. The hypothesis that crests grew as the dinosaur aged are not abnormal or new, but without known fully adult specimens possessing full crests, we can neither, as yet, support nor refute that hypothesis. However, if evidence comes to light to fully support this and the hypothesis concerning dimorphism and feather morphology, then we will know a lot more about the life histories of these animals.

15 August 2017

The Brains and Skulls

Brains and other soft tissues are of great interest to scientists in extant and fossil specimens. There are a variety of ways to study organs in extant specimens and many of those methods can actually be applied to fossil specimens as well. Many of the methods used to investigate fossil soft tissue systems originate in studies of the soft tissues of extant organisms. These are systems that we can readily devise methods for and test out the methods on. Interpretation of the results can be compared with observations of behavior and organ use in extant animals as well. These model organisms and their organ systems allow for inquiries into similar systems in fossil animals. These steps result in studies such as Kundrat 2007 which looks at virtual brain models of Conchoraptor derived from CT scans of the skull. The scans are used to create virtual endocasts, or models of the negative space of the skull where the brain would have been in a living Conchoraptor. Endocasts show scientists potential lobes of the brain (assuming that the skull retained its original dimensions during the fossilization process). Kundrat 2007was able to identify characteristics of the brain that Conchoraptor appears to have shared, or at least approximated, with the brains of birds. Additional studies of the skull have been undertaken which look at other organ systems of Conchoraptor and use some similar methods. Kundrat and Janacek 2007 explored the hearing capabilities as well as the structure of the skull of Conchoraptor. They described pneumatization and sinuses of the cranium (another avian-like feature). This study also described and analyzed the bones surrounding the tympanum (eardrum). Recesses in the bone helped to describe the tympanum itself as well as the different portions of the ear. Specifically, Kundrat and Janacek were able to describe distinct proportions and geometry of the inner and middle ear of Conchoraptor and infer the hearing capabilties of the dinosaur.

13 August 2017

The Video File

There have been, as we have gotten more and more into the lesser known dinosaurs, fewer and fewer resources available at any given time. This has been related to the popularity of given dinosaurs, of course, and has not really made our job any easier when it comes to sharing interesting and new sources. However, we have a stable of consistent and helpful resources that we can typically fall back on that are reliable and accurate, which are far more important than new and interesting. For that reason, rather than posting a small number of websites all sharing the same basic information about Conchoraptor today, I would much rather share a single video, produced by WizScience, that summarizes all of those pages and does so over a series of illustrations and photographs.

12 August 2017

Shell Stealing Dinosaurs

Known from the Nemegt Formation of Maastrichtian soils of Mongolia, specifically the Red Beds of Hermiin Tsav, the conch stealing oviraptorid Conchoraptor gracilis. Barsbold 1986 described a partial skeleton and skull of an oviraptor which, like its cousins also discovered by Barsbold and the Polish-Mongolian expeditions of the 1970's, is a victim of the hypotheses of many scientists that the oviraptorid dinosaurs were stealing eggs rather than incubating eggs. The name Conchoraptor reflects Barsbold's hypothesis that the animal's lack of dentition was indicative of a diet that was rooted in mussels and other shellfish rather than eggs. This dietary hypothesis was unpopular at the time, though we now know that oviraptors, whether they fed on mussels and clams or not, were not feeding on the eggs that they were found with.The lack of crest, seen in this representation of the skull, is thought to have been a result of immaturity in the described holotype. This hypothesis will be explored during the week as we explore Conchoraptor.
©Jaime A. Headden
Creative Commons Attribution 3.0 Unported

10 August 2017

Fish Foods

©Florida Museum of Natural History
It has been determined, or rather hypothesized, that Enhydritherium had a mainly piscivorous, or fish-based, diet. This was based on the fact that Enhydritherium possessed bones in its front paws that are more similar to extant fish catching otters than to its ancestors which are thought to have lived on land and did not eat fish regularly. Modern fish catching otters use their mouths to catch their prey whereas the ancestors of Enhydritherium used their hands to catch and grab food items; this means that the hands of Enhydritherium and modern otters are not as adept at grasping and handling food items as their ancestors. Enhydritherium also possessed large attachments for neck biting muscles and, as a direct relation, probably had extremely large and powerful neck muscles. These would have been used to attack prey quickly and hold them as the otter then left the water to secure and feed on its fish prey. These neck and biting muscles were very important for Enhydritherium because it was not capable of chasing its food in the water. Poor swimming adaptations in the hindlimbs made Enhydritherium good at wading into water and escaping from the water, but unable to chase aquatic prey. The hindlimbs of the animal were much more adapted to terrestrial locomotion. As such, it was capable of long overland journeys like that which Tseng, et al. 2017 describes as a hypothesis of migration between the bicoastal populations of Enhydritherium.

08 August 2017

Otters and the Ocean

Due to being found near a coast and looking like their extant descendants, Berta and Morgan's initial description of Enhydritherium was heavily angled toward portraying the skeletal remains as those of a large ancestor of modern otters. Their description was not wrong, of course, and Enhydritherium is known to be one of the largest otters, fossil or extant, that has been recorded. As a large sea mammal Enhydritherium has garnered attention throughout the time that it has been known to science. This has led to a number of studies describing different aspects of the animal's life history. The most all encompassing study discusses, describes, and analyzes the osteology of the otter in order to describe its paleoecology; Lambert 1997. This is a fairly typical order of events in describing fossils and the world in which they lived that, in turn, allows for inferences concerning the interactions of this particular species both intra- and inter-specifically. What helps even more, of course, is the discovery of additional remains. Depending on how and where the remains are recovered, new answers can be found to old questions or new questions can be developed. In the case of the Mexican dental remains that we have seen earlier this week, old hypotheses have been refuted and new hypotheses generated concerning the movement of this otter. Tseng, et al. 2017 refutes old hypotheses of migration that include Arctic and Central American Seaway dispersal of Enhydritherium between what are now Florida and California. A lack of fossil evidence from either region is deemed troubling as supporting evidence of such migratory routes. However, the trans-Mexico route does possess fossil remains and, with a skeleton that appears to support terrestrial travel over long distances, also seems suitable for Enhydritherium.

07 August 2017

News and Finds

Furry extant otters are often described as adorable, mischievous, and sometimes simply with the word "awwww." The newest discovery of Enhydritherium fossils could possibly be described using those adjectives, but likely there is nothing that most people would find adorable about the teeth discovered in the Mexican wilderness. However, those teeth were the diagnostic element of the fossil that identified the animal for the crew. As Dr. Jack Tseng recounts, he recognized the teeth as carnivoran and another member of the field crew recognized the teeth further as belonging to an otter. Rather than summarize everything that he has told reporters, though, everyone should watch this video instead.

05 August 2017

Amazing Otters

Fossil mammal make appearances here from time to time. This week is one such time when mammals will be featured exclusively. Known from sites in California, Mexico, and Florida, and described initially in 1985 by Berta and Morgan from a Floridian specimen, Enhydritherium terraenovae was a North American otter dated from approximately 9.1 to 4.9 MA. The majority of sites where this otters fossils have been recovered are in Florida, but the newest discovery was made in the Juchipila Basin of Central Mexico. This find suggests that these otters not only successfully lived on both coasts, but that they may have migrated between the coasts as well. Unlike extant otters, Enhydritherium was not yet particularly aquatic, which enabled the animal to conduct movements across expanses of dry land in ways that extant otters would find both improbable and, most likely, impossible. Not many interpretations of this large otter, an estimated 16 kg (35 lbs), exist; however, its skeleton suggests that it already had a "weasel-like" body plan and was elongated, compact, and close to the ground. It may have appeared very much like Potamotherium but was likely more stocky and larger than this more recent member of the otter family.

04 August 2017

Interesting Interpretations

Figure 1: Old school Melanorosaurus herd with gracile forelimbs.
©Zdeněk Burian (1905 — 1981)
As an early sauropodomorph, Melanorosaurus has been treated in many illustrations as a proper sauropod. In a few illustrations it has been treated more as what was once properly called a prosauropod; meaning that it showed Melanorosaurus as a sauropod-like animal with more gracile forelimbs which look as though they may have been capable of reaching for food and potentially grasping items (Figure 1). Unfortunately, this is less likely than a more sauropod-like body plan. The Natural History Museum of London features an illustration that portrays Melanorosaurus as a stereotypical sauropod with a body shape similar to a diplodocid; . We would assume, with this interpretation, that the back possesses a hump of fat in the middle portion. That, of course, is not unrealistic, as it has occurred in extant and fossil animals numerous times. The kind of back shape that we expect from the skeletal reconstruction, without a hump of back fat, is well represented by Josep Zacarias' black and white illustration of Melanorosaurus. I have a number of favorite illustrations of Melanorosaurus that show varied amounts of the back fat hump; both the lean and fattened versions of the animal are acceptable and offer their own interesting versions of the potential life history of Melanorosaurus. However, the most interesting of those images, to me, is John Conway's image of a herd at a drinking hole. The animals possess neck wattles not shown in other interpretations and are portrayed in various postures across the image and in all plains of the image. A couple in the background are even rearing up on their hindlimbs. The scene has a lot of little activity in it in all corners.

03 August 2017

Anatomy and Popularity

Some may have noticed that in the past few weeks I have missed days of writing now and again. These missed days are intended and do not in any way attest to a lack of interest in subject matter or the continued existence of this work. They do reflect the amount of time available to me to write on some days but more likely than not, they are related to the amount of information in existence online or in my personal print library available on any given species of fossil animal. Melanorosaurus, for example, is an animal with fewer links, videos, and mentions in the literature than an animal like Tyrannosaurus and some days the information to be presented is less than is optimal for a stand alone entry.

©Scott Hartman
Melanorosaurus has gained some popularity in recent years. Many illustrations, commemorative stamps, and a number of videos (including one in Spanish) have been designed, created, and released that feature Melanorosaurus. The low number of fossils that have been recovered have not hindered entire skeletal recreations either; this is the case for the majority of fossil species of course as many animals are reconstructed and illustrated with hypothesized skeletal elements inferred from related or at least similar species. Hypothesized skeletal reconstructions are more informative when they include a representation of the known fossil materials, such as that shown here.

01 August 2017

On Paper

A big year for Melanorosaurus recently was 2007. In that year both the forelimb and the first complete skull of the early sauropodomorph were described using new methods and new technologies. These new papers are not readily available online, but with a little digging they can either be found or the volume containing them can be purchased. The skull and forelimb papers both, for instance, are available via Wiley as individual articles in a larger publication that can be purchased at this link. The price tags on scientific literature are always a little higher than many other publications; despite what it looks like, that is actually not a terrible price. There are books that can be mostly read online (and are also available for purchase) that contain Melanorosaurus descriptive articles. The postcranial specimens that have been designated as members of Melanorosaurus are described by Galton, et al. in the 2005 book "Thunder-lizards: The Sauropodomorph Dinosaurs" and much of this chapter is free to view through Google books. There are missing pages, as there are with many Google books, but typically these are illustrations, graphs, or other figures and not too much text is missing; lost content is unfortunate either way of course. Melanorosaurus continues to be a heavily studied animal outside of textbooks and special publications though. There have been osteological studies published in the Journal of Vertebrate Paleontology abstracts (stemming from a conference presentation).

Possibly one of the more important papers for Melanorosaurus in the past decade is de Fabregues and Allain 2016. This paper explores new material attributed to Melanorosaurus. In so doing, the authors revise the position a species of Melanorosaurus and name a new genus. Despite this paper being largely about splitting taxa, a lot is said about the genus and the anatomy of the dinosaur. This makes it very informative for our purposes this week.