Frog Prince(ss) of Popularity

Living permanently in water, Palaeobatrachus was the kind of frog that people often think of when someone suggest that they imagine a frog going about its daily routine; this or a similar idea are common things in kindergartens worldwide, I promise. This, in coordination with its revival as a cartoon character on a popular children's series and numerous entries in scholarly papers as well as short texts on frogs (such as Tertiary Frogs from Central Europe). Scholarly articles and cartoons alike appear to be enough to make this fossil amphibian popular enough for it to continue to be well known and widely distributed in image, text, and even video online.

The Lungs of Frogs

The typical lungs of your average frog are similar in general shape to the lungs of other terrestrial vertebrates in that they appear as lobes of soft tissue at the end of a trachea. They are also similar in function as they allow for blood and air to interact allowing for gas exchanges within the organ itself in specialized structures called alveoli; frogs have a much lower concentration of these structures in their lungs than other vertebrates. The lungs of Palaeobatrachus were not too different from those of their descendants in function, but their morphology was considerably different. Whereas extant frogs possess centrally located lungs housed in the thorax, the lungs of Palaeobatrachus were located within the dorsal sides of their thorax. Extant frogs, of course, do not only use their lungs to breathe. Gas exchange occurs within the mouth (minimally) and cutaneously while submerged; frogs make use of dissolved oxygen in the water to exchange gases through their skin. It could be hypothesized that the dorsal lungs of Palaeobatrachus laid the groundwork for these centralized lungs and also that they aided in enhancing the development of the system of cutaneous respiration we see in extant frogs. Cutaneous respiration may have, at the time, been the main method of filling the lungs of Palaeobatrachus as well, meaning that the lungs were an added adaptive characteristic of this frog; there exist today many small terrestrial amphibians completely lacking lungs. Perhaps these lungs enabled the frog to take in a large amount of air before diving and stay submerged longer in potentially oxygen poor aqueous environments. The evolutionary history of amphibian lungs is far more complex than we have time for today, unfortunately, but there are many resources available to delve into this history.

Volumes of Frogs

The number of papers written about Palaeobatrachus is well more than enough for a book all on its own. There are papers from this year that mention Palaeobatrachus and compare it to other fossil frogs, but these are not the meat and bones of the literature that details the knowledge that we have on Palaeobatrachus. There have been many different descriptions, recently even, of new species of Palaeobatrachus. The most recent descriptions, from last year, are of species known as P. diluvianus and P. eurydices; these species do not appear in any mentions of Palaeobatrachus species lists. New descriptions of fossil frogs, however, are not the only studies that have been published about Palaeobatrachus that are interesting and have made significant impact on the study of these particular frogs and fossil frogs in general. A particular favorite of mine is Roček, et al. 2006 on tadpoles and gigantism in Palaeobatrachus juveniles. A second favorite that I would recommend reading is about the diet of Palaeobatrachus. Wuttke and Poschmann 2010 describes a lagerstätte fossil of an unspecified Palaeobatrachus species with fossilized stomach contents. Those contents were made of small fish that the frog clearly captured and ingested (i.e. fish that were eaten by the frog).

Short Dinosaur Train Day

Today there is only a single documentary/feature that shows Palaeobatrachus and discusses it. Dinosaur Train has an entire episode about the family venturing out on a camping trip that also features this central European frog. The family meets Patricia Palaeobatrachus during the middle of the night when they hear a strange and scary noise.

Ancient Frog Links

Palaeobatrachus appears in a number of links and on a number of websites that are helpful for children and other fossil enthusiasts of course. The links range from very easy and quick reads, such as the Dinosaur Train Field Guide (which actually reads the facts to you), to more difficult passages like those found on the Prehistoric Wildlife and Encyclopedia of Life pages. The Encyclopedia of Life pages are actually heavily stocked with information about the fossils, where they originated, and what we know about the life of the animal. Anyone wanting to skip a little reading, or having the facts read to them by the Dinosaur Train conductor, there are also videos dedicated to facts about Palaeobatrachus. The easiest to find, of course, is a short from Dinosaur Train featuring Dr. Scott Sampson, as seen below (the audio of the current version available has a little echo).

Fur to Frogs

©Nobu Tamura; released as Palaeobatrachus gigas

Palaeobatrachus is a genus consisting of at least two named species, P. occidentalis and P. robustus (with others being mentioned that we will explore later), of amphibian that appears in the fossil record from approximately 130 MA to 11.6 MA; Fossilworks reports a range of 70 MA to 9.7 MA and these disparate ranges will be figured out later this week. An early frog, Palaeobatrachus is known from central Europe. Specifically, Palaeobatrachus is very common in the freshwater fossils of Germany. Early frogs, Palaeobatrachus, was extremely amphibious and spent very little time out of water. A lot is know about the entire life cycle of Palaeobatrachus with all stages of life, egg, tadpole, and adult, having been recovered from Bohemian rocks. Changing temperatures and changes in available suitable water sources caused Palaeobatrachus to suffer a reduced range of habitat. This, in the end, forced the frogs into extinction as continual climate change and shrinking suitable habitat forced the frog into what would be a losing battle with other taxa and the environment.

Home Field

Megalibgwilia is known in parts of the world that are not Australia, but its popularity, in the form of common popular outlets such as books movies, websites, video games, and toys, appears to be entirely lacking outside of Australia. Websites, of course, reach well outside of Australia, but dedicated sites that we have not already shared and discussed are rare and do not add too much that we have not already shown concerning the giant echidnas. One of those few non-Australian based websites that share information about Megalibgwilia is Berkley's Museum of Paleontology website. This page more specifically discusses monotreme evolution, but Megalibgwilia represents an important step in the evolution of other echidnas. A lack of other sources aside, the popular entry this week is therefore ending abruptly and is shorter than usual.

Megalibgwilia's Elbow

W. H. Wesley, Humerus of M. ramsayi

Owen's original description of Echidna ramsayi, later synonymized as Megalibgwilia ramsayi, consisted entirely of a detailed look at the broken left humerus of one of the "giant" animals. Eventually crania and postcranial remains were added to the descriptive list for this single species. All of the descriptions of M. ramsayi have amounted to a fairly complete picture of this first species of the genus. The second species, M. robusta, was described by William Sutherland Dun in 1896 and consisted of mostly complete remains. Megalibgwilia robusta is the oldest known echidna and, despite being known as a "giant echidna", is slightly smaller than the largest known monotreme of Western Australian; Zaglossus hacketti. Contemporaries of Zaglossus, the two species of Megalibgwilia were geographically separated from one another and their larger cousins in Western Australia. Megalibgwilia ramsayi appears to have been prominent across mainland Australia and extended to Tasmania whereas M. robusta has been restricted, so far, according to fossil remains, to New South Wales. The two species possessed snouts that are more well suited to probing and grabbing insects than grasping and probing for worms like the Zaglossus group of echidnas. As contemporary species, Megalibgwilia and Zaglossus may have possessed overlapping ranges, making diverse diets for the two groups of animals important in minimizing competition for food sources.

Short on Papers

There are not many papers hosted online featuring Megalibgwilia. Considering that these echidna ancestors have been known and described for almost 150 years, the lack of modern articles is somewhat sad and almost depressing. There are plenty of articles that make passing mentions of Megalibgwilia or compare the "giant echidnas" to extant members of the genus. One of the original articles describing Megalibgwilia by Owen in 1883 originally named the animal Echidna ramsayi and consisted of less than a half page of text. That abstract of a lecture by Professor Owen can be viewed in the archives of the Proceedings of the Royal Society here. Unfortunately, Dun's 1896 description of the other species, Megalibgwilia robusta, has not been hosted anywhere online. Print copies may be nearly impossible to find as well given the age.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.