Glyptodon Facts

The facts about Glyptodon are posted in many different places online and in a variety of videos. As I stated yesterday, many people recognize Glyptodon right away even if they do not or cannot recall the name of this large armored mammal. Because none of the videos that are posted about the animal show unique facts or interpretations of those facts that are not presented on the fact websites I will save the use of any websites until later. That, however, leaves us with copious amounts of literature to read about this interesting and odd shaped animal. The sites ThoughtCo and Prehistoric Wildlife present facts and detail some of what we know about the animal including its relationship to near contemporary animals and its descendants. These insights are, of course, useful in determining life histories, ecologies, and general life facts about Glyptodon. The Enchanted Learning site presents similar, but less, information about Glyptodon. It does, however, offer us a coloring sheet, something I have not posted in many months for our Sunday posts. Enjoy reading and coloring today!

A Mammalian Tank

Good evening sports fans (I have been watching hockey today) and dinosaur fans. We are going to get back to dinosaurs soon, but this week we are going to look at a well armored mammal that I saw, remembered, and noticed I have never discussed on here at the Field Museum on Monday. A genus of the curious Xenarthran animals of South America, Glyptodons are armored animals with large curved teeth and an armadillo-like shell around its body. This should not be a surprise when I say that armadillos are close living relatives of the now extinct Glyptodons. Regardless of name recognition, the visual of a Glyptodon is typically quickly and readily identifiable; this may be the first time for some being able to place a name with the animal. Glyptodon tails are different across the genus, but we will see that their thoracoabdominal armor is fairly conservative across time and evolution.

A Load of Anatomy

Petrolacosaurus kansensis was discovered in a smoothed layer of shale in eastern Kansas. The discovery included a skull with two temporal fenestrae (part of the defining characteristics of diapsids), a large orbit and teeth. It also included over 60 caudal vertebrae, 7 cervical vertebrae, the pectoral girdle, radius, ulna, fibula, and articulated tibia and astragalus. This articulation tells us a lot about the morphology and development of the reptilian astragalus and ankle joint, which is why many papers have been written on this specific aspect of the fossil remains. Manual and pedal phalanges were also discovered, allowing researchers to know the arrangement of the digits; this is actually quite important evolutionarily as digit order and retention has changed over time (some animals have presented with certain digits lost and sometimes knowing which digits were retained or lost can inform evolutionary relationships). These characteristics have helped to inform the position on the reptilian and diapsid family tree that Petrolacosaurus currently maintains. Further finds of this animal and others will help to refine that positioning further of course, but at this moment we have a good idea of where the animal is phylogenetically and what its position means for the origins of specific regions and parts of the reptilian body plan, making this an extremely important animal.

Old Literature

From Reisz 1977

Some days, as we all know here, the reading list for older discoveries is very small indeed. This is of course thanks to the fact that not everything ever written has been scanned or re-typed and posted online. This is not just an ancient writings problem either; I have had difficulty getting articles from as recent as 1999 online without contacting authors directly. This is important because there are numerous articles on Petrolacosaurus and some of them are slightly older articles. Remember that the small reptile was discovered in Kansas in 1932 but was not described until 1945. There were no field notes associated with the find other than the general locality of Garnett, Kansas; approximately 50 miles south of Lawrence and the University of Kansas. Having worked on a specimen from the University of Kansas Vertebrate Paleontology collections I can attest to the mountain of field records and their sometimes cryptic nature (the specimen I looked at was given the location "locality #12" but no other information) but I have not seen any completely lost field notes in my experience. Regardless of the completeness of field notes, Petrolacosaurus has been described and assigned and somewhat fawned over for decades now as the oldest known diapsid showing transitional characters. Reisz's 1977 article re-describing this old reptile and first diapsid possesses a very iconic, though general appearing, line drawing of the skull of this reptile which could easily stand in for any and all early diapsids and might be confused by some to represent a modern lizard of some kind. Petrolacosaurus has been used to describe the evolution of not only reptiles as a whole, but also in describing the origin of one of the bones making up the ankle joint, the astragalus (known as the talus in humans). This Peabody paper from 1951 is not only interesting, but important in understanding the evolutionary origins of a bone that was important for reptiles, crocodiles, pterosaurs, and dinosaurs and birds. Petrolacosaurus is a very important animal in the history of evolution despite its small size and these papers make that quite evident. Enjoy reading them and discovering more about the origin of reptiles!

Walking with Monsters

There are many animals known only from the screen for many people. Petrolacosaurus is a prominent member of this group of animals as many only know it from its appearance in the Walking with Monsters series. Despite its dinosaur-like name, Petrolacosaurus was a small reptile and, as we can see from the first clip featuring it, at the mercy of many other animals like the enormous amphibians, arthropods, and insects it was contemporaneous with. The second clip shows that not all of these interactions went poorly for Petrolacosaurus though. The small predatory reptile was the beneficiary of tragic natural events like forest fires (as shown) and was capable of running down prey smaller than itself.

Know Your Early Diapsids

One of Dr. John Merck's online lectures for one of his geology classes summarizes some aspects of diapsida and specifically references the characters of Petrolacosaurus that have caused it to be assigned to the base of the diapsid family tree. Other sites have information on Petrolacosaurus as well. These include Prehistoric Wildlife which has a short paragraph describing what is known about the small reptile. A more extensive entry and probably the most comprehensive and easy to read entry outside of the Wikipedia article or a scholarly journal entry is that found on the Walking with Monsters version of the wiki sites.

Dawn of the Reptiles

We have discussed the dawn of the dinosaurs, multiple times depending on the taxa discussed in any given week, the dawn of mammals, birds, amphibians, and a number of other introductory taxa. Some of these have been composed of disarticulated nearly complete skeletons and some have included single limbs or even single bones. One of the most complete purported "first" taxa is one of the earliest diapsids, a small reptile with two holes in its lateral skull wall (from which we gather the meaning of the word diapsid). Discovered in 1932, the fossil of Petrolacosaurus kansanensis (Lane 1945) comes from the Pennsylvanian age of the Carboniferous (approximately 302 MA) and includes the skull, pectoral girdle, elements of the hind and fore limbs, and a large portion, if not the entirety, of the axial or vertebral skeleton.

The Artistic Crinoid

Murals and large scale paintings of ocean scenes often include Crinoids. Despite their lower population now, comparison to the Permian, these odd animals have always been prevalent members of the ocean.This level of involvement in the ecosystem makes the inclusion of such creatures in artwork almost essential, especially in panoramas of more ancient subject matter. Some good images that include Crinoids can be found at this link (some may be erased in the future, FYI). Crinoids have been the subject of professional as well as amateur art for a very long time. They have been main subjects as often as they have been background animals actually. Line drawings of Crinoids have populated the notes of scientists since before natural history was even considered a legitimate profession (scientific history is one of my favorite side hobbies and I promise that the history of natural history is very interesting). The best Crinoid-centric image I have found this evening is presented below. This image is older, as we can tell by its artist, Heinrich Harder, but is one of the best Crinoid centered images that can be found online. The image shows a variety of Crinoids, or as Harder called them "seelilien", swaying gently in a current and anchored into the sandy bottom of the ocean. The colors have faded over the years, but imagining the brilliance of the reds, yellows, and purples of the Crinoids one can really see the beauty of these strange animals from Harder's perspective.

©Heinrich Harder

Forgotten but Popular

Crinoids possess a fairly simple appearance from an external view. A large stalk or stem, a calyx, and a feathery appendage are used for stability and locomotion, feeding and reproducing, and directing food into the mouth respectively. We can think of Crinoids as upside down starfish with the stalk growing out of what would be the dorsal surface of the starfish and a sucker or root-like tendrils anchoring the animal when it does not want to float on the currents. Some of these root structures are comprised almost entirely of the cirri that originate in the stalk. Their tough fibrous nature allows certain Crinoids to use the cirri as small and mostly inefficient legs as well, moving the Crinoid slowly from area to area. It is this stalk that is so often discovered by amateur fossil hunters in roadcuts in places like Missouri and Kansas; in case you find the shear number of fossils hard to believe consider these links please: (Missouri state fossil and Crinoid Stonehenge Model). The calyx is also frequently found, complete with the feathery arms, but is still not as regularly discovered as the stalk by amateurs. The calyx has, like other echinoderms, mouth, reproductive organs, and anus in close proximity to one another; if this sounds confusing, consult this graphic to the right. The feathery arms of the animal are called Pinnules and are ciliated, or covered in small hair-like structures called cilia that are capable of moving gathered food items toward the oral cavity of the animal. Crinoids add even more amazingness to their life history in that they are pentaradial echinoderms. Echinoderms are unique in that they begin life as bilaterally symmetric ("mirrored") larvae and during their life cycle grow to be pentaradial, or having five main segments arranged at 72º intervals around the mouth. Consider the ontogenetic image below to better visualize this change.

Researching Crinoids

Crinoid papers are everywhere. Crinoids are everywhere. The Crinoids have been researched across time in the Lower Mississipian, and in geographic regions like the Antarctic, and the western Atlantic. Character traits of various Crinoids have been research, described, and cataloged, with specific interests apparently heavily invested in morphology (including microstructures of endoskeleton), ontogeny, physiology, and even locomotion. Topics like the Permian extinction event are given special attention as well, as it justifiably deserves considering that this event was extremely significant in the overall evolution of this class of animals. These papers are, of course, just a very select few of the the published works concerning Crinoids and do not even begin to scratch the surface, but there are far too many works to read in a single week at this point in the history of Crinoid research. Enjoy the readings presented here and, if so inclined, go beyond through your own literature searches.

Living Fossil

The term "living fossil" is thrown out as a saying far more often than it ought to be used; it should almost never be used to be honest, but we cannot stop everyone from using odd phrases like that. Regardless, a documentary called Living Fossils produced an entire episode on Crinoids that is pretty well done and informational. Enjoy this video today:

Fossils and Extant Crinoids

Videos of extant Crinoid groups are often given fantastic titles like "Amazing Free Swimming Feathers!" and descriptions like "mesmerizing video". These videos are not heavily inundated with facts and interesting trivial bits as we try to disseminate on Sundays, but there are plenty of dedicated websites to garner facts from. Fossil Facts, Fossil Era, and Kids Search are prime websites for reading short paragraphs loaded with all kinds of facts about these interesting animals. More official sites also present fact files and quite a few photographs of fossil specimens. These fossils come directly from Kansas, in the case of the Kansas Geological Survey and a variety of localities in teh case of the UCMP at Berkeley.

Overlooked Animals

One of the most populous and overlooked animals in the ocean since at least the Ordovician is the group of over 500 extant species in the genus Articulata. Also known as Crinoids, these strange animals belong to the class Crinoidea, live in areas from the shallows to at least 9,000 m deep, and have a historical range in three additional genera (all extinct) that spans the globe leaving fossils in a large range of geographic areas and geological time zones. The fossils of these passive filter feeding animals have been found attached to fossilized driftwood, the bottoms of ancient oceans, and in lengths in excess of 40 m. As single stalked echinoderms that were enormously successful, Crinoids underwent two explosive radiations early in their evolution in both the Ordovician, when they first definitively appear in the fossil record, and during the very early Triassic, after an extinction event near the end of the Permian initially bottle-necked the Crinoid record for a short period. This second radiation lacked morphological diversity previously seen in Crinoids, but did exhibit some of the longest individuals with Pentacrinites reaching lengths of approximately 40 m (130 ft).

Given that there are hundreds of species and somewhat fewer genera, the reason that Crinoids have been lumped together for this week is because the wealth of information for any one individual species is actually quite limited, online, and there are a number that are not even mentioned anywhere online aside from acknowledgement that they existed. Talking about the entire group together we can discuss a large number of morphologies all at once and compare them. Be prepared for a lot of talk about stalks and plant-like morphologies. These are very unique animals that are often mistaken for plants. Be amazed, or perhaps underwhelmed, by their looks!

Photo uploaded by Berengi; GNU Free Documentation License, Version 1.2

Today is Something Different

The diet of cave lions was much like the diet of modern lions in that these were large apex predators capable of subduing and preying upon equally large animals. Some of these lions have been found in the dens of bears, suggesting that they were capable of taking bears but that some may have perished in the act; conversely, these remains found in bear caves may have been successful and commandeered the cave for itself. Other known prey items included bison, reindeer (as seen previously), and even saiga antelope; a family of Eurasian antelope that possess rather well insulated nasal passages. Despite never being mentioned, the human imagination likes to imagine that all apex predators would like to get a good meal of human flesh and therefore there are indeed illustrations, like the one below, that shows a "caveman" returning with dinner to find a cave lion devouring his female partner. Be very careful in showing this image as it has no real basis in the evidence we have of cave lion diet or their interactions with humans.

The Mythology of Lions

Lions, cave or otherwise, have been revered as royal, strong, proud cats for a very long time in the human world and extending some of the myths, legends, and beliefs that are lion-centric to cave lions is not a far stretch of the imagination. One of the early standouts of human literature is the Nemean Lion which was said to prowl Nemea in Greece and is within the historical range of both cave lion and modern lion but only the temporal range of the modern lion. Cave lion remains may have influenced the story of a lion so large and fierce that only the great Heracles could stop it from terrorizing the Greek peninsula. Origin stories in the myths of ancient Greece credit the abnormally sized lion as having been the offspring of titans or having originated and then fallen from the moon. Accounting for abnormal size in such ways certainly suggests that the story's antagonist may have been based on sub-fossil evidence of a large lion. The additional story detail that the animal lived in a cave could suggest either creative story-telling or literally finding the remains of a cave dwelling lion (a common occurrence from which the common name of Pathera leo spelaea originates).

Prior to the Greek, Persian, and classical Chinese (to mention a few cultures) mythos of lions, Eurasian Cave Lions were depicted in early cave art. The American Cave Lion has been depicted on various media in native North American cultures in various forms. Many of these appear more cougar-like (the North American cougar or puma has been referred to as the American Lion by many different source) and may actually be confused with the other cat. Considering that these more recent works were likely created in the likeness of cougars, the depictions of the American Cave Lion may actually be lower in number than the internet would have anyone believe.

Panel of the Lions, Chauvet Cave

Geography of Lions

Extant lions are restricted to the African continent in the modern day. The extant populations of lions representing a number of recognized subspecies are dotted across the continent in areas that represent a very minor proportion of their historic range across Africa, Southern Europe, and Southwestern Asia. If we were to consider the cave lions as subspecies of the extant lions, as many have described their phylogeny, then the historic range of lions actually covered the majority of Europe, Asia, and portions of North America. We know the extent of their range because Eurasian Cave Lions have been recovered in various places and are well represented in cave art in a variety of locations across Europe and Asia. The North American subspecies (hereafter today I will refer to them as the American Lion) has been recovered in similar ways: as fossils, from glacial deposits, and a large population has been recovered from tar pits as well. The American Lion is known from a shorter temporal range than the Eurasian Cave Lion (340,000 - 11,000 years vs. 370,000 - 10,000 years respectively) and is considered endemic to North America. The American Lion, despite a smaller range and a shorter temporal span, was approximately 25% larger than extant Lions and 15% larger than Eurasian Cave Lions (which are in turn 10% larger than extant Lions) making it the largest of the lions, including the closest common ancestor between American and Eurasian lions, Panthera leo fossilis. This also means that the American Lion is, as many of these lions are, one of the largest known cats in the history of known felids. The size of the cat enabled it to take prey like the reindeer shown below, usually taken in the modern age by large bears or packs of wolves, for example.

©Heinrich Harder

Genetics and Lions

Ice Age animals have a long, in the somewhat short time that it has been available, history of genetic and isotope research. The reason for this is that the thawed cubs mentioned yesterday have generated not only a lot of sensation but have provided scientists with intact remains that preserved the majority of the soft tissues and organs of the animals. This of course has led to chemical, microbiological, and genetic work being carried out using the preserved tissues of the animals. Some of these studies include molecular phylogeny (Burger, et al. 2004), diet inquiries using isotopes (Bocherens, et al. 2011), and studies of genetic diversity (Ersmark, et al. 2015). Some might be asking "How does one study diversity from a single litter of cubs?" and this is not without its caveats and misgivings; however, it is important to note that we have not discussed all of the populations of known cave lion with some tissue preservation. Many American Cave Lions have been recovered from the tar pits of Rancho La Brea in Southern California and these could add to the genetic diversity of known populations. However, the destructive nature of tar pits has hampered DNA recovery but that is not to say that there have been no efforts to recover DNA. These efforts have been largely unsuccessful unfortunately. This leaves us hoping there are other soft tissue deposits to back up these studies on genetic diversity that have not been mentioned here this week. There are, in fact, soft tissue preserved specimens from across Eurasia and many known from Alaska and Northwest Canada that are mentioned in the paper linked above. These are not entire cubs as we saw yesterday, and are therefore less famous, but are nonetheless quite important in terms of genetic studies of cave lion populations and diversity.

Non-genetic, chemical, or microbiological study is also important in the history of cave lions. These have included phylogenetic studies based on skeletal tissue, specifically cranial and dental characters (Sotnikova and Nikolskiy, 2006), as well as a detailed timeline of the extinction processes that affected and eliminated the Eurasian and American (Stuart and Lister, 2011) Cave Lions from their respective habitats. Though we have been discussing the American Cave Lion in conjunction with its Eurasian relatives seamlessly, there is mitochondrial evidence (see the linked molecular phylogeny paper above by Burger, et. al.) that this population split early enough in their evolution that it has been argued that these represent merely a "lion-like cat" with a very popular misnomer. This phrase was first prominently used in 1969 by C. R. Harington as far as I can tell, but his paper suggests that the North American and Eurasian animals were likely conspecific (Harington, 1969).

Monday's Movies

One of the most important discoveries in the past few years was the retrieval of two frozen Eurasian Lions after glacial melt in Siberia. This discovery has led to discussions about cloning and the paleobiology of the animals. Cave Lions have also been recreated and animated in documentaries. These include a lot of different documentaries actually, but the one linked here (from Walking with Beasts) is shown stalking a mammoth, and is fairly compelling to watch.

Things to Know About Cave Lions

A lot of people love Cave Lions as well as extant lions. This has spurred a lot of websites to host information on Cave Lions and even a 20 minute video which was self-produced that discusses what one amateur fossil enthusiast knows about the large cats. This video is spoken over a few artistic recreations of a few populations of Cave Lions. There is also a shortened video from WizScience that goes over a shorter version of some of the same information. Fact pages that we visit often are also well-represented with Prehistoric Wildlife and ThoughtCo (formerly hosted on About).

Subspecies of Lions

The list of subspecies attributed to lions actually encompasses some of the fossil species of lion that we are going to discuss this week. Rather than discuss the three distinct groups of cave lion separately (Panthera leo spelaea, P. leo fossilis, and P. leo atrox), we will lump the three species together in the sense that we will discuss them as individual populations distributed globally and officially labeled as subspecies of the extant species of lion. "Cave lion", used as a generalized term, refers to European (P. leo fossilis), Eurasian (Panthera leo spelaea), and North American or American Lion (P. leo atrox) populations of large carnivorous felids of the Pleistocene. These animals were not excessively morphologically disparate from extant lions, but distinctions can be seen and observed between the extant and the extinct. These small distinctions add up to larger lions than the extant species, as seen below.

©Roman Uchytel