The Kimmeridgian Boat Jaw

Senckenberg Museum of Frankfurt

The Kimmeridgian, often associated with the Solnhofen limestones of the Late Jurassic, is the area most often associated with high quality slab fossils of thin and small boned dinosaurs from Germany. Multiple specimens of a certain pterosaur, Scaphognathus crassirostris, have been recovered from this deposit. The generic name refers to the blunt boat-like appearance of the mandible whereas the specific epithet refers to the wideness of rostrum. Scaphognathus was an early pterosaur and was overall of diminutive size (skull = 4.5 inch, wingspan = 3 feet) with long needle-like teeth well adapted for grabbing insects on the fly. The teeth were well preserved in the skull of the holotype and, with additional specimens of the cranium as well, we know that there are 16 teeth in the upper jaw that overbite the mandible and that they are all vertically oriented. Fish catching early pterosaurs possessed diagonally and horizontally oriented sets of teeth. The holotype is a well preserved and articulated specimen that has not, like so many pterosaur fossils, been flattened thoroughly.

August Goldfuss, 1831

Life Intervenes

It is unfortunate that the past two days have seen no new posts concerning Dakotaraptor. The dromaeosaur has not been forgotten or pushed aside but other events and goings on were slightly more relevant than revamping a pair of months old posts. That said, I should schedule in a time to write so I do not put off days of writing these posts, even if the animal from the calendar was recently an animal on the blog anyway. Friday is image day now with the new schedule, though, and with a popular dinosaur images are changing and being uploaded almost daily because artists appear to be enamored with the large dromaeosaur still. An artist we have not seen around here lately, possibly because I have simply not looked at his page for a while, is Tuomas Koivurinne. Mr. Koivurinne has always been a favorite (because of his style and interests in dinosaur and military themes) and in the early days of the blog was featured very regularly. His interpretation of Dakotaraptor is probably one of the most dark portrayals in content and composition that is available for viewing online. To be honest, the color scheme involves a lot of cool but light colors, the darkness of the image in relation to other Dakotaraptor images online is due to the minimal sky influence on the image. Many of the images available are on white backgrounds or feature a more open terrain. The closest composition of images are those that we have seen from Emily Willoughby, but I would argue that her Dakotaraptor, while appreciably fierce, appears to be much more huggable than this rather raptorial version. I think that the image dichotomy between the two illustrators and their work emphasizes the fact that this was both a feathered and fluffy looking dinosaur (an argument could be made for the huggability of Koivurinne's Dakotaraptor also) and a carnivorous and potentially highly active predator. Similar view points are seen in the way that people view eagles, hawks, and falcons today as animals that look somewhat soft because of their feathers but tend to also respect their capability to produce violence to procure food. Dakotaraptor may have appeared fluffy and cuddly but it was a vicious predator and Koivurinne's artwork here captures that aspect of the animal's life perfectly while remaining quite safe for work and, I would argue, for sensitive audiences.

©Tuomas Koivurinne

Tapping Out

Normally I would never do this, but the only two papers that exist on Dakotaraptor appeared in the last paper post. Therefore, here is a link to the last post!

Movies for Dakota

Somehow we have not managed to run out of videos for Dakotaraptor. The dromaeosaur was big in life and has been big as a fossil so far. Its impact is more prominent because it is a "raptor" of extraordinary size. This is shown in the video that we are sharing for Movie Monday. Despite its popularity it is not featured in any documentaries, yet. This may change in the near future, but not at this moment. We do have more quality narrations and news stories though, and that is quite useful.

Dinosaur George has, since the last time Dakotaraptor was here, has posted a video answering questions on the dinosaur. We have not shown Dinosaur George posts in a while, and that is entirely because I have not come across them lately, not for any other reason. He seems like a nice guy and he values education. I am okay with him.

This Time

Last time on fact day I posted most of the same websites that still exist. Posting them a second time would be redundant and there is no need to do that. Besides, there was really only one or two that was worth posting. There was a rather good dinosaur fact video on Dakotaraptor and there were a few that I skipped over. Instead of posting old material, here are a couple of the fact videos that are acceptable, but that were passed over last time for one reason or another:

Revisiting a Recent Raptor

In the somewhat recent past we discussed a large dromaeosaur of the middle north of the United States. That dromaeosaur is was recently discovered and described and is named Dakotaraptor steini. This is the last full week of April and Dakotaraptor is the calendar dinosaur for the month of April. To refresh the reader's memory, Dakotaraptor is one of the largest North American dromaeosaur discovered to date and was recovered from South Dakota's Hell Creek formation. This formation is Cretaceous in origin and Dakotaraptor is from an area of the formation that correlates to the youngest rocks and therefore the end of the Cretaceous. Throughout the publication and popularizing of the description of Dakotaraptor the paleoartist Emily Willoughby has portrayed the dinosaur time and again. This illustration is the only illustration of hers that was not featured the last time that Dakotaraptor was the dinosaur of the week. She posted this little sketch on Twitter and it is absolutely adorable.

©Emily Willoughby

Size and Andrewsarchus

How large is the purported largest terrestrial carnivore that ever lived? Andrewsarchus mongoliensis had the largest carnivore-like skull known for a terrestrial animal. At approximately 3 feet long, the skull is absolutely massive for a carnivorous animal, as we see them today. A modern adult tiger has a skull measuring 1.3 feet in length. A tiger is a large predator. Andrewsarchus was a nearly 3 times larger predator, if we assume the body estimate is allometric with the skull. Artistic interpretation of the size estimates of Andrewsarchus look something like this, which is quite impressive:

Popularity and the Pig-like Beast

Andrewsarchus may not have been related to pigs, but the fact that it resembled a pig and still does in most modern illustrations may be severely confusing to some. The depiction in the most popular place that Andrewsarchus has been shown was even slightly rotund. The Walking With Andrewsarchus is large, muscular, and intimidating. That is a trend that continues in other illustrations as well. The strangest thing about Andrewsarchus' popularity is that it has blossomed in less opular venues than television, books, toys, movies, video games, and other highly visible areas. Instead, it has something of a nearly cult-like following on the internet. Amateur illustrations, professional illustrations, and fan sites are all populated with Andrewsarchus. Thankfully Andrewsarchus managed to be illustrated on one of the informational cards that we see now and again that is so vibrant and fearsome.

Superb Skull of A Gigantic Beast

The remain of Andrewsarchus consist of a single Mongolian skull from a presumed adult specimen. The skull is not a complete cranium and is lacking the mandible. This means that we do not know anything from solid evidence about the dentition of the lower jaw. The assumptions that are considered when looking at possible stand ins for the lower jaw include similarly built carnivores and members of Andrewsarchus' branches of the mammalian family tree. Simply put, this means that we have to consider whales, hippos, and small extinct mammals of the family Raoellidae. An assumption exists, regardless of the model taxon used to inform the mandible, that the teeth belonged to a strict carnivore. Contention in the field crew existed over this idea with Roy Chapman Andrews asserting that the 3 foot long skull belonged to a great predator and the chief paleontologist (Walter Granger) attributing the skull to a giant pig, essentially calling it an omnivorous beast of great size. No one disagreed on the great size, whatever their view of the diet. The known dentition is respectable and fearsome in the 3 foot skull. The dental formula is 3 incisors, 1 canine, 4 premolars, and 3 molars. This is the exact dental formula of extant pigs. That explains Granger's suspicions of the phylogenetic position of Andrewsarchus. Hippos have the same formula, with some variation, which backs up Chapman's assertions. Recent evidence has also reinforced Chapman's position rather than Granger's, but we cannot argue that he had a valid reason for being suspicious of the origin of the beast we know as Andrewsarchus.

Relationship Problems

The closest living relatives to our giant predator is a giant herbivore. This has happened many times in the history of life and as such it is not remarkable in terms of being a revelation. However, Andrewsarchus is actually considered the sister taxon to whales and small mammals known as Raoellidae (Geisler and Theodor 2009). Spaudling, O'Leary, and Gatesy (2009) were slightly less confident with the single skull but upheld the close relationship with whales and hippos. Instead of asserting a solid relationship at a single node, Andrewsarchus is placed in a polytomy with a small group of other fossil taxa. Ignoring phylogenetics and discussions of sister groups, the initial description by Osborn is online. I always urge people to read initial descriptions and that initial description is hosted right here.

Movie Mayhem

Andrewsarchus is a small but significant documentary star. Featuring in no feature length movies, the animal does play a significant part in a television documentary. As with many of the animals we have videos where they feature, this is another instance of the Walking With series showing an animal that we are interested in. The series covered, after their very well received initial dinosaur series, the time before and the time after the dinosaurs. The Eocene predator Andrewsarchus was contemporary with the large Brontotherium, but actually has only been found in Mongolia. The Walking With series places these Mongolian predators in the same habitat as the North American Brontotherium. Obviously this is not currently backed up by any evidence, but the potential could exist given the correct conditions and there may have been other brontothere like herbivores living in Mongolia.
Walking with Beasts - Brontotherium vs Andrewsarchus (Audio Remake) from Israel Barber on Vimeo.

Sites to Avoid

Andrewsarchus makes an appearance on a number of websites. Some of those are not exactly the kinds of sites that we want to get facts from. Therefore, ignoring the message boards with dinosaurs hypothetically fighting one another, the best fact pages are the only ones left (this makes sense to everyone I imagine). There are encyclopedia entries like that at Kids Search that is very short and not very thorough but also very thorough sites like About. About's site is now, or at least for this single animal, divided into individual pages for each part of the entry. There is an entry on Dinosaur Jungle that is also well written. It does feature a very wolf-like Andrewsarchus at the top of its page, which is very incorrect, but an understandable mistake. Prehistoric Wildlife is more of a fact file than an encyclopedia article. Instead of the normal Prehistoric Wildlife images at the top of the page, only the skull is featured in the size comparison. This skull is illustrated and looks really nice, it is an interesting size comparison image.

Roy Chapman Andrews' Champion

When Henry Fairfield Osborn named Andrewsarchus mongoliensis in honor of Roy Chapman Andrews, he did not realize how long it would take for the general public to recognize and love the truly strange fossil mammal. Andrewsarchus was an artiodactyl (related to giraffes, bison, and similar animals) which makes it even more intriguing when one finds out that Andrewsarchus was a voracious predator. This assertion is based on the single known skull which sports a snout totaling about 60% of the entire skull. That snout is loaded with sharp mammalian teeth. Osborn compared that snout and skull to a number of other carnivores in his initial description. Osborn also declared that the skull of Andrewsarchus belonged to the largest terrestrial mammalian carnivore ever. It may have been.

Not so Popular

Amazonsaurus is popular for being a rare find in northern Brazil and it is also popular for containing enough material that it could be diagnosed to a genus. Amazonsaurus, for these reasons, is not very popular at all. Being represented by such a minuscule amount of material, Amazonsaurus is largely ignored by the general public because it is largely ignored by the scientific community as well. Not much can be said for a large sauropod that looks and acts like a sauropod because we cannot hypothesize much more on the anatomy with the overall lack of anatomy. People do like to draw the dinosaur though. Some of the anatomy is based on Diplodocus of course, so they are really drawing a different dinosaur mostly, but the level of detail here is still fairly phenomenal.

What Do You Look Like

The problematic part of fragmentary fossil remains cannot be narrowed down to a single area of study. One thing that certainly suffers is our capability to interpret what an animal looked like as an entire organism. This has further implications in that body shape and size can tell us a lot about how an animal lived, how it may have eaten, how much it ate, and many, many more things. The knowledge of functional morphology of an animal outweighs simply having quality accurate illustration as it tells us what the dinosaur actually did, and looked like as well, with the anatomy that it had to work with. Fragmentary fossil skeletons therefore rely heavily on identification to a group from what is available and then that another animal in that group has had enough fossil remnants collected to inform us to make an educated decision about what the new and fragmentary dinosaur may have looked like. Amazonsaurus contained enough fossil skeletal elements that its affiliations as a sauropod and more specifically as a diplodocid have been accepted after description. We have been able to fill out the missing anatomy with informed hypotheses based on Diplodocus and other members of the group. One thing that has been estimated based on our knowledge of the fossils and its cousins is the size of Amazonsaurus. Extrapolating from the vertebrae and pelvis by comparing the number of elements and the sizes of elements with other dinosaurs we have estimated the length and height of Amazonsaurus. The sauropod was not a titanosaur but it was a notable sauropod, achieving a size slightly larger than an elephant and appreciably longer. Many illustrations of Amazonsaurus out on the internet show the tail coiled up or gently whipping around. This is a tie back to the relationship with Diplodocus, and may or may not have actually been indicative of the manner in which Amazonsaurus held its tail. To appreciate the overall length, at any rate, the tail has to be straightened out.

Honorable Mentions

Amazonsaurus makes appearances in many studies and summarizing papers where it is discussed in relation to whatever other sauropod or animal that they were compared to. The only paper that is really worth reading today is the description of the fossils that were recovered and given the name Amazonsaurus. The description paper  includes line drawings and pictures of the fossils, images of the locale, and maps of the region where the fossil was discovered. Description of the geological setting is included as well, which is important for determining the setting in which the dinosaur lived, in addition to other particulars about the dinosaur and its fossil environment.

Brazilian Dinosaurs

Amazonsaurus has a 45 minute documentary that tells all about the dinosaur from discovery to description and beyond. The only problem with it is that the entire documentary is in, I am fairly confident but would be willing to admit that I was wrong, Brazilian Portuguese. The first half of the documentary is shown below. The second half is linked from the first on YouTube and after the first half ends.

Non-Portuguese speakers have a more limited choice of documentaries that they can both watch and fully understand. These are shorter and less informational. They include entries like the one below. Though not an actual documentary, it affords some information that can be used, if one can escape the robot voice without turning it off.

The Amazing Amazonsaurus

Amazonsaurus is not a very complete dinosaur. It is, though, well known as a very rare dinosaur from northern Brazil. That gathers a considerable following somewhere on the account of the scarcity of the fossils if nothing else. This has led to an appreciable amount of information available online. These sites range from short fact pages consisting of only a few lines of text to a short but well constructed series of paragraphs detailing the life history and diet of Amazonsaurus. As always, there are middle of the road pages that are easily accessible to readers of the high elementary to middle school level; groups that are at the heart of dinosaur fandom.

Adding More to the Long History

©Luiz Fernando

This week we are literally adding a longer entry into the annals of Dinosaur of the Week. There are a lot of sauropod remains in the fossil record and we have discussed many of those remains (honestly, we have gotten to the point that some of the dinosaurs we discuss have very little material actually being discovered. Amazonsaurus maranhensis is one of the few sauropods remaining that we have not discussed that has an appreciable amount of fossil material attributed to it. The vertebral column of the back and tail are fragmentary but more intact than the pelvis. The number of elements is small, but attributable to a sauropod and the only dinosaur material discovered in the state of Maranhão in northern Brazil identifiable to a genus or species.  Two unidentifiable theropods, an unidentifiable sauropod, and Amazonsaurus are known from the Itapecuru formation in Maranhão. Not much is known about the dinosaur, but it has been assigned to a group of diplodocid sauropods from the Cretaceous known as Rebbachisaurid.

Heads and Tails

To start discussing the body in more skeletal detail, the tails of Dilophosaurus are well known. The holotype animal is actually quite nearly complete. This is somewhat rare for large fossil animals, though Dilophosaurus is still somewhat small by dinosaur standards. This is what allows for the inferred skeletal elements of Sinosaurus however and we do benefit from the completeness of one dinosaur in comparison with a second dinosaur. Sinosaurus, though, has a well preserved skull in a few specimens and a juvenile specimen is included in that number. The juvenile skull, and a number of the adult skulls, are disarticulated. Disarticulation can be a very beneficial outcome of fossilization; a well articulated fossil skull is good for showing a complete entity whereas the disarticulated skull can be used to show how bones of the skull are sutured and put together into the solid structure.

Sinosaurus cranial elements are well known because of all of these specimens. This allows us to identify individual bony elements and differentiate them from other animals (aiding in justification of separating the genera/species). The teeth of Sinosaurus are also helpful in this matter. These teeth are serrated on both the anterior and posterior edges and flattened width-wise. This means that Sinosaurus' teeth are actually somewhat shark-like in their construction and would cut flesh on biting down and pulling back and away with the teeth. Those inferred actions are more closely related to animals like the dromaeosaurs with recurved posterior serrated teeth. Sinosaurus had recurved teeth as well, making the comparison worthwhile, but the anterior serrations are much more useful for cutting into flesh during the powered closing of the jaw. The anatomy appears to indicate the idea that Sinosaurus was biting and cutting its prey at the same time and then pulling and making a second cut as its teeth were moved away from the prey. That sort of wound would be hard for any animal to recover from and might explain some hunting hypotheses related to these animals.

Sinosaurus Shown Complete

One of the positives of being similar to another fossil animal is that that fossil animal's skeleton can inform missing and destroyed elements of the animal that it is comparable to. Sinosaurus therefore benefits from relatively more complete Dilophosaurus skeletons and vice versa with a little bit of guesswork involved where required. Many times the fossils we collect from any given species or genus are related to the cranium and there is very good reason for this. A key element in the process of fossilization is the fact that larger, more solid objects have a regular tendency to fossilize better (for many many reasons that are better left for a different discussion). The cranium tends to be one of the larger, more solid, objects that many animals possess; clams and other hard shelled fossil animals as well as fossilized plants benefit from related but different circumstances. This all has a lot to do with what we know about Sinosaurus. This dinosaur exists mainly as a number of well preserved skulls with some fragmentary skulls and postcranial skeletons added into the mix for good measure. These are not the kinds of "wow-factor" remains that typically interest the public to the point that we see children's books and stuffed animals. The fact that Sinosaurus has a morphological doppelganger that is much more well known from Jurassic Park does not help to spread the word about the dinosaur; the general public tends to equate anything remotely like one dinosaur as that dinosaur unless expressly corrected, there is no shame in not knowing your dinosaurs!

Casually Walking

Early theropods did not need to be as enormous as Tyrannosaurus for a number of reasons, chief among them being that their prey was not nearly as large as the mega-sauropods and ceratopsians of later ages of dinosaurs. Sinosaurus was still a long predator but possessed a much more gracile body than many following theropods. The dinosaur was definitely still well muscled and had the teeth to terrorize contemporary prey items; however, it is unlikely that it was generating the bite forces of Allosaurus or Tyrannosaurus. Sinosaurus may have rivaled and even outraced the other two dinosaurs, based on the gracile body, but tests of this sort of hypothesis has not been conducted on Sinosaurus so we cannot do more than speculate. The body of Sinosaurus is estimated to have been approximately 5.6 m (18 ft) long, making it shorter than the similar-in-appearance Dilophosaurus which measures 6 m (20 ft) long. Dilophosaurus, which appears in the fossil record a few million years prior to Sinosaurus was probably the largest carnivore in its ecosystem, if not globally, at the time and Sinosaurus may have held a similar distinction. Aside from being the largest animal, a large portion of the length of Sinosaurus (as in Dilophosaurus) was made up of tail.

©Dmitry Bogdanov (as Dilophosaurus sinensis, jr. synonym)

As we know from dromaeosaurs and hadrosaurs a long stiff tail is a great counterbalance for running. However, the tails of Sinosaurus specimens does not appear to be stiffened and instead appears to be appreciably flexible instead. All of the largeness and gracility to this point has pointed to a terrific carnivore outpacing and overshadowing all of its prey items. A flexible tail, though, points less toward high speed running, so it is possible that despite appearing capable of producing significant speed (in relation to other dinosaurs) Sinosaurus may not have needed speed or it may not have required a stiff tail for specific counterbalancing; that is, it may not have accelerated or sustained speeds in the same way that later stiff-tailed dinosaurs did. There also exists the possibility that there was not a great amount of speed at the command of Sinosaurus and its gracile frame and appearance of potential speed is, like its similarity in appearance with Dilophosaurus, merely an impression of a character that we have attributed to it hypothetically, but falsely.

Teeth, Tracks, and Crests

Sinosaurus has left its mark across much of China and a great deal of paleontology that has been published from China. The literal mark making is documented in trackways, though these are rare (compared to those in North America) and are not completely diagnosable. To that end, a small number of theropods are discussed whenever trackways are found. Sinosaurus has found its way into those discussions as a stand in (literally) foot model for some theropods and as a contributor to these trackways. Xing et al. 2014 discusses both of these possibilities in regard to newly discovered trackways in central China. Trace fossils of predators are typically represented either by the trackways above or by lost teeth. The benefit, to us and theropods, of lifetime tooth replacement is that we can find fossilized teeth and theropods never have to go hungry. Whenever teeth fall out, the bone that holds those teeth remodels as new teeth grow in. This loss and remodeling is the subject of a description of the process using a specimen from the Lufang Basin in Xing et al. 2013. Traumatic tooth loss and feeding are discussed in terms of the remodeling of alveolar areas of the mandible and maxillae. In terms of the crests part of the title, many descriptions of the crests of Sinosaurus have been published. The crests are discussed in a cooperative article from American, Chinese, and Canadian paleontologists that looks at the mechanical capabilities of these crests. This may sound a little odd, however, finite element analysis (FEA) to test the crest's capability to resist loads during intraspecific combat. This use of crests has been hypothesized many times, but FEA has not been used often to test the capabilities to resist mechanical loading and to test combat hypotheses.

Weird Video List

The videos associated with Sinosaurus are as few in number as the fact pages. There are a number of good papers, but that will come tomorrow. Today there are only a handful of videos that are worth sharing. Partially because Sinosaurus is a mostly forgotten dinosaur, these videos are showing skeletal displays or self-made models rather than anything that was made for movies or anything else of that nature. In the movie department, though, we have the fact file videos of WizScience, which are typically well done but narrated by the very robotic Microsoft Word voice. All of the other videos that we find online are actually people somehow missing the letter p when spelling Spinosaurus. It appears to be a bit of an epidemic actually.

Confusion and Facts

Sinosaurus has confused many people over the years. The fossil is not entirely to blame; evolving phylogenetics have pushed apart Sinosaurus and its morphologically similar cousin Dilophosaurus. However, the visual similarity of the two has caused many to equate the two or infer a close relationship where none exists. Many pages have gotten this straightened out over time and correctly identify the familial relationships of Sinosaurus (which is more closely related to Cryolophosaurus than it is to Dilophosaurus) as they point out relevant facts about the dinosaur. The fact pages concerning Sinosaurus are few in number and that makes for a short post, sadly.

More Chinese Lizards

Any dinosaur with Sino- in the genus or species has a history of some sort that is related to or originated in China. That, of course, is important given that this week's dinosaur is very prominently related to China by name and location of recovered fossil remains. Sinosaurus triassicus Young 1948 is a dilophosaurid theropod with a number of specimens representing it. We know there are multiple not because they are all published, but because at least a secondary set of remains was named as Dilophosaurus sinensis Hu 1993 and synonymized in a subsequent study of the remains conducted by Dong Zhiming in 2003. The many different remains are housed in numerous museums including the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and Lufeng Dinosaurian Museum (ZLJT). The reason that realizing that there area respectable number of Sinosaurus fossils in museums is important is because this is a dinosaur that is not popularly well known but is well known in science in part due to the number of specimens. 

As stated earlier Sinosaurus is a dilophosaurid. Dilophosaurid is not a recognized clade, but describes a group of crested theropods that superficially resembles the dinosaur Dilophosaurus wetherelli. Prior classifications place Dilophosaurus closer to the Tetanuran theropods (stiff-tailed theropods) to which Sinosaurus belongs. Dilophosaurus actually sits outside of even the Tetanurans in the same group as Coelophysis, making it a basal theropod. Therefore, despite superficial resemblances, Sinosaurus is actually a more advanced and derived theropod. The specific name, triassicus, refers to the fact that Chung Chien Young originally thought the formation from which the type specimen came was Triassic. We now know that Sinosaurus, like Dilophosaurus, was actually an early Jurassic dinosaur dating to between 200 - 190 million years ago.

Differences in Dinosaur Heads

©John Sibbick

Hadrosaurs of all shapes and sizes have unique features, as we know for any given taxon, and many of them sport some sort of crest above their heads. Strangely, considering the prevalence of crests, there are very few illustrations dedicated to displaying the differences between the crests and the hadrosaurs that sport them. The most well known of those hadrosaurs include the most well known crests (e.g. Corythosaurus, Parasaurolophus) in the ornithischian world. Descriptions of the Lambeosaurus crest should be fresh in everyone's mind from yesterday and the Lambeosaurs in the above illustration should therefore stick out fairly well. However, if the description alone was not enough to help a casual observer pick between Lambeosaurus and Corythosaurus please turn your attentions to this second image that shows both dinosaurs and labels them clearly.