Trinacromerum Swims Again!

Honestly, it does not really swim again at all. There are no mentions in popular documentaries. There are a few Dolichorhynchops mentions in a few varied documentaries. The main place it does show up where we can watch a model of Trinacromerum in motion is actually in the Facebook game Jurassic Park Builder. Unfortunately it is not too factual and not at all like we usually share here on movie Mondays. At least there is something though! The model is pretty accurate in terms of body shape and proportions of appendages to the body. The fact that it never has to surface to breathe may confuse some that are just learning about plesiosaurs. Also, it appears to use its tail to swim more than its flippers, which is totally incorrect and, unfortunately, therefore very misleading.

Trinacromerum, The Lesser Known

Trinacromerum is a less well known, studied, and found plesiosaur than its close relation Dolichorhynchops. There are all the pages slowly accumulating here, the descriptions and fossils at Oceans of Kansas, and the page at About. Coloring pages and other related children's fun pages under the name Trinacromerum do not exist; however, sharing the below image of Dolichorhynchops works for the purpose of a coloring page for today.

Saturday Image

In terms of the Plesiosauria, Trinacromerum is in the Polycotylidae family of short necked plesiosaurs. Its stout little body, in terms of enormous marine reptiles, was designed for quicker movements through the water. Whereas icthyosaurs were streamlined and built for speed, most plesiosaurs appear to have been quite slower and not as often built for anything nearing speed. That said, Trinacromerum was one of the more streamlined and faster of the short necked plesiosaurs. The sagittal crest on the skull allows for more muscle attachment and, most likely, these muscles then attached to the lower haw. This means that the snapping shut of the lower haw was rather quick and violent. A quick, strong jaw closure combined with a faster swimming body plan means that Trinacromerum was capable of chasing down faster moving prey than its slower swimming relatives. Imagine that suddenly chasing you through the ocean!

In Honor

©Nobu Tamura

Special for this week, I would like to discuss an animal that is not a dinosaur this week. Coinciding with the defense of my Master's Thesis this afternoon at 3:30 Central time, this week's animal is none other than Trinacromerum! Trinacromerum consists of two species, one being not much heralded, T. bentonianum and T. kirki. Trinacromerum is a polycotylid plesiosaur closely related to Dolichorhynchops and often confused with that genus. Its short neck and probably high speed body was built for cruising through Cretaceous waters and nabbing fish on the fly. Trinacromerum is a rather interesting marine reptile and ought to be fun to talk about for the remainder of this week. Be prepared for this unexpected sidetrip to the ocean!

Popularity Is Everything

Aardonyx is a relatively newly discovered, described, and documented dinosaur. Its popularity is mostly seen in news stories related to its discovery and naming instead of in the typical popular outlets of toys and children's books for example. Huffington Post wrote about it as did National Geographic. At least one Spore model has been made by a modder/Spore enthusiast out there, which is rather wonderful.

That Foot

As stated in the paper, if one had time or reason to read it yesterday, the weight bearing axis of the hindfeet and hindlimb of Aardonyx exhibits a shift to the medial aspect of the foot. Additionally, the femur of Aardonyx exhibited a more straightened shaft than in previous bipedal members of sauropodmorpha. Femoral shape, weight bearing axis, and a slower gait are all indicative of quadrupedalism, and Aardonyx was in the transitional placement in the three categories, making it slightly faster than later relatives with a convex femoral shaft and bearing the weight less in the medial aspect of the feet. Also, the humerus was notably shorter than the femur rather than of equal length; another important trait in quadrupedal dinosaurs is the near-equal length of femur and humerus.

Sister of Quadrupeds

In the describing paper, published in Proceedings of the Royal Society B, Aardonyx is discussed as the sister taxon to obligatory quadrupedal sauropodomorphs. This rather straightforward and almost emotionless statement is one of the most important phrases in the entire paper. Another highly important discovery, to those that love sauropods, is also mentioned in the abstract in a bit more detail; the anatomical orientation of the bones of the foot and their weight bearing capabilities are hinted at briefly. This comment and discussion of the anatomy of the foot leads into a rather interesting discussion on the evolution of bulk browsing in sauropods. This in turn leads to more discussion on obligate quadrupedalism from this facultative quadruped. This image is from the paper and details the remains discovered that were used to describe the new taxon.

From Yates, et al.2009

Dr. Bonnan Tells A Story

Aardonyx has not appeared in many videos. There are a few out there that are tribute videos more than anything else. However, the best video out there for discussing the what, where, and how of Aardonyx's discovery and description is an interview of Dr. Matthew Bonnan discussing where it was found, what it meant to find it, and why it is a very important transitional fossil animal.

Drawing and Learning

Two resources for the interested student today. The first is the London NHM's Dino Directory, which is almost always a good site, but today lacks an image. It does have a good short amount of information and, despite saying no images exist, also has an image depicting the size relationship between the average human and Aardonyx. The second resource is more for the artsy or open to try to be artsy dinosaur lover. This video shows how to draw Aardonyx; leaving a nice image for coloring afterwards as well even if it is not the best version of Aardonyx out there. How to draw videos are kind of hit and miss of course, but it is not a bad thing to open oneself up to trying new things, like drawing dinosaurs! There is also a step by step guide, if that is more one's speed.

Nearing 4 Footedness

©Matthew Bonnan

The skeleton of Aardonyx is incomplete; however, there are a number of very similar recreations of the animal based on what limited skeletal material has been recovered. Regardless of the amount of material, the recreations are always presented with large nares and domed snouts. The long neck and tail are known as are the claws that give the name to the animal. In their placement and orientation those claws are more like the extended hand claws of Baryonyx rather than those of Iguanodon. The stance of the dinosaur is always bipedal but with the center of gravity very clearly near the center of the thoracic area. The stance is very close to quadrupedal walking and definitely shows a good transitional sort of gait as the weight forces the bipedal to quadrupedal stance. The rather long tail counterbalances that upfront center of gravity.

Transitional Sauropods

©Nobu Tamura

From savage little dinosaurs to gentle giants, we like to take odd leaps through time, geography, and ancestries. Earth claw of Celeste, or Aardonyx celestae as it is more commonly known, was a transitional prosauropod in the adaptation of quadrupedalism (for weight support) from bipedalism. The structure of the foot of this animal revealed a lot about how the sauropod gait and stance evolved and cemented the quadrupedal to bipedal evolutionary line in sauropod movement. A very odd nose and a rather large claw accentuate this dinosaur in addition to the interesting foot structure; things we will learn about in the coming week. Looking at this animal now we can see that it looks rather plain and somewhat uninteresting, but I promise that it will reveal itself shortly as anything but that.

The Atrocity of Anonymity

©Gabriel Lio

Atrociraptor is a dinosaur that, should we discover more remains, will become more and more exciting and well known as time goes on. The few remains available now, however, are pretty interesting and that may, in time, also build support and love for the animal. Until then, we will have to be happy with the Spore video shared, the book we talked about, and the few internet resources that were shared.

Finding Something in Not Much

©Michael B H

The fossil remains of the type specimen of Atrociraptor has very little material. The material that is present is a mandible and the anterior half of snout of the dinosaur. What skull there is depicts an animal that is short lengthwise and tall in height in its head. Large serrations of the teeth and their emergence at an angle to the jawline means that Atrociraptor had a rather vicious bite that could certainly inflict mortal damage. The short snout and tall skull were most likely strongly muscled as well. The skull, then, was a rather efficient and violent weapon. It was the kind of damage that earned a name and fed a small but voracious predator during the Late Cretaceous.

Announced In A Book

I promised good papers today because I had no movies for a Monday. Atrociraptor was first announced and described in the book "Feathered Dragons" edited by Currie, Koppelhus, Shugar and Wright. It is rather different for an initial description to appear in a book as wide in scope and reach as this, but it was quite appropriate considering the context of the book in general. The minimal fossil remains are detailed, described, and shown in multiple views and arrays. Atrociraptor also shows its angry face in the Mesozoic field guide often referenced the past few weeks as well. Since the naming portion of the book is available online it is, of course, encouraged by me to read this book section and enjoy what little fossil evidence there is to enjoy for this dinosaur.

Monday Blues

No movie Monday for Atrociraptor. Not unless you count Spore that is.

This is clearly not the best model of Atrociraptor. At least someone has put some effort into putting out some model of this little known, little fossilized, killing machine. There is literally no other video out there online that mentions Atrociraptor, to my knowledge, and my exhaustive search must end at some time. Unfortunately this time around, it ends with this less than ideal result. However, I have papers for tomorrow. I do indeed!

Kids and the 'Raptor

Small fossil materials almost always lead to small returns in most forms of popular culture, including the resources available for children. Academic Kids is the only website that attempts to toss out information at a lower reading level aside from About, which always has a rather succinct and lower level reading text. Atrociraptor lacks dedicated coloring pages and interesting kids videos, it is too bad though, considering that it could definitely make a really awesome addition to all kinds of kids shows or even the little shorts associated with the "I'm A Dinosaur" videos by Hooplakidz.

Softer Sides of Savagery

©Ezequiel Vera

Atrociraptor means "Savage Thief" and is really a fairly fantastic name. The majority of images that people have come up with for this supposedly savage dinosaur are very violent, perhaps appropriately so considering we are talking about a carnivore initially linked to the very active predators of the Velociraptorinae. The Saurornitholestinae subfamily is not a trio (Atrociraptor, Bambiraptor, and Saurornitholestes) of gentle herbivores, but it is not as often associated with the violent carnage that the name Velociraptor tends to evoke. The other side of the coin is a carnivore that hunts to survive and does so without the savagery iconic to other images of dromaeosaurs; all hunting and killing by carnivores has some level of carnage and savagery in it. This brings me to the point of mentioning the facial features of this interpretation of Atrociraptor. Atrociraptor tends to be very similar in most illustrations. The typical body features of a dromaeosaur are seen here; large pes claw, open wrists, feathered body, and stiffened tail to mention a few. The face is the only material known and is scaled on the muzzle and feathered posterior to that, as would be expected in a contemporary illustration. The eyes are large and capable of facing forward. The thing that is the most striking in this image is the upward turn of the jawline. It is almost as if it is smiling as it runs some morsel down. Take a moment and think about that.

Atrocious Atrocity

Photo by Emily Willoughby at the Royal Tyrell Museum

In 1995 Wayne Marshall of East Coulee, Alberta discovered what was to become the type and only specimen of a dromaeosaurid known, 9 years later thanks to Philip J. Currie and David J. Varricchio, today as Atrociraptor marshalli. The Horseshoe Canyon Formation where the fossil was discovered is the home of many Albertosaurus fossils as well. Originally assigned to the Velociraptorinae in the Dromaeosauridae; however, in 2009 Currie assigned Atrociraptor to the Saurornitholestinae. Despite the minimal nature of the fossil remains, the snout and a small amount of skull make up the type specimen, the fenestrations that are in the snout are unique enough that the specimen is known to be different enough from other members of the Saurornitholestinae to constitute remaining classified as a unique species and not synonymized with any other taxa.

The Popular Crowd

Jinfengopteryx is neither well known or uniquely popular. Even the supposed Chinese mythology surrounding it, Jinfeng is a derivative of the name of the "Golden Phoenix" that is queen of all birds, turns out zero online hits. There could be any number of reasons for this, but for a namesake to turn out absolutely zero hits is pretty novel. Books, other than the field guide mentioned earlier in the week, and movies leave Jinfengopteryx out in the cold. No toys exist and very few pages online hint at its existence. The birdlike qualities of Jinfengopteryx have been debated and the dinosaurlike qualities have been counter-debated (though we can fairly confidently say that we can agree this is a very birdlike dinosaur). Regardless, this is an interesting fossil animal and we can probably all agree that it is somewhere, family-wise, in limbo; however, it deserves more recognition than it has currently garnered and hopefully, in the future, we can revisit it and see that is much more widely known and studied. We can also hope for another specimen to be found, but hoping can be pretty bleak sometimes in paleontology, so don't be upset if it takes a while to find a second specimen!

All the Single Birds

It may not have been mentioned, but Jinfengopteryx is known from a single specimen. That single specimen, like many well preserved "dino-birds," is preserved in a slab of fine sediments that preserved the little specimen wonderfully. The tail and preserved feathers along the tail are fantastic looking in the fossil slab. The counterslab, which appears to be missing, probably has some nice carbon film impressions; however, I do not know if it is just missing or non-existent. The known feathers are numerous and well studied, as we have mentioned before. The teeth and other troodontid features can be seen in this fossil as well; this includes the general morphology of the skeleton but also makes it one of the only troodontids known to have feathers. Also, it is in what I can really only describe as a "roadrunner pose" on that wonderful fossil slab.

From Ji et al. 2005

Once More Compared

I can easily have a simple day and simply tell everyone to read the paper shared recently on size and evolution preceding the adaptations to powered flight; however, I have other papers for today as well. There are a couple of really good papers (I am leaving out the papers that named Jinfengopteryx) that I definitely recommend to learn more about our "dino-bird" of the week. One paper, that is available to all as an abstract, but can be found with a little effort, inter-library loan, or good friends, compares Jinfengopteryx and Archaeopteryx (as well as other long-tailed near Aves). The comparison is fantastic and the topic overall is very intriguing. The skeletons as well as the feather impressions are compared and the placement and flight abilities of the different "dino-birds" are discussed thoroughly. The second paper, available as a PDF file here, discusses the ecological factors that caused specialized evolution to occur in theropod dinosaurs. Specifically, the ecological factors promoting herbivory (herbivor-ism? vegetarianism?) to become dominant features of the diets of some theropods including the "dino-bird" Jinfengopteryx are the main discussion points of this paper. It makes for some fun reading, I promise!

Feathers Evolve In Motion

As mentioned yesterday, there are not many (read: any) videos that really mention or feature Jinfengopteryx as a main character. There is the documentary on feather evolution that discusses many fossil birds, dinosaurs, and "dino-birds." The video is not Jinfengopteryx heavy; however, it is below and does mention the animal at times, so it qualifies as part of video Monday for as much as it can count.

What to Post When There is Nothing to Post

Our little golden phoenix has been left out of the children's literature. There are brief summaries of what we know about Jinfengopteryx out there to be read but that does not necessarily make up for the lacking pages and resources. Videos we have seen before discussing feather evolution discuss Jinfengopteryx, but we do not even have a good hearty Dinosaur Train or Dinosaur King reference like we usually see with our little "dino-birds"; it is a little frustrating to have minimal material in any one specific category. However, Jinfengopteryx is a good critical thinking point if it is not a good source of coloring pages and so my unofficial assignment to little dinosaur loving folk out there today is to look at this print by John Conway and make your own list of reasons why these little "dino-birds" should be dinosaurs, birds, or both.

Roostersaurus?

©Matt Martyniuk

Jinfengopteryx was more troodontid than it was bird. However, it was every bit of a "dino-bird"in its feathering and general body shape. The retrices of Jinfengopteryx were fairly long, like those of a Black-billed Magpie or a Scissor-tailed Flycatcher. This recreation of the small troodontid shows that that wonderful tail in all its glory; it almost looks like a small bantam rooster. Notable exceptions of course are the clawed wings, recurved toe claws, and teeth (not visible here). The color scheme in this version of the illustration is different from that presented in Martyniuk's Field Guide; however, it is actually a slightly more colorful interpretation that is seen here as opposed to the book. Regardless, the bird-like posture is certainly recognizable and the wonderful little "dino-bird" comes to life very nicely.

Golden Herbivorous Phoenix

©Emily Willoughby

Jinfengopteryx elegans is bucking the trend, maybe, of following predators with herbivores that we normally ascribe to here in our rotation of fossil animals. It is also another very bird-like dinosaur and a theropod. Seeds discovered in the fossil evidence provided the stirrings of the hypothesis that the diet of Jinfengopteryx was that of an herbivore. The original description also claims that Jinfengopteryx should be considered one of, if not the most, basal bird so far discovered. However, it has since been assigned to the Troodontidae, as prescribed by Louis Chiappe. Regardless of its affiliations and diet, it is another "dino-bird" that may be quite a bit more interesting than it appears on its feathery surface.

At Least One Popular Outlet

Dinosaur Revolution was, for obvious reasons, the one outlet of popular culture that we know for sure had references to Rahonavis. The little "dino-bird" appears in many books, mostly those that are more technical in nature, but a few that are just a little more entertainment oriented; a quick search in a book list will turn up quite a few results. Possibly one of the lesser referenced but one of my more favored technical "guides" that discusses Rahonavis and shows a pretty, glossy, long tailed beauty of a "dino-bird" is Matt Martyniuk's A Field Guide to Mesozoic Birds and Other Winged Dinosaurs.

Menacing Clouds?

©Apsaravis (http://apsaravis.deviantart.com/)

Perhaps the menacing part of the name Rahonavis is meant to represent the difficult nature of the taxonomic argument that sometimes still swirls around it; it could also be in reference to the cloudy nature of the familial relationships. It was most likely not in relation to the idea that Rahonavis was a powered flier, as it appears to have lacked the ability to fly under its own power. Forster et al. asserted that Rahonavis and Archaeopteryx were related. The pelvic girdles of the two "dino-birds" are similarly adapted to flight, but appear to be independently derived. Other flight adaptations of the skeleton are manifested in the arms, including quill knobs raised on the ulna; these are present on extant birds. The dromaeosaurid characters of the skeleton have been discussed at length, but to summarize them again, we can say they are manifested most visibly in the feet and hands as well as the pubis, skull, and tail. The similarities between Rahonavis and dromaeosaurids appear to be more numerous than those between Rahonavis and birds; but does this make Rahonavis more bird-like than dinosaurian?

Open Source Dino-Bird

First and foremost, there is a paper on keratin immunoreactivity in Rahonavis in a 1999 JVP issue; I am not worried about talking about that one today because I do not want to. If you do want to read it it can be found on the Taylor and Francis website, however. The discussion of Rahonavis in the description and taxonomic discussion of a new dromaeosaurid from Mongolia (Mahakala omnogovae) is both open source, available online, and very, very interesting. The overall theme of the paper discusses the evolution of size prior to the advent of flight in birds. It is a topic I thoroughly enjoy, which may be why I encourage everyone to take the time to read it (open-source helps too, let's be honest).

Sounds of the Forest

Dinosaur Revolution featured Rahonavis. Today is one of those days that the video needs to speak for itself. It certainly can as well. Thankfully, there are two videos that show Rahonavis, so there is a lot of talking going on here.

Kiddie Dino-Birds

The best kids sites have nothing regarding Rahonavis. There are a variety of reasons that this has happened; however, there is information out there for younger readers on sites like About and a very small blurb on Enchanted Learning. A generic looking Rahonavis is even available for coloring either online or saving and printing via pdf. It is not the worst interpretation, but it is just a little bit more generic than one would hope for of course.

Dino or Bird?

Rahonavis is a borderline dinosaur that may potentially be a bird; as stated yesterday. Most of the illustrations that have been released since the naming and describing of Rahonavis in 1998 represent this overlap of morphologies. Rather than looking at those heavily dinosaur and bird influenced crosses of illustrative masterpiece, looking at the skeleton provides some of the best clues concerning the morphological characteristics of Rahonavis. As we can see in the skeleton, there are very avian characters in the forelimbs as well as the pectoral girdle. The sternum of Rahonavis is even a little keeled, allowing for the attachment of larger chest muscles; Rahonavis was probably not an actively powered flier. The hindlimbs and the pelvic girdle of Rahonavis are rather dinosaurian. The sickle claws on the feet as well as the orientation of the pubis are very dromaeosaurid. The skull fenestrations and teeth, the tail, and the ribs are also very dinosaur related characters seen in Rahonavis.