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Therizinosaurs!

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Therizinosaurs are some of the creepiest dinosaurs I can think of. Our dinosaur this week, Falcarius (One species: Falcarius utahensis), is considered a valuable transitional discovery between other theropods and true therizinosaurs. Study of this Utah discovery in conjunction with the recently discovered Beipiaosaurus from China have allowed researchers to discover a lot more and draw a lot more logical conclusions about the evolution of the family of therizinosaurs. Falcarius, meaning "sickle" in Latin, was named for its high curvature claws present on its hands. A fairly long dinosaur, Falcarius has quite a stretch at the neck as well as quite a reach with its forelimbs. Typical therizinosaurs are assumed to be some of the only theropods that are obligate herbivores; ornithomimids are the other major family of theropods thought to be partially herbivorous but are proposed to have been much more omnivorous in nature. Falcarius was discovered by Larry Walker in 1999 in the Crystal Geyser Quarry of eastern Utah. James Kirkland, who we mention a lot in Utah related paleontology, was called in to head the geological survey team in 2001 that began to recover the bones of this dinosaur from the quarry. By 2005 a couple of thousand specimens had been recovered comprising the total remains of at least 300 individuals. Since that time the number of specimens has increased to over 3000 in the original quarry and a second quarry has been discovered to also contain specimens of this animal. The name was officially given to the dinosaur in May 2005's publication of Nature by Kirkland et al., which we will visit later in the week.
Picture by Paul Fisk. Mounted at the Utah Museum of Natural History.

Some Short Anatomy

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©Gaston Designs
The arms of Falcarius are where the name came from, so we expect them to be pretty stunning. The large claws of the arm are just that; they are quite extraordinary in the world of an herbivorous dinosaur. Most herbivores either use size or speed to protect them from predators. Many have other forms of protection, such as safety in numbers, but the large claws of Falcarius would certainly have made formidable weapons for protection against predators. Additionally, the claws are situated much like those of a sloth, and as such, are fairly ideal for pulling branches to the animal rather than grabbing and grasping.

The teeth of Falcarius are rather peg-like. In some other animals, like Diplodocus, we find these sorts of teeth and they are mainly for sheering leaves off of the twigs and branches from which the dinosaur fed. Because of this it is also highly likely that Falcarius ate in a very similar manner. Use of the hand like that of a sloth, for pulling down branches, while the teeth strip the leaves from the plant. The teeth are not designed for crushing and chewing plant matter in a highly efficient manner. There are a few teeth that appear to be for crushing plant matter, but they are very few and more toward the posterior end of the mouth. This probably entails the use of a gizzard in the digestive system, though as yet we do not seem to have compelling evidence of this organ structure.

Falcarius, Too Scary for Kids?

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In terms of links friendly to younger readers Falcarius scores very low in search returns. That in itself is not a problem really, if there is someone around to help them read the harder to read items that are out there related to Falcarius. Intermittent internet issues today have made my search even more difficult as well. However, I did turn up some easier to understand fact pages through the Natural History Museum of Utah and Bob Strauss' writings for About.com. Both sites can be read by younger readers, but as they are not written specifically for younger readers, they may be a little higher reading level than I usually like to expose kids to. Tomorrow I should be able to find a bit more to share and will also hopefully have more time to share things as well.

Falcarius and the Video Question

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Discovery, a few years back, aired a show dedicated to Utah's dinosaur graveyard at Crystal Geyser Quarry. The show follows the evolution of a theropod line of herbivores from carnivorous ancestors and attempts to parallel that evolution with the initial radiation of dinosaur evolution from a single bipedal carnivore ancestor.

The show is separated into 5 clips and, for the time being exists on YouTube starting with the video shared here. Given the nature of Discovery shows being slowly taken off of the internet due to copyright rules, if you want to watch this online do so as quickly as possible!

Lindsay Zanno's Abridged Works

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Not that everything thing Lindsay Zanno has ever written has been about Falcarius or anything, but Dr. Zanno spent a good deal of time with Falcarius and wrote, or coauthored, quite a few articles about different aspects of Falcarius' anatomy. We know quite a bit about Falcarius thanks to the work of many different paleontologists, but the names that came up the most in the early articles were Zanno, Kirkland, and Sampson; coincidentally, the tooth shape mention I made on Saturday was corrected by Dr. Kirkland, if anyone missed that. In 2005 Kirkland et al. officially named Falcarius (an article that can be found here) and described the animal in a short but detailed paper. Phylogenetic analyses from this paper placed Falcarius as the "basalmost therizinosauroid known". Zanno went on the next year to analyze the pectoral girdle and forelimb of Falcarius, which is of interest to everyone given those rather unique and interesting claws. She discusses clade placement in the paper, which is very interesting, but if anyone was wondering what the range of motion for that nifty forelimb was, that is also addressed, so no worries! The systematics lovers that are now appalled at my casual dismissal of the former part of the 2006 Zanno paper should try to find a copy of Zanno's 2010 article examining the osteology of Falcarius and placement of Falcarius and other basal therizinosaurs within their family and clade. It makes up for my dismissal of the previous papers section on systematics, I promise.

More Than Arms

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Falcarius is so much more than arms and leaf shaped teeth. It is a rather long dinosaur that tells us a lot of information about the other members of its family both before and after it in addition to being a member of that very unique family. Falcarius has a long neck and a long tail counterbalancing that neck and its bipedal stance allows for a great reach with the head that is on the end of the neck. The arms of Falcarius were also unique in that they were robust and were capable of extending through a rather interesting range of motion. Though very much like their Maniraptora sisters, Therizinosaurs developed a different set of motions in their forelimbs. In fact, Zanno 2006 states that 20% of the synapomorphies of Maniraptora and Therizinosaur actually show that Therizinosaurs were reversing their pectoral girdle conditions and thus the range and types of motions they were capable of producing in their forelimbs. Twenty percent is a significant change from similar animals. Not requiring their forelimbs to grapple with prey and instead using them in a different manner entirely, such as reaching for vegetation, would certainly alter their range, and therefore their anatomical makeup, significantly over many generations. This, then, makes sense that Falcarius is little changed as a basal ancestor, but the fact that it still possesses many of those changes and represents transitional stages of those changes is significant.
References:
L. E. Zanno. 2006. The pectoral girdle and forelimb of the primitive therizinosauroid Falcarius utahensis (Theropoda, Maniraptora): analyzing evolutionary trends within Therizinosauroidea. Journal of Vertebrate Paleontology26(3):636-650

Famous Falcarius

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Falcarius, as noted on Monday, was the subject of its own dedicated documentary produced by the Discovery Channel. The fame, however, does not stop there. Falcarius has also been modified into games, or just plain created as a character in some people's games.



Falcarius has also appeared in a few books, some about feathered dinosaurs. This assumes, and it appears to be the general consensus at the moment, that Falcarius was at least partially feathered. Drawing it with the steps in a dinosaur how-to-draw book also includes feathering, which is usually fairly difficult for most amateur artists that are using how-to-draw books. Toys and statues have also been created by companies and artists depicting Falcarius. Cartoons, our semi-normal fame related outlet, seem to be lacking when it comes to Falcarius, strangely.



New Old Partial Dinosaurs

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©Mark Witton
The original material of Nyasasaurus (Nyasasaurusparringtoni) was a partial skeleton described in the 1956 doctoral dissertation of Alan Charig. The material was minimal, consisting of a humerus, three sacral and three presacral/thoracic vertebrae. A second specimen exists, also minimal remains, consisting of a trio of cervical vertebrae and two postsacral/caudal vertebrae. Nyasasaurus was discovered in central Africa near Lake Nyasa (also known as Lake Malawi) in Tanzania. The skeletal elements were discovered in the early 1930's by Francis R. Parrington, and is now considered to represent what is possibly the oldest dinosaur known. Living with cynodonts, rhynchosaurs, and other therapsids and diapsids, Nyasasaurus dates from around 243 MYA, approximately 30 MY prior to Coelophysis. Perhaps, thanks in part to a paper published within the last year, we can definitively assign Nyasasaurus to a family, but for today, remember that it is considered one of the most basal dinosaurs and that it is most certainly an Archosaurian animal.

Camera Shy

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©Nobu Tamura
Nyasasaurus, in part due to the fragmentary nature of the few remains that have been recovered, is not represented in images often. In fact, only two or three images of the dinosaur exist in the public domain. One of these is a bubble representation of proposed or predicted biomass of the dinosaur as extrapolated from the measurements of the available bones. Of the other two, one indicates herbivorous behavior and the other omnivorous or carnivorous features are highlighted. The image show here is the latter. Both body types work, especially given that we are missing a lot of the information needed to correctly reconstruct the body. That said, compare today and yesterday's images and feel free to discuss the positives of both bodily representations as each interpretations has both merits and negatives as well.

Coloring A Rare Dinosaur

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Nyasasaurus remains are rare and websites designed to educate children specifically about Nyasasaurus are pretty much non-existent. The best to offer in terms of that is the About.com page about Nyasasaurus. That page is another perspective showing Nyasasaurus as a carnivorous dinosaur. This is a coloring page that sort of makes up for the lack of information available to younger readers, but given the lack of information all around concerning Nyasasaurus it is not too amazing that there is not as much to share with any specific age groups about this dinosaur.


Radio Programs

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Nyasasaurus does not have any dedicated videos; however, there was a radio program last year, Quirks and Quarks, that is hosted by CBC. The interview is fairly informative, and it is a nice listen. I think today I will let the radio do the talking and make this a very short post!

Southern Dinosaurs

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Support for the hypothesis that dinosaurs originated in the southern areas of Pangaea are explored in a paper that was begun by Alan Charig's colleagues with his help and then finished posthumously in December of last year. The paper is the same research referenced in the radio interview posted yesterday. The paper identifies Nyasasaurus as either the earliest dinosaur or the sister taxon of the Dinosauria. The age of the fossils are explored as well, extending the origin of the Dinosauria backwards in time, making the group older than previously thought. The paper can be retrieved from an outside site not associated with the Royal Society, but be aware that there are copyright rules to be observed and respected and do not be amazed if the link stops working sometime given those things.

The Minimal Facts

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It is always a difficult call to make when a scientist or group of scientists name a new species on very little material. Nyasasaurus is based on such little material that it is almost amazing that we can even consider it definitively a dinosaur. Looking back at papers that we have read this week it is apparent that there were enough characters to definitively announce Nyasasaurus as a reptile and, based on the consensus interpretation of the characters it does appear to be one of the most basal dinosaurs. The vertebrae are scattered around the body (a handful of cervical, a couple thoracic, and a few post-sacral) and the only other bone available for comparison and analysis is a humerus from the right forelimb. This bubble drawing was created to represent the potential area of the body and its dimensions:

No One Knows Me

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Nyasasaurus is a little known dinosaur. Even the name of the lake that lends its name to the dinosaur has changed in the years since it was discovered and initially named. Nyasasaurus is included in some encyclopedic works on dinosaurs but does not have its own specialized books (neither those geared toward scientists or general audiences). Nyasasaurus did gain some popularity in the media when the latest study named it as one of the oldest dinosaurs to have existed. Images of Nyasasaurus that were shared due to this news were typically snippets of the Mark Witton illustration shown here earlier in the week; however, images from the study were also shared with the public. Probably the best image was the one shown below which highlights some of the better aspects of the discovered bones and has cross sections of the humerus shown as well, for all of the histology fans out there.
The humerus specimens of Nyasasaurus parringtoni seen in (a) anterior and (b) posterior views, as well as (c) complete cross-section in transmitted light, (d) cross-section through the entire cortex, and (e) cross-section through the outer portion of the cortex. (f) Rearticulated sacrum in right lateral view with interpretive drawing. (g) Posterior presacral vertebra in right lateral view. (h) Partial posterior presacral vertebra in dorsal view. (i) Anterior cervical vertebra in left lateral view with interpretive drawing. (j) Anterior cervical vertebra in left lateral view with interpretive drawing. Scale bars: (a,b,f-j) 1 cm, (c) 4 mm, (d) 1 mm, (e) 500 nm.

Surprise Mammals!

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We have discussed mammals here before, and usually I announce when we will deviate from our dinosaur topics, but I received a very kindly worded request not too long ago to discuss mammals again and I wanted to surprise everyone, request maker included, rather than build up anticipation, etc. However, it is a great pleasure to deviate from the norm for the month of September and discuss, though not my favorite group in the wide world of animals, the mammals of the early days of the age of mammals. Technically I have mentioned this week's little mammal before on here. A while back when discussing the age of giant birds I discussed very briefly a prey item for some giant birds; a small mammal with shrew-like qualities and the locomotion of a tiny kangaroo: Leptictidium. Leptictidium is a genus comprised of five species: L. auderiense, L. ginsburgi, L. nasutum, L. sigei,and L. tobieni. These small mammals were forest dwelling bipedal insectivores that were successfully spread across the forests of Europe during the Eocene but went extinct as the forests gave way to open grasslands in the Oligocene. Today they have left us with no descendants and little soft anatomy, but a fair assortment of well preserved skeletal anatomy.

Small Fossils

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Leptictidium nasutum
Leptictidium is actually a fairly exceptional little mammal. The general rule in fossils is that the smaller you are the more likely it is that parts of your body, or the entirety of your remains, will be lost over millions of years. However, Leptictidium fossils are fairly abundant and not only of good quantity, but also of good quality; many of the fossils found are entire or nearly entire skeletons. This is due in part to the fact that these fossils are slightly younger than the fossils we typically discuss and because these small mammals lived in the underbrush of forests. The underbrush of forests contain a lot of materials that can quickly bury animals and, in forests near swampy lands, the additional material inundating the forest floor during flood events also added to the positive preservational bias. Additionally, forest fires, a common occurrence in a natural system, would have caused the suffocation and burial of these small mammals fairly easily. Regardless of the method of preservation or reason for exceptional preservation, numerous well detailed individuals have been discovered and unearthed throughout Europe and a great deal of the anatomy of Leptictidium is known and can be studied in the future as well.

BBC model
The fleshing out of past creatures is often difficult without skin impressions but, again thanks to the wonderful preservation of specimens of this animal, the fleshy details of Leptictidium are a little more well known. In some instances the overall body shape of the soft anatomy of Leptictidium has been preserved as a carbonized film that looks like a dirty halo around the skeletal fossil. The finest details of the face have been little preserved, but extrapolations have been fleshed out using what details have been preserved and with modern analogues filling in any gaps of hypothetical behavior and form. The analogue most often used for Leptictidium are the elephant shrews (Family Macroscelididae) of Africa. Also insectivorous, the features that make elephant shrews successful have been incorporated into Leptictidium, to a point, to make up for missing details of the soft anatomy and the comparison between the two sets of animals has drawn parallels and enhanced understanding of the skeletal structures as well. The proboscis seen in documentaries and in many fleshed out illustration is based in large part on the elephant shrew proboscis, which is actually kind of funny to see in action.

Firendly Little Guys

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There is not a doubt that Leptictidium falls into what the internet is these days calling the "dawwww" and "squee" categories of adorable little animals and the genus is as such expected to be a hit with the kids of the world. Not as many sites exist for fossil animals outside of the Dinosauria, however. About's Bob Strauss has written another succinct and well delivered page on Leptictidium that would be suitable for younger readers, and that is a good thing. Australia's version of of ABC has a question and answer page up about Leptictidium that would most likely be of interest to younger readers as well.

Leptictidium Hopping Into Your Heart

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Leptictidium is a bouncy little mammal. As such, the videos we have for Leptictidium are very "hoppy". In the words of LeVar Burtan, "you don't have to take my word for it", just watch this:




Follow the Bouncing Mammal

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It is something like follow the bouncing ball, but furrier and probably a little more dangerous than a ball, because Leptictidium has some good size teeth. The postcranial skeleton of Leptictidium has been studied and described many times over, as well as compared across time and formations. In 2006 the Eocene Leptictidium and Early Oligocene Leptictis, of Europe and Wyoming respectively, were compared. Unfortunately that paper is not so easy or free to get a hold of as Meehan and Martin's paper detailing the discovery of those Wyoming Leptictid mammals, those this time from the Paleogene. Reading about even similar small mammals is interesting, but it would be very nice to be able to read the original Storch and Lister paper naming and describing Leptictidium nasutum if you have that ability. It is not apparently available widely online and it is only in German it appears.

Choosing Wisely

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There is so much interesting anatomy, I admit it as someone that does not enjoy studying mammals typically, to choose to discuss today that I am not sure if I want to look at the hindlimb or the nasal trunk of Leptictidium; we are probably lucky that I narrowed it down to those two anatomical features honestly. The hindlimbs of Leptictidium were specialized locomotive machines much like those present in extant kangaroos and rabbits. The kangaroo rat actually provides some very likely mechanics for the movement of Leptictidium through the underbrush.

The fact that it could hop at speed probably made evasion of predators its most likely defense mechanism and, depending on the musculature associated with individual specimens and species, the speed of the Leptictidium and range or types of predators able to chase down the little mammals was probably different in different ecosystems and time periods. To my knowledge mechanical studies have not been done comparing the speeds and gaits of different species of Leptictidium. It is probably important to note that the relaxed gait is not strictly representative of the speed of any individual within a species.

The nasal trunk of Leptictidium that is thought to exist in these small mammals would have more than likely contained some highly sophisticated olfactory senses as it was more a proboscis than it was an actively foraging trunk used for manipulating objects. The dedication of senses in the trunk would allow this small mammal to actively forage day or night and, with other heightened senses nocturnal life would have been an advantageous mode of life for Leptictidium. Considering, however, that the orbits do not seem to be exceptionally large or geared toward containing eyes that were adjusted to a nocturnal lifestyle, it appears to be more likely that Leptictidium was a crepuscular (dawn and dusk) predator of insects. Then as now insects would have been very active at dawn and dusk and Leptictidium could have used its heightened senses of smell and hearing to detect insects foraging at a distance and hidden by dense vegetation from the sight of Leptictidium.
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