• Category Archives Uncategorized

  • A critical evaluation of Tianyulong confiusci – part 2

    Posted on by Jura 3 Comments

    Continuing from yesterday, the following is what I garnered from the Tianyulong confiusci specimen announced last week.

    When looking at the fossil, a couple preliminary questions came to mind.

    1. Is the fossil real?

    2. Is the integument real feathers/protofeathers?

    Is the fossil real?

    Main slab for _Tianyulong_ with highlights showing the breakage in the slab
    Main slab for Tianyulong with highlights showing the breakage in the slab. Click the image to enlarge.

    The initial paper gives no mention of how the fossil was collected (i.e. if it was collected by local farmers – as most of these fossils are – or if it was found in the field), so it is hard to tell how many hands this fossil has passed through before it was described. The specimen is broken into at least 3 different slabs (as shown in the first pic. Highlights [mine] show where breaks occur). The first, and most obvious, is across the top of the body, separating the dorsal vertebrae from the rest of the fossil. The second break, is a little less obvious. It appears to neatly separate the anterior part of the body, from the posterior part (pretty much right before the hip). It’s hard to tell from the photos, but this section might have been glued together. Whether this was before it reached the scientists, or after is left unclear. So there is room for suspicion there. The characters used to determine heterodontosaurid affinities come exclusively from the skull. The preservation of the hip makes it very hard to tell what one is looking at. The ischium appears quite a bit thicker than in Heterodontosaurus tucki. This could be chalked up to generic difference, or even an ontogenetic one. The authors mention the presence of extensive ossified tendons on both dorsal and ventral sides of the caudal vertebrae. This is actually unusual for an ornithopod. Ossified tendons tend to be arranged in a lattice-like geometry throughout the dorsal portions of the caudal verts, but not the ventral side. Tianyulong not only has ossified tendons on both dorsal and ventral sides of the caudals, but they are arranged in a parallel fashion rather than the more typical lattice work. This sounds much more like what one would expect to see in a dromaeosaur, not a heterodontosaurid. Especially since the eponymous Heterodontosaurus lacked ossified tendons. This would make this tendon arrangement both unique for heterodontosaurs, and unique for ornithopods.

    Incidentally, there is yet another crack that separates this section of the tail from that of the proximal (and apparently tendonless) portion of the tail. It doesn’t look like the crack goes all the way through the slab, but this can’t be verified from the photos. Nonetheless, this is yet another cause for skepticism.

    Another bit of strangeness is the presence of an apparent stain along most of the skeleton. It appears as a lighter, white colour, and is found within the body cavity, and along the back and tail. This might have been caused by the dissolving of the soft tissue. Whatever it is, this stain cuts off all the apparent filaments from the rest of the skeleton (save one small section that will be described later). In fact, there is one part where the stain appears to cut ? rather sharply ? right through the tail filaments. This cut is at an angle to the tail, thus not following the body contour at all. In fact, it almost looks like a deep gouge like that caused by a shovel, or (in this case) a trowel. Perhaps this was a casualty of the preparation/excavation.

    After looking the fossil pictures over, I have to say that Tianyulong more than any other “feathered dinosaur” before it, has the potential to be a chimera.

    Is the integument protofeathers/feathers?

    Well, the answer is an emphatic no to the latter. These are definitely not feathers.

    So then are they protofeathers?

    In the paper, Zheng et al mentioned that the filaments bear a similarity to both the “quills” on Psittacosaurus , and the protofeathers of Sinosauropteryx. Curious; I decided to compare the three.

    Comparison of the _Psittacosaurus_ "quills" (top), _Sinosauropteryx_ protofeathers (left) and _Tianyulong_ "filaments" (right)
    Comparison of the Psittacosaurus “quills” (top), Sinosauropteryx protofeathers (left) and Tianyulong “filaments” (right). Click the image to enlarge.

    Right off the bat, I’d say one can dismiss any real relationship to the protofeathers of Sinosauropteryx. The filaments on Tianyulong are similar only in the sense that they don’t branch at all. Short of that, the size, and density of Tianyulong‘s filaments are quite different from those of S.prima (being wider, longer and more loosely packed).

    When compared to the “quilled” Psittacosaurus, a much greater similarity can be seen as both filaments are rather long. The Psittacosaurus “quills” however, are quite a bit thicker, and seem to show up within the skin, while Tianyulong‘s filaments don’t touch the skeleton at all, save for the same spot where the strange (possible) groove is found.

    Some folks have stated that the large filaments are focused on the caudal portion of the body, just like in the “quilled” Psittacosaurus specimen. I would caution against this. Most of Tianyulong‘s body is not preserved. Unlike the Psittacosaurus specimen, where one could tell that these “quills” appeared only on the tail, there is very little evidence for the same arrangement in Tianyulong. I would extend this caution to statements about Tianyulong being completely fuzzy too. There are some filaments found by the dorsal vertebrae and under the cervicals. However, these filaments are much removed from the body. The dorsal patch does not follow the arch of the vertebrae; instead lying more anterior to the bones. As for the ventral patch, unless one wants to posit a double chin on Tianyulong, they also don’t actually associate with the bones, nor do they follow the body contour.

    The caudal filaments are strange in their own right. Like all the rest of these filaments they don’t follow the body contour (compare, for instance how the protofeathers of Sinosauropteryx follow the body rather tightly). In fact many of these filaments seem to be tangled amongst each other.

    Note there is yet another apparent break in the slab, between the filaments.

    If everything is arranged correctly, then these filaments seem to be tangling up with filaments that would have emerged much further up the back. Also unlike the singular “quills” on the Psittacosaurus, these thinner filaments all appear to protrude from the same narrow area. Instead of being more evenly spaced along the caudal vertebrae, they all bunch up by the proximal caudals. If these filaments did belong to the living animal, then it would appear that Tianyulong was brandishing a “smokestack haircut” long before Kid from Kid and Play ever did.

    Final verdict:

    Readers will no doubt have noted my extensive use of quotes around certain instances of protofeathers, as well as the mention of quills in the infamous Psittacosaurus specimen. I do so because of the questionable assignment of these filaments to those particular structures. In doing so, I am following in the steps of David Hone, who also suggested that one be cautious with one’s interpretation of some of these Yixian fossils (though my view is a little more extreme). Many of them have been described briefly, with little follow up work. The Psittacosaurus with the “quills” is a particularly nasty case. It received a quick right up in Nature, before it was discovered that the specimen was illegally collected. Now there is a veritable “shit storm” surrounding the fossil. This has resulted in it becoming a pariah that no journal dare touch. A result that has essentially put a halt to any further research for now. It’s unfortunate, as the identity of the Psittacosaurus filaments remains in limbo (not everyone is “happy” with the diagnoses of quills).

    As for Tianyulong, there appears to be a fair amount of evidence to suggest the animal might have died on a plant, or was possibly being devoured by nematode like parasites prior to death. As for being protofeathers, they appear as unlikely in Tianyulong, as they do in Psittacosaurus. The relationship to the protofeathers of Sinosauropteryx prima, appear to be at the most basal geometric level (i.e. they are both straight and unbranching).

    Still, what if everything is genuine? What kind of implications would that hold for dinosaurs?

    For my answer to that, stay tuned.

    ~Jura


    This entry was posted in Dinosaurs Uncategorized and tagged

  • A critical evaluation of Tianyulong confiusci – part 1

    Posted on by Jura 2 Comments

     

    Tianyulong

    Apologies to all for the delay between blog posts. It seems I really should avoid putting deadlines on these things, as every time I do so, something in real life pops up to divert my attention.

    I have since had the chance to examine the Tianyulong confiusci paper thoroughly. My initial trepidations about the fossil remain. Tianyulong is a very important find…if what it preserves is real?

    As I sat to write this post up, I watched as the pages piled up. Because of the unexpected length of the post, I decided to break this evaluation into two, or three parts (likely three, but I’m covering my bases just in case). This first part has little to do with T.confiusci, and is mostly a primer for what’s to come. Tune in tomorrow for the meat of this post.

    The story thus far

    In the interim between blog posts, Time.com has published an article on the Tianyu museum in Pingyi China (home to T. confiusci). This natural history museum has quite possibly the largest collection of fossils in the world. Their dinosaur hall alone features some 480 fossils randomly on display. The issue is just how authentic they all are.

    From the article:

    Tianyu has purchased most of its fossil collection from individuals an illegal practice permitted by authorities only because it is technically a state-owned institution. More problematic, however, is that there is no way of knowing how many of those fossils are real. Chinese scientists say fake fossils are so pervasive in Chinese museums that using authenticity as the basis for judging a collection’s worth is unrealistic.

    This has been a rampant problem in China for some time now (~10 years at least). While here in the states, paleontologists have to worry about the locality in which a fossil bought at a shop, or auction, was collected (both for legal purposes, as well as scientific documentation); fossils in China also bear the burden of possibly being faked. Fossil poachers in China know what types of fossils are preferred (“feathered” dinosaurs in particular), and have gotten very good and making fakes. So good in fact, that a thorough vetting of any major find in China should really be done. Some authors have already started inventing techniques for doing just that (Rowe et al 2001, Mateus et al 2008).

    Sadly a thorough vetting process remains the exception, not the rule for Chinese fossils. Only two major dinosaur finds have been authenticity tested. The first was the seminal “feathered dinosaur”: Sinosauropteryx prima (Chen et al 1998). The second was NGMC-91; otherwise referred to as “Dave” (Ji et al 2001). This specimen is believed to be a member of another “feathered dinosaur:” Sinornithosaurus milleni.

    Technically there was one more specimen that has received authenticity testing, but I’ll get to that in a bit.

    Photo from National Geographic's 1999 mag.

    It really seemed that once Sinosauropteryx was found to be authentic, many of the other “feathered” finds were given a free ride. Within a year’s time four separate “feathered” dinosaurs were published in Nature. There was the therizinosaur Beipiaosaurus inexpectus (Xu et al 1999a), along with Caudipteryx zoui, Protarchaeopteryx robusta (Ji et al 1998) and the dromaeosaur Sinornithosaurus milleni(Xu et al 1999b). All were preserved with variations of what seemed like “feathers” (generally referred to as protofeathers now). None appeared to have been given an authenticity test, and were (for the most part) presumed to be the real thing. Protofeathers became something to be expected from Liaoning province. If someone posted a news article about a dinosaur fossil from the Yixian formation, it was practically a given that the animal would have protofeathers of some sort.

    Then, in November of 1999, National Geographic reported on the discovery of yet another “feathered dinosaur” coined: Archaeoraptor liaoningensis (Sloan 1999) The animal was found with the true feathered wings of a bird, along with a feathered dromaeosaurid legs and tail. Though informally published by National Geographic (who had jumped the gun on the story), it was nonetheless accepted by the paleo community.

    As the weeks passed, the validity of Archaeoraptor started to get called into question. The specimen itself consisted of numerous slabs that were glued together. This was suspicious, but not surprising given that the shale of the Yixian is weak. There were some mentions of it being a chimera (one leg was apparently longer than another), but regardless, it was generally believed to be the real deal (I even had a chance to ask one of the paleontologists working with it, Phil Currie, about it’s validity, and he felt it was genuine).

    Finally, after thorough examination, it was found that “Archaeoraptor liaoningensis” was indeed a fake. The animal was a chimera composed of a bird (front half), the feathered dromaeosaurid Microraptor gui, and a third, unnamed animal. Alas, despite the apologetic retraction from National Geographic, the damage was done. The Archaeoraptor hoax was well publicized around the internet. In particular, on the websites of creationists who toted it as the newest Piltdown man (the fact that both Piltdown and Archaeoraptor were found to be hoaxes through the use of science [Rowe et al 2001], seems to be a fact that is lost by creationists).

    Archaeoraptor stood as a cautionary example of why a thorough vetting process should be undertaken for important Chinese discoveries. Especially if they come from the remarkable shales of the Yixian formation.

    Now, 10 years later, the Yixian continues to pump out new and amazing finds. Unfortunately, it also continues to pump out numerous forgeries; many of which are very well done. Despite what happened with Archaeoraptor, there is still a distinctive lack of authenticity testing going on for these fossils. So there remains a good chance that some of these “feathery” finds are not what they appear to be.

    Which brings us to our “feathered” heterodontosaurid: Tianyulong confiusci.

    Tune in tomorrow for the analysis.

    References

    Chen, P., Dong, Z.,Zhen, S. 1998. An Exceptionally Well-Preserved Theropod Dinosaur from the Yixian Formation of China. Nature. Vol. 391: 147-152.
    Ji, W., Currie, P.J., Ji, S., Norell, M.A. 1998. Two Feathered Dinosaurs from Northeastern China. Nature. Vol. 393: 753-761.Ji, Q., Norell, M.A., Gao, K. Ji, S., Ren, D. 2001. The Distribution of Integumentary Structures in a Feathered Dinosaur. Nature. Vol. 410:? 1084-1088.
    Mateus, O., Overbeeke, M. and Rita, F. 2008. Dinosaur Frauds, Hoaxes and “Frankensteins”: How to distinguish fake and genuine vertebrate fossils. Journal of Paleontological Techniques. Vol.2:1-5
    Rowe, T., Ketcham, R.A., Denison, C., Colbert, M., Xu, X., Currie, P.J. 2001, Forensic palaeontology: The Archaeoraptor Forgery. Nature. Vol. 410: 539-540. doi: 10.1038/35069145Sloan, C.P. 1999. Feathers for T.rex?. National Geographic. Vol. 196(5): 98-107.
    Xiao-Ting, Z., You, H., Xu, X., Dong, Z. 2009. An Early Cretaceous Heterodontosaurid Dinosaur with Filamentous Integumentary Structures. Nature. Vo.. 458: 333-336.
    Xu, X., Tang, Z. Wang, X. 1999a. A Therizinosauroid Dinosaur with Integumentary Structures from China. Nature. Vol. 399: 350-354.
    Xu, X., Wang, X., Wu, X. 1999b. A Dromaeosaurid Dinosaur with a Filamentous Integument from the Yixian Formation of China. Nature. Vol. 401: 262-266.

    This entry was posted in Dinosaurs Uncategorized and tagged

  • Feathers in ornithischians? Probably not.

    Posted on by Jura Comment

    Easily the biggest news of the day is the finding of alleged “proto feathers” or “dino fuzz” in an ornithischian dinosaur. For the most part this quick post is just going to add to the echo chamber of Tianyulong confuciusi posts and link redirects that are currently popping up around the web.

    The news comes following a paper by Xiao-Ting et al, in the journal Nature.

    The paper’s title is:

    Xiao-Ting, Z. , Hai-Lu, Y.,? Xing, X. and Zhi-Ming, D. 2009.? An Early Cretaceous Heterodontosaurid Dinosaur with Filamentous Integumentary Structures. Nature. Vol. 458 : 333-336.

    I won’t be able to read over the article until tomorrow (at which time I will return to this).? Judging from its brief 3 page spread, I expect this discovery to be as briefly documented as the alleged feathers on Psittacosaurus find from a few years back.

    Nonetheless, as with the Psittacosaurus find, the news outlets and dino fan sites (including the Dinosaur Mailing List) are all a buzz with “feathered” dinosaur news and how it relates to the origin of feathers themselves.

    Unfortunately what I don’t see (and didn’t see in many of the previous “dino fuzz” finds) is any real vetting behind the find.? According to the news outlets, the authors seem pretty set on these structures being related to feathers in some way. No mention has been made of them being possible contaminants from where the animals died (i.e. plant material, or stains from parasites), or even a possible forgery (as it does come from Liaoning Province; which is well known for their forged fossils). Furthermore, the description of the find sounds much more like the “quill” like structures that are presumed to be on psittacosaurs, than it does the “dino fuzz” present on Sinosauropteryx.

    Thankfully there have been a few voices of reason/skepticism out there.

    Dr. Larry Witmer of Ohio University offerred some alternative possibilities:

    …it is unclear at this point if Tianyulong‘s feather-like structures are part of the same evolutionary lineage as the feathers on today’s birds and the same lineage that yielded the proto-feathers on early theropods. Also, it’s possible that the Tianyulong feather-like structures really occurred under the skin, not outside it. That would change all these arguments, suggesting that the structures are collagen features in the skin, not feathery.

    — Live Science

    Additional caution came from Luis Chiappe of the Natural History Museum of Los Angeles:

    But Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County, who has written about the origin of feathers, said he doubts that feathers evolved outside of theropods and birds. Interpreting Tianyulong‘s filaments as early feathers is questionable because of their appearance, he said.

    Moreover, Chiappe said, given the apparent lack of feathers in many dinosaur species, “I don’t see any reason why you’re going to conclude that feathers must have originated before the origin of dinosaurs or (at) about the same time.”

    — AP News Feed

    At this point I will withold my conclusions on this until I’ve read through the paper, and compared it with some of the other “feathered” dinosaurs.


    This entry was posted in Dinosaurs Uncategorized and tagged

  • Two new paleo-herps illustrate the problems of a persistent reptile myth.

    Posted on by Jura 5 Comments


    v

    Titanoboa picture by the paper’s co-author: Jason Bourque

    I was trying to wait until I could nab the papers for these guys, but since Geology does not feel like updating their site, I’m going to have to move without them.

    Reported on 1st February, John Tarduno of the University of Rochester, and his team have discovered an alleged freshwater turtle fossil in the Canadian Arctic. The animal – given the gorgeous name of Aurorachelys (“Dawn turtle” or “Arctic turtle” as the case may be) – was found in strata dating back to the late Cretaceous. According to the press release (which is all I have to go on at the moment), the presence of the turtle has lead Tarduno and his colleagues to suggest the presence of an immense halocline in the paleo-arctic ocean.? According to Tarduno:

    …the Arctic Ocean was more separated from the rest of the world’s oceans at that time, reducing circulation. Numerous rivers from the adjacent continents would have poured fresh water into the sea. Since fresh water is lighter than saltwater, Tarduno thinks it may have rested on top, allowing a freshwater animal such as the aurora turtle to migrate with relative ease.

    The other major discovery came out today in Nature.? Researcher John Jason Head, and colleagues have discovered the world’s largest snake. The new snake has been dubbed: Titanoboa cerrejonensis, and it has been estimated to grow to a whopping 13 meters in length (43ft) and could have weighed as much as 1,135kg (2,500lbs).? The fact that this immense animal even existed, is amazing enough, but the researchers took their find a little further.

    Since snakes are poikilotherms that, unlike humans, need heat from their environment to power their metabolism, the researchers suggest that at the time the region would have had to be 30 to 34 degrees Celsius for the snake to have survived. Most large snakes alive today live in the South American and southeast Asian tropics, where the high temperatures allow them to grow to impressive sizes.

    This is where I have my problems. First for Aurorachelys; how are the researchers determining that this animal was a freshwater turtle? As I mentioned prior, I have not had a chance to read either of these papers yet, but just off the top of my head, I can’t think of any specific osteological trait that can be used to determine whether an animal is capable of salt-excretion (i.e. marine). Edit: See Nick’s comment for a list of papers on osteological correlates to salt excretion. This is what I get for posting something right before bed. 🙂? Are the researchers, instead, using the extant phylogenetic bracketing method (EPB), and figuring that Aurorachelys was a freshwater inhabitant, based of critters it was most closely related to?

    If it’s the latter, then I have reason to pause. Uniformitarianism, or the assumption that present day processes are likely the same now as they were in the past, is a very useful tool.? It’s especially useful in the realm of geology, where rock cycles are unlikely to have changed.? In biology, too, uniformitarianism can be helpful for studying processes like evolution and ecological partitioning. However a uniformitarian view of life is much less sturdy when dealing with more labile things like behaviour, or the evolution of a specific trait. If the researchers are assuming that Aurorachelys was a freshwater animal based off of EPB, then I would have to assume that salt excreting glands must be a hard thing to evolve. But are they? I’m not sure we have an answer there.

    Another issue this raises is, if Aurorachelys was a freshwater turtle that was cast adrift, then what are the chances that it would have been fossilized in the first place. Fossilization is a one in a million process as it is. In general, parsimony tells us that unique individuals / behaviours, are unlikely to be preserved. When we find a giant representative of a species, it probably was not unique, but rather a high end average animal. So too, it would seem, with Aurorachelys.? It is highly unlikely that this turtle was caught out of its element.? This may mean that this large halocline was present and that freshwater turtles were undertaking this migration rather often, or it means that the ability to remove excess salt from the body, was present in this species. Interestingly, a similar situation exists for the giant alligatoroid Deinosuchus. Salt excreting glands appear to be a unique adaptation of crocodyloids,? and not their alligatorish kin. Yet Deinosuchus founds some way to cross the saltwater filled Western Interior Seaway. Again, how hard is it to evolve salt removing glands?

    The case of Titanoboa cerrejonensis is much the same. In this case, it appears to be a clear case of the erroneous belief that reptiles make good ecological thermometers; despite the presence of leatherbacks (Dermochelys coriacea) in the freezing Northern Atlantic, or the small Chinese alligator (Alligator sinensis) living in a part of China that readily freeze, or even the relatively tiny Andean lizards ((Liolaemus multiformis), who live in parts of the Andes mountain range that experience an average daytime temperature of 10°C (50°F) , all while maintaining body temperatures of 35°C (95°F). Both the Aurorachelys and Titanoboa cerrejonensis papers appear to make assumptions that seem questionable given the evidence.? However I will reserve final judgement until I’ve had a chance to read the respective papers. Hopefully there is some hard evidence to back up the assertions that have been proposed.


    Photo by Ray Carson

    Photo by Ray Carson

    Until then, check out the comparison on the vertebrae of a large Eunectes murinus (green anaconda) and Titanoboa cerrejonensis. This beast was huge.

    Papers

    Head, J.J.,Bloch, J.I., Hastings, A.K., Bourque, J.R., Cadena, E.A., Herrera, F.A., Polly, D.P., Jaramillo, C.A. 2009.
     Giant Boid Snake from the Palaeocene Neotropics Reveals Hotter Past Equatorial Temperatures. Nature. Vol 457 :715-717
     doi:10.1038/nature07671

Vandermark, D., Tarduno, J.A., Brinkman, D.B., Cottrell, R.D., Mason, S. 2009. New Late Cretaceous Macrobaenid Turtle with Asian
    ?Affinities from the High Canadian Arctic: Dispersal via Ice-Free Polar Routes.Stephanie Mason. Geology, Vol 37.

    This entry was posted in Extinct Reptiles Uncategorized and tagged

  • One more reason why David Attenborough is cool.

    Posted on by Jura 1 Comment
    David Attenborough doing what he does best.
    David Attenborough doing what he does best.

    For anyone who enjoys nature documentaries, Sir David Attenborough is a household name.? His team is easily responsible for some of the best nature docs ever created (e.g. Planet Earth, Blue Planet, Life in the Undergrowth and of course: Life in Cold Blood).? A stranger to retirement, the? 82 year old documentarian extraordinaire is showing no signs of slowing down.

    His latest doc is on the bicentennial anniversary of Charles Darwin’s birth.

    As I have alluded to before,? I find Attenborough and his team’s work on nature docs to be of the highest calibre partly because they don’t hide the science from the viewer. Often, Attenborough’s team works hand in hand with scientists,? which has lead to the filmmaker’s capturing information that has never before been documented by science (e.g. new species, or new behaviours). Well now there is one more neat thing to add to the list. Sir David takes no shit from creationists.

    In an article from the U.K.’s Daily Telegraph,? Attenborough talks about the hate mail that he receives from creationists,? and how he deals with it. Rather than go the brash Richard Dawkins route,? Attenborough seems to prefer a more matter of fact approach.? It’s hard to argue with the results.

    http://www.telegraph.co.uk/culture/tvandradio/4345830/Sir-David-Attenborough-I-get-hate-mail-telling-me-to-burn-in-hell-for-not-crediting-God.html

    I would be curious to see what – if any – the rebuttals to the eye-boring worm would be.

    ~ Jura – who just checked his arm for devine bot flies.


    This entry was posted in Uncategorized and tagged

  • T-U-R-T-L-E Power! Part 1: Turtles are Weird.

    Posted on by Jura 11 Comments


    As the meme goes: I like turtles!

    They are such a unique group of animals, that one can’t help but be drawn to them. Yet despite their uniqueness, turtles tend to get thrown into the wastebin of “living fossils”. It’s not uncommon to hear documentaries, or books refer to turtles as having been static since their first appearance 200+ million years ago. It’s unfortunate because statements like these tend to downplay just how weird and wonderful turtles really are.

    So why are turtles so weird? Well, as one might expect, it’s all about the shell. The turtle shell is an iconic image. Everyone knows what a turtle basically looks like. Even strange turtles like the mata mata (Chelus fimbriatus) are still recognizable as turtles. Contrary to popular belief, turtles can neither come out of their shells, nor does the shell act as their home. One cannot pull a turtle from its shell. The shell is the result of a phenomenal transformation of the backbone, ribcage, sternum, clavicles and gastralia.

    Turtle shells are different from the armoured “shells” seen on dinosaurs like the ankylosaurs. It is also fundamentally different from the armour seen on armadillos, crocodylians and every other vertebrate out there. In all these other animals, the armour is composed of bony plates that are formed from bone which is made intramembranously in the dermal portions of the body. Turtles are the only animals we know of that develop their armour by using this dermal bone in conjunction with endochondral bones (i.e.. the vertebrae and rib cage).

    turtle_side_view1
    A turtle “coming out of its shell.” Image from the Encarta website.

    It is at this point that turtles go from simply being unique, to just being weird. In order for the shell to protect the exposed limbs and head, the shell had to engulf the limb girdles. The rib cage had to actually grow over the pectoral and pelvic girdles. Think about that for a minute. Take a look in the mirror sometime and see how your arms are placed. Our arms, and the arms of every other tetrapod alive today, are set outside the rib cage. In fact, we actually can (and do) rest our arms along the outside of our ribs. Turtles can’t do that. Having one’s ribs on the outside can really hamper the ability to move the arms. The arms can extend, but they cannot bend without banging into the ribs. In order to fix this, turtles had to reverse the way their arms bend. Turtle arms bend towards one another, rather than away as they do in all other tetrapods. Imagine if your arms bent like your legs do, and you get the idea. Protection of the head required another unique innovation. Namely, turtles had to become double jointed. Turtle neck articulation follows a standard “ball and socket” arrangement that is widespread among various extant reptiles. However, within each species there is between one and two vertebrae that feature a “ball” on both sides (Romer, 1956). This biconcavity creates a hinge joint that can bend a full 90°. It is this special joint, more than anything else, that allows turtles to contort their necks in such a manner. For pleurodires, as the name implies, this articulation allows the neck to be tucked to the side of the body under a lip of the carapace. For cryptodires, these double joints allow the head and neck to literally go inside the body cavity; something no other tetrapod can do, and something that is decidedly weird. 🙂 Another issue with having a shell composed of fused ribs and vertebrae, is that flexibility is reduced to zero. This has a huge effect on speed. Turtles cannot extend their stride by bending their spine; a behaviour that all other tetrapods are capable of . The only way to increase stride length is to increase the lengths of the limbs. This puts an immediate limit on turtle speed. While longer limbs could be evolved, they would not be able to fit inside the shell. The only way for a turtle to go faster is to speed up the stride frequency. Turtles were thus forced to give up on ever being speedy. Though there are some chelonian members (e.g. my Terrapene ornata luteola) which put that statement to the test.

    Yet another weird characteristic of turtles is how they have circumvented the issue of breathing while encased in armour.

    Normally, in tetrapods, breathing is achieved through the bellow like pumping of the lungs. This is accomplished by muscles connected to the ribs. These muscles expand the ribcage, allowing air to enter. As turtles no longer had the joints that allow the ribs to move, they lost the muscles that moved them. This creates a problem unique to turtles. How does one get air both in, and out of the body cavity. This is a problem that seems to have been solved multiple times in turtle evolution. Tortoises can “rock” their pectoral girdles back and forth in order to pump the lungs. Many semi-aquatic turtles can use the buoyancy of water to push air out of their lungs, while others can use the weight of their viscera to pull down on the lungs and allow air in. Many, though, have evolved sheets of muscle connected to the lungs, which will either expand, or contract the lungs and allow for respiration. Some, such as box turtles (Terrapene) require a sheets of muscle that will both expand and contract the lungs. In these animals, both inhalation and exhalation, are an energetic process. The upshot to this, is that by having independent muscles for respiration, box turtles are able to breathe even when fully sealed inside their shells (Landberg et al, 2003).

    One strange aspect of chelonians that is rarely brought up, is how incredibly diversified they are. If turtles had died out at the end of the Mesozoic, and all we had to go on were fossils, I doubt we would ever have realized just how “flexible” the turtle bodyplan actually is.

    Despite being encased in a shell both above and below, turtles are capable of chasing down prey (e.g. Trionyx and Apalone). Some are adept excavators; making extensive burrows that can run as long as 9 meters (30ft) and be 3.6m (12ft) deep (Gopherus agassizii). Still others like pancake tortoises (Malacochersis tornieri) are proficient rock climbers. Probably most surprising are musk turtles (Sternotherus). These normally waterbound turtles are quite adept tree climbers. Sternotherus minor has been observed scaling cypress trees up to 2 meters (Orenstein, 2001). Both of these species have relatively small plastrons which give them added flexibility. Still, even stiffened tanks like Leopard tortoises (Geochelone pardalis ) have been observed scaling fences that were blocking their way. The animals would climb up one side and then just topple over the other (Orenstein, 2001).


    Some, such as the big-headed turtle (Platysternon megacephalum) have evolved huge heads with strong jaws for crushing shellfish. Others are efficient filter feeders (Podocnemis unifilis); sieving the water of small food particles.

    Many freshwater turtle species have re-evolved ?gills.? These are areas of thin, permeable skin usually around their cloaca. This allows these species to take in oxygen through the water.

    Lastly, turtles don’t grow old (Congdon, 1992). Unlike most other animals, turtles show little to no signs of age related deterioration. 74 year old three toed box turtles (Terrapene carolina triunguis) were found to be just as reproductively active as turtles some 40 years younger than them. (Miller, 2001).

    So chelonians are weird, but how did they come to be this way? For that, you’ll have to stay tuned.

    ~Jura

    Extra geek points to folks who got the reference to the Partners in Kryme song from the first TMNT movie. Id est: the original turtle rap. None of that Vanilla Ice crap.

    References

    Congdon, J. 1992. Senescence in Turtles: Evidence from Three Decades of Study on the E. S. George Reserve. Senescence in Organisms in Natural Populations. American Association of Gerontologists. Washington, D.C.

    Landberg, T., Mailhot, J.D., Brainerd, E.L. 2003. Lung Ventilation During Treadmill Locomotion in a Terrestrial Turtle, Terrapene carolina. J.Exp.Biol. Vol. 206: 3391-3404.

    Miller, J.K. 2001. Escaping Senescence: Demographic Data from the Three-Toed Box Turtle (Terrapene carolina triunguis).

    Orenstein, R. 2001. Turtles, Tortoises and Terrapins: Survivors in Armor. Firefly Books. 304 pps. ISBN 1-55209-605-X

    Romer, A.S. 1956. Osteology of the Reptiles. U.Chicago Press. ISBN: 0-89464-985-x 772pps


    This entry was posted in Chelonia Uncategorized and tagged

  • Back into the groove.

    Posted on by Jura Comment

    Things have been pretty slow here over the past 2 months. Much of that had to do with things being remarkably busy IRL. I’ve also noticed that while the posting rate had dried up around here, my hit count has been steadily increasing.

    Just more proof that life lives off irony. >:)

    Anyway, now that things have slowed a tick, I’m going to be revving up the old blog once more. I should have something interesting to start the new year off later today.

    More to come.

    ~Jura


    This entry was posted in Uncategorized and tagged

  • Arctic dinosaurs special on NOVA

    Posted on by Jura 1 Comment

    Photo from Smithsonianmag.com
    Photo from Smithsonianmag.com

    Given all the recent stink over a certain other documentary, I’m not exactly itching to jump back into dino docs.

    Oh well.

    The Public Broadcasting Service’s long running series NOVA, has a new episode out, entitled Arctic Dinosaurs. The episode is about a particularly exciting find in Alaska, and its implications for our view on dinosaurs. The researchers; namely museum Victoria’s Tom Rich and MNS Dallas’ Anthony Fiorillo, came across a fossil bed along Alaska’s north slope, that revealed the existence of hadrosaurs, ceratopians and coelurosaur theropods, all living in far North Alaska.

    As I had mentioned previously, NOVA tends to get lauded for its well put together documentaries. I would argue that this doc was no different; though there were some missteps that I feel may be a sign of NOVA’s producers trying to fall more in line with the fare seen on Discovery Channel and the A&E networks.

    First, and foremost, I would like to applaud PBS for making this NOVA special available online.

    Secondly, I would like to lambast PBS for what is probably their most egregious error with this, and other NOVA specials. Namely the lack of Firefox love. The only way I am able to watch these NOVA specials is by firing up Internet Explorer. If I use Firefox all that happens is I get a dead loading screen.

    The premise of the series is fine, and as in previous iterations, NOVA has done a good job of letting the scientists talk how scientists really talk (i.e. with lots of caution and caveats).

    I was far less impressed with the writing for the narrator. There were more than a few instances where the narrator resorted to straight up hyperbole. Especially in the beginning when it is revealed that all these dinosaur fossils had been found in this polar state.

    The narrator said:

    The startling discovery that these ancient reptiles, “thunder lizards,” lived and thrived in the arctic has taken scientists by surprise.

    Then a little later:

    According to conventional wisdom, it shouldn’t be here, because this is how dinosaurs are typically pictured: cold-blooded reptiles living in tropical climes, not in cold, arctic environments like this one. And the Hadrosaur is not alone.

    Um, no. We have had discoveries of dinosaurs, and other reptiles from polar and paleo-polar latitudes, for decades now. The real neat thing about this find, was the sheer number of animals discovered. This doc served more as a review of what we have learned so far, rather than a breaking news story.

    There was another writing snafu that occurred a little further in too that I feel needs clarifying:

    Scientists long believed that dinosaur biology resembled that of cold-blooded reptiles like crocodiles, animals that require warmth to survive and cannot withstand prolonged exposure to temperatures below freezing. But not one crocodile fossil has been found along the Colville, which suggests that polar dinosaurs found a way to adapt to an environment that their cold-blooded cousins couldn’t tolerate. But how?

    This statement is misleading. We do have evidence of non-dinosaurian polar reptiles. These include Cretaceous crocodylian and turtle fossils found in Victoria, Australia (which would have been closer to the South Pole) and Axel Heiberg Island in Canada, as well as plesiosaur fossils from Antarctica, and at least the assumption that Meiolaniid turtles (large, ankylosaur like armoured turtles that lived from the late Cretaceous through to the Pleistocene) had once lived in Antarctica.

    Oh, and also Leaellynasaura amicagraphica was a herbivore; not a carnivore as was stated in the show.

    So there were those few writing missteps. The only other thing I can fault the show for was its very lackluster CG work. As NOVA is a mostly public funded series, I can forgive the lower quality CG work, though I still think they could have afforded to make their models at least a tad more realistic (especially since they teased feathers on Dromaeosaurus albertensis before returning to scaly maniraptors (i.e. the Troodon formosus). Plus their Gorgosaurus libratus was just atrocious.

    Regardless, most of these complaints are small. The writing flubs were probably the worst offenders. Short of that, the show was well put together. Though the show still fell a little more in the pro-warm-blooded camp for dino metabolism, it was the first and only time I have ever heard a documentary point out that warm-blooded and cold-blooded are opposite ends of a continuum. In fact one of the better writing moments occurred towards the end when the narrator stated:

    Dinosaurs likely had their own unique solution to the body temperature problem, which allowed them to survive for millions of years in the toughest seasonal conditions their world had to offer.

    It was nice to see a documentary that actually took a more objective stance on the whole thermophysiological debate.

    Finally another big plus for this show was the sheer number of paleontologists that rarely seem to make it in front of the camera, including Hans-Dieter Sues and Anusuya Chinsamy-Turan (the latter of whom while being a great scientist, has one of the harder to pronounce names in paleontology).

    Overall, this was another fine piece of work from the folks over at NOVA. Though there was a tendency to stray into the realm of hyperbole with the narration, and the CG work is somewhat painful to watch, the show proved informative and interesting.

    In the end, that’s really all a documentary should strive for.

    ~Jura


    This entry was posted in Dinosaurs Uncategorized and tagged

  • The return of fruit eating crocodylians.

    Posted on by Jura Comment

    Back in 2002, a short paper came out that commented on the observation that captive caimans would eat fruit left in their cage. When I initially read the paper, I found it interesting. In the end, though, I assumed this to just be a fairly anomalous incident.

    Now Darren Naish of Tet Zoo has followed up on this story with further evidence of frugivory in crocodylians.

    As one can see, this observation has been filmed at least once.

    So does this mean that crocodylians are not as completely carnivorous as once thought? It’s hard to say. All observations made so far have been from alligatorids (alligators and caimans). This might be an apomorphic trait to this group. Only more observations will say for sure.

    Another option that Darren pointed out, is that this was a learned trait of these captive animals. In each case, observed animals were found to be sharing their enclosures with herbivorous animals (usually tortoises). This type of operant learning is rather rare, and would be amazing if found to be true.

    However, as evidenced by the comments of St. Augustine Alligator Farm park director, John Brueggen, fruit eating has been observed in wild animals too; so this is not simply a case of bored captives.

    Whatever the case, these observations do illustrate just how adaptaptable crocodylians are as a group.

    ~Jura


    This entry was posted in Crocodylia Uncategorized and tagged

  • WordPress automatic upgrade.

    Posted on by Jura Comment

    While having the ability to manually mess around with any aspect of the blog is a cool feature, one downside to having the manual version of WordPress is that upgrading becomes a bit of a chore. Usually by the time I get around to upgrading, there is a new version of WordPress available by the time I am done.

    So I deal with the frustrating nag in the admin page, urging me to upgrade.

    Well, I need not worry about this anymore. Jeff Bakalar of CNET has given a thorough video tutorial of a neat WordPress plugin called WordPress automatic upgrade.



    The plugin goes through all the tedious steps required to upgrade to the latest version of WordPress. While there are a lot of task screens that must be clicked through, the whole process still goes by substantially faster than before. If you have the manual version of WordPress, I highly recommended WordPress automatic upgrade.

    No more tedium, and no more nags.

    ~Jura


    This entry was posted in Uncategorized and tagged