• Category Archives Uncategorized
  • “Dakota” and National Geographic

    This upcoming Sunday (9th December), National Geographic is going to be airing a special devoted to the dinosaurs (and other interesting critters) of the Junggar basin. The overall information conveyed should be interesting. The less than stellar CG models should not. Seriously, in the land of dino docs, National Geographic has got to have the smallest budget. Whatever though, it’s a documentary. The actual look shouldn’t matter all that much.

    That said, be prepared to hear a lot of nonsensical roaring. Oh, and seeing Guanlong with an idiotic mane.


    The second part of the special deals with a finding here in the states. A hadrosaur by the name of: Dakota. The species has yet to be worked out, but that’s not so important as the fossil itself. Dakota represents the most complete dinosaur ever.

    Think about that…ever.

    See Dakota is a mummy. Not the Egyptian kind (obviously), but the same basic premise. Basically this hadrosaur wound up getting buried in anoxic material faster than any bacteria had a chance to degrade it. Not only does Dakota preserve skin (which many other hadrosaur mummies have done), but it also preserved muscle tissue, and tendons. Who knows, there might even be some viscera in there.

    Everything is still pretty hush hush until after the NG special. All that’s really been released so far is that the evidence from the mummy shows that dinosaurs were much longer than previously thought, and that Dakota had a far more muscular hind end than anyone imagined. This extra muscle has been (speculatively) translated into faster running speed for hadrosaurs. The current media blitz has everyone believing that hadrosaurs could outrun Tyrannosaurus rex. To be honest, that is taking the speculation a bit too far. This data is interesting for what it tells us about hadrosaurs. It doesn’t really say much about T.rex.

    That said, I don’t really see a problem with the thought of hadrosaurs being faster. Despite what all the T.rex fanboys would have the world believe, T.rex was just another predator. Like most predators it probably had a kill ratio that was pathetically low (i.e. it lost most of what it hunted). There’s nothing wrong with that. Hadrosaurs evolved with tyrannosaurs throughout their geological history. If tyrannosaurs were so good that they “got one” every time, then it wouldn’t seem very likely that hadrosaurs would have lasted as long as they did.

    Plus, there were a whole lot of hadrosaurs back then.

    Anyway, this is my heads up for folks who don’t know. The air date is December 9th at 9 EST (8 C/P). That’s all American time. For the rest of the world, feel free to adjust GMT to your respective times.

    For more on the whole show, check out NG’s official site for it:

    Dino Death Trap


  • Intelligent Design on trial

    Science vs Religion Simpsons style
    As for science versus religion, I?m issuing a restraining order: Religion must stay 500 yards from science at all times.


    This is yet another case of me coming to the party a bit late. I can’t even blame my connection quandaries anymore, as I am now up and running 24/7. I guess I haven’t yet got the hang of this whole “blog” thing. Anyway, on Tuesday (13th Nov) NOVA aired their special on the infamous Dover case. They went over the causes that lead up to it, as well as what was at stake.Though I missed the chance to let folks know about this ahead of time, I can let you guys know that PBS has made the entire show available online.

    Just head to:

    http://www.pbs.org/wgbh/nova/id/program.html.

    The special is two hours long, and broken up into 12 chapters. Apparently the ID folks were not happy with the treatment that NOVA was going to give the special (i.e. an objective one), so few proponents agreed to be interviewed. That stance certainly isn’t going to do anything helpful for their cause.

    So if you are curious about the whole debate, or are active in it, check out the program. It’s worth watching.


  • Paleo-ecological snapshot

    Who ate who. From NationalGeographic.com


    Rare is the event when the fossil record records a case of animal behaviour. More often than not, this is recorded as footprints. Every once in a while though, we get lucky and find a case of actual animals doing what they were doing prior to death.The most famous case of this is the fighting dinosaurs of Mongolia. This is the fossil featuring a Protoceratops andrewsi attacking and being attacked by a Velociraptor mongoliensis. This was easily the best fossil of this type that scientists had ever found. That is until now.

    First Food Chain Fossil.
    Paleontologists at the Berlin museum of natural history have unearthed the remains of a a fossil “shark” that ate an “amphibian” that ate a fish.

    The reason for all the quotation marks is due to the fact that all three of these critters represent animals that no longer exist, and were not true members of Selachimorpha (sharks), Amphibia, or osteichthys. The “shark” that was found, was a xenacanthid. This makes it a cartilaginous fish (Chondrychthys), but it’s no more a shark than it is a skate, or a ray. The other animal (well animals, since there were two that were eaten) were temnospondyls. Temnospondyls were a highly successful group of critters that hold the distinction of being one of the first land dwelling tetrapods (think: Eryops). Whether, or not they can be considered amphibians, seems to depend on how far back in time one is willing to call critters amphibians. In the very simplified evolutionary view of life (i.e. classic cartoon version), then yes, any animal between a fish and a reptile is going to be an amphibian. In the more complicated, bushy version of evolution (i.e. what actually happened) calling temnospondyls amphibians gets kind of weird. For instance, temnospondyls apparently had dermal scales, much like fish. Scales are nonexistent in extant amphibians (save caecililans, so maybe this isn’t so weird), so calling temnospondyls amphibians doesn’t really sit well with me. Then again, if I were a science journalist, I’d have to figure out how to explain temnospondyls to a lay public, and to do it with a finite amount of space.
    But I digress…

    Along with the two temnospondyls in the stomach of the xenacanthid “shark,” we also have a “fish” inside one of the temnospondyls. Okay, so “fish” has been a wastebin term for some time now. As such, one could technically say that it is okay to call the animal inside the temnospondyl, a fish. I’d just point out that the fish that was eaten, was an acanthodian. These were an interesting, but enigmatic group of earlly fish that broke off from the line that lead to the osteichthyans. They weren’t cartilaginous fish, but they didn’t give rise to anything alive today either.

    The reason this fossil rocks (no pun intended) is because it shows one animal eating another animal, and then getting eaten by yet another animal. It reminds me of an old Looney Tunes cartoon. This tri-level trophic event is rare to see in living creatures, so one can imagine the chances for a one in a million fossil. Making matters even more interesting, this tri-level trophci event involves groups of animals that aren’t alive today. It’s a true snapshot of a bygone time.
    Completely awesome find.
    For those looking to read more about it, I’ve included the abstract to the official paper:

    Kriwet, J., Witzmann, F., Klug, S., Heidtke, H.J. 2007. First direct evidence of a vertebrate three-level trophic chain in the fossil record. Proc. Royal Soc. B. Early published online. doi: 10.1098/rspb.2007.1170

    Abstract

    We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level food chain in the fossil record with the simultaneous preservation of three trophic levels. Our analysis shows that small-sized Lower Permian xenacanthid sharks of the genus Triodus preyed on larval piscivorous amphibians. The recorded trophic interaction can be explained by the adaptation of certain xenacanthids to fully freshwater environments and the fact that in these same environments, large temnospondyls occupied the niche of modern crocodiles. This unique faunal association has not been documented after the Permian and Triassic. Therefore, this Palaeozoic three-level food chain provides strong and independent support for changes in aquatic trophic chain structures through time.


  • Crocodile tears are real. Who knew?

    _Crocodylus niloticus_ eating an impala. Do you see tears?

    We’ve all heard the old wives tale about crocodiles crying during feeding. Many of us have probably also run across numerous references that discount this statement. That said, there has never been much scientific interest in determining whether, or not crocodiles actually cry.That has just changed:

    Shaner, D.M., and Vliet, K.A. 2007. Crocodile Tears: And thei eten hem wepynge. Bioscience. Vol. 57. No. 7: 615-617. doi: 10.1641/B570711

    The subtitle there translates to: “And they eat them weeping.”

    The aforementioned authours were studying an apparent phenomenon in humans called: parareflexes. The hypothesis for this goes that a screwup in our normal genetic makeup, may result in the expression of traits/behaviours from an older phylogenetic time. Interestingly, the hypothesis came about from the supposed phenomenon of crocodile tears. In this case, the hypothesis is assuming that the trait of crying while eating, is one that was found in the last common ancestor between humans and crocodiles (over 300 mya). Er, yeah.

    Coming back to the story, the authours tested Alligatorids (2 caiman species and the American alligator) from the St. Augustine Alligator Farm in St. Augustine Florida, USA (highly recommended for folks who like crocs). The animals were trained to walk up on the bank, out of the water, and accept food from there. All the animals were dry when they came up to eat.

    The results showed that crocodylians do cry while eating. At least, they seem to when eating away from water (rather hard to tell if they are crying while in the water). They also show a large amount of bubbling around their eyes. Stranger still, the eyes cry at different rates (i.e. one eye has more bubbles and water than the other).

    So what does it all mean?

    That, the authours didn’t delve too much into. They mentioned that the phenomenon they witnessed was different from the one mentioned on Adam Britton’s site. The authours suggest that this might be a byproduct of crocodylian anatomy. Due to the extensive sinuses found in crocodylian skulls (see: here), there is a connection between the nasolachrymal duct (the nose/tear ducts) and the nasopharynx (where the internal nostrils meet the throat). The authours speculate that during bouts that involve pushing air back and forth through this duct (e.g. feeding, or extensive fighting), the lachrymal glands are stimulated to release tears. This would also explain why there was bubbling found in nearly all the animals studied.

    So crocodylians cry; but they still don’t seem to do it out of remorse. I guess this makes the old wives tale only partially true.

    ~Jura


  • Biomechanics of theropod necks

    _Ceratosaurus_ skeleton from the NMNH website

    Yes, yet another entry involving dinosaurs. Given their popularity, you’d think that I’d have a better write up of them on my site. >:)

    It will happen one day. Until then, there are plenty of great places on the web to learn about dinosaurs.

    That said, let’s tackle the meat of the matter.

    Snively, E. and Russell, A.P. 2007. Functional Variation of Neck Muscles and Their Relation to Feeding Style in Tyrannosauridae and Other Large Theropod Dinosaurs. The Anatomical Record. Vol. 290: 934-957.

    This paper is just an awesome testament to just how much we can learn about animals by studying their skeletons alone.

    The authors studied the cervical (neck) vertebrae and skulls of 15 theropod dinosaurs from 3 major clades.

    The family: Tyrannosauridae

    • Daspletosaurus
    • Albertosaurus
    • Gorgosaurus
    • Tarbosaurus
    • Tyrannosaurus (Nanotyrannus as well, but it was placed as a probable junior synonym of Tyrannosaurus).

    Carnosauria

    • Allosaurus
    • Sinraptor
    • Monolophosaurus

    Neoceratosauria

    • Ceratosaurus

    Abelisauridae

    • Carnotaurus
    • Abelisaurus
    • Majungatholus

    It should be noted that, where possible, multiple species within a genus were used.

    _Allosaurus_ skull from UCMP Berkeley's site

    The authors studied the muscle scars left on the cervical vertebrae and rear skulls of every specimen. By carefully studying the location of each scar, and comparing it to the Extant Phylogenetic Bracket (EPB) – which would be birds and crocodylians – it was possible for them to determine which scar belong to which neck muscle.

    Neater still; the size of a muscle scar, at its origin, is proportional to the cross sectional area of that very muscle (at least when comparing homologous muscles).

    What does it all mean? Basically, the authors were able to deduce (with reasonable accuracy) the overall size of the muscles found in these theropod’s necks, just by measuring the size of the muscle scars left on the cervical vertebrae themselves.

    Now how cool is that?

    The end results featured 3 representative species:

    1. Tyrannosaurus rex
    2. Allosaurus fragilis
    3. Ceratosaurus nasicornis

    Each one was a “poster child” for a particular feeding method.

    _T.rex_ skull from Biocrawler dinosaur encyclopedia

    Tyrannosaurs (especially Tyrannosaurus) employed a puncture and pull method that required strong muscles for pulling the neck up and sideways (somewhat similar to the feeding method used by crocodiles when on land).

    Neoceratosaurs showed strong ventral musculature suggesting strong downward force was being used. They also show strong dorsal and lateral musculature, which suggests that they employed a “hit and run” method of attack that would be similar to white pointer sharks, or Komodo dragons.

    Last, but certainly not least, Allosaurus and its ilk were more similar to the speedy dromaeosaurs (Deinonychus, Velociraptor) in hunting style. Strong ventral musculature helps to corroborate previous studies (such as Emily Rayfield’s FEA study) that Allosaurus used its head like a hatchet, and slammed it down into prey animals. The long, strong forearms were probably used first to hold prey and brace it for the killing strike.

    All in all, this was a fascinating paper. One with the potential to change all future reconstructions of these animals.

    So keep your eyes tuned to Discovery Channel, as I’m sure they are bound to make a special that will incorporate this data (they always do).

    ~Jura


  • Of the Birds, the Bees and the Dinosaurs.

    This is actually a re-write of a previous blog post that got lost in the void of cyberspace when I clicked the “save” button.

    Needless to say, I’m not feeling as driven to write everything all over again. As such, I’m just going to touch on the highlights.

    I’ve been in internet connection hell for the past 2 weeks, so I’m a bit behind on the reptile news. This latest one comes from about a week ago.

    Study finds that dinosaurs had sex as youths.

    A study by Gregory Erickson and colleagues has found that dinosaurs did not wait until they were fully grown up, before engaging in sex.

    Though the finding is touted as a surprise, the reality is far from that. The scientists in question studied the bone microstructure of 7 theropods that were found near eggs (therefore, expected to be the parents of said eggs). These theropods were also of close relation to birds (clades: Oviraptorosauria and Deinonychosauria). What they found was that a members of each clade showed signs that they were still growing while watching their eggs.

    In the grand scheme of things, this is not surprising. Sexual maturity hits reptiles, mammals, fish and amphibians before full body size is achieved. It is often represented as a time when maximal growth rate ends (as resources get diverted to egg/sperm production).

    The only exceptions to this rule are Avians. Birds reach full adult size extremely fast (1 year, or less for most species). Sexual maturity trails way behind at 2-4 years in many of the larger animals. The reasoning behind this is due to the mechanical limitations of flight in birds. The musculature required to sustain flight, is not available in birds until they reach adult size. As flight is the main means of escape from predators, it behooves birds to reach flight status as quick as possible.

    Well, needless to say, few dinosaurs flew (Microraptor gui being the only example I can think of), so the pressure to hit adult size was just not there for dinosaurs.

    In the end this report can be filed under: Assumed and Now Validated.

    This finding, along with many other findings over the past couple of years just helps to remind us that birds evolved from dinosaurs; not the other way around.

    ———————————————————–

    Reference

    Erickson, G.M., Curry Rogers, K., Varricchio, D.J., Norell, M.A., Xu, X. 2007. Growth Patterns in Brooding Dinosaurs Reveals the Timing of Sexual Maturity in Non-Avian Dinosaurs and Genesis of the Avian Condition. Biology Letters Published Online. doi: 10.1098/rsbl.2007.0254


  • The fibrolamellar smoking gun.

     

    Three different types of bone growth scene in vertebrates. A. Low vascular, lamellar bone. B, highly vascular, woven bone. C. Fibrolamellar bone. Arrows indicate Lines of Arrested Growth (LAGs). Image from http://ltc.smm.org/histology/
    Three different types of bone growth seen in vertebrates. A. Low vascular, lamellar bone. B, highly vascular, woven bone. C. Fibrolamellar bone. Arrows indicate Lines of Arrested Growth (LAGs). Image from http://ltc.smm.org/histology/

     

    For over twenty years now it has been assumed that there is a black and white divide between bone histology and thermophysiology. Automatic endothermic “warm blooded” animals tend to show a haphazard composition of bone deposition, in which bone is laid down around surrounding blood vessels very quickly, with interspersals of more organized bone deposition (for strength). The term, coined by histologist Armand de Ricqles (1980), is fibrolamellar bone.

    In contrast, bradymetabolic “cold-blooded” animals tend to show a regular deposition of layered, or lamellar zonal bone. This bone is not as well vascularized as fibrolamellar bone, and is often deposited at a much slower rate.

    Back in 1980, this evidence was used along with a chain of other circumstantial evidence to show that dinosaurs were actually “warm-blooded” animals (Bakker, 1980). This challenge did not go unanswered, and even back then there were people questioning the evidence being proposed in favour of dinosaurian automatic endothermy. As far back as 1982, there were authours claiming to have histological evidence of fibrolamellar, “warm-blooded” bone growth in crocodylians (Ferguson et al, 1982). This evidence has often been scoffed at as being questionable at best (Horner & Padian, 2004). Skeptics have pointed out that the fibrolamellar crocodylians mentioned have all been captives. Being kept in a stable environment with easy access to food has resulted in these skewed results. Wild individuals would doubtfully show these traits, as access to scenarios like those provided in captivity, are unlikely.

    For awhile this seemed to keep the argument of fibrolamellar bone, strictly in the pro-automatic endotherm camp. Well, not anymore.

    Tumarkin-Deratzian, A.R. 2007. Fibrolamellar bone in adult Alligator mississippiensis. Journal of Herpetology. Vol. 41. No.2:341-345.

    This paper reports the observation of long bone histology in alligators from Lake Griffin in Lake County, Florida. The findings are most interesting. Seven specimens were studied. Of these, three had extensive fibrolamellar growth in their long bones. In fact, one could put a fibrolamellar individual next to a lamellar zone individual and it would look like one was comparing a “classic mammal” to a “classic reptile.” The difference is incredibly dramatic; even moreso than comparing frame A with frame C in the above picture.
    That’s not the best part though. You see, these lake Griffin alligators were not only wild animals, but they were stressed animals too. Currently the Lake Griffin alligator population is suffering from an intense die off. The reasons behind the high mortality at Lake Griffin remain uncertain, but there seems to be a link to thiamine deficiency in the animals dying.

    This means that, not only are we seeing different bone deposition patterns in animals from the same population, but we are also seeing them from animals that were living under stressed conditions. This throws the whole “crocodylians can only show automatic endothermic growth rates under perfect conditions” argument right out the window.

    So what does fibrolamellar deposition really show? Currently it remains unknown. It might still indicate faster growth. What it doesn’t indicate, though, is the thermophysiological preference of the animal in question.

    Id est: it doesn’t seperate the “warm-bloods” from the “cold-bloods.”

    More to come. Stay tuned.

    ~Jura

    References
    Bakker, R. 1980. “The Need for Endothermic Archosaurs.” In: Thomas, R. D. K., and Olson, F. C. (eds.). A Cold Look at the Warm-Blooded Dinosaurs. Westview Press, Boulder.
    de Ricqles, A. J. 1980. “Tissue structures of dinosaur bone: Functional significance and possible relation to dinosaur physiology.” In: Thomas, R. D. K., and Olson, F. C. (eds.). A Cold Look at the Warm-Blooded Dinosaurs. Westview Press, Boulder. Pp. 103-139.
    Ferguson, M.W.J., Honig, L.S., Bingas Jr, P., Slavkin, H.C. 1982. In vivo and in vitro development of first branchial arch derivatives in Alligator mississippiensis. Progress in Clinical nad Biological Research. Vol. 101: 275-286.
    Padian, K. and Horner, J.R. 2004. “Dinosaur Physiology.” In: Weishampel, D.B., Dodson, P. and Osmolska, H. (eds.), The Dinosauria 2nd edition. Univ. California Press., Berkeley. pp. 660-671.

  • When dinos were nixed, mammals stayed fixed.

    According to news from CNN.com, (though technically, AP), mammals weren’t itching to take over the newly vacated niches left behind by the dinosaurs 65 mya.

    A new phylogenetic study of mammals, reported that there was no burst of activity following the demise of the dinosaurs. There was some flurry of speciation in animals that left no descendants, but all extant mammals remained pretty low key until around 55-35 mya.

    As is typical for these studies, the results are somewhat controversial. Some folks are questioning the dating methods used, while others are both shocked and impressed with the results.

    Though the AP sticks in the hyperbolic: “…challenges a long-standing theory.” statement, I doubt we’ll be seeing textbooks getting rewritten anytime soon.

    ~Jura


  • Latest Paleo News

    Apparently these past couple of days have been a bit of a boon to paleontology. 3 new finds have just been announced.

    The most recent find, is that of a new species of gliding reptile from the early Cretaceous period (125 mya).

    See: New Scientist for a full description.

    The neat thing about this critter is that it is the oldest gliding lizard to date. Back in the Permian and Triassic periods, there were various gliding critters like Sharovipteryx, Coelurosauravus, and Kuehneosaurus. None of these reptiles were lizards, though.

    This new guy, Xianglong zhaoi, is the first true member of squamata that glided. The New Scientist illustration makes the critter look nearly exactly like a modern day Draco. I haven’t read the paper yet, so I’m not sure how accurate it is. Finally, another neat thing about this little guy (only 15 cm long) is that it was preserved so well that one can actually make out the wing membrane itself. Very cool stuff.

    The second bit of news is among the crocodyliformes. A new species of Metriorhynchid suchian has been unearthed in Eastern Oregon. Metriorhynchids were a completely marine group of crocodyliformes. They are easily diagnosed by their thin snouts with needle like teeth, their lack of any real scalation (in specimens that retain skin impressions) and the presence of a bifurcated, or forked tail. Imagine something like the horrible love child of a crocodile and a shark.

    Full story here

    According to the report, this new guy, who has yet to be named, lived around the middle to late Jurassic (180-150 mya). According to the report, this species retained short stubby limbs (all other Metriorhynchids evolved paddles), which suggests that it might have still made forays onto land. It was probably a coastal dweller. It must have been pretty clumsy on land, though, given its large forked tail.

    The last bit of news is in the realm of dinosaurs. Paleontologists have recently announced the discovery of an ornithischian dinosaur that was a burrower. The new dino, named: Oryctodromeus cubicularis, was found inside an ancient burrow. It also showed a couple of unique features that suggest this animal did the burrowing itself.

    One can read more on the story here.

    The paper will appear in the next issue of: Proceedings of the Royal Society B.

    Once I get ahold of these papers, I may make an update.

    Stay tuned.

    ~Jura


  • American crocodile bounces back.

    A little over 30 years from when it was originally put on the endangered species list, the American crocodile (Crocodylus acutus), has been officially moved from “endangered” to “threatened.”

    American crocodile pick from: stockpix.com

    Crocodylus acutus

    Though the animal remains endangered in South America, in the states things seem rosier.
    In Florida the animals have gone from a scant 300 wild animals, to 2,000. Though this pales in comparison to the amazing comback that the American alligator (Alligator mississippiensis) made (over 1 million individuals live in the Southern U.S.), it is still an impressive bounceback.

    Kudos to the American croc and the conservationists who worked tirelessly to bring it back from the brink.