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Part seven of an ongoing series about all things dinosaurian!

Past diaries can be found here--

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Pronounced 'Ni-jhir-sor-ihs'

Or if Nee-jher if you prefer the French version instead!

Nigersaurus was an absolutely fascinating and downright strange sauropod dinosaur that lived in the Middle Cretaceous period (119-99 million years ago) in what is now modern day Niger, but was then the southern super continent of Gondwana (consisting of what we now know as Africa, South America, Australia, New Zealand, India, and several Arabic countries).

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Though it was first discovered in 1979, the true extent of the oddities characteristic of this dinosaur was not known until 2005 when paleontologist Paul Sereno lead an expedition into the Nigerian deserts to delve into the history of evolution on this ancient continent (one of my goals within my career is to study some of these creatures--partly because of the locality and partly because so monumentally little is known about the Gondwanan dinosaurs relative to those of more northern latitudes).

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In the expedition, they had unearthed an extraordinarily fragile skull along with several vertebrae and other assorted bones of this dinosaur.

Though because bone material in the field is frequently caked with excess dirt and rock (which we paleontologists call 'matrix'), much of what they learned about the biomechanical functionality of this skull would be found after the field season when it was cleaned and prepared in the lab.

First of all, it took bone pneumacity (in which the bone is full of holes to lighten the weights that the animal would otherwise have to bear) to a fantastic new level: for the most part, its skull and vertebrae were mostly patches of air with some bone as an afterthought!

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Its skull certainly followed the same pattern, containing five extra fenestra ('holes') on each side.

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In fact, one bone in particular (the jugal, or cheek bone) was so thin that light could shine straight through it, demonstrated here--

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But the feature that has received the most attention were its jaws--like all dinosaurs, Nigersaurus had a constant supply of teeth to replace the others as they become worn via chewing the tough Cretaceous plant matter (lots of ferns and cycads). However, as with only two groups of dinosaurs known (hadrosaurs, or 'duckbills' and the ceratopsians such as the well known Triceratops), it held a constant tooth battery.

In this battery, it contained 50 columns of teeth that would be worn and replaced at a constant rate, allowing it to chew the plant matter like a prehistoric lawn mower.

CT scanning determined that at any given time, Nigersaurus had as many as 500-600 teeth in its skull.

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The same CT scan taken also determined that due to the positioning of the semi-circular canals in the ear cavity, Nigersaurus spent most of its time (both in a feeding position and walking position) with its skull pointed almost completely downwards. This implies that unlike what is thought for most other sauropod dinosaurs, it fed mostly on ground matter as opposed to the more aerial trees.

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The initial 2005 paper describing the tooth battery can be found here--

http://www-personal.umich.edu/...

And a more detailed description here--

http://www.plosone.org/...

Both require some level of specialist vocabulary, but thought I'd link them all the same!

Hope you enjoyed it, and feel free to rec away.

Originally posted to Username4242 on Wed Jul 01, 2009 at 11:39 AM PDT.

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Comment Preferences

  •  Interesting to see a sauropod have (10+ / 0-)

    bone pneumacity and yet feed mostly on ground matter.  It would seem to me that having lighter bones would be beneficial to poking your long neck and head around trees in order to get at vegetation up high instead of vegetation on the ground.    

    The question to everyone's answer is usually asked from within. -Steve Miller

    by jtb583 on Wed Jul 01, 2009 at 11:52:17 AM PDT

  •  That's a lotta teeth. (6+ / 0-)

    The bone pneumacity fascinates me. I wonder what they sounded like with those hollowed cheeks, etc.

    "If they can get you asking the wrong questions, they don't have to worry about answers." - Thomas Pynchon, "Gravity's Rainbow"

    by Uwaine on Wed Jul 01, 2009 at 12:02:53 PM PDT

    •  Knowing how evolution works (5+ / 0-)

      It may be that the pneumacity was a carry over from its evolutionary ancestors, and not something that was essential to its own success.

      Or perhaps pneumacity was not a result of needing lighter bones, or possibly the consequences of a mineral scarcity?  

      I'm looking a bit at human nutrition and one of the more interesting things I'm finding is that our bodies are geared to absorb certain minerals, but don't have specialized metabolic mechanisms for ridding ourselves of excess minerals.  This implies that a scarcity of these minerals is much more common than an excess.

      So the idea that certain dinosaurs evolved to deal with a mineral scarcity by having heavier weight bearing bones and lighter bones elsewhere doesn't seem to far fetched to me.

      Proud member of the Cult of Issues and Substance!

      by Fabian on Wed Jul 01, 2009 at 12:21:21 PM PDT

      [ Parent ]

      •  Semi-aquatic? (2+ / 0-)
        Recommended by:
        Uwaine, blackjackal

        Might a semi-aquatic (i.e., shallow water) habitat account for these characteristics?  Pneumacity would certainly make the creature lighter and thus (one would presume) more buoyant for it's body volume.  A wading grazer might retain such a trait as an adaptive advantage, even if it evolved for other reasons.  At the same time, feeding on bottom vegetation would certainly require a head-down feeding style.

        So the obvious next question I'd have is, what was the environment in that region during the Middle Cretaceous?  Or am I barking up an entirely wrong tree here?

        Conservito delenda est pro is deleo orbis terrarum!

        by Stwriley on Wed Jul 01, 2009 at 12:34:18 PM PDT

        [ Parent ]

        •  The main issue is wear within the teeth! (3+ / 0-)
          Recommended by:
          Stwriley, Uwaine, blackjackal

          Aquatic feeders (hippo, etc.) primarily feed on very soft, gentle vegetation--which in turn is very easy on the teeth, which produces very little wear.

          However, what we see with Nigersaurus (and indeed most herbivorous dinosaurs) is that the teeth not only see wear, but a tremendous amount of it--the analysis Sereno did on the skull suggests that each row of teeth was replaced in the line of once a month due to the material of the plant matter.

          •  Hippos? (1+ / 0-)
            Recommended by:
            Uwaine

            But hippos are land grazers, feeding on grass, not aquatic plants.  I'm rather dubious at the idea that we can characterize all aquatic growth as "soft" or "gentle" either, especially if we're talking about the Middle Cretaceous.  I'm not saying I'm right on this (far from it) but I'm not sure these are necessarily correct counter-arguments.

            That was why I asked the environment question.  Knowing what the surrounding habitat was like and what grew there would be necessary for either following or dismissing this idea (at least for me.)  I don't think the apparent rapid tooth replacement means that what I've proposed is impossible.

            Conservito delenda est pro is deleo orbis terrarum!

            by Stwriley on Wed Jul 01, 2009 at 01:12:14 PM PDT

            [ Parent ]

            •  Yeah, sorry; didn't got much sleep last night. (3+ / 0-)
              Recommended by:
              Fabian, Stwriley, Uwaine

              Hippos were certainly not a good example.

              Reading through the paper, most of the Nigersaurus fossils have been found in deposits that are non-indicative of still water habitats (like a lake), but more river systems and flood plains.

              It suggests that due to the range of motion of the neck, and to the wear of the teeth along with jaw morphology (plus ecological plant life reconstruction) its most likely food source would have consisted of ground level ferns and horsetails.

              Didn't really think before I posted, sorry again!

              •  Horsetails! (2+ / 0-)
                Recommended by:
                Stwriley, Uwaine

                Current horsetails are so high in silica that settlers used them to scour out pots and pans.  Imagine eating them!  That would certainly wear out your teeth.  Of course, I have to wonder if their teeth were the same as ours.  If we grew new teeth all the time, would ours be nearly so durable?

                Proud member of the Cult of Issues and Substance!

                by Fabian on Wed Jul 01, 2009 at 04:06:07 PM PDT

                [ Parent ]

      •  I hadn't thought about mineral scarcity. That's (2+ / 0-)
        Recommended by:
        Fabian, blackjackal

        an interesting hypothesis. I just figured it needed all the calcium for teeth production :D.

        "If they can get you asking the wrong questions, they don't have to worry about answers." - Thomas Pynchon, "Gravity's Rainbow"

        by Uwaine on Wed Jul 01, 2009 at 12:39:06 PM PDT

        [ Parent ]

        •  I don't know a whole lot (1+ / 0-)
          Recommended by:
          Uwaine

          about dinosaurs, but it's certainly fun imagining what they must have been like and how they dealt with the challenges all animals need to - finding food, water, raising young, defending against predators.  

          The mass extinctions must have wiped out a fair amount of genetic diversity, like the pneumacitic skeletons and the renewable dentition.  

          Proud member of the Cult of Issues and Substance!

          by Fabian on Wed Jul 01, 2009 at 04:02:18 PM PDT

          [ Parent ]

  •  OMG (11+ / 0-)

    I seriously had no idea this was a diary on actual Dinosaurs.

    I was so going to bomb Nigersaurus with LOLCats based on my first assumption.

    Wow.

    Good think I looked before I leapt.

    Cheers

    The object of persecution is persecution. The object of torture is torture. The object of power is power. Now do you begin to understand me?' - 1984

    by MinistryOfTruth on Wed Jul 01, 2009 at 12:08:39 PM PDT

  •  A walking vacuum cleaner (5+ / 0-)

    Imagine trying to carry that door to door, poor salesmen!

    •  It seems a most efficient lawn mower (3+ / 0-)
      Recommended by:
      Hedwig, Stwriley, blackjackal

      Quite the specialist too!

      For some reason, I immediately thought of a mixed herd of nigersaurus and some taller dinosaurs.  The nigersauri would eat ground level plants and anything that fell from the tall browsers and also use the larger dinosaurs for protection from predators.

      Proud member of the Cult of Issues and Substance!

      by Fabian on Wed Jul 01, 2009 at 12:25:12 PM PDT

      [ Parent ]

  •  Hey thanks! (1+ / 0-)
    Recommended by:
    jtb583

    I love your dinosaur diaries.

  •  What About Defensive Issues? (2+ / 0-)
    Recommended by:
    Fabian, Uwaine

    Wouldn't the bone pneumacity make for a rather fragile skeleton?  Your description makes them sound almost like ultra-large four-legged birds, which exhibit the same sort of bone hollowing you describe.  Birds can be very strong, but they can also be pretty fragile, especially when impacted by something hard.  A dinosaur like nigersaurus would need to avoid almost any sort of encounter with a predator or otherwise it would toast (and lunch too).  Of course, lighter bones could imply that it was pretty nimble, kind of like a horse or ass, to avoid predators.

    "Love the Truth, defend the Truth, speak the Truth, and hear the Truth" - Jan Hus, d.1415 CE

    by PrahaPartizan on Wed Jul 01, 2009 at 01:57:35 PM PDT

    •  Sauropod defense! (2+ / 0-)
      Recommended by:
      Fabian, Uwaine

      Though there are very few skeletons of Nigersaurus and so far as I know, no trackways; it is known that many groups of sauropods utilized herding behavior to hold keep predators at bay.

      And though Nigersaurus is fairly small so far as sauropods go, size can also be a fantastic advantage--I'd imagine that if a predator were to approach Nigersaurus, it would try to make itself appear as large as possible--stomping its feet on the ground and making lots of noise.

      Another neat possibility for defense lies within the diplodocid (the clade of sauropods that Nigersaurus is a  part of) tail design--though I'm not sure if the bone ratios are exactly enough in Nigersaurus, computer modeling comparing the tail of Diplodocus to the size and shape of a whip shows that its tip was capable of breaking the sound barrier (exactly like one does with a whip to make the characteristic crack).

      So you can picture a group of diplodocus creating loud booming noises with their tails to add to the intimidation factor.

      But yeah, their skeleton was very lightweight and would certainly be more easily chewed through than if it were dense material.

  •  Very cool (1+ / 0-)
    Recommended by:
    Fabian

    Could you define what makes a dinosaur a dinosaur? I've vague ideas of dentition, skeletal structure, perhaps breathing mechanism, but if you were to show me a fossilized reptilian skeleton I wouldn't know how to classify it (unless it was really obvious and had a huge neck shield and three horns on its head or something).

    •  Absolutely. (2+ / 0-)
      Recommended by:
      Fabian, Uwaine

      Using an informal description (ie, without using cladistics), dinosaurs are two-legged land-dwelling archosaurs (group that includes crocodiles, birds, etc.) dominant within the Mesozoic period that held their legs (either two or four) in an upright non-sprawling posture.

      They either exhibited saurischian hips (lizard like) or ornithischian hips (bird-like). In the saurischian hip design (used by large theropod dinosaurs among others), the pubic bone is very separate from the ischium bone in the hip.

      Photobucket

      While in the in the ornithischian hip design (utilized by animals like Triceratops, hadrosaurs, Pachycephalosaurs, etc.), the pubic bone bends backwards like they do in modern day birds (which can be confusing because birds in fact evolved from saurischian dinosaurs).

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      They also exhibited growth rates and apparent metabolisms that were non-characteristic of cold blooded animals.

      Using the cladistics, one would have to add all birds that survived past the KT boundary extinction (when the dinosaurs were mostly killed off!) 65 million years ago.

      So all the birds you see are walking modern day dinosaurs!

  •  omg, it's so cute!! /nt (1+ / 0-)
    Recommended by:
    Username4242

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