Tuesday, 24 December 2013

Influence of the rostrum linkage system on forage volume in Brontorusps (Brontocrambis brucus)


A Christmas Special!
Ahead of the normal schedule, and with dinosaurs, rusps and biomechanics!

Click to enlarge; copyright Gert van Dijk
The title of this post sounds like that of a proper scientific paper, doesn't it? Something out of the 'Journal of Astrobiological Biomechanics', I guess. It's time to look at rusps again. My big rusp painting is finished, and as it is meant as a double-page spread, it is large: 7200 by 2700 pixels. A spoiler is shown above showing a fragment of a rusp in the background of the painting. The fragment has been halved in size and its area represents just 2% of that of the entire painting. The painting is based on earlier sketches. For more on rusps, either visit the main Furaha site or look at these posts: sketches, anatomy, predation, concept paintings, etc.  

The evolution of new Furahan animals gets more complicated with time. In the beginning I just sketched a pleasing shape and started painting right away. Now, I worry more whether the animal makes evolutionary, mechanical and ecological sense. Well, up to a point; this is science fiction and supposed to be fun, after all. 

Here are some of the steps in rusp 'ontology': they started with some quick sketches, and then the slow evolution began: successive legs were offset medially and laterally to avoid legs bumping into one another, followed by an arrangement for their skeleton. Their fore and aft whips are long and held horizontally rather like the tails and necks of sauropods, and hence have a similar system of internal trusses as compressive elements at the bottom and ligaments at the top to withstand tensile stress. The whip is held up passively by these forces, so avoiding the high cost of doing that with muscle force only. The last stage involved refining the head of the rusp, and in particular its snout, or 'rostrum'. In an earlier post this rusp species was called Mammoth Rusp / Megacrambis, but now it is the Brontorusp / Brontocrambis; yes, that means 'Thunder Caterpillar'!  The Mammoth Rusp still had some intricate limbs functioning as additional feeding aids under its snout. I was not too certain of that arrangement, and my doubts were confirmed by comments on that post. So the Brontorusp no longer has these additional mouth parts. The thing is, now we have a massive animal with a large head. How does it feed itself?

The mouth of the rusp is in its head, which seems obvious but in speculative biology not many things are obvious. Also note that rusps are large herbivores: they need a lot of food and spend much of their time eating. Moving about is costly, so it would be best if they moved the least possible amount to get their food, which does not sound as if there is much room to save energy. Let's tackle that by considering the problem of getting an animal's mouth on vegetation; there appear to be four solutions to do so; rusps use the fourth, but we'll come to that. The first solution, always necessary as vegetation will not come to you, involves walking to the food source.

Click to enlarge; copyright Klein et al; Biology of the sauropod dinosaurs. Indiana University Press 2011
But once an animal arrives at its 'foraging station' a nice way to save energy is to keep most of the body motionless and to have a long neck allowing the head and mouth to move about independently of the gut. For very large animals, needing to feed all day, it pays to divide their anatomy in mouth and guts; the rest is just 'other bits'. Sauropod dinosaurs used that method, and the image above is from a study on how far sauropod mouths could reach, depending on neck length and leg length. The idea is that the neck can move in a horizontal plane 90 degrees to the right and the left, and in a vertical plane straight up and down. If the animal is lying on the ground the volume of space that it can reach is one quarter of a sphere. If the base of the neck is higher up, when the animal is standing, the volume increases. The authors assume that the bottom part of the volume then is cylindrical whereas I would assume that to be spherical as well, but never mind.

Click to enlarge; copyright Gert van Dijk
Swans and geese have very flexible necks and can probably reach every point within that envelope, but if an animal has a neck less flexible than a swan's, only part of the volume is accessible to the mouth. If this is the first time you realised that geese and sauropods might have long necks for a similar reason, good!

The image above shows an adapted 'forage volume' for a sauropod: the outer red sphere is the outer limit of where it can reach, and the inner blue sphere represents the inner limit, assuming that the neck is too stiff for the animal to reach a point closer to its body. The human ('Marlene') is just there to keep the sauropod in its proper place. 

The third solution to get the mouth near food is to use an appendage to shovel food towards the mouth. The best example I can think of is the elephant's trunk, which greatly increases the elephant's reach. The erstwhile rusp mouth limbs were short and not at all good as harvester limbs, and I did not wish to elongate them tenfold; they are gone. I also did not wish to turn the whip into a grasping organ. Rusp whips are not built for that, although in a pickle they can probably be used to knock a branch off a tree. Instead, rusps use a fourth system which is really just a combination of the last two: they carry their mouths towards the food without moving the rest of the head. The 'mouth extender' is extensible and based on a mechanical linkage system. In itself this is certainly not a new idea: Earth fish have such systems in abundance.

Click to enlarge; copyright Gert van Dijk
This image shows a schematic view of the rusp rostrum. Start with the red shape in the foreground: it consists of two V-shapes starting from a vertical axis. All places where elements meet are in fact joints. The pink axis shows that the whole ensemble can rotate, but it can do other things as well: if the two Vs rotate towards one another, the whole shape will become longer and narrower. At its right end, the shape ends in two points on a horizontal line. Now copy the shape, rotate it by 90 degrees, and you get the blue shape in the foreground. The two points where the red shape ends act as connection points for the blue shape. Once connected, some movements from the red shape are connected to the blue one, but not all, and that makes the rusp rostrum quite versatile. In the back you see how the rostrum is formed by stringing red and blue shapes together. In reality the trusses are not formed by straight bones, but by curved ones, so the section of the rostrum is circular rather than rhombic. The cylinder on the right attempts to show the outlines of the bones on a cylinder.


Click to enlarge; copyright Gert van Dijk
And this image shows an as yet unmentioned aspect of movement: if the two starting points are brought closer together, this changes the section of the rostrum as well as its length. The right one is extended, the middle one shortened, and the right one is in neutral position. I expect rusp rostra (yes, that's the plural) to be able to double in length.

Click to enlarge; copyright Gert van Dijk
But we need more flexibility, and that is achieved by rotating the shapes and using the angle between the Vs for additional control. The stylised skeleton in the back shows what can be achieved. So there we are: an extensible and steerable system to get rusp mouths where they would otherwise not reach.


Click to enlarge; copyright Gert van Dijk
Here are two views of an adapted Sculptris model of a rusp head. I take it you will recognise the system of trusses under its hide.

Click to enlarge; copyright Gert van Dijk
And finally, a schematic rusp foraging volume, rather like that of the sauropod (the whip of this model is truncated). Note that the rusp can access a larger portion of the outer foraging volume than the sauropod. The volume itself is smaller though, as rusps are smaller than sauropods, and their rostra extend their reach, bot nearly as much as the sauropod's neck does. Marlene is standing in the forage volume, something I would definitely NOT recommend! In practice, rusps are ground feeders, not bothering about high branches. Have I told you about the ecology of the spotted plains where they live, where post of forests alternate with plains and how rusp feeding habits are to blame for that? No? Oh well, that is another story.  

20 comments:

Petr said...

Wonderful post, Gert, thank you very much!

I think I have the rusp model planned out, I made some last minute adjustments to include the extended rostrum, I hope you'll like it.

I was thinking I could send the finished model to you as a late Christmas present.

Makes me sad I haven't thought of this earlier.

If you'd like, you can contact me through e-mail here:

monster.p.st@gmail.com

Take care!

Happy Holidays!

Pete.

Jan said...

Excellent! This solution sounds both plausible and original. Btw, saying that rusps are ground feeders means that there must be some other giant top feeders and that is definitely boost for our imagination (although I think that some specialized type of rusps with the ability to raise the front part of the trunk would be also a solution).

Sigmund Nastrazzurro said...

Petr: I am looking forward to that and have sent you a private email.

Jan: Oh dear, I hadn't thought of that!
Then again, I needn't worry, as I have made a painting of a long-necked hexapod with a limber body in the past. It is on a permanent loan to a friend of mine, so I will have to ask it back temporarily to scan it.

rodlox said...

May your holidays have been - and continue to be - utterly enjoyable.

You said there were 4 feeding strategies.
1. Sauropods & swans.
3. Elephants.
4. Rusps & fishes.
...what was #2?

all in all, this was a fantastic Christmas present to everyone who follows (and who will come to follow) your blog. kudos!

Sigmund Nastrazzurro said...

Rodlox: thank you. The list of feeding systems is aimed at mobile animals and sesslie food sources, and so does not include filter feeders. The list was as follows:
1. move the entire animal to the food
2. use a long neck to move the head+mouth to the food independent of the gut
3. use an appendage to bring food to the mouth
4. make the mouth mobile with respect to the rest of the head

Jan said...

So there would be another furahan animals more similar to sauropods?
I think that for a fast-feeding giant their bodyplan is near the perfection, except one thing - the position of the brain.
Ideally brain should not rest on a long slender neck, far from the heart, but every terrestrial animal has brain near the sensory organs and for them it is ideal position. Is there some solution? For example different neural mechanism, one which uses faster signals than ions, I think it would not only lead to faster reflexes, but would allow a different bauplans as well.

Petr said...

thbere is also the "elephant" solution. the brain is close to the heart and the sensory organs are near the brain andf there is this thing sticking out of the animal's head that basically does the same thing - reaches far to get food.

if you combine the two ideas, you¨ll get something with a pre-cranial vertebral culomn with just jaws at the end, and with eyes and brain in an actual skull near the main body and heart, you'll have a perfect mix :D

Sigmund Nastrazzurro said...

Jan & Petr: the only long-necked hexapod I ever painted does not have the enormous bulk of a sauropod and is not nearly as large. No long tail either. In stature it is probably closer to a giraffe than a sauropod.
As for the position of the brain, in many Furahan animals there is a visual nucleus in the head, but the main brain may be elsewhere. I may develop this theme in a post someday. It is linked to something I may have to study more, and that is to which extent never conduction velocity limits information processing. I doubt there are any formal studies on the subject (but have never searched for them).
As for blood pressure: girafes have extraordinary high blood pressure compared to other mammals, in whom pressure hardly scales with mass. Sauropods must have had even higher pressures. Apparently it is possible...

Petr said...

Yeah, high blood pressure is not impossible, I was just pondering an anatomy not found on earth... :D

Jan said...

Petr: Yes, but keeping the eyes at the end of the neck has its own benefits (one of the solutions could also be to have two "brain+eyes" complexes, one in the position of the elephants and one (with smaller brain) of the sauropods).

Back to the rusps, the evolutionary pressure would probably led to quite a long rostrum when prolongated. And their movement during feeding would not resemble anything known from earth. I hope I would see more pictures in the future :)

Petr said...

Jan: Yeah, that sounds interesting! :D

Sigmund Nastrazzurro said...

Petr and Jan: I was playing with the idea of doing more detailed studies of the movement of the rusp rostrum, but the is less easy than it might seem. It would be nice to have a program to simulate mechanisms in such a way that you could move them about while each joint has set of rules such as axes it works around with ranges of movement. I have nothing along those lines -unless that can be done in Matlab; I will check-.

On another note, the rostrum can indeed be worked upon to result in a larger range than Brontocrambis has, and so the idea came to me to stretch its leg, make the body narrower, to raise the head and raise the rostrum on the head, pointing upwards a bit; elongate the rostrum while keeping it 'gracile', and before you know it there is something you might call 'Giraffocrambis Janpetrii'...

Petr said...

that's amazing! :)

Uncephalized said...

Phew! I've finally caught up to the latest post.

And what's more, the material on this blog inspired me in my own world-building exercises. I have a space saga universe to populate and also a fantasy world to support a novel I'm working on. I am not the visual artist you are, but I've been sketching for days, inspired by your posts, and so far the ideas I'm generating are pretty interesting. So thanks for providing this resource!

Spearhafoc said...

Nice work!

I was wondering if anyone had any tips for 10 legged walk/run patterns? I'm not happy with the way I've designed Barsoomian banths.

http://spearhafoc.deviantart.com/art/Banth-size-comparsion-383959350

Sigmund Nastrazzurro said...

Spearhafoc: Nice Banth! The trouble with such a 10-legged beast is that it is hard to put legs on the beast in a way that makes sense. I suppose you have found my post on thoats? As Mars has a low gravity, a tetrapod of similar mass as one on Earth could do with thinner legs, and if you then take the number of legs into account, the legs can be even spindlier. Another problems with Martian fauna is that the legs will be very close together on a body with a 'normal' length this forces the legs on one side to move almost in unison. If you extend body length between leg pairs, you will up with a centipede-like animal. Finally legs can be offset sideways to let them move past one another. These seem the only ways to produce a banth or thoat with a believable anatomy and gait. Of course, the result is probably not at all what the casual reader had in mind.

Spugpow said...

Excellent post!

It's interesting that this rusp seems to have a narrow beak for browsing, whereas it seems like the rusps you've depicted so far living on the open plains are grazers.

Another method for bringing foliage within reach is to knock down the entire tree, which elephants are adept at. It's fun to imagine an even more battering-ram-like rusp doing the same.

Spearhafoc said...

Hmmm. The legs are described as powerful, so I can't make them spindly. Maybe I'll just stick to what I have, and accept the differences from reality as part of the same creative license that allows life on Mars in the first place.

Oh, and I did see your thoat post from a while ago. It inspired me to unfuse the legs, which I had done in my earlier sketches. Here's what I wound up with...

http://spearhafoc.deviantart.com/art/Thoat-size-comparison-384073292

And in Zbrush...

http://spearhafoc.deviantart.com/art/Thoat-final-colour-425603836

Thanks for all your help. Your site has been a great resource for my Mars project.

Uncephalized said...

"Petr and Jan: I was playing with the idea of doing more detailed studies of the movement of the rusp rostrum, but the is less easy than it might seem. It would be nice to have a program to simulate mechanisms in such a way that you could move them about while each joint has set of rules such as axes it works around with ranges of movement. I have nothing along those lines -unless that can be done in Matlab; I will check-."

You can do exactly that with SolidWorks, but it's very expensive if you can't get it through a group license (does your university's engineering department use it?).

Sigmund Nastrazzurro said...

Spugpow: the 'beak' is not a hard structure, so you should see it as a prehensile upper lip rather than as a parakeet beak. I will ad some wrinkles to show that.

Spearhafoc: indeed, the image that the Martian fauna is supposed to evoke in Rice Burrough's work differs fundamentally from what biomechanical reasoning suggests. My advice is not to care about scientific accuracy when depicting Burrough's life forms, as it will not work. The best way to solve the issue may be to go a bit over the top with your designs so the question whether the designs are realistic or not will not come up at all.

Uncephalized: I had a very quick look at SolidWorks. It looks impressive, but also daunting. Dear me; to do the site and the blog justice I tackled Painter, Photoshop, XFrog, Vue, Sculptris and various odds and ends such as CSS, InDesign and Matlab. I have now begun to take ZBrush seriously. Solidworks looks like a serious job to take on as well...