14:32 21-04-2012
Spugpow: do you mean the tongue-like organs? those are derived from lateral jaws. Or do you mean the internal jaws that grind food? Those are an independent trait, and not related to the dermal skeleton.
As for the methane base, well, perhaps that gave rise to a material suited for an unbelievably strong skeleton that is ridiculously light. But I would be happier if this was fleshed out more, pardoning the pun.

Evan: the Fishes teeth-analogues indeed work well with slippery prey. When I first designed neocarnivores with beaks, I felt that their clubs could take over that role entirely. I do not think there is an evolutionary advantage in losing teeth, unless it is to lose weight. I am considering what to de with teeth; have a look at my latest blog entry, posted a few minutes ago...
01:43 21-04-2012
Are the internal jaws of the hexapods actually derived from mouthparts, or are they more gizzard-like?

Or are they extensions of the shoulder blades or something?
01:40 21-04-2012
The Mesklinites are methane-based, which might explain their low density.
19:28 20-04-2012
Evan Black

Thanks for that diagram of the head. Since the original picture of the Drasa has the head from the side, it was hard to tell how wide it was. Knowing that it actually sits between the eyes helps me understand how it's situated. I feel presumptuous asking this, but could we see a front view of the head as well? Even with 0.6 g, the neck might need to be a touch thicker to support the head if it's too massive.

How does flora and fauna diversify in caves more than in other biomes of the planet? As I understand it, biodiversity depends on available resources, amount of area, and on competition with other organisms. A small patch of rainforest, for example, typically has more biodiversity in it than an entire desert because resources aren't as scarce. A desert, even with scarce resources, can potentially support a higher biodiversity if it is larger, because different species can spread out and not compete over the same localized resources. A species with NO competitors can get along just fine, so long as it can support its own population.

So how much surface area do these cave biomes actually have in comparison to the desert, plains, forests, and (I presume) marine biomes? How does cave flora photosynthesize?


Am I correct that the reason sawjaws have retained their teeth is so they can hold on to "fish" prey? Also, is there a specific reason for widespread use of beaks instead of teeth among neocarnivores? Is it simply because of a beaked common ancestor or is there some evolutionary pressure I'm not realizing?
17:27 20-04-2012
Jan: not entirely. As you can see from the sawjaw, the basal hexapod design does include teeth-analogues. Howver, most neocarnivores have reduced or no teeth, using beaks instead. In all hexapods the main food-grinding machinery is placed in the torso anyway. The mouth is to catch a prey and present it to the internal jaws, where grinding is the first processing step. Neocarnivores use their clubes to smash and break, and use beaks to reach inside. Of course, there are some bone-crushing scavengers with powerful jaws.
13:04 20-04-2012
Btw, maybe I have already asked, but it seems that Furaha carnivores do not have teeth. Is it true?
04:45 20-04-2012
@Evan Black- You'll have to forgive my photoshopping skills, but this is a quick diagram of a Drasa head. I think perhaps a human brain may be a bit larger, but not by much. I haven't included much more detail, but eventually I will
02:42 20-04-2012
@Evan Black & SN: I really like the idea of spreading weight differently by how the toes are positioned! That never even occurred to me, thank you so much.
@Evan Black: I suppose my statement about Drás' ecosystems was a bit vague as well. Although much of the planet is indeed desert, that's not to say that there aren't other ecosystems as well. Drás has wide expanses of plains in some regions and even some sparse forests, however much of the flora and fauna diversity is located underground in caverns, tunnels and underground waterways. I'll come up with a sketch tonight on the Drasa head anatomy and post it soon! Thank you guys again for your input, I really do appreciate it.
21:00 19-04-2012
Evan Black
Sigmund, I suppose there is a possibility that the 2 pounds referenced in the book was an attempt to give a relative weight for readers, and that a kilogram is roughly what the Mesklinites would weigh in 1 g. In which case, Mesklinites would probably fit somewhere around your own predictions on density and weight. However, when taken at face value, the Mesklinites come out being only a little more dense than cork.

One last thing I'd like to point out with my investigation into details from the novel is the article called "Whirligig World," added as an afterword in the edition I read. In it, Clement refers to the relationship between a Science Fiction writer and his or her audience as "playing a game." The author's role is to follow scientific knowledge as closely as it is currently understood, and the role of the readers is to measure the details of the book against any subsequent scientific discoveries to see if it still holds up. He actually describes the whole process as "fun." I admire this attitude, not the least of which because it's a justification for one of my favorite things to do when reading sci-fi. I encourage everyone with enough interest to pick up the gauntlet Clement has thrown.

I tried my hand at a couple of rough sketches of a Mesklinite more closely matching what's described in the book while in class today, and I would suggest looking to Furaha's rusps for inspiration.

I look forward to your blog post!
20:29 19-04-2012
Evan Black

When you say things like, "It is largely a desert world, although early on in its development it had a bit more vegetation, but nothing significant," that's a potential red flag. Why do native animals derive and radiate, but plants don't find more complex niches? If the planet is mostly desert, how is it habitable? Or is this a Star Wars planet?

Even with the scale of 3 meters indicated, I still have a hard time understanding how a human sized brain fits into the head in that image. I'd like to see that anatomical diagram of the head, if possible.

I don't think the tiptoe strategy would help with soft, sandy dunes. That kind of terrain requires a broad, snowshoe style of foot to spread weight over a surface area. The feet as they are in the picture seem ideally suited to climbing or other mountainous/cavernous activities as well as walking on hot rocks. Do a Google image search for slickrock caves and you'll see what I'm imagining.


"Basically, their musculature and general physiology would make them predisposed to rolling, so the first on land were rollers."

Statements like that fall into the category of things I need like to see further explanation to fully comprehend. Do you have diagrams or something to show how this clade was predisposed for rolling? Also, the first land dwellers doesn't necessarily lead to sapient life, otherwise arthropods would have showed us up some time ago. Also, even if rollers got the head start, how did they out-compete the much less complex (and therefore likely to be more robust and evolutionarily fit) walkers? There are also some gaps in how the few roller clades that survived the extinction turned into sophonts. It's like saying that rodents survived the KT extinction and gave rise to humans. Such a description may work just fine in some contexts, but when sapient rollers are such an "outside-the-box" concept, you really want to show your work. Secondly, rollers aren't as likely to fill generalist niches, which are the types of species that are more likely to survive extinction events. How do they survive and go on to become sapient when all of their walking cousins just can't make it?
20:18 19-04-2012
DrásResearcher: Joints in segmented limbs are places that call for active muscle control, meaning energy expenditure. More joints, keeping joints bent, long segments, high mass and high gravity all increase that cost. On a low gravity planet you can get away with more than if gravity is high. But if you wish your creature to carry heavy burdens, fewer segments will help.
I think you should adopt Evan's idea of making the toes multifunctional: on hard (or very hot) surfaces you can keep them together and even have the animal walk on its knuckles, with the digits bent back. On shifting sands it could spread its weight on the toes, now held horizontally.

Evan: the figures you found for the Mesklinites' weight are astounding. I guess there is no possibility of mass being mistaken for weight? I guess not, particularly if there is specific mention of this value holding at 3g. I am afraid that you are right, and that Clement made an error here. Pity. The density you calculated should include the skeleton, after all, and in this environment the skeleton will make up a sizeable portion of body mass.
By now, this Mesklinite business represents about enough work to be worthy of a blog post in its own right. Perhaps if I paint a redesigned Mesklinite alongside? I would have to read the book again first.

By the way, I expect to relaunch the blog shortly (Sunday, probably). Nothing fancy; just 'Four years on...'
05:49 19-04-2012
@SN- Would you say that if there were 3 segments in the rear two legs it would be more conducive for carrying slightly heavier loads than she could now? Also, they spend a lot of time in caves, hence the toes needing to be arched up so high so that they can maneuver around difficult areas, but would it also assist them in sandy dunes?
01:02 19-04-2012
Evan Black
Another datum I gleaned from the text of Mission of Gravity:

Apparently, the Mesklinites weigh two pounds in the equatorial 3g region. That's a very surprising number. That comes out to 0.9072 kg, and therefore 0.3024 kg in a 1g environment. With the volume of a cylinder 38.1 cm long and at 5.1 cm diameter (if I've done my calculations right) that's only 388.53 kg/m^3, little more than a third of the density of water. So either there are some complex biochemical things going on (Mesklin has ammonia snow, after all) or Clement is showing that while his astrophysical calculations have withstood the test of time, his biology might leave something to be desired.

The Drasa legs seem to me like they're configured so that they're quite versatile. In the image the legs seem more columnar, but they seem like they might be capable of a wider, more stable stance, at least long enough to ride out a windstorm. In any case, winds may be relatively mild on the planet, making it something of a non-issue.

The toes could be splayed for soft ground or marshes, but given their desert location, they could also play the role of keeping the feet off hot surfaces (lizards at rest will sometimes hold a foot in the air to let it cool off, then hold up the next and so on) or aid in sure-footedness in more mountainous regions.
00:15 19-04-2012
Evan (it feels strange not calling you empyreon. Speaking of which, are there reasons you stopped frequenting the forum aside from being busy?), I somewhat addressed your question. Basically, their musculature and general physiology would make them predisposed to rolling, so the first on land were rollers. Therefore, they had time to fill a variety of niches before walkers arose, and they tenuously maintained this role as the dominant phylum for maybe one or two hundred million years, after which a mass extinction allowed the walkers to take their place. Some rollers lived on and eventually spawned the sophont, though I'm not sure how much longer after the extinction. They became intelligent mostly due to their relationships with their epitokes, which they only developed to the extreme they did because of their walk cycle's inefficiency in relation to the walkers. So yes, there's competition, but the competition only got fierce after they had time to diversify, and when it did get fierce, it's what led to the rise of intelligence.

As for how the walkers walk, I'm thinking there will be two branches of walkers: the centipedes/snakes you mentioned, which developed early on, and another group that split from the rollers, which walk sideways, in the direction the rollers roll.
22:51 18-04-2012
I'm glad you want to hear more information about the Drasa! I didn't know if I would be over sharing or not. I'll address all the questions posed by Evan Black and SN:
1) Homeworld gravity: Yes, Drás is smaller than Earth with approximately 0.6G. It is largely a desert world, although early on in its development it had a bit more vegetation, but nothing significant. The winds can be very strong in a region called the Outer Desert, so named because the planet is tidally locked to Kuar, its parent gas giant.
2) Size: The Drasa are fairly tall, averaging 3 meters in height, although males tend to be a bit smaller.
3) Evolution: Drasa ancestors were small, cave dwelling "spider-like" creatures that made use of Drás' intricate caves and tunnel systems. As resources became depleted in some cave niches, some of these creatures ventured out in the open to find other caverns. This line would eventually evolve into the Drasa.
4) Diet: Omnivorous.
5) Sentience: The biology of many of Drás' species includes a separation of feeding and breathing tubes, with the inhalation openings near the chest and exhalation near the rear. As such, the head is not bothered with a large nasal cavity. The brain is comparable to a human sized brain (I have drawn a picture of a Drasa head in profile with the anatomy outlined; however, its a rough sketch and I haven't fixed it up with color or photoshop!)

Hope that answers some questions! I really appreciate your feedback and comments
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