I'm working on building a species of wild animal, and I have several criteria in mind, and I'm looking for any glaring issues I may have missed that makes such a creature entirely infeasible scientifically. "Unlikely" is acceptable, and so is "evolutionarily impossible". I'm only concerned with "if such a species came in to existence through any means at all, could individuals survive their own biology long enough to reproduce, given acceptable environmental conditions?"

First, here are the criteria:

  1. Average healthy adult specimens will weigh 140kg-190kg
  2. Terrestrial, not aquatic (this is listed because later points involve a specific type of anatomical feature [water-vascular system] that is far more common in aquatic creatures than terrestrial, though there are exceptions)
  3. Legged locomotion. Bipedal, quadrupedal, hexapedal, etc., is yet to be determined, but will definitely have some form of legs or leg analogue appendages
  4. Endoskeleton
  5. Movement will be accomplished by means of a water-vascular system rather than conventional muscles. EDIT: In conventional muscles, movement is achieved by muscle fibers contracting and causing the attachment points at the extremities of the muscles to be pulled closer together. Water-vascular types of systems still use some conventional muscle material, but rather than the direct contraction of muscles being used to move appendages, the muscle contractions instead power what is effectively a hydraulic system inside the body, so appendages are moved by extension of the hydraulics, which pushes the connection points farther away from each other, in contrast to the contraction of conventional muscles bringing them closer together.
  6. To provide anchor points for the water-vascular movement system, the main skeleton expected in a creature that would otherwise be driven by normal muscles will be augmented by numerous and densely packed micro-bones that extend from the primary skeletal structure out to just under the surface of the skin.
  7. Tightly packed micro-bone structure causes relatively low body-water/fluid content by mass
  8. This dense skeletal structure and water-vascular system allow automatic sealing of damaged tissues, and immediate shedding of any destroyed bones and cells. This, combined with the low body-fluid content, causes the appearance of body tissue crumbling like damp dirt out of injured areas, and little to no bleeding.

The crumbling characteristic is actually the main desired point. Inspired by things like Golems, Gargoyles (that 'turn to stone' during the day), and many other rock-based and earth-based fantastical creatures, I'm trying to come up with something living in and of itself (as opposed to golems that are traditionally magic powered rather than truly alive), but with stone and earth/dirt-like characteristics. EDIT: There are two main types of "damage" that I'm envisioning. The first are what would normally cause punctures or cuts on a traditional earth mammal, bird, reptile, etc. and could come from teeth and claw injuries from either predators of this species, or from rival individuals within the same species itself, as well as humanoid species hunting them with arrows, spears, and bladed weapons. The second type is crushing damage, such as from a club or thrown stone or a fall from a significant height, in which I envision the micro-bone structure acting like a crumple zone, preventing the blow from reaching deeper bones. For both types of damage I envision that within seconds or, at most, minutes, the micro-bones that are broken on impact or by cut or puncture, as well as some of the very close surrounding tissue, are shed off like grains of sand, damp earth, or small pebbles, or a mix of similar, leaving an appropriately shaped depression/hole/furrow where the now-missing tissue used to be (until it can be re-grown or scarred over)

Is such a creature biological possible?

  • $\begingroup$ You go into detail about details but not details about the crumbling. I picture your creature like a big velvet worm. But under what circumstances does it crumble? When it dies? When it is escaping a predator? When it touches something - because I have to thing a terrestrial creature is touching the ground a lot. Please provide specifics about the crumbling you want. $\endgroup$
    – Willk
    Jun 18 at 21:05
  • $\begingroup$ "Terrestrial, not aquatic" and "Movement will be accomplished by means of a water-vascular system" - would these animals shoot jets of liquid into the air to move forward? $\endgroup$
    – Alexander
    Jun 19 at 2:33
  • $\begingroup$ @Willk I added detail on that. Does that clear it up for you? $\endgroup$
    – Harthag
    Jun 22 at 19:13
  • $\begingroup$ @Alexander I've included some additional detail and clarification on that. $\endgroup$
    – Harthag
    Jun 22 at 19:14
  • $\begingroup$ Why not just have an additional foamy-structured exoskeleton that directly takes the damage, then crumples? It would be more like seashell crumbling off than rock, but it would protect tissue. $\endgroup$
    – DWKraus
    Jun 22 at 19:30

2 Answers 2


How is it to be used?

Problem is that to possess a crumple zone/ parts that are designed to crumple. It will cost something to build. It will cost something to maintain. Yet a typical crumple zone is constructed of materials that are inherently one time use. That eliminates there use in items that have high cycle times like chewing, if truly one time use and break.

There could be concerns about creating an ideal habitat for fungi and other pathogens to grow. Warm, protected, likely to be moist.

Status for mating season

If its a system to be used semi regularly over some stretch of time ie. horns/antlers for mating season. Think bighorn sheep, deer, moose etc. It needs to be robust over multiple impacts. Generally if the structure breaks they are out of the competition at least for the season.

A defensive crumple zone wouldn't be used because then it would suggest last to arrive would win or the one that could just take the hits without crumpling or takes hits while crumpled would win.

No crumple systems here.

Offensive/ food acquisition:

Rodent teeth come close, they are designed to wear off in chips, continually exposing fresh sharp cutting surfaces.

Shark teeth also come close, they are on a conveyor belt type system continually bringing new ones into position, so if old ones break off, no problem.

Since such systems need to be reliable when ever they are use. Rodent teeth crumple, but they last many cycles before crumpling partially.


This is the most plausible to have crumple zones, but if it is to defend against an attacker, multiple hits/bytes will degrade the defense to nothing. So a crumple zone could be effective against ambush predators and ambush predators were common, then such a system would be feasible. Ie when attacked by single strike ambush predictor all it get its a mouthful of crumbles.

Against persistence or pack hunters, crumpling defensive structures would be of limited utility. Sure first few strikes will be ineffective, but eventually they could hit a vital spot with defense worn away.

Some plausible one time systems.

If it were to be a system the was to be used always guaranteed once. IE off spring are raised in a really tall tree/cliff etc. off spring leap out and rely on the crumple zone on landing discard and don't need it again. But question asks for non fliers

Or perhaps its a juvenile takes off on a once in a lifetime mating flight lands hard and disposes of wings and crumple system never to fly again. But suitably far form parent colony. Question asks about non-fliers

Perhaps something like a mountain coat with areogels, so if it fell uncontrolled the outer layers would collapse on impacts, allowing more/higher falls to be survived, but light enough not to be a hindrance. However the bulk of the crumple zone could contribute to the loss of balance.

Again if single strike ambush predators are common, then crumpling armor could be effective.

Crumple zones have limited use.

While there are a few scenarios where they would be of value and be plausible. Those scenarios are limited and likely to be out competed by systems that can take a hit without crumpling and be repaired. Ie fibrous material(hair, skin) over physical absorption layers (fat,muscle).


The only thing that comes close to this is when some species of gecko, salamander and tuatara intentionally sacrifice their tails to a predator so the animal can escape and the predator deals with a wriggling dropped tail.

The tail regrows and the gecko can repeatedly drop its tail if needed.

Your creatures might be able to drop their limbs from the shoulder or pelvic joint, if needed.


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