Many different organisms on Sagan IV have different strategies for supporting their bodies. This page acts as a reference for what each type of support refers to.
If the support for a terrestrial organism's torso and limbs are different, both need to be included (ie, "Endoskeleton (Chitin), Hydrostatic Legs"). Some organisms may have more than one kind of support structure.
Note that the support an organism uses can't always change easily. Be sure to do research before changing it.
This section covers support on the level of cells.
An organism which has no cell wall is instead supported by its cytoskeleton. A well-known real-world example is the amoeba.
Format: Soft-Bodied (Cytoskeleton)
Examples: Chaoses, Goliathpseudopodia, Foi
Cell walls are present in unicellular organisms and in many kinds of flora. The material of a particular cell wall influences an organism's needs, limitations, and flexibility.
Format: Cell Wall (Material)
Cellulose is one of the most common cell wall materials for macroscopic organisms. On Earth, it can be found in plants, algae, and some slime molds. It is difficult to digest and very flexible. For herbivores, digesting cellulose requires a large gut.
Examples: Purple Flora, Black Flora, some Plent Flora, their unicellular relatives
On Earth, chitinous cell walls are only found in fungi and lichen. Chitin requires a lot of nitrogen to grow, and as a result organisms with chitinous cell walls grow more slowly than those with cellulose. Like cellulose, chitin is difficult to digest and herbivores may need a large gut to digest chitinous flora.
Examples: Crystal Flora, some Worm Flora, Glass Flora, their unicellular relatives
Silica cell walls, such as those of diatoms, are inexpensive to make, but also completely rigid. An organism with a silica cell wall must be able to reproduce in a way other than mitosis or binary fission, as silica cell walls cannot expand.
Some fauna are soft-bodied. Soft-bodied organisms struggle to attain large sizes, as they usually must keep their muscles tensed constantly to stand upright.
- As primary support: Soft-Bodied (Method)
- As secondary support: <Method> <body part> (ie. "Hydrostatic legs")
A hydrostatic skeleton is a fluid-filled sac, or a set of them, which is used as an extremely flexible endoskeleton. A well-known real-world example is earthworms.
Examples: Ukfauna, basal carpofauna
A muscular hydrostat is where solid muscle on its own supports and moves the organism or body part. Many organisms on Sagan IV have muscular hydrostats for tongues.
A hydraulic system has some similarities to a hydrostatic skeleton, in that fluid is used to move and support the organism. Water pressure is used to move the body and limbs. A real-world example is echinoderms.
An endoskeleton is a skeletal support which is located inside an organism's body. A piece of an endoskeleton may be casually referred to as a bone, even if it is not technically made of bone.
Format: Endoskeleton (Material)
A rigid endoskeleton does not easily bend. Real-world organisms with rigid endoskeletons include bony fish, starfish, and cuttlefish. Most rigid endoskeletons are mineralized. In addition to materials found on Earth, Sagan IV includes a unique bone material, petrolignin, which is a type of mineralized cellulose used by some plents.
Mineralized endoskeletons are heavy, but this can be alleviated if they are made hollow. Examples:
- Bone: Spondylozoans (Dwellers, Shrews, Snappers, Limblesses, Snarks, Scylarians, etc.)
- Calcified Chitin: Hagloxes
- Petrolignin: Some plents
Some organisms have rigid skeletons made of different materials which are not mineralized.
- Sclerotized Chitin: Saucebacks, Murkworms, Lizardworms
A non-rigid endoskeleton can bend easily. Some real-world examples include squids and cartilaginous fish.
Wood as an endoskeletal material is exclusive to plents. Though technically non-rigid, wood is in a category of its own because it is so flexible that it can bend from an organism's own muscles pulling on it.
Unjointed wood, as an endoskeleton, means that an organism's skeletal structure is rope- or basket-like and has no distinct joints or individual bones. Especially useful in smaller organisms, unjointed wood bones can snap back to their original shape with little energy. Most plents retain some unjointed sections of their skeleton even if they have evolved joints, as in larger species unjointed wood can form stiffening rods and hold largely immobile body parts upright with little energy.
Examples: Basal ambulatory plents, most living phlyers, nobits
Jointed wood, as an endoskeleton, means that an organism has distinct separate wood bones which function similarly to a rigid skeleton. Many larger and more derived plents have jointed wood bones in their legs. In smaller species, jointed wood can still bend from muscles pulling on it; however, the skeleton will often bend at the joints first.
Examples: Gulpers, nodents, ketters, lickers
Semi-jointed wood has characteristics of both jointed and unjointed wood. Usually, the skeleton is a single continuous wood bone, but certain parts are thinner than others and are therefore more flexible like joints. In a larger organism, semi-joints might be used in place of true joints where extra flexibility might be needed in an otherwise unjointed part of the skeleton.
Examples: Gamergate Gundis
An exoskeleton is a skeletal support located on the outside of an organism's body, which generally covers all or most of its exterior (as opposed to a shell, which only covers part).
Format: Exoskeleton (Material)
- Chitin: Most binucleid worms, many anipedes
- Cellulose: Most living skuniks
A shell is a single or paired piece which is technically a type of exoskeleton, but does not support the whole body. Shells are usually rigid.
Format: Shell (Material)
- Calcified: Shelled urchips
- Sulfur: Bubblehorns
Most flora have cell walls, but there is additional support unique to them.
Usually the stem is not mentioned in support unless it has properties which make it hold itself up better than the cell wall alone.
Format examples: Woody Stem, Chitinous Stem, Calcified Stem
The distinction between a woody stem and a trunk is largely subjective. If you might call your organism a tree, though, it should probably be called a trunk.
Format examples: Woody Trunk, Chitinous Trunk, Calcified Trunk
Heartwood is dead wood found in the center of some trees. If the heartwood is made of a material other than cellulose, it must be specified.
Format examples: Heartwood, Chitinous Heartwood, Calcified Heartwood