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Description

A single tube mouth-foot unit animation showing the typical gait for this type of appendage, shown at 5x normal speed. Tube Mouth-Feet are present in just about every ambulatory clade, suggesting a common ancestry and high utility. In its most basal form they are nothing more than absorptive paddles on the boral surface of Tidal or River Plates, used as both locomotory oars and root-like feeding surfaces. They were later modified by terrestrial plates for actual movement in following the tides and rest of the colony, only to eventually become strengthened with rigid osmotic tubes that allowed for more efficient terrestrial movement. This adaptation is thought to have led to the explosive radiation of terrestrial forms, leading to Bryotes, Stars, Bugs, and ultimately to larger forms like Ladons and megafauna with the adoption of bony elements.

This older (fav.me/dcg83ms ) sketch for reference.

Each unit consists of two pairs of tube mouth/feet on two rolling halves of a rotating coxa. Driven by osmotic muscle pumps and a compressible fluid-filled bladder inside each half, the legs are pumped full of fluid each in turn and drained with the forceful filling of the other so that there is always one foot in contact with the substrate. As each foot is drained and deflated it carries with it a mouthful of material which it passes into an esophageal tube for material processing and digestion. Important nutrients for growth and photosynthesis (or digestion if heterotrophic) are passed to the circulatory medium, where they are ferried to the appropriate cellular (or in this case, meta-cellular) body. This slight suction is amplified in derived terrestrial forms to aid in climbing vertical surfaces (itself thought to be another spur in the adaptive radiation of the multitude of forms).

The entire coxal unit can rotate and pivot in the perpendicular axis through the expansion of osmotic tissues, later developed into muscles. The oscillating motion of the hemispherical units is partially driven by the squeezing and relaxing of the fluid bladders inside, which also gives them shape and form for muscle attachment through hydrostatic rigidity.

Description

A single tube mouth-foot unit animation showing the typical gait for this type of appendage, shown at 5x normal speed. Tube Mouth-Feet are present in just about every ambulatory clade, suggesting a common ancestry and high utility. In its most basal form they are nothing more than absorptive paddles on the boral surface of Tidal or River Plates, used as both locomotory oars and root-like feeding surfaces. They were later modified by terrestrial plates for actual movement in following the tides and rest of the colony, only to eventually become strengthened with rigid osmotic tubes that allowed for more efficient terrestrial movement. This adaptation is thought to have led to the explosive radiation of terrestrial forms, leading to Bryotes, Stars, Bugs, and ultimately to larger forms like Ladons and megafauna with the adoption of bony elements.

This older (fav.me/dcg83ms ) sketch for reference.

Each unit consists of two pairs of tube mouth/feet on two rolling halves of a rotating coxa. Driven by osmotic muscle pumps and a compressible fluid-filled bladder inside each half, the legs are pumped full of fluid each in turn and drained with the forceful filling of the other so that there is always one foot in contact with the substrate. As each foot is drained and deflated it carries with it a mouthful of material which it passes into an esophageal tube for material processing and digestion. Important nutrients for growth and photosynthesis (or digestion if heterotrophic) are passed to the circulatory medium, where they are ferried to the appropriate cellular (or in this case, meta-cellular) body. This slight suction is amplified in derived terrestrial forms to aid in climbing vertical surfaces (itself thought to be another spur in the adaptive radiation of the multitude of forms).

The entire coxal unit can rotate and pivot in the perpendicular axis through the expansion of osmotic tissues, later developed into muscles. The oscillating motion of the hemispherical units is partially driven by the squeezing and relaxing of the fluid bladders inside, which also gives them shape and form for muscle attachment through hydrostatic rigidity.