Phylogeny of Thoracostomes

Thoracostomes (thraxes for short) are among the most successful land animals on Ilion. 92% of detritivores and 60% of primary consumers belong to the group, owing to their versatile design and rapid rate of reproduction, among other things. They are named for the placement of their mouth, which is not in the front as in other red plant derivatives, but on the chest between the front pair of limbs. The mouth, which contains a radula, lies flat against the ground. Since this arrangement is not conducive to breathing, oxygen and carbon dioxide must diffuse across the skin.  As a result, thoracostomes adapt well to an amphibious lifestyle in freshwater habitats.

Anatomy

Hexapede thoracostomes – A single mutation caused all of the ancestor’s offspring to develop only six out of fourteen legs. Amazingly, this deformity did not affect organ function and the lineage grew into one of the most adaptable animal groups on the planet. Due to their ability to concentrate toxins, microbes, and pigments in their skin, some species can be quite colorful.

Tube-footed thraxes – Members of this group share many similarities to their sister clade but with longer bodies. Most tube-footed thraxes rely on concentrated toxins and warning coloration to make themselves unappetizing to predators, while others get by with camouflage. Some species have a special stomach compartment for fermenting black plant microphylls, which are normally too difficult to digest through conventional means.

Microthraxes – Measuring in the millimeters, microthraxes play an important role returning nutrients to the soil. They are found in leaf litter, fur, and decaying organisms, feeding exclusively on dead material. Their eyestalks, while still functional as sensory organs, serve mainly to manipulate food.

Clawed thraxes – Like the name indicates, these animals have claws on their feet for clinging to trunks and branches. Their jointed, dexterous eyestalks are perfect for seeking out higher quality food sources such as red plant fruit buds and small animals.

Stack-eyed thraxes – While most thraxes have rudimentary vision, their visual acuity is poor. Stack-eyed thraxes evolved to secrete a substance into their heat pits that hardens into a lens. The lens only lasts a limited amount of time before it becomes too cloudy to see through and must be shed on a regular basis. The photoreceptors fall out with it and a new eye and lens erupts from below, much like shark’s teeth.

Zoom out: Red plant derivatives