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Description
The Ecdysozoic: an alternative timeline where vertebrates never managed to get much of a foothold on land. On this version of Earth, terrestrial niches are almost exclusively occupied by highly derived descendants of insects - specifically coleopterans - which have diverged into an astonishing variety of forms. They are the Lepidozoa, a clade whose geological longevity and mastery over the planet rivals the dinosaurs.

Several anatomical adaptations allowed this group of insects to exceed the physical limitations imposed on their smaller relatives. A rudimentary endoskeleton made of chitin supports the animal from within while simultaneously anchoring the muscles. The cellular cuticle, a mosaic chain-mail of chitinous deposits connected by epithelial tissue, provides flexible external armor somewhat similar to reptilian osteoderms. Unlike the rigid exoskeleton of base insects, the cellular cuticle grows with the individual, allowing them to bypass the costly chore of molting. The evolution of active respiration was an especially important development. Bellows, muscular contractile chambers, forcefully draw air through the spiracle and into the tracheal tube. Working in concert, 4-8 bellows can efficiently oxygenate even a large animal's blood.

The individual illustrated here is a generic bipedal predator, part of a genus which includes some of the largest Lepidozoans. A pair of forward facing eyes, far more acute than any modern insect, mark him as a hunter. His sharp beak, derived from mandible mouthparts, protects a long and flexible radular "tongue". Six limbs - each specialized for a different task - facilitate locomotion, hunting, and social display. As with all Lepidozoans, the ancestral wings and elytron are long gone (although some species later managed to re-evolve powered flight).

The two inset diagrams offer a closer look at structure of the cellular cuticle and spiracle bellows.

Description
The Ecdysozoic: an alternative timeline where vertebrates never managed to get much of a foothold on land. On this version of Earth, terrestrial niches are almost exclusively occupied by highly derived descendants of insects - specifically coleopterans - which have diverged into an astonishing variety of forms. They are the Lepidozoa, a clade whose geological longevity and mastery over the planet rivals the dinosaurs.

Several anatomical adaptations allowed this group of insects to exceed the physical limitations imposed on their smaller relatives. A rudimentary endoskeleton made of chitin supports the animal from within while simultaneously anchoring the muscles. The cellular cuticle, a mosaic chain-mail of chitinous deposits connected by epithelial tissue, provides flexible external armor somewhat similar to reptilian osteoderms. Unlike the rigid exoskeleton of base insects, the cellular cuticle grows with the individual, allowing them to bypass the costly chore of molting. The evolution of active respiration was an especially important development. Bellows, muscular contractile chambers, forcefully draw air through the spiracle and into the tracheal tube. Working in concert, 4-8 bellows can efficiently oxygenate even a large animal's blood.

The individual illustrated here is a generic bipedal predator, part of a genus which includes some of the largest Lepidozoans. A pair of forward facing eyes, far more acute than any modern insect, mark him as a hunter. His sharp beak, derived from mandible mouthparts, protects a long and flexible radular "tongue". Six limbs - each specialized for a different task - facilitate locomotion, hunting, and social display. As with all Lepidozoans, the ancestral wings and elytron are long gone (although some species later managed to re-evolve powered flight).

The two inset diagrams offer a closer look at structure of the cellular cuticle and spiracle bellows.