Geminorum-F Fauna – Octopods Anatomy

Geminorum-F is a unique planet, currently undergoing desertification, a consequence of Pangaea. On this planet, vertebrates are becoming scarce, supplanted by arthropods and invertebrates, which have adapted more quickly to new ecosystems.
Among the arthropods to have benefited from this evolutionary boom, the "Octopoda" group is undoubtedly the one that has adapted and diversified the most. The two groups nicknamed "Octopoda" were partially predominant in terrestrial ecosystems, but were limited in size by predation and a lack of space in ecological niches before the crisis. But when predators disappeared and ecological niches emptied, this allowed them to adopt sizes and behaviors much closer to the vertebrates of the time, while also being more resistant to the new climates that desertification brought with it. The "Octopoda" are actually two groups:
Archaeoctopoda, recognizable by their lack of wings, their partially fused thoraxes, and their appearances that sometimes resemble a fusion of insects and crustaceans.
And Neoctopoda, recognizable by their integumentary wings, their more pronounced insect-like appearance, and their double-clawed feet (sometimes more than two on the forelimbs).
Their anatomies nevertheless share many similarities, suggesting that the two groups shared a common ancestor.
The major difference between these "insects" and those on Earth is their number of limbs: eight legs, which means one more pair than the hexapod insects on Earth. This is explained by the presence of a fourth thoracic segment, preceding the traditional "pro-meso-meta-thorax," the Pulmothorax, where lung-like organs are located (but also where part of the brain of these animals is located).
These lungs and the active respiration that results from them are what allowed these arthropods to develop colossal sizes, some reaching the size of dogs or sheep, and the largest specimens have been observed to be close to the size of rhinoceroses or bison.