What did scientists believe was the first development of tardigrades?

Scientists believe that the first development of tardigrades was legs, which are key to their mobility and feeding behavior in their diverse aquatic environments. Tardigrades, often referred to as "water bears," are known for their ability to thrive in extreme conditions, and their legs allow them to navigate through their microscopic habitats. The presence of legs also suggests an evolutionary adaptation that helped these organisms to exploit various ecological niches, making them successful survivors throughout their long evolutionary history.

In contrast, wings, fins, and antennae do not represent the initial evolutionary adaptations associated with tardigrades. While some organisms may have evolved these features for different ecological functions, tardigrades specifically made their mark with their unique structure of legs that cater to their particular lifestyle.