I frequently and regularly find Chaetonotus macrochaetus in the Purren pond and the Simmelried. The specimens are found mainly in the mud layer, but also in decomposing plant matter. The species is quite characteristic due to its long and thick spines, which bear a small secondary tip (s. fig. 7). The scales are trilobed and approximately 10 µm long in the middle of the body (s. fig. 6). All dorsal scales bear a spine, except for a field of small, keeled scales at the posterior end (s. fig. 8). On the ventral side there are small, keeled scales and two elongated terminal scales, which are also keeled (s. fig. 9). According to Schwank (1990), the ventral scales are supposed to be disc-shaped. In my specimens, however, they were more oval and also oblong in shape, with a length of 3–4 µm (s. fig. 9). As a further deviation, all specimens in my population were between 120–190 µm long and thus clearly above the range of 70–120 µm described by Schwank.

A very similar species is Chaetonotus persetosus. The distinguishing features from Chaetonotus macrochaetus appear to be only slight. The trunk spines are said to be shorter, and the ventral scales are supposed to be slightly hexagonal in shape and lack a keel. My specimens clearly possessed keeled ventral scales, which is why they must be Chaetonotus macrochaetus.