So far I have only found one specimen of Chaetonotus soberanus in December 2022 in an old sample of mud from the Simmelried. However, it is possible that I have overlooked other specimens so far.

Chaetonotus soberanus was first described by Grosso & Drahg in Argentina in 1983. Subsequently, the species was recorded in 2013 by Kånneby in Sweden, who also only found 1 specimen. No further records have been documented to date.

I only found the specimen after I had already placed a coverslip on it. I found the specimen still freely swimming (s. fig. 1 a-c). After reducing the layer thickness, it was fixed with the ventral side facing the coverslip. The anterior two thirds of the ventral side are covered with transversal scales with a jagged ornamentation, while the posterior third is covered with roundish, keeled scales (s. fig. 2 b). This arrangement is characteristic of Chaetonotus soberanus. In order to view the dorsal side, I tried to turn the specimen under the coverslip, whereby it twisted slightly. Nevertheless, I was able to recognize the dorsal arrangement of the scales (s.  fig. 3 a-b). The larged round scales are in the middle of the trunk. Towards the posterior end, they become smaller. I could not recognize their exact shape because the layer thickness of the sample could not be further reduced.

Chaetonotus soberanus is probably identical with the species Chaetonotus macrolepidotus macrolepidotus. This species was raised by Kisielewski because he considered the species Chaetonotus ophiogaster and Chaetonotus macrolepidotus to be synonymous. Chaetonotus macrolepidotus macrolepidotus is said to have the ventral scale pattern of Chaetonotus ophiogaster and the dorsal scale pattern of Chaetonotus macrolepidotus. In my opinion, however, Chaetonotus soberanus is much better defined and also confirmed by the new description by Kånneby (2013). It also coincides with the characteristics of my specimen, which is why I consider the specimen to be Chaetonotus soberanus.