Planometopus contractus was first described by Penard in 1922 as Metopus contractus. This name was adopted by Kahl. In 2018, Rottovera et al. redescribed the species and transferred it to the newly established genus Planometopus based on morphological characters and the results of 18S rRNA gene analysis.

So far I could detect Planometopus contractus exclusively in the Simmelried where the species occurs sporadically. The shape of Planometopus contractus is very variable, which is also mentioned by Kahl and Rottovera et al. I found stocky, almost rectangular specimens (s. fig. 3 a-b) and also more elongate, oval specimens (s. fig. 1 a-c). However, all forms are distinctly dorso-ventrally flattened (s. fig. 2 b) and the apical dome is flat and distinctly curved ventrally (s.  fig. 2 b). Overall, the ciliate appears very rigid and not flexible. What is also striking compared to other metopid ciliates are the widely spaced rows of somatic cilia, which are running obliquely and in a counterclockwise manner. This can be seen especially clearly on the dorsal side (s. fig. 3 b). In my population, I could observe very large symbiotic bacteria in the cytoplasm, which accumulated around the macronucleus (s. fig. 1 c). Since these symbiotic bacteria are not mentioned by Kahl or Rottovera et al. it is unclear whether this is a constant feature. The long caudal cilia appeared spread in a fan-shaped way in some specimens, whereas they were soft and flexible in others.