Sulfonecta uniserialis was first described by Levander as Caenomorpha uniserialis. This name was also adopted by Kahl. Later Caenomorpha uniserialis was transferred to the genus Sulfonecta by Jankowski. It is the only species in the genus Sulfonecta. We will see if this remains to be the case.

In my localities Purren pond, Ulmisried and Simmelried I find Sulfonecta uniserialis frequently and regularly in the mud zone. The species has two caudal spines, but they are comparatively short in relation to the body length. The broad and flat apical dome makes Sulfonecta uniserialis look almost somewhat lenticular at low magnifications. The centrally located primary spine is conspicuously swollen in the middle or last third. I have never found specimens without this swelling. In addition, this primary spine still has an accessory spine, which was always short and pointed in my population (s. fig. 2 b). The secondary spine is much shorter and somewhat displaced towards the outer margin (s. figs. 2 c and 3 b). In my population it was always slightly curved towards the central long axis. As in Caenomorpha medusula and Caenomorpha sapropelica, the cytopharynx is situated near the contractile vacuole and oriented toward the anterior end (s. fig. 1 c). Unlike these two species, Sulfonecta uniserialis has only one row of cilia on the apical dome instead of two. This row of cilia is located on the left side and is difficult to recognize. According to Kahl, this row of cilia is supposed to be soft cirri, which disintegrate due to coverslip pressure. The macronucleus is large and spherical, while the micronucleus is exceptionally small and attached to the macronucleus (s. fig. 3 b). I was able to detect symbiotic bacteria in the cytoplasm of all investigated specimens (s. fig. 3 a-b). Although I did not examine these more closely, several different forms (species) of bacteria were clearly visible.