[3][4] Specimens of Zospeum tholussum were recovered by a team of cavers and biologists of the Croatian Biospeleological Society (Hrvatsko Biospeleološko Društvo or HBSD) from the Lukina jama–Trojama cave system in the Velebit mountains of Croatia, during an expedition from July 29 to August 8, 2012.

[8][9][10] The expedition was primarily to determine the cave system's depth,[11] but the team also collected specimens of animals they encountered.

[6] The cave system is unusual for containing three different microclimatic layers which makes it extremely interesting in terms of biodiversity to scientists.

[12] The first 200 m (660 ft) of the cave system's entrance is permanently covered in thick layers of snow and ice and has an average air temperature of 1 °C (34 °F).

[5][6] The cave system progressively becomes warmer in deeper areas, with an average air temperature of 2 °C (36 °F) in the middle part and 4 °C (39 °F) at the bottom.

[5] They also recovered a single live specimen of Zospeum tholussum from an unnamed large chamber at a depth of about 980 m (3,220 ft).

[5] Zospeum tholussum was formally described by the German taxonomist Alexander M. Weigand in 2013, based on the specimens the caving expedition recovered.

The specific name is derived from Latin tholus, meaning dome or cupola, referring to the distinctive dome-like shape of the second whorl of the shell.

The nine type specimens are currently deposited in the Forschungsinstitut und Naturmuseum Senckenberg in Frankfurt am Main, Germany (museum voucher SMF 341633).

[14] Weigand identified Zospeum tholussum as a new species based on the morphology of the shells, as well as molecular genetic data recovered from the single living specimen.

However, no living specimens of this species were recovered, so DNA barcodes could not be obtained to determine its exact taxonomic relationship with Zospeum tholussum.

[5] The shells of the collected specimens of Zospeum tholussum have a moderately variable morphology between individuals in the species.

[12] Because of their proximity to bodies of water and their preference for habitats with a mud substrate, Weigand and colleagues (2013) have proposed that the primary mode of dispersal of Zospeum species may be passive, either by being carried along in running water or through the activities of larger animals like cave bats or crickets.