The fossils of Ascendonanus are of special scientific importance because they include remains of skin, scales, scutes, bony ossicles, and soft-tissue body outlines, which could indicate that some of the oldest relatives of mammals had a scaly "reptilian-type" appearance.

It is the smallest known member of the clade Varanopidae, a group of early synapsids that generally resembled the unrelated monitor lizards.

Features that identify Ascendonanus as a "pelycosaur" grade synapsid and a member of the Varanopidae include a single lateral temporal opening (fenestra) in the skull, a ridge on the underside of the centra of the vertebrae, and enlarged blades on the ilium of the pelvis.

[1] The five recovered fossils of Ascendonanus are strongly compacted and were split open as flattened counterslabs that revealed articulated partial or near complete skeletons with remains of soft tissue and some internal features.

The most remarkable specimen (MNC-TA1045) preserves the clear body outline of nearly the entire animal on counterslabs, showing the thickness in life of the limbs and the neck, and the full covering of scales.

Such eyelid ossicles are currently not known in any other amniotes, but have been found in some dissorophid temnospondyl amphibians, a non-amniote tetrapod group that is not closely related to synapsids.

[1][7] The specimens show a regular scale pattern over their bodies, similar to living squamates and archosaurs, suggesting dry, scaly skin was present in the earliest amniotes before the split into synapsids and sauropsids (reptiles) during the Carboniferous Period.

In addition to finding fossils of trees and plants at the Hilbersdorf site, the team recovered remains of vertebrates (synapsids, temnospondyl, aistopods) and arthropods (scorpions, Arthropleura, spiders), some later identified as species new to science.

[1] A second fall of wet ash quickly buried the Ascendonanus individuals and the other animals that were on or under the forest floor up to about 53 cm deep, preventing decay and preserving bodies largely intact (but compacted over time), with detailed impressions or traces of soft tissues.

[1] Later, more violent phases of the eruption covered the wet ash layer in much deeper deposits of coarser hot pyroclastic material that make up most of the Zeisigwald Tuff Horizon (total depth up to 4 m).