The only known specimen of Acherontemys heckmani was recovered from strata of the Roslyn Formation in Kittitas County, Washington.

[2] The turtle was collected from rocks exposed along a coal seam in the Northern Pacific Railroads Northwestern Improvement Company No.

[3] Acherontemys was originally assigned to the paraphyletic Chelydridae by Hay, a placement maintained by Robert L. Carroll (1988).

[4] J. Howard Hutchison (1992), however, classified it within Emydidae,[5] and this placement was maintained by Evangelos Vlachos (2016), who placed it in the Testudinoidea clade Pan-Emydidae.

[6] Vlachos notes the extra-wide vertebral scutes as distinguishing A. heckmani from any other testudinoid taxa of North America, though the size is seen in some European geoemydids.

[6] Both authors note the distinctly wide nature of superpygal II, which is rectangular in general outline and spans the width of the 3 rear peripheral bones.