Fossils of Mixopterus have been discovered in deposits from Late Silurian age, and have been referred to several different species.

[5] By thrusting and pushing the tail, the telson spine would be capable of stinging prey in between the front legs.

During swimming, the prosomal legs (appendages IV and V) were probably positioned backwards to produce minor lateral strokes.

The two heavy and specialized frontal appendages, held above the bottom, would balance the weight of the long abdomen.

The male could then attach itself to the lateral corners of the last prosomal segment, and direct its long genital appendage to the point where the eggs were stored by the female.

With its slender and spineless walking legs and short genital appendage, Erettopterus could not have produced the tracks, though they match the size and morphology of M. kiaeri rather well.

The great morphological similarities as well as the relative abundance of M. kiaeri in the region prompted Hanken and Størmer (1975)[4] to refer the tracks to Mixopterus.