The
holotype,
AM F125866, a skull and partial skeleton, originated from the
Kincumber Quarry, where the
Terrigal Formation is present. In October 1996, Mihail Mihaildis, a retired
chicken farmer, purchased a large slab weighing roughly for use in the construction of a garden
retaining wall at his private property in
Umina Beach,
New South Wales. While landscaper David King was cleaning the rocks, he discovered the holotype specimen of
Arenaerpeton supinatus. The holotype specimen was found in to of surrounding
quartz-rich
sandstone. Shortly after, Mihaildis contacted the
Australian Museum,
Sydney about the discovery and in 1997, it was put on display at the "Dinosaur World Tour", a Canadian touring exhibition, which was showing in Sydney at the time. One of the describers of the specimen, Lachlan Hart, saw the specimen while it was on display in 1997 at the age of twelve. The fossil was eventually donated to the Australian Museum in 2000. In , shortly before it was described, the holotype was taken to the facilities of the
Australian Border Force so a more complete view of the skeleton could be seen by using X-ray scanners normally reserved for the inspection of
cargo. Despite this, there was insufficient difference in
X-ray attenuation between the fossil and the surrounding matrix, possibly due to the similar density between the
quartz and the
apatite of the
fossil, or due to the low quantity of surviving
bone.
Arenaerpeton supinatus was then named and described by Hart et al. (2023). == Description ==