Mecistotrachelos is known from several fossil specimens excavated from the Solite quarry from the Cow Branch Formation on the Virginia-North Carolina border.

The first fossil, VMNH 3649, is the holotype of the genus and is preserved completely articulated, although missing the tail, hindlimbs, and most of the pelvic girdle.

[2] The Solite quarry was once a large lake and surrounding wetland which formed in a rift basin when Pangaea started to break up during the Late Triassic.

The quarry's sediments were initially believed to have formed during the Carnian stage of the Triassic, about 230 million years ago.

[3][2] More recent magnetostratigraphy of the Cow Branch Formation supports a younger age in the middle Norian, closer to 220 million years ago.

[2] The skull is lightly built and pointed, and there is some evidence for holes in the back of the head, indicating that the animal was a diapsid reptile.

The manus (hand) had five fingers while the pes (foot) had short metatarsals and an indeterminate number of toes which seemed to have hooked inwards, at least in VMNH 3650.

In addition, the flexible hind limbs with "hooked" toes preserved in VMNH 3650 indicate that it was well-adapted for an arboreal habitat.

[2] Unlike in kuehneosaurids, which had downward-curving "wings", the ribs of Mecistotrachelos were mostly straight, and were not naturally cambered to create an airfoil.

In this case they would function as a pteroid bone in pterosaurs or an alula in birds, increasing or decreasing drag depending on their position.

[7] The only other Triassic rib-gliding reptiles were the kuehneosaurids, which are usually interpreted as lepidosauromorphs distantly related to rhynchocephalians (such as the tuatara) and squamates (such as lizards and snakes).