Kadimakara australiensis

The rear of the skull, as shown by the holotype specimen, preserves several bones of the skull roof, most notably the parietal bones which form the upper surface of the skull past the level of the eyes. These paired bones were boxy in shape and contacted each other at the midline of the skull. In the middle of their suture (line of contact) was a hole known as a pineal foramen, which in some modern reptiles contains a sensory structure colloquially known as a "third eye". Immediately behind this hole was a rectangular lowered area of bone, known as a median fossa. This median fossa is the main feature which can be used to differentiate Kadimakara from its close relative Prolacerta, which either lacks this specific lowered area or has the entire rear part of the skull slightly lowered, depending on the individual. Directly above the eyes were a pair of bones known as frontals; only a small portion of these bones were preserved in the Kadimakara holotype. However, the preserved portion can be seen to stretch along the outer edges of the parietal bones. This means that the parietals had a wedge-like shape when seen from above, and that they stretched forward as far as the level of the orbits. Kadimakara also lacks postparietals, additional bones which form out of the rear part of the parietals in many different types of archosauromorphs. All of these parietal features are also shared by Prolacerta, and their presence (or lack thereof) links Kadimakara with that genus in the family Prolacertidae.[2] A small, wedge-like bone known as a postfrontal formed the upper rear corner of the orbit (eye hole).[1]

The outer edge of each parietal bone contacts a large hole on each side of the skull roof. These holes are known as supratemporal fenestrae. The outer edge of each hole was formed by a multi-pronged bone, although the identity of this bone has been controversial. The original describer of Kadimakara, Alan Bartholomai, considered it a postorbital bone which forms the rear edge of an unusually elongated orbit. In 2016, Martin Ezcurra reinterpreted the bone as a complex forward extension of the squamosal bone. This reinterpretation means that the orbit had a rounder and much less unusual shape than that of Bartholomai's original reconstruction, as the actual postorbital bone was positioned further forward on the skull. Unfortunately, the postorbital is mostly lost, with only a small sliver of bone still present in the specimen. Nevertheless, this postorbital sliver can be seen to contact a supratemporal fenestra, omitting the preserved postfrontal bone from contact with the hole.[2]

This reinterpretation has several implications for bone identifications in the rest of the skull. The ventral process (lower branch) of the squamosal, which extends onto the cheek region of the skull, contacts a smaller crescent-shaped bone near the jaw joint. Under Bartholomai's interpretation, this bone was a fragment of the jugal (cheek bone), but Ezcurra reinterpreted it as a strap-like quadratojugal bone, which was near the jaw joint.[2] Regardless of these interpretations, the rear branch of the jugal would not have been long enough to enclose the lower temporal fenestra. The lower temporal fenestra (also known as the infratemporal fenestra) was typically a large hole on the side of the skull, although it was not completely enclosed from below in many lepidosaurs (the group of reptiles containing lizards, snakes, and the tuatara) and a few archosauromorphs (such as Prolacerta and Kadimakara). In these reptiles, the lower temporal fenestra attained an arch-like shape. The Kadimakara holotype has also preserved fragments of the braincase and the rear part of the palate. The rear part of the shallow lower jaw was also preserved.[1]

As this specimen is not definitively proven to belong to Kadimakara, many of its features may not necessarily apply to the genus. However, its referral to Kadimakara is likely legitimate due to the fact that the snout bones closely resemble those of Prolacerta. The maxilla (the main toothed bone of the snout) was covered in shallow longitudinal furrows but otherwise had a conventional design, with a large main body and a wedge-like prong extending backwards to contact the jugal bone. Several teeth have also been preserved attached to the maxilla. These teeth are sharp, curved, and flattened from the side, indicating that Kadimakara was a carnivorous reptile. The teeth are set in deep sockets and fused to the bone in several areas. The rear edge of the maxilla clearly connects to a smaller bone known as a lacrimal, which forms the front edge of the orbit. The upper side of the snout was formed by a pair of large bones known as nasals which presumably contacted the frontals in an area which has not been preserved. The middle part of the shallow lower jaw was also preserved, including teeth similar to those of the maxilla.[1]