Oardasaurus (meaning "Oarda de Jos lizard") is an extinct genus of lizard from the latest Cretaceous of Romania. It is a member of the Barbatteiidae, a group of lizards closely related to the Teiidae. At 20 centimetres (7.9 in) in length, it was much smaller than the only other named member of the Barbatteiidae, Barbatteius, which lived slightly later. Like Barbatteius, Oardasaurus can be identified by the presence of a crust of bone deposits, or osteoderms, on the roof of its skull; it differs from Barbatteius in the pattern of the sculpturing on this crust. Both Oardasaurus and Barbatteius lived in the isolated island ecosystem of Hațeg Island, having rapidly diversified into various generalist predators of small prey after their arrival on the island during the Early Cretaceous. They went extinct in the Cretaceous–Paleogene extinction event.
Description Oardasaurus is a small lizard, measuring roughly 20 cm (7.9 in) long. It is smaller than its close relative Barbatteius, which measures up to 80 cm (31 in) long. Like the teiioids Meyasaurus and Pedrerasaurus, the teeth of Oardasaurus are heterodont (i.e. having several types) but are consistently bicuspid (i.e. bearing two cusps), with the rear cusp being larger. The teeth probably underwent replacement. Unlike modern Teiidae, there are no crushing teeth in the back of the jaw. Among lizards, Oardasaurus and Barbatteius are unique in that their temporal muscles originate from attachments on the upper portions of their parietal bones; and in that their upper temporal fenestrae are not obscured by either the postorbital bones or the postfrontal bones. A characteristic of the family Barbatteiidae, which Oardasaurus and Barbatteius belong to, is the presence of an extensive crust of osteoderms, separated by deep grooves, on the bones of the skull roof (including the parietals, postorbitals, and frontals, with the latter having a slightly different arrangement). These osteoderms preserve the imprints (collectively known as the "pileus") of the scales that laid over them. In modern Teiidae, the arrangement of the pileus (which is present directly on the skull roof due to an absent or limited osteoderm crust) varies between species, while it is fairly constant in modern Lacertidae. In Oardasaurus, the occipital (rear) scale of the pileus is subdivided into three smaller osteoderms in Oardasaurus, unlike Barbatteius, Meyasaurus, and the lacertid Plesiolacerta where there is no such division. The variable division in Barbetteiidae may be transitional between teiids and lacertids. In Oardasaurus, the frontal bones are completely fused, and the suture between the frontal and parietal is straight but has a jagged margin. They are also fused in Barbatteius and adult Meyasaurus, but they remain unfused in Pedrerasaurus and young Meyasaurus. Additionally, the margin where each frontal borders the eye socket is markedly concave in Oardasaurus. On the bottom part of the rear of each frontal, there is a small triangular depression, located just behind the crest known as crista cranii frontalis. These depressions are probably where "lappets" from the parietals inserted, much like Barabetteius and Meyasaurus.
Discovery and naming Fossil remains of Oardasaurus were found in the site of Oarda de Jos A (ODA), which is located near the village of Oarda de Jos in southern Transylvania, Romania, 3 km (1.9 mi) south of Alba Iulia on the eastern shore of the Sebeș River. The site consists of Cretaceous continental deposits, belonging to the early Maastrichtian Șard Formation, exposed as a slope 50 m (160 ft) long and 17–19 m (56–62 ft) high. Grey-black silt clays form much of the deposits. From 2008 to 2015, about 2.8 tonnes (3.1 short tons) of sediment were screen-washed at the site; the remains of Oardasaurus were among the specimens found. The type specimen of Oardasaurus, an incomplete parietal bone, is stored at the Palaeontological Laboratory of the Palaeontology-Stratigraphy Museum of Babeș-Bolyai University (PSMUBB) in Cluj-Napoca, Romania, under the specimen number PSMUBB.ODAN-A-12. Additional specimens, all stored at the PSMUBB, include PSMUBB.ODAN-A-13, a fragment from a parietal bone; PSMUBB.ODAN-A-18, a mostly complete but flattened postorbital bone; PSMUBB.ODAN-A-15 (also known as ODAN-Lizard 4), -16, -17, and -23, all fused frontal bones; PSMUBB.ODAN-A-19 (or ODAN-Amf-8), -20, and -21, all incomplete maxillae. The frontal bones belong to three different size classes, with -15 being largest, -16 and -17 being intermediate, and -23 being smallest. In 2017, Oardasaurus was named as a new genus by Vlad Codrea, Márton Venczel, and Alexandru Solomon in a research paper. They named the genus after the village of Oarda de Jos, combined with the suffix -saurus, which means "lizard". One species was assigned to this genus by Codrea and colleagues, O. glyphis. Glyphis is derived from the Greek glyphe, meaning "carving". For their research paper, Codrea and colleagues used a scanning electron microscope at the Royal Belgian Institute of Natural Sciences in Brussels, Belgium to photograph the parietal, frontal, and maxilla.
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