|Morohasaurus kamitakiensis |
Ikeda, Ota, Tanaka, Ikuno, Kubota, Tanaka & Saegusa, 2022
• We report a nearly complete left dentary of lizard from the Lower Cretaceous Sasayama Group, Japan.
• The material was described as a new monstersaur taxon “Morohasaurus kamitakiensis”.
• The new taxon might possibly be the oldest representative of the Monstersauria in the world.
• The present finding endorses the high taxonomic and ecological diversity of the Early Cretaceous lizard assemblage in Japan.
A nearly complete left dentary of a lizard was excavated from the Lower Cretaceous Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan. The specimen shows several characters, which suggest its allocation in Monstersauria of the superfamily Varanoidea (Squamata: Anguimorpha). However, the specimen exhibits obvious differences from the known members of the whole Varanoidea. Thus, the specimen is described as a new taxon of cf. Monstersauria, Morohasaurus kamitakiensis gen. et sp. nov.. This new species is characterized by a suit of unique features, such as the sinuous posteroventral rim of the dentary with a large U-shaped upper notch and small V-shaped lower notch, posteroventral corner of intramandibular septum with a weakly pointed eminence projecting posteriorly, and unicuspid, curved trenchant teeth with distinct blade-like carinae on their mesial and distal sides without grooves or serrations. Morohasaurus kamitakiensis might possibly be the oldest representative of the Monstersauria.
Keywords: Monstersauria, Japan, Lower Cretaceous, Ohyamashimo Formation, Oldest representative
Tadahiro Ikeda, Hidetoshi Ota, Tomonori Tanaka, Kenji Ikuno, Katsuhiro Kubota, Kohei Tanaka and Haruo Saegusa. 2022. A Fossil Monstersauria (Squamata: Anguimorpha) from the Lower Cretaceous Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan. Cretaceous Research. 130, 105063. DOI: 10.1016/j.cretres.2021.105063 hitohaku.jp