Abstract
The extant venomous Gila monster and beaded lizards, species of Heloderma, live today in southwestern USA and south along the Pacific coastal region into Central America, but their fossil history is poorly understood. Here we report helodermatid osteoderms (dermal ossicles) from the late Miocene-early Pliocene Gray Fossil Site, eastern Tennessee USA. Twenty-three species of mammals are known from the fauna including abundant Tapirus polkensis, as well as fishes, anurans, salamanders, turtles, Alligator, birds, and snakes. Beaded lizards belong to the Monstersauria, a clade that includes Primaderma + Paraderma + Gobiderma + Helodermatidae (Estesia, Eurheloderma, Lowesaurus, and Heloderma). Osteoderms of lizards in this clade are unique within Squamata; they typically are circular to polygonal in outline, domed to flat-domed in cross-section, have a vermiculate surface texture, are not compound structures, and do not have imbricate surfaces as on many scincomorph and anguid lizards. We review and characteri...
Highlights
Twenty−three species of mammals are known from the fauna including abundant Tapirus polkensis, as well as fishes, anurans, salamanders, turtles, Alligator, birds, and snakes
Beaded lizards belong to the Monstersauria, a clade that includes Primaderma + Paraderma + Gobiderma + Helodermatidae (Estesia, Eurheloderma, Lowesaurus, and Heloderma)
Osteoderms of lizards in this clade are unique within Squamata; they typically are circular to polygonal in outline, domed to flat−domed in cross−section, have a vermiculate surface texture, are not compound structures, and do not have imbricate surfaces as on many scincomorph and anguid lizards
Summary
The extant venomous Gila monster and beaded lizards, species of Heloderma, live today in southwestern USA and south along the Pacific coastal region into Central America, but their fossil history is poorly understood. We report helodermatid osteoderms (dermal ossicles) from the late Miocene–early Pliocene Gray Fossil Site, eastern Tennessee USA.
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