Acta Zoologica Cracoviensia, 31() 1988
Lower vertebrates from the Golden Valley Formation, Early Eocene of North Dakota (U.S.A.)
Abstract:
The Wasatchian (early Eocene) lower vertebrate fauna from the Golden Valley Formation (Stark County, North Dakota, U.S.A.) includes the fishes Amia fragosa, A. uintaensis (Amiidae), Atractosteus occidentalis (Lepisosteidae), and Teleostei indet., unidentified anurans, and the salamanders Batrachosauroides gotoi (Batrachosauroididae) and Chrysoriton tiheni (Dicamptodontidae). The latter species has an elongated, aquatic body, forming the first such adaptation recorded for the Ambystomatoidea. Reptiles include the turtles Baptemys tricarinata (Dermatemydidae), Echmatemys testudinea (Emydidae) and Plastomenus sp. (Trionychidae), the lizards cf. Xestops sp. (Anguidae), ?Glyptosaurinae, and Saniwa, cf. S. ensidens (Varanidae), and the crocodilians Chrysochampsa mlynarskii gen. sp. n., Allognathosuchus sp. (Alligatoridae), and Crocodylidae indet. Chrysochampsa mlynarskii gen. sp. n. resembles most closely such species as Alligator prenasalis from the North American Oligocene, but it also has some resemblances to extant Alligator and the caimans. The lower vertebrates from the Golden Valley Formation represent a segment of the midcontinental fauna of North America that persisted from at least Late Cretaceous through the Wasatchian. However, except for the fishes, there is little generic similarity between the Golden Valley lower vertebrates and those from the Paleocene and Cretaceous. The assemblage includes primarily aquatic or riparian forms.
