The genus Nuia from lowermost Ordovician strata of the Bliss Formation and lower El Paso Group, New Mexico (USA)

In New Mexico, Nuia is an abundant constituent of the Hitt Canyon Formation of the Lower Ordovician El Paso Group in the Mud Springs Mountains and also occurs as low stratigraphically as the uppermost part of the Bliss Formation in the Caballo Mountains. Additional arguments are provided to prove that Nuia is an organism, probably a cyanobacteria, and possibly a rivulariacean. Nuia of New Mexico are probably among the oldest representatives of this genus, because it does not have the Late Cambrian-Middle Ordovician distribution previously suggested, but a range limited to the Early Ordovician. The palaeobiogeography of Nuia in the southern North American craton (Sonora, Chihuahua, New Mexico and Texas) is more precisely reconstructed, as is the initial location of the Precordillera terrane (western Argentina) as part of the southeastern margin of Laurentia