Published online by Cambridge University Press: 14 July 2015
The rhynchonellid genus Ptilorhynchia Crickmay and the terebratulid genus Sellithyris Middlemiss are described from Mexico for the first time. This is the first formal description of Sellithyris from the American Continent. Ptilorhynchia (Proteorhynchia) imlayi n. sp. is described from the late Aptian of the La Penã Formation, Coahuila. “Rhynchonella’ durangensis Imlay from the Valanginian of the Carbonera Formation, Durango, is assigned to Ptilorhynchia (Proteorhynchia). “Terebratula’ coahuilensis Imlay from the Valanginian Barril Viejo Formation, Coahuila, is referred to Sellithyris. Sellithyris coahuilensis indicates close links with contemporaneous Valanginian faunas of southern Europe. During the early Early Cretaceous Sellithyris had a fairly restricted latitudinal and broad longitudinal distribution (Tethys and its extension across the opening Central Atlantic Ocean). Ptilorhynchia (Proteorhynchia) in Mexico is significant as the first low-latitude record for Ptilorhynchia. Other Lower Cretaceous records are from northern and southern high latitudes, previously interpreted as a bipolar distribution. It is suggested that Ptilorhynchia had a Boreal-East Pacific distribution with Ptilorhynchia (Proteorhynchia) being a low-latitude Early Cretaceous offshoot. The genus may prove to be pandemic. Proteorhynchia Owen is regarded as a subgenus of Ptilorhynchia.