Paleocene orthophragminids from the American bioprovince were studied from the Nonsuch Formation in Jamaica and the Salt Mountain Limestone in Alabama, the latter being the type locality of Discocyclina blanpiedi (Vaughan) and Discocyclina cookei (Vaughan). Species traditionally assigned to Athecocyclina Vaughan, Neodiscocyclina Caudri and Hexagonocyclina Caudri are redescribed and a new systematic classification of American orthophragminids is proposed based on the newly discovered microspheric forms of Paleocene species of Hexagonocyclina and Neodiscocyclina and Eocene Stenocyclina Caudri. Hexagonocyclina, questionably placed in Orbitoclypeidae Brönnimann in previous works, possesses an orbitoclypeid-type microspheric juvenarium justifying its placement in this family, whereas Stenocyclina and Pseudophragmina are transferred to Discocyclinidae Galloway after identifying the discocyclinid-type microspheric juvenarium. The genus Proporocyclina Vaughan & Cole is considered invalid and is assigned to Pseudophragmina. The genus Neodiscocyclina Caudri, possessing an orbitoclypeid-type juvenarium, is interpreted as a junior synonym of Orbitoclypeus Silvestri, a genus widely occurring in the Tethys. Athecocyclina has a typical discocyclinid-type microspheric juvenarium and is characterized by the development of immature radial subdivisions in the annular chambers, which never form complete septula. An evolutionary lineage for Orbitoclypeus weaveri consisting of O. weaveri blanpiedi and O. weaveri weaver is established for the first time herein. The Hexagonocyclina cristensis lineage, consisting of H. cristensis cristensis and H. cristensis meandrica, and the Athecocyclina stephensoni lineage, consisting of A. stephensoni macglameriae and A. stephensoni stephensoni, are provisionally suggested based on the morphometry and early chamber arrangement of megalospheric forms. The superposition of the two subspecies in the Orbitoclypeus weaveri lineage is shown from the Salt Mountain Limestone. http://zoobank.org/urn:lsid:zoobank.org:pub:493F043E-22D3-49CD-A427-D5159F249BD2.
- American bioprovince
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