HEMICYCLAMMINA WHITEI (HENSON, 1948): THE SENIOR SYNONYM OF HEMICYCLAMMINA SIGALI MAYNC 1953, A DISTINCTIVE LARGER BENTHONIC FORAMINIFER FROM THE MID-CRETACEOUS OF NEOTETHYS

Abstract

In 1953 Wolf Maync introduced the lituolid (now regarded as loftusiid) foraminiferal genus Hemicyclammina, with its type species Hemicyclammina sigali from the Cenomanian of Algeria. Since then, this distinctive microfossil has been frequently reported from mainly Neotethyan mid-Cretaceous (mostly Albian and Cenomanian) sedimentary rocks in locations as far apart as Brazil and Oman. However, Maync was seemingly unaware of the 1948 publication of Francis R.S. Henson in which a new species of foraminifera, Cyclammina whitei, was described from the mid-Cretaceous of the Middle East. During the course of the last 70 years, C. whitei has been placed in the genus Hemicyclammina, tenuously regarded as distinct from H. sigali. We demonstrate that H. whitei and H. sigali are synonyms, with H. whitei the senior synonym, and hence the type species of Hemicyclammina. This argument is supported by the re-illustration of the type material of H. whitei and H. sigali. It is also argued that a number of poorly known taxa (e.g., Hemicyclammina evoluta Hamaoui, Ismailia neumannae El-Dakkak, Sinainella aegyptiaca El-Dakkak) are most likely the junior synonyms of H. whitei and that thus, for the Albian – Cenomanian at least, there is only one species of Hemicyclammina. Limited Barremian/Aptian records of Hemicyclammina are probably best assigned to a potentially ancestral form herein termed “Hemicyclammina? sp.” pending access to further material and a full assessment of the evolution of Hemicyclammina. A critical review of the many published records demonstrates that H. whitei ranges throughout the Albian and Ceno-manian, although locally it may have a more restricted range because of facies control on its inception, extinction, and abundance. It is confidently known to occur from southern and central America, North Africa, the Mediterranean, the Arabian Plate and Somalia.