Research Training Program

Heather McCarren
Ohio State University
Columbus, Ohio

Dr. Brian Huber, Ph.D.
Supervising Scientist
Department of Paleobiology

"Before my research here at the National Museum of Natural History, I could never have imagined feeling so at home working in the Cushman room. This experience has truly been an honor and a privilege."

Phylogeny and depth ecology of Late Cretaceous planktonic foraminifer species of Globigerinelloides

At least eight species of foraminifera, a group of marine protists that comprise an important part of the fossil record, in the genus Globigerinelloides (G. multispinus, G. prairiehillensis, G. messinae, G. subcarinatus, G. volutus, G. alvarezi, G. aspensis, and G. impensus) are frequently identified in various studies of Late Cretaceous marine sediments, but opinions vary as to which of these species names are accurate and should be retained. In an effort to stabilize the taxonomy, or naming, of this group, primary type specimens of most of these species were compared with Globigerinelloides morphotypes from ODP Site 690 (Weddell Sea), DSDP, Sites 463 and 465 (tropical Pacific), and DSDP Site 511 (Falkland Plateau). Morphometric data, coiling metrics, and shape analysis based on high-resolution x-ray images from umbilical and edge views were extremely useful in characterizing population variability for each of these planispirally coiled morphotypes. Results indicate that Late Cretaceous Globigerinelloides include two distinct lineages, one with 10 to 15 chambers and the other with 20 to 25 chambers in adult specimens. Identification has been made of what may represent a new species from this latter group, which will be described at a later date. Differences in chamber shape, chamber size increase rates, and external shell ornamentation are used to delineate species populations within these two lineage groups. Stable isotope analyses of the biometrically differentiated Globigerinelloides taxa will be obtained to determine their relative depth ecologies. Earlier Globigerinelloides taxa will be similarly analyzed to reconstruct their Late Cretaceous evolutionary history.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates program, Award Number DBI 9820303.

Letter of Gratitude