Fusulinid wall structure in the Profusulinella-fusulinella evolutionary transition
Bulletins of American Paleontology
The evolutionary transition from Profusulinella regia to Fusulinella llanoensis is preserved in a 15-m interval of the Marble Falls Limestone in central Texas. This transition was accomplished by the progressive development of internal epithecal deposits. By definition, the epitheca in Profusulinella is secreted only on the floors of chambers and septa. In Fusulinella, the epitheca is secreted also on the ceilings of chambers so that it lines the entire chamber cavity. Intermediate populations from the transition interval, assigned to F. primaeva, include specimens with profusulinellid walls as well as those in which fusulinellid wall structure is incompletely developed. The Profusulinella-Fusulinella evolutionary transition also occurred independently, and at about the same time, in geographically disjunct populations in what are presently Europe (P. ex gr. pseudorhomboides-F. ex gr. subpulchra lineage) and southeast Asia (P. prisca timanica-Fusulinella n. sp. lineage). Accordingly, the genus Fusulinella is regarded as polyphyletic, with its multiple origins being the result of synchronous parallelism. The stratigraphic appearance of Fusulinella characterizes the bases of the informal upper Atokan Series in North America, the upper Kashirian Substage in western Eurasia, the Akiyoshian Series in Japan, and the upper Dalan Stage in South China. If these levels are roughly age equivalent, as is widely accepted, then the rapid global dispersal of early Fusulinella spp. from their original loci most likely occurred during an interglacial highstand that allowed interchange among otherwise separate faunal realms.
Original Publication Date
Groves, John R., "Fusulinid wall structure in the Profusulinella-fusulinella evolutionary transition" (2005). Faculty Publications. 2916.