Flabellum fresnoense Durham, 1943

Baron-Szabo, Rosemarie C., 2008, Dendrophylliina, Caryophylliina, Fungiina, Microsolenina, and Stylinina, Zootaxa 1952, pp. 1-244 : 90

? Flabellum fresnoense Durham, 1943

Pl. 8, figs 2a, b

v1943 Flabellum fresnoense Durham , n. sp.: Durham, p. 197, pl. 32, figs 2–3.

2000 Flabellum fresnoense, Durham 1943 : Löser, p. 36.

Dimensions. d=5.7 x 7.9 mm; d (min)/d (max)=0.5–0.72; s=16+s3; h (broken specimen)=7.4 mm.

Description. Solitary, trochoid-subcylindrical; slightly flattened in outline; costosepta arranged in 2 cycles with the beginning of a third cycle in 8 systems; 16 septa reach the axial region.

Remarks. The holotype of the species Flabellum fresnoense represents a small juvenile fragmented specimen which leaves unanswered questions regarding its septal development and expected habitus of the adult corallum. As shown in recent studies on the ontogenetical developments in solitary forms of the Upper Cretaceous, like e.g., Aulosmilia and Flabellosmilia (Baron-Szabo 2003) , the septal arrangement can vary significantly during ontogeny in that changes from septal developments in cycles to arrangements in size orders often occur in these genera. In the present case the septal apparatus might not necessarily be arranged in cycles (here in 8 systems) but could very well represent a development in two with the beginning of a third size order. Moreover, the holotype of Flabellum fresnoense very closely resembles juvenile stages of Flabellosmilia (see e.g., Baron-Szabo 2003, pl. 17, fig. 1). While one significant feature of the latter genus is its diamond-shape (in cross view), in its juvenile stages however, it often shows rather flabellate to elliptical outlines. The diamond-shape often develops in later ontogenetical stages in that the corallum increasingly becomes more flabellate and at the same time the septa that are positioned in the central area of the corallum (meaning perpendicular to the distant edges of the corallum) become more dominant in length, widening the corallum in these places. In Flabellum fresnoense such a feature might be displayed. In addition, in having reduced costae, the form shows a feature that is characteristic of the genus Flabellosmilia .

Type location of species. Paleocene of the USA (California, Fresno County, Lodo Formation , Cheney Well #1) .

Distribution. Paleocene of the USA (California, Fresno County, Lodo Formation, Cheney Well #1).