Icacinaceae from the Eocene of western North America

Abstract

These fossils increase our knowledge of Icacinaceae in the Paleogene of North America and highlight the importance of the Northern Hemisphere in the early diversification of the family. They also document interchange with the Eocene flora of Europe and biogeographic connections with modern floras of Africa and Asia, where Icacinaceae are diverse today. The present-day restriction of this family to tropical regions offers ecological implications for the Eocene floras in which they occur.

Revision of Icacinaceae from the Early Eocene London Clay flora based on X-ray micro-CT

“…: Stull et al 2015). However, some of the major clades within the family in its strict sense can be diagnosed using fruit morphological characters (Table 2), such as the ornamentation pattern on the endocarp surface (e.g., the presence of pits, ridges, or rugosities); the presence and morphology of projections into the locule cavity; the position (either inside or outside the endocarp wall) of the primary vascular bundle, which is referred to as the funicle in older literature (e.g., Reid and Chandler 1933); the configuration of apical apertures; and the presence of papillae lining the inner endocarp wall (Reid and Chandler 1933;Manchester 1994;Kvaček and Bůžek 1995;Stull et al , 2015Allen et al 2015). The seeds also generally have a slight vertical indentation on one lateral face, bearing the raphe.…”

“…The extant species examined are listed in Appendix B. The London Clay Collinson et al 2012) and North America (e.g., Manchester 1994;Tiffney 1999;Pigg et al 2008;Rankin et al 2008;Stull et al 2011Allen et al 2015) through original observations or reference to the literature. The examination and description of the London Clay material focuses primarily on previously undocumented characters (e.g., certain internal structural features, such as the position of the vascular bundle) as revealed by micro-CT imaging, to complement the original observations of Reid and Chandler (1933).…”

“…Subsequently, Kvaček and Bůžek (1995) established the fossil genus Palaeohosiea to accommodate a new species, P. suleticensis, as well as the two "Hosiea" species mentioned above, under the new combinations, P. bilinica (including the fossils previously named Natsiatum eocenicum) and P. marchiaca. However, as noted by Allen et al (2015), the diagnosis of Palaeohosiea contains no significant distinctions from the extant genus Iodes and, therefore, the various fossils included in the "Palaeohosiea complex" likely represent this genus.…”

“…New combinations are established for three species from the flora, several of which have important nomenclatural consequences for other fossils of Icacinaceae from North America (Manchester 1994;Tiffney 1999;Allen et al 2015) and Europe (Kvaček and Bůžek 1995); these are discussed herein. A new combination is also made for a species of Iodes from the Eocene of western North America with close affinities to a species from the London Clay (Iodes corniculata Reid et Chandler).…”

“…The family, in the traditional sense (Engler 1893;Howard 1940;Sleumer 1942), was grossly polyphyletic (Soltis et al 2000;Kårehed 2001), but recent phylogenetic work has greatly clarified the composition of the family and relationships within it (Byng et al 2014;Stull et al 2015). Furthermore, recent and ongoing studies of fruit morphology have highlighted characters useful for diagnosing clades within the family (e.g., Stull et al 2011Allen et al 2015).…”