Aspidostemon

Abstract: Introduction The increasing number of fossil angiosperm reproductive structures described from Cretaceous strata (e.g. Friis et al., 2006) has provided a wealth of new data for understanding aspects of early flowering-plant evolution. In particular, flowers retrieved from many newly discovered mesofossil floras are often three-dimensionally preserved, which permits detailed morphological and systematic analyses. They have thereby provided information on the phylogenetic diversity and reproductive biology of Cretaceous angiosperms (e.g. Friis et al., 2006, 2010). However, an important feature of the angiosperm fossil record from the Cretaceous is that many fossils, particularly from the Early Cretaceous, cannot readily be accommodated in living taxa at the family or genus level, either because they are too poorly preserved to show the diagnostic features needed for secure systematic placement, or because they show a mosaic of features found in several living groups, indicating that they represent extinct lineages on internal branches of the angiosperm phylogenetic tree. The focus of this paper is on two early fossils of the second kind. While their relationships to extant Laurales are secure, they show features indicating that they fall outside the circumscription of extant families in the order. Studies of relationships among living angiosperms based on analyses of DNA sequences support the recognition of the Laurales as a monophyletic group of seven extant families (Calycanthaceae, Siparunaceae, Gomortegaceae, Atherospermataceae, Hernandiaceae, Monimiaceae, Lauraceae; Renner, 1999, 2005; Renner and Chanderbali, 2000). The Laurales are the sister group to Magnoliales and include between 2840 and 3340 species in about 92 genera (Renner, 2005). The Calycanthaceae are the well-supported sister group to the remainder of the order, the core Laurales (Fig 3.1), within which Atherospermataceae, Gomortegaceae and Siparunaceae also form a well-supported clade (e.g. Renner, 1999, 2005). Relationships among Lauraceae, Monimiaceae and Hernandiaceae are currently not settled securely (Renner and Chanderbali, 2000). Morphological data strongly support a sister relationship of Hernandiaceae and Lauraceae (e.g. Doyle and Endress, 2000; Endress and Doyle, 2009), as do some molecular analyses (e.g. Qiu et al., 1999, 2006). However, in other molecular analyses the pattern of relationships among these three families is not well resolved (e.g. Renner, 1999, 2005; Chanderbali et al., 2001; Soltis et al., 2007).

Abstract: Le genre Aspidostemon (Lauraceae), endemique de Madagascar, est revise. Il est caracterise par des feuilles opposees, des fleurs avec trois ou six etamines bi-loculaires et un fruit completement renferme dans un hypanthium elargi et surmonte par des pieces florales persistantes. Ce genre, decrit en 1987 par Rohwer & Richter avec 11 especes, totalise, dans la presente revision, 28 especes dont 18 sont nouvellement decrites, une est transferee depuis le genre Cryptocarya, une espece est exclue d'Aspidostemon et une autre est consideree comme incompletement connue car son specimen type est sterile.

Abstract: The southem African tree, Dahlgrenodendron natalense, previously ascribed to the genus Beilschmiedia was recently segregated as a monotypic genus, Dahlgrenodendron, on account of its distinctive exomorphology, palynology and fruit structure. Dahlgrenodendron differs from Beilschmiedia in nearly all quantitative and qualitative features of wood and bark anatomy. The overall structural pattern of these tissues does not support the initial assignment of Dahlgrenodendron to the tribe Cryptocaryeae, nor does it fit any other lauraceous taxon. Within Lauraceae, an isolated non-aligned status is provisionally proposed for the genus.