Scutifolium jordanicumgen. et sp. nov. (Cabombaceae), an aquatic fossil plant from the Lower Cretaceous of Jordan, and the relationships of related leaf fossils to living genera

Abstract

A new species of aquatic plant, Scutifolium jordanicum gen. et sp. nov., Taylor, Brenner & Basha, is described from the Albian of Jordan. The leaves are microphyllous with a symmetrical, elliptical to suborbiculate shape, convex to rounded apex and base, and actinodromous to palinactinodromous primary venation. The peltate, centrally attached petioles are narrow, elongate, and alternately arranged on similarly sized stems. The leaves appear to be thick and have aerenchyma. Comparisons to plants with centrally peltate leaves and palmate venation and to aquatic plants with floating leaves suggest that S. jordanicum belongs to the Cabombaceae lineage within the Nymphaeales. Cladistic analysis including the fossil and living members of the Nymphaeales shows that the S. jordanicum is basal to the living members of the family and has unique characters not found in any living genera. This is the oldest evidence of the Cabombaceae from the Old World. Inclusion of two other Early Cretaceous peltate leaf fossils in the phylogenetic analysis indicates their affinities to Cabombaceae and that some of the shared derived characters for the living members are progressively acquired in the fossils. These data show the Cabombaceae were widespread in Gondwana and Laurasia by the mid-Cretaceous.

Integrating Early Cretaceous Fossils into the Phylogeny of Living Angiosperms: ANITA Lines and Relatives of Chloranthaceae

“…Thus, recognition of crown group fossils in the Aptian-Albian indirectly implies that these were aquatic plants, and this is confirmed by the vegetative morphology of Pluricarpellatia, Scutifolium, and Brasenites (Wang and Dilcher 2006;Taylor et al 2008;Friis et al 2011). …”

“…This was also noted by Taylor et al (2008), who concluded that Pluricarpellatia and Scutifolium were related to Cabombaceae, and by Friis et al (2011). Characters of the best-understood fossil, Monetianthus, do not make sense for a stem relative of Nymphaeales, since the most recent common ancestor of the order can be reconstructed as having hypogynous flowers and a smaller number of free carpels containing one ovule each (Endress and Doyle 2009).…”

“…Mohr et al (2008) discussed similarities and differences between Pluricarpellatia and Nelumbites, but they confused the picture by referring to Nelumbites as nymphaealean and not mentioning the evidence that it was related to Nelumbo. However, there are other peltate leaves in the Albian of Jordan (Scutifolium; Taylor et al 2008) and Kansas (Brasenites; Wang and Dilcher 2006) that are more like Brasenia than Nelumbo and Nelumbites in tending to be longer than wide, rather than round or wider than long, and in other characters used by Taylor et al (2008).…”

“…Whereas there is no direct evidence on the ecology of Monetianthus and Carpestella, the vegetative morphology of Pluricarpellatia, with rhizomes bearing roots, leaves with long petioles, and flowers with long pedicels, clearly indicates an aquatic habit, consistent with the lacustrine origin of the sediments. Using a data set of vegetative characters only (Taylor 2008), Mohr et al (2008) and Taylor et al (2008) found two most parsimonious positions for Pluricarpellatia, depending on how they scored the leaves, which they described as varying between eccentrically and centrally peltate: sister to Cabombaceae when the leaves were scored as centrally peltate but sister to Nymphaeales as a whole (not including Trithuria) when the leaves were scored as eccentrically peltate. However, Taylor (2008) used the term "peltate" to describe attachment of the petiole to the plane of the blade at a high angle (D. W. Taylor, personal communication, 2012), rather than in the well-established sense of extension of the blade around the adaxial side of the petiole.…”

Arcellites punctatus sp. nov.: a new megaspore from the Early Cretaceous of Portugal studied using high resolution synchrotron radiation X-ray tomographic microscopy (SRXTM)

“…There is also evidence for major changes in fresh water ecosystems during the same period. An early invasion of angiosperms into the aquatic realm is indicated by several whole plant occurrences (Sun et al 2002;Friis et al 2003;Mohr et al 2008), isolated Brasenia-like floating leaves (Saporta 1894;Taylor et al 2008), and flowers and seeds related to the Nymphaeales (Friis et al 2009(Friis et al , 2011. Heterosporangiate ferns with inferred aquatic habit also became established and proliferated markedly during the Early Cretaceous (e.g.…”