Nystroemiaceae
The Nystroemiaceae are Permian gymnosperms with ovulate structures showing some apparently ancestral features more typical of early seed plants, whereas the leaves and branches show derived character states of broad-leaved gymnosperms
Ecology & Form
Stems
Branches were probably woody with variability in its branching pattern
Long and short shoots were differentiated
Leaves
Vegetative leaf with a long petiole and a broad lamina with radiate reticulate venation
Lamina with entire or undulate margin and cordate or tapering base
Reproductive Structures
Frond-like ovuliferous organ
The main axis forking with pinnate lateral branches bearing numerous small bicornute ovules at their tips.
Leafy/ovuliferous complex arising from leaf axil
Ovuliferous organs attached in the axil of the petiole of leafy organ, or both organs crowded on a node
Classification
└Nystroemiaceae †
Geologic Age
Middle - Late Permian
Nystroemia †
Halle 1929; Wang & Pfefferkorn 2010
Early - Late Permian of North China
Seed plant with multi-order branching system
Ovuliferous organ frond-like, with the main axis forking into two or more pinnate branches adaxially bearing numerous small bicornute ovules with zygomorphic symmetry
Vegetative leaf with a long petiole; lamina reniform, basally cordate or tapering, entire or slightly undulate at the margin; veins numerous, finely diverging and reticulate.
Leafy/ovuliferous complex arising from leaf axil, forming the last-order branches, which are alternative or opposite on the second-last-order axis
Ovuliferous organs attached in the axil of the petiole of leafy organ, or both organs crowded on a node.
N. reniformis
Wang et al. 2003
N. shouyangensis
Middle - Late Permian (Capitanian–Wuchiapingian) of Shouyang, Shanxi, China
Ovuliferous organ with the main axis forking into two or more pinnate-like branches adaxially bearing numerous small bicornute ovules with zygomorphic symmetry
Vegetative leaf with a long petiole; lamina reniform, basally cordate, entire or slightly undulate at the margin; veins numerous, finely diverging and reticulate
Leaves and ovuliferous organs attached to short shoots, forming the last-order branches
The most critical difference is that N. shouyangensis has leaves and ovuliferous organs arranged on a short shoot, whereas N. reniformis are arranged on a long shoot
The leaf laminae of N. shouyangensis have a very distinctly cordate base, whereas N. reniformis mostly have a wedge-shaped lamina base, although the lamina base of certain small leaves is cordate to a degree
The ovuliferous organs of N. shouyangensis as a rule appear as a main axis that distally bifurcates once, producing two subordinate pinnate branches bearing numerous small bicornute ovules, whereas N. reniformis are more irregular
Above: Nystroemia reniformis (From Fig. 4, Wang & Pfefferkorn 2010)
Above: Nystroemia shouyangensis (From Fig. 6, Wang & Pfefferkorn 2010)