Nymphaea sp.

Gee, Carole T., Taylor, David Winship & Rember, William C., 2022, First Water Lily, A Leaf Of Nymphaea Sp., From The Miocene Clarkia Flora, Northern Idaho, Usa: Occurrence, Taphonomic Observations, Floristic Implications, Fossil Imprint 78 (1), pp. 288-297 : 290-291

Nymphaea sp.

Text-fig. 2a, b

1991 Nuphar sp. ; Rember, table 1 on p. 52, appendix B on pp. 117, 122 (leaf not figured).

P r o v e n a n c e. Locality P-33 at the Fossil Bowl Racetrack site, 115.5 cm down from the top of the section A as measured by Rember (1991: 32, fig. 5); Idaho, USA.

S t r a t i g r a p h y. Wanapum Formation of the Columbia

River Basalt Group.

A g e. 15.78 ± 0.039 Ma, Middle Miocene (cf. Höfig et al. 2021).

R e p o s i t o r y. Clarkia fossil collections, Morrill Hall,

University of Idaho in Moscow, USA (no inventory number).

D e s c r i p t i o n. The fossil leaf is represented by a single specimen, which is oriented with its adaxial surface facing upward on the sediment surface ( Text-fig. 2a, b ). It has the eccentric peltate petiole attachment typical of many aquatic leaves. A dark spot on the adaxial side of the lamina represents the point of petiole insertion on the abaxial side of the leaf. The petiole insertion point is dark, robust, and located about 1 mm distal to the basalmost leaf margin. The petiole itself is not visible, because it is presumably attached at an angle to the abaxial side of the leaf lamina.

Using the morphological characters and character states given by the Leaf Architecture Working Group (1999) and Ellis et al. (2009), the fossil specimen can be described as follows. The leaf is simple and has an entire margin without any undulations. The leaf measures 3.8 cm in maximal length, from leaf apex to the end of basal lobe, and 3.2 cm in maximal width at its widest point which is about 2.3 cm from the leaf apex. Hence, the leaf laminar area defines a microphyll, with a laminar length/width ratio of 1.2, and leaf shape is widely ovate in general outline. Leaf apex angle is obtuse, while the leaf apex shape is rounded. Leaf base angle is acute, and leaf base shape is cordate, whereby the leaf base is embayed in a narrow sinus with extremely straight margins until it curves at the end of the lobes. The leaf sinus between the basal lobes is deep, measuring 1.2 cm or 30 % of leaf length.

The venation on the lamina is visible only near the base of the leaf. The primary vein category is basal actinodromous, with at least three lateral primaries radiating from the petiolar insertion point on either side of the slightly thicker medial primary vein. The medial primary vein, or midvein, runs toward the leaf apex and would measure 2.2 cm when it reaches the margin, but is only clearly visible in the proximal 1 cm of its length. The lateral primaries are visible for a few millimeters to roughly 6 mm of their length. Lateral secondary veins and higher venation cannot be observed.

R e m a r k s. The characteristics preserved in the Clarkia leaf are well within the range of variation in living water lilies of the Nymphaeaceae (cf. Taylor 2008, Taylor and Gee 2014, Gee and Taylor 2019), not only morphologically as described above, but also after a more critical analysis of single characters using phylogenetic analysis. To examine its relationship to the family Nymphaeaceae and living genera, we first entered the data of the Clarkia leaf into a previously constructed data matrix comprised of the livingtaxa data of Gee and Taylor (2019), then conducted the analysis. The phylogenetic analysis shows that the fossil leaf is well-embedded within the order Nymphaeales and family Nymphaeaceae . Even with the lack of fine venation, the phylogenetic analysis yields bootstrap support for the fossil leaf within Nymphaeales (68 %), but not within the Nuphar clade. Furthermore, mapping the Clarkia Nymphaea leaf on fig. 5 of Gee and Taylor (2019) also shows that it shares many synapomorphies with the Nymphaeales : 5, floating leaves usually peltate; 10, leaf base angle wide obtuse; 11, leaf apex angle obtuse; 19, primary veins actinodromous. Characters 5 and 10 are universally found in the order. Synapomorphies for Nymphaeaceae are also shared: 9, sinus length ratio 0.21 to 0.40; 12, leaf base cordate; 14, base margin curved; 15, cordate lobe shape with rounded point; 16, peltate base very eccentric. In this case, character 12 is universal for the Nymphaeaceae .

The Clarkia leaf differs in several ways from Nuphar leaves by exhibiting characters not found in Nuphar : 8, length/width ratio 1 to 1.29; 13, apex rounded; 18, medial slightly thicker than lateral primaries; 19, actinodromous. These differences restrict the relationship of the fossil leaf to the clade that encompasses Nymphaea , Barclaya WALL. , and Euryale SALISB. / Victoria LINDL.

Within the Nymphaea - Barclaya - Euryale / Victoria clade, the Clarkia leaf lacks the short cordate base of Barclaya , as well as the nearly central peltate attachment of the petiole and palinactinodromous primary venation of the Euryale / Victoria clade. Its placement is confirmed when the Clarkia leaf is put into a key of leaves of living Nymphaeaceae genera (cf. Taylor 2008). Based on the characters preserved in the Clarkia leaf, it fits best in the genus Nymphaea . Thus, the phylogenetic analysis is consistent with our assignment of the fossil leaf based on gross morphology to Nymphaea . The lack of details in the higher venation merely precludes identification at the species level, but not at the generic level.

F r e q u e n c y i n t h e l e a f a s s e m b l a g e. The single specimen of Nymphaea in the Clarkia leaf flora is a rare occurrence. It is the only such leaf in the entire collection made by Rember in 1976. If the leaf count made in only the 90 to 120 cm interval of section A is considered, the water lily leaf makes up 0.1 % of the 774 leaves found in this 30 cm stratigraphic interval. If the entire Clarkia collection described by Rember in 1991 is taken into account, the frequency of water lily leaves in the assemblage becomes even smaller, amounting to 0.01 % of the 10,641 specimens collected in the systematic sampling of section A.

Figures

Text-fig. 2. Nymphaea sp. from the Miocene Clarkia Lake flora, Locality P-33. a: Photograph of the fossil leaf. b: Sketch of leaf showing the salient features of shape, basal lobes and margin, eccentric insertion point of the abaxial petiole, and primary actinodromous venation. Dashed lines represent torn edge of lamina; dotted line is outline of right basal lobe. Line drawing by P. Martin Sander. Scale bar applies to both photo and drawing.