Sapindopsis powelliana (Lesquereux) Wang & Dilcher, 2018

Wang, Hongshan & Dilcher, David L., 2018, Early Cretaceous angiosperm leaves from the Dakota Formation, Hoisington III locality, Kansas, USA, Palaeontologia Electronica (34 A) 21 (3), pp. 1-49 : 20-27

Sapindopsis powelliana (Lesquereux) comb. nov.

Figures 13-16

Basionym. Rhus powelliana Lesquereux (1892, p. 155, plate 56, figures 4, 5).

Emended specific diagnosis. Leaf compound, trifoliolate or paripinnate, consisting of three to six pinnately alternate to opposite leaflets; leaf stipulate, petiole thin; lateral leaflets petiolulate, terminal leaflets petiolulate or sessile, narrow oblong to narrow elliptic; leaflet margin entire. Primary venation of leaflets pinnate; primary vein multi-stranded, stout to massive, course straight. Secondary venation eucamptodromous or slightly brochidodromous; intersecondary veins common, composite. Tertiary veins thick relative to secondary veins, predominately percurrent, slightly convex; arrangement on secondary vein predominately alternate. Quaternary veins orthogonal, forming quadrangular or pentagonal imperfect areoles; veinlets simple, curved or straight.

Description. Leaf compound, trifoliolate ( Figure 15 ) or paripinnate ( Figure 16.1 ); leaflets alternate ( Figure 16.1 ) to opposite ( Figures 13.1 , 14 ); leaf stipulate ( Figures 13.1 , 15 ), petiole thin, stipules up to 1.5 cm long and 0.6 cm wide, with venation parallel to the long axis; leaflets narrow oblong ( Figures 13.1 , 14.1-2 , 15 ) to narrow elliptic ( Figure 13.4 ); leaflet 6.5 cm to 13.5 cm long and 1.5 cm to 2.5 cm wide ( L / W 4.3 to 5.4); leaflet margins entire, structurally reinforced, apex acute to acuminate, base acute and asymmetrical, terminal leaflet tissue decurrent on rachis; two ultimate leaflets oppositely arranged, with outer sides lamina decurrent on rachis ( Figure 13.1 ), giving a bilobed appearance; the apex of the ultimate leaflets sometimes lobed once, with deep sinus extending about 30% distance of lamina length, bracing of the sinus accomplished by forking of primary veins and then running along the margin within sinus ( Figure 14.2 ). Lateral leaflets petiolulate and terminal leaflets petiolulate or sessile ( Figure 14.2 ); petiolule thin, about 1 mm wide and up to 3.5 cm long ( Figure 15 ). Primary venation of leaflets pinnate; primary vein multi-stranded, stout to massive (the ratio of vein width to lamina width is ca. 4%), course straight. Secondary venation eucamptodromous ( Figure 9.2, 9.5 ; secondary veins upturned and gradually diminishing apically inside the margin, connected to the superadjacent secondary veins by a series of cross veins without forming prominent marginal loops) or slightly brochidodromous; secondary veins moderate in thickness, ca. 15 pairs per leaflet lamina; secondary veins uniformly originate from primary vein at moderate to narrow acute (less than 65 °) angle, up to 15 pairs per leaflet, subopposite, uniformly curved and diminish near lamina margin; intersecondary veins common, composite (made up of coalesced tertiary vein segments for over 50% of its length). Tertiary veins thick relative to secondary veins, angle of origin acute-obtuse ( AO, lower side of the secondary vein and upper side of the secondary veins), predominately percurrent, slightly convex; arrangement on secondary vein predominately alternate.

Quaternary veins orthogonal (arising at right angles), forming quadrangular or pentagonal imperfect areoles; veinlets simple, curved or straight.

Number of specimens examined. 110.

Neotype (designated here). UF15706-14830 ( Figure 13.1-3 ).

Other specimens illustrated. UF 15706-14814 ( Figure 13.4-5 ); 24670 ( Figure 14.1 ); 4812 (Figure

14.2); 24719 ( Figure 15 ); 24711 ( Figure 16.1 ); 24675 ( Figure 16.2 ).

Remarks. Lesquereux (1892, p. 155, plate 56, figures 4, 5) described two specimens from the Dakota flora and assigned them to an extant genus and established a new species, Rhus powelliana . He did not designate a holotype specimen for the new species and both specimens he described are currently missing. Based on Article 9.7 of the International Code of Botanical Nomenclature (McNeill et al., 2012), we here designate one specimen from Hoisington III locality, Kansas ( UF 15706- 14830; Figure 13.1-3 ) as the neotype. We transfer this species to the genus Sapindopsis based upon the following diagnostic characters: 1) pinnately compound leaf with terminal lobes or leaflets commonly more or less united at their base ( Figure 13.1 ); 2) distal leaflets with lamina decurrent to the leaf rachis and continuing as a narrow marginal lamina on either side of the rachis ( Figure 14.1 ); 3) the decurrent lamina on the rachis missing entirely toward the leaf base ( Figure 14.2 ); 4) leaflets elliptical to lanceolate-shaped, stout midrib extending to the apex of each leaflet ( Figures 13-15 ); and 5) eucamptodromous secondary venation.

The genus Sapindopsis was established by Fontaine (1889) and the generic diagnosis was emended by Berry (1911d). A total of eight species were originally proposed. Dilcher and Basson (1990) emended the generic diagnosis and proposed that the simple leaf forms (e.g., Sapindopsis cordata Fontaine, 1889, p. 296, plate 147, figure 1), in synonymy with Ficophyllum crassinerve Knowlton (1919) and Sapindopsis elliptica Fontaine (1889, p. 297, plate 147, figure 3), and in synonymy with Rogersia longifolia Berry (1911d) should be excluded from the genus Sapindopsis . The large distance between adjacent secondary veins and the well-defined intercostal region by secondary veins in Rogersia are distinct from those of the Sapindopsis powelliana leaves. The other six species, including Sapindopsis magnifolia Fontaine (Fontaine, 1889, p. 297, plate 151, figures 2, 3, plate 152, figures 2, 3, plate 153, figures 2, 3, plate 154, figures 1, 5, plate 155, figure 6; Berry, 1911d, p. 471, plate 86, figures 1-3, plate 87, figure 1, plate 88, figure 1; Berry, 1922, p. 214, plate 55, figure 5, plate 56, plate 57, figure. 2, plate 59, figure 3; Doyle and Hickey, 1976, p. 166-167, figures 17-19; Hickey and Doyle, 1977, p. 35, figures 33- 38), Sapindopsis variabilis (Fontaine, 1889, plate 151, figure 1, plate 152, figures 1, 4, plate 153, figure 3, plate 154, figures 2-4, plate 155, figures 2-5; Berry, 1911d, p. 469, plate 83, figures 109, plate 84, figures 1-2, plate 85, figure 1; Berry, 1922, p. 213, plate 55, figures 2-4), Sapindopsis parvifolia Fontaine (Fontaine, 1889, p. 300, plate 154, figure 6), Sapindopsis brevifolia Fontaine (Fontaine, 1889, p. 300, plate 153, figure 4, plate 155, figures 1, 7, plate 163, figure 3; Berry, 1911d, p. 473, plate 87, figures 2-5; Berry, 1922, p. 216, plate 55, figure 1, plate 59, figure 1), Sapindopsis tenuinervis Fontaine (Fontaine, 1889, p. 301, plate 153, figure 1), and Sapindopsis obtusifolia Fontaine (Fontaine, 1889, p. 301, plate 156, figure 13, plate 159, figures 3-6), can be distinguished from Sapindopsis powelliana by their sessile leaflets. Sapindopsis belviderensis Berry (Berry, 1922a, p. 216-217, plates 49-54; Hickey and Doyle, 1977, p. 35-36, figures 39-40) has toothed leaflets which is different from Sapindopsis powelliana .

Sapindopsis powelliana is similar to a specimen ( Sapindopsis sp. ) illustrated as the frontispiece by Hickey and Doyle (1977). This specimen is from Red Point, Cecil County, Maryland (upper Subzone II-B; late Albian), and it may belong to the same species. They are similar in that both species have lateral leaflets with long petiolules and lobed terminal leaflets.

Dilcher and Basson (1990) described one species (also see Krassilov and Bacchia, 2000), Sapindopsis anhouryi from the Nammoura locality, Lebanon. The stipules of this species are similar to those of S. powelliana leaves but they differ in that the leaflets of Sapindopsis powelliana are petiolulate and the secondary venation is eucamptodromous. Well-defined intercostal regions by secondary veins and intramarginal veins are also absent from the leaflets of Sapindopsis powelliana .

Huang and Dilcher (1994) described four types of pinnately lobed leaves from the Cheyenne Sandstone. Of these leaves, Sapindopsis sp. B is similar to the trifoliate leaf ( Figure 15 ) from the Hoisington III locality. Unfortunately, it is difficult to compare them in detail because no venation higher than the second order can be observed for the Cheyenne Sandstone specimens.

Sapindopsis powelliana leaves can be distinguished from other Cretaceous species of Sapindopsis reported around the world by its entire leaflet margin, petiolulate leaflets, eucamptodromous secondary venation, and predominately percurrent tertiary venation. These species include, Sapindopsis cf. Sapindopsis magnifolia / variabilis Fontaine (Upchurch et al., 1994, p. 40, figures 54- 57), Sapindopsis minutifolia Upchurch et al. (1994, p. 41, figures 58, 59), Sapindopsis lebanensis Krassilov and Bacchia (Krassilov and Bacchia, 2000, p. 782, figures 8, 9A-D; Golovneva, 2007, p. 1081, plate 3, figure 1), Sapindopsis neuburgae Golovneva (2007, p. 1081, plate 3, figure 1), Sapindopsis janschinii Golovneva (2007, p. 1081, plate 3, figures 2-5, plate 4), Sapindopsis kryshtofovichii Golovneva (2007, p. 1083, plate 5, figures 1-4; plate 6, figures 1-4).

Doyle and Hickey (1976) and Dilcher and Basson (1990) recognized two distinct types of Sapindopsis leaves. One type has fused terminal leaflets and decurrent lamina tissue on the rachis. The other type rarely has fused terminal leaflets and frequently the leaflets are petiolulate and lack any decurrent lamina tissue on the rachis. Most leaves of Sapindopsis powelliana belong to the second type but with occasional exceptions ( Figure 14.1 ). As suggested by Dilcher and Basson (1990), a detailed study of the leaf types of Sapindopsis is needed in order to separate these forms into distinct genera. A reexamination of the actual stratigraphic positions of these leaf forms is also needed in order to understand the direction of leaf evolution.

Compared with all other species assigned to Sapindopsis , S. powelliana seems to have the highest leaf venation rank. Most other species of Sapindopsis from the Potomac Group have the second leaf rank. This is in agreement with Doyle and Hickey (1976) and Hickey and Doyle’s (1977) summary of the Potomac leaf sequence because the Dakota Formation is younger than the Potomac Group.

Although the genus Sapindopsis was originally proposed by Fontaine (1889) as a member of the Sapindaceae , there is no evidence that Sapindopsis is more closely related to extant Sapindaceae than to other groups (Crane, 1989; Crane et al., 1993; Upchurch et al., 1994). Many features of leaf architecture and cuticular anatomy in fossil Sapindopsis , and its co-occurrence with platanoid reproductive structures show that they are probably more closely related to Platanaceae (Hickey and Wolfe, 1975; Hickey and Doyle, 1977; Upchurch, 1984; Upchurch and Dilcher, 1990; Wang et al., 2011).

Figures

FIGURE 13. Sapindopsis powelliana (Lesquereux) comb. nov. 1, UF15706-14830. leaf with four leaflets. Note two ultimate leaflets appearing to be bilobed (indicated by arrow on the left), two oppositely arranged lateral leaflets, and stipule at the base. Scale bar equals 1 cm. 2, Enlargement of Figure 13.1 (indicated by arrow on the right) to show secondary and tertiary venation. Scale bar equals 2 mm. 3, Enlargement to of Figure 13.1 to show venation of the stipule. Scale bar equals 2 mm. 4, UF15706-14814, an elliptic leaflet with acuminate apex. Scale bar equals 1 cm. 5, Enlargement of Figure 13.4 to show secondary and tertiary venation. Scale bar equals 3 mm.

FIGURE 14. Sapindopsis powelliana (Lesquereux) comb. nov. 1, UF15706-24670, leaf with three leaflets. Note bilobed ultimate leaflet. Scale bar equals 1 cm. 2, UF15706-4812, leaf with narrow oblong leaflets. Scale bar equals 1 cm.

FIGURE 15. Sapindopsis powelliana (Lesquereux) comb. nov. UF15706-24719, leaf with two opposite lateral leaflets, one ultimate leaflet with long and thin petiolule, and a stipule at the base of petiole (indicated by arrow). Scale bar equals 1 cm.

FIGURE 16. Sapindopsis powelliana (Lesquereux) comb. nov. 1, UF15706-24711, leaf with six leaflets (indicated by numbers). Note eucamptodromous secondary venation and strong secondary veins. Scale bar equals 1 cm. 2, UF15706-24675, leaf with two ultimate lobed leaflets. Note that the apex of each lobe of the two leaflets dissects one more time to form two smaller lobes (indicated by arrows). Scale bar equals 1 cm.

FIGURE 9. 1 and 3, Rogersia dakotensis Wang and Dilcher, 2009, UF15706-24798, general leaf shape, note thin secondary veins forming intramarginal veins (scale bar equals 5 mm) (1) and enlargement to show intramarginal veins formed by looping secondary veins (scale bar equals 1 mm) (3). 2 and 4, Rogersia parlatorii Dilcher and Wang, 2006, UF15706-7529, specimen showing leaf shape (scale bar equals 5 mm) (2) and enlargement to show secondary venation (scale bar equals 5 mm) (4).