Sapindopsis retallackii, 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 : 27-28

Sapindopsis retallackii sp. nov.

Figure 17

Specific diagnosis. Leaf compound, with three or four leaflets; most commonly three leaflets closely arranged on the distal portion of the rachis, occasionally with one leaflet attached at some distance proximally on rachis; rachis thin. Leaflet lorate, always curved abaxially; apex attenuate; base normal acute; lateral leaflets sessile and terminal leaflets petiolulate; margin entire, usually revolute. Primary venation pinnate; primary vein stout; course straight (medial leaflet) or recurved (lateral leaflets). Secondary venation brochidodromous; secondary veins thin relative to primary vein; opposite to subopposite, decurrent; angle of divergence acute, joining superadjacent secondary veins to form a loop enclosing an intercostal area, with two series of loops (tertiary and quaternary in order) in excostal region; exmedial branches of secondary veins common, forming tertiary veins. Intersecondary veins common. Tertiary vein moderate; orthogonal reticulate but tending to be percurrent, retroflexed. Quaternary veins random reticulate, forming incompletely closed meshes. Veinlets simple, linear.

Description. Leaflet lamina base symmetrical. Form lanceolate, L / W >5, 10 cm long (estimated length) and 1.8 cm wide. Apex missing. Base normal, acute; petiolule 1 cm long and 1 mm wide. Margin entire. Petiole normal, short, 0.8 cm long and 0.5 mm wide. Primary venation pinnate; primary vein stout, slightly curved, up to 0.5 mm wide at the widest portion of lamina. Secondary venation festooned brochidodromous; secondary vein fine relative to primary vein; secondary veins diverging from primary vein at narrow acute angles, with lowest one to two pairs more acute than pairs above; secondary veins slightly recurved after diverging from primary vein, then extending a distance to about one fourth to one half of half lamina before joining superadjacent secondary or intersecondary veins to form two series of loops in the excostal region. Intersecondary veins common, one to three pairs per intercostal region; intersecondary veins simple or occasionally forking at variable distance after diverging from primary vein; intersecondary veins almost the same width as secondary veins. Tertiary veins hair-like; diverging from primary veins, exmedial (lower) side of secondary veins or intersecondary veins at moderate acute to narrow acute angles, predominately exmedially ramified, orientation parallel to secondary or intersecondary veins, connected by cross veins of the same order. Number of specimens examined. 30.

Holotype. UF15706-3153 ( Figure 17 ).

Species epithet. In recognition of Greg Retallack and his contribution to the Dakota Formation geology and paleobotany.

Occurrences. Hoisington III locality, Kansas.

Remarks. Only one specimen, representing a terminal leaflet of a compound leaf, is observed from the Hoisington III locality. The venation pattern matches that of the compound leaves from the Springfield locality and Pleasant Dale locality, Nebraska (Wang and Dilcher, in preparation).

Sapindopsis retallackii is similar to Sapindopsis sp. A (Huang and Dilcher, 1994) in having three leaflets but they differ in that S. retallackii occasionally has four lorate leaflets, and brochidodromous secondary venation. Sapindopsis retallackii can be distinguished from other Sapindopsis species (see previous section) by the following suite of characters: compound leaf with petiolulate terminal leaflets, sessile lateral leaflets, lorate leaflet shape, brochidodromous secondary venation, the presence of exmedial branches of secondary veins that branch into tertiary veins, and common intersecondary veins.

Figures

FIGURE 17. Sapindopsis retallackii sp. nov. 1, UF15706-3153, showing a leaflet with entire margin. Note the petiolule at the base (indicated by arrow). Scale bar equals 5 mm. 2, Enlargement of Figure 17.1 to show numerous thin secondary and intersecondary veins. Scale bar equals 1 mm.