Early angiosperms from the Lower Cretaceous of Jixi, eastern ...

Angiospermae
Dicotyledonae
G. Sun, D.L. Dilcher / Review of Palaeobotany and Palynology 121 (2002) 91^112 97
Genus Asiatifolium Sun, Guo et Zheng, 1992
Type: Asiatifolium elegans Sun, Guo et Zheng
emend.Sun et Dilcher
Generic diagnosis: Leaf pinnately compound, rachis
nearly straight.Lea£et oblong to obovate;
apex obtuse to rounded; base cuneate.Margin
entire.Petiole chartaceous.Venation pinnate, brochidodromous;
midvein stout.Secondary veins 5^
8 pairs, nearly opposite.Tertiary and quaternary
veins nearly equal in thickness.Submarginal vein
present.
Asiatifolium elegans Sun, Guo et Zheng emend.
Sun et Dilcher
Plate I, 1^11; Plate III, 8^10; Fig.4A^C
Synonyms:
1992a Asiatifolium elegans Sun, Guo et Zheng; Sun et al., p.
546, pl.I, ¢gs.1^3.
1992a Chengzihella obovata Guo et Sun; Sun et al., p. 546,
pl.I, ¢gs.4^9.
1995 Asiatifolium elegans Sun, Guo et Zheng; Sun, p.429,
pl.141, ¢gs.1^3, text-¢g.9^2, 1^2.
1996 Asiatifolium elegans Sun, Guo et Zheng; Sun and
Dilcher, p.393, pl.1, ¢gs.1^9, text-¢g.1A^B.
Emended description: Leaf pinnately compound,
rachis nearly straight, rachis about 0.6^1.0 mm
in thickness.Lea£et obovate (oblanceolate), usually
1.9^4.8 cm (minimum = 0.7 cm) long by 1.1^
2.0 cm (minimum = 0.3 cm) wide; margin entire;
apex obtuse, often slightly rounded.Leaf lamina
partly asymmetrical, tapering gradually to form a
slight to pronounced asymmetrical base.Petiole
medium length ca. 1.0 cm long by 0.7 mm wide.
Petiolule very short 2.0 mm long by 1.0 mm wide,
appearing to be in£ated.Venation pinnate; midvein
conspicuous with a pronounced taper in
width towards the apex (base 0.5 mm to apex
0.1 mm) and straight to slightly curved. Secondary
veins appear subopposite with branching
more or less irregularly, at 40^50‡ angle from
midvein, secondary veins fork equally in the outer
1/3 of the lamina and may continue to fork two or
three times forming a network that eventually
joins a sub-marginal vein.Few or no intersecondary
veins.The tertiary venation and quaternary
venation often arising at 90‡ angles.Ultimate venation
preserved, appearing to form a closed network
of areole.An evident marginal vein (ca.0.1
mm wide) present just inside of the leaf margin by
about 0.2 mm.
Discussion: The new material (Plate I, 7;Fig.4B)
provides more complete characters of the leaf
which is actually compound, not simple as indicated
in Sun et al.(1992a).The marginal veins,
present just inside the leaf margin by a very short
distance, can be regarded as one of the main characters
of the present species.Regarding the loops
near the margin described by Sun et al.(1992a, p.
546), they seem to be very obscure and would best
be regarded as a sector of the marginal vein.Since
the main characters of Chengzihella obovata (Sun
et al., 1992a, p.546, pl.I, ¢gs.4^9) are consistent
with the present species, the former should be incorporated
into the present species.
Material: More than 20 specimens.
Locality and horizon: Chengzihe of Jixi, Heilongjiang,
China; Chengzihe Formation in the W-B
Section beds Nos.29, 42, 45 and 47.
Plate I.All of the specimens described here are collected from the Lower Cretaceous Chengzihe Formation of Jixi, Heilongjiang,
China, and are housed in Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing, China.
1^11. Asiatifolium elegans Sun, Guo et Zheng emend.Sun et Dilcher.
1, 2.PB16766.1.Bar = 0.5 cm.2.Bar = 1 cm.
3, 10.PB16771.3.Bar = 1 cm.10.Bar = 0.5 cm.
4, 5. PB16772.4.Bar = 1 cm.5.Bar = 0.5 cm.
6.SC10011.Bar = 0.5 cm.
7.SC10013.Bar = 0.5 cm.
8.SC10012.Bar = 0.5 cm.
9.PB16768.Bar = 1 cm.
11.Venation of the leaf and showing the intramarginal vein in detail of 9.Bar = 0.2 cm.