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

G. Sun, D.L. Dilcher / Review of Palaeobotany and Palynology 121 (2002) 91^112 99
Genus Jixia Guo et Sun, 1992
Type: Jixia pinnatipartita Guo et Sun emend.Sun
et Dilcher
Generic diagnosis: Leaf simple, pinnately lobed,
lobes opposite to alternate.Obtuse sinuses extending
to near midvein.Venation pinnate.Midvein
prominent, arched to zigzag.Secondary veins decurrent
along midvein, transversing lamina lobe
near admedial margin.Tertiary and quaternary
veins present.Marginal vein present.
Jixia pinnatipartita Guo et Sun emend. Sun et
Dilcher
Plate II, 1,9;Fig.4D
Synonyms:
1992a Jixia pinnatipartita Guo et Sun; Sun et al., p. 547, pl.
I, ¢gs.10, 12; (non pl.I, ¢g.11).
1992a Rogersia lanceolata Fontaine; Sun et al., p. 543, pl. I,
¢g.15.
1995 Jixia pinnatipartita Guo et Sun; Sun, p.429, pl.141,
¢g.4; text-¢g.9^2, 3.
1996 Jixia pinnatipartita Guo et Sun; Sun and Dilcher, p.
393, pl.1, ¢g.10; text-¢g.1C.
Emended description: Leaf simple, deeply once
pinnately lobed, ca. 1.5^4.5 cm long by 0.6^4.0
cm wide.Margin entire.Apex not preserved;
base narrow cuneate.Petiole incomplete.Lobes
subopposite to alternate, vary in number, form
and size.Basal lobes shorter and appear placed
at an angle of 80‡ to the midvein.Median lobes
narrowly oblong orientated at angles of 60^70‡ to
the midvein, extending free some distance from
the central leaf lamina.Deep obtuse sinuses with
rounded margins extending nearly to the leaf midvein
separate the lobes.Midvein arched, prominent
and giving rise to prominent secondary veins
that arch gradually paralleling the midvein for a
short distance, a signi¢cant portion of the midvein
appears to feed into each secondary vein.The secondary
veins innervate the lobes asymmetrically
transversing the lamina lobe nearer the admedial
lobe margin.Tertiary veins branch at an angle of
75‡ and are often parallel, may branch once near
the leaf margin before joining a marginal vein.
Some tertiary veins extending into narrow lamina
of the lobes depart at an angle of nearly 90‡.
Quaternary venation may branch at nearly right
angles from the tertiary veins forming poorly preserved
areoles.
Discussion: The emended description of the
present species is mainly supplemented by having
the evident marginal vein and the character classi-
¢ed of its tertiary and quaternary venation.One
of the specimens originally described as the
present species (Sun et al., 1992a, p.547, pl.I,
¢g.11) di¡ers from the present species in having
a multi-lobed leaf, and secondary veins arising
opposite or nearly opposite from the midvein.
Therefore, this species of the genus Rogersia originally
described by Fontaine (1889), has been assigned
to a new species described below in detail.
Reviewing the specimen Rogersia lanceolata, originally
described by Sun et al.(1992a, p.543, pl.I,
¢g.15) is actually a segment lobe of the present
species.
Material: 6 specimens.
Locality and horizon: Ibid., in the W-B section
beds Nos.45 and 47.
Jixia chengzihensis Sun et Dilcher sp. nov.
Plate II, 2, 3, 5^8, 10, 11, 13; Fig.4F,I
Synonyms:
1992a Jixia pinnatipartita Guo et Sun; Sun et al., p. 547, pl.
I, ¢g.11.
1995 Jixia chengzihensis Sun et Dilcher; Sun, p.429, p1.
141, ¢gs.5, 7, text-¢g.9^2, 4; [nomen nudum, nomen
invalidum].
1996 Jixia chengzihensis Sun et Dilcher; Sun and Dilcher,
p.393, p1.1, ¢g.11, text-¢g.1D; [nomen invalidum].
Description: Leaf simple, deeply pinnately lobed.
Lobes may have pinnate shallow lobes, usually
1.7^3.2 cm long by ca. 2.0 cm wide. Margin entire.Apex
and base not preserved.Primary lobes
opposite to subopposite, vary in size and shape.
Some lobes preserved are ca. 1.0 cm long by 0.3^
0.4 cm wide at lobe base increasing to 0.7^0.8 cm
wide where secondary lobes are present.One or
two pairs of secondary lobes borne from middle
to apex of the primary lobe.Secondary lobes subopposite
with rounded apex.Midvein of leaf progresses
somewhat zigzag fashion from lobe to
lobe.Midvein prominent, 0.6 mm wide basally
and tapers distally.Secondary veins slightly irregular
that extend into the secondary lobes.Tertiary