Callipteris seshufenensis Chen

Chen, Xin-Yu, Zhang, Hua-Chuan & Yang, Jin-Yue, 2024, A new fossil species of Callipteris (Callipteridae) in the Early Permian from the Xishan Area in Beijing, North China, Phytotaxa 641 (4), pp. 295-300 : 296-297

† Callipteris seshufenensis Chen , sp. nov.

Holotype: SWZXZW 0100004.

Repository: Cores and Samples Center of Land & Resources (CSCLR), Sanhe, Hebei, China.

Type locality: Seshufen village, Mentougou District, Beijing, China.

Stratigraphic horizon: Shanxi Formation, the Early Permian.

Etymology: Species name referring to the occurrence of the fossils in Seshufen village.

Diagnosis: Pinnules small and lobate to small and lobed, spaced and marginally decurrent, and not retracted at the base, with a rounded-obtuse apex. Lobate pinnules with slightly asymmetrical margins bearing at least five rounded lobes in which 1–2 rounded lobes are generally poorly developed. Presence of a delicate (poorly developed) basal lobe. Pinna rachis narrow with obvious transverse stripes, invisible at the base, without attenuations at the pinnule apex. Lateral veins regular and thick, except for the rounded obtuse apex of pinnule, the other small pinnules have 2–3 lateral branches directly connected with pinna-rachis and slightly bent outward. Midvein divided more than three times (sometimes more than five times).

Description: The holotype (SWZXZW 0100004; Fig. 1 ) is a small fragment of frond. The different frond parts are sterile and show pinnules of variable shape and size. The pinna-rachis is 0.5–0.8 mm wide. The pinnules are inserted obliquely from the pinna-rachis at about 45° to 55° and are not closely spaced, tapering gradually towards smaller pinnules in the distal parts of pinna-rachis. The pinnules are 2–6 mm long and 1.2–1.5 mm wide, spaced and marginally non-decurrent, with rounded obtuse apex, and are obliquely attached to rachis forming angles almost perpendicularly.

Larger pinnules are located in the middle and lower parts of the pinnae (intermediate and proximal pinnules). The lobes are lobate, generally well developed (except the basal lobe), and ten in number. The pinna-rachis is narrow with obvious transverse stripes ( Fig. 2A ), with a small attenuation at the pinnule apex.

The midvein is divided ( Fig. 2B ) more than five times (sometimes more than six times). It is generally once forked shortly after arising from the midvein, with the second fork approximately one-sixth of the midvein length, the second fork and the third forks approximately one-third and one-half of the midvein length, and the fourth and the fifth forks approximately two-thirds and five-sixths respectively. The sixth forking occurs very rarely, near the pinnule margin. The lateral veins are regular, strong, and closely spaced, with a vein density that ranges between 20 and 24 per 10 mm on the pinnule margin.

Comparison: The material described in this paper is similar to the fossils of C. conferta in oval pinnae shape and slightly decurrent base. However, the pinnule midveins of C. conferta extend out at a narrow angle, and then bend out at a wide angle, and do not disperse until reaching the top of the small feather. Callipteris biforma Huang, 1977 has two kinds of pinnule shape: one is tongue-shaped with pinnules long and narrow; the other is dome shaped (bluntly triangular or semicircular) with pinnules short and wide. Callipteris heilongjiangensis Huang, 1977 has pinnules each with a half-pointed tip, and very fine lateral veins extending from the midvein at a very narrow angle (15° to 20°). The pinnae of Callipteris pseudoshenshuensis Huang, 1977 are at least 16 cm above, and the tongue shaped pinnules are narrow and long (34 mm long and 11 mm wide), and some are short and wide (26 mm long and 14 mm wide). The fossil differs from species Callipteris zeilleri Zalessky, 1948 by having 2–6 mm long and 1.2–1.5 mm wide pinnules (vs. 10 mm long and 5 mm pinnules), strong midvein (vs. weak midvein) and strong lateral veins (vs. fine lateral veins).

Figures

FIGURE 1. Callipteris seshufenensis. A. Holotype (SWZXZW 0100004), B. Line drawing of Holotype showing the venation details. Scale bar = 1 cm.

FIGURE 2. Details of Callipteris seshufenensis. A. Pinna-rachis, B. Midvein. Scale bar = 1 mm.