Early Cretaceous Keteleerioxylon Wood in the Songliao Basin, Northeast China, and Its Geographic and Environmental Implications

Abstract

The extant Keteleeria is endemic to east and southeast Asia, while Keteleeria-like trees were widely distributed in the northern hemisphere in Earth's history. In this paper, we reported a novel wood fossil of Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov., collected from the middle part of the Yingcheng Formation, Yingcheng Coal Mine, Changchun City, Jilin Province, northeast China. The quantitative growth-ring analyses of K. changchunense indicate that it was evergreen with a leaf longevity of 1-3 years, which is consistent with the foliar retention of extant Keteleeria. Its high ring-markedness index (RMI) indicates that the climate seasonality was pronounced during the Early Albian period in the Songliao Basin, northeast China. The fossil records of Keteleeria and closely related taxa indicate that this group might have originated from high latitudes in the northern hemisphere, then spread and migrated southward during the Late Jurassic and Cretaceous periods, gradually decreased in the Cenozoic period, and so far only survives in east and southeast Asia.

Keywords: Cretaceous; Keteleeria; Keteleerioxylon changchunense sp. nov.; environment; geography.

Figure 1

Distribution of the extant Keteleeria species and variants in the world (Adapted with permission from Ref. [2]).

Figure 2

Location of Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov. in the Yingcheng Coal Mine (red star), Changchun City, Jilin Province, Northeast China.

Figure 3

Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov. (A). General view of the specimen JLJY-02. (B). Transverse section showing the resin canals (red arrows) and growth ring boundaries. (C). Close-up of the resin canals (red arrow). (D). Close-up of the growth ring boundary. (E). Radial section showing the vertical resin canal. (F). Radial section showing the biseriate pits on the radial walls of tracheids and the crassulae. (G,H). Radial section showing the opposite and alternate biseriate pits and triseriate pits and the crasulae on the radial walls of tracheids. Scale bar: A: the longer scale mark in the card is 1 cm; B = 1 mm; C, D, E = 200 μm; F, G, H = 50 μm.

Figure 4

Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov. (A). Radial section showing the opposite and alternate biseriate pits and triseriate pits and the crasulae on the radial walls of tracheids. (B). Radial section showing pitted horizonal and end walls of the ray parenchyma cells. (C). Tangential section showing the axial parenchyma cell. (D,E). Radial section showing taxodioid-cupressoid type cross-field pits. (F). Radial section showing the marginal ray cells resembling ray tracheids with scattered uniseriate pits (red arrows). (G). Tangential section showing uniseriate, partly biseriate rays. (H). Close-up of the rays showing uniseriate rays. (I). Tangential section showing the pitted end wall of ray parenchyma cell (red arrow). Scale bar: A, B, D, E, F, I = 50 μm; C, H = 100 μm; G = 200 μm.

Figure 5

The CSDM curves of five growth rings and cell diameters of growth ring increment. EW: Earlywood, LW: latewood. The arrows indicate the zeniths of CSDM curves. When the abscissa value of the zenith is greater than half of the cell number, the curve is right-skewed; on the contrary, it is left-skewed.

Figure 6

Geographical and geological distribution of Keteleeria-like fossils (red stars) in the world (global average temperature data from [90]).