Pityostrobus yixianensis sp. nov., a pinaceous cone from the Lower Cretaceous of north-east China

Abstract

A silicified conifer cone was collected from Lower Cretaceous rocks in Yixian, Liaoning Province, north-east China. The cone is long and cylindrical, and its axis contains secondary xylem with resin canals. Vascular traces to the scale and its subtending bract are separate when they diverge from the vascular cylinder of the cone axis. Where the base of the scale is separate from the bract, resin canals are distributed adaxially and abaxially in the vascular traces. Bracts separate from the scales marginally, and the apex of each scale is flattened. Seeds are inverted and occur in pairs on the adaxial surface of fertile scale. Seed is winged and elliptical, lacking both resin cavities and vascular traces in its seed coat. The characters of the Chinese specimen have led to the description of a new species of the fossil genus Pityostrobus as E! yixianensis. When compared with other pinaceous genera, E? yixianensis shows greatest similarity to the extant genera Picea, Pseudotsuga and Larix. It differs from other species of Pityostrobus which have a close relationship with either the genus Pinus or Pseudoaraucaria. The evolutionary and phylogenetic position of Pityostrobus yixianensis is considered to represent an ancestral intermediate between extant conifer genera such as Picea, Pseudotsuga and Larix. Pityostrobus yixianensis represents the first record of

New fossil Pinaceae from the Early Cretaceous of Mongolia

“…Unfortunately the specimen of P. yixianensis is too eroded to provide information on the base of the cone, peduncle, and the form of the bract-scale complexes, which precludes full comparison with P. farjonii. The combination of anatomical characters seen in P. yixianensis is most similar to that seen in several living genera, including not only Picea but also Pseudotsuga and Larix (Shang et al 2001).…”

“…Pityostrobus yixianensis Shang, Cu et Li (Shang et al 2001) described from Yixian, Liaoning Province, northeast China, based on a single seed cone permineralized in silica, is superficially similar to Picea farjonii in its large number of bract-scale complexes, bracts that separate from the scale laterally and have two resin canals, and a seed coat that lacks resin vesicles. Pityostrobus yixianensis is also of interest because of its similar geographic position and Early Cretaceous (Aptian) age to P. farjonii.…”

“…yixianensis, P. ramentosa, P. shastaensis, P. californiensis, P. pluriresinosa, P. milleri, P. hokodzensis, P. andraei, P. bommeri, and P. corneti (Alvin 1953;Creber 1956Creber , 1967Miller 1976b;Falder et al 1998;Shang et al 2001;Ratzel et al 2001;Smith and Stockey 2001;Smith et al 2016); and from the Albian: P. hueberi, P. virginiana, P. argonnensis, P. mcmurrayensis Stockey, P. oblongus, and P. leckenbyi (Creber 1960(Creber , 1967Robison and Miller 1977;Stockey 1981). Pityostrobus stockeyae differs from all of these species in having articulated bracts with a deciduous distal needle-like segment that is often conspicuously exserted.…”

“…Especially important are diverse and structurally preserved seed cones from many localities in the Northern Hemisphere, most of which have been placed in three fossil genera: Pseudoaraucaria Fliche (Alvin 1957a(Alvin , 1957b(Alvin , 1960(Alvin , 1988Miller and Robison 1975), Obirastrobus Ohsawa, Nishida et Nishida (Ohsawa et al 1992), and Pityostrobus Nathorst emend. Dutt., a morphogenus that includes at least 29 species that are probably of diverse relationships to extant and extinct lineages of Pinaceae (e.g., Dutt 1916;Miller 1972Miller , 1974Miller , 1976bMiller , 1977bMiller , 1985Stockey 1981;Falder et al 1998;Stockey 2001, 2002;Shang et al 2001;Smith et al 2016). So far, few well-preserved and critically studied seed cones from the Early Cretaceous have been placed unequivocally in extant genera of Pinaceae (e.g., Alvin 1960; Klymiuk and Stockey 2012;Ryberg et al 2012).…”