Investigations On Coniferous Wood From The Jurassic Tiaojishan Formation In Jianchang,western Liaoning Province

The Middle to Upper Jurassic Tiaojishan Formation,mainly distributed in western Liaoning Province,e.g.,Beipiao,Chaoyang,Fuxin and Jianchang regions,is one of the most significant horizons for the Jurassic petrified wood in northern China.Diverse and rich fossil wood records have been documented in this formation.Previously,fossil wood of the Tiaojishan Formation was mainly reported in Batuying and Changgao regions of Beipiao City,whereas fossil woods from Jichang region are poorly known.A systematic investigation is given on the Jurassic petrified wood found in Jianchang region.Totally five species referred to three genera of petrified wood were described.Among them,two new species,Protophyllocladoxylon jianchangense sp.nov.and Protaxodioxylon liaoningense sp.nov.,are recognized in this paper.These new findings contribute to further understanding the fossil wood diversity of the Middle-Late Jurassic of the Tiaojishan Formation in Jianchang region.In addition,some well-preserved fungal remains,represented by fungal hyphae with typical clamp-connection and asexual spores(chlamydospores),were found within the fossil wood tissue.The occurrence of clamp-connection indicates that the fungal remains systematically belong to the Basidomycota.Typical wood decay structures of the host resembling the extant white-rot indicate that the current fungal remains to be white-rotting fungi.The fungal remains represent the first record of the Jurassic wood rotting fungi in Jianchang,western Liaoning,China,and shed light revealing the plant-fungal interaction in the Middle-Late Jurassic forest ecosystem.Petrified wood plays a significant role in understanding the terrestrial palaeoclimate and palaeoenvironment in geological past.The fossil wood genus Xenoxylon Gothan is extensively accepted as an indicator of cool and/or wet climate.The occurrence of diverse Xenoxylon woods infers that a cool and wet climate condition may be prevailed during the sedimentation period of the Tiaojishan in Jianchang region.The existence of distinct growth rings shows that the palaeoclimate had seasonal variations.Additionally,the calculations of the Annul Sensitivity(AS)and Mean Sensitivity(MS,most lower than 0.3)and E/L of the growth rings of the studied fossil wood material indicate that water supply was relatively sufficient.