内蒙古赤峰早中新世两种槭属化石及其古气候、古地理意义OA

Acer Linn.represents a significant component among the northern temperate broad-leaved forests,with a wide geographical distribution across the northern temperate regions and occasionally extending into certain subtropical zones.In this study,we document nine leaf fossils and two samara fossils of Acer from the Laoliangdi Formation in Chifeng,Inner Mongolia.These fossils were identified as A.cf.sinense of section Palmata and A.cf.buergerianum of section Oblonga based on detailed morphological observations and comparisons.Furthermore,we reconstructed the dispersal routes of these two sections using the fossil record.During the Paleocene,section Palmata was restricted to East Asia.By the Late Eocene,it expanded into Europe via the Turgai Strait.During the Oligocene and Miocene,this section became widespread across Eurasia.In the Pliocene and Pleistocene,its distribution was again limited to East Asia.However,during the Holocene,section Palmata expanded from East Asia to North America,resulting in the current disjunct distribution between these two continents.Section Oblonga likely migrated from the high latitudes of North America to the mid-latitudes of East Asia via the Bering Land Bridge during the Late Eocene.After the Miocene,this section disappeared from North America and persisted exclusively in East Asia,where it remains widely distributed today.The distinct dispersal histories of sections Palmata and Oblonga highlight the need for further investigation into the biogeographical pathways of Acer species across different sections.Additionally,by integrating the current climatic parameters of the habitats of A.sinense and A.buergerianum with those of the reported Early Miocene plant fossils in Chifeng,Inner Mongolia,we estimate that the mean annual temperature in Chifeng during the Early Miocene ranged from 10.6 to 18.2 ℃,with annual precipitation ranging from 950 to 1492 mm.These data indicate a warm and humid climate in the Early Miocene.This study further enriches the plant diversity in Early Miocene eastern Inner Mongolia and provides new evidence for the climate of this region during the Early Miocene.