Scientific knowledge about the ancestral genome of core eudicot plant kingdom can potentially have profound impacts on both basic and applied research, including evolution, genetics, genomics, ecology, agriculture, forestry, and global climate. To investigate which plant conserves best the core eudicots common ancestor genome, we compared Arcto-Tertiary relict Nyssaceae and 30 other eudicot plant families. The genomes of Davidia involucrata (a known living fossil), Camptotheca acuminata and Nyssa sinensis, one per existent genus of Nyssaceae, were performed comparative genomic analysis. We found that Nyssaceae originated from a single Nyssaceae common tetraploidization event (NCT)– autotetraploidization 28–31 Mya after the core eudicot common hexaploidization (ECH). We identified Nyssaceae orthologous and paralogous genes, determined its chromosomal evolutionary trajectory, and reconstructed the Nyssaceae most recent ancestor genome. D. involucrata genome contained the entire seven paleochromosomes and 17 ECH-generated eudicot common ancestor chromosomes and was the slowest in mutation among the analyzed 42 species of 31 plant families. Combing both its high retention of paleochromosomes and its low mutation rate, D. involucrata provides the best case in conservation of the core eudicot paleogenome.