Implications of lack of morphological information in fossil leaves related to Lauraceae: a statistical evaluation

Fossil leaves serve as crucial repositories of palaeobiological information on angiosperms, with the Lauraceae family standing out as a highly represented group across geological time. The recognition of this diversity has been based mainly on comparing its leaf architecture and cuticle anatomical characteristics; however, the latter is sometimes not preserved, so leaf architecture is left as the only source of information available for identification in Lauraceae. This issue has produced a taxonomic mosaic in the family's fossil record, with taxa exhibiting well-established Lauraceae affinities and others with uncertain affinities. Nevertheless, the characters can be incompletely conserved (unknown characteristics), representing an obstacle in the identification process, which is one of the main challenges when making taxonomic assignments. Considering this problem, this study statistically analyses specific cases (it is not a taxonomic review of the family) and examines the taxonomic implications of this lack of information. The analysis used two statistical approaches: one accounting for the unknown information and another employing character imputation. A large dataset was utilized to ensure meaningful results, including extant Lauraceae taxa and fossils assigned to or related to the family. The results highlight the significant impact of unknown data on morphologic similarities and taxonomic affinities, particularly within Lauraceae, revealing challenges related to similar morphologies between extant and fossil groups and patterns found in other angiosperm groups. This study pioneered the demonstration and testing of this influential factor in taxonomic decisions, emphasizing the need for careful consideration in identifying fossil material.