Early angiosperm woods from the mid-Cretaceous (Turonian) of New Mexico, USA: Paraphyllanthoxylon, two new taxa, and unusual preservation

Karen Chin, Emilio Estrada-Ruiz, Elisabeth A. Wheeler, Garland R. Upchurch, Douglas G. Wolfe

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Abstract

© 2019 Elsevier Ltd The fossil record of Cretaceous angiosperm wood is skewed toward the latest part of the period; most described taxa are based on specimens from Campanian or Maastrichtian sediments. The low percentage of pre-Campanian angiosperm woods relative to other flowering plant organs may reflect a taphonomic bias or the existence of relatively few woody angiosperm taxa until the last part of the Cretaceous. The discovery of three fossil angiosperm wood taxa in the Turonian Moreno Hill Formation of New Mexico offers additional data on the occurrence of secondary xylem in early angiosperms. These wood fossils represent a common Cretaceous wood taxon plus two new angiosperm wood types, and increase the number of known pre-Campanian wood types by 10–20%. Analyses of thin sections from a large (>50 cm diameter) silicified log at a locality in the lower Moreno Hill Formation reveal it is Paraphyllanthoxylon arizonense Bailey, a wood taxon known from Cenomanian and Maastrichtian to Paleocene sites in the American Southwest. Paraphyllanthoxylon arizonense represents large trees that may belong to Laurales. Several other sizeable logs in the same area are also likely to be P. arizonense. In contrast, two taxa from a stratigraphically higher site in the Moreno Hill have not been previously described and are each represented by only one specimen. These two new wood types, based upon small, phosphatic axes (5–7 cm in diameter), differ from Paraphyllanthoxylon in their smaller diameter vessels and scalariform perforation plates. The unique combinations of character states of these phosphatic specimens indicate that they are new genera. Although the taxonomic affinities of Herendeenoxylon zuniense gen. et sp. nov. are uncertain, it is possible that it belongs to the Ericales. The affinities of the other new wood type, Vasunum cretaceum gen. et sp. nov. are unknown. The presence of three angiosperm wood taxa in the Moreno Hill Formation is noteworthy because exposures of terrestrial Turonian deposits are uncommon. The large diameter and apparent abundance of P. arizonense in the lower member of the Moreno Hill Formation suggest that these trees were dominant members of woodland or forest habitats of the ancient coastal lowlands. The small diameters and scarcity of the other two wood types suggest that they came from shrubs or small trees that were not common.
Original languageAmerican English
Pages (from-to)292-304
Number of pages261
JournalCretaceous Research
DOIs
StatePublished - 1 Jun 2019

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