New Material of Paleocene-Eocene Pellornis (Aves: Gruiformes) Clarifies the Pattern and Timing of the Extant Gruiform Radiation
2019
Grace Musser | Daniel T. Ksepka | Daniel J. Field
<i>Pellornis mikkelseni</i> is an early gruiform from the latest Paleocene-earliest Eocene Fur Formation of Denmark. At approximately 54 million years old, it is among the earliest clear records of the Gruiformes. The holotype specimen, and only material thus far recognised, was originally considered to comprise a partial postcranial skeleton. However, additional mechanical preparation of the nodule containing the holotype revealed that the skeleton is nearly complete and includes a well-preserved skull. In addition to extracting new information from the holotype, we identify and describe two additional specimens of <i>P. mikkelseni</i> which reveal further morphological details of the skeleton. Together, these specimens show that <i>P. mikkelseni</i> possessed a schizorhinal skull and shared many features with the well-known Paleogene Messelornithidae (“Messel rails”). To reassess the phylogenetic position of <i>P. mikkelseni</i>, we modified an existing morphological dataset by adding 20 characters, four extant gruiform taxa, six extinct gruiform taxa, and novel scorings based on the holotype and referred specimens. Phylogenetic analyses recover a clade containing <i>P. mikkelseni</i>, <i>Messelornis</i>, <i>Songzia</i> and crown Ralloidea, supporting <i>P. mikkelseni</i> as a crown gruiform. The phylogenetic position of <i>P. mikkelseni</i> illustrates that some recent divergence time analyses have underestimated the age of crown Gruiformes. Our results suggest a Paleocene origin for this important clade, bolstering evidence for a rapid early radiation of Neoaves following the end-Cretaceous mass extinction.
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