On the osteology and phylogenetic affinities of Morsoravis sedilis (Aves) from the early Eocene Fur Formation of Denmark

Morsoravis sedilis is a small bird from the early Eocene Fur Formation of Denmark, which in the original description was considered to be most closely related to Charadriiformes. Because Morsoravis has subsequently been likened to Pumiliornis tesselatus, an equally enigmatic bird from the middle Eocene of Messel in Germany, I perform here the first phylogenetic analysis including the two taxa. This analysis supports a sister group relationship between Morsoravis and Pumiliornis, and the clade including the two taxa is recovered as the sister taxon of the late Eocene/early Oligocene Eocuculus. I report a possible, albeit lost, second specimen of Morsoravis, and identify derived characters in support of a sister group relationship between Morsoravis and Pumiliornis. The analysis did not resolve the higher-level affinities of the clade including Morsoravis, Pumiliornis, and Eocuculus, and did not confirm charadriiform affinities of Morsoravis. More data on the osteology of the fossils, as well as an improved understanding of the interrelationships of extant birds, are needed for a well-established phylogenetic assignment of these fossil taxa.