New fossils of Eocypselus and Primapus from the British London Clay reveal a high taxonomic and ecological diversity of early Eocene swift‐like apodiform birds
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Media type:
E-Article
Title:
New fossils of Eocypselus and Primapus from the British London Clay reveal a high taxonomic and ecological diversity of early Eocene swift‐like apodiform birds
Description:
<jats:p>We describe new specimens and species of apodiform birds from the early Eocene London Clay of Walton‐on‐the Naze (Essex, UK). In addition to multiple partial skeletons of <jats:italic>Eocypselus vincenti</jats:italic> Harrison, 1984, three new species of <jats:italic>Eocypselus</jats:italic> are described as <jats:italic>Eocypselus geminus</jats:italic>, sp. nov., <jats:italic>Eocypselus paulomajor</jats:italic>, sp. nov. and <jats:italic>Eocypselus grandissimus</jats:italic>, sp. nov. The previously unknown quadrate of <jats:italic>Eocypselus</jats:italic> shares a characteristic derived morphology with the quadrate of the Aegothelidae, Hemiprocnidae and Apodidae, whereas the quadrate of the Trochilidae is very different. We also report a striking disparity of the shapes of the axis vertebra of apodiform birds, which is likely to be of functional significance. <jats:italic>Eocypselus</jats:italic> and extant Hemiprocnidae and Cypseloidini (Apodidae) exhibit the plesiomorphic morphology, whereas a derived shape characterizes extant Aegothelidae, Apodini and Trochilidae. Furthermore, we describe the first partial skeleton of the earliest aegialornithid species, <jats:italic>Primapus lacki</jats:italic> Harrison & Walker, 1975, which was previously only known from the humeri of the type series that stem from different sites of the London Clay. The apodiform birds from Walton‐on‐the‐Naze show a considerable taxonomic and ecomorphological diversity, and whereas <jats:italic>Eocypselus</jats:italic> may have inhabited forest edges and caught insects by sallying flights from perches, <jats:italic>Primapus</jats:italic> probably was a fast‐flying and more aerial bird.</jats:p>