Gerald Mayr’s research while affiliated with Senckenberg Research Institute and other places

Fossils of the avian clade Strisores (nightjars, swifts and allies) are well represented in some early Eocene localities. These birds were also taxonomically diverse in the British London Clay, but most of the previously described fossils belong to the Apodiformes (swifts and allies), or are represented by very fragmentary specimens. Here we report substantial new material of non-apodiform taxa of the Strisores from Walton-on-the-Naze (Essex, UK) that bears on the diversity and affinities of aerial insectivores from the London Clay. In addition to specimens of the recently described archaeotrogonid Archaeodromus , we report partial skeletons of the enigmatic taxon Palaeopsittacus , as well as two new species of the Fluvioviridavidae. The new Archaeodromus fossils reveal previously unknown osteological details, including features of the skull. The Palaeopsittacus specimens suggest that this poorly known taxon may be the earliest stem group representative of the Nyctibiiformes. The specimens of the Fluvioviridavidae elucidate some aspects of the osteology of these birds and the quadrate shows a morphology that is distinct from all extant Strisores. The non-apodiform Strisores from Walton-on-the-Naze exhibit disparate morphologies, which indicate that there was already significant ecological diversification of these birds by the early Eocene, and the diversity of these aerial insectivores in Walton-on-the-Naze contrasts with the absence of bats in this locality and other sites of the London Clay.

We describe upupiform, coraciiform, and possible piciform birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). The material includes partial skeletons of a new species of a small upupiform bird, Waltonirrisor tendringensis , gen. et sp. nov., which is the earliest known representative of the Upupiformes. Three very similar species of stem group rollers are assigned to Laputavis robusta , Septencoracias morsensis , and S. simillimus , sp. nov. These species only differ in minor features, which raises the possibility that the taxon Sepencoracias Bourdon, 2016 is a junior synonym of Laputavis Dyke, 2001. A smaller stem group roller from Walton-on-the-Naze resembles the North American primobucconid species Primobucco mcgrewi . We also describe two species of a new genus-level taxon, Pristineanis , gen. nov., which shows close affinities to the North American “ Neanis ” kistneri and may be a stem group representative of the Piciformes. In many aspects of their postcranial osteology, the stem group Coracii from Walton-on-the-Naze, as well as the new taxon Pristineanis, resemble coeval Trogoniformes from this fossil site. Because trogons are the extant sister taxon of the Picocoraciades – the clade including the Upupiformes, Coraciiformes, and Piciformes –, the shared similarities are likely to be plesiomorphic for this latter clade. Early Cenozoic representatives of the Upupiformes and Coraciiformes were much smaller than their extant relatives, which suggests that the Picocoraciades are an avian example of Cope’s Rule that postulates a tendency for size increase in evolutionary lineages over time.

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 Eocypselus vincenti Harrison, 1984, three new species of Eocypselus are described as Eocypselus geminus , sp. nov., Eocypselus paulomajor , sp. nov. and Eocypselus grandissimus , sp. nov. The previously unknown quadrate of Eocypselus 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. Eocypselus 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, Primapus lacki 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 Eocypselus may have inhabited forest edges and caught insects by sallying flights from perches, Primapus probably was a fast‐flying and more aerial bird.

We report avian cervical vertebrae from the Quercy fissure fillings in France, which are densely covered with villi‐like tubercles. Two of these vertebrae stem from a late Eocene site, another lacks exact stratigraphic data. Similar cervical vertebrae occur in avian species from Eocene fossils sites in Germany and the United Kingdom, but the new fossils are the only three‐dimensionally preserved vertebrae with pronounced surface sculpturing. So far, the evolutionary significance of this highly bizarre morphology, which is unknown from extant birds, remained elusive, and even a pathological origin was considered. We note the occurrence of similar structures on the skull of the extant African rodent Lophiomys and detail that the tubercles represent true osteological features and characterize a distinctive clade of Eocene birds (Perplexicervicidae). Micro‐computed tomography (μCT) shows the tubercles to be associated with osteosclerosis of the cervical vertebrae, which have a very thick cortex and much fewer trabecles and pneumatic spaces than the cervicals of most extant birds aside from some specialized divers. This unusual morphology is likely to have served for strengthening the vertebral spine in the neck region, and we hypothesize that it represents an anti‐predator adaptation against the craniocervical killing bite (“neck bite”) that evolved in some groups of mammalian predators. Tuberculate vertebrae are only known from the Eocene of Central Europe, which featured a low predation pressure on birds during that geological epoch, as is evidenced by high numbers of flightless avian species. Strengthening of the cranialmost neck vertebrae would have mitigated attacks by smaller predators with weak bite forces, and we interpret these vertebral specializations as the first evidence of “internal bony armor” in birds.

We report charadriiform and charadriiform-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). A partial skeleton of a small modern-type charadriiform is described as a new species, Charadriisimilis essexensis n. gen. n. sp., and most closely resembles taxa of the Charadrii (plovers, stilts, oystercatchers, and other “wader-like” shorebirds). Affinities to this clade were also supported by phylogenetic analyses, which placed the fossil as the sister taxon of either the Burhinidae or all crown group Charadrii. In addition, we identify specimens of the charadriiform-like taxon Scandiavis, which was before known only from the early Eocene Fur Formation in Denmark. Associated limb elements of two individuals are classified as Scandiavis cf. mikkelseni Bertelli et al., 2013, and remains of two further individuals are tentatively assigned to Scandiavis. The presence of a processus supracondylaris dorsalis on the previously unknown humerus corroborates charadriiform affinities of Scandiavis, whereas a plesiomorphic hypotarsus morphology indicates a position outside crown group Charadriiformes. Charadriisimilis essexensis is one of the earliest modern-type charadriiforms, and the holotype of the species is the most substantial early Paleogene fossil record of a charadriiform bird. Together with Scandiavis, as the best-represented taxon to be considered as a stem group charadriiform, it provides the basis for an improved understanding of the evolutionary history of charadriiform birds. UUID: http://zoobank.org/ca15ee81-09e8-4577-8beb-a362debf6636