Palaeobiology and flight capacity of volant palaeognaths (Pan-Palaeognathae: Lithornithidae): implications for the common ancestor of extant palaeognaths and early crown birds

Extant palaeognathous bird diversity comprises the flightless ratites (ostriches, rhea, kiwi, cassowaries, and emu), as well as the partridge-like tinamous that fly powerfully over short distances. As the sister clade of all other crown birds (Neognathae), insight into the biology of early palaeognaths may help clarify the biological attributes of the ancestral crown bird and clarify numerous outstanding macroevolutionary conundrums such as the flight and dispersal capacity of ratite ancestors. In a thorough review of the palaeognath fossil record (Chapter 2), I conclude that a group of apparently volant palaeognaths from the Paleogene, the lithornithids, may hold the key to addressing these questions. In the remainder of this thesis, I make use of high-resolution CT scanning to investigate the morphology of lithornithids, and use this information to explore several aspects of early palaeognath palaeobiology. Chapter 3 is an investigation into the previously undescribed neurocranium, brain endocast, and endosseous labyrinth of the Lithornis vulturinus neotype that had hitherto not been published on. The endocast of L. vulturinus may provide the clearest insights to date into the neuroanatomy of early crown group birds, combining an ancestrally unflexed brain with a moderately enlarged telencephalon and enlarged optic lobes. In Chapter 4, I redescribe the L. vulturinus neotype, providing new information gleaned from CT scans of the specimen, and additionally provide a description of a new L. vulturinus fossil specimen from near the type locality. While this new information does not resolve species relationships within Lithornithidae, it may prove useful in identifying additional lithornithids in the fossil record. In Chapter 5, I quantitatively investigated the flight capabilities and ecology of Lithornis promiscuus using geometric morphometric analysis of the sternum, a method that effectively predicts these traits in extant birds. Geometric morphometric analysis is not only consistent with aerobic continuous flapping flight while rejecting burst flight, but also demonstrates that among extant birds the sternum of Lithornis promiscuus is similar to taxa capable of long-distance flight, providing insight into the potential dispersive capabilities of early palaeognaths, with implications for unravelling puzzling aspects of their historical biogeography. Taken together, these new insights into the biology of early palaeognaths corroborate interpretations of lithornithids as ground feeding birds with “modern” neuroanatomy that were capable long-distance fliers and contribute substantial new insight into the probable nature of the ancestral crown group bird.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Widrig, Klara

Advisor dc:contributor.advisor

• Field, Daniel

• Palaeognathae
• Lithornithidae
• avian evolution
• vertebrate palaeontology

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/ff6a7fdc-6ba0-4a3d-9a3f-31b4d25c2c80/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.114349

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/377580