Quantitative investigation of the diet of enantiornithines, the most diverse Mesozoic birds

Dr Ali, Jason Richard   (Co-Investigator (Co-I) (for projects led by other university))

Professor Wang Xiaoli   (Co-principal investigator)

Professor Zheng Xiaoting   (Co-principal investigator)

Dr Bevitt Joseph   (Co-principal investigator)

22

2021-08-09

2023-06-08

133344

Quantitative investigation of the diet of enantiornithines, the most diverse Mesozoic birds

early bird diet, finite element analysis, mechanical advantage, microwear, morphometrics

Others - Biological SciencesEarth Sciences

Biology and Medicine (M)

17105221

General Research Fund (GRF) 2021/22

2021

Completed

1 To improve understanding of diet in the most important group of Mesozoic birds. Enantiornithines are the most speciose and widespread birds of the Mesozoic era [1]. Recent studies have commented on their locomotion [2] and reproduction [3], but their diet remains entirely speculative [4]. Diet shapes the niche specialisation of organisms, determines the structure of food webs in communities, and underpins the structure of entire ecosystems [5]. Thus, without understanding their diet, the ecology of this key fossil group will remain unclear. We seek to remedy this situation by applying our novel framework of modern techniques to infer fossil diet. 2 To test and refine our novel framework for determining fossil bird diet to produce a fully tested gold standard. Seven lines of evidence (dental microwear, cervical muscle construction, body mass estimation, stable isotope geochemistry, traditional morphometrics, mechanical advantage modelling, and finite element analysis) have been proposed to reflect avialan diet, all using extant taxa as a reference (usually extant birds, extant lepidosaurian reptiles when comparing teeth). In this proposal, Avialae is defined as a clade that includes living birds and their closest fossil relatives: a stem-based taxon containing Passer domesticus (house sparrow) and all coelurosaurian dinosaurs closer to it than to Dromaeosaurus albertensis (dromaeosaurid) or Troodon formosus (troodontid) [6]. We expect the use of combined techniques to allow us to narrow the dietary possibilities more than any individual technique could, and to potentially identify unique feeding styles not present in modern birds (see Figure 1 for a summary). To date, a maximum of only two lines of evidence have ever been applied to any given fossil avialan. We will evaluate the efficacy of our proposed framework by observing whether, and if so how, it increases the specificity and confidence of diet assignment. The project will therefore result in a gold standard for understanding fossil bird diet for the foreseeable future. 3 To reconstruct ancestral bird diets. Living bird diets are extremely varied [7], but it is unclear when in the theropod lineage such variation emerged. The diet of the common ancestor of all birds is particularly contested [8-10], primarily because the diet of less than 5% of non-avian avialan taxa is known. In this proposal, Aves refers to crown birds only: living birds and all of their ancestors back to their most recent common ancestor [6]. Enantiornithines make up the majority of non-avian avialan taxa. We expect our study to more than double the number of data points in avialan diet ancestral state reconstruction. 4 To determine whether edentulism (tooth loss) was a driving force in the dietary diversity of modern birds. As nearly all enantiornithines were toothed [11], their diets will test the hypothesis that edentulism allowed modern birds to diversify their diets [12]. Dietary radiation(s) in the toothed enantiornithines would imply that beaks alone could not have led to the modern diversity in bird diets. 5 To advance understanding of Mesozoic ecosystems. Living birds are vital to understanding modern ecosystems owing to their role as indicator species and their rapid rates of species diversification and turnover [13]. By furthering our understanding of the ecology of enantiornithines (the closest Mesozoic analogues to modern bird diversity), as described in the first objective, we will also gain a much clearer picture of Mesozoic ecosystems. Enantiornithine inter- and intrageneric niche specialisation (the precise role each genus plays in the ecosystem) will be the main focus of study to identify the niche occupation range (i.e. set of niche specialisations across the entire group) of enantiornithines relative to modern birds. Additional palaeoecological information will be gathered and published as part of the study, notably information on the dental microwear and stable isotope geochemistry of other organisms in the Jehol biota as reference taxa.