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Teeth are a key innovation underpinning the adaptive radiation of jawed vertebrates. They are a synapomorphy of gnathostomes, but the evolutionary origin of teeth must lie deeper within the jawless vertebrates. Jawless vertebrates comprise the extant groups of lampreys and hagfish and the extinct intermediate stem-gnathostomes, which possess a variety of tooth-like structures and denticles. To test among different hypotheses of tooth evolution, we must study the development and function of these tooth-like structures in jawless vertebrates. For this I use a combination of computational methods including Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA), micro-CT (computed tomography) and synchrotron-radiation X-ray tomographic microscopy (srXTM). I investigate the oral plates of heterostracans, one of the earliest skeletonising vertebrates. Using CFD and FEA I test functional hypotheses of suspension feeding and mechanical feeding and show that the oral plates performed a mechanical function. Using srXTM I study histology and morphogenesis of the oral plates and denticles and reveal that they are developmentally linked to the dermal skeleton, supporting the ‘outside-in’ hypothesis of tooth evolution. I show that the oral plate denticles are non-homologous to gnathostome teeth and that the capacity to form internal odontodes evolved several times independently in stem-gnathostomes. Adding to the fossil perspective I present foundational work on the development of lamprey toothlets. Using micro-CT and srXTM I describe toothlet replacement at tissue level and show that replacement is a conserved feature of the lamprey crown group. Comparing lamprey toothlet development and replacement to hagfish and gnathostomes, I lay the foundation for future investigations into the genetic regulation of tooth development across vertebrate lineages. Using a multifaceted computational approach this thesis sheds light on the function and development of tooth-like struct

Coralline algae play important ecological roles throughout the photic zone of the world’s oceans. Recent studies have shown that attached-living coralline algae can contain records of past climate variability. So far, algal-based paleo-reconstructions are mainly available from mid- to high-latitudes, while in low latitude and temperate regions only few examples exist. Here, we investigate samples from the attached-living encrusting coralline algal species Neogoniolithon hauckii (Rothpletz) R.A Townsend & Huisman [= Neogoniolithon mamillosum (Hauck) Setchell & L.R. Mason, nom illeg.] from a temperate site in the Mediterranean Sea to assess its potential as an environmental recorder. The specimens were collected at different water depths (20 and 40 m) in the Columbretes Islands (Spain). Sclerochronological analysis of sectioned samples revealed seasonal growth patterns. Mg/Ca, Li/Ca, and Ba/Ca ratios were measured in the algal skeletons using laser ablation inductively coupled mass spectrometry (LA-ICP-MS) in ultra-high resolution. We report a mean vertical extension rate of 1.1 to 1.2 mm/year (based on analysis of Mg/Ca cycles in 40 m and 20 m samples), representing the first growth rate measurement for this species. In addition, subannual banding patterns were mapped, measured, and could be linked to high frequency variability in laser-analyzed Mg/Ca ratios. Elemental ratios analyzed in Neogoniolithon hauckii were compared to in situ water temperatures measured at the water depth of sample collection. Our results show significant positive relationships between algal Mg/Ca (R=0.55) as well as Li/Ca ratios (R=0.46) and in situ measured temperature data (40 m specimen). Ba/Ca ratios show no significant correlation to temperature and may be influenced by other factors. These data suggest potential of this species for climate reconstructions in warm-temperate regions as Neogoniolithon hauckii is not only widely distributed in the Mediterranean, but also one of th

Coralline algae play important ecological roles throughout the photic zone of the world’s oceans. Recent studies have shown that attached-living coralline algae can contain records of past climate variability. So far, algal-based paleo-reconstructions are mainly available from mid- to high-latitudes, while in low latitude and temperate regions only few examples exist. Here, we investigate samples from the attached-living encrusting coralline algal species Neogoniolithon hauckii (Rothpletz) R.A Townsend & Huisman [= Neogoniolithon mamillosum (Hauck) Setchell & L.R. Mason, nom illeg.] from a temperate site in the Mediterranean Sea to assess its potential as an environmental recorder. The specimens were collected at different water depths (20 and 40 m) in the Columbretes Islands (Spain). Sclerochronological analysis of sectioned samples revealed seasonal growth patterns. Mg/Ca, Li/Ca, and Ba/Ca ratios were measured in the algal skeletons using laser ablation inductively coupled mass spectrometry (LA-ICP-MS) in ultra-high resolution. We report a mean vertical extension rate of 1.1 to 1.2 mm/year (based on analysis of Mg/Ca cycles in 40 m and 20 m samples), representing the first growth rate measurement for this species. In addition, subannual banding patterns were mapped, measured, and could be linked to high frequency variability in laser-analyzed Mg/Ca ratios. Elemental ratios analyzed in Neogoniolithon hauckii were compared to in situ water temperatures measured at the water depth of sample collection. Our results show significant positive relationships between algal Mg/Ca (R=0.55) as well as Li/Ca ratios (R=0.46) and in situ measured temperature data (40 m specimen). Ba/Ca ratios show no significant correlation to temperature and may be influenced by other factors. These data suggest potential of this species for climate reconstructions in warm-temperate regions as Neogoniolithon hauckii is not only widely distributed in the Mediterranean, but also one of the few sp