The origin of the face: how a 415-million-year-old armoured ”fish” (placoderm) bridges the gap between jawless and jawed vertebrates

Chairperson: professor Per Ahlberg

Representative of the Docentship Committee: professor Stefan Knight

Abstract: The human face is built just like that of any other jawed vertebrate (gnathostome): a nose with two nares sits in front of paired eyes, and above a mouth built up of upper and lower jaws. But there are vertebrates devoid of jaws, the cyclostomes, such as extant lampreys; their facial geometry is strikingly different from ours, with a single naris opening in a blind nasohypophyseal duct, located between the two eyes. These two different geometries are the consequences of different migration paths of cell populations in the vertebrate embryos. Relying only on extant forms fails to address the evolution from one face geometry to another. In other words, studying fossils forms is essential. In this lecture I will present the jawless and jawed fossil vertebrate diversity, and introduce key fossils such as a skull of Romundina, a small placoderm (fossil armoured fish) from the Canadian Arctic Archipelago. This specimen was scanned at high resolution, and its 3D modelled intracranial structures present a combination of jawed and jawless facial characteristics. Romundina thus bridges the gap between the two models of extant faces, allowing us to propose a step-wise evolutionary scenario regarding the origin of the jawed vertebrate face.

The lecture is an obligatory teaching test for those applying for admittance as docent and it should be possible for students and others with basic academic education in the relevant field to follow it. The lecture lasts 40-45 minutes with subsequent discussion. The lecture will be given in Swedish/English.