TESTING EUCONODONT GROWTH MODELS USING A COLLECTION OF PATHOLOGICAL SPECIMENS

Conodonts are the first vertebrates to have developed biomineralized, enamel-like hard tissues. These tissues resemble vertebrate tooth enamel structurally and in terms of functional adaptations; but are unique, as they possess the ability to repair both fractures and surface scores that occur during normal function. Euconodonts are the most highly derived group of conodonts and grew in a series of concentric layers deposited on the outer surface of the element, allowing the teeth to continuously grow throughout the life of the animal. Two competing models of conodont growth are tested 1) retraction of elements into epithelial pockets and 2) periodical growth of biomineral-secreting tissues encapsulating the entire element. Pathological growth and malformations can provide an insight into the mechanism of biomineralisation of these teeth and reveal new histological features that have previously been unknown. A selection of abnormally developed conodonts from the Silurian of Sweden are examined and confronted with previously proposed growth models to shed new light on this unique invention in the history of biomineralization.