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Origin of euconodont elements

Published online by Cambridge University Press:  20 May 2016

Hubert Szaniawski
Affiliation:
Instytut Paleobiologii PAN, Al. Żwirki i Wigury 93, PL-02-089 Warszawa, Poland
Stefan Bengtson
Affiliation:
Institute of Palaeontology, Box 558, S-751 22 Uppsala, Sweden

Abstract

Primitive euconodont elements from the Upper Cambrian of Sweden are investigated histologically and compared with co-occurring elements of paraconodonts. The proposed close relationship between the two groups is confirmed. Typical euconodont and paraconodont elements are bridged by intermediate forms. The ontogenetic development of the early euconodont elements shows striking similarities to the evolutionary development from paraconodonts to euconodonts, suggesting that evolution generally followed a peramorphic pattern (“recapitulation”). The conodont crown originated through extension of the growth lamellae around the whole element, accompanied by stronger mineralization. The first denticulation in Proconodontus arose when a jagged posterior edge in juvenile specimens was enhanced by the subsequent deposition of growth lamellae, a process comparable to the regeneration of broken tips. The most primitive euconodont elements probably erupted from the epithelium earlier in ontogeny than in more advanced forms. After the appearance of the phosphatic crown, conodont elements underwent a very rapid morphological differentiation. Cordylodus may have arisen from Proconodontus serratus.

Type
Research Article
Copyright
Copyright © The Paleontological Society 

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