A true caudal fin or not? New insights in the evolution of the gadiform caudal fin

Type Article
Date 2023-09
Language English
Author(s) Moritz TimoORCID1, 2, Walter Jacqueline2, Grunow BiankaORCID3, Thieme PhilippORCID1, 4
Affiliation(s) 1 : Deutsches Meeresmuseum , Katharinenberg 14–20, 18439 Stralsund , Germany
2 : Institute of Biological Sciences, University of Rostock , Albert-Einstein-Straße 3, 18059 Rostock , Germany
3 : Research Institute for Farm Animal Biology (FBN), Fish Growth Physiology , 18196 Dummerstorf , Germany
4 : MARBEC, Université de Montpellier, IRD , Ifremer, CNRS, cc093, Place E. Bataillon, 34095 Montpellier Cedex 05 , France
Source Zoological Journal Of The Linnean Society (0024-4082) (Oxford University Press (OUP)), 2023-09 , Vol. 199 , N. 1 , P. 26-44
DOI 10.1093/zoolinnean/zlad017
Keyword(s) Homology, morphology, ontogeny, osteology, Paracanthopterygii
Abstract

The distinctive caudal-fin skeleton of gadiforms has puzzled scientists for a long time, because of its many differences in comparison to other teleosts. Contradicting hypotheses interpreted this structure as (i) a highly derived teleostean caudal fin, (ii) a new formation with parts from the caudal, dorsal and anal fins, a so called pseudocaudal, or (iii) a complete evolutionary novelty, a so called neocaudal. To shed light on to this issue, the caudal-fin ontogeny of Lota lota was studied in detail. It differs from the development in non-gadiform teleostean taxa, e.g. by absence of a distinct and early notochord flexion. However, there are also many similarities with other teleosts, e.g. the caudal fin develops before the dorsal and anal fins. Furthermore, the morphology of adult caudal fins of all major gadiform families were studied and reviewed. Our results, in combination with the latest molecular phylogenies, allowed us to discuss the evolution of the gadiform caudal fin and resolve the origin of this highly debated character complex. Although their caudal-fin skeleton shows several derived apomorphies, the gadiform caudal fin is homologous to the caudal fins of other teleosts, without principal inclusion of dorsal- or anal-fin elements.

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