Unravelling the ontogeny of a Devonian early gnathostome, the “acanthodian” Triazeugacanthus affinis (eastern Canada)

PeerJ

Jean-Yves Sire¹  Richard Cloutier²  Marion Chevrinais² 

[1] CNRS—UMR 7138-Evolution Paris-Seine IBPS, Université Pierre et Marie Curie, Paris, France;Laboratoire de Paléontologie et Biologie évolutive, Université du Québec à Rimouski, Rimouski, Canada;

关键词: Gnathostomata;    Acanthodii;    Mineralization;    Developmental trajectory;    Ossification sequence;   

DOI  :  10.7717/peerj.3969

来源: DOAJ

【 摘 要 】

The study of vertebrate ontogenies has the potential to inform us of shared developmental patterns and processes among organisms. However, fossilised ontogenies of early vertebrates are extremely rare during the Palaeozoic Era. A growth series of the Late Devonian “acanthodian” Triazeugacanthus affinis, from the Miguasha Fossil-Fish Lagerstätte, is identified as one of the best known early vertebrate fossilised ontogenies given the exceptional preservation, the large size range, and the abundance of specimens. Morphological, morphometric, histological and chemical data are gathered on a growth series of Triazeugacanthus ranging from 4 to 52 mm in total length. The developmental trajectory of this Devonian “acanthodian” is characteristic of fishes showing a direct development with alternating steps and thresholds. Larvae show no squamation but a progressive appearance of cartilaginous neurocranial and vertebral elements, and appendicular elements, whereas juveniles progress in terms of ossification and squamation. The presence of cartilaginous and bony tissues, discriminated on histological and chemical signatures, shows a progressive mineralisation of neurocranial and vertebral elements. Comparison among different body proportions for larvae, juveniles and adults suggest allometric growth in juveniles. Because of the phylogenetic position of “acanthodians”, Triazeugacanthus ontogeny informs us about deep time developmental conditions in gnathostomes.

【 授权许可】

Unknown