Redescription of Parexus recurvus, an Early Devonian acanthodian from the Midland Valley of Scotland

Abstract

Parexus Agassiz was one of the first Early Devonian ‘spiny sharks’ to be described. The genus is readily recognized by the large size and ornament of its anterior dorsal fin spine. Although two species were erected, reappraisal of all known specimens indicate they should be synonymized in the type species Parexus recurvus. Farnellia tuberculata Traquair, originally described as a vertebral column, is actually tooth rows of jaw dentition, and is also now considered to be a junior synonym of P. recurvus. Parexus has a perichondrally ossified scapulocoracoid of typical acanthodian shape, and diagnostic features of the family Climatiidae, but has distinctive scales comprising appositional growth zones that closely resemble those of the putative stem chondrichthyan Seretolepis elegans Karatajute-Talimaa.

苏格兰Midland Valley早泥盆世棘鱼Parexus recurvus 的重新描述

Parexus recurvus 是将要描述的最早的早泥盆世“刺鲨鱼”的一种。该属因个体大和前背鳍刺的装饰而易于识别。虽然已建立了两个种,对所有已知标本的再审定表明它们应该是模式种Parexus recurvus 的同名种。原先被描述为脊柱的Farnellia tuberculata Traquair在此也认为是P. recurvus 的幼体同义名。Parexus 具有由软骨骨化的肩胛喙状骨,这是典型的棘鱼形状,也是科Climatiidae的鉴定特征;但它的鳞片很独特,具有同位生长带,与软骨鱼类Seretolepis elegans Karatajute-Talimaa的鳞片很相像。

Key words:

• Parexus
• Acanthodii
• Chondrichthyes
• Devonian
• Seretolepis
• Climatiidae
• stem gnathostome

View correction statement:

Erratum

Acknowledgements

CJB acknowledges the support of the Queensland Museum for providing basic support facilities and ESEM usage, and of an Australian Research Council Discovery Grant for 2010–2013. We thank Mike Taylor and Stig Walsh (NMS), Zerina Johanson (NHM), Mike Howe, Paul Shepherd and staff (BGS), David Lampard (DUNMG) and Garston Phillips and staff (WOSMG) for allowing access to and/or providing images of specimens in their collections. We are particularly grateful to Roger Jones for access to his collection, and his donation of material for our investigations. We would also like to thank reviewers Gavin Hanke and Zhu Min for their helpful comments. This is a contribution to IGCP Project 596: Climate change and biodiversity patterns in the mid-Palaeozoic.

Notes

This version has been corrected. Please see Erratum (http://dx.doi.org/10.1080/03115518.2013.824060).