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RESEARCH ARTICLE
Contents Vol 107(3)

The digital tendon locking mechanism of owls: variation in the structure and arrangement of the mechanism and functional implications

Luke Einoder A B and Alastair Richardson A
+ Author Affiliations
- Author Affiliations

A School of Zoology, University of Tasmania, Private Bag 05, Hobart, Tas. 7001, Australia.

B Present address: School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.

C Corresponding author. Email: lukeeinoder@hotmail.com

Emu 107(3) 223-230 https://doi.org/10.1071/MU06019
Submitted: 11 May 2006  Accepted: 10 July 2007   Published: 7 September 2007

Abstract

This study provides evidence of morphological differences in support of the current phylogenetic division of the owls into two familes (Strigidae, Tytonidae), with respect to the digital tendon locking mechanism (TLM). This mechanism consists of modified surfaces on the flexor tendons in the digits, which, when engaged form a lock that holds the digits in a flexed position. Although species-specific differences in TLM structure were apparent, consistent inter-family differences occurred in the degree of expression of the TLM, its location within the digit, and in the structure and arrangement of the locking elements. Phylogenetic differences also occurred in the location of the associated digital ligaments. The TLM of the Strigidae was found to resemble that of the Falconiformes (Falconidae and Accipitridae). However, the Tytonidae possess a more distinctive pattern, characterised by a digit 1 TLM located at the opposite end of the digit and bearing reversed plicae. The biomechanics of the mechanism are considered, along with the functional implications of the varying structures in an attempt to understand the adaptiveness, or otherwise, of this-little known structure within an avian order.


Acknowledgements

We wish to thank Nick Mooney of the Department of Primary Industry Water and Environment (Tasmania) for suggesting this topic as an interesting area of research, and for providing an insight into the ecological significance of particular hindlimb structures. Also to Nick, thank you for comments on early drafts of this manuscript, and for providing many of the specimens used. Jason Wiersma provided much inspiration for the authors into the study of raptor ecology, for which this work owes a great deal. Thanks to Judy Rainbird of the Queen Victoria Museum, Tasmania, and Walter Boles of the Australian Museum, Sydney, who also kindly provided specimens. We would like to thank Ian Norman, of the Arthur Rylah Institute, Department of Sustainability and Environment, Victoria, for assistance with editing. Thanks also to the editors of Emu, whose comments and suggestions were greatly appreciated.


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