A bony connection signals laryngeal echolocation in bats
Nina Veselka1, David D. McErlain2,3, David W. Holdsworth2,4, Judith L. Eger5, Rethy K. Chhem6,7, Matthew J. Mason8, Kirsty L. Brain8, Paul A. Faure9 & M. Brock Fenton1
1. Department of Biology,
2. Imaging Research Laboratories, Robarts Research Institute,
3. Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5B7, Canada
4. Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5K8, Canada
5. Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario M5S 2C6, Canada
6. Department of Radiology, Medical University of Vienna, Division of Human Health, 1090 Vienna, Austria
7. Division of Human Health, International Atomic Energy Agency, Wagramer Strasse 5, PO Box 200, 1400 Vienna, Austria
8. Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
9. Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, Ontario L8S 4K1, Canada
Correspondence to: M. Brock Fenton1 Correspondence and requests for materials should be addressed to M.B.F (Email: bfenton@uwo.ca).
Echolocation is an active form of orientation in which animals emit sounds and then listen to reflected echoes of those sounds to form images of their surroundings in their brains1. Although echolocation is usually associated with bats, it is not characteristic of all bats2, 3. Most echolocating bats produce signals in the larynx, but within one family of mainly non-echolocating species (Pteropodidae), a few species use echolocation sounds produced by tongue clicks4, 5. Here we demonstrate, using data obtained from micro-computed tomography scans of 26 species (n = 35 fluid-preserved bats), that proximal articulation of the stylohyal bone (part of the mammalian hyoid apparatus) with the tympanic bone always distinguishes laryngeally echolocating bats from all other bats (that is, non-echolocating pteropodids and those that echolocate with tongue clicks). In laryngeally echolocating bats, the proximal end of the stylohyal bone directly articulates with the tympanic bone and is often fused with it. Previous research on the morphology of the stylohyal bone in the oldest known fossil bat (Onychonycteris finneyi) suggested that it did not echolocate6, but our findings suggest that O. finneyi may have used laryngeal echolocation because its stylohyal bones may have articulated with its tympanic bones. The present findings reopen basic questions about the timing and the origin of flight and echolocation in the early evolution of bats. Our data also provide an independent anatomical character by which to distinguish laryngeally echolocating bats from other bats.
Correspondence to: M. Brock Fenton1 Correspondence and requests for materials should be addressed to M.B.F (Email: bfenton@uwo.ca).
Echolocation is an active form of orientation in which animals emit sounds and then listen to reflected echoes of those sounds to form images of their surroundings in their brains1. Although echolocation is usually associated with bats, it is not characteristic of all bats2, 3. Most echolocating bats produce signals in the larynx, but within one family of mainly non-echolocating species (Pteropodidae), a few species use echolocation sounds produced by tongue clicks4, 5. Here we demonstrate, using data obtained from micro-computed tomography scans of 26 species (n = 35 fluid-preserved bats), that proximal articulation of the stylohyal bone (part of the mammalian hyoid apparatus) with the tympanic bone always distinguishes laryngeally echolocating bats from all other bats (that is, non-echolocating pteropodids and those that echolocate with tongue clicks). In laryngeally echolocating bats, the proximal end of the stylohyal bone directly articulates with the tympanic bone and is often fused with it. Previous research on the morphology of the stylohyal bone in the oldest known fossil bat (Onychonycteris finneyi) suggested that it did not echolocate6, but our findings suggest that O. finneyi may have used laryngeal echolocation because its stylohyal bones may have articulated with its tympanic bones. The present findings reopen basic questions about the timing and the origin of flight and echolocation in the early evolution of bats. Our data also provide an independent anatomical character by which to distinguish laryngeally echolocating bats from other bats.
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