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2. The biodiversity of the Eocene Messel Pit

Author

Smith, Krister T., Collinson, Margaret, Folie, Annelise, Habersetzer, Jörg, Hennicke, Florian, Kothe, Erika, Lehmann, Thomas, Lenz, Olaf K., Mayr, Gerald, Micklich, Norbert, Rabenstein, Renate, Racicot, Rachel, Schaal, Stephan F. K., Smith, Thierry, Tosal, Aixa, Uhl, Dieter, Wappler, Torsten, Wedmann, Sonja, and Wuttke, Michael

Published
2024
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6. Variation in whale (Cetacea) inner ear anatomy reveals the early evolution of “specialized” high‐frequency hearing sensitivity.

Author

Racicot, Rachel A., Mourlam, Mickaël J., Ekdale, Eric G., Glass, Abigail, Marino, Lori, and Uhen, Mark D.

Subjects
*TOOTHED whales, *AQUATIC mammals, *EAR ossicles, *COMPUTED tomography, *CETACEA, *INNER ear
Abstract

As fully aquatic mammals, hearing is arguably the most important sensory component of cetaceans. Increasingly, researchers have been harnessing computed tomography (CT) to investigate the details of the inner ear as they can provide clues to the hearing abilities of whales. We use microCT scans of a broad sampling of the ear bones (periotics) of primarily toothed whales (Odontoceti) to investigate the inner ear bony labyrinth shape and reconstruct hearing sensitivities among these cetaceans, including several taxa about which little is currently known. We find support for sensitivity to the lower frequency spectrum in the archaeocete Zygorhiza kochii and an early toothed mysticete cf. Aetiocetus. Oligocene odontocetes (including one from our novel dataset), stem delphinidans, and two additional species of the long‐snouted eurhinodelphinids are found to have been able to hear within the narrow‐band high‐frequency spectrum (NBHF), which is thought to be a specialized form of hearing that evolved convergently multiple different times in extant groups to avoid predation by macroraptorial predators. Our results thus indicate that NBHF evolved as early as the Oligocene and certainly in stem delphinidans by the early Miocene, and thus may be an ancestral characteristic rather than a more recent innovation in select groups. [ABSTRACT FROM AUTHOR]

Published
2024
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7. The trace fossil record of the Nama Group, Namibia: Exploring the terminal Ediacaran roots of the Cambrian explosion

Author

Darroch, Simon A.F., Cribb, Alison T., Buatois, Luis A., Germs, Gerard J.B., Kenchington, Charlotte G., Smith, Emily F., Mocke, Helke, O’Neil, Gretchen R., Schiffbauer, James D., Maloney, Katie M., Racicot, Rachel A., Turk, Katherine A., Gibson, Brandt M., Almond, John, Koester, Bryce, Boag, Tom H., Tweedt, Sarah M., and Laflamme, Marc

Published
2021
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10. Ediacaran marine animal forests and the ventilation of the oceans

Author

Gutarra, Susana, Mitchell, Emily G, Dunn, Frances S, Gibson, Brandt M, Racicot, Rachel A, Darroch, Simon AF, Rahman, Imran, Gutarra, Susana, Mitchell, Emily G, Dunn, Frances S, Gibson, Brandt M, Racicot, Rachel A, Darroch, Simon AF, and Rahman, Imran

Abstract

The rise of animals across the Ediacaran–Cambrian transition marked a step-change in the history of life, from a microbially dominated world to the complex macroscopic biosphere we see today.1,2,3 While the importance of bioturbation and swimming in altering the structure and function of Earth systems is well established,4,5,6 the influence of epifaunal animals on the hydrodynamics of marine environments is not well understood. Of particular interest are the oldest “marine animal forests,”7 which comprise a diversity of sessile soft-bodied organisms dominated by the fractally branching rangeomorphs.8,9 Typified by fossil assemblages from the Ediacaran of Mistaken Point, Newfoundland,8,10,11 these ancient communities might have played a pivotal role in structuring marine environments, similar to modern ecosystems,7,12,13 but our understanding of how they impacted fluid flow in the water column is limited. Here, we use ecological modeling and computational flow simulations to explore how Ediacaran marine animal forests influenced their surrounding environment. Our results reveal how organism morphology and community structure and composition combined to impact vertical mixing of the surrounding water. We find that Mistaken Point communities were capable of generating high-mixing conditions, thereby likely promoting gas and nutrient transport within the “canopy.” This mixing could have served to enhance local-scale oxygen concentrations and redistribute resources like dissolved organic carbon. Our work suggests that Ediacaran marine animal forests may have contributed to the ventilation of the oceans over 560 million years ago, well before the Cambrian explosion of animals., Copyright © 2024 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). The linked document is the published version of the article., NHM Repository

Published
2024

12. Romaleodelphis pollerspoecki, gen. et sp. nov., an archaic dolphin from the Central Paratethys (Early Miocene, Austria).

Author

Sanchez-Posada, Catalina, Racicot, Rachel A., Ruf, Irina, Krings, Michael, and Rössner, Gertrud E.

Abstract

A new long-snouted homodont odontocete fossil from the Lower Miocene of Austria (ca. 22.5–22.0 Ma) is formally described and interpreted based on external skull characteristics supplemented by CT and µCT data. The specimen was found in deposits from the Central Paratethys and includes an incomplete and fragmented cranium and mandible as well as ear bones. It differs markedly from previously identified long-snouted archaic dolphins with single-rooted, homodont dentition, and thus is suggestive of a new taxon, for which the name Romaleodelphis pollerspoecki proposed. The geological context of R. pollerspoecki hints at a neritic habitat in close vicinity to estuarine environments. Romaleodelphis pollerspoecki shares key features with certain members of the so-called 'Chilcacetus clade' such as the widening of the premaxillae at the rostrum base and the absence of a deep lateral groove along the rostrum; however, a phylogenetic analysis reconstructs R. pollerspoecki in a polytomy with members of this 'clade' and a larger clade including many other taxa. To better understand the phylogenetic relationships of these taxa, comprehensive reexamination of Argryocetus and Macrodelphinus will be necessary. Measurements obtained through µCT-based internal anatomical reconstruction of the bony labyrinth indicate that R. pollerspoecki had the ability to hear specialized high-frequency signals similar to modern narrow-band high-frequency (NBHF) specialists. This work further identifies several extinct platanistoids as hearing within the NBHF spectrum, increasing the understanding of the diversity of ecological adaptations in early-diverging odontocetes and providing more examples of convergent evolution of this hearing type. [ABSTRACT FROM AUTHOR]

Published
2024
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14. The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

Author

Darroch, Simon AF, Gutarra Diaz, Susana V., Masaki, Hale, Olaru, Andrei, Gibson, Brandt M, Dunn, Frances S, Mitchell, Emily G, Racicot, Rachel A, Burzynski, Gregory, Rahman, Imran, Darroch, Simon AF, Gutarra Diaz, Susana V., Masaki, Hale, Olaru, Andrei, Gibson, Brandt M, Dunn, Frances S, Mitchell, Emily G, Racicot, Rachel A, Burzynski, Gregory, and Rahman, Imran

Abstract

Rangeomorphs are among the oldest putative eumetazoans known from the fossil record. Establishing how they fed is thus key to understanding the structure and function of the earliest animal ecosystems. Here, we use computational fluid dynamicstotesthypothesizedfeedingmodesforthefence-likerangeomorphPectinifrons abyssalis, comparing this to the morphologically similar extant carnivorous sponge Chondrocladia lyra. Our results reveal complex patterns of flow around P. abyssalis unlike those previously reconstructed for any other Ediacaran taxon. Comparisons with C. lyra reveal substantial differences between the two organisms, suggesting they converged on a similar fence-like morphology for different functions. We argue that the flow patterns recovered for P. abyssalis do not support either a suspension feeding or osmotrophic feeding habit. Instead, our results indicate that rangeomorph fronds may represent organs adapted for gas exchange. If correct, this interpretation could require a dramatic reinterpretation of the oldest macroscopic animals., Copyright. © 2023 The Author(s). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). The attached file is the published version of the article., NHM Repository

Published
2023

16. Contributors

Author

Acevedo-Gutiérrez, Alejandro, primary, Adam, Peter J., additional, Aguilar, Alex, additional, Amano, Masao, additional, Anderson, Paul K., additional, Archer, Frederick I., additional, Arnould, John P.Y., additional, Atkinson, Shannon, additional, Au, Whitlow W.L., additional, Aurioles-Gamboa, David, additional, Javier Aznar, F., additional, Baird, Robin W., additional, Baker, C. Scott, additional, Ballance, Lisa T., additional, Balbuena, Juan A., additional, Bannister, John L., additional, Barlow, Jay, additional, Barton, Sheri L., additional, Bearzi, Giovanni, additional, Beasley, Isabel, additional, Bekoff, Marc, additional, Ben-David, M., additional, Bengtson, John L., additional, Berta, Annalisa, additional, Bérubé, Martine, additional, Bester, Marthán N., additional, Bianucci, Giovanni, additional, Bjørge, Arne, additional, Black, Nancy A., additional, Bodkin, J.L., additional, Bonde, Robert K., additional, Borger, Jill, additional, Borrell, Asuncion, additional, Boveng, Peter, additional, Bowen, W.D., additional, Boyd, Ian L., additional, Braulik, Gillian T., additional, Brown, Alexander M., additional, Brownell, Robert L., additional, Buckland, Stephen T., additional, Burns, John J., additional, Cabrera, Andrea A., additional, Campagna, Claudio, additional, Cantor, Mauricio, additional, Cárdenas-Alayza, Susana, additional, Cárdenas-Hinojosa, Gustavo, additional, Castellini, Michael, additional, Cerchio, Salvatore, additional, Champagne, Cory D., additional, Chilvers, B. Louise, additional, Chivers, Susan J., additional, Cipriano, Frank, additional, Clapham, Phillip J., additional, Constantine, Rochelle, additional, Cooper, Lisa N., additional, Corkeron, Peter, additional, Costa, Daniel P., additional, Costidis, Alexander M., additional, Cowan, Daniel F., additional, Cranford, Ted, additional, Crespo, Enrique A., additional, Crocker, Daniel E., additional, Croll, Donald A., additional, da Silva, Vera M.F., additional, Danil, Kerri, additional, Darling, Jim, additional, Dawson, Stephen M., additional, de Muizon, Christian, additional, de Vos, Asha, additional, Dehnhardt, Guido, additional, DeMaster, Douglas P., additional, Deméré, Thomas A., additional, Dendrinos, Panagiotis, additional, Dill, Lawrence M., additional, Dizon, Andrew E., additional, L. Dolar, M. Louella, additional, Domning, Daryl P., additional, Donovan, G.P., additional, Dudzinski, Kathleen M., additional, Duffield, Deborah A., additional, Dyer, Michael P., additional, Ellis, Richard, additional, Eskelinen, Holli, additional, Estes, James A., additional, Evans, Peter G.H., additional, Fernández, Mercedes, additional, Fertl, Dagmar, additional, Fettuccia, Daniela de Castro, additional, Fiedler, Paul C., additional, Fish, Frank E., additional, Flores, Paulo A.C., additional, Forcada, Jaume, additional, Ford, John K.B., additional, Fordyce, R. Ewan, additional, Forestell, Paul H., additional, Forney, Karin A., additional, Fowler, Charles W., additional, Frankel, Adam S., additional, Friedlaender, Ari S., additional, Frohoff, Toni, additional, Frost, Kathryn J., additional, Galatius, Anders, additional, García-Vernet, Raquel, additional, Geisler, Jonathan H., additional, Gelatt, Thomas S., additional, Gentry, Roger, additional, George, J. Craig, additional, Gerrodette, Tim, additional, Goldbogen, Jeremy A., additional, Goldsworthy, Simon D., additional, P. Goodall, R. Natalie, additional, Goodman, Simon J., additional, Gregg, Justin D., additional, Hall, Ailsa J., additional, Hammill, Mike O., additional, Hammond, Philip S., additional, Hanke, Frederike D., additional, Hartman, Karin L., additional, Hazen, Elliott, additional, Heide-Jørgensen, M.P., additional, Heithaus, Michael R., additional, Herman, Louis M., additional, Herzing, Denise L., additional, Hewitt, Roger P., additional, Hindell, Mark A., additional, Hoelzel, A. Rus, additional, Hofmeyr, G. J. Greg, additional, Hohn, Aleta A., additional, Hooker, Sascha K., additional, Horstmann, Lara, additional, Horwood, Joseph, additional, Hoyt, Erich, additional, Hückstädt, Luis A., additional, Ivashchenko, Yulia V., additional, Iverson, Sara J., additional, Janik, Vincent M., additional, Jaramillo-Legorreta, Armando M., additional, Jefferson, Thomas A., additional, Jensen, Anne M., additional, Karamanlidis, Alexandros A., additional, Kasuya, Toshio, additional, Kato, Hidehiro, additional, Keith Diagne, Lucy W., additional, Kemp, Christopher, additional, Kemper, Catherine M., additional, Kenney, Robert D., additional, Kinze, Carl C., additional, Kirkman, Stephen P., additional, Kiszka, Jeremy J., additional, Koopman, Heather N., additional, Kooyman, Gerald L., additional, Kovacs, Kit M., additional, Kraus, Scott D., additional, Krysl, Petr, additional, Laidre, Kristin L., additional, Laitman, Jeffrey T., additional, Lambert, Olivier, additional, Landry, André M., additional, Lavigne, David M., additional, LeDuc, Rick, additional, Lipsky, Jessica D., additional, Littnan, Charles, additional, Loughlin, Thomas R., additional, Lowry, Lloyd, additional, Lowther, Andrew D., additional, Lydersen, Christian, additional, Maas, Mary C., additional, MacLean, Stephen A., additional, MacLeod, Colin D., additional, Mallette, Sarah D., additional, Mann, Janet, additional, Maresh, Jennifer L., additional, Marsh, Helene, additional, Marshall, Christopher D., additional, Martin, Anthony R., additional, Mass, Alla M., additional, McAlpine, Donald F., additional, Chris McKnight, J., additional, McLellan, William A., additional, Mead, James G., additional, Melin, Sharon R., additional, Merrick, Richard, additional, Mesnick, Sarah L., additional, Miller, Edward H., additional, Miller, Lance J., additional, Miller, Patrick J.O., additional, Miyazaki, Nobuyuki, additional, Moore, Jeffrey E., additional, Moore, Kathleen M., additional, Moore, Michael, additional, Moore, Sue E., additional, Moors-Murphy, Hilary B., additional, Morin, Phillip A., additional, Newman, William A., additional, Newton, Kelly M., additional, Nieto-García, Edwyna, additional, Northridge, Simon, additional, Nummela, Sirpa, additional, O'Brien, Justine K., additional, O'Corry-Crowe, Gregory M., additional, Olsen, Morten T., additional, Olson, Paula A., additional, Oppenheimer, Jonas, additional, Orbach, Dara N., additional, Ortiz, Rudy M., additional, Pabst, D. Ann, additional, Palsbøll, Per J., additional, Parra, Guido J., additional, Patterson, Eric, additional, Paves-Hernández, Héctor, additional, Perrin, William F., additional, Perryman, Wayne L., additional, Pitman, Robert, additional, Pomeroy, Patrick P., additional, Ponganis, Paul J., additional, Powell, James A., additional, Pyenson, Nicholas D., additional, Racicot, Rachel, additional, Raga, J. Antonio, additional, Ralls, Katherine, additional, Raverty, Stephen, additional, Read, Andrew J., additional, Reeves, Randall R., additional, Regehr, Eric V., additional, Reggente, Melissa A.L., additional, Reidenberg, Joy S., additional, Reijnders, Peter J.H., additional, Reyes, Julio C., additional, Reynolds, John E., additional, Robeck, Todd R., additional, Robinson, Kelly J., additional, Rode, Karyn, additional, Rogers, Tracey, additional, Rojas-Bracho, Lorenzo, additional, Roman, Joe, additional, Rommel, Sentiel A., additional, Roos, Marjoleine M.H., additional, Rosel, Patricia E., additional, Rowntree, Victoria J., additional, Rugh, David, additional, Russell, Debbie J.F., additional, Sayigh, Laela S., additional, Scolardi, Kerri M., additional, Scott, Michael D., additional, Sears, Richard, additional, Seger, Jon, additional, Sharp, Sarah, additional, Sheehan, Glenn W., additional, Silber, Gregory K., additional, Simeone, Claire A., additional, Smith, Brian D., additional, Southall, Brandon L., additional, Spitz, Jérôme, additional, Spoor, Fred, additional, Stacey, Rita, additional, Staniland, Iain J., additional, Steel, Debbie, additional, Stern, S. Jonathan, additional, Stewart, Brent S., additional, Supin, Alexander Y., additional, Suydam, R., additional, Swartz, Steven L., additional, Teilmann, Jonas, additional, Tershy, Bernie R., additional, Thewissen, J.G.M., additional, Tinker, M.T., additional, Tolley, Krystal A., additional, Trillmich, Fritz, additional, Trites, Andrew W., additional, Turner, Ted, additional, Twiss, Sean D., additional, Tyack, Peter L., additional, Uhen, Mark D., additional, Van Franeker, Jan A., additional, Van Waerebeek, Koen, additional, Wade, Paul R., additional, Wang, John Y., additional, Weller, David W., additional, Wells, Randall S., additional, Werth, Alexander J., additional, Whitehead, Hal, additional, Williams, Terrie M., additional, Würsig, Bernd, additional, Yablokov, Alexey V., additional, Yamada, Tadasu K., additional, Yamato, Maya, additional, Yochem, Pamela K., additional, York, Anne E., additional, and Zhou, Kaiya, additional

Published
2018
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19. Cetology: The bare 'jaw' bones of whale evolution.

Author

Racicot, Rachel and Smith, Chris

Subjects
*JAWS, *OCEAN, *WHALES
Abstract

Whale jaws are essential for both feeding and underwater hearing since the earliest 'walking' whales returned to the oceans. Over ∼50 million years of subsequent evolution have morphed the whale jaw into extreme shapes, but the hearing region remains conserved due to its critical acoustic functions. [ABSTRACT FROM AUTHOR]

Published
2024
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20. The life and times of Pteridinium simplex

Author

Darroch, Simon AF, Gibson, Brandt M, Syversen, Maggie, Rahman, Imran, Racicot, Rachel A, Dunn, Frances S, Gutarra Diaz, Susana V., Schindler, Eberhard, Wehrmann, Achim, Laflamme, Marc, Darroch, Simon AF, Gibson, Brandt M, Syversen, Maggie, Rahman, Imran, Racicot, Rachel A, Dunn, Frances S, Gutarra Diaz, Susana V., Schindler, Eberhard, Wehrmann, Achim, and Laflamme, Marc

Abstract

Pteridinium simplex is an iconic erniettomorph taxon best known from late Ediacaran successions in South Australia, Russia, and Namibia. Despite nearly 100 years of study, there remain fundamental questions surrounding the paleobiology and paleoecology of this organism, including its life position relative to the sediment–water interface, and how it fed and functioned within benthic communities. Here, we combine a redescription of specimens housed at the Senckenberg Forschungsinstitut und Naturmuseum Frankfurt with field observations of fossiliferous surfaces, to constrain the life habit of Pteridinium and gain insights into the character of benthic ecosystems shortly before the beginning of the Cambrian. We present paleontological and sedimentological evidence suggesting that Pteridinium was semi-infaunal and lived gregariously in aggregated communities, preferentially adopting an orientation with the long axis perpendicular to the prevailing current direction. Using computational fluid dynamics simulations, we demonstrate that this life habit could plausibly have led to suspended food particles settling within the organism's central cavity. This supports interpretation of Pteridinium as a macroscopic suspension feeder that functioned similarly to the coeval erniettomorph Ernietta, emblematic of a broader paleoecological shift toward benthic suspension-feeding strategies over the course of the latest Ediacaran. Finally, we discuss how this new reconstruction of Pteridinium provides information concerning its potential relationships with extant animal groups and state a case for reconstructing Pteridinium as a colonial metazoan., Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/ licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited., NHM Repository

Published
2022

21. The life and times of Pteridinium simplex

Author

Darroch, Simon A. F., primary, Gibson, Brandt M., additional, Syversen, Maggie, additional, Rahman, Imran A., additional, Racicot, Rachel A., additional, Dunn, Frances S., additional, Gutarra, Susana, additional, Schindler, Eberhard, additional, Wehrmann, Achim, additional, and Laflamme, Marc, additional

Published
2022
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24. Lagomorpha as a Model Morphological System

Author

Kraatz, Brian, primary, Belabbas, Rafik, additional, Fostowicz-Frelik, Łucja, additional, Ge, De-Yan, additional, Kuznetsov, Alexander N., additional, Lang, Madlen M., additional, López-Torres, Sergi, additional, Mohammadi, Zeinolabedin, additional, Racicot, Rachel A., additional, Ravosa, Matthew J., additional, Sharp, Alana C., additional, Sherratt, Emma, additional, Silcox, Mary T., additional, Słowiak, Justyna, additional, Winkler, Alisa J., additional, and Ruf, Irina, additional

Published
2021
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28. Intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena) and its implications for comparative studies across odontocetes

Author

Martins, Maria Clara Iruzun, Park, Travis, Racicot, Rachel, Cooper, N, Martins, Maria Clara Iruzun, Park, Travis, Racicot, Rachel, and Cooper, N

Abstract

In morphological traits, variation within species is generally considered to be lower than variation among species, although this assumption is rarely tested. This is particularly important in fields like palaeontology, where it is common to use a single individual as representative of a species due to the rarity of fossils. Here, we investigated intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena). Interspecific variation of cochlear morphology is well characterised among odontocetes (toothed whales) because of the importance of the structure in echolocation, but generally these studies use only a single cochlea to represent each species. In this study we compare variation within the cochleae of 18 specimens of P. phocoena with variations in cochlear morphology across 51 other odontocete species. Using both 3D landmark and linear measurement data, we performed Generalised Procrustes and principal component analyses to quantify shape variation. We then quantified intraspecific variation in our sample of P. phocoena by estimating disparity and the coefficient of variation for our 3D and linear data respectively. Finally, to determine whether intraspecific variation may confound the results of studies of interspecific variation, we used multivariate and univariate analyses of variance to test whether variation within the specimens of P. phocoena was significantly lower than that across odontocetes. We found low levels of intraspecific variation in the cochleae of P. phocoena, and that cochlear shape within P. phocoena was significantly less variable than across odontocetes. Although future studies should attempt to use multiple cochleae for every species, our results suggest that using just one cochlea for each species should not strongly influence the conclusions of comparative studies if our results are consistent across Cetacea.

Published
2020

29. Bony labyrinths of the blackfish (Delphinidae: Globicephalinae).

Author

Racicot, Rachel A. and Preucil, V. Eve

Subjects
DELPHINIDAE, NARWHAL, KILLER whale, WHITE whale, SKULL morphology, MARINE mammals, BOTTLENOSE dolphin
Abstract

Bony labyrinth morphology varies across marine mammals and contains key information regarding hearing sensitivity and ecology. The hearing ranges of globicephaline (Delphinidae: Globicephalinae) or melon‐headed dolphins, known as "Blackfish," have been extensively studied using acoustic technologies, but clade‐wide morphological analysis of the bony labyrinth is lacking. In this study, we investigate the variation in hearing‐relevant bony labyrinth morphology within globicephalines using μCT scans of isolated petrosals and digitally isolating the bony labyrinth of all species. Principal components analysis (PCA) of nine hearing‐relevant measurements of the cochlea alongside a broader sampling of terrestrial and aquatic artiodactyls shows Orcaella brevirostris and other globicephalines with higher levels of facial asymmetry and potentially more specialized echolocation abilities plotting near Monodon monoceros, Delphinapterus leucas, and Orcinus orca. The remaining globicephalines, which have more symmetrical skulls and other unique and acoustically relevant attributes, plotted towards the middle of the echolocating odontocete portion of the PCA. Our analysis thus reveals that inner ear morphology may correlate with both facial skull morphology and echolocation specializations, as these are intertwined. Furthermore, this study illustrates how morphological analyses, especially those centered on hearing, may provide critical conservation‐relevant information as direct access to audiograms becomes less tenable. [ABSTRACT FROM AUTHOR]

Published
2022
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37. Intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena) and its implications for comparative studies across odontocetes.

Author

Iruzun Martins, Maria Clara, Park, Travis, Racicot, Rachel, and Cooper, Natalie

Subjects
HARBOR porpoise, COCHLEA, COMPARATIVE studies, CETACEA, UNIVARIATE analysis
Abstract

In morphological traits, variation within species is generally considered to be lower than variation among species, although this assumption is rarely tested. This is particularly important in fields like palaeontology, where it is common to use a single individual as representative of a species due to the rarity of fossils. Here, we investigated intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena). Interspecific variation of cochlear morphology is well characterised among odontocetes (toothedwhales) because of the importance of the structure in echolocation, but generally these studies use only a single cochlea to represent each species. In this study we compare variation within the cochleae of 18 specimens of P. phocoenawith variations in cochlearmorphology across 51 other odontocete species. Using both 3D landmark and linear measurement data, we performed Generalised Procrustes and principal component analyses to quantify shape variation. We then quantified intraspecific variation in our sample of P. phocoena by estimating disparity and the coefficient of variation for our 3D and linear data respectively. Finally, to determine whether intraspecific variation may confound the results of studies of interspecific variation, we used multivariate and univariate analyses of variance to test whether variation within the specimens of P. phocoena was significantly lower than that across odontocetes. We found low levels of intraspecific variation in the cochleae of P. phocoena, and that cochlear shape within P. phocoena was significantly less variable than across odontocetes. Although future studies should attempt to use multiple cochleae for every species, our results suggest that using just one cochlea for each species should not strongly influence the conclusions of comparative studies if our results are consistent across Cetacea. [ABSTRACT FROM AUTHOR]

Published
2020
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47. Evolution of narrow band - high frequency hearing in odontocetes

Author

Miller, Lee A., Galatius, Anders, Olsen, Morten Tange, Racicot, Rachel Ann, and Steeman, Mette

Abstract

Whale biologists generally agree that predation by killer whales provided selection pressure for driving up the biosonar frequencies of some odontocetes. This made the signals of these species, like the harbor porpoise, less audible to their predator. But why should the acoustic signals of 13 to 15 known species in four families have peak frequencies between 120 kHz and 140 kHz? We propose and argue that at these frequencies an ambient noise minimum exists and has so over the past 10 million years or more. The spectral properties of the signals produced by smaller odontocetes, like the harbor porpoise, have thus been shaped by predation pressure from larger odontocetes, driving the frequency up, and limited by increasing ambient noise above about 140 kHz. The result is a high frequency, narrow band acoustic signal. To support the above conclusions we use palæontological, palæoclimatic, anatomical and phylogenetic data.

Published
2015

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