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Darroch SA, Gutarra S, Masaki H, Olaru A, Gibson BM, Dunn FS, Mitchell EG, Racicot RA, Burzynski G, Rahman IA. The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life. iScience 2023; 26:105989. [PMID: 36756377 PMCID: PMC9900436 DOI: 10.1016/j.isci.2023.105989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 12/06/2022] [Accepted: 01/12/2023] [Indexed: 01/18/2023] Open
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 dynamics to test hypothesized feeding modes for the fence-like rangeomorph Pectinifrons 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.
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Affiliation(s)
- Simon A.F. Darroch
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Evolutionary Studies Institute, Vanderbilt University, Nashville, TN 37235, USA,Senckenberg Research Institute and Natural History Museum Frankfurt, 60325 Frankfurt, Germany
| | | | - Hale Masaki
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA
| | - Andrei Olaru
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA
| | - Brandt M. Gibson
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Department of Chemistry and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Frances S. Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Emily G. Mitchell
- Department of Zoology, Museum of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Rachel A. Racicot
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Evolutionary Studies Institute, Vanderbilt University, Nashville, TN 37235, USA,Senckenberg Research Institute and Natural History Museum Frankfurt, 60325 Frankfurt, Germany
| | - Gregory Burzynski
- Department of Biology, Fairfield University, Fairfield, CT 06824, USA
| | - Imran A. Rahman
- The Natural History Museum, London SW7 5BD, UK,Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK,Corresponding author
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Kraatz B, Belabbas R, Fostowicz-Frelik Ł, Ge DY, Kuznetsov AN, Lang MM, López-Torres S, Mohammadi Z, Racicot RA, Ravosa MJ, Sharp AC, Sherratt E, Silcox MT, Słowiak J, Winkler AJ, Ruf I. Lagomorpha as a Model Morphological System. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.636402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Due to their global distribution, invasive history, and unique characteristics, European rabbits are recognizable almost anywhere on our planet. Although they are members of a much larger group of living and extinct mammals [Mammalia, Lagomorpha (rabbits, hares, and pikas)], the group is often characterized by several well-known genera (e.g., Oryctolagus, Sylvilagus, Lepus, and Ochotona). This representation does not capture the extraordinary diversity of behavior and form found throughout the order. Model organisms are commonly used as exemplars for biological research, but there are a limited number of model clades or lineages that have been used to study evolutionary morphology in a more explicitly comparative way. We present this review paper to show that lagomorphs are a strong system in which to study macro- and micro-scale patterns of morphological change within a clade that offers underappreciated levels of diversity. To this end, we offer a summary of the status of relevant aspects of lagomorph biology.
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Racicot RA, Boessenecker RW, Darroch SAF, Geisler JH. Evidence for convergent evolution of ultrasonic hearing in toothed whales (Cetacea: Odontoceti). Biol Lett 2019; 15:20190083. [PMID: 31088283 DOI: 10.1098/rsbl.2019.0083] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Toothed whales (Cetacea: Odontoceti) are the most diverse group of modern cetaceans, originating during the Eocene/Oligocene transition approximately 38 Ma. All extant odontocetes echolocate; a single origin for this behaviour is supported by a unique facial source for ultrasonic vocalizations and a cochlea adapted for hearing the corresponding echoes. The craniofacial and inner ear morphology of Oligocene odontocetes support a rapid (less than 5 Myr) early evolution of echolocation. Although some cranial features in the stem odontocetes Simocetus and Olympicetus suggest an ability to generate ultrasonic sound, until now, the bony labyrinths of taxa of this grade have not been investigated. Here, we use µCT to examine a petrosal of a taxon with clear similarities to Olympicetus avitus. Measurements of the bony labyrinth, when added to an extensive dataset of cetartiodactyls, resulted in this specimen sharing a morphospace with stem whales, suggesting a transitional inner ear. This discovery implies that either the lineage leading to this Olympicetus--like taxon lost the ability to hear ultrasonic sound, or adaptations for ultrasonic hearing evolved twice, once in xenorophids and again on the stem of the odontocete crown group. We favour the latter interpretation as it matches a well-documented convergence of craniofacial morphology between xenorophids and extant odontocetes.
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Affiliation(s)
- Rachel A Racicot
- 1 W.M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges , Claremont, CA 91711 , USA.,2 Vertebrate Paleontology Department and The Dinosaur Institute, Natural History Museum of Los Angeles County , Los Angeles, CA 90007 , USA.,3 Department of Earth and Environmental Sciences, Vanderbilt University , Nashville, TN 37340 , USA
| | - Robert W Boessenecker
- 4 Department of Geology and Environmental Geosciences, College of Charleston , Charleston, SC 29414 , USA
| | - Simon A F Darroch
- 3 Department of Earth and Environmental Sciences, Vanderbilt University , Nashville, TN 37340 , USA
| | - Jonathan H Geisler
- 5 Department of Anatomy, New York Institute of Technology, College of Osteopathic Medicine , Old Westbury, NY 11568 , USA
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Cribb AT, Kenchington CG, Koester B, Gibson BM, Boag TH, Racicot RA, Mocke H, Laflamme M, Darroch SAF. Increase in metazoan ecosystem engineering prior to the Ediacaran-Cambrian boundary in the Nama Group, Namibia. R Soc Open Sci 2019; 6:190548. [PMID: 31598294 PMCID: PMC6774933 DOI: 10.1098/rsos.190548] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 08/23/2019] [Indexed: 05/20/2023]
Abstract
The disappearance of the soft-bodied Ediacara biota at the Ediacaran-Cambrian boundary potentially represents the earliest mass extinction of complex life, although the precise driver(s) of this extinction remain unresolved. The 'biotic replacement' model proposes that an evolutionary radiation of metazoan ecosystem engineers in the latest Ediacaran profoundly altered marine palaeoenvironments, resulting in the extinction of Ediacara biota and setting the stage for the subsequent Cambrian Explosion. However, metazoan ecosystem engineering across the Ediacaran-Cambrian transition has yet to be quantified. Here, we test this key tenet of the biotic replacement model by characterizing the intensity of metazoan bioturbation and ecosystem engineering in trace fossil assemblages throughout the latest Ediacaran Nama Group in southern Namibia. The results illustrate a dramatic increase in both bioturbation and ecosystem engineering intensity in the latest Ediacaran, prior to the Cambrian boundary. Moreover, our analyses demonstrate that the highest-impact ecosystem engineering behaviours were present well before the onset of the Cambrian. These data provide the first support for a fundamental prediction of the biotic replacement model, and evidence for a direct link between the early evolution of ecosystem engineering and the extinction of the Ediacara biota.
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Affiliation(s)
- Alison T. Cribb
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA
| | | | - Bryce Koester
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Department of Biodiversity, Drexel University, Philadelphia, PA, 19104, USA
| | - Brandt M. Gibson
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Thomas H. Boag
- Geological Sciences, Stanford University, Stanford, CA 94304, USA
| | - Rachel A. Racicot
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Helke Mocke
- Geological Survey of Namibia, Ministry of Mines and Energy, Windhoek, Namibia
| | - Marc Laflamme
- Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, CanadaL5L 1C6
| | - Simon A. F. Darroch
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
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Gibson BM, Rahman IA, Maloney KM, Racicot RA, Mocke H, Laflamme M, Darroch SAF. Gregarious suspension feeding in a modular Ediacaran organism. Sci Adv 2019; 5:eaaw0260. [PMID: 31223655 PMCID: PMC6584682 DOI: 10.1126/sciadv.aaw0260] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 05/14/2019] [Indexed: 05/29/2023]
Abstract
Reconstructing Precambrian eukaryotic paleoecology is pivotal to understanding the origins of the modern, animal-dominated biosphere. Here, we combine new fossil data from southern Namibia with computational fluid dynamics (CFD) to test between competing feeding models for the Ediacaran taxon Ernietta. In addition, we perform simulations for multiple individuals, allowing us to analyze hydrodynamics of living communities. We show that Ernietta lived gregariously, forming shallow marine aggregations in the latest Ediacaran, 548 to 541 million years (Ma) ago. We demonstrate enhanced vertical mixing of the water column above aggregations and preferential redirection of current into body cavities of downstream individuals. These results support the reconstruction of Ernietta as a macroscopic suspension feeder and also provide a convincing paleoecological advantage to feeding in aggregations analogous to those recognized in many extant marine metazoans. These results provide some of the oldest evidence of commensal facilitation by macroscopic eukaryotes yet recognized in the fossil record.
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Affiliation(s)
| | - Imran A. Rahman
- Oxford University Museum of Natural History, Oxford OX1 3PW, UK
| | - Katie M. Maloney
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Rachel A. Racicot
- Vanderbilt University, Nashville, TN 37235-1805, USA
- WM Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, 925 N Mills Ave., Claremont, CA 91711, USA
| | - Helke Mocke
- Geological Survey of Namibia, National Earth Science Museum, Windhoek, Namibia
| | - Marc Laflamme
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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Galatius A, Olsen MT, Steeman ME, Racicot RA, Bradshaw CD, Kyhn LA, Miller LA. Raising your voice: evolution of narrow-band high-frequency signals in toothed whales (Odontoceti). Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly194] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Anders Galatius
- Department of Bioscience, Aarhus University, Roskilde, Denmark
| | - Morten Tange Olsen
- Evolutionary Genomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen O, Denmark
| | | | - Rachel A Racicot
- W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA, USA
- The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN, USA
| | - Catherine D Bradshaw
- School of Geographical Sciences, University of Bristol, Bristol, UK
- Met Office Hadley Centre, Exeter, UK
| | - Line A Kyhn
- Department of Bioscience, Aarhus University, Roskilde, Denmark
| | - Lee A Miller
- Department of Biology, University of Southern Denmark, Odense, Denmark
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7
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Racicot RA, Darroch SAF, Kohno N. Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae). J Anat 2018; 233:421-439. [PMID: 30033539 PMCID: PMC6131972 DOI: 10.1111/joa.12862] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2018] [Indexed: 10/28/2022] Open
Abstract
Narwhals (Monodon monoceros) and belugas (Delphinapterus leucas) are the only extant members of the Monodontidae, and are charismatic Arctic-endemic cetaceans that are at risk from global change. Investigating the anatomy and sensory apparatuses of these animals is essential to understanding their ecology and evolution, and informs efforts for their conservation. Here, we use X-ray CT scans to compare aspects of the endocranial and inner ear labyrinth anatomy of extant monodontids and use the overall morphology to draw larger inferences about the relationship between morphology and ecology. We show that differences in the shape of the brain, vasculature, and neural canals of both species may relate to differences in diving and other behaviors. The cochleae are similar in morphology in the two species, signifying similar hearing ranges and a close evolutionary relationship. Lastly, we compare two different methods for calculating 90var - a calculation independent of body size that is increasingly being used as a proxy for habitat preference. We show that a 'direct' angular measurement method shows significant differences between Arctic and other habitat preferences, but angle measurements based on planes through the semicircular canals do not, emphasizing the need for more detailed study and standardization of this measurement. This work represents the first comparative internal anatomical study of the endocranium and inner ear labyrinths of this small clade of toothed whales.
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Affiliation(s)
- Rachel A. Racicot
- Department of Earth and Environmental SciencesVanderbilt UniversityNashvilleTNUSA
- The Dinosaur InstituteNatural History Museum of Los Angeles CountyLos AngelesCAUSA
| | - Simon A. F. Darroch
- Department of Earth and Environmental SciencesVanderbilt UniversityNashvilleTNUSA
| | - Naoki Kohno
- Department of Geology and PaleontologyNational Museum of Nature and ScienceTokyoJapan
- Graduate School of Life and Environmental SciencesUniversity of TsukubaTsukubaJapan
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Darroch SAF, Rahman IA, Gibson B, Racicot RA, Laflamme M. Inference of facultative mobility in the enigmatic Ediacaran organism Parvancorina. Biol Lett 2017; 13:rsbl.2017.0033. [PMID: 28515329 DOI: 10.1098/rsbl.2017.0033] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 04/21/2017] [Indexed: 11/12/2022] Open
Abstract
Establishing how Ediacaran organisms moved and fed is critical to deciphering their ecological and evolutionary significance, but has long been confounded by their non-analogue body plans. Here, we use computational fluid dynamics to quantitatively analyse water flow around the Ediacaran taxon Parvancorina, thereby testing between competing models for feeding mode and mobility. The results show that flow was not distributed evenly across the organism, but was directed towards localized areas; this allows us to reject osmotrophy, and instead supports either suspension feeding or detritivory. Moreover, the patterns of recirculating flow differ substantially with orientation to the current, suggesting that if Parvancorina was a suspension feeder, it would have been most efficient if it was able to re-orient itself with respect to current direction, and thus ensure flow was directed towards feeding structures. Our simulations also demonstrate that the amount of drag varied with orientation, indicating that Parvancorina would have greatly benefited from adjusting its position to minimize drag. Inference of facultative mobility in Parvancorina suggests that Ediacaran benthic ecosystems might have possessed a higher proportion of mobile taxa than currently appreciated from trace fossil studies. Furthermore, this inference of movement suggests the presence of musculature or appendages that are not preserved in fossils, but which would noneltheless support a bilaterian affinity for Parvancorina.
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Affiliation(s)
| | - Imran A Rahman
- Oxford University Museum of Natural History, Oxford OX1 3PW, UK
| | - Brandt Gibson
- Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Rachel A Racicot
- Natural History Museum of Los Angeles County, Los Angeles, CA 90007, USA
| | - Marc Laflamme
- University of Toronto Mississauga, Mississauga, Ontario L5 L 1C6, Canada
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Darroch SAF, Sperling EA, Boag TH, Racicot RA, Mason SJ, Morgan AS, Tweedt S, Myrow P, Johnston DT, Erwin DH, Laflamme M. Biotic replacement and mass extinction of the Ediacara biota. Proc Biol Sci 2016; 282:rspb.2015.1003. [PMID: 26336166 DOI: 10.1098/rspb.2015.1003] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The latest Neoproterozoic extinction of the Ediacara biota has been variously attributed to catastrophic removal by perturbations to global geochemical cycles, 'biotic replacement' by Cambrian-type ecosystem engineers, and a taphonomic artefact. We perform the first critical test of the 'biotic replacement' hypothesis using combined palaeoecological and geochemical data collected from the youngest Ediacaran strata in southern Namibia. We find that, even after accounting for a variety of potential sampling and taphonomic biases, the Ediacaran assemblage preserved at Farm Swartpunt has significantly lower genus richness than older assemblages. Geochemical and sedimentological analyses confirm an oxygenated and non-restricted palaeoenvironment for fossil-bearing sediments, thus suggesting that oxygen stress and/or hypersalinity are unlikely to be responsible for the low diversity of communities preserved at Swartpunt. These combined analyses suggest depauperate communities characterized the latest Ediacaran and provide the first quantitative support for the biotic replacement model for the end of the Ediacara biota. Although more sites (especially those recording different palaeoenvironments) are undoubtedly needed, this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life.
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Affiliation(s)
- Simon A F Darroch
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1805, USA
| | - Erik A Sperling
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA Department of Geological Sciences, Stanford University, 450 Serra Mall Bldg. 320, Stanford, CA 94305, USA
| | - Thomas H Boag
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
| | - Rachel A Racicot
- Department of Biology, Howard University, 415 College Street NW, Washington, DC 20059, USA
| | - Sara J Mason
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
| | - Alex S Morgan
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
| | - Sarah Tweedt
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Behavior, Ecology, Evolution & Systematics, University of Maryland, College Park, MD 20742, USA
| | - Paul Myrow
- Geology Department, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO 80903, USA
| | - David T Johnston
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
| | - Douglas H Erwin
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
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Racicot RA, Gearty W, Kohno N, Flynn JJ. Comparative anatomy of the bony labyrinth of extant and extinct porpoises (Cetacea: Phocoenidae). Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12857] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Rachel A. Racicot
- The Dinosaur Institute; Natural History Museum of Los Angeles County; Los Angeles CA USA
- Smithsonian Institution; P. O. Box 37012 MRC 121 Washington DC 20013-7012 USA
| | - William Gearty
- Department of Geological Sciences; Stanford University; Stanford CA USA
| | - Naoki Kohno
- Department of Geology and Paleontology; Division of Biotic Evolution; National Museum of Nature and Science; Tokyo Japan
- Graduate School of Life and Environmental Sciences; University of Tsukuba; Japan
| | - John J. Flynn
- Department of Vertebrate Paleontology; Division of Paleontology; American Museum of Natural History; New York NY USA
- Richard Gilder Graduate School; American Museum of Natural History; New York NY USA
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Rahman IA, Darroch SAF, Racicot RA, Laflamme M. Suspension feeding in the enigmatic Ediacaran organism Tribrachidium demonstrates complexity of Neoproterozoic ecosystems. Sci Adv 2015; 1:e1500800. [PMID: 26702439 PMCID: PMC4681345 DOI: 10.1126/sciadv.1500800] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 10/05/2015] [Indexed: 05/15/2023]
Abstract
The first diverse and morphologically complex macroscopic communities appear in the late Ediacaran period, 575 to 541 million years ago (Ma). The enigmatic organisms that make up these communities are thought to have formed simple ecosystems characterized by a narrow range of feeding modes, with most restricted to the passive absorption of organic particles (osmotrophy). We test between competing feeding models for the iconic Ediacaran organism Tribrachidium heraldicum using computational fluid dynamics. We show that the external morphology of Tribrachidium passively directs water flow toward the apex of the organism and generates low-velocity eddies above apical "pits." These patterns of fluid flow are inconsistent with osmotrophy and instead support the interpretation of Tribrachidium as a passive suspension feeder. This finding provides the oldest empirical evidence for suspension feeding at 555 to 550 Ma, ~10 million years before the Cambrian explosion, and demonstrates that Ediacaran organisms formed more complex ecosystems in the latest Precambrian, involving a larger number of ecological guilds, than currently appreciated.
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Affiliation(s)
- Imran A. Rahman
- School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Simon A. F. Darroch
- Smithsonian Institution, P. O. Box 37012, MRC 121, Washington, DC 20013–7012, USA
- Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235–1805, USA
- Corresponding author. E-mail:
| | - Rachel A. Racicot
- Smithsonian Institution, P. O. Box 37012, MRC 121, Washington, DC 20013–7012, USA
- The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA 90007, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario L5L 1C6, Canada
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12
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Hsiang AY, Field DJ, Webster TH, Behlke ADB, Davis MB, Racicot RA, Gauthier JA. The origin of snakes: revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record. BMC Evol Biol 2015; 15:87. [PMID: 25989795 PMCID: PMC4438441 DOI: 10.1186/s12862-015-0358-5] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/22/2015] [Indexed: 11/17/2022] Open
Abstract
Background The highly derived morphology and astounding diversity of snakes has long inspired debate regarding the ecological and evolutionary origin of both the snake total-group (Pan-Serpentes) and crown snakes (Serpentes). Although speculation abounds on the ecology, behavior, and provenance of the earliest snakes, a rigorous, clade-wide analysis of snake origins has yet to be attempted, in part due to a dearth of adequate paleontological data on early stem snakes. Here, we present the first comprehensive analytical reconstruction of the ancestor of crown snakes and the ancestor of the snake total-group, as inferred using multiple methods of ancestral state reconstruction. We use a combined-data approach that includes new information from the fossil record on extinct crown snakes, new data on the anatomy of the stem snakes Najash rionegrina, Dinilysia patagonica, and Coniophis precedens, and a deeper understanding of the distribution of phenotypic apomorphies among the major clades of fossil and Recent snakes. Additionally, we infer time-calibrated phylogenies using both new ‘tip-dating’ and traditional node-based approaches, providing new insights on temporal patterns in the early evolutionary history of snakes. Results Comprehensive ancestral state reconstructions reveal that both the ancestor of crown snakes and the ancestor of total-group snakes were nocturnal, widely foraging, non-constricting stealth hunters. They likely consumed soft-bodied vertebrate and invertebrate prey that was subequal to head size, and occupied terrestrial settings in warm, well-watered, and well-vegetated environments. The snake total-group – approximated by the Coniophis node – is inferred to have originated on land during the middle Early Cretaceous (~128.5 Ma), with the crown-group following about 20 million years later, during the Albian stage. Our inferred divergence dates provide strong evidence for a major radiation of henophidian snake diversity in the wake of the Cretaceous-Paleogene (K-Pg) mass extinction, clarifying the pattern and timing of the extant snake radiation. Although the snake crown-group most likely arose on the supercontinent of Gondwana, our results suggest the possibility that the snake total-group originated on Laurasia. Conclusions Our study provides new insights into when, where, and how snakes originated, and presents the most complete picture of the early evolution of snakes to date. More broadly, we demonstrate the striking influence of including fossils and phenotypic data in combined analyses aimed at both phylogenetic topology inference and ancestral state reconstruction. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0358-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Allison Y Hsiang
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA.
| | - Daniel J Field
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA. .,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20560, USA.
| | - Timothy H Webster
- Department of Anthropology, Yale University, New Haven, Connecticut, 06520, USA.
| | - Adam D B Behlke
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA.
| | - Matthew B Davis
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA.
| | - Rachel A Racicot
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA.
| | - Jacques A Gauthier
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA. .,Yale Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06520, USA.
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Ekdale EG, Racicot RA. Anatomical evidence for low frequency sensitivity in an archaeocete whale: comparison of the inner ear of Zygorhiza kochii with that of crown Mysticeti. J Anat 2014; 226:22-39. [PMID: 25400023 DOI: 10.1111/joa.12253] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2014] [Indexed: 11/28/2022] Open
Abstract
The evolution of hearing in cetaceans is a matter of current interest given that odontocetes (toothed whales) are sensitive to high frequency sounds and mysticetes (baleen whales) are sensitive to low and potentially infrasonic noises. Earlier diverging stem cetaceans (archaeocetes) were hypothesized to have had either low or high frequency sensitivity. Through CT scanning, the morphology of the bony labyrinth of the basilosaurid archaeocete Zygorhiza kochii is described and compared to novel information from the inner ears of mysticetes, which are less known than the inner ears of odontocetes. Further comparisons are made with published information for other cetaceans. The anatomy of the cochlea of Zygorhiza is in line with mysticetes and supports the hypothesis that Zygorhiza was sensitive to low frequency noises. Morphological features that support the low frequency hypothesis and are shared by Zygorhiza and mysticetes include a long cochlear canal with a high number of turns, steeply graded curvature of the cochlear spiral in which the apical turn is coiled tighter than the basal turn, thin walls separating successive turns that overlap in vestibular view, and reduction of the secondary bony lamina. Additional morphology of the vestibular system indicates that Zygorhiza was more sensitive to head rotations than extant mysticetes are, which likely indicates higher agility in the ancestral taxon.
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Affiliation(s)
- Eric G Ekdale
- Department of Biology, San Diego State University, San Diego, CA, USA; Department of Paleontology, San Diego Natural History Museum, San Diego, CA, USA
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Racicot RA, Colbert MW. Morphology and Variation in Porpoise (Cetacea: Phocoenidae) Cranial Endocasts. Anat Rec (Hoboken) 2013; 296:979-92. [DOI: 10.1002/ar.22704] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 03/20/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Rachel A. Racicot
- Department of Geology and Geophysics; Yale University; New Haven Connecticut
| | - Matthew W. Colbert
- Jackson School of Geosciences; The University of Texas at Austin; Austin Texas
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Racicot RA, Berta A. Comparative morphology of porpoise (cetacea: Phocoenidae) pterygoid sinuses: Phylogenetic and functional implications. J Morphol 2012. [DOI: 10.1002/jmor.20116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Racicot RA, Berta A. Comparative morphology of porpoise (Cetacea: Phocoenidae) pterygoid sinuses: phylogenetic and functional implications. J Morphol 2012; 274:49-62. [PMID: 22965565 DOI: 10.1002/jmor.20075] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 07/30/2012] [Accepted: 08/07/2012] [Indexed: 11/11/2022]
Abstract
High-resolution X-ray computed tomographic scans were used to examine pterygoid sinus morphology within extant porpoise species and one delphinid (Tursiops truncatus), in order to consider: 1) intraspecific and interspecific variation among the studied species; 2) the most parsimonious sequence of character acquisition; and 3) the potential functional roles of the preorbital lobes of the sinuses in sound reflection. Scans revealed that the pterygoid/palatine regions are mediolaterally broader in the earliest diverging phocoenid (Neophocaena phocaenoides) and Tursiops truncatus than the dorsoventrally elongated sinuses observed in other species. Rostrocaudal lengths of the sphenoidal regions of the sinuses in all individuals studied are proportionally similar, indicating conservatism in this region across species. The neonate Phocoena phocoena has shorter preorbital lobes than adults, but they are still proportionally longer than Neophocaena phocaenoides and Phocoena spinipinnis. The preorbital lobes broaden mediolaterally to varying degrees across species; in particular, Phocoenoides dalli has the largest dorsal and lateral expansion of this region. Assuming the highest pulse frequency produced by porpoises is 150 kHz, all regions of the preorbital lobes are thick enough to reflect the wavelengths produced. In addition, the neonate preorbital lobes are not as elongated as they are in adults, and the dorsal third of this region may not reflect sound to the same extent. This study reinforces the importance of using nondestructive methods to quantify variation in endocranial anatomy and the value of CT data for recovering phylogenetically useful information, as well as functional roles sinuses play in concert with the soft tissue head anatomy for biosonar.
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Affiliation(s)
- Rachel A Racicot
- Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA.
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