title: Morphological and biomechanical disparity of crocodile-line archosaurs following the end-Triassic extinction.
abstract: Mesozoic crurotarsans exhibited diverse morphologies and feeding modes, representing considerable ecological diversity, yet macroevolutionary patterns remain unexplored. Here, we use a unique combination of morphological and biomechanical disparity metrics to quantify the ecological diversity and trophic radiations of Mesozoic crurotarsans, using the mandible as a morpho-functional proxy. We recover three major trends. First, the diverse assemblage of Late Triassic crurotarsans was morphologically and biomechanically disparate, implying high levels of ecological variation; but, following the end-Triassic extinction, disparity declined. Second, the Jurassic radiation of marine thalattosuchians resulted in very low morphological disparity but moderate variation in jaw biomechanics, highlighting a hydrodynamic constraint on mandibular form. Third, during the Cretaceous terrestrial radiations of neosuchians and notosuchians, mandibular morphological variation increased considerably. By the Late Cretaceous, crocodylomorphs evolved a range of morphologies equalling Late Triassic crurotarsans. By contrast, biomechanical disparity in the Cretaceous did not increase, essentially decoupling from morphology. This enigmatic result could be attributed to biomechanical evolution in other anatomical regions (e.g. cranium, dentition or postcranium), possibly releasing the mandible from selective pressures. Overall, our analyses reveal a complex relationship between morphological and biomechanical disparity in Mesozoic crurotarsans that culminated in specialized feeding ecologies and associated lifestyles.
authors.affiliation: School of Earth Sciences, University of Bristol, , Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK, Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, The Royal Veterinary College, , Hawkshead Lane, Hatfield AL9 7TA, UK, Department of Biology, Duke University, , Box 90338, Durham, NC 27708, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Stubbs
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Pierce
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Rayfield
authors.forename: Philip S L
authors.initials: PS
authors.lastname: Anderson
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology* / Q000502:physiology*; D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D053476:Extinction, Biological; D005247:Feeding Behavior; D005580:Fossils; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology; D010802:Phylogeny
keywords: crurotarsan; disparity; ecological diversity; evolutionary radiation; form and function; mandible
references.citation: J Morphol. 2008 Jul;269(7):840-64
references.pmid: 18496856
references.citation: Science. 2002 May 17;296(5571):1305-7
references.pmid: 12016313
references.citation: Nature. 2011 Jul 06;476(7359):206-9
references.pmid: 21734660
references.citation: Nature. 2007 Dec 13;450(7172):1011-9
references.pmid: 18075580
references.citation: Science. 1989 Jun 2;244(4908):1064-6
references.pmid: 17741044
references.citation: Integr Comp Biol. 2005 Apr;45(2):256-62
references.pmid: 21676769
references.citation: Nature. 2004 Aug 26;430(7003):1021-4
references.pmid: 15329719
references.citation: J Anat. 2009 Nov;215(5):555-76
references.pmid: 19702868
references.citation: J Morphol. 2006 Sep;267(9):1017-31
references.pmid: 15593308
references.citation: Biol Lett. 2013 Mar 27;9(3):20130095
references.pmid: 23536443
references.citation: Proc Natl Acad Sci U S A. 2011 Jan 4;108(1):232-7
references.pmid: 21173263
references.citation: Proc Biol Sci. 2011 Apr 22;278(1709):1165-70
references.pmid: 20880889
references.citation: J Evol Biol. 2012 Feb;25(2):365-77
references.pmid: 22111918
references.citation: Anat Rec A Discov Mol Cell Evol Biol. 2006 Aug;288(8):827-49
references.pmid: 16835925
references.citation: Syst Biol. 2004 Dec;53(6):933-48
references.pmid: 15764561
references.citation: Evolution. 2007 Jul;61(7):1758-72
references.pmid: 17598754
references.citation: Biol Lett. 2008 Dec 23;4(6):733-6
references.pmid: 18812311
references.citation: Evolution. 2010 Mar 1;64(3):724-44
references.pmid: 19804403
references.citation: Science. 2008 Sep 12;321(5895):1485-8
references.pmid: 18787166
references.citation: J Evol Biol. 2012 May;25(5):904-15
references.pmid: 22356676
references.citation: Proc Biol Sci. 2002 Feb 7;269(1488):317-26
references.pmid: 11839201
references.citation: Evolution. 2004 Mar;58(3):495-503
references.pmid: 15119434
references.citation: Nature. 2010 Aug 5;466(7307):748-51
references.pmid: 20686573