Shape and mechanics in thalattosuchian (Crocodylomorpha) skulls: implications for feeding behaviour and niche partitioning.
Variation in modern crocodilian and extinct thalattosuchian crocodylomorph skull morphology is only weakly correlated with phylogeny, implying that factors other than evolutionary proximity play important roles in determining crocodile skull shape. To further explore factors potentially influencing morphological differentiation within the Thalattosuchia, we examine teleosaurid and metriorhynchid skull shape variation within a mechanical and dietary context using a combination of finite element modelling and multivariate statistics. Patterns of stress distribution through the skull were found to be very similar in teleosaurid and metriorhynchid species, with stress peaking at the posterior constriction of the snout and around the enlarged supratemporal fenestrae. However, the magnitudes of stresses differ, with metriorhynchids having generally stronger skulls. As with modern crocodilians, a strong linear relationship between skull length and skull strength exists, with short-snouted morphotypes experiencing less stress through the skull than long-snouted morphotypes under equivalent loads. Selection on snout shape related to dietary preference was found to work in orthogonal directions in the two families: diet is associated with snout length in teleosaurids and with snout width in metriorhynchids, suggesting that teleosaurid skulls were adapted for speed of attack and metriorhynchid skulls for force production. Evidence also indicates that morphological and functional differentiation of the skull occurred as a result of dietary preference, allowing closely related sympatric species to exploit a limited environment. Comparisons of the mechanical performance of the thalattosuchian skull with extant crocodilians show that teleosaurids and long-snouted metriorhynchids exhibit stress magnitudes similar to or greater than those of long-snouted modern forms, whereas short-snouted metriorhynchids display stress magnitudes converging on those found in short-snouted modern species. As a result, teleosaurids and long-snouted metriorhynchids were probably restricted to lateral attacks of the head and neck, but short-snouted metriorhynchids may have been able to employ the grasp and shake and/or 'death roll' feeding and foraging behaviours.
Pierce
S E
SE
University Museum of Zoology, Department of Zoology, University of Cambridge, Cambridge, UK. sep55@cam.ac.uk
Angielczyk
K D
KD
Rayfield
E J
EJ
D000489:Alligators and Crocodiles / Q000033:anatomy & histology* / Q000502:physiology; D000818:Animals; D005075:Biological Evolution; D001732:Bite Force; D002508:Cephalometry / Q000379:methods; D004032:Diet; D005247:Feeding Behavior / Q000502:physiology*; D020342:Finite Element Analysis; D005580:Fossils; D008953:Models, Anatomic; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology* / Q000502:physiology; D013045:Species Specificity; D013314:Stress, Mechanical
J Biomech. 1987;20(11-12):1035-44
3429455
J Bone Joint Surg Am. 1974 Jul;56(5):1001-22
4603167
Naturwissenschaften. 2008 Jan;95(1):79-84
17712540
Bioinformatics. 2008 Jan 1;24(1):129-31
18006550
Anat Rec A Discov Mol Cell Evol Biol. 2006 Aug;288(8):827-49
16835925
Evolution. 2006 Apr;60(4):824-41
16739463
Proc Biol Sci. 2002 Feb 7;269(1488):317-26
11839201
Sci Am. 1976 Apr;234(4):114-9, 122-4
1257732
Anat Rec A Discov Mol Cell Evol Biol. 2005 Apr;283(2):331-48
15747347
J Morphol. 2008 Jul;269(7):840-64
18496856
Science. 2006 Jan 6;311(5757):70-3
16282526
Evolution. 1998 Oct;52(5):1247-1262
28565378
Proc Biol Sci. 2004 Jul 22;271(1547):1451-9
15306316
Anat Rec. 1999 Apr 1;254(4):496-507
10203257
Syst Biol. 1998 Dec;47(4):654-72
12066309
Anat Anz. 1964 Oct 13;115:256-80
14327484
Syst Biol. 2004 Dec;53(6):933-48
15764561
Syst Biol. 1999 Sep;48(3):547-58
12066293
Proc Natl Acad Sci U S A. 2000 Apr 11;97(8):4106-11
10760280
Anat Histol Embryol. 2002 Aug;31(4):206-13
12196262
J Morphol. 1999 Sep;241(3):251-63
10461135
Evolution. 1991 Aug;45(5):1065-1080
28564168
J Exp Zool. 2001 Jul 1;290(2):101-7
11471139
Anat Rec A Discov Mol Cell Evol Biol. 2005 Apr;283(2):319-30
15747350
Ann Anat. 2004 Dec;186(5-6):387-96
15646269