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, 8 (5), e65295

Feeding Mechanics in Spinosaurid Theropods and Extant Crocodilians

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Feeding Mechanics in Spinosaurid Theropods and Extant Crocodilians

Andrew R Cuff et al. PLoS One.

Abstract

A number of extant and extinct archosaurs evolved an elongate, narrow rostrum. This longirostrine condition has been associated with a diet comprising a higher proportion of fish and smaller prey items compared to taxa with broader, more robust snouts. The evolution of longirostrine morphology and a bulbous anterior rosette of premaxillary teeth also occurs in the spinosaurid theropod dinosaurs, leading to suggestions that at least some members of this clade also had a diet comprising a notable proportion of fish or other small vertebrates. Here we compare the rostral biomechanics of the spinosaurs Baryonyx walkeri and Spinosaurus c.f. S. aegyptiacus to three extant crocodilians: two longistrine taxa, the African slender-snouted crocodile Mecistops cataphractus and the Indian gharial Gavialis gangeticus; and the American alligator Alligator mississippiensis. Using computed tomography (CT) data, the second moments of area and moments of inertia at successive transverse slices along the rostrum were calculated for each of the species. Size-independent results tested the biomechanical benefits of material distribution within the rostra. The two spinosaur rostra were both digitally reconstructed from CT data and compared against all three crocodilians. Results show that African slender-snouted crocodile skulls are more resistant to bending than an equivalent sized gharial. The alligator has the highest resistances to bending and torsion of the crocodiles for its size and greater than that of the spinosaurs. The spinosaur rostra possess similar resistance to bending and torsion despite their different morphologies. When size is accounted for, B. walkeri performs mechanically differently from the gharial, contradicting previous studies whereas Spinosaurus does not. Biomechanical data support known feeding ecology for both African slender-snouted crocodile and alligator, and suggest that the spinosaurs were not obligate piscivores with diet being determined by individual animal size.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Species tested for second moments of area and moments of inertia.
(A) G. gangeticus (gharial) – NHMUK 2005.1605 (specimen used here), (B) M. cataphractus – NHMUK 1924.5.10.1 (specimen used here), (C) A. mississippiensis (American alligator) for reference – Chicago Zoological Society 31321. Scale bars  =  5 cm.
Figure 2
Figure 2. Lateral and ventral views of Baryonyx walkeri (NHMUK VP R9951) through the stages of digital preparation.
(A) The original specimen in left lateral view, (B) the original specimen in ventral view, (C) the digitally prepared original in left lateral view, (D) the digitally prepared original in ventral view, (E) final specimen with teeth removed and alveoli levelled, (F) final specimen with teeth removed and alveoli levelled showing cloned right maxilla. See Video S1 and S2 for more detailed visualisations of the preparation and reconstruction. Scale bar  = 5 cm.
Figure 3
Figure 3. The digital preparation of Spinosaurus indet.
(NHMUK 16665) in lateral and ventral views. The original specimen – lateral view (A), and ventral view (B). The digitally prepared specimen with no matrix – lateral view (C), and ventral view (D). The rostral reconstruction is based on other specimens of Spinosaurus (e.g. [28]) and the B. walkeri rostra - lateral view (E) and ventral view (F). Video S3 and S4 for more detailed visualisations of preparation and reconstruction. Scale bar  = 5 cm.
Figure 4
Figure 4. Simple illustrations of beam theory
. (A) When a load is applied to a beam with one fixed end (a cantilever beam), the effect of the beam is a deflection in the direction of the force. This results in the most extreme tension on one side of the beam, and the most extreme tension on the opposite side. In the middle, there is a point where there is no tension or compression, called the neutral axis. B) Two circular cross sections of equal cortical area (black). Beam theory states the solid tube (hollow circle) will have higher resistance to bending and torsion than the solid circle due to the material being distributed further from any neutral axis.
Figure 5
Figure 5. Dorsal and lateral views of skulls/reconstructed rostra of the species tested showing slice locations.
(A) A. mississippiensis, (B) G. gangeticus, (C) M. cataphractus, (D) Spinosaurus indet. and (E) B. walkeri. All skulls have had their teeth removed and alveoli leveled. Blue lines indicate first (1) and last (25) slices of the crocodilian study, red lines mark on the spinosaurs (or equivalent for the crocodilians): 1st slice located at the rostral tip; 8th slice located at 18.5% of total rostral length.
Figure 6
Figure 6. Log of absolute and size-corrected second moments of area and moments of inertia for crocodilians.
(A) log absolute Ix , (B) log size-corrected Ix (C) log absolute Iy , (D) log size-corrected Iy, (E) log absolute J , (F) log size-corrected J. Blue  =  alligator, red  =  gharial, black  =  M. cataphractus. Squares  =  upper jaw.
Figure 7
Figure 7. Log of absolute and log of size-corrected second moments of area and moments of inertia for crocodilians and spinosaurid rostra.
(A) log absolute Ix , (B) log size-corrected Ix (C) log absolute Iy , (D) log size-corrected Iy, (E) log absolute J , (F) log size-corrected J. Blue  =  alligator, red  =  gharial, black  =  M. cataphractus, green  =  Spinosaurus, orange  =  B. walkeri.

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References

    1. Busbey AB (1989) Form and function of the feeding apparatus of Alligator mississippiensis . Journal of Morphology 202: 99–127. - PubMed
    1. Cleuren J, Aerts P, De Vree F (1995) Bite force analysis in Caiman crocodilus . Belgian Journal of Zoology 125: 79–94.
    1. Daniel WJT, McHenry CR (2001) Bite force to skull stress correlation: modelling the skull of Alligator mississippiensis. In: Grigg GC, Seebacher F, Franklin CE, editors. Crocodilian biology and evolution. Chipping Norton: Surrey Beatty pp. 135–143.
    1. Langston W Jr (1973) The crocodilian skull in historical perspective. In: Gans C, editor. The biology of the reptilia, pt. 4D. New York: Academic Press. p 263–289.
    1. McHenry CR, Clausen PD, Daniel WJT, Meers MB, Pendharkar A (2006) Biomechanics of the rostrum of crocodilians: a comparative analysis using finite-element modeling. The Anatomical Record 288: 827–849. - PubMed

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