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, 2 (4), 611-4

Prey Choice and Cannibalistic Behaviour in the Theropod Coelophysis

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Prey Choice and Cannibalistic Behaviour in the Theropod Coelophysis

Sterling J Nesbitt et al. Biol Lett.

Abstract

Direct evidence of prey choice in carnivorous dinosaurs is rare in the fossil record. The most celebrated example pertains to purported stomach contents in the carnivorous dinosaur Coelophysis bauri, which besides revealing prey choice, also points to cannibalistic behaviour as being commonplace (Colbert 1989, 1995). Here, we test this hypothesis by conducting the first comprehensive anatomical and histological examination of the famed Coelophysis 'cannibals'. The results unequivocally show that the gut contents derive from early crocodylomorphs rather than juveniles of Coelophysis. These findings suggest that this taxon is not cannibalistic and bring into question the commonality of this behaviour among non-avian dinosaurs.

Figures

Figure 1
Figure 1
Abdominal region of Coelophysis bauri neotype (AMNH FR 7224). (a) Detail of abdominal cavity of AMNH FR 7224 showing posterodorsally intact stomach (dotted line) with preserved contents (AMNH FR 30616) highlighted in yellow. Right femur and left ilium, left femur (fe) and sacral vertebra (sv) of stomach content material. Intact gastralia in green, right dorsal ribs in blue and left dorsal ribs in red. Note that both left and right ribs lie above purported stomach remains in anteroventral portion of abdomen, thereby rejecting that material as preserved stomach content. (b) Detail of ingested right femur and left ilium in lower left. (c) The two purported cannibalistic C. bauri specimens prior to exhibition in 1950s. Neotype of C. bauri: (b) AMNH FR 7224 and (c) AMNH FR 7223. Abbreviations: ac, acetabulum; fe, femur; ip, ischial peduncle of ilium; pu, pubis; sc, scapula; sv, sacral vertebra.
Figure 2
Figure 2
Comparative morphological and histological evidence illustrating Crocodylomorpha affinities of the Coelophysis bauri stomach contents. (ad) Hesperosuchus agilis (AMNH FR 6758), right proximal femur in (a) lateral, (b) medial and (c) dorsal views, and (d) histological section from the medial metaphysis of cf. Hesperosuchus (GR 215; see electronic supplementary material). (eh) Right proximal femur of stomach contents (AMNH FR 30616) in (e) lateral, (f) medial and (g) dorsal views, and (h) histological section from the medial metaphysis. (il) Coelophysis bauri (AMNH FR 30618), right proximal femur in (i) lateral, (j) medial and (k) dorsal views, and (l) histological section from the medial metaphysis from a juvenile Coelophysis (AMNH FR 30617). All histological specimens show compacted cancellous bone, indicative of incorporation of what was formerly the ends of the bones into the dense bone shafts later in development. Each was capped by a layer of primary fibrolamellar bone along a mediolateral front, attesting to the deposition of new bone atop of the former metaphyses. The presence of a concave, indistinct transition to the initially avascular primary bone and subsequent primary bone showing longitudinal or locally semi-radiating vascularization patterns indicates that the (h) stomach content specimen and (d) cf. Hesperosuchus possess nearly identical developmental histories. In contrast, (l) the transition zone in Coelophysis lacks an avascular zone, and is very thin and distinctive, indicating a complete cessation of bone deposition prior to the capping with primary periosteal bone. The transition zone is straight, unlike the concave pattern seen in cf. Hesperosuchus and the stomach content. Finally, the vascular canals in Coelophysis are relatively long and show pronounced, inclined radiating patterns. The histological patterning and developmental histories are consistent with the stomach contents' referral to Crocodylomorpha from the independent morphological character evidence. Institutional abbreviation: GR, Ruth Hall Museum of Paleontology at Ghost Ranch Conference Centre, Ghost Ranch, New Mexico. Femoral scale bars, 5 mm. Histology scale bars, 1 mm. Asterisk indicates site of histology sample. Abbreviations: at, anterior trochanter; faa, facies articularis antitrochanterica; pcf, proximal condylar fold; ofh, offset femoral head.

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