A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus

Abstract

Gong and colleagues recently described unusual traits in the dromaeosaurid Sinornithosaurus that were interpreted as the first evidence of a venomous dinosaur. This interpretation was based on extremely elongated maxillary teeth, morphologically similar to those present in poisonous snakes; labial grooves on maxillary and dentary tooth crowns; and an additional ornamented depression in the lateral surface of the maxillary bone (subfenestral fossa). A reappraisal of each of these morphological traits is provided here in light of comparisons with other theropod dinosaurs and previous discussions for inferring poisonous capabilities in fossil taxa. We fail to recognize unambiguous evidence supporting the presence of a venom delivery system in Sinornithosaurus. For example, the extremely elongated teeth seem to be a taphonomic artifact due to the displacement of teeth outside the alveoli; the labial grooves are present in a wide variety of theropods; and no strong evidence for the lodging of a venomous gland is recognized. In contrast, the cranial and dental anatomy of Sinornithosaurus is congruent with that of other dromaeosaurids. The weak support for a venomous Sinornithosaurus renders unlikely the ecological model proposed by Gong and colleagues for this predatory dinosaur.

Kurzfassung

Gong und Kollegen haben kürzlich Strukturen des dromaeosauriden Sinornithosaurus beschrieben, die sie als ersten Hinweis für einen Dinosaurier mit giftigem Biss deuteten. Ihre Interpretation beruhte auf den stark verlängerten Oberkieferzähnen, die denen giftiger Schlangen ähneln; labialen Einkerbungen auf den Zahnkronen von Ober- und Unterkieferzähnen und einer zusätzlichen ornamentierten Depression in der seitlichen Oberfläche des Maxillare (subfenestrale Grube). Eine Neubewertung dieser morphologischen Merkmale wird hier im Vergleich mit anderen theropoden Dinosauriern und vorangehenden Diskussionen bezüglich der Feststellung von Giftigkeiten bei fossilen Taxa vorgenommen. Wir konnten keine eindeutige Evidenz finden, die das Vorhandensein eines Giftapparates bei Sinornithosaurus belegt. Zum Beispiel scheinen die langen Oberkieferzähne ein taphonomisches Artefakt bedingt durch die Dislozierung der Zähne aus ihren Alveolen zu sein und die labialen Einkerbungen auf den Zähnen sind bei Theropoden weit verbreitet. Zusätzlich konnte keine eindeutige Evidenz für die Existenz einer Giftdrüse gefunden werden. Die kraniale und dentale Anatomie von Sinornithosaurus ist kongruent mit der bei anderen Theropoden. Die unbegründete Interpretation macht das ökologische Model, das Gong und Kollegen für diesen räuberischen Dinosaurier entwarfen unwahrscheinlich.

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Abbreviations

MB:

Museum für Naturkunde der Humboldt Universität, Berlin, Germany

MPCA:

Museo Carlos Ameghino, Cipolletti, Río Negro, Argentina

MPM-Pv:

Museo Padre Molina Paleontología de Vertebrados, Río Gallegos, Santa Cruz, Argentina

UCMP:

University of California Museum of Paleontology, Berkeley, CA, USA

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Acknowledgments

Several people allowed the study of specimens under their care: K. Padian, P. Holroyd, and R. Irmis (UCMP), D. Schwarz-Wings (MB), and C. Muñoz (MPCA). This research was partially funded by the Samuel Welles Fund Grant of the UCMP, the Jurassic Foundation, and the Jackson School Travel Grant of the Society of Vertebrate Paleontology (to M. Ezcurra). We thank the reviews conducted by X. Xu, P. J. Makovicky, and S. L. Brusatte, which helped to improve the quality of the manuscript.

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Correspondence to Federico A. Gianechini.

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Gianechini, F.A., Agnolín, F.L. & Ezcurra, M.D. A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus . Paläontol Z 85, 103–107 (2011). https://doi.org/10.1007/s12542-010-0074-9

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Keywords

  • Sinornithosaurus
  • Dinosauria
  • Dromaeosauridae
  • Venomous system

Schlüsselwörter

  • Sinornithosaurus
  • Dinosauria
  • Dromaeosauridae
  • Giftapparat