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| Tenontosaurus tilletti (Ostrom, 1970) in Nudds, Lomax & Tennant, 2022. Artwork by James McKay |
Abstract
Tenontosaurus tilletti was an abundant ornithischian dinosaur from the Lower Cretaceous of North America, commonly regarded as a ‘basal’ iguanodontian. Here, we describe a remarkably well-preserved specimen, comprising a near-complete skeleton and skull, from the Cloverly Formation, Montana, USA, currently housed at the University of Manchester Museum, UK. Found alongside the specimen were alleged gastroliths, cycad seeds, and teeth of the contemporaneous dromaeosaur Deinonychus antirrhopus, all of which were buried in an alleged ash. We assess the credibility of these claims, using X-ray CT scanning and X-ray fluorescence (XRF) respectively, and show that the ‘seeds’ are non-organic mineral concretions, and that the ‘ash’ is actually a lime mud with a silica content of approximately 7%. We confirm the identification of the Deinonychus teeth and the gastroliths, providing further evidence to support the long-standing assertion, originally made by John Ostrom in 1970, that Tenontosaurus was a common food item for Deinonychus.
Keywords: Tenontosaurus, Cloverly Formation, Lower Cretaceous, Montanatrophic interaction, gastroliths, iguanodont
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| Tenontosaurus tilletti skeleton (MANCH LL.12275) fully articulated and mounted in bipedal stance for 1999 Lottery-funded gallery display at Manchester University Museum. |
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| Spherical structures (MANCH LL. 12279a, b) found associated with MANCH LL.12275, previously identified as cycad seeds, but which we here reinterpret as mineral concretions of goethite/limonite. Scale bar = 3 cm. |
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| Gastroliths (MANCH LL. 12278a-l) found in the gastric region of MANCH LL.12275. Scale bar = 3 cm. |
Systematic Palaeontology
Ornithischia (Seeley, 1887)
Neornithischia (Sereno, 1999)
Ornithopoda (Marsh, 1881)
Tenontosaurus tilletti (Ostrom, 1970)
Holotype: AMNH 3040, partial skeleton lacking skull and forelimbs.
Paratypes: YPM-PU 16338, a partial skeleton, and YPM 3456, a well-preserved skull and partial skeleton.
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Conclusions:
One of the challenges that palaeontologists are faced with is interpreting the behaviours of organisms preserved only in the fossil record. Studies often rely upon functional morphology to infer behaviour, especially through comparison with modern analogues. However, in rare occurrences, with some examples being more common than others, specimens are sometimes found with direct evidence of interactions, referred to as ‘frozen behaviour’ (Boucot 1990; Boucot and Poinar 2010; Radwanski and Radwanska 2009; Lomax 2021).
MANCH LL.12275 represents one of the most complete and well-preserved specimens of Tenontosaurus tilletti currently known. The original documentation indicated that the specimen was found preserved in ash and with associated cycad seeds. Based on our analyses, we cannot confirm the preservation within a distinct ash layer (although there might have been a minor ash component), while the alleged plant seeds are herein identified as non-organic mineral concretions. The association of teeth of Deinonychus antirrhopus with the skeleton reinforces evidence for one of the most well-documented trophic relationships in the dinosaur fossil record. The gastroliths within the stomach cavity of the specimen also provides further evidence for the feeding habits of Tenontosaurus and is the first case of the use of gastroliths in a more derived ornithopod; it is also one of the geologically oldest examples of gastroliths found within an ornithopod.
John R. Nudds, Dean R. Lomax and Jonathan P. Tennant. 2022. Gastroliths and Deinonychus Teeth associated with A Skeleton of Tenontosaurus from the Cloverly Formation (Lower Cretaceous), Montana, USA. Cretaceous Research. In Press, 105327. DOI: 10.1016/j.cretres.2022.105327
