A new primitive Neornithischian dinosaur from the Jurassic of Patagonia with gut contents

Abstract

We describe a new species of an ornithischian dinosaur, Isaberrysaura mollensis gen. et sp. nov. The specimen, consisting in an almost complete skull and incomplete postcranium was collected from the marine-deltaic deposits of the Los Molles Formation (Toarcian-Bajocian), being the first reported dinosaur for this unit, one of the oldest from Neuquén Basin, and the first neornithischian dinosaur known from the Jurassic of South America. Despite showing a general stegosaurian appearance, the extensive phylogenetic analysis carried out depicts Isaberrysaura mollensis gen. et sp. nov. as a basal ornithopod, suggesting that both Thyreophora and neornithischians could have achieved significant convergent features. The specimen was preserved articulated and with some of its gut content place in the middle-posterior part of the thoracic cavity. Such stomach content was identified as seeds, most of them belonging to the Cycadales group. This finding reveals a possible and unexpected role of this ornithischian species as seed-dispersal agent.

Allometric scaling of seed retention time in seed dispersers and its application to estimation of seed dispersal potentials of theropod dinosaurs

“…Fruit and seed morphologies adapted for dispersal by vertebrates appeared before the Mesozoic era (Pennsylvanian period); therefore, herbivorous dinosaurs are the primary candidates considered responsible for seed dispersal in the Mesozoic era (Tiffney , Pu et al ). A set of species of Theropoda have distinctive morphologies adapted for herbivory (Zanno and Makovicky , Pu et al ), whereas some of the theropod and ornithischian dinosaurs show direct evidence of fruit or seed consumption (Zhou and Zhang , Salgado et al ). In addition, carnivorous dinosaurs could have dispersed seeds, either by accidental consumption of seeds or via their consumption of herbivorous animals; this has been confirmed in some extant vertebrates (Nogales et al , van Leeuwen et al ).…”

Peer Review #2 of "The systematic position of the enigmatic thyreophoran dinosaur Paranthodon africanus, and the use of basal exemplifiers in phylogenetic analysis (v0.1)"

“…Constraint trees were then written using the 'Force' command in TNT to explore how labile the position of Paranthodon was in each phylogenetic analysis. The significance of the constraint trees was tested using 1000 replications of the Templeton Test (Salgado et al, 2017). Support for groupings was tested using symmetric resampling, which was carried out with a probability of 33% and 1000 replicates on a 'New Technology' search of existing trees.…”

“…The most recent phylogeny of Stegosauria by Raven and Maidment (2017) showed Paranthodon and Tuojiangosaurus to clade together, a result that was found again here in the one most parsimonious tree of length 279.65 (Analysis E1). Isaberrysaura, the Argentinian dinosaur found as a neornithischian by Salgado et al (2017), was then found in a sister-taxon relationship with Gigantspinosaurus (Analysis E2). However, the strict consensus of the four most parsimonious trees of length 285.38 had a lack of resolution at the base of Eurypoda.…”

“…That basal exemplifiers may be inappropriate is further supported by our analyses of the Boyd (2015) dataset. The recently described taxon Isaberrysaura (Salgado et al 2017) was included as an OTU in Analysis D6, as well as Huayangosaurus, Stegosaurus and Paranthodon (Fig. 8).…”

“…This taxon was included here because although it was recovered as a basal neornithischian by Salgado et al (2017), it possesses numerous anatomical features normally associated with thyreophorans, and was found to be a stegosaur in Han et al (2017). Analysis D6 resulted in Isaberrysaura being found as a basal neornithischian, along with Paranthodon and the unambiguous stegosaurs Huayangosaurus and Stegosaurus.…”