A new long-spined dinosaur from Patagonia sheds light on sauropod defense system

Pablo A Gallina,Alejandro Haluza,Sebastián Apesteguía,Juan I Canale

doi:10.1038/s41598-018-37943-3

Pablo A Gallina, Alejandro Haluza + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-37943-3

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Abstract

Dicraeosaurids are a group of sauropod dinosaurs characterized by a distinctive vertebral column with paired, long, neural spines, present in an extreme fashion in the South American form Amargasaurus cazaui. This distinctive morphology has been interpreted as a support structure for a thermoregulatory sail, a padded crest for display, a dorsal hump acting as fat reservoir, and even as inner cores for dorsal horns. Other inferred functions (if any) of this structure were related to sexual display and/or defense strategies. Here we describe a new dicraeosaurid sauropod, Bajadasaurus pronuspinax gen. et sp. nov., from Patagonia which preserves the most complete skull of the group and has extremely elongate bifid cervical neural spines that point permanently forward, irrespective of the neck position. Although much shorter versions of this neural spine configuration were already recorded for other dicraeosaurid taxa, the long, anteriorly bent spines of this new dinosaur support the hypothesis that these elongate spines of dicraeosaurid sauropods served as passive defense structures.

Highlights

Since the finding of the nearly complete skeletons of Dicraeosaurus in the expeditions to the upper Jurassic “Saurian beds” of Tendaguru, Tanzania, led by Werner Janensch from the Geological-Paleontological Institute and Museum of the University of Berlin in the early 20th century (1909–1912), the presence of elongate bifid neural spines in the axial skeleton of this taxon was always a distinctive and iconic feature[1,2]
The skull was recovered in articulation with the anterior region of the neck and another cervical vertebra with exceptional development of anteriorly bent, bifid cervical neural spines, which informs hypotheses of defense behavior in sauropod dinosaurs
The temporal difference between Bajadasaurus and Amargasaurus, a 15 My younger spiny sauropod from the Neuquén basin, supports that the development of a fence of spines was likely adaptive over a long time period

Summary

Introduction

More than eighty years later, the discovery of a new, rather complete, dicraeosaurid skeleton from the Early Cretaceous of South America, Amargasaurus cazaui[3], renewed discussions on the peculiar vertebral anatomy of these sauropod dinosaurs including interpretations as a support structure for a thermoregulatory sail, a padded crest as a display and/ or clattering structure, a dorsal hump, or as internal cores of dorsal horns[4,5,6]. Nov., from the Early Lower Cretaceous Bajada Colorada Formation (Northern Patagonia, Argentina), which includes dermal roof and palatal bones, a braincase, and a nearly complete lower jaw, expands the knowledge on the skull morphology of this group[13]. The skull was recovered in articulation with the anterior region of the neck and another cervical vertebra with exceptional development of anteriorly bent, bifid cervical neural spines, which informs hypotheses of defense behavior in sauropod dinosaurs. The temporal difference between Bajadasaurus and Amargasaurus, a 15 My younger spiny sauropod from the Neuquén basin, supports that the development of a fence of spines was likely adaptive over a long time period

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