High browsing skeletal adaptations in Spinophorosaurus reveal an evolutionary innovation in sauropod dinosaurs

Abstract: Sauropods were among the most diverse lineages of dinosaurs, with an ample geographic distribution throughout the Mesozoic. This evolutionary success is largely attributed to neck elongation and its impact on feeding efficiency. However, how neck elongation influenced exactly on feeding strategies is subject of debate. The process of mounting a nearly complete virtual skeleton of Spinophorosaurus nigerensis, from the Middle (?) Jurassic of Niger, has revealed several previously unknown osteological adaptations in this taxon. Wedged sacral and posterior dorsal vertebrae cause the presacral column to deflect antero-dorsally. This, together with elongated scapulae and humeri make the anterior region of the skeleton vertically lengthened…

…This implied a functional constraint for sauropod species which evolved lower browsing feeding strategies: the antero-dorsal sloping caused by the sacrum had to be counteracted with further skeletal modifications, e.g. a ventrally curved mid to anterior presacral spine to hinder the dorsal slope of the whole presacral series caused by the wedged sacrum. This suggests that at least the last common ancestor of Eusauropoda developed high browsing capabilities, partially due to the modified wedged sacrum, likely a potential synapomorphy of the clade and key in the evolutionary history of the group.

41598_2020_63439_Fig4_HTML

Skeletal reconstructions of Spinophorosaurus nigerensis.

(A) Original skeletal reconstruction of Spinophorosaurus first published in 2009, modified from the original publication

(B) Virtual skeletal reconstruction of Spinophorosaurus.

Vital et al. (2020)

Additional Resources on Sauropod Neck Posture:

Blog review of the scientific article: What can sauropod sacra tell us about neck posture?

Journal Article: Head and neck posture in sauropod dinosaurs inferred from extant animals

Journal Article: The Effect of Intervertebral Cartilage on Neutral Posture and Range of Motion in the Necks of Sauropod Dinosaurs

Journal Article: Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs

 

 

Leave a Reply