The elongated neck of sauropodomorph dinosaurs evolved gradually

Abstract

Discoveries from South America have increased our knowledge on the early evolutionary history of sauropodomorph dinosaurs. The dietary shift from faunivorous to herbivorous creatures and the increasing body size are both widely documented in the fossil record. Conversely, the initial evolution of the elongated neck is poorly known. It is one of the most diagnostic features of Sauropodomorpha. There is a gap between the record of short‐necked sauropodomorphs from Carnian (±233 Ma) and long‐necked forms from early Norian (±225 Ma). As a consequence, it is unknown if the cervical vertebrae became long gradually or abruptly. In the present study, we present a new specimen excavated from strata that belong to this time interval (±228 Ma). CAPPA/UFSM 0352 comprises a series of five cervical vertebrae unearthed from the Late Triassic of Southern Brazil. The vertebrae are proportionately longer than that of older forms and proportionately shorter than that of younger ones. Therefore, our results demonstrate that the elongation of the neck of sauropodomorphs is an example of gradual evolutionary process. Except by its elongated shape, the general anatomy of the cervical elements resembles that of the earliest forms (i.e., have a conservative anatomy). Combined with previous data, it is possible to conclude that the shape of the skull and teeth, as well as the neck proportions, were the first structures to clearly differ derived sauropodomorphs from early diverging forms. Finally, some of the recovered phylogenetic scenarios favor the origins of the elongated neck in the clade Bagualosauria.

The dawn of an Era: New contributions on comparative and functional anatomy of Triassic tetrapods

“…The authors demonstrate, from this specimen, that the early sauropodomorphs could attain considerable sizes within the spectrum of early dinosaur evolution. A pivotal study conducted by Damke et al (2024, this issue) describes Brazilian Carnian dinosaur fossils, shedding light on the gradual evolution of the distinctively elongated neck, a hallmark feature of sauropodomorphs and sauropods. As we delve into the Norian stage, we witness the transformation of sauropodomorphs into large‐bodied, herbivorous creatures, potentially exhibiting gregarious behavior.…”

On a skeletally immature individual of Unaysaurus tolentinoi (Dinosauria: Sauropodomorpha) from the upper Triassic of southern Brazil

“…The origin and early radiation of sauropodomorph dinosaurs have been exhaustively investigated during the last decade (Langer et al, 2022; Novas et al, 2021; Otero & Peyre de Fabrègues, 2022; Pol et al, 2021). The evolution of the body plan during the Triassic Period has received great attention (Ballell, Rayfield, & Benton, 2022; Bronzati et al, 2019; Cabreira et al, 2016; Damke et al, 2024; McPhee et al, 2018; Müller et al, 2018), especially regarding the acquisition of typical traits related to gigantism (Apaldetti et al, 2018; Lefebvre et al, 2022; Peyre de Fabrègues & Allain, 2020). Some studies examined biogeographical patterns (Griffin et al, 2021; Dunne et al, 2023), whereas others investigated the biology and ecology of the group (Aureliano et al, 2022; Ballell, Benton, & Rayfield, 2022; Bronzati et al, 2017; Cerda et al, 2022; Müller, 2022; Otero et al, 2019; Pol et al, 2021).…”