A Juvenile Specimen of Sauropodomorpha from the Lower Jurassic of China and a Brief Review of the Lufeng Sauropodomorph Fauna

Abstract

An incomplete dinosaur skeleton, including a partial skull, recently discovered from the Lower Jurassic Lufeng Formation of Yunnan, China, is here reported. Apart from its small size, little anatomical evidence supports, a priori, the non-adult status of this new sauropodomorph specimen but osteohistological analyses suggest that it is a fast-growing juvenile. This specimen represents only the second occurrence of a juvenile non-sauropodan sauropodomorph in the Lufeng Basin. The anatomy of the new specimen does not match that of other Lower Jurassic immature specimens; although cranial material is preserved, it does not display the diagnostic characters of early sauropodomorphs from the same horizon, namely Lufengosaurus, Yizhousaurus and Yunnanosaurus. Our phylogenetic analysis places the new specimen in a position relatively distant from other Chinese sauropodomorphs, and corroborates the anatomical evidence showing it is not referable to any known species already excavated in Yunnan. This result is interpreted with caution considering that ontogeny affects phylogenetic reconstruction. A thorough comparison with adult forms, taking into account ontogenyrelated characters, suggests that this Lufeng juvenile might represent a previously unknown species of early sauropodomorph.

Palaeobiology of the early sauropodomorph Mussaurus patagonicus inferred from its long bone histology

“…2020; Peyre de Fabrègues et al . 2021). Assuming an annual periodicity for CGM formation (Castanet et al .…”

An unusually robust specimen attributed to Buriolestes schultzi (Dinosauria: Sauropodomorpha) from the Late Triassic of southern Brazil

“…Although CAPPA/UFSM 0244 is recovered close to C. novasi in the phylogenetic analysis with the dataset of Langer et al (2022), both are also grouped with the other specimens of B. schultzi . Character states that support the affinities between CAPPA/UFSM 0244 and C. novasi are related to proportions or susceptible to plastic deformation, which are usually affected by sedimentary compression or intraspecific variation (Hone et al, 2016; Müller et al, 2019; Müller, Garcia, et al, 2018; Peyre de Fabrègues et al, 2021). Actually, the holotype and only specimen of C. novasi is heavily deformed (Ezcurra, 2010; Martinez et al, 2013), and these affinities should be carefully considered.…”

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

“…Small, skeletally immature individuals of early sauropodomorphs are relatively rare (Bonaparte & Vince, 1979; Müller et al, 2019; Peyre de Fabrègues et al, 2021). From the Caturrita Formation, the only unambiguous record of a juvenile sauropodomorph is a small tibia (Pretto et al, 2016).…”

“…The discovery of new specimens is important because early dinosaurs and their relatives are known by their high intraspecific variation resulting from ontogenetic development (Griffin & Nesbitt, 2016; Müller et al, 2019; Piechowski et al, 2014). It is crucial to track this variation in order to generate more reliable phylogenetic and taxonomic hypotheses (Otero & Pol, 2022; Peyre de Fabrègues et al, 2021) and, consequently, macroevolutionary scenarios. The anatomy of the new specimen resembles that of the holotype of U. tolentinoi .…”