The osteology of Pulanesaura eocollum: implications for the inclusivity of Sauropoda (Dinosauria)

Abstract

We present the complete osteology of the putative basal sauropod Pulanesaura eocollum. Current phylogenetic hypotheses suggest that Pulanesaura is the sister taxon of Vulcanodon + other sauropods, a position supported primarily by derived features of its axial skeleton and forelimb. A question of nontrivial importance is therefore the relative position of Pulanesaura with respect to current higher taxonomic groupings within Sauropodomorpha. The most recently proposed cladistic definition of Sauropoda (the most inclusive clade not including Melanorosaurus) places Pulanesaura as an unambiguous sauropod, whereas another commonly cited definition (the least inclusive clade containing Vulcanodon and Saltasaurus) suggests it is the most proximate sauropod outgroup. In addition to the issues pertaining to the validity of Melanorosaurus, we highlight a suite of features that can be shown to unambiguously and exclusively co-occur at the base of Sauropoda sensu the latter definition, arguing in favour of its continued use. As a corollary to this interpretation, we suggest that, instead of being simple diagnostic artefacts, (complex) apomorphies remain valid signifiers of notable phylogenetic loci whose contribution to our current classificatory schemes remains underexploited.

Anatomy and systematics of the sauropodomorph Sarahsaurus aurifontanalis from the Early Jurassic Kayenta Formation

“…The matrices were constructed in Mesquite [ 65 ] and the phylogenetic analyses were conducted in TNT [ 66 , 67 ]. We also scored the holotype specimen of Sarahsaurus aurifontanalis in a more recent phylogenetic matrix constructed by McPhee et al [ 37 ] and modified by McPhee and Choiniere [ 38 ]; the same character was added to this matrix as the other matrices described above. That matrix contains 61 taxa and 365 characters.…”

A Giant Dinosaur from the Earliest Jurassic of South Africa and the Transition to Quadrupedality in Early Sauropodomorphs

“…Together with the South American taxon Lessemsaurus (known from very large, but most likely skeletally immature, material [11]), these three genera form a monophyletic Lessemsauridae (a fourth member, Ingentia, was too recently described [15] to be included in our analysis). Lessemsauridae is within a pectinate grade of non-sauropodan sauropodiforms sensu [8], basal to Leonerasaurus, Gongxianosaurus, Pulanesaura, and the columnar-limbed quadrupeds known as Sauropoda sensu [16] (Figures 2 and S4).…”

“…This is indicated by a set of derived morphological features of sauropod forelimbs, including reduction of the deltopectoral crest; straightening of the humeral and femoral shafts; lengthening of the antebrachium and modification of the proximal ulna to a triradiate shape; modification of the metacarpus into a U-shaped support structure; loss of the lesser trochanter, migration of the fourth trochanter distally and medially, increase in fibular robustness; and many others [16,18]. These features evolved, at least in incipient forms, by the middle of the Early Jurassic and are exemplified by the early sauropod Vulcanodon [19,21] (see also Pulanesaura [16]).…”

“…To assess the relationships of the holotype of Ledumahadi, we scored it using the phylogenetic dataset of [16], which is based on the original dataset of [9]. We added the following two characters:…”

Cranium and Vertebral Column of Xingxiulong chengi (Dinosauria: Sauropodomorpha) from the Early Jurassic of China

“…The end‐Triassic extinction, although removing many previously dominant groups, gave rise to the true age of dinosaurs with a great radiation of sauropodomorphs (Padian, ; McPhee et al, ). However, the relationships among Early Jurassic sauropodomorphs are highly debated, and this has direct bearing on the origin of Sauropoda, the clade which includes the largest land animals to ever walk the Earth (McPhee and Choiniere, ; Chapelle and Choiniere, ; Regalado Fernandez et al, ; Zhang et al, ).…”