The earliest known titanosauriform sauropod dinosaur and the evolution of Brachiosauridae

Abstract

Brachiosauridae is a clade of titanosauriform sauropod dinosaurs that includes the well-known Late Jurassic taxa Brachiosaurus and Giraffatitan. However, there is disagreement over the brachiosaurid affinities of most other taxa, and little consensus regarding the clade’s composition or inter-relationships. An unnamed partial sauropod skeleton was collected from middle–late Oxfordian (early Late Jurassic) deposits in Damparis, in the Jura department of eastern France, in 1934. Since its brief description in 1943, this specimen has been informally known in the literature as the ‘Damparis sauropod’ and ‘French Bothriospondylus’, and has been considered a brachiosaurid by most authors. If correctly identified, this would make the specimen the earliest known titanosauriform. Coupled with its relatively complete nature and the rarity of Oxfordian sauropod remains in general, this is an important specimen for understanding the early evolution of Titanosauriformes. Full preparation and description of this specimen, known from teeth, vertebrae and most of the appendicular skeleton of a single individual, recognises it as a distinct taxon: Vouivria damparisensis gen. et sp. nov. Phylogenetic analysis of a data matrix comprising 77 taxa (including all putative brachiosaurids) scored for 416 characters recovers a fairly well resolved Brachiosauridae. Vouivria is a basal brachiosaurid, confirming its status as the stratigraphically oldest known titanosauriform. Brachiosauridae consists of a paraphyletic array of Late Jurassic forms, with Europasaurus, Vouivria and Brachiosaurus recovered as successively more nested genera that lie outside of a clade comprising (Giraffatitan + Sonorasaurus) + (Lusotitan + (Cedarosaurus + Venenosaurus)). Abydosaurus forms an unresolved polytomy with the latter five taxa. The Early Cretaceous South American sauropod Padillasaurus was previously regarded as a brachiosaurid, but is here placed within Somphospondyli. A recent study contended that a number of characters used in a previous iteration of this data matrix are ‘biologically related’, and thus should be excluded from phylogenetic analysis. We demonstrate that almost all of these characters show variation between taxa, and implementation of sensitivity analyses, in which these characters are excluded, has no effect on tree topology or resolution. We argue that where there is morphological variation, this should be captured, rather than ignored. Unambiguous brachiosaurid remains are known only from the USA, western Europe and Africa, and the clade spanned the Late Jurassic through to the late Albian/early Cenomanian, with the last known occurrences all from the USA. Regardless of whether their absence from the Cretaceous of Europe, as well as other regions entirely, reflects regional extinctions and genuine absences, or sampling artefacts, brachiosaurids appear to have become globally extinct by the earliest Late Cretaceous.

Taxonomic affinities of the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: phylogenetic and biogeographic implications for eusauropod dinosaur evolution

“…2014). A comparable tubercle is also known in the brachiosaurids Giraffatitan and Vouivria (Mannion, Allain & Moine, 2017), but has not been reported in other non-flagellicaudatan sauropod tibiae. As such, it is here regarded as a local autapomorphy of Janenschia.…”

“…In anterior view, the lateral half of the proximal end slopes downwards; thus, the humerus lacks the squared proximolateral corner that characterises somphospondylans , as well as Haestasaurus (Upchurch, Mannion & Taylor, 2015) and Tehuelchesaurus (Carballido et al, 2011). There is expansion along the lateral, as well as medial margins of the proximal end, giving the humerus an hourglass outline in anterior view, rather than the asymmetrical, laterally unexpanded morphology present in most titanosauriforms and several turiasaurs Mannion et al, 2017). The proximal end is anteroposteriorly thickest towards its medial edge, with the humeral head forming a prominent rounded bulge at the proximal tip of the posterior surface.…”

“…1;McIntosh et al, 1996: table 12), Lourinhasaurus (ratio=1.1; Mocho, Royo- Torres & Ortega, 2014) and Vouivria (ratio=1. 1;Mannion et al, 2017).…”

Redescription of Brachiosaurid Sauropod Dinosaur Material From the Upper Jurassic Morrison Formation, Colorado, USA

“…We continue to refer the Cloverly titanosauriform material described by D'Emic and Foreman () to Sauroposeidon proteles (including Paluxysaurus jonesi ; see D'Emic, ), although the dataset of Mannion et al () and other studies using it (e.g., Royo‐Torres et al, ) treat these as three terminal taxa. There are no scoring disagreements between Paluxysaurus and Sauroposeidon or between the “Cloverly titanosauriform” and Sauroposeidon in that data matrix.…”

“…There are no scoring disagreements between Paluxysaurus and Sauroposeidon or between the “Cloverly titanosauriform” and Sauroposeidon in that data matrix. Seven scoring differences are listed between the “Cloverly titanosauriform” and Sauroposeidon in the Mannion et al () matrix (characters 21, 22, 48, 50, 51, 148, and 168); we consider all to be mis‐scored, as briefly outlined below.…”