The early evolution of titanosauriform sauropod dinosaurs

Abstract

Titanosauriformes was a globally distributed, long‐lived clade of dinosaurs that contains both the largest and smallest known sauropods. These common and diverse megaherbivores evolved a suite of cranial and locomotory specializations perhaps related to their near‐ubiquity in Mesozoic ecosystems. In an effort to understand the phylogenetic relationships of their early (Late Jurassic–Early Cretaceous) members, this paper presents a lower‐level cladistic analysis of basal titanosauriforms in which 25 ingroup and three outgroup taxa were scored for 119 characters. Analysis of these characters resulted in the recovery of three main clades: Brachiosauridae, a cosmopolitan mix of Late Jurassic and Early Cretaceous sauropods, Euhelopodidae, a clade of mid‐Cretaceous East Asian sauropods, and Titanosauria, a large Cretaceous clade made up of mostly Gondwanan genera. Several putative brachiosaurids were instead found to represent non‐titanosauriforms or more derived taxa, and no support for a Laurasia‐wide clade of titanosauriforms was found. This analysis establishes robust synapomorphies for many titanosauriform subclades. A re‐evaluation of the phylogenetic affinities of fragmentary taxa based on these synapomorphies found no body fossil evidence for titanosaurs before the middle Cretaceous (Aptian), in contrast to previous reports of Middle and Late Jurassic forms. Purported titanosaur track‐ways from the Middle Jurassic either indicate a substantial ghost lineage for the group or – more likely – represent non‐titanosaurs. Titanosauriform palaeobiogeographical history is the result of several factors including differential extinction and dispersal. This study provides a foundation for future study of basal titanosauriform phylogeny and the origins of Titanosauria. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166, 624–671.

An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America's last giant sauropod

“…Originally established with a node-based definition (D Andesaurus delgadoi C Titanosauridae and all descendants of their most recent common ancestor; Salgado et al 1997), some subsequent works adopted a stem-based definition for the name and anchored the definition on other, more specific taxa (D all titanosauriforms more closely related to Saltasaurus loricatus than to Euhelopus zdanskyi; Sereno 1998; Wilson & Sereno 1998); then it was used again as a node-based name (D Andesaurus delgadoi C Saltasaurus loricatus and all descendants of their most recent common ancestor, Wilson & Upchurch 2003). The discovery of new titanosauriform taxa in recent years has also produced new hypotheses of titanosauriform phylogeny (Curry Rogers 2005;Calvo et al 2007a,b;Gonz alez Riga et al 2009;D'Emic 2012;Mannion et al 2013;Carballido & Sander 2014), which have sometimes resulted in taxonomic redundancy stemming from the shuffling of taxa used to anchor taxonomic definitions. For the purpose of this paper, we will follow the principle of priority whenever possible, adopting the first definition of a clade or lineage with an ancestry-based stem or node definition.…”

Upper Jurassic sauropod record in the Lusitanian Basin (Portugal): Geographical and lithostratigraphical distribution

“…Several compressed cone-chisel teeth were found in the Upper Jurassic sedimentary sequence of the Lusitanian Basin (Alcobaça, Praia da AmoreiraPorto Novo, Sobral, Freixial, and Bombarral Formations). This tooth morphology was traditionally considered as synapomorphic of Titanosauriformes (e.g., Upchurch et al, 2004;D'Emic, 2012), but this morphology was also found in the possible basal macronarian Europasaurus (Carballido and Sander, 2014), which was also considered to be a member of Titanosauriformes by D'Emic (2012) and Mannion et al (2013). If we accept the phylogenetic position proposed for Europasaurus by Carballido and Sander (2014), this tooth morphology should be present in a more inclusive group than Titanosauriformes.…”

Appendicular osteology ofDreadnoughtus schrani, a giant titanosaurian (Sauropoda, Titanosauria) from the Upper Cretaceous of Patagonia, Argentina

“…All this previous work and the detailed description of the material (Sanz et al, 1999;Company et al, 2009;Company, 2011;Díez Díaz et al, 2011, 2012, 2013, as well as its inclusion in numerous phylogenetic analyses, have made Lirainosaurus astibiae one of the world's best-known titanosaurian species, and a main reference for the study of the sauropod faunas of the Late Cretaceous of Europe.…”