Abstract
The sauropod dinosaur “Pelorosaurus” becklesii was named in 1852 on the basis of an associated left humerus, ulna, radius and skin impression from the Early Cretaceous (Berriasian-Valanginian) Hastings Beds Group, near Hastings, East Sussex, southeast England, United Kingdom. The taxonomy and nomenclature of this specimen have a complex history, but most recent workers have agreed that “P.” becklesii represents a distinct somphospondylan (or at least a titanosauriform) and is potentially the earliest titanosaur body fossil from Europe or even globally. The Hastings specimen is distinct from the approximately contemporaneous Pelorosaurus conybeari from Tilgate Forest, West Sussex. “P.” becklesii can be diagnosed on the basis of five autapomorphies, such as: a prominent anteriorly directed process projecting from the anteromedial corner of the distal humerus; the proximal end of the radius is widest anteroposteriorly along its lateral margin; and the unique combination of a robust ulna and slender radius. The new generic name Haestasaurus is therefore erected for “P.” becklesii. Three revised and six new fore limb characters (e.g. the presence/absence of condyle-like projections on the posterodistal margin of the radius) are discussed and added to three cladistic data sets for Sauropoda. Phylogenetic analysis confirms that Haestasaurus becklesii is a macronarian, but different data sets place this species either as a non-titanosauriform macronarian, or within a derived clade of titanosaurs that includes Malawisaurus and Saltasauridae. This uncertainty is probably caused by several factors, including the incompleteness of the Haestasaurus holotype and rampant homoplasy in fore limb characters. Haestasaurus most probably represents a basal macronarian that independently acquired the robust ulna, enlarged olecranon, and other states that have previously been regarded as synapomorphies of clades within Titanosauria. There is growing evidence that basal macronarian taxa survived into the Early Cretaceous of Europe and North America.
Highlights
Sauropod dinosaurs were globally distributed mega-herbivores that dominated many Mesozoic terrestrial ecosystems [1,2,3]
The current study represents one such reappraisal, focussed on the Early Cretaceous taxon “Pelorosaurus” becklesii Mantell 1852 [22]. This taxon is significant regionally and globally for several reasons: it potentially represents the earliest known European titanosaur [6,18]; it provides a glimpse of sauropod evolution during the otherwise poorly represented Berriasian-Valanginian, a period that documents the initial recovery of sauropods from a significant extinction event around the Jurassic-Cretaceous boundary [2,23,24,25]; and it includes the first dinosaurian skin impression recognised by science [26]
The English sauropod “Pelorosaurus” becklesii is based on fore limb elements and a skin impression
Summary
Sauropod dinosaurs were globally distributed mega-herbivores that dominated many Mesozoic terrestrial ecosystems [1,2,3]. In recent years, significant progress in our understanding of sauropod evolution has been driven by several factors, including an influx of information on new taxa (e.g., see [4]: fig 4), phylogenetic analysis [1,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19], and new technology such as CT-scanning and Finite Element Analysis (e.g., [20,21]) These advances provide fresh opportunities to revisit material that was first discovered in the 19th or early 20th centuries, in order to address previously intractable taxonomic, phylogenetic or other problems. We consider the new information on “P.” becklesii in the wider context of sauropod evolutionary history
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