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Hypselospinus (Iguanodontia) from Early Cretaceous of Britain revised

Ben Creisler

A new online paper:

David B. Norman FLS (2014)
On the history, osteology, and systematic position of the Wealden
(Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia:
Zoological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/zoj.12193

The history of discovery and interpretation of several dinosaurs
collected from quarries near the town of Hastings during the latter
half of the 19th century is more complicated than it should be. Samuel
Husbands Beckles and Charles Dawson collected several large ornithopod
skeletons from this area, but just a few bones from these skeletons
were subsequently described and interpreted (principally) by Richard
Owen and Richard Lydekker. All these specimens merited recognition
because they had the potential to contribute to an on-going debate
about the anatomical structure and relationships of the iconic Wealden
dinosaur Iguanodon. Unfortunately, no detailed description of these
important skeletons was published in later years. Furthermore,
previously known associations of bones and even provenance
information, linked to the specimens that were gradually acquired by
the Natural History Museum, are unclear. Confusion may have arisen
because Richard Lydekker used the private collector Charles Dawson as
a voluntary curatorial assistant. This account documents the past work
on the osteology of material that can be attributed to Hypselospinus
fittoni. Nearly all such material is described here for the first
time, and every effort has been made to re-establish associations
between bones as well as provenance information. A skeletal
reconstruction of Hypselospinus is attempted on the basis of the
hypodigm. Most of the on-going confusion concerning the affinity of
this material with either Hy. fittoni or its sympatric contemporary
Barilium dawsoni has been resolved. Hypselospinus fittoni (Lydekker,
1889) is rediagnosed on the basis of this new and relatively
comprehensive anatomical description, and this animal is compared with
known contemporary and closely related taxa. Some recently published
accounts claiming to be revisions of the taxonomy of Wealden
‘iguanodonts’, including material belonging to the hypodigm of Hy.
fittoni, have failed to adhere to basic taxonomic principles and have
caused more confusion than was strictly necessary. The systematic
position of Hypselospinus is reassessed cladistically. The cladistic
analysis forms the basis for a revised hierarchical classification of
derived ornithopods. The consensus topology generated by the
systematic analysis has been used to explore the phylogenetic history
of these dinosaurs and create an internally consistent classificatory
hierarchy (phylogenetic definitions and Linnaean diagnoses are given
for critical positions in the topology). This analysis suggests that
there is a fundamental split amongst the more derived (clypeodontan)
ornithopod ornithischians into the clades Hypsilophodontia and
Iguanodontia. There is evidence for anatomical parallelism and
convergence (homoplasy) particularly between large-bodied
representatives of both clades. Hypselospinus is one of the earliest
known styracosternan iguanodontians and displays anatomical
characteristics that presage the evolution of the extraordinarily
abundant and diverse hadrosaurs of the latest Cretaceous
(Campanian−Maastrichtian). These observations cast fresh light on the
phylogeny, classification, diversity, and biology of derived
ornithopods. There is little doubt that Hy. fittoni could have been
understood far better more than a century ago. That this statement is
undoubtedly true is reflected in the century of doubt and confusion
that has surrounded this taxon and its original incarnation as
Iguanodon fittoni.