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Maledictosuchus, new metriorhynchid crocodylomorph from the Middle Jurassic of Spain



From: Ben Creisler
bcreisler@gmail.com


New in PLoS ONE:

Jara Parrilla-Bel, Mark T. Young, Miguel Moreno-Azanza & José Ignacio
Canudo (2013)
The First Metriorhynchid Crocodylomorph from the Middle Jurassic of
Spain, with Implications for Evolution of the Subclade Rhacheosaurini.
PLoS ONE 8(1): e54275.
doi:10.1371/journal.pone.0054275
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0054275




Background

Marine deposits from the Callovian of Europe have yielded numerous
species of metriorhynchid crocodylomorphs. While common in English and
French Formations, metriorhynchids are poorly known from the Iberian
Peninsula. Twenty years ago an incomplete, but beautifully preserved,
skull was discovered from the Middle Callovian of Spain. It is
currently the oldest and best preserved metriorhynchid specimen from
the Iberian Peninsula. Until now it has never been properly described
and its taxonomic affinities remained obscure.

Methodology/Principal Findings

Here we present a comprehensive description for this specimen and in
doing so we refer it to a new genus and species: Maledictosuchus
riclaensis. This species is diagnosed by numerous autapomorphies,
including: heterodont dentition; tightly interlocking occlusion;
lachrymal anterior process excludes the jugal from the preorbital
fenestra; orbits longer than supratemporal fenestrae; palatine has two
non-midline and one midline anterior processes. Our phylogenetic
analysis finds Maledictosuchus riclaensis to be the basal-most known
member of Rhacheosaurini (the subclade of increasingly mesopelagic
piscivores that includes Cricosaurus and Rhacheosaurus).

Conclusions/Significance

Our description of Maledictosuchus riclaensis shows that the
craniodental morphologies that underpinned the success of
Rhacheosaurini in the Late Jurassic and Early Cretaceous, as a result
of increasing marine specialization to adaptations for feeding on fast
small-bodied prey (i.e. divided and retracted external nares;
reorientation of the lateral processes of the frontal; elongate,
tubular rostrum; procumbent and non-carinated dentition; high overall
tooth count; and dorsolaterally inclined paroccipital processes),
first appeared during the Middle Jurassic. Rhacheosaurins were
curiously rare in the Middle Jurassic, as only one specimen of
Maledictosuchus riclaensis is known (with no representatives
discovered from the well-sampled Oxford Clay Formation of England). As
such, the feeding/marine adaptations of Rhacheosaurini did not confer
an immediate selective advantage upon the group, and it took until the
Late Jurassic for this subclade to dominate in Western Europe.