Metriorhynchid Crocodylomorph from the Middle Jurassic of Spain in PLoS ONE

["Ing. Yasmani Ceballos Izquierdo" <yceballos@uci.cu>]

Another paper in PLoS ONE that may be of interest:
Parrilla-Bel J, Young MT, Moreno-Azanza M, Canudo JI (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


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.


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