In 2001, the giant titanosaurian sauropod dinosaur
Paralititan stromeri was described from the midCretaceous (Cenomanian) Bahariya Formation of
Egypt. Despite the incompleteness of the holotype
(Egyptian Geological Museum [CGM] 81119), the
1.69 m humerus of Paralititan indicated the presence
of an extraordinarily large-bodied titanosaurian on
the African continent, rivaling in size those known
from the Americas at the time (e.g., Argentinosaurus,
Alamosaurus). Since then, several enormous new
titanosaurians have been described from the mid–
Late Cretaceous of South America (e.g.,
Dreadnoughtus, Futalognkosaurus, Notocolossus,
Patagotitan), as have several other African Late
Cretaceous titanosaurs (e.g., Mansourasaurus,
Rukwatitan). Following from these discoveries,
recent analyses have proposed the existence of
certain clades of often gigantic titanosaurians (e.g.,
Colossosauria, Lognkosauria). Paralititan, however,
has been omitted from these analyses, most likely due
to its fragmentary nature and the brevity of its
published description.
Here we provide an updated assessment of the
evolutionary relationships of Paralititan to test
whether this taxon belongs to one of the
aforementioned clades of exceptionally large
titanosaurs. We re-evaluated and updated the scorings
of Paralititan in our working phylogenetic dataset and conducted both parsimony and tip-dating
Bayesian phylogenetic analyses (57 taxa scored for
285 variable and 302 autapomorphic characters). Our
parsimony results postulate Paralititan as the sister
taxon of Rukwatitan, with this African clade being
the outgroup to a clade of generally large titanosaurs
that consist mainly of forms widely regarded as
lognkosaurians plus a clade of taxa with a biconvex
first caudal vertebra (e.g., Alamosaurus,
Dreadnoughtus). The tip-dating Bayesian analysis
produced similar results, except that Rukwatitan was
recovered within Lognkosauria, with Patagotitan and
Paralititan being successive outgroups to this clade.
Furthermore, the Late Cretaceous ingroup clade to
the exclusion of Paralititan consists of the smallbodied Saltasauridae and several small–mediumsized titanosaurians from Afro-Eurasia (e.g.,
Mansourasaurus) amongst Colossosauria and the
‘biconvex first caudal clade.’ The latter results
support the notion that, on continental Africa,
multiple titanosaurian lineages underwent trends
toward either larger or smaller body sizes, paralleling
a pattern seen in the Late Cretaceous of South
America. |
