Data from: Redescription and phylogenetic affinities of the caimanine Eocaiman cavernensis (Crocodylia, Alligatoroidea) from the Eocene of Argentina

Caimaninae is one of the few crocodylian lineages that still has living
representatives. Today, most of its six extant species are restricted to
South and Central America. However, recent discoveries revealed a more
complex evolutionary history, with a fossil record richer than previously
thought and a possible North American origin. Among the oldest caimanines
is Eocaiman cavernensis, from the Eocene of Patagonia, Argentina. It was
described by George G. Simpson in the 1930s, representing the first
caimanine reported for the Paleogene. E. cavernensis has then been
ubiquitous in phylogenetic studies on the group, but a more detailed
morphological description and revision of the taxon was lacking. Here, we
present a reassessment of E. cavernensis, based on first-hand examination
and micro-computed tomography of the holotype, and reinterpret different
aspects of its morphology. We explore the phylogenetic affinities of E.
cavernensis and other caimanines using parsimony and Bayesian inference
approaches. Our results provide evidence for a monophyletic Eocaiman genus
within Caimaninae, even though some highly incomplete taxa (including the
congeneric Eocaiman itaboraiensis) represent significant sources of
phylogenetic instability. We also found Culebrasuchus mesoamericanus as
sister to all other caimanines and the North American globidontans (i.e.
Brachychampsa and closer relatives) outside Caimaninae. A time-calibrated
tree, obtained using a fossilised birth-death model, shows a possible
Campanian origin for the group (76.97±6.7 Ma), which is older than the age
estimated by studies using molecular data, and suggests that the earliest
cladogenetic events of caimanines took place rapidly and across the K-Pg
boundary.