Discovery of facultative parthenogenesis in a New World crocodile

Over the past two decades, there has been an astounding growth in the
documentation of vertebrate facultative parthenogenesis (FP). This unusual
reproductive mode has been documented in birds, non-avian
reptiles—specifically lizards and snakes—, and elasmobranch fishes. Part
of this growth among vertebrate taxa is attributable to awareness of the
phenomenon itself and advances in molecular genetics/genomics and
bioinformatics, and as such our understanding has developed considerably.
Nonetheless, questions remain as to its occurrence outside of these
vertebrate lineages, most notably in Chelonia (turtles) and Crocodylia
(crocodiles, alligators, and gharials). The latter group is particularly
interesting because unlike all previously documented cases of FP in
vertebrates, crocodilians lack sex chromosomes and sex determination is
controlled by temperature. Here, using whole-genome sequencing data, we
provide the first evidence of FP in a crocodilian, the American Crocodile,
Crocodylus acutus. The data support terminal fusion automixis as the
reproductive mechanism; a finding which suggests a common evolutionary
origin of FP across reptiles, crocodilians, and birds. With FP now
documented in the two main branches of extant archosaurs, this discovery
offers tantalizing insights into the possible reproductive capabilities of
the extinct archosaurian relatives of crocodilians and birds, notably
members of Pterosauria and Dinosauria.