A crocodile in Costa Rica has made herself pregnant, the first recorded instance of a "virgin birth" in the reptile species.
The crocodile was kept in captivity in a zoo and had no contact with males - but a fully-formed foetus was discovered inside one of her eggs.
The foetus was 99.9% genetically identical to the mother, confirming it had no father.
Virgin births, or parthenogenesis, have been documented in birds, lizards, snakes and fish, but never before in crocodiles.
The crocodile in question was 18 when she laid a clutch of eggs in 2018.
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Seven of the eggs appeared to be viable and were incubated but when none hatched after three months they were opened. One contained a stillborn crocodile foetus.
Researchers from Virginia Tech who specialise in parthenogenesis analysed the foetus and their findings were published in the Royal Society journal Biology Letters.
They said the discovery suggests virgin births could be happening in crocodiles without anyone realising.
"It is not uncommon for captive reptiles to lay clutches of eggs, given the period of isolation from mates, these would normally be considered non-viable and discarded.
"These findings therefore suggest that eggs should be assessed for potential viability when males are absent.
"Furthermore, given that (virgin births) can occur in the presence of potential mates, instances of this may be missed when reproduction occurs in females co-habited with males."
The scientists said the discovery offers "tantalising insights" into the possible reproductive capabilities of extinct relatives of crocodiles, particularly dinosaurs.