24 out of the 25 fossils were freshly born hatchlings, however unexpectedly the 25th wasn't a parent, or even an adult, but an teenage sibling of the hatchlings.
A volcanic eruption combined with rains likely caused the babysitter to step up, having dispursed all adults in chaos, the teenage specimen was fully capable of running away to save itself for a little longer, however it chose to stay behind. Leading it's siblings to a safer area to take shelter, Using it's body to block the elements, it was likely that this sibling was engulfed by a landslide while trying to protect it's newborn family.