Researchers discovered a new mammaliform genus, Megacauda sungei, which represents a semi-aquatic forebear of living mammals and was the first known animal capable of suckling. The fossil evidence for Megacauda sungei dates back to a period between 163 million and 168 million years ago.
The team was able to reconstruct the entire throat anatomy of the creature, and its pelvis and hyoids are preserved in three dimensions. Estimates suggest that Megacauda sungei weighed approximately one kilogram.
Tiny limb fragments, resembling bones from salamanders, were found within the fossil's stomach area. Oliver Griffith of Macquarie University in Sydney stated that the evidence indicates that traits like sucking, necessary for drinking milk from mothers, existed before the origin of modern mammals.
Furthermore, Luo noted that the evolutionary origins of the pharyngeal and hyoid structures were known to predate the rise of modern mammals, as the researchers previously understood very little about this pattern. Griffith added that it is interesting to observe this sister lineage to today's mammals developing an aquatic way of life, a pattern seen repeatedly across the mammalian family tree, including in the platypus.
