Seems like there isn’t a strong definition for “megafauna.”
In zoology, megafauna (from Greek μέγας megas "large" and Neo-Latin fauna "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately 45 kilograms (99 lb), with other thresholds as low as 10 kilograms (22 lb) or as high as 1,000 kilograms (2,200 lb).
Not a strong definition but still sufficient to exclude squirrels and even wild pigs are on the very low end.
You raise a good point as I would have expected “mega”fauna to have implied hundreds of kilograms at least. Under 100 and as low as 10 kg seems to take away any true meaning from the label.
