Are you from the 1830s? https://books.google.com/ngrams/graph?content=platypi%2C+platypuses&year_start=1800&year_end=2019&corpus=26&smoothing=3&direct_url=t1%3B

Are you from the 1830s? https://books.google.com/ngrams/graph?content=platypi%2C+platypuses&year_start=1800&year_end=2019&corpus=26&smoothing=3&direct_url=t1%3B%2Cplatypi%3B%2Cc0%3B.t1%3B%2Cplatypuses%3B%2Cc0 https://books.google.com/ngrams/graph?content=platypi%2C+pla... Platypuses don’t live in North America. Most of the older sources that Google n-gram is pulling from for the above chart are British or Australian. A substantial proportion of the recent uses of platypi are grammar guides telling people that it should always be spelled platypuses.