A 500-year-old prayer book owned by a nun is being heralded as evidence that the Dutch were not the first Europeans to arrive in Australia.

The Dutch have historically been credited with landing the first European ship on Australian shores in 1606 but the Portuguese prayer book is dated between 1580 and 1620 and has a kangaroo-like creature sketched into it pages as well as an image of a bare-chested man with leaves in his hair which could possibly be an Indigenous Australian.

A New York gallery, Les Enluminures, has acquired the book, which is believed to have been owned by a nun from western Portugal named Caterina de Carvalho – the name inscribed in the manuscript – and has been valued at about US$15,000.

Laura Light, a researcher for Les Enluminures, said speculation about whether the manuscript “proved” if it was the Dutch or Portuguese who were the first Europeans to arrive on Australia’s shores was “a little too narrow”.

“Surely the fact that this drawing is found in such an unlikely context – a prayer book owned by a Portuguese nun at the end of the sixteenth or early seventeenth centuries – tells us something of interest about the level of contact between these two cultures,” she said in an email.

The Portuguese were notoriously secretive about which routes they had sailed so it has been difficult to ascertain when they first came to Australia, but there has been speculation for years that they beat the Dutch to it.

Some of the main pieces of “evidence” used are maps dating back to the 1540s which were presented to King Henry VIII of England and show a huge land mass beneath Indonesia and Papua New Guinea.

The National Library of Australia’s curator of maps, Martin Woods, said he doubted the sketch was of a kangaroo and it could possibly be a possum or even a deer, which sometimes eat on their hind legs.

“There’s no tail showing which would be the, excuse the language, the major telltale,” he said.

“If you were drawing a kangaroo the first thing you would draw is the tail. It’s drawn inside a D so the tail could be obscured but you could make it wrap around the letter.”

Woods also said the front legs and the hind legs looked the same size and it should be noted the document was essentially an illustration, not part of a map or official record.

“I think it’s very exciting for people who already believe the Portuguese were the first to reach Australia but for people who do not believe it, the manuscript is not that exciting,” he said.