First authorship determined by coin toss!

This week's Science features the most complete and robust mammalian phylogeny to date, in the snappily titled: "Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification" by Jan Janečka et al.*

Apart from the beautiful figures (see the main phylogeny below), the thing that really caught my eye was the unusual superscripting of "First/Last authorship determined by coin toss." Never seen that one before! I've been on a couple of joint first author papers before but we've never had to resort to a coin toss to determine the "first first" and "second first" author order. Then again, they've not been Science papers, so I guess the stakes weren't so high.

*The listed first author is actually Robert Meredith but I thought I would play "parallel universe" for poor Jan Janečka, who missed out on the first author coin toss. (The last author coin toss is not so bad as papers do not get abbreviated to the last author in the same way as the first authorship; this paper will always be "Meredith et al.")