Ever number theory paper I have ever read has listed the authors in alphabetical order, with one exception:
http://www.math.sjsu.edu/~goldston/article03.PDF
D. R. Heath-Brown, D. A. GoldstonHeath-Brown, D. R.; Goldston, D. A., "A note on the difference between consecutive primesA note on the differences between consecutive primes," Math. Annalen 266Ann. 266, 317–320 (1984), 317-320. ZBL0514.10031. PDF (Wayback Machine)
I guess this was due to an editorial error. Dan Goldston once jokingly told me (paraphrase):
"The rules of mathematics do not apply to Heath-Brown."