To cite package 'fossil' in publications use:

Vavrek, Matthew J. 2011. fossil: palaeoecological and palaeogeographical analysis tools. Palaeontologia Electronica, 14:1T. http://palaeo-electronica.org/2011_1/238/index.html

Corresponding BibTeX entry:

  @Article{,
    title = {fossil: palaeoecological and palaeogeographical analysis
      tools},
    author = {Matthew J. Vavrek},
    year = {2011},
    journal = {Palaeontologia Electronica},
    volume = {14},
    pages = {1T},
    number = {1},
    note = {R package version 0.4.0},
  }