added links to Heim 2009 data matrix (#84) and McElwain et al. abstract and text (#95)
added links to Heim 2009 data matrix (#84) and McElwain et al. abstract and text (#95)

paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new