Birastrops, also spelled Birostrop, (PROSE: Scratchman [+]Tom Baker and James Goss, adapted from Doctor Who Meets Scratchman, BBC Books novelisations (BBC Books, 2019).) were a race of short insectoid beings. They had six spindly arms and a chitinous carapace which they could shed at will. Birastrop morality allowed killing for medical research. (PROSE: Where the Heart Is [+]Andy Lane, Decalog 2: Lost Property (Virgin Decalogs, 1995).)
Birastrop lungs were capable of safely breathing in cyanide. Dr Mehendri Solon obtained Birastrop lungs and put them in Morbius's new body, (TV: The Brain of Morbius [+]Robin Bland, Doctor Who season 13 (BBC1, 1976).) along with a Birastrop posterior. (PROSE: Mehendri Solon [+]Error: Code 2 - no data stored in variables, cache or SMW.)
When Scratchman summoned an army of creatures from the Fourth Doctor's memories, the scarecrow replica of the Third Doctor recognised a Birostrop among them, believing they had gone extinct. (PROSE: Scratchman [+]Tom Baker and James Goss, adapted from Doctor Who Meets Scratchman, BBC Books novelisations (BBC Books, 2019).)