Historical clue formulations

• Prefix with skeleton — 2026-09-09
• Skeletal prefix — 2024-09-28
• Lead-in to sphere — 2024-06-06
• Prefix with skeleton — 2022-09-27
• Prefix with skeleton — 2022-05-19
• Prefix with skeleton — 2021-02-02
• Prefix with skeleton — 2020-11-11
• Prefix with skeleton — 2019-09-10
• Prefix with planet — 2019-07-07
• Prefix with thermic — 2019-07-06
• Prefix with skeleton — 2017-02-06
• Prefix with planet — 2017-01-31
• Outside: Prefix — 2016-11-20
• Outer opening? — 2015-10-08
• Prefix with skeleton — 2015-07-22
• Prefix with biology — 2015-07-04
• Intro to biology? — 2015-05-10
• Prefix with skeleton — 2015-03-10
• Intro to biology? — 2014-06-20
• Prefix with thermal — 2014-03-30
• Prefix with skeleton — 2013-09-22
• Prefix with biology — 2013-04-25
• Prefix with thermal — 2013-02-14
• Prefix with skeleton — 2012-06-13
• Outside: Prefix — 2012-04-29
• Prefix with biology — 2011-09-07
• Prefix with skeleton — 2011-09-06
• Outer: Prefix — 2011-07-06
• Prefix with sphere — 2011-02-15
• Skeletal opening? — 2011-01-23
• Prefix with biology — 2011-01-07
• Prefix with skeleton — 2010-10-03
• Prefix with biology — 2009-12-01
• Prefix with skeleton — 2009-11-30
• Skeletal opening? — 2009-05-23
• Outer: Prefix — 2008-11-24
• Prefix with skeleton — 2007-01-30
• Prefix with skeleton — 2005-09-27
• Outer: Prefix — 2004-04-21
• Prefix with skeleton — 2003-06-25
• Outside: Prefix — 2003-01-16
• Skeleton's head? — 2002-05-19
• Outside: Prefix — 2001-04-25
• Outer: Prefix — 2000-08-07
• Outer: Prefix — 2000-05-24
• Prefix with skeleton — 1998-08-10
• Prefix with biology — 1998-01-04
• Prefix with biology — 1997-09-27
• Prefix with sphere — 1997-06-14
• Outside: Prefix — 1996-08-05