Complex sentence: Thomas Starling Sullivant (1854--1926) was an influential American cartoonist who signed his work T. S. Sullivant, whose work appeared most frequently in the pages of the humorous "Life" magazine.
Split into simpler sentences: Thomas Starling Sullivant (1854--1926) was an influential American cartoonist who signed his work T. S. Sullivant. His work appeared most frequently in the pages of the humorous "Life" magazine.