The arthropod head problem is a long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. While the dispute has historically centered on the exact make-up of the insect head, it has been widened to include other living arthropods such as the crustaceans and chelicerates; and fossil forms, such as the many arthropods known from exceptionally preserved Cambrian faunas. While the topic has classically been based on insect embryology, in recent years a great deal of developmental molecular data has become available. Dozens of more or less distinct solutions to the problem, dating back to at least 1897, have been published, including several in the 2000s.
The arthropod head problem is popularly known as the "endless dispute", the title of a famous paper on the subject by Jacob G. Rempel in 1975, referring to its apparently intractable nature. Although some progress has been made since that time, the precise nature of especially the labrum and the pre-oral region of arthropods remain highly controversial.
Read more about Arthropod Head Problem: Background, Head Components, The Acron Concept, Molecular Development and The Arthropod Head Problem, Areas of Agreement, Areas of Disagreement, The Head of Onychophorans, Fossil Evidence, Assessment
Famous quotes containing the words head and/or problem:
“He was thoughtful and grave—but the orders he gave
Were enough to bewilder a crew.
When he cried “Steer to starboard, but keep her head larboard!”
What on earth was the helmsman to do?”
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“What had really caused the women’s movement was the additional years of human life. At the turn of the century women’s life expectancy was forty-six; now it was nearly eighty. Our groping sense that we couldn’t live all those years in terms of motherhood alone was “the problem that had no name.” Realizing that it was not some freakish personal fault but our common problem as women had enabled us to take the first steps to change our lives.”
—Betty Friedan (20th century)