Fossil Record
Fossils of sipunculans are extremely rare, and are only known from two genera (Archaeogolfingia and Cambrosipunculus) from the Cambrian Chengjiang biota in China. These fossils appear to belong to the crown group, and illustrate that sipunculans have changed little since the early Cambrian.
Some scientists consider a close relationship of sipunculans and the extinct hyoliths, operculate shells from the Palaeozoic, with which they share the helically twisted gut. If true, the anal plate of some sipunculans might be a remnant of a shell similar to that of hyoliths.
Read more about this topic: Sipuncula
Famous quotes containing the words fossil and/or record:
“The earth is not a mere fragment of dead history, stratum upon stratum like the leaves of a book, to be studied by geologists and antiquaries chiefly, but living poetry like the leaves of a tree, which precede flowers and fruit,—not a fossil earth, but a living earth; compared with whose great central life all animal and vegetable life is merely parasitic.”
—Henry David Thoreau (1817–1862)
“The case of Andrews is really a very bad one, as appears by the record already before me. Yet before receiving this I had ordered his punishment commuted to imprisonment ... and had so telegraphed. I did this, not on any merit in the case, but because I am trying to evade the butchering business lately.”
—Abraham Lincoln (1809–1865)