Eldonia
ludwigi
Eldonia ludwigi is a good example of a problematic fossil
organism. Eldonia and Eldonia-like fossils are known from
scattered localities around the world, but they are concentrated in Cambrian
soft-bodied fossil deposits, such as British Columbia’s Burgess Shale (see
introductory comments) and China’s Chengjiang deposit.
The slab shown below has four specimens of Eldonia
ludwigi Walcott, 1911. Eldonia had a nonmineralized,
medusiform, disc-shaped body with radiating structures, apparent tentacular
organs, and a coiled gut (usually very dark-colored). Early
interpretations held that Eldonia was a holothurian (a sea
cucumber). This view may be correct, but Eldonia and Eldonia-like
organisms are often now considered to be lophophorates (Superphylum
Lophophorata, which includes several familiar groups: brachiopods, bryozoans,
entoprocts, and phoronids). Who knows?
The Eldonia ludwigi slab shown below comes from
the Burgess Shale Lagerstätte of southeastern British Columbia,
Canada. These organisms are entirely nonmineralizing, and many details of
their soft-part anatomy are readily discerned.
Eldonia ludwigi Walcott, 1911 (centimeter scale) from the Burgess
Shale (Middle Cambrian) above Field, British Columbia, southwestern Canada.
YPM 5824 (Yale University’s Peabody Museum, New
Haven, Connecticut, USA)
Eldonia ludwigi Walcott, 1911 (diameter ~3 to ~3.5 cm across) from
the Burgess Shale (Middle Cambrian) above Field, British Columbia, southwestern
Canada.
YPM 5824 (Yale University’s Peabody Museum, New
Haven, Connecticut, USA)
Eldonia ludwigi Walcott, 1911 (diameter ~1.8 cm across) from the
Burgess Shale (Middle Cambrian) above Field, British Columbia, southwestern
Canada.
YPM 5824 (Yale University’s Peabody Museum, New
Haven, Connecticut, USA)