Iotuba chengjiangensis (sometimes mis-spelt Lotuba[
]) is a 515 million year old Cambrian worm known from the Chengjiang biota.[ Ancient fossils shed new light on evolution of sea worm] Originally interpreted as a phoronid, the organism is now recognized as an annelid cage worm affiliated with the Flabelligeridae and Acrocirridae, which Zhang et al grouped together in the new superfamily Flabelligeroidea.[
]
Anatomy
Iotuba was a couple of centimetres long and half a centimetre in width. Internally it is characterized by a through gut flanked by a pair of boudinaged tubes interpreted as nephridia ("kidneys"). Its trunk is adorned with small conical papillae ("microspines"). Its "head" bears a pair of tentaculate, horseshoe-shaped branchiae ("gills"), and can be withdrawn into the body; it is surrounded by a cage of spines interpreted as chaetae, equivalent to those of the flabelligerid "cage worms".[
]
History of interpretation
Iotuba was originally interpreted as a phoronid based on a misinterpretation of the single then-available specimen as harbouring a U-shaped gut and
Previous comparisons to ecdysozoan worms such as Louisella.[ ] have been ruled out based on the construction of the anterior region and other morphological details.
Occurrence
Iotuba has been reported from the Chengjiang biota, with a possible additional occurrence in the Haiyan Lagerstätte
