Earliest ontogeny of Lower Palaeozoic brachiopodsStaff: M.G. Bassett & L.E. Popov
Understanding of the early life history of fossil and recent brachiopods continues to be of great importance in phylogenetic reconstructions. However, the early ontogeny or development of many Early Palaeozoic rhynchonelliform brachiopods remains poorly understood. In particular, the ontogeny of strophomenates requires further study, because newly obtained data on the ontogeny of the Order Billingsellida, which is commonly considered to represent the ancestral stock of all strophomenates, suggests that they are fundamentally different from the Recent rhynchonellates. Not only did they have a planktotrophic larvae (at least in some taxa), but most importantly they exhibit a different sequence of mantle and shell formation, as well as adult attachment. The ontogeny of the Billingsellidawas (with the exception of having a planktotrophic larva) probably closely comparable to that described in recent Novocrania. It is possible that the sequence of changes from the larval attachment by the posterior part of the body to an adult attachment by the ventral side of the body may represent plesiomorphic characters inherited by both groups from the Chileata. Study of the rhynchonelliformean and craniiformean brachiopod brachiopod ontogeny and in particular time and characters of transition from planktotrophic to leicitotrophic larvae in various brachiopods has also important implication in understanding of the early Palaeozoic brachiopod biogeography.
Popov, L. E., Egerquist, E., and Holmer, L. E. 2007. Earliest ontogeny of Middle Ordovician rhynchonelliform brachiopods (Clitambonitoidea and Polytoechioidea): implications for brachiopod phylogeny. Lethaia, 40, 85-96.
Holmer, L.E., Pettersson Stolk, S. Skovsted, C.B., Balthasar, U. and Popov, L.E. 2009. The enigmatic Early Cambrian Salanygolina - a stem group of rhynchonelliform chileate brachiopods? Palaeontology, 52, 1-10.