An article published in the journal “Papers in Palaeontology” describes the discovery of a species of bryozoan called Jablonskipora kidwellae which constitutes an evolutionary missing link. These are the first modern bryozoans that grew in a structure and their study could help shed light on the evolution of these small invertebrates that live in colonies and are part of a phylum that emerged in the Cambrian period, about 500 million years ago.
Bryozoans, phylum Bryozoa or Ectoprocta, are typically aquatic animals that today exist in many different species that live in both sea and fresh water. They’re considered living fossils because they descend from ancient organisms, perhaps among the first multicellular life forms and among the first animals to evolve. They’re very different from other animals, so reconstructing their relationships with other phyla is a source of controversy. The consequence is that various proposals were made to group bryozoans with other phyla in larger taxonomic groups.
So far, scientists failed to understand how bryozoans survived for half a billion years and many changes in the world. But now Paul Taylor and Silviu Martha of the London Museum of Natural History believe they have discovered a missing link in the history of bryozoans in the species they named Jablonskipora kidwellae after University of Chicago’s geophysical scientists David Jablonski and Susan Kidwell.
Fossils belonging to this species were discovered in southeastern England, near Devon. They were discovered at the beginning of the 20th century but lived about 105 million years ago. It seems bizarre to talk about modern bryozoans referring to such ancient fossils but we’re talking about an extremely ancient phylum that for over 50 million years showed little diversity.
In particular, the order Cheilostomata or Cheilostomatida appeared only in the late Jurassic, about 150 million years ago. Jablonskipora kidwellae was attributed to this order, which about 100 million years ago showed a huge diversification. This is the period in which the discovered species lived, which according to the researchers shows key characteristics in their evolution.
The colony structure created by Jablonskipora kidwellae grows upwards. This may seem trivial but according to the researchers this is a crucial change because it allows the colony to tap the water that flows over the sea floor, to which a small part of these organisms is anchored. Creating that type of structure requires a different kind of union among individuals, an evolutionary leap that allowed a greater diffusion of bryozoans and their consequent diversification.
Bryozoans are not exactly the organisms that raise the greatest interest, neither among scientists nor among the public. However, they represent a case of evolutionary success in which organisms that live in colonies managed to develop slowly, under all points of view, and prosper for a very long time.