Evolution
Linguliformean brachiopods represent the first certain appearance of brachiopods in the fossil record.
There is currently a lot of research into the origins of the brachiopoda.
Some genetic studies show that they are very closely related to the Phoronida and therefore may share a common ancestor with them. Other similar studies show that the phoronids are actually a naked brachiopod.
Other current research is slowly piecing together the ancestors of the brachiopods and offering insights into how their unique morphology evolved and from what type or organism it did so from.
Linguliformean brachiopods appear at the base of the Cambrian (some 530 million years ago) and represent the first certain appearance of brachiopods in the fossil record.
Within the fossil record there are hints that their behaviour has changed; some fossil from China suggest that they may not always have been infaunal, instead resting on the sediment surface. In addition, the habitat they are found in varies quite considerably from estuaries to deep sea settings.
Within the Linguloidea there is exceptional morphological conservatism; ligulids from the base of the Cambrian right through the Palaeozoic, Mesozoic and up to the modern day are very similar in their external appearance.
It has often been said that lingula is a living fossil in a similar manner to the modern Coelocanth (Latimeria chalumnae). This has all been based upon the external and sometime internal shell morphology.
It is only recently that soft tissue morphology of lower Palaeozoic fossil has come to light from exceptionally preserved specimens found in China. The soft tissue in these 500 million year old species shows that although the external shell morphology has remained remarkably consistent, the soft tissue morphology and anatomy has undergone some major changes.