Proof that Lingula (Brachiopoda) is not a living-fossil, and emended diagnoses of the Family Lingulidae, by Christian C. Emig
Lingula is often considered a "living-fossil" based on its supposed lengthy morphological conservatism owing to its absence of evolution, and its remarkable survival for more than 550 M.Y. This conclusion is based on the typical apparently unchanged "linguliform" shape of the shell. However the taxa of the family Lingulidae show morphological evolutionary changes despite the fact that the group appears panchronic among the Recent Brachiopoda. Consequently, traditional opinion that Lingula is a "living-fossil" should be rejected. Diagnoses of the Family Lingulidae and of its three genera are herewith emended.
CG2003_L01_CCE/index.html

On the history of the names Lingula, anatina, and on the confusion of the forms assigned them among the Brachiopoda, by Christian C. Emig
The first descriptions of Lingula were made from then extant specimens by three famous French scientists: Bruguière, Cuvier, and Lamarck. The genus Lingula was created in 1791 (not 1797) by Bruguière and in 1801 Lamarck named the first species L. anatina, which was then studied by Cuvier (1802). In 1812 the first fossil lingulids were discovered in the Mesozoic and Palaeozoic strata of the U.K. and were referred to Lingula on the basis of similarity in the form of the shell. In the 1840's other linguliform brachiopods from the Palaeozoic were described. The similarity of the shell form of the extant Lingula and these fossils led Darwin in 1859 to create the description "living fossil" in his book "On the Origin of Species". Thereafter, this Darwinian concept became traditional in that Lingula was considered to lack morphological evolutionary changes. Although denounced as scientifically incorrect for more than two decades, the concept still remains in many books, publications and Web sites, perhaps a witness to palaeontological conservatism
CG2008_A08/index.html

Schmidtites celatus (Obolida, Brachiopoda) from the "Obolus sands" (Upper Cambrian - Lower Ordovician) of Estonia, by Christian C. Emig
Large collections of the brachiopod obolid Schmidtites celatus have been gathered from Upper Cambrian-Lower Ordovician strata in four northern Estonian localities. The morphological features and the taxonomic characters of the genus and of the single species representing it are re-described and illustrated. New diagnoses are proposed based on characters of the shell and morphological traits that permit Schmidtites celatus to be compared with and distinguished from the other obolid genera occurring in the same samples or areas, i.e., Ungula ingrica, Oepikites, and Obolus apollinis which now includes specimens formerly described as Ungula convexa. Schmidtites celatus differs from them mainly in the arrangement of its musculature.
CG2006_A04/index.html

The distribution of worm borings in brachiopod shells from the Caradoc Oil Shale of Estonia, by Olev Vinn 
Abundant worm borings were found in some brachiopod shells (Clitambonites, Estlandia, Nicolella) from the Ordovician (Caradoc) oil shale in North Estonia. 9 of 21 brachiopod genera (43 %) have been bored. Excluding the size and thickness of valves, no common morphological feature discriminates the brachiopods with borings from those without them. The Trypanites are host-specific, and the frequency of bored valves varies from 6.5 % in Bekkerina to 51 % in Estlandia. The worm larvae preferred hosts with thick lamellose shells, such as those of the clitambonitids, especially Clitambonites schmidti. The boring organisms were size-selective; they preferred large adult specimens. The majority of the borings are oriented, and living hosts were preferred to dead shells. Some clitambonitidine brachiopods, like C. schmidti tolerated a large number of the borer's shafts in their valves. Few bored valves have the blister-like shell-repair structures in their interior.
CG2005_A03/index.html

New data on the lophophore anatomy of Early Cambrian linguloids from the Chengjiang Lagerstätte, Southwest China, by Zhi-Fei Zhang, De-Gan Shu, Jian Han & Jian-Ni Liu
A succession of developmental types in the lophophores of lingulid brachiopods is reported from the Early Cambrian Chengjiang deposits of South China. These types range from trocholophe, schizolophe to simple coiled spirolophe. Of Atdabanian age, this succession of forms is mirrored in the ontogeny of the lophophore of Recent linguloids, thus demonstrating a close similarity in the development of the lophophores of Cambrian and Recent forms. We illustrate also more than 10 extraordinary specimens with aberrant dispositions of the lophophoral arms that extend to unusual lengths either inside or outside the shell.
CG2004_L04/index.html

Tools for linguloid taxonomy: the genus Obolus (Brachiopoda) as an example, by Christian C. Emig 
This study points out some basic problems of linguloid systematics and proposes solutions for them. A taxonomic examination of the unique species of the genus Obolus found in the Upper Cambrian of Estonia and Russia, O. apollinis (= O. ruchini, O. transversus, O. rebrovi and Ungula convexa) is used as an example of a methodology employing all of the characters valid for distinguishing species of both extant and fossil Lingulidae. These characters are: - umbonal region; - body musculature; - septa or ridges; - main mantle canals - as established and figured by Emig (...) and Biernat and Emig (...). All of them have been determined to be taxonomically stable and have been studied and compared to take into account intraspecific variability; they should be used to describe or to redescribe any taxon of the superfamily Linguloidea. Characters of the shell and valves, such as shape, size, and dimensional ratios have no taxonomic value.
CG2002_A01_CCE/index.html

Understanding linguloid brachiopods: Obolus and Ungula as examples, by  Leonid E.Popov & Lars E. Holmer
Emig (...) re-examined the taxonomy of the genus Obolus Eichwald from the Middle Cambrian - earliest Ordovician of the East Baltic region as part of a proposal for a wholesale revision of the principles of linguloid systematics. He contended that previous taxonomic studies on Obolus and related forms were carried out erroneously using characters that have no taxonomic value. Emig's proposed revision is based mainly on the limited morphological diversity between fossil and Recent taxa within a single linguloid Family, the Lingulidae. However, the present study demonstrates the taxonomic validity of the diagnostic characters used for classification within the mostly extinct families of the Superfamily Linguloidea, for they exhibit far more variation in morphology. This study also shows that Emig has provided no satisfactory basis for his radical changes and revisions to the existing widely accepted taxonomy of the Cambrian to earliest Ordovician Obolidae of the East Baltic. Obolus Eichwald and Ungula Pander are shown to constitute distinctive and discrete genera comprising the species Obolus apollinis Eichwald, O. ruchini Khazanovitch et Popov, O. transversus (Pander), Ungula ingrica (Eichwald), U. inornata (Mickwitz), and U. convexa Pander.
CG2003_A06_LEP-LEH/index.html

Reply to L.E. Popov and L.E. Holmer (CG2003_A06_LEP-LEH): Obolid taxonomy, by Christian C. Emig
Since early in the 19th Century the taxonomy of fossil obolids has been the subject of numerous controversies (...), so the development of new criteria for their proper differentiation is mandatory. Based on the extant species of the family Lingulidae (...) and later applied to fossil taxa (...), new morpho-anatomical characters were established and their variability analysed. As a consequence, several shell structures commonly used to discriminate between genera and species of both extant and fossil taxa were determined to have no phylogenetic status. (...)
CG2003_A06R/index.html