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Zootaxa. 2018 Jul 6;4444(1):1-24. doi: 10.11646/zootaxa.4444.1.1.

Extreme reduction of morphological characters: a type of brachidial development found in several Late Cretaceous and Recent brachiopod species-new relationships between taxa previously listed as incertae sedis.

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Royal Belgian Institute of Natural Sciences, O.D. Earth and History of Life, Vautier Street, 29, 1000 Brussels, Belgium..


Size reduction and development of a simplified brachidial structure occurred several times during the long evolution of the Phylum Brachiopoda. Even Recent forms may be micromorphic and paedomorphic with reduced brachidia or none at all. A revision of the Maastrichtian (Late Cretaceous) Terebratella (Morrisia?) suessi Bosquet, 1859 has allowed us to erect a new genus, Jagtithyris gen. nov., because its singular brachidium development does not match any platidiid structure. Such a brachidium has also been observed in another European Late Cretaceous brachiopod, which indicates that this type was not a unique morphological curiosity. This species is the micromorphic Campanian-Maastrichtian Leptothyrellopsis polonicus Bitner Pisera, 1979, which has brachidial structures in common with Jagtithyris suessi comb. nov., although a number of differences have been observed. The genera Leptothyrellopsis and Jagtithyris gen. nov., are included in a new family, Jagtithyrididae fam. nov. During an ongoing revision of extant brachiopod faunas we have been led to recognize a link between this family and representatives of the genus Simplicithyris Zezina, 1976. The taxonomic position of this peculiar group is also discussed.


Mollusca, Rhynchonelliformea, Jagtithyrididae fam. nov., Cretaceous, Holocene, brachidial simplification, new taxa

[Indexed for MEDLINE]

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