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Craniidae Temporal range: Ordovician–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Petrocrania scabiosa encrusting the edge of a strophomenide brachiopod; Upper Ordovician of northern Kentucky.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Brachiopoda
Class:	Craniata
Order:	Craniida Waagen, 1885
Suborder:	Craniidina Waagen, 1885
Superfamily:	Cranioidea Menke, 1828
Family:	Craniidae Menke, 1828
Genera
See text.
Synonyms
Valdiviathyrididae

The Craniidae are a family of brachiopods, the only surviving members of the subphylum Craniiformea. They are the only members of the order Craniida, the monotypic suborder Craniidina, and the superfamily Cranioidea; consequently, the latter two taxa are at present redundant and rarely used.There are three living genera within Craniidae: Neoancistrocrania, Novocrania, and Valdiviathyris. As adults, craniids either live freely on the ocean floor or, more commonly, cement themselves onto a hard object with all or part of the ventral valve.

Like the burrowing lingulids, Craniids are inarticulate brachiopods. There are no outgrowths forming a hinge between both valves, nor is there any support for the lophophore. Unlike lingulids, which have shells consisting of apatite and organic material, craniids have shells composed mainly of calcium carbonate. No craniids are known to bear a pedicle at any development stage.

Evolution

Extinct craniids

Most craniid genera are extinct, known only from fossils like other craniiforms. Craniids first appeared in the later part of the Tremadocian, the first stage of the Lower Ordovician. In the Lower Ordovician, they were mostly restricted to peri-Gondwanan terranes (modern central Europe) in the South Polar region. By the Middle Ordovician, they had spread northwards to Baltica. In the Late Ordovician, their range expanded eastwards to Avalonia before crossing the Iapetus Ocean to Laurentia.

Craniid diversity and abundance was respectable but still fairly low during the Late Ordovician, and even lower through the rest of the Paleozoic. The craniid fossil record is patchy, with fossils unknown from the Upper Carboniferous, Upper Permian, and the entire Triassic. They reappear in the Oxfordian stage of the Late Jurassic and briefly regain their Ordovician level of diversity in the Late Cretaceous.

Living craniids

Craniids are remarkable for their slow rate of evolution. Approximately 11 species of this 480-million-year-old lineage still survive today, with minimal differences relative to their fossil counterparts. One species, Valdiviathyris quenstedti, has remained essentially unchanged for the last 35 million years or so. Although some evolution would have taken place in the meantime, this was essentially silent mutations and marginal adaptations to cooler habitat. Present-day Valdiviathyris are indistinguishable from fossils of the Late Eocene, and the genus cannot even be divided into chronospecies. V. quenstedti can be considered a living fossil and one of the oldest and most long-lived species known to science.

Valdiviathyris and Neoancistrocrania have occasionally been separated into their own family, Valdiviathyrididae, though few authors follow this suggestion. Craniscus has sometimes been cited as a fourth living craniid genus, based on "Craniscus japonica", a putative species from waters off Japan. Genetic evidence has clarified this misconception, revealing that "Craniscus japonica" actually represents a misattributed species of Neoancistrocrania.

List of genera

From the Treatise on Invertebrate Paleontology Part H, Revised (unless stated otherwise):

• †Acanthocrania Williams, 1943
• †Ancistrocrania Dall, 1877 = Cranopsis
• †Celidocrania Liu, Xhy, & Xue, 1985 (possible synonym of Acanthocrania)
• †Crania Retzius, 1781
• †Craniscus Dall, 1871
• †Conocrania Smirnova, 1996
• †Danocrania Rozenkrantz, 1964
• †Deliella Halamski, 2004
• †Isocrania Jäkel, 1902
• †Lepidocrania Cooper and Grant, 1974
• †Mesocrania Smirnova, 1997
• †Nematocrania Grant, 1976
• Neoancistrocrania Laurin, 1992
• Novocrania Lee and Bruton, 2001 = Neocrania
• †Orthisocrania Rowell, 1963
• †Petrocrania Raymond, 1911
• †Philhedra Koken, 1889
• †Pseudocrania McCoy, 1851
• Valdiviathyris Helmcke, 1940

Gallery

• Petrocrania (small rounded shells) encrusting an Ordovician strophomenide brachiopod
• Pseudocrania sp., from the Ordovician of Estonia
• Isocrania costata, from the Upper Cretaceous of The Netherlands
• Illustration of Novocrania anomala, a living craniid native to the North Atlantic

References

1. ^ Emig, Christian C.; Bitner, Maria Aleksandra; Álvarez, Fernando. "Craniiformea". Brachiopoda Database. Retrieved 7 June 2023.
2. Moore, R.C. (1965). Brachiopoda. Treatise on Invertebrate Paleontology. Vol. Part H., Volume 1. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. H6, H93. ISBN 0-8137-3015-5.
3. ^ Bassett, Michael G. (2000). "Chapter 2 (part): Craniida". In Kaesler, Roger L. (ed.). Part H, Brachiopoda (Revised). Volumes 2 & 3: Linguliformea, Craniiformea, and Rhynchonelliformea (part). Treatise on Invertebrate Paleontology. Boulder, Colorado; Lawrence, Kansas: Geological Society of America; University of Kansas. pp. 169–183. ISBN 0-8137-3108-9.
4. ^ Popov, Leonid E.; Holmer, Lars E.; Bassett, Michael G.; Pour, Mansoureh Ghobadi; Percival, Ian G. (2013). Harper, D.A.T.; Servais, T. (eds.). "Chapter 10: Biogeography of Ordovician linguliform and craniiform brachiopods". Geological Society, London, Memoirs. Early Palaeozoic Biogeography and Palaeogeography. 38 (1): 117–126. doi:10.1144/M38.10. ISSN 0435-4052.
5. Curry, Gordon B.; Brunton, Howard C. (2007). "Chapter 9: Stratigraphic Distribution of Brachiopods". In Selden, Paul A. (ed.). Part H, Brachiopoda (Revised). Volume 6: Supplement. Treatise on Invertebrate Paleontology. Boulder, Colorado; Lawrence, Kansas: Geological Society of America; University of Kansas. pp. 2901–2965. ISBN 978-0-8137-3136-0.
6. ^ Robinson, Jeffrey H.; Lee, Daphne E. (2007-03-01). "The recent and Paleogene craniid brachiopod, Valdiviathyris quenstedti Helmcke, 1940". Systematics and Biodiversity. 5 (1): 123–131. doi:10.1017/S1477200006002179. ISSN 1477-2000.
7. ^ Cohen, Bernard L.; Long, Sarah L; Saito, Michiko (2008). "Living craniids: preliminary molecular evidence of their inter-relationships". In Harper, David A.T.; Long, Sarah L.; Nielsen, Claus (eds.). Brachiopoda: Fossil and Recent. Fossils and Strata. Vol. 54. Wiley-Blackwell. pp. 283–287. doi:10.18261/9781405186643-2008-31. ISBN 978-1-4051-8664-3.
8. ^ Bassett, Michael G. (2007). "Chapter 4 (part): Craniida". In Selden, Paul A. (ed.). Part H, Brachiopoda (Revised). Volume 6: Supplement. Treatise on Invertebrate Paleontology. Boulder, Colorado; Lawrence, Kansas: Geological Society of America; University of Kansas. pp. 2591–2592. ISBN 978-0-8137-3136-0.
9. Brunton, C.H.C. (1968). "Silicified brachiopods from the Visean of County Fermanagh (II)". Bulletin of the British Museum (Natural History), Geology. 16: 8.
10. Emig, Christian C. (2009). "Nummulus brattenburgensis and Crania craniolaris (Brachiopoda, Craniidae)" (PDF). Carnets de Géologie (08). Archived from the original (PDF) on 2016-03-04. Retrieved 2014-08-05.

v t e Brachiopod orders
Linguliformea Lingulata †Acrotretida Lingulida †Siphonotretida †Paterinata Paterinida Craniiformea Craniata Craniida †Craniopsida †Trimerellida Rhynchonelliformea †Chileata Chileida Dictyonellida †Kutorginata Kutorginida †Obolellata Naukatida Obolellida Rhynchonellata †Athyridida †Atrypida †Orthida †Pentamerida †Protorthida Rhynchonellida †Spiriferida †Spiriferinida Terebratulida Thecideida †Strophomenata Billingsellida Orthotetida Productida Strophomenida

• Brachiopod families
• Extant Ordovician first appearances
• Craniata