Terebratulina unguicula, copyright Florida Museum of Natural History.

Belongs within: Terebratulida.

The cancellothyridids: a modern success story
Published 3 June 2015

As has been noted on this site more than once before, brachiopods are a group of animals probably more familiar to the student of palaeontology than of zoology. From the brief gloss that tends to be their only coverage in textbooks, one might be forgiven for thinking them all but inconsequential in the modern fauna. But where conditions suit them (usually sheltered locations where low levels of light and water flow favour their slow metabolisms over the higher energy requirements of bivalves), brachiopods can still be abundant, and even dominant.

Northern lamp shells Terebratulina septentrionalis, from Oceana.

One of the most diverse families of brachiopods in the modern fauna is the Cancellothyrididae. Cancellothyridids first make their appearance in the Jurassic, becoming widespread in the Cretaceous (Cooper 1973). Members of this family have shells with a large foramen (the opening at the rear of the shell through which passes the pedicel or stalk by which the brachiopod is attached to its substrate), usually with the deltidial plates surrounding the foramen greatly reduced. The main defining feature of the Cancellothyrididae is the structure of the brachidium, the skeletal structure that provides the support for the base of the lophophore, the tentacle-like feeding structures. In cancellothyridids, the two sides of the brachidium coalesce in the middle to form a tube.

Dorsal valve of the Cretaceous cancellothyridid Cricosia filosa in (A) lateral, (B) ventral and (C) posterior views, from Cooper (1973), showing the tubular brachidium.

The brachidium does not extend into the arms of the lophophore, which are instead strengthened by unattached spicules. The tubular shape of the brachidium distinguishes the Cancellothyrididae from the closely related family Chlidonophoridae, whose members share the large posterior foramen but have the two sides of the brachidium open in back. Cooper (1973) recognised two subfamilies of cancellothyridids, the living Cancellothyridinae and the Cretaceous Cricosiinae; the cricosiines have the tubular section of the brachidium longer and narrower than the cancellothyridines.

Modern cancellothyridids are found in the Indo-Pacific and the North Atlantic, but seem to be absent from the South Atlantic. The majority of living species are included in the widespread genus Terebratulina, with the other living genera all having restricted distributions in the Indo-Pacific. However, a molecular phylogenetic analysis of species of Terebratulina and the Australian genus Cancellothyris by Lüter & Cohen (2002) indicated that both Atlantic Terebratulina and Cancellothyris were nested within Pacific Terebratulina. Paraphyly of the widespread genus would also correlate with its palaeontological distribution: while the other genera are known only from the Recent fauna, Terebratulina has a fossil record dating right back to the origins of the cancellothyridids in the Jurassic (Muir-Wood 1965). Lüter & Cohen (2002) tentatively suggested the possibility of a North Pacific origin for Terebratulina (and, by implication, for Cancellothyrididae as a whole), with dispersal to the North Atlantic occurring through the gap between North and South America before formation of Central America. Their preference for this option rather than the alternative of dispersal through the Tethys (the seaway that once separated Africa from Eurasia) was based on their estimate via molecular clock of a separation of about 100 million years between the Atlantic and Pacific species, supposedly too early for the Tethys option. However, it must be stressed that their sampling of even modern cancellothyridid diversity was not comprehensive. A trans-Tethys dispersal of cancellothyridids may also be indicated by the presence of the fossil genus Rhynchonellopsis in the lower Oligocene of northern Europe (Muir-Wood 1965). Of course, there is no inherent reason why cancellothyridids could not have travelled in both directions!

Systematics of Cancellothyrididae
Cancellothyrididae [Cancellothyridae, Cancellothyridoidea]M-WS65
|--Agulhasia King 1871 [Agulhasiinae]M-WS65
| `--*A. davidsoni King 1871M-WS65
|--Orthothyris Cooper 1955 [Orthothyridinae]M-WS65
| `--*O. radiata Cooper 1955M-WS65
| |--Meonia Steinich 1963M-WS65
| | `--*M. semiglobularis (Posselt 1894) [=Terebratula semiglobularis]M-WS65
| `--Eucalathis Fischer & Oehlert 1890M-WS65
| |--*E. murrayi (Davidson 1878) [=Terebratulina murrayi]M-WS65
| `--E. ergasticaM-WS65
| |--Gisilina Steinich 1963M-WS65
| | `--*G. gisii (Roemer 1840) [=Terebratula gisii]M-WS65
| |--Rugia Steinich 1963M-WS65
| | `--*R. tenuicostata Steinich 1963M-WS65
| `--Chlidonophora Dall 1903M-WS65
| |--*C. incerta (Davidson 1878) [=Terebratulina incerta]M-WS65
| `--C. chuniM-WS65
`--Cancellothyridinae [Cancellothyrinae]M-WS65
|--Cancellothyris Thomson 1926M-WS65
| `--*C. hedleyi (Finlay 1927)M-WS65 (see below for synonymy)
|--Rhynchonellopsis Vincent 1893M-WS65
| `--*R. nysti (Bosquet 1862) [=Terebratulina nysti]M-WS65
|--Sendaithyris Hatai 1940M-WS65
| `--*S. otutumiensis Hatai 1940M-WS65
|--Surugathyris Yabe & Hatai 1934M-WS65
| `--*S. surugaensis Yabe & Hatai 1934 [=*S. (Terebratulina) suragaensis]M-WS65
|--Murravia Thomson 1916M-WS65
| |--*M. catinuliformis (Tate 1896) (see below for synonymy)M-WS65
| `--M. exarataM-WS65
`--Terebratulina d’Orbigny 1847M-WS65
|--T. retusa (Linnaeus 1758) (see below for synonymy)M-WS65
|--T. crossiM-WS65
|--T. elongata Davidson 1874HB93
|--T. hataianaR97
|--T. lataK79
|--T. radiata [=Terebratula (Terebratulina) radiata]C64
|--T. septentrionalisWR65
|--T. serpentisH04
|--T. suessi [incl. T. scouleri]H86
`--T. unguiculaM-WS65

Cancellothyrididae incertae sedis:
Disculina Eudes-Deslongchamps 1884M-WS65
`--*D. hemisphaerica (Sowerby 1826) [=Terebratula hemisphaerica]M-WS65
Dzirulina Nutsubidze 1945M-WS65
`--*D. dzirulensis (Anthula 1899) [=Terebratula dzirulensis]M-WS65
Phymatothyris Cooper & Muir-Wood 1951 [=Pallasiella Renz 1932 non Sars 1895]M-WS65
`--*P. kerkyraea (Renz 1932) [=*Pallasiella kerkyraea]M-WS65
Plectoidothyris Buckman 1918M-WS65
`--*P. polyplecta (Buckman 1901) [=Terebratula polyplecta]M-WS65
Plectothyris Buckman 1918M-WS65
`--*P. fimbria (Sowerby 1822) [=Terebratula fimbria]M-WS65
Postepithyris Makridin 1960M-WS65
`--*P. cincta (Cotteau 1857) [=Terebratula cincta]M-WS65

*Cancellothyris hedleyi (Finlay 1927)M-WS65 [=Terebratulina hedleyiM-WS65, C. australis Thomson 1927M-WS65, Terebratula cancellata Koch in Küster 1844 non Eichwald 1829M-WS65, Terebratulina cancellataF27]

*Murravia catinuliformis (Tate 1896) [=Terebratulina catinuliformis, T. davidsoni Etheridge 1876 non Boll 1856]M-WS65

Terebratulina retusa (Linnaeus 1758) [=Anomia retusa; incl. A. caputserpentis Linné 1767 non Linnaeus 1758, *Terebratulina caputserpentis]M-WS65

*Type species of generic name indicated


[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

Cooper, G. A. 1973. Fossil and recent Cancellothyridacea (Brachiopoda). Tohoku Univ., Sci. Rep., 2nd Ser. (Geol.), Special Volume 6: 371–390.

[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.

[HB93] Harper, D. A. T., C. H. C. Brunton, L. R. M. Cocks, P. Copper, E. N. Doyle, A. L. Jeffrey, E. F. Owen, M. A. Parkes, L. E. Popov & C. D. Prosser. 1993. Brachiopoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 427–462. Chapman & Hall: London.

[H86] Hutton, F. W. 1886. Notes on some Australian Tertiary fossils. Proceedings of the Linnean Society of New South Wales, series 2, 1 (2): 481–482.

[K79] Kauffman, E. G. 1979. Cretaceous. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A418–A487. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

Lüter, C., & B. L. Cohen. 2002. DNA sequence evidence for speciation, paraphyly and a Mesozoic dispersal of cancellothyridid articulate brachiopods. Marine Biology 141: 65–74.

Muir-Wood, H. M. 1965. Mesozoic and Cenozoic Terebratulidina. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 2 pp. H762–H816.

[M-WS65] Muir-Wood, H. M., F. G. Stehli, G. F. Elliott & K. Hatai. 1965. Terebratulida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 2 pp. H728–H857. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).

[R97] Richardson, J. R. 1997. Biogeography of articulated brachiopods. In: Kaesler, R. L. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda, Revised vol. 1. Introduction pp. 463–472. The Geological Society of America: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[WR65] Williams, A., & A. J. Rowell. 1965. Brachiopod anatomy. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 1 pp. H6–H57. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).

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