Carapace architecture of Sulcella (Postsulcella) testis (st = stragulum), from Adamczak (2003).

Belongs within: Platycopida.

The Cavellinidae are a group of ostracods known from the Middle Silurian to the lower Middle Triassic. They are ancestral to the later Cytherellidae, from which they differ in retaining a plesiomorphic random aggregate muscle scar pattern (Adamczak 2003). Members of the genus Cavellina have the carapace oblong to ovate in lateral view, with the dorsum moderately arched, and subovate in dorsal view with the posterior end thicker than the anterior, especially in female specimens (Benson et al. 1961).

The august history of filter-feeding ostracods
Published 25 July 2011

Today’s post subject, the Cavellinidae, were a family of ostracods that were around from the Middle Silurian period to the Middle Triassic (Adamczak 2003a). And for those of you unfamiliar with ostracods: you lucky, lucky bastards. They’re horrible.

I exaggerate slightly. Ostracods are a group of crustaceans that spend their lives enclosed in a pair of shells, superficially a bit like a bivalve, However, what they primarily are is very, very small (often less than a millimetre in total length), which makes them very difficult to work with as identification often requires dissecting out the (even smaller, needless to say) appendages hidden within the shells. Fortunately, I’ve personally managed so far to avoid being caught in ostracod purgatory, but many of my acquaintances have not been so fortunate. In the case of fossil ostracods like today’s subjects, it is generally only the valves themselves and not any of the internal parts that are preserved to be of concern, but they’re still small enough overall to hardly be counted as simple to work with.

External dorsal and lateral views of the carapace of each sex of the Silurian Gotlandella martinssoni, from Adamczak (2003a) (adr = admarginal ridge, mr = marginal ridge).

Cavellinids belong to a group of ostracods called the Platycopina, so-called because of their relatively flat sides. Among the modern fauna, platycopines are represented only by the genus Cytherella, whose distant ancestors were almost certainly among the species assigned to the Cavellinidae (Adamczak 2003a), so the ‘extinction’ of the cavellinids in the Triassic is really a pseudo-extinction as they were replaced by the descendant cytherellids. As befits its phylogenetic isolation from other living ostracods, Cytherella is an oddity in the modern fauna, being one of the few ostracod lineages to make a living as filter-feeders. The rear part of the carapace is expanded on the inside to form a brood chamber in which the eggs are nursed. It has been suggested that the evolution of filter-feeding and of the brood chamber were connected (Adamczak 2003b): as water is drawn in by the process of filter-feeding, it circulates around the brood chamber to keep the contents, whether eggs or newly hatched larvae, oxygenated. The constant flow of water also brings more oxygen to the adult’s own gills than it would receive passively, so Cytherella are able to live in places with less dissolved oxygen than other ostracods (Lethiers & Whatley 1994).

Internal view of right valve of the Middle Devonian Birdsallella eifeliensis, from Adamczak (2003a). Abbreviations: cg = contact groove (where the left valve is nestled); li = limen (the inner partition separating off the probable brood chamber).

Though preserved appendages have not yet been recorded from any cavellinid, their valve morphology is very similar to that of Cytherella: closely sized valves (the right is only slightly larger and slightly overlapping the left), with the line of contact between the valves is fairly straight along the underside, and the valves gaping open slightly at the front but tightly closed towards the back. A constriction on the inside of the valve also indicates the presence of a Cytherella-like brood chamber, and like Cytherella the outer surface of the carapace is fairly smooth. In fact, the only really marked difference between cavellinids and cytherellids is the arrangement of the muscle scars indicating where the valves where held together: in Cytherella and fossil members of the Cytherellidae, the scars are arranged in a double row, while members of the Cavellinidae have the scars in a random cluster. Because of the similarities between cavellinids and Cytherella, it is inferred that cavellinids were also filter feeders. Filter-feeding ostracods seem to have been more diverse in the Palaeozoic than in the present, leading Lethiers & Whatley (1994) to suggest that the Palaeozoic marine environment may have contained lower oxygen levels in many places than the modern environment. However, this line of reasoning was dismissed by Becker (2005), who felt that there was no reason to assume that fossil filter-feeders would necessarily show the same preference for low-oxygen environments as modern Cytherella. Instead, Becker has argued that strongly calcified ostracods like cavellinids are indicative of relatively high energy environments in shallow coastal waters (Adamczak 2003a).

Systematics of Cavellinidae

Characters (from Adamczak 2003a): Typically oval lateral carapace outline; right valve consistently larger, overreaching all around the smaller; contact of valves holosolenic; stragular process present; domiciliar dimorphism kloedenellid, i.e. in heteromorphs brood chamber always separated by an inner partition (limen); random aggregate muscle scar patterns.

<==Cavellinidae [Cavellininae, Volganellacea, Volganellidae]
    |--Reubenella avnimelechi Sohn 1968A03
    |--Alatacavellina Wang 1983A03
    |    `--*A. ovata Wang 1983A03
    |--Chapmanites Krömmelbein 1954A03
    |    `--*C. crassus Krömmelbein 1954A03
    |--Facticavellina Wang & Cao 1997A03
    |    `--*F. reliqua Wang & Cao 1997A03
    |--Uchtovia Egorov 1950A03
    |    `--*U. polenovae Egorov 1950A03
    |--‘Uralina’ Rozhdestvenskaya 1962 non Schuchert & LeVene 1929A03
    |    `--*U. uralica Rozhdestvenskaya 1962A03
    |--Menoeidina Stewart 1936BB61
    |    `--*M. subreniformis Stewart 1936BB61
    |--Paracavellina Cooper 1941BB61
    |    `--*P. elliptica Cooper 1941BB61
    |--Platychilella Cooper 1942 [=Platychilus Cooper 1941 nec Jakolev 1874 nec Cossmann 1888]BB61
    |    `--*P. ovoides (Cooper 1941) [=*Platychilus ovoides]BB61
    |--Tetratylus Cooper 1941BB61
    |    `--*T. elliptica Cooper 1941BB61
    |--Voronina Polenova 1952BB61
    |    `--*V. voronensis Polenova 1952BB61
    |--Donellina Egorov 1950 (n. d.)M61, BB61
    |    `--*D. grandis Egorov 1950BB61
    |--Sulcocavellina Polenova 1952 (n. d.)M61, BB61
    |    `--*S. incognita Polenova 1952BB61
    |--Timanella Egorov 1950M61
    |    `--*T. typica Egorov 1950M61
    |--Ellesmeria Tolmachov 1926 (n. d.)M61, BB61
    |    `--*E. ovata Tolmachov 1926BB61
    |--Sansabelloides Harris & Lalicker 1932 [incl. Semilukiella Egorov 1950]A03
    |    |--S. texana (Warthin 1930) [=Jonesina texana; incl. Sulcella harrisi Bradfield 1935, *Sansabelloides harrisi]A03
    |    `--*Semilukiella’ zaspelovae Egorov 1950A03
    |--Volganella Sharapova & Mandelstam 1956BB61
    |    |--*V. magna Spizharsky 1956BB61
    |    `--V. spizharskyiBB61
    |--Birdsallella Coryell & Booth 1933A03 (see below for synonymy)
    |    |--*B. simplex Coryell & Booth 1933A03
    |    |--*Cavellinella [sensu Polenova & Zaspelova]’ batalinaeA03
    |    |--*Cavellinella [sensu Bradfield]’ casei Bradfield 1935A03
    |    `--B. eifeliensis Adamczak 1968A03
    |--Kloedenellitina Egorov 1950 [incl. Houhongfeiella Olempska 1999, Muhuaella Olempska 1999]A03
    |    |--*K. sygmaeformis (Batalina 1941) [=Beyrichia sygmaeformis]A03
    |    |--*Houhongfeiella’ microspinosa Olempska 1999A03
    |    |--K. pseudosygmaeformis Egorov 1950A03
    |    `--*Muhuaella’ spinosa Olempska 1999A03
    |--Sulcella Coryell & Sample 1932A03
    |    |--S. (Sulcella)A03
    |    |    |--*S. (S.) sulcata Coryell & Sample 1932A03
    |    |    `--S. (S.) kloedenellides Adamczak 1968A03
    |    `--S. (Postsulcella Adamczak 1968)A03
    |         |--S. (*P.) testis Adamczak 1968A03
    |         `--S. (P.) postuma Becker 1965A03
    `--Cavellina Coryell 1928HM04 [incl. Alveus Hamilton 1942A03, AlvenusA03]
         |  i. s.: C. bellerophonellaFP12
         |         *Alveus’ depressus Hamilton 1942 [=Alvenus depressus]A03
         |         C. glandellaCB86
         |         C. mesodevonicaBB61
         |--C. (Cavellina)HM04
         |    |--*C. (C.) pulchella Coryell 1928A03
         |    |--C. (C.) jolliffana (Bradfield 1935) [=Cytherella jolliffana]HM04
         |    |--C. (C.) rohrensis Becker 1965A03
         |    `--C. (C.) symmetrica (Payne 1937)HM04
         `--C. (Invisiblia Polenova 1960)A03
              `--C. (*I.) indistincta Polenova 1955A03

Birdsallella Coryell & Booth 1933A03 [=Birdsalella (l. c.)M61; incl. Cavellinella Bradfield 1935A03, Cavellinella Polenova & Zaspelova in Polenova 1953 non Bradfield 1935A03]

*Type species of generic name indicated


[A03a] Adamczak, F. J. 2003a. The platycopine dynasty. 2. Family Cavellinidae Egorov, 1950. Authentic platycopines. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 229 (3): 375–391.

Adamczak, F. J. 2003b. The early platycopine dynasty (Ostracoda; Palaeozoic). Senckenbergiana Lethaea 83 (1–2): 53–59.

Becker, G. 2005. Functional morphology of Palaeozoic ostracods: phylogenetic implications. Hydrobiologia 538: 23–53.

[BB61] Benson, R. H., J. M. Berdan, W. A. van den Bold, T. Hanai, I. Hessland, H. V. Howe, R. V. Kesling, S. A. Levinson, R. A. Reyment, R. C. Moore, H. W. Scott, R. H. Shaver, I. G. Sohn, L. E. Stover, F. M. Swain & P. C. Sylvester-Bradley. 1961. Systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt Q. Arthropoda 3: Crustacea: Ostracoda pp. Q99–Q421. Geological Society of America and University of Kansas Press.

[CB86] Chen D.-Q. & Bao H. 1986. Lower Permian ostracodes from the Chihsia Formation of Jurong and Longtan, Jiangsu Province. Acta Micropalaeontologica Sinica 3 (2): 107–132.

[FP12] Farabegoli, E., & M. C. Perri. 2012. Millennial physical events and the end-Permian mass mortality in the western Palaeotethys: timing and primary causes. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 719–758. Springer.

[HM04] Hoare, R. D., & G. K. Merrill. 2004. A Pennsylvanian (Morrowan) ostracode fauna from Texas. Journal of Paleontology 78 (1): 185–204.

Lethiers, F., & R. Whatley. 1994. The use of Ostracoda to reconstruct the oxygen levels of Late Palaeozoic oceans. Marine Micropaleontology 24 (1): 57–69.

[M61] Moore, R. C. 1961. Supplement—USSR treatise on Ostracoda. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt Q. Arthropoda 3: Crustacea: Ostracoda pp. Q422–Q429. Geological Society of America and University of Kansas Press.

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