Theelia Ludwig 1889

Theelia Ludwig, 1889 and Theelia Ludwig, 1891

The genus name Theelia was mentioned by Ludwig on page 89 (fascicle 4 of Ludwig 1889-1892 = Ludwig 1889) for the first time, but the formal diagnosis (within the Dendrochirotida) did not appear before page 349 (fascicles 13/14 of Ludwig 1889-1892 = Ludwig 1891b; cf. also Waterhouse 1902: p. 372, Schulze et al. 1938: p. 3449 and Neave 1940: p. 459).

This name for a holothurian genus was also erected at the same time by Charles Schlumberger (1825–1905) in describing isolated fossil holothurian ossicles from Paleogene strata of the Paris Basin (Schlumberger 1888, 1890; cf. also Schulze et al. 1938: p. 3449 and Neave 1940: p. 459). Theelia Schlumberger, 1890 belongs (as originally described) to the Chiridotidae, covering fossil representatives related to Chiridota. This genus name is widely in use within holothurian palaeontology (e.g., Croneis & McCormack 1932; Frizzell & Exline 1956, 1958, 1966; Soodan 1991, 1993; Gilliland 1992; Sepkoski 2002; Reich 2003, 2013), but is in need of revision since representatives of Theelia (>80 recorded from Carboniferous to Miocene strata; Reich 2013) can be assigned to chiridotids, myriotrochids, and synaptids (e.g., Gilliland 1993).

However, Theelia Ludwig, 1891 in contrast, was only used or mentioned by Hubert Ludwig (Ludwig 1894,

1898), by some of his students (e.g., Erwe 1913) and others (e.g., Bather 1900; Pawson 1969, 1971a). Ludwig

(1889–1892) listed several species within his new genus:

(1) Theelia disciformis (Théel) (Ludwig 1891b: p. 350) [= Psolidium disciformis (Théel, 1886)];

(2) Theelia incerta (Théel) (Ludwig 1891b: p. 350) [= Psolidium incertum (Théel, 1886) = Psolidium poriferum (Studer, 1876)];

(3) Theelia cataphracta (Selenka) (Ludwig 1889: p. 89, 95, 143; 1891b: p. 350) [= Ceto cuvieria Gistel, 1848];

(4) Theelia ambulator (Bell) (Ludwig 1889: p. 107, footnote) [= uncorrected spelling of ambulator after moving the species from Psolus (generic name masculine) to Theelia (generic name feminine); this was corrected by Ludwig in the enclosed "Erratum sheet" bounded to the whole volume];

(5) Theelia ambulatrix (Bell) (Ludwig 1891b: p. 350) [= Ceto cuvieria Gistel, 1848].

Ludwig himself did not accept the genus name Theelia introduced by Schlumberger because he had mentioned the name earlier (cf. discussion in Ludwig 1891b: p. 445). However, partially due to this, Marthe Deflandre-Rigaud (1902–1987) introduced the name Chiridotites (Deflandre-Rigaud in Deflandre & Deflandre-Rigaud 1949) within the "ordo militaris" scheme (outside the ICZN) of Carey Croneis (1938) to replace Theelia Schlumberger, 1890 (e.g., Deflandre-Rigaud 1950, 1953, 1957, 1961, 1962). The genus Chiridotites was accepted as valid by Donald L. Frizzell (1906–1972) and his wife Harriet Exline (1909–1968), but is unequivocally a younger synonym of Theelia Schlumberger, 1890 (e.g., Frizzell & Exline 1956: p. 114).

In conclusion, Theelia Ludwig, 1889 appears to be a nomen nudum, and Theelia Ludwig, 1891 is a junior homonym of Theelia Schlumberger, 1890 and both Theelia Ludwig are junior synonyms of Ceto Gistel, 1848 (p. p.), Stolinus Selenka, 1867 (p. p.), Hypopsolus Bell, 1883 (p. p.), and Psolidium Ludwig, 1886a (p. p.).