CORNULITIDAE FISHER, 1962

Herringshaw, Liam G., Thomas, Alan T. & Smith, M. Paul, 2007, Systematics, shell structure and affinities of the Palaeozoic Problematicum Cornulites, Zoological Journal of the Linnean Society 150 (4), pp. 681-699 : 683

CORNULITIDAE FISHER, 1962

Remarks: Fisher (1962) erected the Cornulitidae as a family containing four genera – Cornulites Schlotheim, 1820 , Conchicolites Nicholson, 1872a , Cornulitella Howell, 1952 and Kolihaia Prantl, 1946 . Only Silurian species of Cornulites are described here, and a revision of the whole group is not attempted, but previously published descriptions and illustrations suggest that cornulitids have been excessively subdivided at generic level. For example, Cornulitella [a name proposed by Howell (1952) to replace Ortonia Nicholson, 1872b , which Howell showed to be preoccupied] was originally described by Nicholson (1872b) as separable from Cornulites on the grounds that its shell was smaller, entirely attached to other organisms, devoid of costae, and had a cellular structure restricted to just one side of the shell. However, this comparison was based on Cornulites being defined as a large, unattached shell with distinct costae, rather than the small form originally figured by Schlotheim (1820). If the type species of Cornulitella – C. conica ( Nicholson, 1872b) – is compared with Schlotheim’s illustration of Cornulites serpularius , the only clear morphological difference is the presence of a cellular structure on one side of the shell of C. conica . The degree of attachment of a cornulitid is at least partly dependent on the availability of suitable substrate ( Hall, 1888; also see below) and is an unreliable character upon which to found a genus.

The criteria originally used to define Conchicolites are also dubious, since Nicholson (1872a) erected the taxon to include cornulitids that were smaller than Cornulites and occurred in large clusters attached to a foreign body. Unlike Cornulitella , no cellular shell structure was observed and the tube wall was thin, but Nicholson (1872b) separated Conchicolites from Cornulitella essentially on ecological grounds, the latter being more completely attached to its substrate and never occurring in such large clusters. Nevertheless, subsequent authors (e.g. Prantl, 1950; Vinn & Mutvei, 2005) have argued that Conchicolites is generically distinct, emphasizing that its thinner, noncellular shell wall structure distinguishes it clearly from Cornulites . Indeed, Vinn & Mutvei (2005: 726) suggested that ‘the two taxa were probably unrelated and that cornulitids may be a polyphyletic taxon.’

The fourth taxon included in the Cornulitidae by Fisher (1962) – Kolihaia eremita Prantl, 1946 – was diagnosed as a tubular shell with ‘radical [proximal] expansions that may bifurcate’ ( Fisher, 1962: W138), indicating a taxon quite unlike Cornulites ; Kolihaia is now regarded as an epiplanktic anthozoan (Kříž, Fřýda & Galle, 2001).

In his brief account of Cornulitidae from the Silurian of Gotland, Larsson (1979a) identified four new genera, but did not describe, illustrate or propose names for them. Vinn & Mutvei (2005) reviewed the material, but did not erect formal taxonomic names, although Vinn (2004) named Cornulites gotlandicus from the Ludlow age Hemse Beds and later recognized the putative cornulitid genus Septalites , also of Ludlow age (Vinn, 2005). Although Cornulites is the only cornulitid genus recognized in the Much Wenlock Limestone Formation, other genera certainly exist, and the diversity of the group through the Palaeozoic requires further assessment.