The true “Festive Volute”, as it was recently revealed, is a striking volutid endemic to Oman characterised by a ‘festive’ colouration consisting of chocolate axial lines and irregularly distributed reddish patches. Until recently, the name was considered to comprise of a few geographically segregated forms ranging between Oman and Somalia — with the best known one being the large, knobby form from Somalia (typical shell length around 200 mm, largest specimens can exceed 250 mm) showing strong red colouration on the spire. In the last few years, collectors in Oman rediscovered and once again brought to light the much overlooked smaller, narrower Arabian form (typical shell length around 80 mm, very large specimens may reach 135 mm) which also lacks the red-stained early whorls seen in the Somalian form.

The collection of over 200 specimens in Oman led to a study published in 2020 pointing out that the Arabian form should be considered distinct from the Somalian form due to clear conchological differences, and that the holotype of Callipara festiva (housed in Muséum national d’Histoire naturelle, Paris) is in fact a specimen of the Arabian form, making the smaller Oman population the true Callipara festiva. Indeed, the holotype of C. festiva is only 71 mm in shell length (though sub-adult) and lacks a reddish spire; the collection locality was not known and Lamarck hypothesised that it probably came from South America, which is clearly incorrect. This means the Somalian form actually did not have a name, and it was described as a new species, Callipara casaana Childs, Aiken & Bail, 2020 — this is the taxon figured and discussed in S. Peter Dance’s 50 “Rare Shells” (1969) as Festilyria festiva. The same authors also named two nomenclaturally unavailable form names for the true C. festiva: f. lizzae for specimens with darker background colouration and the black-red markings (accounting for about 2% of the known specimens) and f. dobsonae for very rare specimens with even darker, brownish background colour.

There is an intermediate form between C. festiva and C. casaana, known as Callipara festiva f. deceptrix Palazzi, 1981, found around Yemen between Oman and Somalia. The shell of f. deceptrix is typically around 175 mm in length (very large specimens exceeding 220 mm) and is narrow like typical C. festiva but has the reddish spire that characterises C. casaana. The exact affinity of this form is yet unclear, and requires further investigation. The type specimen of f. deceptrix, however, is a 116 mm subadult with a spire showing very strong reddish colouration suggesting a closer affinity to C. casaana.

The true C. festiva appears to be only uncommon in Oman with numerous specimens beached after storms, but live-taken specimens remain exceedingly rare. Almost certainly a carnivorous and predatory gastropod feeding on other invertebrates, judging from the number of beached shells it probably lives in shallow subtidal waters (unlike C. casaana which is only taken by trawl and supposedly live in deeper waters). The only species that C. festiva can be confused with, other than C. casaana, is the very rare Callipara victoriae Childs, Aiken & Bail, 2020 endemic to Masirah Island, Oman, but they are actually easy to distinguish based on the indistinct shoulder knobs and the much wider shell of C. victoriae. – Adapted from Chong Chen’s post Kogkhulion