Siphonodella leiosa (Conodonta), a new unornamented species from the Tournaisian (lower Carboniferous) of Puech de la Suque (Montagne Noire, France)

Abstract

A new conodont species, Siphonodella leiosi, is described from the lower Carboniferous pelagic limestones of the Montagne Noire (France), deposited on North Gondwana in outer platform environment. Specimens were obtained from one level dated to the Siphonodella jii conodont Zone. The major difference from other siphonodellid conodonts known in this area is that the elements of this new species have a practically entirely smooth and unornamented platform, apart from the development of one or two low rostral ridge-like nodes. Similar morphologies were generally observed in shallow marine deposits of the same time frame from China, Russia and East and Central European areas. The new discovery reinforces the idea that ornamentation of siphonodellids is not only related to bathymetry, but that temperature could play an important role in the diversification and radiation of unornamented species during the Siphonodella jii conodont Zone.

NEW GROUP OF TOURNAISIAN ADVANCED <em>SIPHONODELLA</em> (CONODONTS, LOWER CARBONIFEROUS)

“…This ornamentation of this species resembles more closely that of the group of cosmopolitans, since the forms, especially, at the late stages of ontogeny bear thin ornamentation in the form of nodes and short transverse ridges (Fig. 2, D-H; Souquet et al 2020). For example, Siphonodella lanei Zhuravlev & Plotitsyn (= S. crenulata (Cooper) M2) or some S. obsoleta Hass have a similar thin reduced ornamentation.…”

“…However, this species has not been found in the type localities (Donetz, Moscow, and Pechora basins) of representatives of this group. Siphonodella leiosa Souquet, Corradini & Girard is insufficiently studied, since it has only been described at a single location at Puech de la Suque section, Montagne Noire, France (Souquet et al 2020). This ornamentation of this species resembles more closely that of the group of cosmopolitans, since the forms, especially, at the late stages of ontogeny bear thin ornamentation in the form of nodes and short transverse ridges (Fig.…”

“…The great research interest in this group of conodonts has led to a significant expansion of the taxonomic composition of siphonodellids. A number of new species of advanced (possessing rostrum) siphonodellids have been described only in last decade (Kaiser et al 2017;Zhuravlev 2017a;Zhuravlev & Plotitsyn 2017;Zhuravlev 2019;Souquet et al 2020) and taxonomical revisions carried out in the last decade (Zhuravlev & Plotitsyn 2017;Zhuravlev et al 2021). At the same time, the emergence of specific specimens has been noted, which…”