Urdyella, Leu & Bucher & Vennemann & Bagherpour & Ji & Brosse & Goudemand, 2022

Leu, Marc, Bucher, Hugo, Vennemann, Torsten, Bagherpour, Borhan, Ji, Cheng, Brosse, Morgane & Goudemand, Nicolas, 2022, A Unitary Association-based conodont biozonation of the Smithian-Spathian boundary (Early Triassic) and associated biotic crisis from South China, Swiss Journal of Palaeontology (19) 141 (1), pp. 1-61 : 50

Genus URDYELLA gen. nov.

Type species. Urdyella unicorna n. sp.

Type stratum and locality. Luolou Formation , Laren road cut, Guangxi Province, China .

Etymology: Named after Severine Urdy.

Diagnosis. Short coniform-to-segminiscaphate P 1 element with a long cusp, usually at least twice the length of the adjacent denticle, a very short anterior process, and a broadly excavated basal cavity.

Remarks. Te relationship of this genus to Cornudina is uncertain ( Orchard, 2005, 2007). P 1 elements similar to the P 1 element of Urdyella n. gen. are often considered as belonging to Cornudina . Yet, as explained by Orchard (2005), the holotype of Cornudina ( O. breviramulus ) appears to be a P 2 element. Both Kozur and Mostler (1971, p. 11) and Sweet (in Clark et al., 1981, p. W155) placed Cornudina with Chirodella as a multi-element Chirodella . Te holotype of Chirodella (Metalonchodina triquetra) is an S 2 element. Te holotypes of both Cornudina and Chirodella are from Muschelkalk (Middle Triassic) collections made by Tatge (1956), who described no elements like those described by Orchard (2005) as P 1. ‘ Chirodella’ sensu formo does not occur in Orchard’s nor in Koike’s Spathian collections of Cornudina . For this reason, Koike (1996) and Orchard (2005) regarded the two genera as unrelated: Koike reconstructed Cornudina as an apparatus consisting of P 1 and P 2 elements only ( Cornudina breviramulis ) or of P 1 elements only ( Cornudina igoi ), whereas Orchard reconstructed Cornudina ? as having an octomembrate apparatus whose P 2 element vaguely resembles the holotype of Cornudina , but he questioned the very validity of that name for Spathian forms that might be unrelated to the ‘true’ Middle Triassic Cornudina .

‘ Chirodella’ sensu formo does not occur in our Smithian collections of Urdyella n. gen. and neither does ‘ Cornudina’ sensu formo. Hence we suggest that Cornudina -likeP 1 elements found in the Smithian, and possibly those found in the Spathian, belong to Urdyella n. gen. not to Cornudina .

Based on multi-element considerations, Orchard grouped both ‘ Cornudina’ and Spathicuspus within the same subfamily Cornudininae . Because Spathicuspus seemed to occur first, he hypothesized that ‘ Cornudina’ evolved from Spathicuspus near the Lower/ Middle Triassic boundary through overall shortening of the P 1 element. Since Urdyella occurs already in the Smithian, we suggest that Spathicuspus may have evolved from Urdyella and the Spathian forms of ‘ Cornudina’ either belong to Urdyella , derived directly from Urdyella , or as assumed by Orchard, evolved from Spathicuspus , although the latter hypothesis seems less likely. Urdyella itself may have evolved from Discretella via forms like Discretella ? n. sp. B. Discretella has a much shorter cusp and a larger anterior process. Furthermore, the basal cavity in Urdyella is flatter and not as broadly excavated as in Cornudina .