Research paper

Rare Middle and Upper Devonian dalmanelloid (Orthida) of the Cantabrian Mountains, N Spain

Departamento de Geología, Universidad de Oviedo, c/ Jesús Arias de Velasco s/n, 33005 Oviedo, Spain.
Corresponding author


Rare Cantabrian Dalmanellidae (Costisorthis lisae nov. sp.), Dicoelosiidae (Teichertina cf. peregrina, T. cf. fitzroyensis), and Mystrophoridae (Mystrophora sp., Biernatium sucoi nov. sp., and Biernatium sp. 2) are described and figured for the first time in Spain. Most of them are scarce forms that occur only in certain localities. All the species but one came from the lower part of the Portilla (province of León) and Candás (province of Asturias) formations, Faunal Interval 21, Polygnathus rhenanus/P. varcus conodont zone, middle Givetian. The exception is Biernatium sp. 2 that occurs in Asturias in FI 25, Piñeres Fm., Palmatolepis transitans zone, lower Frasnian. Costisorthis ranges from Pragian to Eifelian rocks in central Europe. C. lisae nov. sp., from the Givetian of Asturias differs from other Costisorthis species in the weaker development of the distinctive ventral and dorsal plications. Teichertina is a bizarre, bisulcate spiriferoid-like taxon previously known from the Pragian to Frasnian of central Europe, NE Russia, west-central Alaska, Nevada, China and Western Australia. T. cf. fitzroyensis, from the Givetian of Asturias and Leon, is smaller than T. fitzroyensis. Its ventral sulcus and costellate ornamentation are weaker than the nominal species. T. cf. peregrina from the Givetian of Leon, is very close to the nominal species. Biernatium includes Pragian to Frasnian age species from central Europe (Poland, Moravia), and Western Australia. Kayserella costatula from the Pragian-Zlichovian of the Yukon (northwestern Canada) is also placed in the genus due to its long cruralium. The Cantabrian Biernatium species have the characteristic high dorsal septum and large cruralium of the genus, but B. sp. 2 is smaller and with a more branched radial ornament pattern than B. sucoi nov. sp. The good preservation of B. sucoi nov. sp. collections allows for the study of its ontogeny and phylogenetic relationships. B. sp. 2 very probably evolved from B. sucoi nov. sp. by extension of the rib branching along the entire shell or nearly so. Mystrophora is close to Biernatium but it is provided with fulcral plates that are lacking in Biernatium, and by a shorter and more elaborate cruralium. The taxon was previously known in beds of Pragian to Eifelian age in northwestern Canada, Eastern Australia, Burma, Europe (Germany, Belgium, and France), and, questionably in the Mongol-Okhotsk area of the Siberian block. M. sp. from the middle Givetian of León is characterized by a larger sized shell than is usual for the genus.

Key words: Dalmanelloids, systematics, ontogeny, phylogeny, palaeobiogeography.

How to cite: García-Alcalde, J.L. 2018. Rare Middle and Upper Devonian dalmanelloid (Orthida) of the Cantabrian Mountains, N Spain. Spanish Journal of Palaeontology, 33 (1), 57-82.

Received 03 October 2017, Accepted 06 March 2018, Published 30 June 2018