Deiphonini Raymond, 1913

Tribe Deiphonini Raymond, 1913

Included genera: Deiphon, Barrande, 1850 ; Mainbrookia Adrain & Pérez-Peris, 2021 ; Onycopyge Woodward, 1880 ; Sphaerocoryphe Angelin, 1854 .

Diagnosis: One or two prefixigenal spines retained in holaspids; trunk with 13 segments; in late-diverging forms the last thoracic segment attached to the pygidium; pair of ventral projections on the pygidial rim.

Discussion: Deiphoninae encompasses a large range of morphological variability. Te Ordovician deiphonines Mainbrookina and Sphaerocoryphe and the post-Ordovician taxa Deiphon and Onycopyge are morphologically highly distinct from the early diverging taxa within the subfamily. Consequently, the synapomorphies that define Deiphoninae have been transformed in the more derived forms. In order to characterise the deiphonine group that contains the post-Ordovician taxa and its most direct Ordovician relatives, the tribe Deiphonini is proposed. Both features are synapomorphies of the Mainbrookia + Sphaerocoryphe clade and they are found in younger deiphonines. In addition, the retention of the last thoracic segment in the holaspid pygidium is an apomorphy of Sphaerocoryphe also shared with post-Ordovician forms. Tese features experienced modifications in the shape in the post-Ordovician forms, as for example the prefixigenal spines are placed in a more ventral position, the anterior pygidial segment is no longer morphologically similar to a posterior thoracic segment and the posterior ventral projections are located in a more posterior and dorsal position than in Mainbrookia and Sphaerocoryphe . But here there can be no doubt that the structures present in post-Ordovician deiphonines are homologous with the structures present in Mainbrookia and Sphaerecoryphe . All these shared characters, together with the strong similarities in the protaspid morphology between Sphaerocoryphe and Deiphon ( Chatterton, 1980; Chatterton & Perry, 1984), support the relationship of Mainbrookia and Sphaerecoryphe with the post-Ordovician forms and the inclusion of all of them in a formally named group.