Early evolution of D eclinognathodus close to the M id‐ C arboniferous B oundary interval in the B arcaliente type section ( S pain)

Upper S erpukhovian to lower B ashkirian conodonts studied from the lower and middle part of the B arcaliente F ormation type section ( NW Spain) are not abundant, but the sedimentary record seems unusually well represented. The first occurrence of D eclinognathodus bernesgae occurs more than 140 m below the first occurrence of D .  inaequalis , the taxon of the D . noduliferus species group appearing in the bed of the Global Standard Stratotype‐section and Point ( GSSP ) for the Mid‐Carboniferous Boundary ( A rrow C anyon, N evada). P1 elements transitional between D . bernesgae and D .  inaequalis are described and considered relevant to the global correlation of the M id‐ C arboniferous B oundary. In addition, D . praenoduliferus , D .  cf. noduliferus , D . lateralis , I diognathoides asiaticus , I . corrugatus and N eognathodus sp. are described and illustrated from the B arcaliente F ormation. A phylogeny is proposed for the early species of these genera on the basis of the morphological changes of the P 1 element, where the rostral parapet and area, the surface roughness and the length and depth of the adcarinal troughs are diagnostic characters at the specific level, while caudal ornamentation is a secondary taxonomic character.