Vesperaliidae

Valiukevičius, Juozas & Burrow, Carole J., 2005, Diversity of tissues in acanthodians with Nostolepis-type histological structure, Acta Palaeontologica Polonica 50 (3), pp. 635-649 : 643-644

Family Vesperaliidae nov.

Comment.—We erect the family Vesperaliidae nov. diagnosed principally by the scale histology of the second structural group (no other skeletal elements have been identified).

Type genus: Vesperalia Valiukevičius, 2004 .

Genera included: Type genus and Acanthacanthus Valiukevičius, 2003a .

Diagnosis.—Acanthodians differing from the other climatiiform families in having high and unusually thick−crowned scales bearing three or four symmetrical pairs of radial, or rarely subparallel, high and robust ridges extending the entire crown length; sharp anterior crown edge; high scale neck, which sometimes has a row of pores; stranggewebe with markedly long and dense oriented lacunae composing the entire crown; thin superficial layers of odontocytic mesodentine and without durodentine; wide ascending and radial vascular canals forming chambers in crowns at the junction with the circular canals.

Discussion.—Characters shared with some of the Climatiidae are the two long, posteriorly converging ridges edging the medial area of the scale crown, but the ridges differ in the Vesperaliidae by the height and robustness of the ridges on the posterior crown part. The high scale neck with a pore row is not found in the Acritolepidae or Tchunacanthidae , and is only rarely observed in the Climatiidae . The arrangement of vascular canals and the stranggewebe are unique characters amongst acanthodians.