Nostolepis Pander, 1856

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

Genus Nostolepis Pander, 1856

Comment.—We propose that the genus Nostolepis applies only to the representatives previously assigned to this genus which have flank scales that grew by superposition and that belong to the first histological type showing both stranggewebe and odontocytic mesodentine in scale crowns.

Type species: Nostolepis striata Pander, 1856 ; Ohesaare Cliff, Saaremaa; Ohesaare Regional Stage, Pridoli , Upper Silurian .

Species included: N. gracilis Gross, 1947 , N. costata Goujet, 1976 , N. arctica Vieth, 1980 , N. kernavensis Valiukevičius, 1985 , N. alta Märss, 1986 , N. minima Valiukevičius, 1994 , N. taimyrica Valiukevičius, 1994 , N. linleyensis Miller and Märss, 1999 , N. decora Valiukevičius, 2003a , N. parathleta Valiukevičius, 2003b , N. kozhymica Valiukevičius, 2003b , N. terraborea Valiukevičius, 2003b , N. amplifica Valiukevičius, 2003c , N. magnicostata Valiukevičius, 2003c , N. consueta Valiukevičius, 2003c , and N. musca Valiukevičius, 2003c .

Revised diagnosis.—Climatiid acanthodian with flank scales of varying size (usually> 0.5 mm) having crowns ornamented by subparallel ridges (usually <8) of variable length; ridges are mainly stout, fading out and rarely reaching posterior crown edges; ridges are rarely bifurcated, and are rarely curved along the lateral edges; some species have raised medial area and lower lateral ledges. Flank scales grew by superposition of layers, with the crown formed of stranggewebe (posterior part) in the lamellae surrounding the primordium, and odontocytic mesodentine incorporating many osteocytes in the anterior crown part; the stranggewebe layer may be enveloped by the mesodentinal network in a growth zone; system of ascending, circular and radial vascular canals developed; bone in scale base highly cellular. The tuberculated head tesserae and tectal plates with “starlet” sculpture grew areally or both areally and superpositionally, and also have a histological structure with stranggewebe and odontocytic mesodentine. Fin spines are short with nodose ribs; they lack an insertion base and subcostal canal, and are composed of odontocytic mesodentine in the ribs and thin outermost layer; the middle layer of cellular bone and osteodentine forms the greatest thickness of the spine; a large central cavity is surrounded by a layer of finely lamellar bone.