Paraorthacodus jurensis, (SCHWEIZER, 1964)

Klug, Stefanie, Kriwet, Jürgen, Böttcher, Ronald, Schweigert, Günter & Dietl, Gerd, 2009, Skeletal anatomy of the extinct shark Paraorthacodus jurensis (Chondrichthyes; Palaeospinacidae), with comments on synechodontiform and palaeospinacid monophyly, Zoological Journal of the Linnean Society 157 (1), pp. 107-134 : 110-111

PARAORTHACODUS JURENSIS ( SCHWEIZER, 1964)

Synechodus jurensis ; Schweizer, 1964: 63, pl. 7 figs 1– 9, pl. 8 figs 5–6.

Synechodus jurensis ; Reif, 1973a: 9, fig. 7e–k.

Synechodus jurensis ; Reif & Goto, 1979: fig. 2e.

Synechodus jurensis ; Maisey, 1985: 15.

Synechodus jurensis ; Reif, 1985: text-fig. C(e).

Paraorthacodus jurensis ; Duffin, 1993a: text-figs 2–4, pls 1–3.

Paraorthacodus cf. jurensis ; Dietl et al., 2006: pl. 5.

Paraorthacodus jurensis ; Dietl et al., 2007: pl. 5.

Holotype: Specimen described by Schweizer (1964) from the upper Kimmeridgian (Upper Jurassic) of the Nusplingen Lithographic Limestone of south-western Germany, bed G (see also Aldinger, 1930; Duffin, 1993a; Dietl et al., 1998). The specimen is housed in the GPIT under collection number GPIT 1210/1.

Revised diagnosis: A species of Paraorthacodus characterized by the combination of the following skeletal and dental characters (upper and lower teeth are not distinguishable in preserved specimens): pelvic girdle inserts at 42nd to 43rd vertebra; transition from monospondylous abdominal to diplospondylous precaudal vertebral column between centra 48 and 49; diplospondylous caudal fin skeleton starts at 80th centrum. Sexual dimorphism in tooth morphology present by a different number of lateral cusplets in all tooth positions: number of cusplets of gender 1 (holotype) without brackets, of gender 2 (new specimen) with brackets; main cusp with high coronal profile in anterior and lateral teeth, with low coronal profile in posterior teeth; ornamentation of delicate nonbifurcating vertical ridges originating above crown/root junction in labial view, and above the prominent lingual neck lacking any ornamentation in lingual view. Single left and right small parasymphysial teeth with straight and slender main cusp flanked by two pairs of triangular cusplets diverging from main cusp, and U-shaped root in labial view. Anterior teeth with main cusp flanked by two(three) pairs of lateral cusplets; main cusp without distal inclination; parallel cutting-edges in the upper two-thirds of main cusp, lowest third expanding to the doubled width; cusplets inclined towards main cusp and staggered downwards laterally; ornamentation on lowest third of main cusp and lowest half of cusplets in labial view; in lingual view ornamentation on the lower half of the main cusp and lower two-thirds of cusplets; root lobes slightly curved anteriorly in basal view; in labial view root lobes curved downwards. Lateral teeth with main cusp flanked by three(four) pairs of lateral cusplets; distally inclined main cusp in anterior-most teeth; mesial cusplets slightly distally inclined; distal cusplets straight and only most lateral inclined mesially; crown base of anterolateral teeth slightly curved downwards, of posterolateral teeth horizontal in labial view; parallel cutting-edges in the upper twothirds of main cusp, lowest third expanding to the doubled width; expansion of ornamentation in labial and lingual view same as in anterior teeth; root lower than in anterior teeth; root lobes slightly curved downwards in anterolateral teeth in labial view; horizontal root base in other lateral positions; in basal view root lobes faintly curved labially with very deep and rectangular expansion. Posterior teeth with main cusp flanked by two(three) pairs of lateral cusplets, reduced to one(two) pairs to the commissure; main cusp slightly distally inclined; teeth decrease in width and height posteriorly; lateral cusplets almost reach same height as main cusp towards the commissure; ornamentation increases in height on labial face towards the commissure reaching apex in posteriormost teeth; lingual face ornamented throughout the crown; root with horizontally noncurved basis.

Comments: Maisey et al. (2004) assigned an incomplete skeleton of a Late Jurassic shark from the Solnhofen area, which is housed in the Senckenberg Museum Frankfurt ( FSM P.4392) tentatively to Paraorthacodus . Unfortunately, this specimen, despite displaying a lot of morphological information, has no unpaired fins preserved. Based on dental structures, however, this specimen should be assigned to Synechodus (S. Klug, unpubl. data). Consequently, the two specimens of Par. jurensis and two small specimens of Paraorthacodus sp. (which might be juveniles to Par. jurensis ) from the Solnhofen quarries (compare Kriwet & Klug, 2004: fig. 7; Klug & Kriwet, 2008: fig. 3a) are the only known skeletal remains of this genus that allow the identification of additional skeletal diagnostic characters in addition to dental features for comparison with and differentiation from other species of Paraorthacodus .

Referred specimen: A single specimen from the upper Kimmeridgian (Upper Jurassic) of the lithographic limestones of Nusplingen (south-western Germany), bed L. The specimen is housed in the SMNS under collection number SMNS 88987/1.