Synechodus sp.

Mollen, Frederik H. & Hovestadt, Dirk C., 2018, A new partial skeleton of a palaeospinacid shark (Neoselachii, Synechodontiformes) from the Albian of northern France, with a review of the taxonomic history of Early Cretaceous species of Synechodus Woodward, 1888, Geodiversitas 40 (25), pp. 557-574 : 560

Synechodus sp.

( Figs 3-7 )

DESCRIPTION

General outline

Skeletal remains of about 340 mm in overall length are preserved in two associated blocks of Gault Clay ( Fig. 3 ), the smallest one of which comprises a series of (precaudal) vertebrae only, whereas the larger block contains the major part of the skeleton. The latter reveals several skeletal elements (i.e., parts of the neurocranium, splanchnocranium, pectoral girdle, vertebral column, teeth and dermal denticles), most of which are displaced as a result of partial decomposition prior to final burial. Dorsal fin spines have not been found. The ventral side of the specimen is exposed, slightly tilted to the right and certain skeletal elements twisted with the pectoral girdle overlying the vertebral column. Consequently, the right side of the individual can be observed on the left side of the blocks and vice versa.

Figures

FIG. 3. — A, Partial skeleton of Synechodus sp. (IRScNB P.9895), Saint-Pô Formation (Albian, Lower Cretaceous), Boulonnais beach between Escalles and Strouanne (northern France);B, Same specimen with interpretation of the exoskeleton (hatching) and the endoskeleton, including parts of the neurocranium (red), splanchnocranium (orange), pelvic girdle (beige) and vertebrate column (yellow). Scale bar: 100 mm.

FIG. 4. — Selected details (in situ) of a partial skeleton of Synechodus sp. (IRScNB P.9895), Saint-Pô Formation (Albian, Lower Cretaceous), Boulonnais beach between Escalles and Strouanne (northern France): A, cluster of anterior teeth; B, cluster of lateral teeth; C, D, patches of dermal denticles; E, precaudal monospondylous vertebrate. Scale bars: A, 250 mm; B, 300 mm; C-E, 150 mm.

FIG. 5. — Associated set of isolated dermal denticles of Synechodus sp. (IRScNB P.9895), Saint-Pô Formation (Albian, Lower Cretaceous),Boulonnais beach between Escalles and Strouanne (northern France): from presumed trunk (A-D), fin (E-G) and snout (H) areas,or preserved as cluster (I, J). Scale bars:A-H, 0.5 mm; I, J, 1 mm.

FIG. 6. — Associated set of isolated teeth of Synechodus sp.(IRScNB P.9895),Saint-Pô Formation (Albian,Lower Cretaceous),Boulonnais beach between Escalles and Strouanne (northern France): A, anterior; B, antero-lateral; C, D, lateral; E, F, latero-posterior and G, posterior tooth files, in labial (1), lingual (2), occlusal (3) and basal (4) views. Scale bars: A-E, 5 mm; F, 4 mm; G, 2 mm.

FIG. 7. — Micro CT scan of an isolated tooth of Synechodus sp. (IRScNB P.9895), Saint-Pô Formation (Albian, Lower Cretaceous), Boulonnais beach between Escalles and Strouanne (northern France): A, lingual; B, labial; C, basal; D, lateral and E, occlusal views; 3D volume renderings with sagittal (A1-A5), transverse (C1-C2) and frontal (D1-D3) sections showing tooth vascularisation and histology as follows: EN, enameloid; PC, pulp cavity; ORD, orthodentine; OSD, osteodentine; SC, secondary cavities; VC, vascular canaliculi. Scale bar: 1 mm.