Sphenodus lundgreni ( Davis, 1890 )

Adolfssen, Jan S. & Ward, David J., 2015, Neoselachians from the Danian (early Paleocene) of Denmark, Acta Palaeontologica Polonica 60 (2), pp. 313-338 : 316

Sphenodus lundgreni ( Davis, 1890)

Fig. 2D–G.

1890 Oxyrhina lundgreni sp. nov.; Davis 1890: 393, pl. 38: 9.

1957 Eychlaodus lundgreni ( Davis 1890) ; Glickman 1957: pl. 1: 16. 1979 Orthacodus lundgreni ( Davis 1890) ; Floris 1979: fig. 7.

1993 Sphenodus lundgreni ( Davis 1890) ; Siverson 1993a: 28.

Material.— Four almost complete specimens (including the holotype), a further nine cusps in the collections of SNM MGUH1406 holotype, MGUH 29822 , MGUH 29823 , MGUH 29824 , GM1881-3326, GM1885-881, GMV2012- 57 [batch number]), and dozens of specimens, many without roots, in private collections, all collected from the Br2 at Faxe .

Description.—Large monocuspid teeth (up to 60 mm high cusps). The cusp is tall, slender with strong deep folds covering the lower part of the labial face and with very short folds at the base of the lingual face, but folds may be lacking in some specimens. Both the faces are strongly convex. Anterior teeth are erect whereas lateral and posterior teeth are slanted towards the commissure, sometimes only in the upper part of the cusp. The majority of teeth display a strong sigmoidal curvature in lateral view, regardless of whether the anterior or posterior margin carries a strong cutting edge. The root is lacking in most teeth but most of the few preserved roots are low and wide with a concave base. Anterior teeth have much narrower roots ( Fig. 2E).

Remarks.—By analogy with the Recent sand shark, Carcharias taurus Rafinesque, 1810 , upper teeth are more likely to be sigmoid ( Fig. 2D) and lower teeth more posteriorly recurved ( Fig. 2E; Böttcher and Duffin 2000).

The teeth depicted by Mannering and Hiller (2008) from the Danian of New Zealand have much longer lingual folds and much more lingually protruding roots, characters which have not been observed in any of the Danish material. It is very likely that the material from New Zealand represents another species. None of the Danish specimens have lateral cusplets and the specimen depicted from New Zealand may be pathologic ( Mannering and Hiller 2008: pl. 1: 6–9). Though Sphenodus may have been more common during the Jurassic, it has been found in the Maastrichtian of Antarctica ( Richter and Ward 1990; Kriwet et al. 2006), but the material from Antarctica differs in that both the labial and lingual folds are very short compared to S. lundgreni , and is too poorly known to draw further conclusions on relationships.

The specimens depicted by Antunes and Cappetta (2002) from Angola appear to carry very similar folds as those in S. lundgreni , even though the Angolan material presumably is from the Campanian. The specimens depicted by Waldman (1971) from the early Paleogene of British Columbia, Canada are of too poor a quality for further comment.

Stratigraphic and geographic range.— S. lundgreni is known from the late Maastrichtian of Denmark to the middle Danian of Denmark and Sweden ( Davis 1890). Teeth of Sphenodus sp. also occur in the Beltinge Fish Bed, basal Upnor Formation, Thanetian, in the UK and in the Thanetian at Shatrylisay, western Kazakhstan ( DJW personal observation).