Megalolamna serotinus ( Probst, 1879 ) Pollerspöck & Shimada, 2024

Pollerspöck, Jürgen & Shimada, Kenshu, 2024, The first recognition of the enigmatic fossil shark genus Megalolamna (Lamniformes, Otodontidae) from the lower Miocene of Europe and M. serotinus (Probst, 1879) as the newly designated type species for the genus, Zitteliana 98, pp. 1-9 : 1-9

Megalolamna serotinus ( Probst, 1879) comb. nov.

Figs 2 , 3

Lamna bassanii – Alessandri 1897: 38–39, pl. 1, figs 16–16 a.

Otodus sp. – Hasegawa and Uyeno 1967: 116, pl. 21, fig. 1 a – c.

Odontaspis taurus obliqua – Caretto 1972: 29, pl. 4, figs 1 a – c, 2 a – c.

Lamna sp. – Barthelt et al. 1991: 200, pl. 2, fig. 8.

Lamna sp. – Renz 2009: 158.

Lamnidae gen. et sp. indet. – Tanaka 2013: 99, pl. 12, fig. 11 a – c.

Brachycarcharias sp.? – Chandler and Young 2015: 49.

Lamniformes gen. et sp. indet. – Carrillo-Briceño et al. 2016: 86, fig. 4.16–17.

Megalolamna paradoxodon – Shimada et al. 2017: 706, fig. 2.

Megalolamna paradoxodon – Landini et al. 2019: 257, fig. 3 S – U.

Megalolamna paradoxodon – Carrillo-Briceño et al. 2020: 13, fig. 5 U – X.

Megalolamna paradoxodon – Shimada et al. in press: 8, fig. 2 a – h.

Megalolamna paradoxodon – Pollerspöck and Unger in press.

Material.

One isolated tooth (GPIT-PV- 31738, as Otodus serotinus sp. nov. in Probst (1879): pl. 2, fig. 84) from the Baltringen-Formation (Baltringen Horizon) in Kodelsberg (east of Baltringen), Baden-Württemberg, Germany, housed in Collection of the Institute and Museum of Geology and Palaeontology of the University of Tübingen, Germany (Fig. 2 A – C ); one isolated tooth (SNSB-BSPG 1984 X 21, as Lamna sp. in Barthelt et al. (1991), pl. 2, fig. 8) from the Kalkofen Formation in Walbertsweiler, Baden-Württemberg, Germany, housed in Bavarian State Collection for Palaeontology and Geology, Munich, Germany (Fig. 3 A ); one isolated tooth (2022 / 46) from the Plesching Formation in Plesching, Austria, housed in Oberösterreichische Landes-Kultur GmbH, Geosciences collections, Leonding, Austria (Fig. 3 B – E ); two isolated teeth (Illustration originals, uncat.: Caretto (1972) pl. 4, figs 1 a – c, 2 a – c) from the lower part of the “ Pietra da canton ” formation, Monferrato region, Italy (lower Miocene) housed in the collections of the Museo Civico di Storia Naturale di Milano, Italy (Fig. 3 F – K ); three isolated teeth (syntype: Alessandri (1897) pl. 1, fig. 16 b: MGPT-PU 11196; additional two specimens: MGPT uncat.) from the Pietra da Cantoni Rosignano (La Colma) housed in the collections of the Earth Sciences Department of the University of Turin, Italy (Fig. 3 L – Q ); one isolated tooth ( UM MAZ 38) from the Burdigalian sediments of the Gypsum quarry “ la Plâtrière’ ’ of the company Syniat, ( France) housed in Institut des Sciences de l’Evolution de Montpellier, Montpellier, France (Fig. 3 R – U ).

Description.

GPIT-PV- 31738 (Fig. 2 (A) – (C )) is an almost complete tooth, missing only a small portion of the mesial root lobe. It measures approximately 8.2 mm in total tooth height and 8.2 mm in total tooth width. The thickness at the crown base is about 2.3 mm, the distal lateral cusplet is slightly narrower at the base than the mesial one (1.2 mm vs. 1.4 mm). Its crown consists of a distally inclined main cusp with a pair of low lateral cusplets, the total crown height and width being about 5.8 mm and 8.1 mm, respectively. A small piece of the crown apex is broken off. The mesial and distal cutting edges of the main cusp are sigmoidally curved, very sharp, straight or slightly convex mesially and strongly concave distally, and their basal side continues to become the cutting edges of the lateral cusplets with practically no clear demarcation. The lingual crown base is essentially concave and slightly wavy. A thin and well-defined enameloid coating is missing due to the poor preservation of the root. However, a clear ridge is recognisable, particularly under the base of the mesial lateral cusplet, which indicates the original presence of this enameloid coating on the tooth neck. The labial base of the crown is almost straight, with some of the enameloid missing due to the state of preservation. Despite the damage to the mesial side of the root, it is recognisable that the root lobes are asymmetrical and the mesial root lobe is slightly wider than the distal root lobe. The lingual root surface is gently rounded. Large foramina or a lingual basal furrow are absent. Due to the small size and the strongly distally inclined crown, the tooth likely represents a latero-posterior tooth from a small individual.

A detailed description of the other records shown in Fig. 3 (( A) – (Q )) is not given here, as some of the material has already been published and illustrated or corresponds to the previous species diagnosis.

Figures

Figure 2. Tooth of Megalolamna serotinus comb. nov. (GPIT-PV- 31738) from the Upper Marine Molasse Baltringen, Walbertsweiler, Baden-Württemberg, Germany, that was originally described as Otodus serotinus by Probst (1879, pl. 2, fig. 84). (A) lingual, (B) profile, and (C) labial views. Scale bar: 5 mm.

Figure 3. Additional teeth of Megalolamna serotinus comb. nov. from Miocene deposits of Europe described in this paper. A: SNSB-BSPG 1984 X 21 from the Upper Marine Molasse Baltringen, Walbertsweiler, Baden-Württemberg, Germany, in lingual view; B – E: Oberösterreichische Landes-Kultur GmbH Coll. no. 2022 / 46 from the Upper Marine Molasse, Plesching, Austria, in (B) lingual, (C) labial, (D) profile, and (E) basal views; F – K: Museo Civico di Storia Naturale di Milano Coll. no. V 5858 and 5856 from the lower part of the “ Pietra da canton ” formation, Monferrato region, Italy, in (F, I) lingual, (G, J) profile, and (H, K) labial views; L – Q: Three teeth from Pietra da Cantoni, eastern Monferrato, Italy, the collection of the Earth Sciences Department of the University of Turin: MGPT uncat. in (L) lingual and (M) labial views; MGPT-PU 11196 in (N) lingual and (O) labial views; and MGPT uncat. in (P) lingual and (Q) labial views; R – U: UM MAZ 38 from Mazan, Mormoiron Basin, Vaucluse, France, in (R) lingual, (S) profile, (T) labial, and (U) basal views. Scale bar: 10 mm.