Isurolamna affinis (Casier, 1946)
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publication ID |
https://doi.org/ 10.26879/1283 |
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persistent identifier |
https://treatment.plazi.org/id/A1525343-662A-FF9C-FEB2-B33BFCB3FE26 |
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treatment provided by |
Felipe |
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scientific name |
Isurolamna affinis (Casier, 1946) |
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Isurolamna affinis (Casier, 1946)
Figure 5M–S View FIGURE 5
1861 Oxyrhina biflena n. sp.; Rogovich, p. 55, pl. VIII, figs. 4, 5.
1912 Oxyrhina biflexa Rog. ; Savtchenko, p. 180, pl. XIII, figs. 28, 33, 39.
1928 Oxyrhina biflexa Rog. ; Menner, p. 306.
1946 Odontaspis hopei var. affinis ; Casier, p. 65, pl. 2, fig. 11b-c.
1950 Lamna affinis (Casier) ; Casier, p. 17.
1966 Lamna affinis (Casier) ; Casier, p. 80, pl. 5, figs. 7-14.
1976 Isurolamna affinis (Casier, 1946) ; Cappetta, p. 555-556, pl. 2, figs. 1-8.
2012 Isurolamna affinis (Casier, 1946) ; Cappetta, p. 217, fig. 203A-G.
2012 Isurolamna affinis (Casier, 1946) ; Diedrich,
p. 19, fig. 14.10.
2014 Isurolamna affinis (Casier, 1946) ; Carlsen and Cuny, p. 46, fig. 4A-G.
2021 Isurolamna affinis (Casier, 1946) ; Adnet et al., p. 31-33, fig. 4.5-4.6.
Material. Three anterior teeth, NMNHU-G 391/94, 391/99, 391/100; one anterolateral tooth, NMNHUG 391/97; three lateral teeth, NMNHU-G 391/95, 391/140/1-2, Vyshhorod.
Description. The anterior teeth ( Figure 5O–Q View FIGURE 5 ) measure from 16 to 17 mm apicobasally. The crown is slender and moderately inclined lingually. The lingual face is strongly convex, and the labial face is almost flat with a median depression near the crown-root junction. The enameloid is smooth on both faces, and the cutting edges reach the base of the crown. There is only a main cusp without cusplets, and both mesial and distal sides of the crown are smooth. The root with an arcuate basal edge shows two rounded lobes, which are broken and therefore it is not possible to measure the angle between them. There is a round foramen on the lingual protuberance.
The anterolateral tooth ( Figure 5M–N View FIGURE 5 ) is similar in morphology and size to the anterior ones (measuring 16.5 mm apicobasally and 11.1 mm mesiodistally), although it has a wider main cusp. The root consists of two lobes differing in size and the degree of roundness.
The lateral teeth ( Figure 5R–S View FIGURE 5 ) measure from 10.5 to 18.4 mm apicobasally and from 10.8 to 16.0 mm mesiodistally. The crown is triangular, inclined distally, and flattened labiolingually. There are two doubled triangular cusplets that are well separated from the main cusp in lingual view, although they are absent in one specimen (as in the case of anterior and anterolateral teeth). One of the root lobes is shorter and rectangular, whereas the other one is longer and has a rounded edge. The basal root edge is arcuate, and the angle between the root lobes equals 100°.
Remarks. The genus Isurolamna has characteristic heterodonty: anterior and anterolateral teeth of its representatives are of isuroid morphology, whereas the lateral teeth are morphologically similar to those in certain lamnids (Cappetta, 1976). Of the three species known so far from the Eocene of Europe and Asia (Adnet et al., 2021), the specimens described in this study are the most similar to those of I. affinis (Casier, 1946) . These teeth differ from I. inflata Leriche, 1905 in lacking lateral cusplets, and they are much smaller than those of I. bajarunasi Glickman and Zhelezko, 1985 from the middle Eocene of Kazakhstan (see Adnet et al., 2021 for details). Udovichenko (2006) noted the presence of the latter species in the middle Eocene of Hradyzk ( Ukraine). We assume that the specimen depicted there should rather be assigned to I. affinis . It is, however, possible that teeth of taxa such as Anomotodon may be mixed in this sample.
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