Lobodon carcinophagus Hombron et Jacquinot, 1842

Koretsky, I. A., Rahmat, S. J. & Peters, N., 2014, Remarks On Correlations And Implications Of The Mandibular Structure And Diet In Some Seals (Mammalia, Phocidae), Vestnik Zoologii 48 (3), pp. 255-268 : 263

Lobodon carcinophagus Hombron et Jacquinot, 1842 ( fig. 6 , table 1)

The lesser degree of the condyloid angle is likely due to the short height of the mandibular ramus (table 1). The short condyloid process extends slightly superior to the tips of the teeth, specifically the canine, with a narrow mandibular notch. The short coronoid process is a slender triangle with a rounded apex. The anterior border of the coronoid process is slightly thicker, marking the site for attachment of the temporalis and masseter muscles. On the labial surface of the ramus is a rather weak, narrow masseteric fossa ( fig. 6 ). Between the posterior border of the molar and the coronoid process is a bony protuberance that fills in what would otherwise be a triangular gap when the mouth is closed. There is a medium-sized condyloid angle of 20°, which is smaller than most cystophorines and phocines, but larger than M. tropicalis .

The width of the masseteric fossa (4.0 cm) of Lobodon carcinophagus covers only 1/2 to 3/4 of the ramus length and is very shallow. The diminished size and lack of depth of the fossa indicates a significantly reduced and less developed masseter than in Monachus tropicalis and most of the other species discussed in this paper. The coronoid process, with a width and height of 2.0 cm is slightly smaller than in M. tropicalis and suggests that the temporalis muscle is either similar or smaller in size.

The common name “crabeater seal” is confusing because unlike most seals, the preferred prey of L. carcinophagus is small shrimp-like crustaceans known as krill belonging to the genus Euphausia ( King, 1961) . However, they do eat fish, squid and the occasional crab (Burns et al., 2004). Studies on L. carcinophagus confirm that the average diving depth is up to 528 m ( Schreer, Kovacs, 1997).

Рис. 6. Подсемейство Monachinae :. левая челюсть Lobodon carcinophagus (NMNH 28538), вид с губной стороны; показана жевательная ямка (пунктирной линией).

Figures

Fig. 6. Subfamily Monachinae: left mandible of Lobodon carcinophagus (NMNH 28538) in labial view showing masseteric fossa (dashed outline).