Ischyodus sp.

Otero, Rodrigo A., Bravo, Constanza Figueroa, Soto-Huenchumán, Paula, Fernández-Collemann, Sara, Valenzuela-Toro, Ana M. & Gutstein, Carolina S., 2021, First record of chimaeroid fish Ischyodus from the Upper Jurassic of southwestern Gondwana, Acta Palaeontologica Polonica 66 (3), pp. 623-630 : 626

Ischyodus sp.

Fig. 3B .

Material.— MHNC.35.445, an isolated, fragmentary right palatine plate from Mina Del Fierro , Andes Cordillera , Región del Maule, Chile; Baños del Flaco Formation , Tithonian (Upper Jurassic) .

Description.—MHNC.35.445 is an isolated and poorly preserved palatine plate attached to the matrix. The basal surface is lost, allowing us to see the internal part of the tritors. The labial and symphyseal contour are preserved as a cast in the sandstone matrix, allowing us to observe the triangular shape of the plate. The posterior inner tritor is suboval and it is the larger tritor in the plate. The labial margin shows three aligned tritors, identified as fragments of the median tritor, the outer tritor, and the anterior inner tritor.

Remarks.—MHNC.35.445 possesses a large, oval posterior inner tritor, a median tritor likely smaller, an outer tritor axially elongated, and an anterior inner tritor slightly rounded. These features are present in different species of the Ischyodus ( Stahl 1999: fig. 138A, C; Popov and Machalski 2014: fig. 4D1). The incompleteness of this mandibular plate precludes a more specific identification.

Figures

Fig. 3. Chimaeroid fishes from Mina Del Fierro, Andes Cordillera, Región del Maule, Chile; Baños del Flaco Formation, Tithonian (Upper Jurassic). A. Ischyodus townsendi (Buckland, 1835) (MHNC.35.444); two articulated mandibular plates in basal view. B. Ischyodus sp. (MHNC.35.445); ventral view of the bony contour of a right palatine attached to the matrix, preserving the occlusal surface of the tritors.Abbreviations: ait, anterior inner tritor; aot, anterior outer tritor; bk, beak; lm, left mandibular; mt, median tritor; out, outer tritor; pit, posterior inner tritor; plm, prominence of the labial margin; pot, posterior outer tritor; r, ridges; rm, right mandibular; syt, symphyseal tritor. Photographs (A1, B1), schematic illustrations (A2, B2).