Merluccius, 1810

Lin, Chien-Hsiang, Brzobohatý, Rostislav, Nolf, Dirk & Girone, Angela, 2017, Tortonian teleost otoliths from northern Italy: taxonomic synthesis and stratigraphic significance, European Journal of Taxonomy 322, pp. 1-44 : 10-11

“ Merluccius ” rattazzii sp. nov.

urn:lsid:zoobank.org:act:658A81A3-5E45-4D56-B3C6-DF85AA002A5D

Fig. 8 C–D

Diagnosis

The species is characterised by elongate otoliths. The highest part of the otolith is in the middle of the dorsal rim. The thickest portion of the otolith is near the junction of the ostium and cauda. The pincenez-shaped sulcus is characterised by an elliptic ostial colliculum and a much longer, dorsally directed caudal colliculum.

Etymology

This species is named in honor of Bruno Rattazzi, who collected the type specimens.

Type material examined

Holotype

ITALY: a right otolith ( IRSNB P 9686 , Fig. 8 C ).

Paratypes

ITALY: two specimens, of which one is figured ( IRSNB P 9687, Fig. 8D ).

Type locality and horizon

ITALY: Tortonian Clay at Sant’ Alosio, surface collected.

Dimensions of the holotype

Length = 13.35 mm, height = 5.15 mm, thickness = 1.85 mm.

Description

The otoliths of this species are large and elongate. They are moderately thick, with a convex inner face and a flat outer face. The anterior rim is rounded and the posterior rim, which is higher than the anterior one, is blunt. The ventral rim is gently curved; the dorsal rim is highest in the middle, and gently becomes lower at the anterior and posterior parts. The margins of all the rims are smooth. The sulcus is large, pince-nez-shaped, and deep; the delimitation of the sulcus becomes less clear at the anterior end. There is a channel opening dorsally at the antero-dorsal part of the ostium. The crista superior is wellmarked, with its central part the most prominent and marking its lowest trajectory; the crista inferior is somewhat less salient in its central part. The collicula are both well developed and their margins are well-separated from the cristae. The ostial colliculum is elliptic and lies more or less horizontally, while the caudal one is elongate, widened and dorsally directed in its posterior part. The dorsal depression is small and shallow.

Remarks

The here described otoliths are apparently related to the merlucciids (subfamily Merlucciinae ), like the Recent Merluccius and the extinct genus Palaeogadus Rath, 1859 , but they differ from those of Merluccius by their very smooth margins and their rounded anterior and posterior portions, while otoliths of Palaeogadus show more elongate otoliths with markedly acuminated anterior and posterior portions and well-developed rostrums. In addition, the otoliths of Palaeogadus have a very large and high cauda as opposed to those of Merluccius where their ostium and cauda are of roughly the same size, but this is a more variable feature (see Nolf 2013: pls 101–104). The new species apparently belong to an extinct deep-water taxon of the merlucciids.

Figures

Fig. 8. Tortonian fish otoliths from northern Italy. A. Coelorinchus caelorhincus (Risso, 1810), Montegibbio (IRSNB P 9772). B. Coryphaenoides contortus (Bassoli, 1906), Sant’Alosio (IRSNB P 9773). C–D. “Merluccius” rattazzii sp. nov., Sant’Alosio (IRSNB P 9686 (holotype)–P 9687). E–F. Coryphaenoides biobtusus sp. nov., Alba, Tanaro (5 m) (IRSNB P 9684 (holotype)–P 9685). G–H. Nezumia aff. sclerorhynchus (Valenciennes, 1838), Alba, Tanaro (5 m) (IRSNB P 9774–P 9775). I–J. Moridae indet., Sant’Agata Fossili (IRSNB P 9776–P 9777). K. Nezumia ornata (Bassoli, 1906), Montegibbio (IRSNB P 9778). L–M. Coelorinchus robustus (Robba, 1970); L. Stazzano, M. Sant’Alosio (IRSNB P 9779–P 9780). N. Gadiculus labiatus (Schubert, 1905), Torrente Stirone (IRSNB P 9781). O–P. Melanonus paralyconus Schwarzhans, 1986, Mondovi, Madonna della Neve (IRSNB P 9782– P 9783). Q–R. Melanonus triangulus (Robba, 1970), Costa Vescovato (IRSNB P 9784–P 9785). S. Gadiculus argenteus Guichenot, 1850, Torrente Stirone (IRSNB P 9786). 1 = ventral view; 2 = inner view. Scale bars = 1 mm.