The oldest record of Eothinoceratidae (Ellesmerocerida, Nautiloidea): Middle Tremadocian of the Cordillera Oriental, NW Argentina

Abstract

Middle Tremadocian cephalopods from the Sierra de Mojotoro, Cordillera Oriental, NW Argentina, are assigned to Saloceras cf. sericeum (Salter) based on the siphuncle morphology and general shape of the conch. Saloceras sericeum (Salter) is known from the Upper Tremadocian and Floian of England and Wales, a region that formed part of eastern Avalonia during the Early Ordovician, located at a high southern latitude to the north of the Gondwanan margin. This is the oldest record of this genus and of the family Eothinoceratidae, and extends the geographical range of Saloceras, being the first positive record of its presence in Argentina and the Central Andean Basin. These remains are amongst the oldest cephalopods described from NWArgentina. They represent the third mid Tremadocian record of nautiloids at relatively high palaeolatitudes and away from the low latitude carbonate platform palaeoenvironments where the bulk of the earliest cephalopods resided.

Review and palaeoecological analysis of the late Tremadocian - early Floian (Early Ordovician) cephalopod fauna of the Montagne Noire, France

“…11) from the late Tremadocian Parcha Formation of Incamayo, Salta Province. Cichowolski et al (2010) have confirmed the presence of the Eothinoceratidae in Argentina by describing Saloceras cf. sericeum from mid Tremadocian horizons of the Floresta Formation, Salta Province.…”

Review of the Early to Mid Ordovician orthoconic cephalopods from Iran

“…In the Montagne Noire (Kröger & Evans 2011), a diverse Tremadocian assemblage is known to consist of Ellesmerocerida including the Eothinoceratidae, Cyclostomiceratidae and Rioceratidae; the endocerid family Proterocameroceratidae, and the earliest definite members of the Orthoceratoidea including baltoceratids, and a possible troedssonellid. Beyond the Montagne Noire the only other records of Tremadocian cephalopods along the high latitude margins of Gondwana consist of Saloceras from Avalonia (Evans 2005) and the Central Andean Basin (Cichowolski & Vaccari 2011). Thus the presence of a probable Bactroceras in the Tremadocian of the Eastern Alborz constitutes a significant addition to knowledge of these assemblages.…”

Palaeogeography and palaeoecology of early Floian (Early Ordovician) cephalopods from the Upper Fezouata Formation, Anti-Atlas, Morocco

“…australe from the middle Tremadocian Floresta Formation of Jujuy, Argentina are synonymised with Saloceras cf. sericeum Salter in Ramsay 1866 by Cichowolski & Vaccari (2011). However, because the internal characters of the specimen described by Cichowolski & Vaccari (2011) are very poorly known and the conch shape remains speculative, the possibility remains that the specimens from Argentina represent Bathmoceras.…”