Paratrematoceras Schastlivceva, 1981

Pohle, Alexander & Klug, Christian, 2024, Orthoceratoid and coleoid cephalopods from the Middle Triassic of Switzerland with an updated taxonomic framework for Triassic Orthoceratoidea, Swiss Journal of Palaeontology (14) 143 (1), pp. 1-32 : 26

Genus Paratrematoceras Schastlivceva, 1981

Diagnosis: Trematoceratid with narrow, tubular siphuncle with short orthochoanitic septal necks that sharply bend in adapically at the transition to the septum.

Type species: P. shevyrevi Schastlivceva, 1981

Included species: P. ornatum Schastlivceva, 1981 ; P. salinarium (Hauer, 1846) comb. nov.

Remarks: Differs from Trematoceras in its narrower siphuncle with sharply bent, orthochoanitic septal necks.

In addition to the species listed by Schastlivceva (1988), which includes specimens described as Trematoceras aff. dubium from the Olenekian of Afghanistan (Kummel & Erben, 1968), Orthoceras salinarium Hauer, 1846 from the Norian of Austria may be referred to the genus, as it has a similarly narrow siphuncle with sharply bent septal necks. However, this is purely based on Hauer’s (1846) drawings and investigation of his type material is required to test this assignment. Michelinoceras sp. A in Tongtherm et al. (2016) from the Anisian of Tailand possibly belongs to Paratrematoceras due to its narrow siphuncle and orthochoanitic septal necks. Several species from Olenekian to Anisian deposits have been assigned to Paratrematoceras by Grădinaru et al. (2007), but since they were not accompanied by illustrations, they represent nomina nuda and the presence of the genus in these rocks is unconfirmed. Consequently, the genus appears to be already present and relatively widespread in the early Middle Triassic, although further studies are needed to differentiate it from Trematoceras with certainty.

Occurrence: Northern Caucasus, Alps?, Tailand?; Middle Triassic (Anisian)?, Late Triassic (Norian).