Allothrissops Nybelin 1964

Allothrissops Nybelin, 1964 Figs 17 A, B Type species. Allothrissops salmoneus (Blainville, 1818 b) Remarks. The Upper Jurassic genus Allothrissops Nybelin, 1964, is problematic and needs to be revised. The existing literature has probably caused more confusion than clarity, because some important authors on this taxon (Blainville 1818 a, b; Agassiz 1833 –43 and Nybelin 1964) described fish from different species under the name of the type species Allothrissops salmoneus (Blainville, 1818 b). The holotype of the type species Allothrissops salmoneus (Blainville, 1818 b) which is figured in Knorr (1755, pl. 31, fig. 1) is lost. Unfortunately, the illustration in Knorr (1755) does not show any diagnostic feature on species level. The specimen was most likely from Zandt (Zandt Basin, Solnhofen Archipelago, for localities see Fig. 1) due to the Liesegang rings typical for the Plattenkalk of Zandt depicted in Knorr (1755). The neotype (NHMUK PV OR 37078), proposed by Nybelin (1964), however, came from the Solnhofen Basin of the Solnhofen Archipelago (Fig. 1). Blainville (1818 a, p. 331) first names this species “ Clupea elongata ”. But since the species Clupea elongata Sesueur, 1818 (later recognized as synonymous with Clupea harengus Linneus, 1758) was described in the same year, Blainville (1818 b, p. 27) renamed his species Clupea salmonea. Nybelin (1964) split the genus Allothrissops from Thrissops Agassiz, 1833 with the species Allothrissops salmoneus, A. mesogaster both from Southern Germany and A. regleyi from Cerin, France. However, the species Thrissops salmoneus described by Agassiz (1833) is not identical to the species Allothrissops salmoneus described by Nybelin (1964). All Th. salmoneus specimens, which Nybelin (1964) mentioned in his investigations originate from Eichstätt or Solnhofen, whereas those figured in the unpublished drawings intended for Agassiz’s work LDGSL / 614 / 2 / 167, LDGSL / 614 / 2 / 168 come from Kelheim (except for a specimen in Prague LDGSL / 614 / 2 / 166 (NMP Uc 64, missing today, see Ebert et al. 2022, fig. 18) which comes from Solnhofen, but cannot be determined more precisely due to its poor preservation. The unpublished drawings to Agassiz (1833 –43) work are today in the Geological Society of London’s collection and online available (refs: LDGSL / 613–616). Evidence for the different interpretations of the species A. salmoneus may also be that Agassiz (1843, p. 128) says Allothrissops mesogaster is more elongated than A. salmoneus (“ Thrissops mesogaster … une espèce très-voisine du Th. salmoneus, mais un peu plus allongée … ”), whereas Nybelin (1964) described it the other way around. Abbreviation of features: AP, number of anal pterygiophores; AV, number of abdominal vertebrae; CV, number of caudal vertebrae, max. SL, maximal standard length (cm); Ribs, number of abdominal ribs; SL / BD, standard length in relationship to body depth; SN, number of supraneurals; Teeth, size of teeth; TV, number of total vertebrae (without ural centra); UD, number of urodermals. Abbreviation of localities: Br, Brunn; Ei, Eichstätt; Et, Ettling; Ke, Kelheim; Pa, Painten; So, Solnhofen; Za, Zandt.