Acanthochirana cordata ( Münster, 1839 )

Odin, Giliane P., Charbonnier, Sylvain, Devillez, Julien & Schweigert, Günter, 2019, On unreported historical specimens of marine arthropods from the Solnhofen and Nusplingen Lithographic Limestones (Late Jurassic, Germany) housed at the Muséum national d’Histoire naturelle, Paris, Geodiversitas 41 (17), pp. 643-662 : 647-648

Acanthochirana cordata ( Münster, 1839) ( Fig. 2 ) STUDIED MATERIAL. — We studied three specimens, MNHN.F. A33503 , R03389 (Solnhofen) and A42003 (Eichstätt), respectively attributed by Charbonnier & Garassino (2012) to Bylgia hexadon Münster, 1839, Aeger tipularius , and Acanthochirana longipes ( Oppel, 1862).

COMMENTS

Charbonnier & Garassino (2012) identified the specimen MNHN.F.A42003 as A. longipes. Careful examination of this

specimen leads us to a different identification. Among the criteria listed in the diagnosis by Schweigert et al. (2016), the number of dorsal rostral teeth and the elongation of Mxp3 are the most important to distinguish A. cordata from A. longipes. Since it was impossible to count the teeth on our specimens, we use the ratio Mxp3 length / cephalothorax length. Based on drawings from Oppel (1862), the ratio is ≤1 for A. cordata while >>1 for A. longipes. The ratio measured on this specimen is of 0.9, implying an assignation to A. cordata .

Specimen A33503 ( Fig. 2A, B ), previously attributed to Bylgia hexadon, was misidentified: it clearly shows elongate Mxp3 with moveable spines characteristic of aegerid shrimps. More precisely, the length of Mxp3 fits well with those observed in Acanthochirana . Additionally, this specimen shows a spiny rostral carina prolonged by a smooth rostrum and an epigastric spine, which allow us to ascribe the specimen to Acanthochirana cordata .

Specimen MNHN.F.R03389 ( Fig. 2C, D ), previously attributed to Aeger tipularius , was also misidentified: it clearly shows elongate Mxp3 with moveable spines characteristic of aegerid shrimps but the length of Mxp3 fits well with those observed in Acanthochirana . Also, the carapace groove pattern is typical of Acanthochirana , showing a weak cervical groove not joined to the cervical margin, an oblique branchiocardiac groove joined to the hepatic groove near the strong hepatic spine and a short hepatic groove backward directed (see diagnosis in Charbonnier et al. 2017: 32).

Figures

FIG. 2. — Acanthochirana cordata (Münster, 1839): A, B, specimen MNHN.F.A33503 from Solnhofen; A, natural light; B, interpretation of the carapace; C, D, specimen MNHN.F.R03389 from Solnhofen; C, visible light; D, interpretation of the carapace. Scale bars: A, B, D, 1 cm; C, 2 cm. Abbreviations: a, branchiocardiac groove; b1, hepatic groove; e1e, cervical groove; egs, epigastric spine; hs, hepatic spine; r, rostrum. Photographs: L. Cazes. Line drawing: G.P. Odin.