Petasobairdia amazonella Forel 2020, sp. nov.
Creators: name: Forel, Marie-Béatrice
name: Grădinaru, Eugen
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Ostracoda
Halocyprida
Bairdiidae
Petasobairdia
Petasobairdia amazonella

description: Petasobairdia amazonella Forel sp. nov.
urn:lsid:zoobank.org:act: BC1BE3CA-3515-49D8-A4A8-8EABDD0C0EE1
Figs 9 Q–U, 10A–D
Diagnosis
A new species of Petasobairdia, short for the genus, triangular in outline with high anterior border.
Etymology
From Ἀμαζóνες/Amazónes, the legendary tribe of warrior women who, according to tradition, used to live along the Black Sea shore.
Material examined
Holotype
ROMANIA • 1 LV; Black Sea, Romanian Continental Shelf, borehole 817LV, sample CM31C; Rhaetian, Upper Triassic; MNHN.F. F63264.
Paratype
ROMANIA • 1 complete carapace; same locality as for holotype but sample CM31B; Rhaetian, Upper Triassic; MNHN.F. F63261.
Other material
ROMANIA • 1 complete carapace; same collection data as for holotype; Rhaetian, Upper Triassic; MNHN.F. F63259 • 1 complete carapace; same locality as for preceding but sample CM31A; Rhaetian, Upper Triassic; MNHN.F. F63260 • 1 complete carapace; same collection data as for preceding; Rhaetian, Upper Triassic; MNHN.F. F63263 • 1 complete carapace; same locality as for preceding but sample CM31B; Rhaetian, Upper Triassic; MNHN.F. F63262 • 4 complete carapaces, 1 RV, 1 LV; same locality as for preceding but samples CM31A, CM31B and CM31C; Rhaetian, Upper Triassic; MNHN.F. F63356.
Dimensions
See Fig. 3G.
Description
Carapace of medium size, sub-square in lateral view, with H max at antero-dorsal angulation and L max below mid-L; LV larger than RV, overlapping it slightly ventrally at ventral concavity and along dorsal margin with laterally compressed overreach along DB; dorsal margin tripartite with rounded angulations at both valves; PDB straight, steep (from 60° in largest specimens to 80° in smallest ones) and short (from 5% of L max in smallest specimens to 20% in larger forms); ADB and DB straight and approximately of same L (40–45% of L max); ADB slope of ±30–40°; DB sloping posteriorly from 10° to 15°; AB large, only poorly tapered ventrally, laterally compressed ventrally, with maximum of curvature slightly below mid-H; ventral margin long and straight with median concavity visible on some specimens; PB narrow, laterally compressed ventrally, with maximum of curvature located in lower ¼ of H max; surface smooth; calcified inner lamella from mid-ADB to mid-PDB, relatively wide along AVB and PVB; large vestibulum along AVB and PVB, narrow in oral area; hinge bar seemingly smooth with anterior and posterior enlarged platforms; AMS field relatively compact, somewhat hastate, located below mid-H and around mid-L, composed of anteriorly incurved row of 3 individual scars and 2 to 3 scars aligned in a short posterior row (Fig. 10D).
Occurrence
Romanian Continental Shelf, Black Sea, Rhaetian, Upper Triassic (this paper).
Remarks
The laterally compressed overlap of Petasobairdia amazonella sp. nov. relates it to the Permian species P. silenitiformis (Kozur, 1985), P. nantongensis Chen, 1982 and P. subnantongensis Chen in Shi & Chen, 1987, for instance, but its shortness, with the posterior maximum of convexity located ventrally, providing it with a sub-square outline in lateral view, differ from conditions in all known species. Although poorly preserved, the AMS pattern on the inner surface of the paratype (Fig. 10D) only differs from that of P. silenitiformis, which is to our knowledge the only observation of AMS for Petasobairdia, in being more compact and less rounded. In general terms, the outline of P. amazonella sp. nov. is reminiscent of that in Bairdia donzei Herrig, 1979 from the Domerian, Early Jurassic, of Germany (Herrig 1979a), but this Jurassic species has a longer posterior extremity and its LV is more rounded in outline and lacks the laterally compressed DB. The H/L scatter plot of all specimens of P. amazonella sp. nov. (Fig. 3G) records the occurrence of several ontogenetic stages, from A-4 to adult. The holotype (Fig. 9 S–T) and paratype (Fig. 10 B–D) are the largest known specimens, but owing to the size difference between the paratype and the LV of the holotype, we consider that the holotype is a submature stage. The development of P. amazonella sp. nov. is marked by the increasing height of the overlap as well as the elongation of the PDB, from 5% of L max in the smallest instar to 27% in the paratype, the largest known specimen to date (Fig. 3G).
description: Published as part of Forel, Marie-Béatrice & Grădinaru, Eugen, 2020, Rhaetian (Late Triassic) ostracods (Crustacea, Ostracoda) from the offshore prolongation of the North Dobrogean Orogen into the Romanian Black Sea shelf, pp. 1-83 in European Journal of Taxonomy 727 on pages 43-44, DOI: 10.5852/ejt.2020.727.1183, http://zenodo.org/record/4316845