Paraostenia striata ( Glaessner, 1931 ), 2024

Paraostenia striata ( Glaessner, 1931) comb. nov.

Fig. 6 View Fig .

1931 Austriocaris striata sp. nov.; Glaessner, 1931: 483, 484, text-figs. 7, 8.

1984 Ostenia striata ( Glaessner, 1931) ; Briggs and Rolfe 1983: 270, text-fig. 6b.

1984 Austriocaris striata Glaessner, 1931 ; Arduini and Brasca 1984: 92.

1986 Austriocaris striata Glaessner, 1931 ; Tintori et al. 1986: 241.

1990 Austriocaris striata Glaessner, 1931 ; Dalla Vecchia and Muscio 1990: 41.

2014 Atropicaris striata ( Glaessner, 1931) ; Schram 2014: 352.

2015 Ostenocaris striata ( Glaessner, 1931) ; Ehiro et al. 2015: 279, table 1.

2019 Austriocaris striata Glaessner, 1931 ; Teruzzi and Muscio 2019: 54.

2019 Atropicaris striata ( Glaessner, 1931) ; Charbonnier et al. 2019: table 1.

2021 Microcaris ( Atropicaris) striata ( Glaessner, 1931) ; Ji et al. 2021: 311, table 1.

2021 Atropicaris striata ( Glaessner, 1931) ; Laville et al. 2021: table 1.

2021 Atropicaris striata ( Glaessner, 1931) ; Lukeneder and Lukeneder

2021: fig. 3M, table 1. 2023 Atropicaris striata ( Glaessner, 1931) ; Lukeneder and Lukeneder

2023: fig. 3P, table 1. 2024 Atropicaris striata ( Glaessner, 1931) ; Lukeneder et al. 2024: 21. Holotype: NHMW 1910/0015/0042, complete shield. Type locality: Polzberg near Lunz am See, Austria. Type horizon: Reingraben formation, Austrotrachyceras austriacum Zone , Austrotrachyceras minor Biohorizon, Julian 2 Ib, Carnian, Upper Triassic.

Diagnosis (this study).— Paraostenia with thin transversal and slightly sigmoid ridges on the shield.

Material.— Type material and eight specimens: NHMW 1910 View Materials /0015/0034, 0036, 0043; NHMW 2021 View Materials /0123/0770, 0772, 0791, 0796, 0797. All from the type locality and horizon.

Dimensions. —See Table 1.

Description.—Shield morphology: Curved pentagonal-shaped shield in lateral view, longer than large ( Fig. 6A View Fig 1 –A View Fig 3 View Fig , B 1 –C View Fig 2 View Fig ). Maximal height reached around mid-length. Anterior margin made of a well-developed, symmetric optic notch, occupying the entire margin ( Fig. 6B View Fig ). Sharp anterodorsal corner. Convex dorsal midline. Rounded posterodorsal and posteroventral corners. Short, concave posterior margin, posteroventrally tilted ( Fig. 6A View Fig 1 –A View Fig 3 View Fig ). Ventral margin made of a horizontal anterior part and a slightly concave posterior one, anteroventrally tilted; both parts having approximately the same length ( Fig. 6A View Fig ). Rounded anteroventral corner ( Fig. 6C View Fig 3 View Fig ). Marginal fold delimited by a shallow groove near all free margins ( Fig. 6A View Fig 4 View Fig ).

Shield macro-ornamentation: Shield with a commashaped ventrolateral furrow ( Fig. 6A View Fig 1 –A View Fig 3 View Fig ). Anterior part of the ventral margin adorned with at least 17 small tubercles near the anteroventral corner ( Fig. 6C View Fig 3 View Fig ). Shield covered of at least 140 thin slightly sigmoid transverse ridges, posteroventrally oriented in the first quarter of the shield, vertical in the second quarter; in the second half of the shield, ridges being vertical in the dorsal part and becoming anteroventrally tilted near the posterior part of the ventral margin ( Fig. 6A View Fig 1 –A View Fig 4 View Fig ).

Other structures: Appendages, posterior trunk and soft parts not preserved.

Remarks.—The specie s A. striata was first assigned by Glaesnner (1931) to Austriocaris . Many years later, Briggs and Rolfe (1983) noticed the differences between the specimens of A. striata and Austriocaris . Austriocaris has a rostrum, an optic notch restricted to the ventral part of the anterior margin, a straight dorsal midline, a spiny posterodorsal corner, a straight dorsal margin and a shield covered by three lateral carinae while A. striata does not have a rostrum and lateral carinae but have a convex dorsal midline, a rounded posterodorsal corner and a concave dorsal margin. Briggs and Rolfe (1983) thus decided to assign this species to Ostenocaris Arduini et al., 1984 (known as Ostenia at that time). However, A. striata differs from Ostenocaris species by the morphologies of the anterior margin (optic notch in A. striata , sinuous and proverse in Ostenocaris ) and of the posterior margin (concave vs. straight). The confusion of Briggs and Rolfe (1983) might come from the fact that in the original description of Ostenocaris cypriformis Arduini et al., 1984 , the type species of Ostenocaris , some specimens of Paraostenia have been assigned, provoking many misidentifications as explained by Laville et al. 2021).

A year after Briggs and Rolfe (1983), Arduini and Brasca 1984) reassigned A. striata to Atropicaris based mostly on the presence of ridges and of a rostrum. This choice was later followed by most authors (e.g., Dalla Vecchia and Muscio 1990; Schram 2014; Ehiro et al. 2015; Ji et al. 2021 as Microcaris ( Atropicaris) striata ; Laville et al. 2021). As explained above for Atropicaris ? sp., several specimens assigned to A. striata actually have a morphology quite different from the holotype, and are most likely belonging to Atropicaris . However, the holotype and additional specimens mentioned here differ from Atropicaris species especially by the absence of a rostrum, by the presence of an optic notch and by the horizontal morphology of the anterior part of the ventral margin.

Actually, A. striata possesses the typical characters of Paraostenia Secrétan, 1985 : a large optic notch, a sharp anterodorsal corner, a rounded anteroventral corner, a concave posterior margin, a rounded posterodorsal corner and a horizontal anterior part of the ventral margin. A. striata should be assigned to Paraostenia . We therefore propose a new combination Paraostenia striata comb. nov. for this species.

Paraostenia striata display a unique character among Paraostenia : the thin transversal ridges. Even though shield macro-ornamentation is well-known in other Paraostenia species (horseshoe-like ornamentation in Paraostenia voultensis Secrétan, 1985 ; longitudinal ridges in Paraostenia ambatolokobensis [ Arduini, 1990]), thin transversal ridges are only known in P. striata .

In addition, P. striata does not carry any lateral or dorsal carina, unlike other species. Nevertheless, due to the poor preservation of the dorsal midline or to the butterfly configuration of the specimens, it is difficult to accurately determine the presence or absence of a dorsal carina.

Stratigraphic and geographic range.—Carnian, Upper Triassic of Austria.