Archaeoconularia cf. insignis ( Barrande, 1867 )

Iten, Heyo Van & Lefebvre, Bertrand, 2020, Conulariids from the Lower Ordovician of the southern Montagne Noire, France, Acta Palaeontologica Polonica 65 (3), pp. 629-639 : 632

Archaeoconularia cf. insignis ( Barrande, 1867)

Fig. 3 .

1966 Eoconularia ? cf. azaisi ( Thoral, 1935) ; Dean 1966: 271.

1978 Eoconularia cf. azaisi ( Thoral, 1935) ; Capéra et al. 1978: 75.

2001 Eoconularia cf. azaisi ( Thoral, 1935) ; Vizcaïno et al. 2001: 219, fig. 3.

2016 Conularia cf. azaisi Thoral, 1935 ; Van Iten et al. 2016b: 171, table 1.

Material.— Four specimens from the late Floian Landeyran Formation: NHN.F.A71848a, b, A71849, and A71850 from the Apatokephalus incisus Zone ; les Sources du Foulon, Cessenon, Hérault; MNHN.F.A71851a, b, from the Hangchungolithus primitivus Zone ; les Rocs Nègres, Causses-et-Veyran, Hérault. All Montagne Noire, France .

Description.—Mostcompletespecimen( MNHN.F.A71851a, b; Fig. 3A, 3B , respectively) flattened, lacking the apertural margin but terminating at the apical end in a crumpled schott apical wall; Fig. 3A 2 ), measuring approximately 31 mm in length, with a maximum single face width of approximately 10 mm and a minimum single face width of approximately 0.5 mm. Faces approximately equal in width, with the corners bounding a given face diverging from each other at approximately 20°. Midline sulcus appears to be deeper than the corner sulcus; both the midline sulcus and the corner sulcus simple (without internal carina or other thickening). Minute, circular to subcircular nodes ( Fig. 3B 2 ) on the faces arranged in gently arching, bell-curve-shaped transverse rows and less distinct longitudinal files, with approximately 15–20 transverse rows per mm and approximately 15 longitudinal files per mm.

Remarks.—Of all previously described species of Archaeoconularia ( Barrande 1867; Slater 1907; Bouček 1928, 1939; Reed 1933; Sinclair 1943; Sayar 1964; Van Iten et al. 2020), the four incomplete specimens here described from the Landeyran Formation appear to be most similar to A. insignis , a species with relatively small nodes (12–30 per mm; Bouček 1928) that occurs in the late Tremadocian (Lower Ordovician) Mílina Formation of Perunica ( Czech Republic; Van Iten et al. 2016b). Both the French specimens and A. insignis are also similar to specimens identified as Archaeoconularia sp. from the late Tremadocian–middle Floian (Lower Ordovician) Fezouata Shale of southern Morocco ( Van Iten et al. 2016b) and may be conspecific with them. Like the material from the Landeyran Formation, the Fezouata Shale specimens occur in pale green-brown or pale gray-green mudstone. Additionally, a single specimen illustrated by Van Iten et al. (2013: fig. 3b) from pale greengrey shale in the early Floian (Lower Ordovician) Tonggao Formation of South China, and identified by these authors as “Conulariid sp. and gen. indeterminate” ( Van Iten et al. 2013: 719), closely resembles deeply exfoliated specimens of A. exquisita from the Middle or Upper Ordovician of Bohemia (see in particular Bouček 1928: pl. 2: 7); therefore it is probably a specimen of Archaeoconularia . In sum, then, A. insignis or a species closely related to it appears to be present both in the Lower Ordovician of Morocco and the southern Montagne Noire (Gondwana), and Archaeoconularia is also present in the Lower Ordovician of Perunica, Avalonia, and, probably, South China. Collectively, these five Early Ordovician areas spanned a broad range of palaeolatitudes extending from near the South Pole to the southern subtropics (see Van Iten et al. 2013: fig. 5).

Figures

Fig. 3. Conulariid scyphozoan Archaeoconularia cf. insignis (Barrande, 1867), Landeyran Formation, upper Floian, Lower Ordovician; southern Montagne Noire, France. Specimens oriented with the apertural end directed toward the top of the page; arrows in A1 and B1 point to a facial midline. A. The two exposed faces of the part of the most complete specimen (MNHN.F.A71851a), which terminates in a crumpled schott (A1). Detail of the part, arrow pointing to the crumpled terminal schott (A2). B. The counterpart of the specimen in A (MNHN.F.A71851b) (B1). Detail of the apertural region of the counterpart, showing the fine ornament including some of the most clearly defined nodes (arrows) (B2).

Fig. 2. Stratigraphic range of conulariids in the Lower Ordovician of the southern Montagne Noire. Stratigraphic column redrawn and modified from Courtessole et al. (1983). Stratigraphy based on Vizcaïno et al. (2001), Álvaro and Vizcaïno (2003), Tortello et al. (2006), and Serpagli et al. (2007).