Paralenorthis lolae Reyes−Abril and Villas, 2010
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publication ID |
https://doi.org/ 10.4202/app.2009.0032 |
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persistent identifier |
https://treatment.plazi.org/id/03E4879F-726D-9577-1266-FDC8FB9B35C7 |
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treatment provided by |
Felipe |
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scientific name |
Paralenorthis lolae Reyes−Abril and Villas |
| status |
sp. nov. |
Paralenorthis lolae Reyes−Abril and Villas sp. nov.
Fig. 8 View Fig .
Etymology: Species dedicated to Dolores González−Mosquera, Lola , great defender of the palaeontological heritage of Navas de Estena and the nearby Cabañeros National Park.
Type material: Holotype: MGM−6121−O, internal mould of ventral valve. Paratypes: five internal moulds and twelve external moulds of ventral valves, nine external moulds and twelve internal moulds of dorsal valves, and internal and external moulds of three ventral valves and eleven dorsal valves, with numbers: MGM−6117−O to MGM−6169−O.
Type locality: SP−II, 5000 m SW of San Pablo de los Montes, Toledo Province, Spain. UTM coordinates:lat 39 ° 30'33''N , long 4 ° 20'44''W.
Type horizon: 110 metres above the base of the Navas de Estena Formation , Didymograptus artus Biozone , lower Oretanian , middle Darriwilian Stage of the Middle Ordovician Series .
Diagnosis.—Semicircular shells of Paralenorthis with rectangular to slightly acute cardinal angles, weakly carinate ventral valve and sulcate dorsal valve, short interareas and costate ornamentation, capillate and filate, with 18–26 ribs; subtriangular ventral muscle field, 23–36% as long as valve; thin and short blade−like cardinal process and wide median ridge reaching mid valve length.
Description.—Shell planoconvex to ventribiconvex, up to 17 mm long with semicircular outline, maximum width at hinge line, rectangular to slightly acute cardinal angles, 60– 82% as long as wide and slightly sulcate anterior commissure. Ventral valve convex, slightly carinate, 15–38% as deep as long; ventral interarea short, 3–8% as long as valve, apsacline and curved, with open delthyrium. Dorsal valve plane to weakly convex, 52–73% as long as wide, weakly sulcate, with no more than 2 costae on sulcus; dorsal interarea anacline, plane, shorter than ventral interarea, with open notothyrium. Radial ornamentation costate, filate and capillate, with only a few postero−lateral ribs subparallel to hinge line, arising beyond umbo and thickened median costa, observed on ventral valve MGM−6242−O ( Fig. 8D View Fig ); ribs high with rounded crests, numbering 18 to 26 at valve margin, with commonest number 20, and 4–6 costae per 5 mm at 5 mm anteromedially from umbo.
Ventral interior with triangular, blunt teeth and well developed crural fossettes, dental plates short, divergent onto valve floor and continuous anteriorly with low muscle bounding ridges; subtriangular muscle field, with adductor track about the same width and length as diductor scars, not enclosed anteriorly, 23–36% as long as valve (m = 29%, v = 0.1%, n =9), 18–26% as wide as valve (m = 22%, v = 0.1%, n = 9). Divergent vascula media, poorly impressed and strongly incurved postero−laterally by mid valve length.
Dorsal interior with short notothyrial platform, posteriorly sloping and continuous anteriorly with high and variably wide median ridge, reaching mid valve length and greatly enlarged in adult stages; cardinal process blade−like, short and thin; brachiophores rod−like, strongly divergent, welded to notothyrial platform; dental sockets excavated on secondary shell deposits; muscle field quadripartite, well impressed only in adult stages, with subequal adductor scars.
doi:10.4202/app.2009.0032
Radial ornamentation strongly impressed on interior of young shell; internal margins of adult valves crenulated with deep and narrow grooves that correspond to crest of ribs, and wide eminences with shallow sulci on intercostal spaces.
Discussion.—These shells are externally very close to those of several Paralenorthis species with reduced rib numbers, as the Baltoscandian Paralenorthis orbicularis (Pander, 1830) , the British Paralenorthis proava (Salter, 1866) , the Chinese Paralenorthis serica (Martelli, 1901) , the North American Paralenorthis buttsi (Schuchert and Cooper, 1932) , Paralenorthis parvicrassicostata (Cooper, 1956) and Paralenorthis robusta (Neuman, 1964) , the Argentine Paralenorthis vulgaris Herrera and Benedetto, 1989 and Paralenorthis altiplanica Benedetto, 1998 , and the Peruvian Paralenorthis carlottoi Villas in Gutiérrez−Marco and Villas, 2007, but display a combination of features distinctive enough within Paralenorthis to propose the erection of a new species. Of the species above, it can be distinguished from P. orbicularis by its non mucronate outline and from P. proava by its weakly sulcate dorsal valve, with no more than two median costae on the sulcus, while there are four ribs in P. proava . It differs from P. serica in its longer ventral muscle field and longer nothotyrial platform (see Xu and Liu 1984: pl. 2: 15, 16, 19–29). The new species differs from P. buttsi in the form of their brachiophore bases, strongly convergent towards the bottom of the notothyrial cavity in the latter; from P. parvicrassicostata by the non capillate external surface of this species (see Williams 1974). Its semicircular, transversely elongated outline, allows easy distinction from P. robusta , of rounded outline. It can be distinguished from P. vulgaris by its transversely elongated outline and shorter ventral interarea, and from P. altiplanica by its much broader notothyrial platform and longer dorsal median ridge. Finally, it differs from P. carlottoi by its transversely elongated outline, with shells never more than 80% as long as wide, while P. carlottoi can be up to 98% as long as wide, as well as by its shorter ventral interarea that is no more than 8% as long as the valve, while those values range in P. carlottoi between 10% and 15%.
The lack of auriculation in the new species allows a ready distinction from the British P. alata, the Argentine P. riojana (Levy and Nullo, 1973) and P. suriensis Benedetto, 2003a , as well as the North American P. marshalli ( Wilson, 1926) , P.? minuscula (Phleger, 1933) and P.? angulata (Cooper, 1956). The new species can be also distinguished from P. estenaensis Reyes−Abril and Villas sp. nov. by its lower rib number, non−varying outline with growth and shorter ventral muscle field.
Stratigraphic and geographic range.—Known from the Navas de Estena syncline (localities NE−II and NE−IIA), in the lower horizons of the Navas de Estena Shales, and from eastern Sierra Morena (localities CC−IIIA, Calzada de Calatrava; VM−I, Viso del Marqués, Ciudad Real Province) and AQ−II, Aldeaquemada, Jaén Province), in the lower part of the Río Formation.
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