Lychnothamnus vectensis ( Groves, 1926 ) Soulié-Märsche, 1989

Sanjuan, Josep & Martín-Closas, Carles, 2014, Taxonomy and palaeobiogeography of charophytes from the Upper Eocene- Lower Oligocene of the Eastern Ebro Basin (Catalonia, NE Spain), Geodiversitas 36 (3), pp. 385-420 : 404

Lychnothamnus vectensis ( Groves, 1926) Soulié-Märsche, 1989

( Fig. 8 D-G)

Chara vectensis Groves, 1926: 172 , pl. 2, figs 2-8.

Stephanochara vectensis – Grambast 1958: 158.

Lychnothamnus vectensis – Soulié-Märsche 1989: 160.

DISTRIBUTION. — Lychnothamnus vectensis has been recorded in the Hampshire ( Reid & Groves 1921) and Paris ( Riveline 1986) basins.In the Ebro Basin,this species occurs within Uppermost Priabonian-Lower Rupelian deposits in Santpedor, Rubió and Sarral (Tables 3, 4).

DESCRIPTION

Medium sized gyrogonite, variable in size, 580- 760 µm in high (mean 660 µm), and 480-620 µm in width (mean 560 µm), normally ellipsoidal but sometimes ovoidal in shape with an isopolarity index of 103-145 (mean 121). Spiral cells about 90 µm wide, normally flat to convex. Seven to nine (frequently eight), convolutions are visible laterally. Apex flat or slightly convex. Spiral cells do not show constrictions in the apical periphery but display marked thinning in the apical zone, resulting in an apical to periapical depression. In some gyrogonites, the apex is ornamented by tubercles that vary notably in size depending on the specimen. Ŋe base is rounded with a large and superficial basal pore about 70 µm across.

REMARKS

Chara vectensis was first determined by Groves (1926) based on ellipsoidal gyrogonites extremely variable in size, 800-1000 µm in high and 500- 800 µm in width, with 9-10 concave spiral cells usually swollen at the apex and often forming prominent rosettes. Ŋe holotype designated and illustrated by Groves (1926), from the A’Court Smith collection at the Natural History Museum, London, belonged precisely to the few specimens which displayed a prominent apical rosette and this character was further considered as diagnostic of the species, rather than as merely an extreme version of its total morphological variation. Taking into account this range of variation, the main difference between the material from the Ebro Basin and the type material is the size of the gyrogonites, which are about 200 µm smaller in the Ebro Basin. Gyrogonites of this species from the Paris Basin gathered in the collection created by J. Riveline (Laboratoire de Biominéralization et énvironnement sedimentaires, Université Pierre et Marie Curie, Paris) show biometric parameters (mean values of 715 µm high, 595 µm wide, isopolarity index of 115 and 8 convolutions) similar to the type material. Furthermore, most of the gyrogonites from the Paris Basin show a swollen apex and concave spiral cells whilst the presence of prominent apical nodules is not common.

Figures

FIG. 8.— Charophytes from the Artés and lateral south-western Formations,Ebro Basin:A-C, Lychnothamnus grambastii (Feist-Castel, 1971), Torre Casanova section; A, apical view, no. 80100 MGSCB, sample TC-9; B, lateral view, no. 80101 MGSCB, sample TC-9; C, basal view,no.80102 MGSCB,sample TC-9;D-F, Lychnothamnus vectensis (Groves,1926),Santpedor and Rubió sections;D, apical view, no. 80103 MGSCB, sample RB-3; E, oblicuous view, no. 80104 MGSCB, sample SP-18; F, lateral view, no. 80104 MGSCB, sample SP-18; G, basal view, no. 80105 MGSCB, sample SP-4; H-K, Lychnothamnus major (Grambast & Paul, 1965), Sarral section and El Talladell outcrop; H, apex, no. 80106 MGSCB, sample BO-1; I, lateral view, no. 80107 MGSCB, sample BO-1; J, lateral view, no. 80108 MGSCB, sample SA-19; K, basal view, no. 80109 MGSCB 09, sample SA-19; L-N, Nitellopsis (Tectochara) merianii (Al. Braun ex Unger, 1852), Vinaixa section; L, apical view, no. 80110 MGSCB, sample VI-5; M, lateral view, no. 80111 MGSCB, sample VI-5; N, basal view, no. 80112 MGSCB, sample VI-5. Scale bar: 500 µm.