Chiastozygus lamprostauros Aguado in Aguado, Company, O'Dogherty, Sandoval & Martinez

Plant Fossil Names Registry Number: PFN001011

Act LSID: urn:lsid:plantfossilnames.org:act:1011

Author: R. Aguado Merlo

Rank: species

Reference: Aguado, R., Company, M., O'Dogherty, L., Sandoval, J. & Martinez, M. (2022): New insights into the Barremian–lower Aptian calcareous nannofossils of the Mediterranean Tethys: Chronostratigraphic and paleobiogeographic implications. – Marine Micropaleontology 173: 102114 (24 pp.).

Page of description: 18

Illustrations or figures: fig. 14 AC–AP

Types

Original diagnosis/description

Diagnosis: Medium-sized (4.3–7.2 μm) normally elliptical Chiastozygus coccoliths with a narrow (~1.2 μm) rim. The relatively wide central area is covered by a diagonal cross whose arms are seen simple and brighter than the rim when the longitudinal direction is oriented at 45° under cross-polarized light microscopy (XPL).

Description: This species has an axial ratio ~1.4 and a relatively narrow rim which is dark and diffusely bicyclic under XPL. The diagonal cross spanning the central area have narrow (~0.5 μm) arms that show median lines and remain dark when the longitudinal direction is oriented at 0°. These arms are seen simple (without median lines) and bright under XPL when the longitudinal direction is oriented at 45°. The angle between the arms of the cross is greater (~105°) in the longitudinal direction than in the transverse direction (~75°). The arms of the diagonal cross are asymmetrical (slightly rotated) with respect to the axes of the ellipse. In some specimens, the diagonal cross supports the base of a distal stem.

Dimensions: lenght =4.3–7.2 (average 5.6) μm; width = 3.4–5.5 (average 4.2) μm; specimens measured: 20.

Holotype dimensions: length = 6.2 μm, width = 5.0 μm.

Etymology

From the Greek words ‘lampros’ meaning ‘bright’, and ‘stauros’ meaning ‘cross’, ‘saltire’, referring to the XPL image of this species.

Stratigraphy

Cretaceous, Lower Cretaceous, Barremian
Type level: Uppermost Barremian, sample X.HA-7 [DGF002] (NC6A nannofossil Zone; Martelites sarasini ammonite Zone).

Occurrence: Found, as a rare species, from the upper Barremian (upper part of the NC5E Zone of calcareous nannofossils, Gerhardtia provincialis Subzone of ammonites) to uppermost lower Aptian (NC7A Zone of calcareous nannofossils, Schackoina cabri Zone of planktonic foraminifera). Recorded in sections X.Cp2, X.F, X.F1, X.HA, X.Kv, X.Kv2, and Rambla Seca from the Subbetic domain in the Betic Cordillera (southern Spain).

Locality

Spain
Type locality: X.HA section (37.852 N; 2.589 W), Province of Granada, southeastern Spain.