Cryptosepta nuda, Gretz & Lathuilière & Martini, 2015
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publication ID |
https://doi.org/ 10.4202/app.00012.2013 |
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persistent identifier |
https://treatment.plazi.org/id/03859812-FFDA-FFB8-FF1F-748FFC3F7E12 |
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treatment provided by |
Felipe |
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scientific name |
Cryptosepta nuda |
| status |
sp. nov. |
Cryptosepta nuda sp. nov.
Figs. 3 View Fig , 4 View Fig , 6 View Fig .
Etymology: From Latin nuda , nude, because the septa are so short that the tube seems nude.
Type material: Holotype: MHNG 2013-34 View Materials to MHNG 2013-37 View Materials ( Figs. 3A View Fig
1 View Fig
, A
2 View Fig
, B, D, 4B, C, E–G View Fig ); sample S6. Rubble of a Cryptosepta nuda colony. Corallites can be observed on both faces of the sample. Paratypes: MHNG 2013-38 to MHNG 2013-41 ( Figs. 3C, E View Fig , 4A, D View Fig ); sample MG 156. Two rubbles containing each a Cryptosepta nuda colony.
Type locality: Ucel , Ardèche, France .
Type horizon: Lower Hettangian (in an interval that could extend from the upper Psiloceras planorbis ammonite Zone to the lower Alsatites liasicus Zone ).
Material.— Type material only.
Diagnosis.—Phaceloid growth form. Corallites forming conical calices. Variable corallite wall thickness, which is proximally thick and distally thin. In transverse and longitudinal sections, the wall often has a corrugated aspect that produces an irregular corallite shape. The number of septa is low. In the more distal parts, the estimated number of septa ranges between 20 and 25. The septa are poorly developed as septal ridges along the inner side of the wall; they are irregular and randomly distributed but not distinct in the distal corallite parts. No visible symmetry. Budding lateral or possibly parricidal. No columella. Certain corallites display a distinct fine external epithecal layer separated from the massive thecal structure and occasionally a fine layer that covers the internal theca. Rare endothecal structures represented by large horizontal tabulae. They separate the corallite into distinct portions. A new septal apparatus grows at the upper surface of these tabulae.
Dimensions.—The different measured parameters of the holotype are shown in Fig. 5 View Fig , and their values are in Table 1. The holotype size is 18 cm length × 12.5 cm width.
Description.—Phaceloid growth form. The corallites are formed by thick walls that become thinner distally. The walls are irregular, thick and often have a corrugated aspect that produces in an irregular corallite shape. The original structure of the corallite walls are difficult to identify and the cathodoluminescence analyses did not permit to reveal the original microstructure. Nevertheless, in some cases, in natural light observations, fine fibre-like structures are visible ( Fig. 6 View Fig ), and the diagenesis likely affected in a different manner the distinct structures that originally formed the theca. For example, some corallites have a distinct fine external epithecal layer separated from the massive thecal structure and occasionally a fine layer that covers the internal theca.
Rejuvenescence phases are visible in longitudinal sections and induced more or less important calicinal aperture retractions. The radial elements are poorly developed and deeply hidden in the calices. Thus, the distal corallite portion has no septa and, in transverse sections, it appears as empty tubes. The septa develop on the pre-existent wall and are gradually inserted. In the proximal part, the number of septa is low, and in the more distal part, the estimated number of septa ranges between 20 and 25. In the transverse section, the septa are short, and the majority is thick. Thinner and longer septa were also observed, occasionally curved and rarely somewhat rhopaloid.
Budding is dominantly lateral; the new bud grows centrifugally at a wide angle from the outer side of the parental corallite wall, and it rapidly becomes quasi parallel to the mother corallite. Additionally, a case of possible parricidal budding could be considered ( Fig. 3E View Fig ). Nevertheless, it is difficult to distinguish it from rejuvenation. It is worth to note that in this case, two septa are elongated and are more or less involved in the budding process similar to as it is known in Intersmilia ( Melnikova and Roniewicz 1976) . In the longitudinal section, endothecal structures are rare, and they comprise large horizontal tabulae that separate the corallite into distinct portions. A new septal apparatus grows at their upper surface. Such tabulae are geometrically related to rejuvenation stages.
Remarks.— Cryptosepta gen. nov. exhibits plesiomorphic characters such as thick corallite wall developed before cryptic poorly developed septa. Though the wall microstructure is not well-preserved, such thickness is associated with poor septal development and suggests a pachythecalid wall (see Kołodziej et al. 2012 for a recent review on pachythecal corals), which is the predominant skeletal characteristic of Zardinophyllidae (=junior synonym Pachythecalidae Cuif, 1975 ). This family comprises additional colonial genera with phaceloid morphologies, including Pachydendron Cuif, 1975 , Pachysolenia Cuif, 1975 and Pachysmilia ( Melnikova, 1989) .Additionally, it comprises the solitary forms Pachythecalis Cuif, 1975 and Zardinophyllum Montanaro-Galitelli, 1975 . Among these genera, Cryptosepta is remarkable in its poorly developed septa ( Table 2).
Compared with Jurassic or Triassic pachythecal Amphiastreidae as redefined by Stolarski and Russo (2001), Cryptosepta does not comprise the two zonal endotheca (no marginarium). The corallite illustrated in Fig. 4C View Fig suggests that a pocket may open within the wall. However, we could not characterise the typical mode of growth in the Amphiastreidae “Taschenknospung” (pocket budding) as it is defined by Roniewicz and Stolarski (2001).
Compared with Intersmiliidae , Cryptosepta has a much thicker wall, which suggests that it is more related to Zardinophyllidae than Intersmiliidae . The rhythmic growth of tabulae in Intersmilia is also a significantly discriminating characteristic.
Zardinophyllids have a pachythecalid type wall that is comprised of radially oriented, equal-sized fibre fascicles and exhibits full microstructural independence between theca and septa. However, the observed specimens show strong recrystallisation, and the original structure of the corallite wall is difficult to identify. The distinct fine external epithecal layer separated from the massive thecal structure that is observed around certain corallites of Cryptosepta nuda ( Fig. 4F View Fig ) is similar to those described by Cuif (1975: 169, fig. 6b), Melnikova and Roniewicz (1976: 99, pl. 24: 2, 3) and in particular to those presented by Kołodziej et al. (2012: 315, fig. 17).
In their initial and juvenile stages, zardinophyllids typically exhibit strong bilateral symmetry with an enlarged primary septum; the adult stages often have quasi-radial symmetry. However, in Cryptosepta , the septa are often not clearly visible, and it was difficult to count the septa in the corallites. Therefore, it is also difficult to discern information about the symmetry.
Compared with the other Liassic genus Pachysmilia Melnikova, 1989 , Cryptosepta has shorter and thicker septa. Nevertheless, Pachysmilia and the Triassic solitary corals Pachythecalis Cuif, 1975 and Zardinophyllum Montanaro-Galitelli, 1975 all display the same distinctive lamellar layer observed in Cryptosepta , which covers the internal theca and septa base. The colonial Triassic coral Pachydendron Cuif, 1975 also has more developed septa.
Stratigraphic and geographic range. — Type locality and horizon only.
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