Lepidocalix pulcher Termier and Termier, 1950a

Makhlouf, Yamouna, Lefebvre, Bertrand, Nardin, Elise, Nedjari, Ahmed & Paul, Christopher R. C., 2017, The diploporite blastozoan Lepidocalix pulcher from the Middle Ordovician of northern Algeria: Taxonomic revision and palaeoecological implications, Acta Palaeontologica Polonica 62 (2), pp. 299-310 : 303-307

Lepidocalix pulcher Termier and Termier, 1950a

Figs. 4–6 .

1950 Lepidocalix pulchrum sp. nov.; Termier and Termier 1950a: 26, pl. 8: 2, 3.

1959 Lepidocalix pulchrum Termier H. & G., 1950; Termier and Termier 1959: 89, 498.

1968? Lepidocalix pulchrus [sic] Termier and Termier, 1950a; Kesling 1968: 254, 143.

2011 Calix pulchra ( Termier and Termier, 1950a) ; Gutiérrez-Marco and Colmenar 2011: 190.

Type material: Lectotype (MUA. 1024020), a flattened theca showing the oral zone. Paralectotypes (MUA. 1023001, MUA. 1023002, MUA.

1024016, MUA. 1024021 and MUA. 1024022), by fragmentary sam-

ples.

Type locality: Zaouïa of Stita , Great Kabylia, northern Algeria .

Type horizon: Darriwilian, Middle Ordovician.

Emended diagnosis.— Calicinae with an elongate theca composed of abundant, thin, and small thecal plates organised in circlets. Primary plates bear up to three dipores, while secondary and tertiary plates, one tubercular diplopore. Relatively small and elongate peristome connected to two main ambulacral rays subdivided once laterally. Ambulacral rays and peristome covered by two series of polygonal cover plates. Periproct restricted to an anal pyramid composed of triangular plates. Slit-like hydropore located between the peristome and the periproct in the CD interray.

Description.—The theca is composed of small, numerous (hundreds), adjacent plates of various sizes, revealing three generations of plates ( Fig. 4 ). The largest preserved theca reaches 62 mm in diameter (MUA.1023002). Primary plates are pentagonal in shape, sometimes hexagonal with rounded corners. Each primary plate carries one central spine and sometimes one or two tubercles. Secondary and tertiary plates are smaller, hexagonal to irregularly polygonal. They sometimes bear one small tubercle (Fig. 5A 2). In larger specimens, primary plates are up to 3 mm wide and 4.5 mm long, while secondary and tertiary elements are up to 2 mm in diameter (MUA. 1023001). All plates are thin at their edges, less than 0.25 mm in thickness. Plates appear to be aligned to form continuous circlets reflecting three generations of circlets. Spines are narrow and elongated (up to 5 mm long). They have a large base, up to the width of the plate, and taper distally, becoming elliptical (no articulation of spines was observed). They are adorally orientated with their base located at the aboral side of the plate. Perpendicular canals can be observed within abraded tubercles and spines. Each secondary and tertiary plate bears one tubercle thinly covering one superficial diplopore. The pattern in the primary plates is more complex. Their spines shelter one internal diplopore, while their tubercles can cover one haplopore or two perpendicular but sinuous canals possibly connected to form a diplopore. Externally the pores can only be seen where the spines have been damaged. Specimens MUA.1024016 and MUA.1023002 confirm the presence of fine spiny ornament on the facetal plates around the ambulacral facets (Fig. 5B, C). The latter reach about 3 × 3 mm, are slightly concave and appear to have supported a single, robust ambulacral appendage, none of which is preserved.

The dipores consist of narrow paired canals about 0.2 mm in diameter (MUA.1023001B). Internally some openings increase in diameter as they reach the internal surface. In the lectotype, pores open externally in an oval tubercle (width 0.65–0.7 mm; length 0.8–0.9 mm) with individual pores about 0.35 mm in diameter. The tubercles apparently represent damaged spines. Specimen MUA.1024016 shows lateral views of some damaged spines that appear to have canals within them (Fig. 5B 1). The variability of the pores apparently depends on where the original spines were damaged (MUA.1024022; Fig. 5D).

The oral surface is slightly flattened at the top of the theca (MUA.1023002). Peristome is a wide, transversally elongated slit (5 mm wide), with two short ambulacra diverging from each extremity and ending in large obovate ambulacral facets ( Fig. 6A ). It is approximately 20 mm wide by 13 mm in the presumed anterior-posterior direction (MUA. 1024020A). Peristome is framed by eight plates Fig. 6A ): four circum-orals in radial position ( CO 1, CO 2,

CO 4, and CO 5) and four peri-orals in interradial position ( PO 1, PO 3, PO 4, and PO 6). The A ambulacrum is absent, thus leading to a four-fold ambulacral system. Ambulacral facets are deep and large (0.75 mm) recumbent on larger oral plates. Peristome is covered by two series of triangular to polygonal plates, and ambulacra, by one series of polygonal plates. The internal surface shows no trace of a central oral opening (mouth), while the oral plates show many dipores with no clear corresponding openings on the external surface (MUA. 1024020B; Fig. 6B ).

The periproct corresponds to a roundish anal pyramid composed of 7 smooth triangular plates (MUA.1023002A). It is about 6 × 3 mm, despite a slight crushing. Hydropore is a slit-like fold located in the CD interray across the PO 1– PO 6 suture. The gonopore and the aboral region are unknown.

Remarks.—The masculine of the Latin word for beautiful is pulcher not pulchrus . Calix is masculine, so we assume Lepidocalix will be too. Thus the correct form would be Lepidocalix pulcher Termier and Temier, 1950a . The subfamily Calicinae is characterized by a four-fold ambulacral system, as shown in Calix sedgwicki Rouault, 1851 ; Calix inornatus ( Meléndez, 1958) ; Glaphocystis globulus Chauvel, 1966 ; Sinocystis loczyi Reed, 1917 ; Sinocystis gigas ( Termier and Termier, 1950a) , and Phlyctocystis sp. (Chauvel, 1978). The ambulacral facets of Lepidocalix pulcher appear to have given rise to a single appendage or brachiole each. In contrast, in Calix sedgwicki Rouault, 1851 , each of the four ambulacral facets bears four brachioles. The presence of this four-fold ambulacral pattern combined with the possession of the typical thecal plating of Calicinae , both support the assignment of Lepidocalix to this subfamily.

The plates of Lepidocalix are very thin (0.25–0.3 mm thick), whereas most aristocystitids have plates over 1 mm thick (e.g., Calix ) and many over 2–3 mm (e.g., Pachycalix ). Their plates are very small and only have a maximum of 3 diplopores per plate, while most aristocystitids have several tens (20–30 at least) of diplopores in their largest plates. The plates bear very prominent spines over the diplopores. These spines reach 3 times as long as the plates are wide. Sinocystis has short tubercles over individual diplopores, but these are a fraction of one mm high and the plates are covered with the tubercles. “Spiny” plates in Calix are much thicker, the plates bear numerous diplopores often distributed all over the “spines”.

In general, these aristocystitids are characterized by a more elongate, ellipsoidal theca, composed of generational circlets of plates showing an ornamentation strongly linked to the development of the respiratory structures (Chauvel

Fig. 5. Photographs of latex casts of the diploporite blastozoan Lepidocalix pulcher Termier and Termier, 1950a ; Middle Ordovician, Stita, Algeria. → A. MUA. 1023001; general aspect of the theca, in lateral view (A 1); enlargement of external surface (A 2, turned 90° counter clock-wise), showing the central tubercles on the plates; enlargement of inner surface (A 3), showing the distribution of the diplopores and apparent imbrication of plates. B. MUA.

1024016; summit view of the theca (B 2), showing circlets of tessellate thecal plates; enlargement of the summit (B 3, turned 90° clockwise), composed of four ambulacral rays recumbent on ornamented facetal plates; enlargement of the right thecal periphery (B 1), showing tessellate plates ornamented with tubercles and long spines. C. MUA. 1023002; general outline of the theca (C 1); enlargement of the top of C 1 (C 2), showing the organisation of the peristome (Pe) and the periproct (AP). D. MUA. 1024022, showing some abraded spines revealing the diplopores. Scale bars 5 mm.

A

B 1 2 3 C 1 2 3

1966, 1980; Chauvel and Meléndez 1978; Kesling 1968). The general thecal shape of Lepidocalix is difficult to reconstruct, because of its preservation. The larger specimen (MUA. 1023002) shows a circular outline with a slightly flattened oral region. The specific plating organised in circlets leads us to suppose an original cylindrical shape of the theca ( Paul 1971; Frest et al. 2011). It could therefore be similar in thecal shape and plating to Calix and Phlyctocystis , both possessing a conical theca, composed of numerous circlets of three generations of plates (Chauvel 1978). Thecal plating in circlets is a diagnostic characteristic of the subfamily ( Chauvel 1966). However, it is more strongly expressed in all Calix species, and only in the aboral regions of the species of Sinocystis and Glaphocystis ( Chauvel 1966) . Ornamentation as spines and/or tubercles is also known in several species of Calix . However, these ornamentation features are usually restricted to the primary plates in the aboral part of the theca, as in Calix sedgwicki and Calix segaudi Termier and Termier, 1950b . In contrast, the outer surface of Calix inornatus is smooth, and without tubercles. All specimens of Lepidocalix studied here show spines and tubercles distributed all over the theca. A final major singularity of Lepidocalix among its subfamily is in grade, based on the presence of an extremely reduced number of dipores per thecal plate.

Termier and Termier (1950a) described imbricate thecal plating in Lepidocalix . However, new series of latex casts of their original material show tessellate sutures between primary and secondary/tertiary plates and no hollow on the external surface of the plates suggesting any plate overlapping (Fig. 5A). When buried, the spines caused the plates near the edge of the specimens to rotate slightly producing the apparently imbricate appearance of some plates, because these spines were initially at an oblique angle to the sediment surface ( Fig. 7). In the centre of the specimen, plates would not have rotated but simply been forced down onto the sediment surface by compaction. Nevertheless, the spines were not completely buried, so that in the centre of specimens they are truncated and often reveal the pore canals inside (similar hypothesis has been proposed for sphaeronitid diploporites; Bockelie 1984). So, the plates are usually still articulated and do not show any apparent imbrication. This appearance is considered here as a preservational artefact, due to the crushing of the theca and the subsequent slight rotation of the spiny plates. Therefore, we reject the hypothesis of imbricate plating in Lepidocalix .

Stratigrapic and geographic range.— Type locality and horizon only.

Figures

Fig. 4. Diploporite blastozoan Lepidocalix pulcher Termier and Termier, 1950a (MUA. 1023001); Middle Ordovician, Stita, Algeria. A. Photograph of latex cast of external mould showing spines, tubercles, and the appearance of imbricate plates. B. Camera lucida drawing, note three generations of plates. Scale bars 2 mm.

Fig. 6. Oral surface of the diploporite blastozoan Lepidocalix pulcher Termier and Termier, 1950a (MUA. 1024020); Middle Ordovician, Stita, Algeria. A. Four peri-orals (PO1, PO3, PO4, and PO6) between four circum-orals (CO1, CO2, CO4, and CO5), peristome partially covered by small subtriangular oral cover plates biseries, diplopore-bearing polygonal thecal plates immediately surrounding the peristome, hydropore over PO1 and PO6; in external view. B. Surface showing numerous diplopores. Photographs (A1, B1), coloured interpretations (A2, B2) of both surfaces illustrating names using circumorals and periorals (Paul 1973, 2017); in internal view. B–E ambulacral designations in Carpenter’s system. Scale bars 5 mm.