Regulaecystis testudineus, Nardin & Bohatý, 2013

Nardin, Elise & Bohatý, Jan, 2013, A new pleurocystitid blastozoan from the Middle Devonian of the Eifel (Germany) and its phylogenetic importance, Acta Palaeontologica Polonica 58 (3), pp. 533-544 : 535-538

Regulaecystis testudineus sp. nov.

Figs. 2 , 3 .

1997 Crinoide sp. indet B.; Hauser 1997: 15, 179–180, pl. 75: 4, 5.

2001 Crinoide sp. indet B. =?Cystoidea; Hauser 2001: 151.

2010 Cystoidee sp. indet. aff. Caryocrinites sp. ; Hauser 2010: 19, figs. 47a, b.

2010 Caryocrinus [sic] ornatus −Formenkreis.; Hauser 2010: 19, figs. 47a, b.

2010 Cystoidea sp. indet. aff. Caryocrinites ornatus Say, 1825 Formenkreis ; Hauser 2010: 41, pl. 8: 8–10.

Etymology: From Latin testudineus , turtle−like; after the shape of the theca in lifetime posture.

Type material: Holotype GIK−2276 , incomplete theca showing most of the abanal face connected to the proximal stem ( Figs. 2E , 3B ) ; Paratype GIK−2277 , incomplete theca showing most of the plating of the thecal faces, the oral area and the insertion of the two brachioles ( Figs. 2A , 3A ) ; Paratype GIK−2278 , partial theca showing details of the abanal face ornamentation and of the stem insertion ( Figs. 2D , 3C ) .

Type locality: Locality 3, “Schurf 3” (S Brühlborn), Prüm Syncline, Eifel (Rhenish Massif, Germany) .

Type horizon: Tortodus kockelianus Conodont Zone, Eifelian, Middle Devonian.

Remarks.—The privately published monographs of Hauser (1997, 2001, 2010) figuring specimens now identified as Regulaecystis testudineus sp. nov. contained misinterpretations. Striking in this context are his interpretations of the figured cystoids as “cupressocrinid or stylocrinid like crinoids” (1997: 179–180) and as Caryocrinus [sic!] ornatus (2010: 19). These monographs are given no further consideration herein.

Additional material.—One incomplete theca connected with an incomplete proximal stem, one incomplete theca showing the oral region, both housed in private collection (non−figured), eight isolated plates and twelve stems (GIK−2279–2280).

Diagnosis.—A species of Regulaecystis with a strongly inflated theca and a rhombic pectinirhomb at L3/L4 suture; plate ornament as granules and prominent radiating ridges; B1 restricted to the anal face; flanges of proximal columnals ornamented with granules.

http://dx.doi.org/10.4202/app.2011.0116

Description.—Approximate thecal size is up to 22 mm in length and up to 18 mm in width, based on the combination of two specimens (GIK−2276, GIK−2277). Thecal outline is broadly trapezoidal characterised by a shoulder−angle circa 45 ° (sensu Bather 1913) without aboral thecal lobes ( Fig. 2E 2 ). The abanal face of the theca is strongly inflated leading to a probable subvertical orientation of the single pectinirhomb ( Fig. 2A 3 , D 1, E 1 ). Thecal margins are slightly curved due to the flattened fluted fringe ( Fig. 2A 1 , A 2, E 2 ). Periproct is large, aborally rectangular without anal lobe.

The abanal and anal faces are composed of 16 and 12 plates, respectively. Periproct is surrounded by six plates (B1, B4, IL4, IL5, L1, L4), and the stem insertion, by five plates (four basals and IL5). Thecal plates are up to 0.55 mm thick in their edge and to 0.75 mm when ridged (GIK−2278, GIK−2280–2281).

Basals are unequal and localised in the stem insertion area. B2 and B3 are pentagonal with a wide base on the abanal face ( Figs. 2D 1 , 3C ). B1 is small quadrangular in shape, and mostly restricted to the anal face ( Fig. 2D 3 ). B4 seems to be fused with IL4, forming the posterior left corner of the anal face ( Fig. 3A 1 ). Infralateral circlet is composed of five large plates disposed in a broad arc across the abanal face. IL1, IL2 and IL3 are confined on the abanal face ( Fig. 3A 1 ). IL2 is large, hexagonal, and located along the thecal midline. IL1 and IL3 are smaller, pentagonal and deformed due to the curvature of the abanal face ( Fig. 2D 2 ). The medium−sized IL4 and IL5 straddle the posterior thecal edges, forming the left and the right corner of the abanal face, respectively ( Fig. 3A 1, B 1 ). Laterals are unequal in size and shape. Four laterals are placed in a broad arc across the abanal face. L2 and L3 are medium−sized and hexagonal.

http://dx.doi.org/10.4202/app.2011.0116

The large and elongate L1 and L4 form the thecal margins. They are characterised by a flattened fringe bearing beaded ridges continuously with the subjacent infralaterals ( Fig. 2A, B, F, H ). L5 is relatively small, possibly located above the L1–L4 junction. Radial plates are not aligned in a circlet. R2 and R3 are large, pentagonal and restricted on the abanal face. R1 and R4 form the right and left oral edge of the theca, respectively. R5 is small and localised transversally between L4 and R4 ( Fig. 2A 3 ). Oral plates are no completely preserved on the available specimens. On the abanal face, O1 bears the slit−like hydropore and the elliptical gonopore with the partially preserved elongate plates interpreted as L5 ( Figs. 2A 4 , 3A 2 ). O1 is pentagonal, transversally elongate surrounding the peristomial opening.

Ornamentation is highly variable. Theca is at least granulated with prominent umbones and sometimes bears sharp radial ridges. When present on the abanal face, ridges radiate from the umbones to join the middle of the plate edges. They define rhomb−like areas continuously from the basal to the lateral circlets and within each circlet. GIK−2277 and GIK−2278 have granules and few narrow radial ridges formed by the incomplete coalescence of the granules ( Fig. 2D 1 ). The rest of the non−weathered material exhibits relatively thick granules with sharp primary ridges (GIK−2276; Figs. 2E 1 , 3B 2 ). Thecal margins are relatively flat and strengthened by multiple beaded ridges.

A single conjunct pectinirhomb with confluent dichopores (sensu Paul 1968) occurs between L3 and L4. The pectinirhomb contains an estimated maximum of 20 slits ( Fig. 2A 4 , B). It is sunk within prominent vestibule rims (L/W ratio about 1.25), leading to the absence of an umbo on L3. Silts are partially lost on the L3 half−rhomb, probably covered by stereom ( Fig. 3A 1 ).

Uniserial brachiolar plates are stout and triangular in transversal section. They internally show one relatively deep central groove and two small lateral facets, interpreted as serving for the articulation of the cover plates.

Periproctal membrane is poorly preserved, probably composed of numerous smooth polygonal platelets, up to 0.7 mm across ( Fig. 3A 2 ). Anal pyramid is unknown.

No stem is completely preserved. The short proximal part is plated by circa 20 thin holomeric pairs of inner and outer columnals ( Fig. 2C, E 2 ). The maximal length of the preserved stems is about 18 mm (GIK−2276). It tapers from 4.2 to 2.1mm in diameter (GIK−2276) or from 5.4 to 3.5 mm for the longest preserved isolated stem (GIK−2281). The flanges of the outer columnals are up to 0.7 mm thick and ornamented by beaded longitudinal ridges or isolated granules ( Fig. 2E 3 ). The distal part seems to be composed of narrow barrel−shaped and ornamented holomeric plates ( Fig. 2E 2 ).

Discussion.—Despite their incomplete preservation, the combination of the features of the different specimens allows the reconstruction of the complete morphology. Within the genus Regulaecystis , R. pleurocystoides from the Lower Devonian Hunsrückschiefer is similar to R. testudineus sp. nov. in its angular thecal outline. However, it clearly differs by having a more flattened theca, a longer and unornamented proximal stem and a simple network of three primary ridges, two across the infralateral circlet and one on L2 (SMF−HS−424, MB−E−1853). The flattening is partly due to the mode of preservation in the compressed mudstone of the Hunsrückschiefer. Nevertheless, the consistency of the thecal framework could suggest that the theca was strongly flattened before the fossilisation process.

Regulaecystis testudineus resembles R. inconstans Paul, 1984 from the late Ordovician of Wales and England. Both species show a trapezoidal thecal outline, relatively thick thecal plates, and a complex granulate and reticulate ornamentation on the abanal thecal face and granules on the proximal outer columnals. However, they distinctly differ on the position of B1 (crossing to the thecal faces in R. inconstans ), the inflation of the theca, the relative dimensions and the number of the elements in the proximal stem, and on the pectinirhomb, which is highly compressed and symmetrical with few slits in R. inconstans (GSM−ZI−9227).

The isolated elements attributed to Pleurocystitidae gen. et sp. indet A and B Prokop and Petr, 2004, from the Loděnice Formation (Pragian, Early Devonian) of the Barrandian area (Bohemian Massif, Czech Republic) show morphological features similar to R. testudineus . They differ on the size of the pectinirhomb, the size of the plates and the strength of the ornamentation.

Stratigraphic and geographic range.—Nims Member of the Junkerberg Formation, Eifelian (Middle Devonian; Tortodus kockelianus Conodont Zone ) from the Prüm Syncline, Eifel (Rhenish Massif, Germany).

Pleurocystitidae gen. et sp. indet. C

Fig. 4 .

1932 Regulaecystis pleurocystoides ; Dehm 1632: 90.

Material.— Two specimens ( SMF−HS−420 , SMF−HS−422 ) showing the anal and abanal faces, respectively, from Hunsrückschiefer ( lower Emsian , Early Devonian ) of Bundenbach (Rhenish Massif, Germany) .

Description.—Theca is flattened and strongly pear−shaped in outline. Posterior area is circular with thecal lobes, surrounded by a raised flattened flange. Anterior area is elongate and trapezoidal. Abanal face is partly preserved in SMF−HS−422 ( Fig. 4A ). Basals are pentagonal. B2 and B3 are joining in the thecal midline and surround the stem insertion. B4 is more elongate and form the left posterior thecal edge. B1 is smaller, crossing the thecal periphery at the right thecal angle. Five infralaterals are organised in a broad arch transversally to the abanal face and bear the raised flat rim. IL4 and IL5 compose the right and the left thecal periphery, respectively. IL1 and IL2 are large and hexagonal. Only two laterals (L2 and L3) are partially preserved on SMF−HS−422. Ornamentation is reduced to few prominent ridges, stretching from the stem insertion to IL5, IL1 and IL3, and from IL2 to the two preserved laterals. The circular periproct area is at

Figures

Fig. 2. Pleurocystitid blastozoan Regulaecystis testudineus sp. nov., Nims Member of the Junkerberg Formation (Eifelian, Middle Devonian), Prüm Syncline (Rhenish Massif, Germany). A. Paratype GIK−2277, lateral view showing the flattened thecal flange and the rounded shape of the theca (A1), dorsal view showing the arched organisation of the plates (A2), lateral view showing the single pectinirhomb located at L3/L4 suture (A3), ventral view showing the organisation of the oral area (A4). B. Isolated plate GIK−2280, showing the slits of the pectinirhomb. C. Pluricolumnals adjacent to a reversed basal plate GIK−2279, showing the typical alternation of external and internal columnal in the proximal stem of the glyptocystitids. D. Paratype GIK−2278, dorsal view of the theca showing the reticulate ornamentation (D1), lateral view showing the intercalation of the circlets of plates (D2), aboral view showing the stem insertion and the organisation of the basals (D3). E. Holotype GIK−2276, lateral view showing the flattening of the theca, and the strong ornamentation (E1), ventral view showing the ornamentation at the margin of the theca and the elongate proximal portion and the thin ornamented distal portion of the stem (E2), and oblique dorsal view on the stem insertion and basal plates (E3). Scale bars 10 mm.

Fig. 3. Interpretative camera lucida drawings of the pleurocystitid blastozoan Regulaecystis testudineus sp. nov., Nims Member of the Junkerberg Formation (Eifelian, Middle Devonian), Prüm Syncline (Rhenish Massif, Germany). A. Paratype GIK−2277, abanal face showing the plate names (A1) and anal face showing the shape of the periproct and the organisation of the primary opening area (A2). B. Holotype GIK−2276, anal face showing the insertion of the ornamented stem (B1) and lateral view showing the strengthening of the thecal margins due to strong ornamentation in thick ridges and thick granules (B2). C. Abanal face of the paratype GIK−2278 showing the dense granulation. Cup and isolated plates of Stylocrinus tabulatus (Goldfuss, 1839) are preserved in the anal face. Plate names abbreviations follow Kesling (1967). Scale bars 5 mm.

Fig. 1. Geographical location of the fossiliferous sites near Prüm, Eifel (Rhenish Massif, Germany).

Fig. 4. Pleurocystitida gen. et sp. indet. C from Hunsrückschiefer (Emsian, Lower Devonian), Bundenbach (Rhenish Massif, Germany). A. SMF−HS− 422, abanal face. B. SMF−HS−420, anal face. Scale bars 10 mm.