Acutatheca rigauxi (Maillieux, 1909)

Mottequin, Bernard, 2008, New observations on Upper Devonian brachiopods from the Namur-Dinant Basin (Belgium), Geodiversitas 30 (3), pp. 455-537 : 502-512

Acutatheca rigauxi (Maillieux, 1909)

Cyrtina Rigauxi Maillieux, 1909a: 10 , 11, figs a-c.

Acutatheca rigauxi – Mottequin 2005a: 56-58, figs 3, 4, 9, table 1.

REMARKS

The species has been described in detail by Mottequin

(2005a). Acutatheca rigauxi occurs at the southern bor-

der of the Dinant Synclinorium (Neuville Formation).

FIG. 46.— Emanuella sp. ,Grands Breux Formation (Boussu-en-Fagne Representatives of the genus Acutatheca have been also Member): A -E, complete shell (IRScNB a12293), loc. BM-2003-7; collected within the Les Valisettes Formation (BM- F -J, complete shell (IRScNB a12292),loc.Bm-2003-10; A, F, ventral views; B, G, dorsal views; C, H, lateral views; D, I, posterior views; 2002-8; Philippeville Anticlinorium) as well as in the E, J, anterior views. Scale bar: A-E, 10 mm; F-J, 5 mm. Frasnian beds of the Lambermont Formation (BM- Upper Devonian brachiopods from Belgium

2002-1; northern border of the Dinant Synclinorium). Emanuella sp.

However, additional material is needed to confirm if (Figs 46; 47; Table 4)

they belong to A. rigauxi or to another species. MATERIAL EXAMINED. — BM-2003-7 (two articulated specimens); BM-2003-10 (two articulated specimens).

Superfamily AMBOCOELIOIDEA George, 1931 DESCRIPTION Family AMBOCOELIIDAE George, 1931 Shell small-sized, wider than long (width/length

Subfamily RHYNCHOSPIRIFERINAE Paulus, 1957 ratio: 1.02-1.23), ventribiconvex, rounded subpentagonal in outline; hinge line shorter than Genus Emanuella Grabau, 1923 greatest width (hinge line width/width ratio: 68- 0.74); widest at about mid-length; anterior margin

TYPE SPECIES. — Nucleospira takwanensis Kayser, 1883 , straight; anterior commissure rectimarginate to by original designation. slightly uniplicate.

Mottequin B.

Ventral valve clearly curved in lateral profile, es- text-fig. 4A) displays a cardinal process fixed to the pecially in the umbonal area; beak curved on the valve floor whereas this structure is apparently raised interarea; largest specimen displaying a shallow in the other representatives of the genus Emanuella , median depression near anterior margin; shoulder i.e. separated from the valve floor by a central apical lines concave; shoulder and apical angles between cavity (Crickmay 1967: pl. 2, figs 1, 4; Goldman & 99-119° and 90-105°, respectively; interarea 3.70- Mitchell 1990: figs 8, 9). Th is cavity is present in 6.25 times wider than high, concave, cata-apsacline; the specimen sectioned by Dürkoop (1970: pl. 56, fragments of deltidial plates observed. fig. 1) as well as in the one illustrated by Grabau Dorsal valve wider than long (width/dorsal valve (1931: fig. 46d); so, it is possible that the specimen length ratio: 1.40-1.46), rounded subtrapezoidal sectioned by Veevers belongs to another genus on to elliptic in outline; highest in its posterior part the basis of the layout of the cardinal process, unless curving progressively towards the front; no fold or this is only an intraspecific variation. The resolution groove; interarea linear, anacline, plane. of this question requires further study. In the middle part of the valves, distance between two successive growth lamellae between 2.4-2.7 mm DISTRIBUTION (more closely spaced near the commissure); spine Emanuella sp. occurs within the Grands Breux Forbases of variable diameter arranged in discontinuous mation (Boussu-en-Fagne Member) on the southern subradial alignments. flank of the Dinant Synclinorium. Similar speci- Ventral interior devoid of dental plates; teeth rela- mens originate from the top of the Les Valisettes tively strong; dental ridges strong; “pedicle collar” sensu Formation (Philippeville Anticlinorium). Veevers (1959a) (=“delthyrial plate” of Ma in Ma et al. 2006) dorsally directed, closing delthyrium apex. Dorsal interior with ctenophoridium separated Rhynchospiriferinae gen. and sp. indet. from the valve floor by a broad central apical cavity (Figs 48; 49; Table 4) (number of lamellae unknown); lateral apical cavities poorly filled in; dental sockets laterally connected MATERIAL EXAMINED. — BM-2003-9 (two articulated to the valve floor (intermediate-type dental sockets specimens, one ventral valve); JG-1996-1 (four articulated specimens). sensu Goldman & Mitchell [1990: 92, fig.17]); spiral cones not observed in the sectioned specimen. DESCRIPTION

Shell small-sized, longer than wide to wider than DISCUSSION long (width/length ratio: 0.96-1.23), ventribi- Some specimens identified as Crurithyris inflata convex, rounded subpentagonal in outline; hinge (Schnur,1853)by Vandercammen(1956:11-19) could line straight but shorter than greatest width (hinge be included with those identified here as Emanuella line width/width ratio: 0.61-0.72); widest at about sp. Th ey cannot be assigned to Crurithyris because the mid-length; anterior margin straight; anterior comlatter does not have well-developed crural plates as in missure rectimarginate (sulcus and fold absent). the transverse sections of Crurithyris urii (Fleming, Ventral valve regularly convex in lateral profile 1828) illustrated by Veevers (1959a: text-fig. 4B). (except in the beak area); dome-shaped in posterior They display the main characteristics of the genus view; flanks sloping moderately towards the lateral Emanuella itemised by Goldman & Mitchell (1990: commissure; beak strongly curved on the interarea; 90), but they do not display a narrow furrow at the umbo prominent; shoulder lines concave; shoulder dorsal valve.Th e lectotype of Emanuella takwanensis and apical angles between 96-102° and 77-86°, (Kayser,1883)has been designated by Veevers(1959a: respectively; interarea 2.85-5.26 times wider than 904) and illustrated by Dürkoop (1970:pl.17: 1a-e). high, concave, cata-apsacline to apsacline; delthy- Both authors presented transverse serial sections of rium partially closed by deltidial plates. specimens of this species, coming from Kayser’s collec- Dorsal valve wider than long (width/dorsal valve tion ( MB).Th e specimen sectioned by Veevers (1959a: length ratio: 1.23-1.53); highest posteriorly, curving

Upper Devonian brachiopods from Belgium progressively in anterior direction; interarea anacline, flat, less developed than the ventral one. Broad spine bases observed only in a single specimen; growth lamellae close to the commissure. Ventral interior devoid of dental plates; teeth simple, small; “pedicle collar” dorsally directed, closing the delthyrium apex (not represented in Fig. 49 ). Dorsal interior with cardinal process fixed to the valve floor; crural plates dorsomedially oriented, splitting off from the valve floor at some distance from their posterior margin; spiral cones laterally oriented, with at least three whorls. DISCUSSION By their micro-ornament and internal characters (sessile cardinal process, slight individualization of the crural plates...), these specimens differs clearly from those identified as Emanuella sp. Internally, they present similarities with the specimen sectioned by Veevers (1959a: text-fig. 4A) and assigned to Emanuella takwanensis such as the absence of central apical cavity as well as the layout of the dental sockets.However, they display an apparently bilobed cardinal process (defective preservation?). FIG. 48. — Rhynchospiriferinae gen. et sp. indet., complete shell

(IRScNB a12294), loc. BM-2003-9, Neuville Formation: A, ventral These specimens cannot be assigned to the genus view; B, dorsal view; C, lateral view; D, posterior view; E, anterior Crurispina Goldman & Mitchell, 1990 because they view. Scale bar: 5 mm. are devoid of ventral sulcus and their anterior commissure is rectimarginate, contrary to what occurs are not frequent in the investigated outcrops. They in the representatives of the genus Crurispina. seem more abundant in the carbonate mudmounds,

but the latter have not been studied in detail. Most DISTRIBUTION of the specimens previously identified as Echino- These unidentified Rhynchospiriferinae have been coelia rigauxi have been transferred to Dionacoelia collected at the top of the Neuville Formation secessus by Mottequin (2005a). (southern border of the Dinant Synclinorium).

REMARK Suborder DELTHYRIDINA Ivanova, 1972 Vandercammen (1956: 42) quoted the following Superfamily RETICULARIOIDEA Waagen, 1883 ambocoeliid species in the late Mid- to Late Frasnian Family RETICULARIIDAE Waagen, 1883 of southern Belgium (using stratigraphical notation Subfamily RHENOTHYRIDINAE of the time): Ambothyris infima (Whidborne, 1893) Gourvennec (in Carter et al. 1994) (“F2i”, “F2IIIb”, “F2IINb”), Crurithyris inflata Genus Warrenella Crickmay, 1953 (Schnur, 1853) (“F2i”, “F2j”, “F3”), Thomasaria gibbosa Vandercammen, 1956 (“F2i”, “F2j”, “F3”), Subgenus Warrenella (Warrenella) T. parallela Vandercammen, 1956 (“F2i”), Echino- Crickmay, 1953 coelia cf. incurva Cooper & Williams, 1935 (“F2j”), E. rigauxi (Maillieux, 1909a) (“F2j”), Emanuella TYPE SPECIES. — Warrenella eclectea Crickmay, 1953 , volhynica Kelus, 1939 (“F2i”, “F3”). Ambocoeliidae by monotypy.

Mottequin B.

A B C D E

Upper Devonian brachiopods from Belgium

Minatothyris maureri – Vandercammen 1957a (e.p.): 184; 1957b: 7-17, figs 1-9, pl. 2, figs 1-11, pl. 3, figs 1-13; 1959: 10.

Warrenella (sic) – Helsen & Bultynck 1992: table 3b.

FIG. 50. — Warrenella (Warrenella) aquaealbae n. sp., loc. Olloy, Neuville Formation, 575: A -E, complete shell (holotype IRScNB HOLOTYPE. — IRScNB a12299. a12299); F, internal mould of a complete shell (IRScNB a12300); A, F, ventral views; B, dorsal view; C, lateral view; D, posterior ETYMOLOGY. — Latin, aqua, water and alba, white, in view; E, anterior view. Scale bar: 10 mm. reference to the “Eau Blanche” whose channel is located close to the locus typicus.

Warrenella (Warrenella) aquaealbae n. sp. LOCALITY AND AGE. — Nismes railway section (BM-

(Figs 50-54) 2003-8), upper part of the Neuville Formation (Lower

Palmatolepis rhenana Zone ).

Spirifer pachyrhynchus – Maillieux 1909b (e.p.): 122, 136, 137 (only those from the “schistes de la Zone à DIAGNOSIS. — Shell medium-sized (maximum width: Spirifer pachyrhynchus ”); 1914: 90; 1922a (e.p.): 56; 45.6 mm; maximum length: 33.7 mm; maximum thick- 1922b (e.p.): 18; 1933: 81, non pl. 6, fig. 105 [copy ness: 28 mm), wider than long (width/length ratio: of Schnur (1853) = Warrenella (W.) eyryglossa (Schnur, 1.04-1.44), dorsibiconvex to ventribiconvex; sulcus 1851)]; 1940: 26; 1941a: 4. — Maillieux in Kaisin et al. and fold little or moderately developed; tongue wide, 1922: 23. — Maillieux in Asselberghs & Maillieux 1925: high, suboval to subtrapezoidal in outline; 4 or 5 growth 166. — Dumon 1929: 164, fig. 12; 1964: fig. 9. lamellae per mm.

Mottequin B.

A B C D

A B

Upper Devonian brachiopods from Belgium

C

Mottequin B.

N 0.608 N 0.556

20 20

N 0.530

10 10 10

0 T/W 0 Ws/W 0 Whl/W

0.45 0.55 0.65 0.75 0.4 0.5 0.6 0.7 0.4 0.5 0.6 0.7

MATERIAL EXAMINED. — BM-2003-8 (14 articulated gently to moderately towards lateral commissure; specimens, three ventral valves, one dorsal valve); JG- sulcus not originating at beak, wide (sulcus width/ 1995-5 (25 articulated specimens); Olloy 575 (45 ar- width ratio: 0.41-0.71), with bottom rounded to ticulated specimens).

flat at front, with blunt margins; tongue 1.03-

2.06 times wider than high, perpendicular to the

DESCRIPTION commissural plane or bent dorsally, trapezoidal to Shell medium-sized, wider than long (width/length suboval in outline; shoulder lines broken to conratio: 1.04-1.44), dorsibiconvex to ventribiconvex, cave; shoulder and apical angles between 118-145° oval in outline; hinge line shorter than greatest width and 92-114°, respectively; beak curved, overhang- (hinge line width/width ratio: 0.44-0.69); widest ing the interarea; interarea 3.45-7.69 wider than at mid-length; lateral margins rounded; anterior high, concave, well-delimited, cata-apsacline to margin variably excavated by the sulcus; anterior apsacline; delthyrium narrow, partially closed by margin uniplicate. deltididal plates.

Ventral valve regularly curved with an accentuation Dorsal valve wider than long (width/dorsal valve in the umbonal area in lateral profi le; flanks sloping length ratio: 1.31-1.47); dome-shaped in posterior

Upper Devonian brachiopods from Belgium view; highest at front or posteriorly (curving or 175), Biernat (1971: 156), Ludvigsen &Perry (1975: maintaining anteriorly); fold originating at about 64), Baliński (1979: 72), Brice (1982: 86), Drot midvalve or more anteriorly, with top rounded to (1982: 77) and Gourvennec (in Carter et al. [1994: flattened at the front (median depression rare on 352]). However, it was maintained by Struve (1970: the fold); interarea flat, orthocline, linear. 539, 540, 1992: 572). Warrenella (W.) aquaealbae Radial ornamentation absent although some n. sp.has been misidentified as W. (W.) maureri . The specimens display slightly undulose anterolateral latter is conspecific with W. (W.) concentrica (Schnur, commissure; 4 or 5 growth lamellae per mm with 1851), but can be distinguished at a subspecific level spine bases (Vandercammen 1957b: 9, text-fig. 4, by biostatistics according to Struve (1970: 539). Afpl. 3, fig. 12). ter Scupin (1900: 245), Holzapfel’s species should Ventral interior with dental plates intrasinal, be restricted to the “Stringocephalenkalk” while slightly divergent, thin, with length corresponding W. (W.) concentrica is an Eifelian species (Struve more or less to the third of the unrolled length of 1970: table 11). However, W. (W.) maureri has not the valve (measured on the internal mould); large been revised recently. Warrenella (W.) aquaealbae specimens with umbonal callus produced by thick- n. sp.differs from W. (W.) eyryglossa (Schnur, 1851) ening of dental plates from their internal face; teeth by its larger size, its narrow hinge line (hinge line small, simple; central apical cavity poorly filled in, width/width ratio: 0.44-0.69 vs 0.64-0.76 for the except for the large specimens; lateral apical cavities type material of the German species according to poorly filled in; muscle field diamond-shaped, not Vandercammen’s [1957a: 184] measurements), the excavated, divided by a myophragm (muscle scars absence of foraminate deltidium, a less well-defined obtained by calcining specimens are insufficiently sulcus, a less curved beak and a ventral muscle field well-displayed for detailed description). not excavated (see Vandercammen [1957a: pl. 1, Dorsal interior with ctenophoridium consisting fig 10, pl. 3, fig. 14]). The internal characters of of parallel thickened plates whose distal extremi- W. (W.) eyryglossa from the Eifel are not known in ties divided generally in two or three; crural plates detail because Vandercammen (1957a) used Belgian short, converging towards the plane of symme- specimens assigned to that species to illustrate using try but not attaining the valve floor; myophragm serial section its internal morphology. Warrenella prominent; large specimens with muscle field de- (W.) aquaealbae n. sp. is distinguished from W. (W.) limited laterally by two prominent curved ridges; concentrica (Schnur, 1851) by its proportionally spiral cones ventrolaterally oriented, comprising wider sulcus (sulcus width/width ratio: 0.41-0.71 vs at least 10 whorls. 0.34-0.55 for Schnur’s species according to Struve

[1970: 541]), a tongue more developed in height, DISCUSSION and a lower maximum size. After study of specimens In southern Belgium,this species was frequently misi- labelled Spirifer maureri from the “Massenkalken der dentified as Spirifer pachyrhynchus de Verneuil, 1845 Frettermühle und Bilveringser ” housed at the ULP whose type material originating from the Ural has and probably belonging to Holzapfel’s collections, been revised by Vandercammen (1959a: 2-10, pl. 1, it is clear that W. (W.) aquaealbae n. sp. differs from figs 1-4) and assigned by him to Emanuella Grabau , W. (W.) maureri (Holzapfel, 1895) by its smaller 1923 ( Ambocoeliidae ).According to Vandercammen size, a sulcus more defined at the front and a more (1957b: 17), in Belgium, Spirifer pachyrhynchus de developed tongue. Warrenella (W.) aquaealbae n. sp. Verneuil, 1845 would encompass both following is distinguished from W. (W.) laevis ( Hall, 1843a) species: Minatothyris eyryglossus (Schnur, 1851) and by its greater size, the absence of costae close to M.maureri (Holzapfel, 1895) .The genus Minatothyris the anterior margin and by its ventral muscle field Vandercammen, 1957 (type species: Spirifer eyryglos- which is not excavated. Warrenella (W.) aquaealbae sus Schnur, 1851) has been placed in synonymy with n. sp.is separated from W. (W.) eclectea Crickmay , Warrenella (Warrenella) Crickmay, 1953 by several 1953 by its greater size, a less defined sulcus and a authors, e.g., Pitrat (1965: H721), Johnson (1966: more prominent dorsal myophragm [see Crickmay

Mottequin B.

as well as a more inflated dorsal valve. Furthermore, the filling of the lateral and central apical cavities is clearly less developed within the latter.

DISTRIBUTION

Warrenella (W.) aquaealbae n. sp. occurs in the upper part of the Neuville Formation as well as the extreme base of the Matagne Formation on the southern flank of the Dinant Synclinorium. Incomplete valves collected within the Les Valisettes Formation (Philippeville Anticlinorium) have been assigned to Warrenella (W.) sp.

Figures

FIG. 49. — Transverse serial sections of Rhynchospiriferinae gen. et sp. indet. (IRScNB a12296), loc. BM-2003-9, Neuville Formation. Numbers refer to distances in mm from the top of the ventral umbo. Scale bars: 2.5 mm.