Linuparus bererensis Secrétan, 1964

Charbonnier, Sylvain, Garassino, Alessandro & Pasini, Giovanni, 2012, Revision of Mesozoic decapod crustaceans from Madagascar, Geodiversitas 34 (2), pp. 313-357 : 313-357

Linuparus bererensis Secrétan, 1964 ( Figs 19-22)

Linuparus bererensis Secrétan, 1964: 122-128 , pl. 8, fig. 1; pl. 11, figs 2-4; pl. 12, figs 1-5. — Collignon 1970b: 35. — Feldmann et al. 2007: 709, 710. — Schweitzer et al. 2010: 46.

Linuparus bererensis multispinosus Secrétan, 1964: 128- 130 , pl. 11, fig. 5. n. syn. — Collignon 1970b: 35.

HOLOTYPE. — MNHN.F. R 03916.

PARATYPES. — From the “Coupe de Ampolypoly-Antsirasira-Behamotra” (Lower Campanian): 2 specimens (gisement 324: MNHN.F. A33148 ); 1 specimen (gisement 320: MNHN.F. A33463 , Menabites boulei and Anapachydiscus arrialoorensis zone); 1 specimen (gisement 315: MNHN.F. A33075 ); 1 specimen (gisement 302: MNHN.F.A33136, Menabites boulei and Anapachydiscus arrialoorensis zone); Middle Campanian: 11 specimens (gisement 317: MNHN.F.A33168); 6 specimens (gisement 326: MNHN.F. R 03911, R 03918, A33117, A33125, A33134, A33140 , Pachydiscus grossouvrei zone); 2 specimens (gisement 327: MNHN.F. R 03915, A33147 , Pachydiscus grossouvrei zone).

From the “Coupe de Berere II” ( Lower Campanian ): 1 specimen (gisement 165: MNHN.F.A33199) ; 1 specimen (gisement 171: MNHN.F.A33158, Karapadites karapadensis zone) .

Paratypes from the “Coupe de Berere III” (Lower Campanian): 1 specimen (gisement 190: MNHN.F. R 03910, Anapachydiscus wittekindi and Eulopoceras jacobi zone); 1 specimen (gisement 206: MNHN.F. A33146 ); 1 specimen (gisement 184: MNHN.F.A33159).

From the “Coupe de Bevaho” (Lower Campanian): 3 specimens (gisement 261: MNHN.F. A33120 , A33157, Karapadites karapadensis zone).

From the “ Coupe de Ampamba-Antsirasira ” (Middle Campanian): 1 specimen (gisement 709, Karapadites karapadensis zone: MNHN.F.A33204) ; 4 specimens (gisement 723: MNHN.F. A33082 ) .

From the “Coupe de Andimaka” (Middle Campanian): 3 specimens (gisement 203: MNHN.F.A33202, A33122 , Pachydiscus grossouvrei zone).

From the “Coupe de Beantaly-Soromaraina” (Lower Santonian): 1 specimen (gisement 340: MNHN.F.A33208, Texanites oliveti zone).

All specimens are from Belo-sur-Tsiribihina, Menabe region, central Morondava Basin, Tulear Province.

TYPE LOCALITY. — Coupe de Ampolypoly-Antsirasira- Behamotra (gisement 326), Belo-sur-Tsiribihina, Menabe region, central Morondava Basin, Tulear Province.

TYPE AGE. — Middle Campanian ( Pachydiscus grossouvrei zone).

ADDITIONAL MATERIAL EXAMINED. — Type material of Linuparus bererensis multispinosus : holotype ( MNHN.F. R 03917, Coupe de Ampolypoly-Antsirasira- Behamotra, gisement 320, Menabites boulei and Anapachydiscus arrialoorensis zone, Lower Campanian); 4 paratypes ( MNHN.F. A33113 , Coupe de Ampolypoly-Antsirasira- Behamotra, gisement 328, Pachydiscus grossouvrei zone, middle Campanian); 1 paratype ( MNHN.F.A33206, Coupe de Andimaka, gisement 177, Pachydiscus grossouvrei zone, middle Campanian).

Unfigured material of Linuparus bererensis : 28 specimens from the Coupe de Ampolypoly-Antsirasira-Behamotra (gisement 326: MNHN.F. A33111 , A33123 , A33126, A33128, A33129, A33135, A33139 , A33141 , A33142 , A33143 , A33145 , A33150, A33179, A33192, A33196, A33197, A33472 , Pachydiscus grossouvrei zone, Middle Campanian); 1 specimen from the Coupe de Ankilizato (gisement 190: MNHN.F.A33127, Lower Campanian); 1 specimen from the Coupe de Ampamba-Antsirasira (gisement 709: MNHN.F. A33073 , Karapadites karapadensis zone, middle Campanian); 1 specimen from the Coupe de Berere II (gisement 169: MNHN.F.A33172, Karapadites karapadensis zone, Lower Campanian); 5 specimens from uncertain outcrop ( MNHN.F. A33144 , A33154, A33465 ).

All specimens are from Belo-sur-Tsiribihina, Menabe region, central Morondava Basin, Tulear Province.

STRATIGRAPHIC RANGE. — Early Santonian to Middle Campanian.

DIAGNOSIS. — Cephalothorax with cephalic region smaller than branchial one. Cephalic region with: 1) two very strong supraorbital teeth directed upwards with two posterior basal spines; 2) wide frontal region without rostrum; 3) two dorsal carinae converging forwards into one strong spine; 4) two well-developed semicircular dorso-lateral carinae and strongly serrated; 5) straight lateral carina well developed, strongly serrated with very strong antennal spine delimiting the ocular incision; and 6) straight, smooth ocular incision; branchial region with: 1) three carinae well developed and strongly serrated; and 2) posterior margin of the cervical groove marked by small spines; posterior margin with submarginal groove of equal width both medially and laterally; abdominal somites with terga bearing two median spines; subrectangular, very strong somite 6 with two lateral depressions forming a rounded central part bearing two median spiny lines as well as two lateral parts slightly carinate with one small proximal spine and one very strong distal spine; subrectangular telson with two weakly curved lateral depressions forming a small rounded central part with two small median spines, lateral margins with strong distal spine, inferior margin near-straight and denticulate.

DESCRIPTION

Cephalothorax subrectangular (holotype: CL = c. 75 mm, CH = c. 18 mm), subdivided by a very deep cervical groove into two regions: cephalic region (length c. 33 mm) smaller than branchial region (length c. 38 mm).

Cephalic region with two very strong supraorbital teeth directed upwards with two posterior basal spines, wide frontal region without rostrum, two dorsal spiny carinae (c. 4-5 spines) converging forwards into one strong spine, two semicircular dorso-lateral carinae well developed and strongly serrate (c. 5-8 spines), straight lateral carina well developed, strongly serrate (c. 4-8 spines) ending by very strong antennal spine delimiting the straight, smooth ocular incision.

Branchial region with three well-developed, strongly serrated carinae: median carina (c. 7-9 spines, sometimes second proximal spines doubled) and lateral carinae (c.14-15 spines); posterior margin of cervical groove marked by small spines; posterior margin with submarginal groove of equal width

(MNHN.F.R03911, Coupe de Ampolypoly-Antsirasira-Behamotra, gisement 326), ventral view; note triangular mandibles; E-H, complete abdomen (MNHN.F. A33146 , Coupe de Berere III, gisement 206), in dorsal (E), right (F) and detailed (G-H) views; note terga of somites 2-5 with two transverse grooves (E), pleurae of somites 2-5 with trifid ventral margin (G), subrectangular somite 6 with two lateral depressions forming a rounded central portion with two spiny crests (H); I-K, tail fan (MNHN.F.R03915, Coupe de Ampolypoly- Antsirasira-Behamotra,gisement 327),in left lateral,dorsal and right lateral views,respectively,note subrectangular telson and uropods with rounded inferior margin. Scale bars: A-F, H-K, 2 cm; G, 1 cm. Photographs by C. Lemzaouda (MNHN).

medially and laterally and with median dorsal spine; pleural region subdivided by one longitudinal groove extending from the posterior margin to the end of the cervical groove: inferior portion strongly tuberculate, superior portion near-smooth excepted for the proximal part which is mostly tuberculate; lateral margins with possible stridulatory apparatus (= appareil stridulant sensu Secrétan 1964), located just posterior to cervical groove; dorsal surface finely tuberculate.

Antennal articles very strong and spiny.

Proepistome with two median, aligned tubercles and one slight median depression.

Triangular mandibles well developed.

Abdomen slightly convergent distally, somite 1 highly reduced, somites 2-5 of equal size, somite 6 wider than others; terga of somites 2-5 with two transverse grooves: proximal groove slightly sinuous medially, distal groove triangular in shape anteriorly; one strong spine close to the median concavity of the proximal groove, one strong spine located at the top of the posterior margin; median spines of somites 1-4 directed forwards, median spines of somite 5 backwards; pleurae of somites 2-5 with two aligned tubercles and trifid ventral margin: proximal spine slightly directed forwards, median spine larger than the others, distal spine slightly directed backwards; subrectangular somite 6 very strong, with two lateral depressions forming a rounded central part bearing two median spiny lines and two lateral, weakly carinate portions with a single small proximal spine and one very strong distal spine; subrectangular telson with two weakly curved lateral depressions forming a small rounded central portion with two small median spines, lateral margins with strong distal spine, inferior margin almost straight and denticulated; uropodal exopod and endopod equal in length with smooth lateral margins and rounded inferior margin, basipodite of uropods subrectangular.

Pereiopods 1-5 elongate, flattened, slightly tuberculate, with spiny ventral margin. Pereiopod 2 longer than the others.

DISCUSSION

We adopt the diagnosis of Linuparus given by Bruce (1965). After re-examination of the Malagasy material studied by Secrétan (1964), we subscribe to her generic attribution. Secrétan (1964) erected the subspecies Linuparus bererensis multispinosus , based on the number (nine) of spines on the median carina and a more elongate cephalothorax. We question the validity of this subspecies for the following reasons: 1) in her description of L. bererensis ( Secrétan 1964: 124) , nine spines were recorded on the median carina, which fact leads to confusion in distinguishing these taxa; 2) the median carina in small and large specimens of L. bererensis shows a variable number of spines (ranging from 7 to 9); and 3) the ratio between cephalothoracic length (CL) and width (CW) measured on several specimens and the spine count on the median dorsal carina of L. bererensis and subspecies multispinosus do not show distinct values to confirm Secrétan’s proposition. The CL/ CW ratio of Malagasy specimens of Linuparus can be described as a linear model as has been observed for numerous fossil and extant crustaceans. Our plot diagram is relatively homogeneous and does not show any separate clusters that might be interpreted as distinct populations ( Fig. 21). Moreover, we stress that the majority of the most complete specimens bear seven spines (68%) while only 18% and 14% have eight and nine spines respectively. In conclusion, with the number of spines of the median carina being so variable in the specimens studied and with cephalothorax proportions relatively homogeneous, these features are best considered to represent intraspecific variation and/or sexual dimorphism. Thus, they are not real diagnostic characters on which to erect a subspecies. In addition, all material stems from the same outcrops.

Infraorder AXIIDEA de Saint Laurent, 1979 Family CTENOCHELIDAE Manning & Felder, 1991