Hoploparia collignoni ( Van Straelen, 1949 )

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

Hoploparia collignoni ( Van Straelen, 1949) ( Figs 13-16)

Palaeohomarus collignoni Van Straelen in Collignon, 1949: 99, pl. 21, figs 8-10.

Hoploparia collignoni – Secrétan 1964: 98-102, pl. 6, fig. 1; pl. 8, figs 2- 3; pl. 9, figs 5-10; pl. 10, fig. 1. — Bishop 1985: 613. — Aguirre Urreta 1989: 522, 524, 526. — Karasawa 2000: 235. — Tshudy & Sorhannus 2003: 709. — Kato & Karasawa 2006: 339. — Feldmann et al. 2007: 707. — Garassino et al. 2009: 89. — Schweitzer et al. 2010: 28.

Hoploparia intermedia Secrétan, 1964: 102-104 , pl. 4, figs 6-10; pl. 9, fig. 11. n. syn. — Bishop 1985: 613. — Aguirre Urreta 1989: 526. — Tshudy & Sorhannus 2003: 709. — Feldmann et al. 2007: 707. — Karasawa et al. 2008: 105. — Garassino et al. 2009: 89. — Schweitzer et al. 2010: 29.

Hoploparia sculpta Secrétan, 1964: 105-109 , pl. 4, fig. 11; pl. 9, figs 1-4, 12; pl. 10, figs 2, 5-9. n. syn. — Aguirre Urreta 1989: 524, 526, 529. — Tshudy & Sorhannus 2003: 709. — Feldmann et al. 2007: 707. — Hoploparia sculpta Secrétan in Garassino et al. 2009: 89. — Schweitzer et al. 2010: 30.

Hoploparia sculptata [sic] – Bishop 1985: 613.

HOLOTYPE. — A near-complete cephalothorax, see Van Straelen 1949: pl. 21, fig. 8.

PARATYPES. — Figured paratypes (2 complete propodi, pl. 21, figs 9, 10 in Van Straelen 1949).

Unfigured paratypes (1 small cephalothorax, 7 propodi, 1 dactylus, 1 fragment of pereiopod). All type specimens were deposited in the collections of the École nationale supérieure des Mines de Paris and they are now housed in the collections of the Université Claude Bernard Lyon 1 ( France). We did not examine these specimens.

TYPE LOCALITY. — Ambarimaninga, Sitampiky region, eastern Mahavavy River, southern Mahajanga Basin, Mahajanga Province.

TYPE AGE. — Middle Albian ( Lemuroceras spathi and Brancoceras besairiei zone).

ADDITIONAL MATERIAL EXAMINED. — Type material of Hoploparia sculpta : 4 syntypes ( MNHN.F. R 03948, R 03950, A31664, Befamonto, gisement 42, Douvilleiceras inaequinodum zone, Lower Albian); 24 syntypes ( MNHN.F. R 03947, R 03952, R 03953, R 03954, R 03955, A31665, Malandiandro, gisement 46, Douvilleiceras inaequinodum zone, Lower Albian).

Type material of Hoploparia intermedia : 2 syntypes ( MNHN.F. R 03938, A31662 , Befamonto, gisement 42, Douvilleiceras inaequinodum zone, Lower Albian); 17 syntypes ( MNHN.F. R 03936, R 03937, A31663 , Malandiandro, gisement 46, Douvilleiceras inaequinodum zone, lower Albian).

Figured material of Hoploparia collignoni by Secrétan (1964): 7 specimens ( MNHN.F. R 03940, R 03941, R 03942, R 03943, R 03944, R 03945, R 03946; Malandiandro, gisement 46, Douvilleiceras inaequinodum zone, Lower Albian). Unfigured material of Hoploparia collignoni : 194 specimens ( MNHN.F.A33152, A33210, A33211, A33212, A33213, A33214, A33224 , A33340, A33349, A33355, A33357, A33462 , Malandiandro, gisement 46, Douvilleiceras inaequinodum zone, Lower Albian); 2 specimens ( MNHN.F.A33333, A33348, Befamonto, gisement 42, Douvilleiceras inaequinodum zone, Lower Albian); 10 specimens ( MNHN.F.A33334, Ambarimaninga, gisement 38, Lemuroceras spathi and Brancoceras besairiei zone, Middle Albian); 10 specimens ( MNHN.F.A33341, Ambanjabe, gisement 45); 16 specimens lacking locality data ( MNHN.F. A33076 , A33227, A33335, A33336, A33339, A33363 , A33412, A33413, A33414 , A33415, A33416). All material originates from the Sitampiky area, eastern Mahavavy River, southern Mahajanga Basin, Mahajanga Province.

STRATIGRAPHIC RANGE. — Early to Middle Albian.

EMENDED DIAGNOSIS. — Cephalothorax with postcervical groove very deep up to the mid-height and very weak ventrally not really joining the hepatic groove; cervical groove deep starting at mid-height and joining the antennal groove; hepatic groove weak; branchiocardiac and inferior grooves absent; weak longitudinal carina, parallel to the dorsal margin and located between the posterior margin and the postcervical groove; gastric region with one well-developed spine; antennal region with tuberculate antennal carina; rostrum dorsally flat with rounded distal extremity, flanked by two smooth lateral carinae; one strong well-developed basal spine; uropodal exopod with diaresis (modified after Van Straelen 1949).

DESCRIPTION

Cephalothorax subcylindrical (CL = c. 46 mm, CH = c. 26 mm); rostrum very elongate, dorsally flat with rounded distal extremity, smooth margins and flanked by two smooth lateral carinae; one strong, well-developed basal spine; ocular incision of slight depth, delimited ventrally by the antennal spine; gastric region not delimited by the cervical groove, bearing one spine located in the centre of the ocular incision; antennal region well delimited by the cervical and antennal grooves, bearing one single postantennal spine aligned with the tuberculate antennal carina distally prolonged by the antennal spine; deep cervical groove, starting at mid-height and joining the antennal groove; postcervical groove straight, intercepting dorsal margin at an angle of c. 90°: it starts very deep in the centre of the dorsal

Charbonnier S. et al.

margin up to mid-height, after becoming very weak, not really joining the weak and rounded hepatic groove; weak longitudinal branchial carina, parallel to the dorsal margin and located between the posterior margin and the postcervical groove; posterior margin slightly sinuous with a thin marginal carina; ornament: branchial region smooth, cardiac, gastric, and antennal regions finely tuberculate.

Abdomen with subrectangular somites; somites 1 and 6 smaller than others; somites 2-5 of uniform length; two different types of ornament on abdomen: 1) somites 1-6 with terga and pleurae completely smooth; and 2) somite 1 completely smooth, somites 2-5 with two pairs of dorsally aligned tubercles, somite 6 with dorsal surface uniformly tuberculate; pleurae 2 and 3 with two proximal tubercles; pleurae 4 and 5 with a single proximal tubercle; pleura 6 with one median tubercle. Two different kinds of telson: one with dorsal surface completely smooth and the other with two median tubercles. Uropods fragmentary, exopod with distal diaresis bearing small spines on the upper margin.

Pereiopods fragmentary, only the propodi are well preserved; all are elongate, truncated conical, without apparent heterochely; specimen MNHN.F. R 03941 shows ventrally two chelipedes associated with the carapace ; two types of ornament occur on the lateral margins of chelipeds: 1) outer margin reinforced by a slightly tuberculate carina, inner margin by a carina of two rows of aligned strong spines; and 2) outer margin reinforced by a carina of two rows of aligned small spines, inner margin reinforced by a carina of two rows of aligned, strong spines; specimen MNHN.F. R 03941 bears propodi of the first type .

DISCUSSION

We adopt the generic features outlined by Feldmann et al. (2007) for Hoploparia , and subscribe to Secrétan’s (1964) assignment of the Malagasy material to it. Secrétan (1964) distinguished Hoploparia collignoni from H. sculpta and H. intermedia principally by: 1) the fact that cephalothoracic grooves were more or less well marked; and 2) the occurrence of different ornament of the inner and outer margins of the propodus and of the abdominal somites. However, we question the validity of Secretan’s (1964) species for the following reasons: 1) all specimens of the three species come from the same outcrops; 2) the configuration of the cephalic grooves are quite similar in all three species, and also the location of the different spines on the gastric and antennal regions are similar; and 3) the propodus presents the same ornament of the inner and outer margins in these three species, irrespective of propodus size.

For these three reasons and also in view of the incomplete preservation of material of H. sculpta and H. intermedia , we here refer specimens assigned to those species to H. collignoni . Moreover, the differences observed in the ornament of the abdominal somites and of the propodus could either represent intraspecific variation and/or sexual dimorphism ( Fig. 16 ). However, the specimens studied are not complete enough to be able to determine which of these interpretations is correct.

Figures

FIG. 16. — Line drawings of Hoploparia collignoni (Van Straelen, 1949), by F. Fogliazza, lateral views. Note differences in ornament of abdominal somites and first propodus that may be linked either to intraspecific variation or to sexual dimorphism.