Carpopenaeus garassinoi Charbonnier, 2012

Petit, Gilles & Charbonnier, Sylvain, 2012, Fossil sponge gemmules, epibionts of Carpopenaeus garassinoi n. sp. (Crustacea, Decapoda) from the Sahel Alma Lagerstätte (Late Cretaceous, Lebanon), Geodiversitas 34 (2), pp. 359-372 : 362-364

Carpopenaeus garassinoi Charbonnier n. sp. ( Fig. 1)

TYPE MATERIAL. — Holotype ( MNHN.F. A33532 , collection Arambourg).

TYPE LOCALITY. — Sahel Alma Lagerstätte (c. 20 km northeast of Beirut), Lebanon.

TYPE HORIZON. — Late Cretaceous sublithographic limestones from the Sahel Alma quarry (Late Santonian after Ejel & Dubertret [1966]).

ETYMOLOGY. — In honor of Dr. Alessandro Garassino (Museo Civico di Storia Naturale di Milano, Italy), a specialist in the palaeontology of decapod crustaceans.

STUDIED MATERIAL. — Only the holotype is currently known.

OCCURENCES. — Known only from the type locality.

DIAGNOSIS. — Large species of Carpopenaeus ; rostrum very elongated, curved upward distally, with four basal suprarostral spines, one median suprarostral spine, one median subrostral spine and three distal spines; third maxilliped well-developed, with serrated ventral margin; pereiopods 2 and 3 very elongated, with multiarticulate carpus; pereiopods 4 and 5 thin and achelate; basipodite well-developed; exopod with rounded diaresis and distal part bearing very small pits.

DESCRIPTION

Subrectangular cephalothorax, height nearly equal with length (holotype: CL = c. 22 mm, CH = c. 21 mm), with short longitudinal carina at midheight ( Fig. 1A, B) ; anterior margin fragmented; ventral margin not clearly visible; posterior margin slightly sinuous with a thin ridge; very elongated rostrum curved upward distally, with four basal suprarostral spines, one median suprarostral spine, one median subrostral spine and three distal spines ( Fig. 1C); ornamentation smooth.

Cephalic appendages well-preserved ( Fig. 1A, B): antennulae (a1) composed of long antennular peduncle with three segments diminishing in length distally and two long and thin multi-articulated flagellae (preserved length: c. 25 mm, Fig. 1B, C); antennae (a2) composed of antennal peduncle with a very long multi-articulated flagellum (preserved length: c. 90 mm); scaphocerite well-developed, oblong and pointed with a longitudinal lateral carina. – Third maxilliped relatively long ending in dactylus ( Fig. 1B, C), ventral margin of carpus, propodus and dactylus bearing one row of small teeth (serrated pattern);

me, merus; mx3, maxilliped 3; p2-p5, pereiopods 2 to 5; pr, propodus; pa1, antennular peduncle; r, rostrum; sc, scaphocerite; s1-s6, somites 1 to 6; sp, spine; t, telson. Scale bars: A, B, 2 cm; C, D, 1 cm.

Pereiopod 1 not preserved; pereiopods 2 and 3 very elongated, both displaying antennae-like multiarticulate carpus, ending in minute chela; pereiopods 4 and 5 almost equal in size, thin and smooth, achelate, ending in small dactyli.

Abdomen convergent distally with smooth ornamentation; somites 1 and 6 very reduced, somite 2 badly preserved, shorter than somite3, somite 3 large and well-developed, somites 4 and 5 short; pleurae of somites ventrally smooth and rounded ( Fig. 1B); pleopods not preserved; telson short (length: c. ⅔ length of uropods), pointed, only known in section; basipodite of the uropods well-developed, subcircular ( Fig.1D); uropodal exopod and endopod elongated, almost equal in length with lateral margins smooth and rounded inferior margins; exopod with median longitudinal carina and a well-developed diaresis with crescent-shaped suture delimiting a distal part uniformly covered with very small pits; endopod slender, with median longitudinal carina and distal part also bearing very small pits ( Fig. 1D).

DISCUSSION

We agree with the diagnosis of Carpopenaeus proposed by Glaessner (1945) and revised by Garassino (1994). The newly described form here is clearly a representative of this genus based upon the following main features:very long rostrum with one subrostral tooth; longitudinal carina on the carapace,pereiopods 2 and 3with multiarticulated carpus, and exopod with a diaresis. Carpopenaeus garassinoi Charbonnier n. sp. differs from theTithonian species Carpopenaeus peterbuergeri Schweigert & Garassino, 2005 in that it has: 1) much thinner pereiopods 4 and 5; 2) pereiopods 2 and 3 of equal length whereas in C. peterbuergeri pereiopods 2 longer than pereiopods 3; and 3) the absence of a branchiocardiac carina well-developed in C.peterbuergeri . Carpopenaeus garassinoi Charbonnier n. sp. differs from both Cenomanian species C. callirostris Glaessner, 1945 and C. septemspinatus ( Dames, 1886) in that it has: 1) a rostrum with four basal suprarostral spines and only one median suprarostral spine whereas the rostrum of C. Callirostris shows six suprarostal spines uniformly distributed and that of C. septemspinatus is shorter with seven suprarostal spines and one distal subrostral spine; 2) the short longitudinal lateral carina on the carapace that is more elongated in C. Callirostris and duplicated in C. septemspinatus ; 3) a third maxilliped with ventral margin serrated and composed of small rounded teeth whereas those of C. callirostris and C. septemspinatus display a row of small spines; 4) the well-developed basipodite; and 5) the distal part of each uropod is covered by small pits whereas the ornamentation is smooth on the uropods of C. callirostris and C. septemspinatus . Moreover, the uropodal exopod of C. septemspinatus does not show any diaresis.

In conclusion, Carpopenaeus garassinoi Charbonnier n. sp. from the Santonian Sahel Alma Lagerstätte is the youngest representative of the genus Carpopenaeus Glaessner, 1945 which was previously known from the Tithonian of the Lithographic Limestones of Zandt, Germany ( Schweigert & Garassino 2005) and from the Cenomanian of Lebanon (Hakel, Hadjoula Lagerstätten).