Chelarctus crosnieri Holthuis 2002, n. sp.
Creators: name: Holthuis, Lipke B.
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Scyllaridae
Chelarctus
Chelarctus crosnieri

description: Chelarctus crosnieri n. sp.   
(Figs 30; 31; 68C)  
TYPE MATERIAL. — Holotype: 72 mm, BORDAU 2, stn CP 1541 (MNHN-Pa 1887).  
TYPE LOCALITY. — Tonga Islands. SW of Tongatapu, 21°15’S, 175°14’W, 319- 333 m.  
ETYMOLOGY. — This new species is named for Alain Crosnier, as a token of gratitude for the extensive help that he has given with the completion of this paper, and also for his patience with my slow pace.  
 MATERIAL EXAMINED. — Tonga Islands. SW of Tongatapu, BORDAU 2, stn CP 1541, 21°15’S, 175°14’W, 319-333 m, 5.VI.2000, 1 holotype 72 mm (MNHN-Pa 1887).   
DESCRIPTION  
The rostrum is rounded anteriorly and constrict- ed at the base, it bears a very distinct and sharp rostral tooth. There is no pregastric tooth, but the gastric tooth is strong, about as large as the rostral tooth; it is placed somewhat closer to the rostral tooth than to the cervical groove. Between the gastric tooth and the cervical groove there are about seven transverse rows of very low, flattened and rounded squamiform tubercles. The cardiac tooth is very low, consisting of two small rounded squamiform tubercles. Between the cardiac tooth and the posterior marginal groove there are about eight transverse rows of very low and anteriorly rounded squamiform tubercles which together form very low anteriorly crenulated ridges. The submedian ridges are hardly indicated. The branchial carina is low and widely interrupted by the cervical groove; there is no tubercle in the gap. The anterior branchial carina ends in two sharp distinct teeth of about the same size that are placed on the inner margin of the orbit. From the posterior of these teeth three short but distinct ridges extend backward; one of these forms the posterior orbital margin, one the dorsal margin of the branchial ridge and the third lies in-between; none of these three bears any tubercles or teeth. The posterior branchial carina ends in a sharp tooth and it has no tubercles except for a few very flattened rounded squamae that are very inconspicuous and form some eight transverse rows. No intermediate row of tubercles was seen. The lateral margin of the carapace bears a distinct anterolateral tooth; behind this tooth the anterolateral margin bears two hardly visible incisions. The mediolateral ridge ends in a sharp tooth behind which there are a few vague flattened squamiform tubercles. A distinct, broadly rounded tubercle is placed just behind the cervical groove practically next to the anterior mediolateral tooth; together with some faint tubercles it may be considered a remnant of the intercervical ridge. No postorbital tubercle is seen. The anterior tooth of the posterolateral margin is flattened and rounded squamiform; it is hardly larger than the tubercles on the mediolateral and posterolateral margins, the latter being about eight or nine in number. Apart from the low squamiform tubercles on the carinae, no true tubercles are seen on the dorsal surface of the carapace, which is covered by very  
C  
short hairs, except for a circular area on either side of the gastric tooth. The posterior marginal groove is narrow and deep, filled with hairs; before it there are two smaller transverse rows of flattened rather indistinct squamiform tubercles; between the groove and the posterior margin of the carapace there are also two transverse rows of small flattened squamiform tubercles. The posterior margin of the carapace shows a shallow emargination in the middle.  
The first abdominal somite has an uninterrupted narrow transverse groove over the middle; behind this groove there are about 20 to 24 short longitudinal grooves, which are not very distinct. The anterior half of the somite is smooth. Abdominal somites II to V have the usual distinct arborescent pattern of narrow grooves in the posterior half, the central part of this pattern forms an oval lobulated figure that is hardly at all elevated and no median carina is present on any of the somites. The anterior half of somite II shows two short interrupted transverse grooves, which are slightly crenulate and bear a posteriorly directed row of very short hairs. In somites III to V, the anterior half is smooth and shows at the most a few small pits. The posterior margin of somites I to III shows a distinct, though small, median incision; this incision is not visible in somites IV and V. The posterior margin of somite VI is slightly convex in the middle. The firm anterior part of the telson shows larger and smaller flattened, rounded tubercles; the posterior margin of this firm part carries four sharply pointed triangular teeth of about the same size. The pleura of abdominal somite I end laterally in two distinct rounded lobes. The margins of pleura II to V are without any teeth, their tops are bluntly rounded. The arborescent markings of the somites continue on to these pleura.  
The anterior margin of the antennular somite is concave in each half. There is a median incision flanked by a bluntly rounded tooth at either side. The anterolateral angles of the somite show each two low and inconspicuous blunt teeth.  
The distal margin of the last (sixth) segment of the antenna bears six teeth, the outer of which is very broad distally and has the distal margin slightly concave in the middle; the next three teeth have the distal margin rounded with a small sharp tooth at the top. Near the inner margin of the segment are two narrower teeth that end in a triangular point. Behind these two teeth the inner margin of the segment shows a small incision. The inner anterolateral angle of the fifth antennal segment bears a rather wide, sharply tipped tooth. The fourth antennal segment bears an oblique carina over the full length of the dorsal surface; apart from this carina the upper surface shows no tubercles or ridges. The anterior margin of the fourth segment bears a single large tooth; between this tooth and the top of the segment the anterior margin is minutely serrate. The outer margin of the segment bears two distinct teeth which are about as large as, but distinctly more acute than, the top of the segment.  
The anterior margin of the epistome is rather deeply divided in the middle and the two halves are convex.  
P.1 is shorter and far more robust than P.2. The dactylus, propodus and carpus are smooth; the outer surface of the merus has a shallow ventral groove filled with very short hairs. The dactylus of P.2 is longer than any other of the dactyli; it is more than half as long as the propodus of P.2. This propodus is slender without any teeth. There are no hairs on either propodus or carpus. The merus is as long as propodus and carpus combined; it has a shallow pubescent groove in the upper half of the outer surface, no other hairs are seen. P.3 has the dactylus slender and slightly shorter than that of P.2. The propodus is strongly compressed and very high, much higher than any of the segments in the other legs, it is as high as long. The anteroventral angle of the propodus is blunt and produced forward, forming a kind of subchela with the dactylus. A blunt ridge extends over the full length of the propodus, above it there are two parallel longitudinal shallow grooves, below it the propodus is strongly keellike compressed. On the upper margin of the propodus there is a longitudinal row of short hairs. The carpus has some short hairs on the anterodorsal margin. The merus is elongate and has two longitudinal pubescent grooves on the outer surface, but otherwise does not show any hairs. P.4 has the dactylus somewhat shorter than that of P.3. The propodus is compressed, about as long as the propodus of P.3 but slightly more than half its height. The outer surface shows two shallow longitudinal pubescent grooves. The lower margin of the propodus is produced anteriorly in a distinct blunt tooth, which almost reaches the base of the dactylus. The carpus and merus of P.4 are similar to, but slenderer than those of P.3. No hairy fringes are observed on the dorsal margin of any of the segments. The dactylus of P.5 is shorter than that of P.4; the outer surface of the merus has a shallow longitudinal hairy groove in the upper half. The lower surface of this segment shows a very short pubescence.  
The anterior margin of the thoracic sternum is incised in the middle; the two halves are distinctly convex and reach beyond the anterolateral angles of the sternum. The sternum is smooth, with rows of short pubescence at the lines between the segments. Behind the base of the fifth leg the thoracic sternum shows a rounded carina, but no teeth.  
The pleopods of the second abdominal somite have the exo- and endopod narrow and slender, reaching the midddle of the somite. The pleopods of somites III to V have the exopod small and broadly oval and the endopod reduced to a bud.  
 Colour   
A coloured photograph of the holotype specimen taken when the animal was fresh shows a yellowish grey animal with a remarkable pattern of dark red circular dots and lines. The fourth antennal segment is plain yellowish grey with the oblique dorsal carina red, while there is also some red along the anterior margin. A dark red circle is seen around the eyes and a red line along the anterior margin of the antennular and antennal somites. The tip of the gastric tooth is whitish and at the base of the tooth is a roundish red dot. A transverse row of three of such circular dots is placed in the median area of the carapace behind the cervical groove. A red dot is also visible on the carapace behind the anterior tooth of each posterior branchial carina. A transverse row of red dots extends before the posterior marginal groove; the distance between the inner two is larger than that between each outer pair. There are four smaller dots on the posterior margin of the carapace. Abdominal somite I has a large dark red spot in the middle; apart from that, there are two dots on each half of the anterior part of the somite and one on each side of the central spot in the posterior half of the somite. Somites II and III each have two transverse rows of four dark red dots (one row in the anterior half of the somite and one in the posterior half). Somites IV and V each have two similar rows of dots, except for the fact that the posterior rows each have only two dots. The tailfan is whitish. P.2 to P.5 have a wide purple band over the merus.  
REMARKS  
So far the species is only known from the holotype.
description: Published as part of Holthuis, Lipke B., 2002, The Indo-Pacific scyllarine lobsters (Crustacea, Decapoda, Scyllaridae), pp. 499-683 in Zoosystema 24 (3) on pages 582-586, DOI: 10.5281/zenodo.4689240