BASAL LAOPHONTID EVOLUTION 



91 



presumably because of the lack of a base for comparison in Farran's 

 (1913) description and illustrations which omitted P2 and P3. The 

 problem is exacerbated by the aberrant left-right asymmetry (1.220 

 vs 1.320) displayed on the P2 endopods. It is unclear whether the 

 reduced setal formula is real and therefore indicative for the pres- 

 ence of a second species in the western Pacific. There is very little 

 additional evidence pointing in this direction except for the different 

 cephalothorax shape (in lateral aspect: compare Fig. 25C) and some 

 morphometric discrepancies in the caudal rami, which appear to be 

 longer, and in the exopods of P2-P4, which are more abbreviated. 

 E. bulligera cannot be retained in the genus Esola because of the 

 absence of (1) distinct spinous processes on the first antennulary 

 segment, (2) cup-shaped integumental pores on the genital (double-) 

 somite and caudal rami, (3) characteristic labral ornamentation and 

 (4) caudal ramus sexual dimorphism. It is reminiscent of Bathyesola 

 compacta (see below) in the presence of only one pair of cup-shapes 

 pores on the cephalothorax but differs from it in the reduced 

 armature on the 9 P5 exopod and the transformed P4 endopod which 

 is the most significant autapomorphy of E. bulligera, justifying its 

 placement in a new genus Corbulaseta. 



Genus Bathyesola gen. nov. 



Diagnosis (based on 9 only). Laophontidae. Body cylindrical; 

 posterolateral corners of 9 genital double-somite and second ab- 

 dominal somite laterally and backwardly produced. Integument of 

 cephalothorax and body somites with dense pattern of spinules and 

 setules. Rostrum large, partly delimited at base. Anterolateral pair of 

 small integumental cup-shaped pores present on cephalothorax. 

 Caudal rami not modified in 9, cylindrical and elongate. 



Sexual dimorphism presumably in antennule, P3 endopod, P5, 

 P6, and genital segmentation. 



Antennules slender; 7-segmented in 9; segment 1 without spinous 

 processes along posterior margin; with aesthetasc on segment 4 

 (fused basally to 2 setae) and as part of apical acrothek on segment 

 7. Antenna with 4 setae on exopod; allobasis with abexopodal seta. 

 Labrum without overlapping scales distally but with pattern of 

 spinules anteriorly. Mandible with 2-segmented palp; endopod free, 

 with 3 setae; exopod represented by single seta; basis represented by 

 2 setae. Maxillule with defined exopod. Maxilla with 3 endites on 

 syncoxa; endopod represented by 3 setae. Maxilliped robust; syncoxa 

 with 2 setae; entire palmar margin with spinules; endopodal claw 

 relatively stout. 



PI with large 3-segmented exopod bearing 4 setae on exp-3 and 

 relatively short endopod; enp-1 without inner seta, enp-2 with 

 minute seta and short, curved claw. P2-P4 with 3-segmented exopods 

 and 2-segmented endopods. P2 basis with moderately long outer 

 spine. Inner seta of P2-P4 exp-2 reduced. Outer spine of P2-P4 enp- 

 2 setiform, short in P2-P3, long in P4. Armature formula as follows: 



Exopod 



Endopod 



P2 



0.1.123 



1.221 



P3 



0.1.123 



0.321 [ cJ presumably 

 0.1.220] 



P4 



0.1.123 



0.221 



P5 9 with separate rami; exopod relatively short, with 6 setae/ 

 spines; baseoendopod well developed, with 5 setae/spines, apical 

 setae reduced; outer basal seta on short setophore. 



P6 9 forming opercula closing off paired genital apertures; with 2 

 small setae. 



Type and only species. Bathyesola compacta gen. et sp. nov. 



Etymology. The generic name refers to the bathyal distribution 

 of the type species. 



Bathyesola compacta gen. et sp. nov. 



TYPE LOCALITY. 18°50'S, 173°29'W, 'White Lady' site on North 

 Fiji Ridge, west of Fiji; 2765 m depth. Accompanying harpacticoid 

 fauna: several 99 and 86 of Xylora bathyalis Hicks, 1988 

 (Thalestridae: Donsiellinae). 



TYPE MATERIAL. Holotype 9 dissected on 6 slides, deposited in 

 Museum National d'Histoire Naturelle, Paris under MNHNP Cop- 

 1869; collected during STARMER II expedition, station 14 (Kaiyo 

 87), dive 19; 14 July 1989; leg. L. Laubier. 



Etymology. The species name alludes to the compact PI, dis- 

 playing a short and robust endopod. 



Description. 



FEMALE. Body length from anterior margin of rostrum to posterior 

 margin of caudal rami 360 urn. Maximum width ( 105 urn) measured 

 at posterior margin of cephalothorax. 



Body (Fig. 26A-B) cylindrical, slightly dorsoventrally depressed, 

 covered with dense pattern of minute spinules dorsally and laterally. 

 Cephalothorax slightly wider than free somites, posterolateral angles 

 backwardly produced forming small lobate extension (Fig. 26B); 

 with pair of small lateral cup-shaped pores. Posterior margin of 

 cephalothorax and all body somites with row of long setules dorsally 

 and laterally. Pleurotergite of P5-bearing somite almost as wide as 

 anterior somites. 



Genital double-somite wide and dorsoventrally flattened; with 

 lateral, backwardly produced extensions in posterior (=abdominal) 

 half; original segmentation marked by bilateral constriction and 

 spinule row arising from transverse surface ridge dorsally and 

 laterally; posterior half with backwardly directed lobate extensions 

 bearing spinular tuft; ventral surface without spinular ornamenta- 

 tion; genital field located near anterior margin. Sixth legs forming 

 well developed opercula closing off paired genital apertures; each 

 with 2 small setae. 



First postgenital somite with backwardly produced lateral angles, 

 bearing spinular tuft; without ventral ornamentation. Penultimate 

 and anal somites distinctly narrower; ventral posterior border with 

 long spinules. Anal somite with spinulose anal operculum. 



Caudal rami (Fig. 26A-B) widely separated; about 4 times as long 

 as average width; maximum width measured at base; dorsal surface 

 with minute spinules; seta I small, setae II — III well developed, naked 

 and closely set; setae IV (naked) and V (pinnate) with fracture 

 planes, seta V 2.8 times as long as seta IV; setae VI-VII naked. 



Rostrum (Figs 26A) large, blunt anteriorly; delimited at base by 

 transverse surface suture; with paired sensillae anteriorly and me- 

 dian tube-pore dorsally. 



Antennule (Fig. 26A-B) relatively short, distinctly 7-segmented, 

 without spinous processes on segments 1-2. Segment 1 with large 

 spinular patch around anterior margin. Armature formula: 1-[1], 2- 

 [4 + 4 pinnate], 3-[6], 4-[l + (1 + ae)], 5-[l], 6-[2], 7-[5 + 1 pinnate 

 + acrothek]. Acrothek consisting of aesthetasc and 2 naked setae; set 

 on apical pedestal. 



Antenna (Fig. 27A). Coxa with spinules on both inner and outer 

 margins. Exopod short, bearing 2 lateral and 2 apical pinnate 

 elements, and a longitudinal row of fine spinules along outer margin. 

 Allobasis with pinnate abexopodal seta. Endopod with lateral arma- 

 ture consisting of 2 spines and 1 minute seta; distal armature 

 consisting of 2 naked spines and 3 geniculate setae (outermost fused 

 basally to minute seta). 



