28 



R. BOTTGER-SCHNACK 



posterior margin. This approach differs from that traditionally used 

 in oncaeid taxonomy, where the telescoping of somites is not 

 considered in length measurements. Traditional length data of Red 

 Sea oncaeids as given by Bottger-Schnack et al. (1989) are only up 

 to 70% of the sizes presented in this paper, due to the excessive 

 telescoping of somites in the sorting medium. In order to make sizes 

 of the species in this paper comparable to those of previous taxo- 

 nomic descriptions (e.g. Heron & Bradford-Grieve, 1995; Bersano 

 & Boxshall, 1994), length data of each species were obtained by the 

 traditional method as well (i.e. measured dorsally from the tip of 

 prosome to the distal end of caudal ramus) and are given in square 

 brackets. 



Descriptive terminology for body and appendages follows that of 

 Huys and Boxshall (1991). Abbreviations used in the text are: ae = 

 aesthetasc; CR = caudal rami; enp = endopod; exp = exopod; 

 exp(enp)-l(-2, -3) = to denote the proximal (middle, distal) segment 

 of a ramus; P1-P4 = swimming legs 1^1. Species of Oncaeidae have 

 a number of pores and other integumental structures (e.g. pits, 

 scales) on body surfaces, but only those discernible with a light 

 microscope were figured or mentioned. 



O. venusta was examined with a Philips XL30 scanning electron 

 miscroscope. Specimens were prepared by dehydration through 

 graded ethanol, critical point dried, mounted on stubs and sputter- 

 coated with palladium. 



Type and other material is deposited in the collections of The 

 Natural History Museum, London (BMNH), Smithsonian Institu- 

 tion (USNM) and the Zoologisches Institut und Museum der 

 Universitat Hamburg (ZMH). Paratypes or other material retained in 

 personal collection, R. Bottger-Schnack designated (RBS). 



GENERIC DIAGNOSIS 



Order POECILOSTOMATOIDA Thorell, 1859 

 Family ONCAEIDAE Giesbrecht, 1892 



Oncaea sensu stricto 



Diagnosis. Body cyclopiform, prosome stout or broad-oval. P2- 

 bearing somite with (c/eve/-subgroup) or without (vem/sta-subgroup) 

 dorsoposterior projection in female. Cephalosome without lateral 

 lobate extensions. Genital double-somite female slightly flask- 

 shaped, not particularly swollen dorsally. First and second postgenital 

 somites shorter than anal one. Anal somite with wide anal opening; 

 operculum with small spinules. 



Exoskeleton well or heavily chitinized, usually ornamented with 

 numerous pores, ridges and scales. 



Sexual dimorphism in antennule segmentation and armature, 

 antennary setae, maxilliped, genital segmentation and ornamenta- 

 tion, endopods of P1-P3 (sometimes also in P4), P5 and P6, and in 

 caudal ramus. 



Antennule 6-segmented in female with armature formula l-[3], 2- 

 [8], 3- [5], 4-[3 + ae], 5-[2 + ae], 6-[6 ( 1 +ae)]; 4-segmented in male 

 with formula l-[3], 2-[8], 3-[4], 4-[ll + (1 + ae) + 2ae]. Distalmost 

 seta of female segment 3 absent in male. Aesthetascs slender. 



Antenna. Enp-1 with triangular projection on outer margin form- 

 ing concavity distally ; inner margin with 1-2 denticular rows. Enp-2 

 shorter than enp-1; posterior surface with double row of spinules; 

 lateral armature consisting of 3 well developed, bare or minutely 

 pinnate setae (I, II and IV) and 1 pinnate spine (III) in female; distal 

 armature consisting of 4 pinnate setae, 1 long bare or minutely 

 pinnate seta, and 2 bare setae; posterior seta well developed. Sexual 



dimorphism in lateral armature of enp-2, with seta III much stouter 

 and seta IV spiniform and curved in male, both elements shorter than 

 in female; often also expressed in coxobasal seta, being short and 

 naked in male. 



Labrum distinctly bilobate, forming paired semi-circular 

 posteroventral lobes. Lobes without marginal teeth but with row of 

 minute denticles around outer ventral margin, with row of long fine 

 setules latero-distally (except for c/eve/-subgroup) and dentiform 

 processes converging and decreasing in size medially. Lobes sepa- 

 rated by semicircular vertex covered anteriorly by overlapping rows 

 of small hyaline petaloid flaps, flanked by slit-like pores located on 

 proximal part of each lobe; posterior face with median sclerotized 

 teeth and usually with paired patches of long fine setules (absent in 

 media). Anterior face with paired spinular patches or denticulate 

 rows (except for venusta); paired integumental pockets usually well 

 developed, free margin of pockets serrated or ornamented with 

 denticle row. 



Mandible with 2 blades, 2 setae and 1 spine. Dorsal blade with 3 

 dentiform processes along distal margin and up to 2 additional 

 processes along dorsal margin. 



Maxillule weakly bilobate; praecoxal arthrite with innermost 

 element proximally displaced and outermost element spiniform and 

 bearing transverse row of spinules. 



Maxilla. Allobasis shorter than syncoxa. 



Maxilliped (female). Large, moderately ovoid. Basis without 

 ornamentation on posterior surface; anterior surface with spinular 

 row and spinular fringe along palmar margin half the distance 

 between distal seta and endopod; both palmar elements long, 

 spiniform and spinulose, similar in length. Enp-1 completely sepa- 

 rated. Enp-2 with long, minutely pectinate claw, rudimentary outer 

 setule and fused unipinnate inner spine. 



Maxilliped (male). Palmar margin forming shallow longitudinal 

 cleft bordered by anterior denticulate fringe and posterior multiple 

 rows of coarse, blunt spinules; not developed into distal flap. 

 Anterior surface of basis with patch of transverse spinular rows. 

 Palmar setae short, smooth. Endopodal claw curved, naked, with 

 hyaline apex. 



PI exopod. Outer and terminal spines with subapical tubular 

 extensions. 



PI endopod. Enp-3 distal spine stout, with broad serrate hyaline 

 flange; base of distal inner seta concealed beneath long anterior 

 spinous outgrowth of segment; length of outgrowth (often) sexually 

 dimorphic, relatively longer in the male. 



P2-P4 exopods. Outer spines stout, with broad, serrate hyaline 

 flanges; lateral spines not markedly increasing in size distally. 



P2-P4 endopods 3-segmented. Enp-3 twice as long as enp-1 and 

 -2 combined or longer; with large conical processes on P2-P3, not 

 on P4. Enp-3 distal spine short in P2-P3, longer in P4; distal outer 

 spine small in P2-P3, always longer than conical process in female. 

 Sexual dimorphism usually expressed in length of conical proc- 

 esses, being longer in the male, and in spine length of enp-3, being 

 reduced in the male. 



Swimming leg armature formula: 



Leg 



Coxa 



Basis 



Exopod 



Endopod 



PI 



0-0 



1-1 



I-0;I-1;III,I,4 



0-1:0-1:1,5 



P2 



0-0 



1-0 



1-0:1-1 ;III.I,5 



0-1:0-2:1,11,3 



P3 



0-0 



1-0 



I-0;I-1;II,I,5 



0-1:0-2:1,11.2 



P4 



0-0 



1-0 



I-0;I-1;II,I,5 



0-1:0-2:1,11.1 



P5 small; represented by outer basal seta and small exopod with 

 2 spiniform setae; exopod delimited at base in females, fused to 



