Phyllocheres Humes, 1996

Genus Phyllocheres Humes View in CoL

Phyllocheres petalus Humes, 1996 urn:lsid:zoobank.org:act:

( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined: Holotype male ( USNM 278097 About USNM ), allotype female ( USNM 278098 About USNM ), associated with sponge Dysidea sp. [near avara (Schmidt)] 10m depth, Pulau Gomumu , south of Obi, Moluccas, 01 o 50’00” S, 127 o 30’54” E, 30 May 1975. GoogleMaps

Redescription of female: Body ( Fig. 2a View FIGURE 2 ) rounded, dorsoventrally flattened, with cylindrical urosome. Body length:width ratio=1.2:1. Cephalosome exhibiting produced epimera on both posterolateral margins, showing halfmoon shape reaching beyond anterior margin of genital double-somite. Second pedigerous somite shorter than following one and showing concave lateral margins. Third pedigerous somite extended posteriorly, recovering fourth and fifth pedigerous somites and partially genital double-somite. Prosome length:width ratio=0.8:1. Prosome length:urosome length=2:1.

Urosome ( Fig. 2b View FIGURE 2 ) composed of 4 somites. Genital double-somite 1.1x longer than wide; genital area located medially with posterolateral row of setules; pair of dorsal sensilla on posterior region and posterior margin toothed. Postgenital somite as long as wide with sensilla on anterior region and posterior margin toothed. Anal somite 1.1x wider than long and with pair of dorsal sensilla. Caudal rami 1.1x wider than long, armed with 6 setae. Seta I absent and remaining setae with proportion of 1.1:1.9:3.7:3.9:1.7:1. All plumose.

Antennule ( Fig. 2c View FIGURE 2 ) 239 µm long (not including setae), 19-segmented. Basal portion with 9 relatively large segments, and distal portion with 10 long segments. Setation as follows: 1(I)–2, 2(II)–2, 3(III)–2, 4(IV)–2, 5(V)–2, 6(VI)–2, 7(VII)–2, 8(VIII)–2, 9(IX–XIII)–7, 10(XIV)–1+spine, 11(XV)–1, 12(XVI)–2, 13(XVII)–2, 14(XVIII)–2, 15(XIX)–2, 16(XX)–2, 17(XXI)–1+ae, 18(XXII–XXIII)–2, 19(XXIV–XXVIII)–11. Aesthetasc 81 µm long.

Antenna ( Fig. 2d View FIGURE 2 ) 180 µm long (including distal claw); basis unarmed. Exopod 1-segmented, with 2 long apical setae and lateral seta. Endopod 3-segmented, first segment with row of setules on outer margin; second segment with distal seta; third segment ornamented with row of setules on outer margin, proximomedial seta, apical seta, plus straight terminal claw.

Oral cone ( Fig. 2e View FIGURE 2 ) 160 µm, reaching insertion of maxilliped. Mandible ( Fig. 2f View FIGURE 2 ) with 2-segmented palp, armed with 2 distal plumose setae; mandibular stylet 149 µm long, tapering distally. Maxillule ( Fig. 2e View FIGURE 2 ) bilobed, outer lobe with 3 smooth setae. Inner lobe 1.9x longer than outer one, inner margin ornamented with setules, and 4 distal naked setae.

Maxilla ( Fig. 3a View FIGURE 3 ) with claw 1.1x longer than syncoxa, apically curved. Maxilliped ( Fig. 3b View FIGURE 3 ) elongated and narrow, 5-segmented, armed with straight terminal claw. Syncoxa with medial short seta. Basis unarmed. Endopod 3-segmented, each with distal seta, armature formula (1,0,1,1,1+claw).

Leg 1–4 ( Figs. 3c–f View FIGURE 3 ) biramous, 3-segmented. Armature formula as follows:

First exopodal segment of leg 1 ( Fig. 3c View FIGURE 3 ) with spine 3x longer than spine of the following segment. Second exopodal segment of leg 1 ( Fig. 3c View FIGURE 3 ) with protruding tooth distally located.

Leg 5 protopod ( Fig. 3g View FIGURE 3 ) fused to fifth pedigerous somite. Basal seta inserted directly on segment. Free segment of leg 5 ornamented with three equally sized setae.

Redescription of male: Body shape ( Fig. 4a View FIGURE 4 ) similar to female, rounded, dorsoventrally flattened, with cylindrical urosome. Body length:width ratio=1.3:1. Cephalosome with produced epimera on both posterolateral margins, reaching anterior margin of genital somite, showing radial bands as seen on female ( Fig. 4b View FIGURE 4 ). Third pedigerous somite extending posteriorly and entirely covering fourth, fifth, and genital somites. Prosome length: width ratio 0.9:1. Genital somite ( Fig. 4c View FIGURE 4 ) 1.5x wider than long with 2 setae (leg 6) on each posterior corner. First and second postgenital somites and anal somite with posterior margins crenulated. Caudal rami 1.4x wider than long, armed with 6 setae (seta I absent). Remaining setae with proportion of 1.6:1.7:5.4:3.7:1.9:1. All plumose. Prosome:urosome length ratio=2.5:1.

Antennule ( Fig. 4d View FIGURE 4 ) 262 µm long (not including setae), 17-segmented. Basal portion with 9 relatively large segments, and distal portion with 8 long segments. Antennular homologies formula: 1(I)–2, 2(II)–2, 3(III)–1, 4(IV)– 2, 5(V)–2, 6(VI)–2, 7(VII)–2, 8(VIII)–2, 9(IX–XII)–6, 10(XIII)–1, 11(XIV)–1+spine, 12(XV–XVI)–3, 13(XVII)– 2, 14(XVIII)–2, 15(XIX–XX)–2, 16(XXI)–2+Aesthetasc, 17(XXII–XXVIII)–9. All setae smooth, aesthetasc 112 µm long.

Remaining structures as described on female.

Remarks: In the original description Humes (1996a) used many plesiomorphic characteristics commonly found in Asterocheres as diagnostic features for Phyllocheres , such as an exopod of antenna 1-segmented; 3-segmented endopod with a terminal segment bearing two short setae and a long seta. Oral cone short. Mandibular palp 2- segmented with two terminal setae. Maxillule with large inner lobe having four setae; small outer lobe with three setae. Maxilla 2-segmented. Maxilliped 5-segmented, sexually dimorphic, with medial prominence on the second segment. Legs 1-4 biramous, with both rami 3-segmented; second endopodal segments of all legs with two setae. Leg 5 with free segment bearing three setae.

However, the few characteristics originally exclusive to the genus description have some differences that are observed in this redescription of Phyllocheres : two distal setae on the distal margin of the third endopodal segment of legs 1 and 2, exhibiting the armature formula (1,2,3) instead of (1,1-I,3). In addition, the distal margin of the third exopodal segment of leg 1 was originally described as having a spine, with the armature formula (III,I,3), but, on this redescription, it is possible to confirm that the distal element on the segment is a seta, therefore having the same plesiomorphic condition as seen in Asterocheres (III,1,3).