\ x (252 644 eo 
Bull. nat. Hist. Mus. Lond. (Zool.) 68(1); 19-26 
A Issued 27 June 2002 

Two new species of the Indo-Pacific fish genus 
Pseudoplesiops (Perciformes, 
Pseudochromidae, Pseudoplesiopinae) 

ANTHONY C. GILL 
Fish Research Group, Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 
SBD, U.K. 
ALASDAIR J. EDWARDS 
Tropical and Coastal Management Studies, Department of Marine Sciences and Coastal Management, 
University of Newcastle, Newcastle upon Tyne NEI 7RU, U.K. 


SYNOPSIS. Pseudoplesiops immaculatus is described from 72 specimens from throughout the West Pacific and the eastern and 
central Indian Ocean. It is distinguished from congeners in having, in combination, a prominent intermandibular flap and an 
unspotted operculum. Pseudoplesiops occidentalis is described from five specimens from the Maldive Islands, central Indian 
Ocean. It is distinguished from congeners in having, in combination, II,23 dorsal-fin rays, 26—28 scales in lateral series, and scales 
with distinct centres and radii in all fields. 
INTRODUCTION 
The genus Pseudoplesiops Bleeker was recently diagnosed to 
included pseudoplesiopine pseudochromids with the medial lami- 
nae of the pelvic bones expanded dorsally (Gill & Edwards, 1999). 
Aside from this synapomorphy, members of the genus are distin- 
guished from other pseudoplesiopines in possessing the following 
combination of external characters: scales in lateral series 26—42; 
lower lip complete (uninterrupted at symphysis); and preopercular 
pores usually 7 (rarely 6 or 8), with a pore present at the upper 
terminus of the preopercle. The genus is mostly confined to the 
eastern Indian and Pacific Oceans, but two undescribed species 
occur in the Maldive Islands, central Indian Ocean. Although it is 
our intention to produce a revision of the genus, we herein describe 
the two Maldives species in order to make their names available for 
a forthcoming guide to western and central Indian Ocean fishes. 
MATERIALS AND METHODS 
Institutional abbreviations follow Leviton et al. (1985). All meas- 
urements to the snout tip were made to the midanterior tip of the 
upper lip. Length of specimens are given in mm standard length 
(SL), which was measured from the snout tip to the middle of the 
caudal peduncle at the vertical through the posterior edge of the 
dorsal hypural plate. Head length was measured from the snout tip to 
the posteriormost edge of the opercular membrane. Snout length 
was measured over the shortest distance from the snout tip to the 
orbital rim, without constricting the fleshy rim of the latter. Orbit 
diameter was measured as its fleshy horizontal length. Interorbital 
width was measured as the least fleshy width. Upper jaw length was 
measured from the snout tip to the posterior edge of the maxilla. 
Predorsal, preanal and prepelvic lengths were measured from the 
snout tip to the base of the first spine of the relevant fin. Body width 
was measured between the posttemporal pores. Caudal peduncle 
length was measured from the base of the last anal-fin ray to the 
ventral edge of the caudal fin at the vertical through the posterior 
© The Natural History Museum, 2002 
edge of the ventral hypural plate. Caudal peduncle depth was 
measured obliquely between the bases of the last dorsal- and last 
anal-fin rays. Measurements of fin rays excluded any filamentous 
membranes. Pectoral fin length was measured as the length of the 
longest middle ray. Caudal fin length was measured as the length of 
the lowermost ray on the dorsal hypural plate. 
Counts of dorsal-, anal- and pelvic-fin spines (unsegmented rays) 
and segmented rays are presented, respectively, as Roman and 
Arabic numerals. If the last dorsal- or anal-fin ray was divided at its 
base it was counted as a single ray. Counts of branched, segmented 
rays in the dorsal and anal fins included unbranched rays behind the 
first branched ray. A value was not recorded if, due to tip damage, a 
branched or unbranched condition could not be determined for the 
segmented ray preceding the anteriormost branched ray. As in most 
actinopterygian fishes, the upper ray in the pectoral fin is rudimen- 
tary and rotated so that its asymmetrical medial and lateral hemitrichs 
appear to represent two separate rays; these were counted as a single 
ray. Procurrent caudal-fin ray counts were of the rays above (“up- 
per’) and below (‘lower) the principal caudal-fin rays. The uppermost 
principal caudal-fin ray was defined as the ray articulating with 
hypural 5, and the lowermost principal caudal-fin ray was the ray 
articulating with the cartilage nubbin between the distal tips of the 
parhypural and the haemal spine of preural centrum 2. All 
pseudoplesiopine species normally have 17 (9 + 8) principal caudal- 
fin rays. 
Counts of ‘scales in lateral series’ were of the posteroventrally 
oriented transverse scale rows on the midside, beginning with the 
row through the tubed scale at the branchial opening and ending with 
the row through the scale at the midposterior edge of the hypural 
plate. “Scales in transverse series’ were counted anterodorsally from 
the anal-fin origin to the dorsal-fin base. Circumpeduncular scales 
were counted in a zig-zag fashion around the middle of the caudal 
peduncle. Gill-raker counts were of the outer rakers on the first arch, 
including rudiments; the angle raker is included in the lower-limb 
(second) count. Counts of pseudobranch filaments included all 
rudiments. Nomenclature of head pores follows Winterbottom 
(1986), as modified by Gill et al. (2000). 
Counts of vertebrae are presented in the form precaudal + caudal 
