First report of the genus Bicorniphontodes (Copepoda, Harpacticoida, Ancorabolidae) in South Korea, with descriptions of three new species

We report the occurrence of the genus Bicorniphontodes George, Glatzel & Schröder, 2019 in Korean waters, with descriptions of three new species: Bicorniphontodes lacuna sp. nov., B. comptus sp. nov., and B. huysi sp. nov. Morphology analysis was carried out to reconstruct the phylogenetic relationships of Bicorniphontodes species, including the three new species. Parsimony analysis based on 41 characters revealed that the three new species are clustered together as a monophyletic clade, of which B. horstgeorgei (George & Gheerardyn, 2015) is a sister species. The monophyletic status of three new species was supported by five synapomorphies, such as the micro-morphological conditions of the exopodal segments of the first leg, coxae of the second to fourth legs, exopod of the fifth leg in the female and baseoendopod of the fifth leg in the male, and the maxillular endopod represented by two setae. These three species can be easily distinguished based on the morphology of the rostrum, cephalothoracic processes, female genital double-somite, caudal rami, and second endopodal segment of the third leg in the male. The taxonomic position of B. bicornis sensu Kim, 2013 in Korean fauna was reevaluated based on the newly collected material from Udo Islet near Jeju Island; this resulted in a synonym of B. huysi sp. nov.


INTRODUCTION
Since its establishment, the family Ancorabolidae Sars, 1909 has been modified and revised (Lee & Huys, 2019;George, 2020). Systematic confusion began with the incorporation of the genus Laophontodes Scott T., 1894 into the family by Lang (1936), resulting in an extension of the familial boundary. Subsequently, Lang (1944Lang ( , 1948 subdivided the family into two subfamilies, Ancorabolinae Sars, 1909 and Laophontodinae Lang, 1944; the latter subfamily was erected for Laophontodes based on plesiomorphic characters such as endopod prehensility in the first leg, basis elongation in the first leg, and the presence of the antennary exopod. However, the subfamily was not characterized by any autapomorphies (George, 2006;George, 2017); thus, some researchers began to question Lang's subdivision of Ancorabolidae and Laophontodinae (e.g., Gee & Fleeger, 1986;

MATERIALS & METHODS
To investigate the diversity of Korean harpacticoids in sediments, field campaigns were carried out along the coastlines and on islands using hand nets and Smith-McIntyre grabs, and by SCUBA diving. Sediment samples were immediately fixed with a 5% formaldehyde solution. In the laboratory, meiofaunal animals were extracted by the decanting method (Pfannkuche & Thiel, 1988) with a sieve (mesh size, 50 µm) and stored in 95% ethanol. Subsequently, harpacticoids were sorted under a stereomicroscope (M165C; Leica, Germany) and Bicorniphontodes species were temporarily placed in lactic acid. Morphological examinations were performed using a differential contrast microscope (BX53; Olympus, Tokyo, Japan) equipped with a drawing tube. Pencil drawings of habitus and appendages were made using the sandwich mounting method (Huys & Boxshall, 1991) and the hanging drop method (Humes & Gooding, 1964), respectively. Dissected parts of the examined specimens were mounted in lactophenol and covered with a coverslip (to prevent urosome depression, a small amount of paraffin was added in the mounting media); they were then sealed with Canada balsam. Digital inking was done using a Wacom drawing tablet (Cintiq DTK-1301; Wacom, Saitama, China) running Adobe Photoshop CS6 software (Adobe Inc., San Jose, CA, USA). A map showing the sampling stations for Bicorniphontodes species (Fig. 1) was generated using Surfer software (version 12). Scale bars are in micrometers. The examined material was deposited in the collection of the Marine Biodiversity Institute of Korea (MABIK), Seocheon, Korea and the Marine Interstitial fauna Resources Bank (MInRB) in the Korea Institute of Ocean Science and Technology (KIOST), Busan, Korea.
A cladistic analysis was conducted to determine possible phylogenetic relationships of the Bicorniphontodes species, including three new species described herein. Unfortunately, B. hamatus and B. ornatus were excluded from the ingroup because their original descriptions are insufficient for a detailed assessment of morphological characters. The cladogram was rooted using an outgroup taxon, Laophontodes typicus Scott T., 1894, known to be closely related to Bicorniphontodes (George, 2020). The character matrix was coded from 41 selected morphological characters as binary (0-1) or multistate (0-n). All characters were coded in accordance with the principle of "oligomerization" (the fusion of segments or loss of setal elements on appendages), which is considered an irreversible evolutional process in copepods (Huys & Boxshall, 1991). A presumably plesiomorphic state was represented by "0", a presumably apomorphic state by "1" or "2", and missing data by "?". Parsimony analysis was performed using the program NONA (Goloboff, 1999) interfaced with the program WinClada software (ver. 1.00.08) (Nixon, 2002). Ratchet Island Hopper analysis (Nixon, 1999) was conducted with the following settings: 1,000 interations, five trees to hold/ interation, 10 characters to sample, "amb-poly=", 10 random constraint level, and 0 random seed. Bootstrap values were also computed using the Tree-Bisection-Reconnection (TBR) method in WinClada software with the following options: 500 replications, 10 replicate searches, one starting tree per replication, and a maximum of 100 trees. Within the selected cladograms, apomorphic and homoplastic characters were arranged using the "Unambig changes only" option. The electronic version of this article in Portable Document Format (PDF) will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix http://zoobank.org/. The LSID for this publication is: [urn:lsid: zoobank.org:pub:CA40EAE8-2B46-40A1-88D5-B32A80ADDD05]. The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central and CLOCKSS.  Description of female (based on the holotype MABIK CR00248414).-Total length 437 µm from tip of rostrum to posterior end of caudal rami in dorsal view (range = 339-437 µm; mean = 396 µm, n = 8). Body ( Fig. 2A) cylindrical, tapering posteriorly.

Taxonomy
Rostrum (Figs. 2A, 6A) distinctly prominent, basally fused to cephalic shield; apical tip weakly produced, with two sensilla and one middorsal tube pore; lateral margins with one pair of pores. Prosome ( Fig. 2A) composed of cephalothorax and three free pedigerous somites. Cephalothorax ( Figs. 2A, 6A) wide, about 28% of body length, with one pair of  processes well-developed, with one small notch bearing one sensillum in the middle of the outer margin and one distinct sensillum-bearing socle on inner margin; dorsal surface covered with several sensilla and pores, and with anterior and posterior cuticular ridges; anterior cuticular ridges distinctly concave; posterior transverse dorsal ridges with four sensillum-bearing socles. Pedigerous somites bearing P2-P4, narrower than cephalothorax, laterally protruded; dorsal surface with one middorsal pore and paired short cuticular ridges on anterior half, and broadly sclerotized dorsal area on posterior half; dorsal sclerotized area subdistally with two sensilla and distally with six, four, and four sensillum-bearing socles, respectively; laterally with one pore, one sensillum and one sensillum-bearing socle; hyaline frills serrate. Urosome (Figs. 2A, 3A) composed of P5-bearing somite, genital double-somite and three abdominal somites. P5-bearing somite more protruded laterally than preceding somite, with one middorsal pore, one pair of dorsolateral pores, one pair of lateral sensilla and four dorsal sensillum-bearing socles; hyaline frill as those of prosomites. Genital double-somite completely fused, distinctly contracted as furrows probably indicating original division (see arrowheads in Fig. 2A, 3A); genital half with one middorsal pore, one pair of dorsolateral sensillum-bearing socles, one pair of lateral sensilla, and one pair of posterolateral protuberances carrying sensillum; first abdominal somite dorsally with Caudal rami (Figs. 2A, 3A, 3C) slightly divergent, elongate, about eight times as long as wide, ornamented proximally with one lateral and one ventral tube pore, and subdistally with one lateral pore, one ventral tube pore and one row of stout ventral spinules; with seven setae: setae I and II inserted at distal fifth of lateral margin, dorsolateral seta II twice as long as ventrolateral seta I; seta III arising from dorsolateral surface subdistally, about 1.5 times as long as seta II; terminal setae IV and V fused basally; seta IV unipinnate, as long as caudal ramus; seta V bipinnate, about three times as long as seta IV; seta VI inserted at distal inner corner, slightly longer than seta I; tri-articulate seta VII arising from a small peduncle on dorsal surface subdistally, as long as caudal rami.
Antennule (Fig. 4A) five-segmented. First segment with one weak outer protuberance surrounded by spinules, two rows of inner spinules, and one plumose inner seta. Second segment larger than preceding one; inner margin with several spinules, outer margin with a distinct bump bearing long spinules, and anterior surface with one tube pore and one small protuberance (near two peduncles bearing long setae); with two plumose setae and seven bare setae. Third segment longest, with five bare inner setae; distal inner corner posteriorly with one long bare seta and one peduncle carrying one aesthetasc and one long bare seta. Fourth segment smallest, with one long bare inner seta. Distal segment with three bare inner setae, one bi-articulate outer seta, one bare and two bi-articulate anterior setae subapically, two bi-articulate apical setae; with one apical acrothek composed of one aesthetasc and two long setae. Antenna (Fig. 5A) three-segmented. Coxa small, unornamented (damaged during dissection process). Allobasis elongate, ornamented with two rows of spinules along abexopodal margin. Exopod represented by one small seta (see arrowhead in Fig. 5A). Endopod as long as allobasis, ornamented with inner spinules, one group of anterior spinules, and two spinulose subdistal frills; lateral armature composed of two unipinnate spines and one delicate seta, and distal armature comprising two unipinnate spines, three geniculate setae, and one tiny seta which is fused basally to adjoining longest geniculate seta.
Mandible (Figs. 5B, 5C). Coxa with one bulge medially and one row of spinules proximally; slender gnathobase armed with multicuspidate teeth and one unipinnate seta (lost during a dissecting process in holotype; present in a few paratypes). Palp onesegmented, with two basal plumose setae; exopod represented by one plumose seta and endopod represented by one bare and two plumose setae.
Maxillule (Fig. 6B). Praecoxal arthrite ornamented with one row of posterior spinules and one row of anterior spinules subdistally; with four distal spines (of which anterior two ones bearing one large spinule subdistally), three lateral setae, and two juxtaposed anterior setae. Coxal endite with two bare distal setae. Basis with two endites; distal and lateral ones with three and two bare setae, respectively. Both rami incorporated into basis; exopod represented by one small and one long uniplumose seta; endopod represented by one long bare and one long uniplumose seta.
Maxilla (Fig. 5D). Syncoxa ornamented with spinules along outer and inner margins, one row of anterior spinules, and two rows of posterior spinules; with two endites: proximal endite with two unipinnate setae (of which proximal one fused to endite basally) and one bare seta; distal endite with one bare and two unipinnate setae. Allobasis drawn out into stout unipinnate claw, with three accompanying bare setae. Endopod represented by two bare setae (fused basally).
Maxilliped (Fig. 5E) three-segmented. Syncoxa elongate, with two rows of spinules and one weakly plumose subdistal seta on medial surface. Basis longer than syncoxa; inner and outer margins slightly convex, ornamented with long setules. Endopod one-segmented, small, with one stout claw as long as basis, accompanied by one small seta. P1 (Fig. 6C). Praecoxa large, triangular, unornamented. Intercoxal sclerite transversely elongate. Coxa elongate, with one row of outer spinules subdistally. Basis elongate, with one plumose outer seta accompanied by few spinules at its base, and few anterior spinules; inner seta plumose, displaced onto anterior surface near inner margin; pedestal for insertion of inner ramus well-developed, with spinules distally. Exopod three-segmented, reaching 2/5 of enp-1; exp-1 with outer spinules and one unipinnate and comb-like outer spine; exp-2 with inner and outer spinules, and one geniculate outer seta; exp-3 smallest, with few outer spinules and four (two outer and two distal) geniculate setae (of which innermost one longest and plumose at distal half). Endopod prehensile, twosegmented; enp-1 elongate, about twice as long as exopod, with outer and inner setules; enp-2 small, with outer setules, one stout spine and one geniculate seta distally, and one tiny posterior seta subapically.
P5 (Figs. 3A, 3E, 3F) two-segmented. Baseoendopod elongate, with two groups of setules and one subapical tube pore on anterior margin, one row of dorsal spinules near posterior margin, and two ventral tube pores; with elongate setophore carrying one bare seta. Endopodal lobe completely incorporated into baseoendopod, represented by two fishbone-like spines. Exopod shorter than baseoendopod, about 0.7 times as long as baseoendopod, with one row of long anterior setules and one ventral tube pore; with one plumose anterior and one posterior seta proximally, one pinnate dorsal seta subapically, and one long plumose and one pinnate apical seta.
Urosome (Figs. 2B, 8A) six-segmented, genital and first abdominal somites separated. Antennule ( Fig. 4B) subchirocer, seven-segmented. First segment with one weak anterior protuberance ornamented with spinules and one row of outer spinules, and two rows of inner spinules; with one plumose inner seta basally accompanied by one row of posterior spinules. Second segment with one outer bump ornamented with setules, one plumose and six bare inner setae, two anterior setae, and one small anterior protuberance. Third segment with six bare inner setae subdistally and distally. Fourth segment represented by small sclerite, with two bare setae. Fifth segment swollen; posterior surface proximally with one small spinulose spine, one uniplumose and five bare setae, medially with one uniplumose and two bare setae, and subdistally with two long bare setae and one peduncle carrying one aesthetasc and one long seta (fused basally); inner margin with serrate protrusions proximally and small denticles anteriorly and posteriorly. Sixth segment small, with three inner setae. Seventh segment conical in shape, with one bare inner seta, three bi-articulate anterior setae, and two bi-articulate outer setae; anterior surface with one acrothek comprising one aesthetasc and two bare setae.   . Exopod fused to baseoendopod, forming single lobe; anterior margin with three groups of spinules and two tube pores, and one pinnate seta; posterior margin subapically with one fishbone-like seta; distal margin with one plumose seta; dorsal surface with few spinules, medially with elongate setophore carrying one bare seta, and subdistally with one plumose seta; ventral surface medially with two tube pores and one fishbone-like seta, and subapically with one row of spinules. Etymology. The specific name "lacuna" is derived from the Latin noun lacuna, meaning "cavity" or "hollow". It alludes to the typical shape of the female genital double-somite, which has distinct lateral furrows. It is in the nominative singular and is to be treated as a noun in apposition.
Remarks. Bicorniphontodes lacuna sp. nov. is reminiscent of B. clarae and B. comptus sp. nov. in terms of having a cephalothorax with dorsal cuticular ridges and distinctly curved backwardly posterolateral corniform processes. However, this new species differs from B. clarae in the following: the rostrum has a blunt distal margin with a central ventral tube pore (vs. prominent and elongated, and without the tube pore in B. clarae); the distal margin of the antennary endopod has a delicate seta accompanied by the subapical longest geniculate spine (vs. absent in B. clarae); the maxillular exopod and endopod Generally, members of Bicorniphontodes, as well as the related genera Laophontodes and Paralaophontodes, exhibit sexual dimorphism in the male P3 endopod. Although females have a two-segmented endopod, the ramus of the male is three-segmented and exhibits an apophysis arising from the distal margin of the second segment. In B. lacuna sp. nov., however, the division between the distal two segments is probably incomplete, and a tube pore is present where apophysis exists in other congeners (see arrowhead in P5-bearing somite (Figs. 9A, 10A) inverse trapezoidal in dorsal aspect, more extended laterally than free pedigerous somites; dorsal surface anteriorly with one median pore and one pair of dorsolateral pores, and posteriorly with four sensilla; hyaline frill as in prosomites. Genital and first abdominal somites completely fused, forming genital-double somite (Figs. 9A, 10A), but smoothly contracted laterally and original division probably indicated by transverse row of minute spinules; original genital somite slightly swollen laterally, anteriorly with dorsal ridges and one middorsal pore, laterally with two pairs of pores and one pair of sensilla, and dorsolaterally with one pair of sensillum-bearing socles; original first abdominal somite swollen laterally, anteriorly with dorsal ridges, laterally with one pair of setular rows posteriorly, and dorsally with three pores and two sensillum-bearing socles; hyaline frill composed of five distinct projections with two or three lappets; ventral surface posteriorly with one pair of tube pores and one row of fine spinules. Genital field (Figs. 10A, 10B) located at anterior half of genital somite; both gonopores fused medially, forming genital slit covered by single operculum derived from vestigial P6, with one seta and one spinule on both sides; copulatory pore large, located in median depression, accompanied by one pair of tube pores laterally. Second abdominal somite posterolaterally expanded; dorsal surface anteriorly with two cuticular ridges and two lateral pores, posteriorly with two medial sensillum-bearing socles and two pores; lateral margins posteriorly with one pair of setular rows and one pair of sensilla; hyaline frill ornamented with seven projections with two or three lappets; ventral surface posteriorly with one pair of tube pores and one row of stout spinules. Penultimate somite as preceding one in shape; dorsal surface with two cuticular ridges medially and two pores posteriorly; lateral margins with one pair of pores anteriorly and one pair of spinular rows posteriorly; both sides of posterior margin distinctly produced, with one row of ventral spinules; hyaline frill as those of free pedigerous somites; ventral surface with one row of posterior spinules. Anal somite (Figs. 9A, 10A, 10C, 10D) small, with one pair of lateral pores, one pair of large ventrolateral pores, and one pair of ventral tube pores; ventral surface ornamented with two pairs of spinular rows posteriorly; anal opening ornamented with fine long setules; anal operculum distinctly prominent, ornamented with fine spinules, accompanied by one pair of long sensilla.
Caudal rami (Figs. 9A, 10A, 10C, 10D) elongate, slightly divergent, slightly shorter than penultimate somite, about five times as long as wide; ornamentation and setal position as preceding species; seta II about three times as long as seta I; seta III as long as caudal ramus; seta V about twice as long as seta IV; seta VI about twice as long as seta I; tri-articulate seta VII slightly longer than seta IV. Antennule (Fig. 11A) five-segmented. First segment with one small anterior protuberance with setules, one row of outer spinules posteriorly, and one row of inner setules; with one plumose inner seta accompanied by spinular row basally. Second segment with three rows of inner spinules and one row of setules on outer bump; inner margin with three plumose and four bare setae; anterior surface with two long bare setae and one small protuberance. Third segment elongate, with one row of inner spinules subdistally; with five inner setae and one long inner bare seta subdistally; distal margin ventrally produced into pedestal, with one aesthetasc and one long seta (fused basally) on its tip. Fourth segment small, with one long bare inner seta. Distal segment about four times as long as preceding segment, with ventral spinules subdistally; with three bare inner setae, one bi-articulate outer seta; distal and subdistal margins with one bare seta and four bi-articulate elements, and acrothek (one aesthetasc and two long bare setae). Antenna (Fig. 12A) three-segmented. Coxa lost during dissection process. Basis and original first endopodal segment fused forming allobasis; elongate, ornamented with two rows of abexopodal spinules (one row present on original basis and another present on original first endopodal segment). Exopod represented by one small bare seta. Free endopodal segment as long as but narrower than allobasis, ornamented with inner spinules, one row of anterior spinules subdistally, and two spinulose subdistal frills; inner margin subdistally with one delicate seta and two unipinnate spines; distal margin with two unipinnate spines, three geniculate setae, and one small seta fused basally to adjoining longest geniculate seta.
Mandible (Fig. 12B). Coxa with one bulge medially and ornamented with one row of spinules proximally; gnathobase armed with multicuspidate teeth and one unipinnate seta. Both rami incorporated into basis forming one-segmented palp, with two rows of spinules; original basis with two plumose setae distally; exopod small, with one bare seta apically; endopod larger than exopod, distally with three plumose setae.
Maxillule (Fig. 12C). Praecoxa unornamented; arthrite well-developed, distally with two bare posterior spines and two anterior spines (bearing one spinule), laterally with three bare setae, and anteriorly with two juxtaposed setae. Coxal endite elongate, with two long setae distally. Basis, exopod and endopod fused, forming single lobe. Basis ornamented with few anterior spinules subdistally and proximally; distally with one delicate and two stout setae, and laterally with two bare setae. Exopod represented by one small and one long seta, and endopod represented by two long (one bare and one uniplumose) setae. Maxilla (Fig. 12D). Syncoxa ornamented with one row of long setules along bump on outer margin, one row of spinules on inner margin, and two rows of spinules on surface; with two endites: proximal endite distally with one bare seta, two unipinnate setae (of which proximal one fused to endite basally); distal endite with one bare and two unipinnate setae. Allobasis drawn out into stout claw accompanied by one uniplumose and two bare setae. Endopod represented by two long bare setae (fused basally).
Maxilliped (Fig. 12E). Syncoxa elongate, ornamented with one row of medial spinules; subdistally with one weakly plumose seta, accompanied by one group of medial spinules at its base. Basis longer than syncoxa; outer margin convex medially, ornamented with setules; palmar margin nearby straight, weakly ornamented with setules. Endopod small, one-segmented, with one stout unipinnate claw as long as basis, accompanied by one tiny seta.
P1 (Figs. 11B, 11C). Praecoxa triangular, unornamented. Intercoxal sclerite transversely elongate. Coxa elongate, about twice as long as wide, with long outer setules. Basis longer and wider than preceding segment; outer margin with one plumose seta carrying one row of anterior spinules at its base; anterior surface with one plumose seta near inner margin; pedestal for insertion of inner ramus well-developed, unornamented. Exopod three-segmented, reaching to proximal third of enp-1; exp-1 with one row of outer spinules, one row of distal spinules, and one unipinnate and comb-like outer spine; exp-2 longest, ornamented with outer spinules and inner setules, with one geniculate outer seta; exp-3 smallest, with one row of outer spinules, one long plumose and three bare geniculate setae. Endopod prehensile, two-segmented; enp-1 elongate, slightly over twice as long as exopod, ornamented with outer spinules and inner setules; enp-2 distinctly smaller than preceding segment, with one row of outer setules, one tiny inner seta posteriorly and subdistally, and one stout spine and one geniculate seta (broken during a dissecting process) distally.
P5 (Figs. 10A, 10E, 10F) two-segmented. Baseoendopod elongate, anterior margin medially with one row of setules, and subdistally with one tube pore and one set of spinules; ventral surface with few spinules and setules, and with two subdistal tube pores; outer setophore elongate, with one long bare seta. Endopodal lobe completely incorporated into baseoendopod, represented by two fishbone-like spines. Exopod about 0.6 times as long as baseoendopod, anterior margin with two groups of spinules subdistally and one pinnate seta proximally; distal margin with one pinnate and one long plumose seta; dorsal surface with one bare seta proximally and one plumose seta subdistally; ventral surface with one tube pore subdistally.
Antennule (Fig. 14B) subchirocer, seven-segmented. First segment with one anterior protuberance ornamented with spinules, one row of outer spinules subdistally, and few inner spinules; with one plumose inner seta subdistally (lost during a dissecting process, but present in another paratype). Second segment elongate, with one row of spinules on outer bump, one transverse row of anterior spinules, one row of inner spinules, and one small anterior protuberance; with five inner setae (one uniplumose and four bare), three bare anterior setae, and one bare posterior seta. Third segment small, with seven bare inner setae. Fourth segment remarkably reduced as small sclerite, with two bare inner setae. Fifth segment swollen; inner margin ornamented with tiny spinules medially and several protuberances proximally, with one unispinulose spine; posterior surface with one uniplumose and seven bare setae near inner margin, and two long setae and one peduncle bearing one aesthetasc and one long bare seta near distal margin. Sixth segment small, slightly longer than wide, with three inner setae. Seventh segment tapering distally, slightly curved; inner margin with one bare seta; anterior surface with three bi-articulate setae; outer margin with three bi-articulate setae and one acrothek comprising one aesthetasc and two bare setae. Setal formula: 1- P3 endopod (Fig. 14C) three-segmented; enp-1 as in female; enp-2 elongate, ornamented with one stout outer spinule and one row of inner spinules, distal margin produced into curved apophysis; enp-3 elongate, about four times as long as wide, apically with two plumose setae. P5 (Figs. 14A, 14D) exopod and baseoendopod fused, forming single lobe; outer setophore elongate with one long seta; anterior margin with one row of long setules, two groups of spinules, and two tube pores; ventral surface with one tube pore (next to endopodal seta) and one row of subdistal spinules; posterior margin with one fishbone-like seta (representing endopod) and few setules; distal margin with one fishbone-like and one plumose seta subapically, and one unipinnate seta apically; dorsal surface with few long setules proximally. P6 (Fig. 14A) represented by a single plate, unarmed; both sides with a transverse gap. Caudal rami (Figs. 9D, 14A) parallel, slightly shorter than those of females, about four times as long wide.
Etymology. The epithet is derived from the Latin noun comptus meaning "hair accessory" and refers to ornamentations on the third segment of the female antennule and the ventral surface of the second abdominal somite in both sexes. It is in the nominative singular; gender masculine.
Remarks. As mentioned above in the remarks regarding B. lacuna sp. nov., the new species resembles most B. lacuna sp. nov. in terms of general body shape and mouthpart appendages. However, morphological differences are present in the ornamentation of the anal operculum, shape of the female genital double-somite, length/width ratio of the caudal rami, and sexually dimorphic features in the male P3. Detailed morphological findings can also support this separation: the dorsal protrusion on the first free prosomite has four sensillum-bearing socles in B. comptus sp. nov. Rostrum (Figs. 15A, 15B) prominent, basally fused to cephalic shield; apical tip less produced than in B. comptus sp. nov.; apically with one tube pore and two sensilla, and subapically with two pores. Cephalothorax (Fig. 15A). Integument with more cuticular ridges than in the preceding two species, medially with V-shaped inner cuticular ridge; dorsoposterior ridge welldeveloped, with four sensillum-bearing socles; dorsal surface with dented ornamentation (see insert in Fig. 15A); mediolateral extensions with blunt tip and one small protrusion posteriorly (see upper arrowhead in Fig. 15A); posterolateral corniform processes weakly curved backwardly, less developed than in the preceding two species; additional lateral projections present between mediolateral extensions and posterolateral corniform processes (see lower arrowhead in Fig. 15A). Pedigerous prosomites extended laterally as in the preceding two species; dorsal surface anteriorly with one median and two lateral cuticular ridges, one median pore, and one pair of lateral pores (absent in P2-bearing somite), and posteriorly with sclerotized protrusion carrying two subdistal sensilla and four distal sensillum-bearing socles; dorsolateral surface with one pair of tube pores in P2-P3-bearing somites; lateral margin with one pair of lateral pores in P2-and P4-bearing somites; hyaline frills crenate.   with one pair of anterior pores; dorsally with cuticular ridges and two pores; both sides of posterior margin distinctly produced, each with one row of ventral spinules; ventral surface with spinules subdistally; hyaline frill serrate. Anal somite (Figs. 15A, 16A, 16C, 16D) small, with one pair of dorsolateral pores, one pair of ventral pores, and one pair of ventral tube pores; semicircle operculum distinctly prominent, ornamented with minute processes, and accompanied by one pair of sensilla basally; pedestal for insertions of caudal rami ventrally with spinules; medial cleft weakly developed, ornamented with bunches of setules and row of spinules. Caudal rami (Figs. 15A, 16A, 16C, 16D) remarkably shorter than those of preceding two species, slightly longer than anal somite, about three times as long as wide; medial margin slightly convex; ornamentation and setal position as in the preceding species; seta II about twice as long as seta I; seta III slightly shorter than caudal ramus, about 1.9 times longer than seta II; seta V shorter than those of the preceding two species, about twice as long as seta IV; seta VI slightly longer than seta I; tri-articulate seta VII about 1.5 times longer than seta III. Antennule (Fig. 16E) five-segmented. First segment with one row of anterior spinules on bump near outer margin, three rows of inner spinules, and one plumose inner seta bearing set of minute spinules at its base. Second segment shorter than those of the preceding two species; outer margin with weak bump bearing a setular row; inner margin with three rows of spinules posteriorly; with two plumose and two bare inner setae, one plumose and two bare anterior setae, and one bare posterior seta; anterior surface without the small protuberance that is present in the preceding two species. Third segment shorter than in the preceding two species, about 2.7 times as long as wide, unornamented; inner margin with five bare setae medially and one bare seta subdistally; distal margin ventrally with peduncle bearing one aesthetasc and one long bare seta (both fused basally). Fourth segment small, with one long bare inner seta. Distal segment elongate; inner margin with three bare setae; outer margin with one bi-articulate seta subdistally; anterior surface with one bi-articulate and one bare seta subdistally; distal margin with one inner acrothek composed of one aesthetasc and two long setae, and with three bi-articulate outer setae. Setal formula: 1- Antenna (Fig. 17A) three-segmented. Coxa small, unornamented. Allobasis elongate, with two rows of abexopodal spinules; scar of original division between basis and first endopodal segment indicated by small crack. Exopod represented by one small bare seta. Free endopodal segment elongate, with one row of abexopodal spinules and two subdistal spinulose frills; lateral armature composed of two distinctly unipinnate spines and one bare seta; distal armature composed of two distinctly pinnate spines, three geniculate setae (innermost one bipinnate proximally, unipinnate distally, and basally fused to tiny seta), and one tiny seta.
Mandible (Fig. 17B). Coxa with one bulge medially and one row of spinules proximally; gnathobase armed with multicuspidate teeth and one seta. Mandibular palp with two rows of spinules; original basis distally with one long plumose and one short uniplumose seta; exopod small, incorporated into basis, with one bare seta distally; endopod larger than exopod, incorporated into basis, with three setae distally.
Maxillule (Figs. 17C, 17D). Praecoxa unornamented; arthrite (came off during dissection process) well-developed, distally with two bare posterior spines and two anterior spines bearing one spinule, laterally with three bare setae, and anteriorly with two juxtaposed setae. Coxal endite cylindrical, with two bare distal setae. Basis, exopod and endopod fused. Basis with two rows of spinules anteriorly, one small and two long bare setae distally, and one uniplumose and one bare seta subdistally. Exopod represented by a set of one small and one long seta. Endopod represented by a set of one bare and one uniplumose seta.
Maxilla (Fig. 17E). Syncoxa with long setules along outer bump, one row of inner spinules, one row of anterior spinules, and one row of posterior spinules; with two endites: proximal endite distally with one bare seta, two unipinnate setae (proximal one fused to endite basally); distal endite with one bare seta and two unipinnate setae. Allobasis drawn out into stout unipinnate claw, with three accompanying bare setae. Endopod incorporated into basis, represented by a set of two bare setae (fused basally).
Maxilliped (Fig. 17F). Syncoxa elongate, with two rows of spinules medially and one short bare seta subdistally. Basis more densely ornamented than in the preceding two species; inner margin with one row of spinules proximally; median surface with moderate and short spinules; outer margin convex, with one row of spinules. Endopod small, one-segmented, with one stout unipinnate claw slightly beyond basis, carrying one tiny seta.
P1 (Figs. 18A, 18B). Praecoxa triangular, unornamented, smaller than in the preceding two species. Intercoxal sclerite transversely elongate. Coxa about 1.6 times as long as wide, with one row of outer setules. Basis with one row of outer setules and one row of anterior spinules (near insertion of outer seta), with distinct pedestal for insertion of inner ramus; outer seta plumose; plumose inner seta inserted on anterior margin near inner margin. Exopod three-segmented, reaching to proximal third of enp-1; exp-1 with one row of outer spinules, one row of anterior spinules at base of outer spine, with one unipinnate and comb-like outer spine; exp-2 with one row of outer spinules, one large anterior spinule at base of outer seta, one row of inner spinules, and one geniculate outer seta; exp-3 small, with few outer spinules and four geniculate setae (of which innermost one longest and plumose distally). Endopod prehensile, two-segmented; enp-1 elongate, about 2.3 times longer than exopod, with one inner row of long setules proximally and one inner row of short spinules distally, and one outer row of spinules; enp-2 distinctly smaller than in preceding segment, about 2.5 times as long as wide, with one row of outer spinules, distally with one stout spine, one geniculate and one tiny seta.
P5 (Figs. 16A, 19C, 19D) two-segmented as in the preceding two species. Baseoendopod elongate; anterior margin with one row of long setules medially, and one tube pore and one row of spinules subdistally; dorsal surface ornamented with spinules; ventral surface subdistally with two fishbone-like setae (originally arising from vestigial endopodal lobe) and two tube pores; outer setophore shorter than those of the preceding two species, with one bare seta distally. Exopod about 0.8 times as long as baseoendopod; anterior margin with setules subdistally and one plumose seta proximally; dorsal surface with two plumose setae; distal margin with two long unipinnate setae; ventral surface with one tube pore subdistally.
Urosome (Figs. 15C, 20A) six-segmented, genital and first abdominal somites separated; genital somite smaller than first abdominal somite, with crenate hyaline frill; first abdominal somite with one pair of lateral pores anteriorly and two rows of ventral spinules posteriorly.
Antennule (Fig. 20B) subchirocer, seven-segmented. First segment with one row of spinules along with small anterior bump, one row of inner spinules, and three rows of posterior spinules; with one plumose inner seta subdistally. Second segment longest, with one row of minute inner spinules proximally, and one row of spinules on outer bump medially; with one plumose and two bare inner setae, one plumose and two bare anterior setae, and three bare posterior setae. Third segment small, with two delicate and four long bare inner setae, and one bare ventral seta. Fourth segment minute, with two setae. Fifth segment swollen; inner margin with one small spine proximally; posterior surface proximally with five bare setae, medially with one plumose and two bare setae, and subdistally with two long bare setae and one distinct peduncle for one long bare seta and one aesthetasc (both elements fused basally); proximal part of inner margin with fewer protrusions than in the preceding two species. Sixth segment small, with three inner setae posteriorly. Seventh segment tapering distally, with one bare inner seta, two bi-articulate anterior setae, three bi-articulate outer setae, and one outer acrothek composed of one aesthetasc and two bare setae. P3 with three-segmented endopod (Fig. 20C); enp-1 small, unornamented; enp-2 elongate, with few stout outer spinules, one row of inner setules medially, and one row of inner spinules subdistally; distal margin with one recurved apophysis; enp-3 about 2.6 times as long as wide, unornamented, with two plumose distal setae.
P5 exopod fused to baseoendopod forming single lobe as in the preceding two species (Figs. 19D, 19E); anterior margin with three groups of spinules and one tube pore; ventral surface with one tube pore medially and one row of spinules subdistally; dorsal surface with two groups of spinules; endopodal lobe represented by one fishbone-like seta; outer setophore with one long seta; original exopod with one weakly pinnate anterior seta, one plumose dorsal seta, and one small fishbone-like and one long weakly pinnate distal seta. P6 (Fig. 20A) Kim, 2013, and Bicorniphontodes sp. (the present study did not examine the latter species because only two female specimens were collected) from two sandy beaches on Udo Islet near Jeju Island. Among them, several female specimens were identified as B. bicornis sensu Kim, 2013 because they concurred with Kim's photographs (2013: Fig. 19) of the habitus, urosome and caudal rami: the posterolateral corniform processes on the cephalothorax are less developed (short and blunt); the P5-bearing somite is strongly produced laterally; and the caudal ramus is distinctly shorter than the penultimate somite. These findings imply that our specimens can be considered conspecific with Kim's material. However, detailed examination of specimens from Udo Islet revealed that they do not match Kim's description. In particular, the length of the caudal rami is approximately three times greater than its width (vs. 4-5 times), the mandibular palp consists of six setae (vs. five setae), the P2-P4 endopods are two-segmented (vs. one-segmented), and the male antennule is seven-segmented (the small fourth segment was presumably overlooked). These observations suggest that Kim (2013) misjudged the morphology of the Jeju Island materials. Thus, we decided to clarify the taxonomic assignment of B. bicornis sensu Kim, 2013 based on specimens from Udo Islet.
The Udo Islet specimens, herein named B. huysi sp. nov., are similar to B. hamatus, in terms of cephalothorax and shape of the caudal rami. Bicorniphontodes hamatus was first reported from a New Zealand harbor by Thomson (1883); the original description contained several errors in terms of female antennules, P1 and P5. Subsequently, this species was mentioned by Lang (1948), who reevaluated its thoracic leg setal armature based on other New Zealand material. This limited information regarding B. hamatus has caused taxonomic confusion (Lee & Huys, 2019), which led us to avoid comparison with our new species. Nevertheless, B. huysi sp. nov. can be distinguished from the New Zealand species by the length/width ratio of the urosomites. For example, the first abdominal somite of the new species is more wider than the genital somite, however B. hamatus has reversed trapezoidal genital double-somite. The length/width ratio of the penultimate somites are significantly different (0.9 in B. huysi sp. nov. vs. 0.6 in B. hamatus).

Cladistic analysis based on morphological characters
For the phylogenetic analysis of the species of Bicorniphontodes, a character matrix was made by scoring morphological characters as binary (0-1) or multistate (0-n). Micro-characters (e.g., surface structures and integument ornamentation) were included among the 41 chosen characters, considering recent studies that revealed their utility during morphology-based phylogenetic analyses of harpacticoid copepods (e.g., Karanovic & Lee, 2012; Karanovic & Kim, 2014). Some characters were adopted from the previous phylogenetic study of Bicorniphontodes (George, Glatzel & Schröder, 2019). The 41 selected characters are listed below (0 = plesiomorphic state, 1-2 = succeeding apomorphic states): Based on the data matrix shown in Table 1, the phylogenetic analysis of Bicorniphontodes species, with L. typicus as the outgroup, was performed using NONA software (Goloboff, 1999). Ratchet Island Hopper analysis of equally weighted characters yielded two most parsimonious cladograms with a length of 59 steps, a consistency index (Ci) of 0.76, and a retention index (Ri) of 0.63 (Fig. 21). The values of Ci and Ri  The topologies of the two cladograms are the same except for the species in a basal position (Figs. 21A, 21B). The first cladogram (Fig. 21A) implies that the most plesiomorphic species is B. clarae with two autapomorphies: the maxillipedal syncoxa is unarmed (character no. 29: 1); and the inner element on the distal margin of the P1 enp-2 is non-geniculate (character no. 31: 0). However, the basal position in the second cladogram (Fig. 21B) is B. bicornis with two autapomorphies: the cephalothorax has a smooth dorsal surface (character no. 9: 0); and the P3 enp-2 has an outer element (character no. 34: 0). A sister-group relationship of B. clarae with the remaining four species (B. horstgeorgei, B. huysi sp. nov., B. lacuna sp. nov. and B. comptus sp. nov.) is supported with more high bootstrap value (37%) than B. bicornis (27%) although both bootstraps of the basal node were lower than 50%. In both cladograms, B. horstgeorgei (from the Fiji Islands in the Pacific) was more closely aligned with the three new Korean species, supported by its moderate bootstrap value (77%). These four species shared four synapomorphies: the rostrum has a subapical tube pore (character no. 0: 0); the mediolateral extensions on the cephalothorax have protuberances on its tip (character no. 6: 1); the dorsal surfaces of urosomites have cuticular ridges (character no. 12: 1); and the first and second abdominal somites have distinct hyaline frills that are composed of projections carrying lappets (character no. 14: 1). The three new species from Korean waters were clustered together, supported by a high bootstrap value (95%), based on five synapomorphies: the maxillular exopod is represented by two setae (character no. 25: 0); all exopodal segments on the P1 are ornamented with outer spinules (character no. 30: 0); the coxae of the P2-P4 are ornamented with outer setules (character no. 33: 0); the exopod of the female P5 has a tube pore (character no. 38: 0); and the baseoendopod of the male P5 has a tube pore (character no. 40: 1).
In the Korean species clade, B. huysi sp. nov. was isolated from the B. lacuna sp. nov./B. comptus sp. nov. clade by three unambiguous autapomorphies: the cephalothorax has additional protrusions between mediolateral extrusions and posterolateral corniform processes (character no. 10: 1); the length/width ratio of the caudal rami is less than 4.5 (character no. 16: 1); and the outer element on the P4 enp-2 is distinctly reduced in length (character no. 36: 1). The sister-group relationship between B. lacuna sp. nov. and B. comptus sp. nov. was defined by only one homoplasy of the well-developed posterolateral corniform process on the cephalothorax (character no. 7: 2), which had a low bootstrap value (57%).
Bicorniphontodes lacuna sp. nov. can be distinguished from its sister taxon, B. comptus sp. nov., by the following four autapomorphies: mediolateral extensions on the cephalothorax have two small protrusions (character no. 6: 2); the division of the original genital double-somite division is marked by distinct lateral furrows (character no. 13: 1); the P3 enp-2 in the male has a tube pore (character no. 35: 1) rather than an apophysis, which is a general sexually dimorphic trait in ancorabolid copepods (see Discussion); and the baseoendopod of the male P5 has two tube pores near endopodal element (character no. 40: 0). The mediolateral extensions with a cuspidate tip (character no. 5: 1) are presumably homoplastic character states shown in B. clarae and B. lacuna sp. nov.
Two autapomorphies for B. comptus sp. nov. are present: the caudal rami show sexual dimorphism (they are divergent and elongated in the female, and parallel and relatively reduced in length in the male; character no. 15: 1) and the third segment of the female antennules has a row of inner spinules (character no. 19: 1). A homoplastic change, i.e., a pointed rostral tip (character no. 1: 1), is evident in this species.

DISCUSSION
In the frame of a revision of the genus Laophontodes, George, Glatzel & Schröder (2019) established the genus Bicorniphontodes for five species: B. bicornis, B. clarae, B. hamatus, B. horstgeorgei, and B. ornatus. They claimed that these species have a close relationship, supported by the following supposed synapomorphies: a pair of mediolateral triangular extensions and a pair of posterolateral corniform processes on the cephalothorax; crenate hyaline frills of body somites (with the exception of the anal somite); subdistal displacement of caudal setae I and II; the absence of an abexopodal seta on the antennary allobasis; and unipinnate and comb-like outer spines on the P2-P3 exp-3. Three new Korean species (B. lacuna sp. nov., B. comptus sp. nov., and B. huysi sp. nov.) also show these synapomorphies. Thus the allocation of these species to Bicorniphontodes is unproblematic.
The results of a parsimony analysis based on 41 morphological characters with L. typicus as outgroup and B. hamatus and B. ornatus excluded (Table 1; Figs. 21A, 21B), support the unambiguous synapomorphies (character nos. 2, 3, 4, 17, and 32) suggested by George, Glatzel & Schröder (2019). The presence/absence of antennary abexopodal seta was omitted from this analysis because the character state of L. typicus coincides with that of Bicorniphontodes, but there is no uncertainty regarding the morphological evidence of monophyly in this genus. With respect to the presence of posterolateral processes recurved backwardly on the cephalothorax (character no. 7), it was considered a synapomorphic trait (state = 1) in this cladistic analysis, but B. huysi sp. nov. has less developed processes (state = 0); more derived features (state = 2) are retained in B. clarae, B. lacuna sp. nov., and B. comptus sp. nov. The topology of our two cladistic trees implies that this character is secondarily evolved in B. huysi sp. nov.
Based on a morphological comparison, George, Glatzel & Schröder (2019) presumed that B. bicornis occupies the basal offshoot within the genus, considering the presence of plesiomorphic characters such as a lack of cuticular ridges on the cephalothorax and a