Dimorphipodia changi, Lee & Huys, 2019

DIMORPHIPODIA CHANGI View in CoL SP. NOV.

( FIGS 2–8)

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Type locality: South Korea, south coast, Stn A 8 (33°59.851′N, 128°30.413′E); fine sand with high silt content; depth 105.7 m ( Fig. 1) GoogleMaps .

Type material: Holotype ♀ dissected on ten slides (reg. no. NIBRIV0000829704 ), allotype ♂ dissected on nine slides (reg. no. NIBRIV0000829705 ), remaining paratypes (three ♀♀, two ♂♂) preserved in formalin (reg. no. NIBRIV0000829706 ); all type specimens collected on 8 June 2015 from type locality.

Description of female: Body length measured from anterior margin of rostrum to posterior margin of caudal rami 611–664 μm (mean = 641 μm; N = 4; holotype = 642 μm). Body ( Fig. 2A) cylindrical, without clear demarcation between prosome and urosome; urosome slightly narrower than prosome, maximal width (128 μm) measured at P3-bearing somite. Integument moderately chitinized. Cephalothorax with marked bilateral constrictions separating posterior third from anterior two-thirds; with paired elongate frontolateral horns immediately posterior to insertion sites of antennules at anterior outer corners ( Fig. 2A); each horn ending in long sensillum and bearing minute denticles and few proximal setules (see inset in Fig. 2A); dorsal surface of cephalothorax with three paires of conspicuous tube-pores; frontal margin concave, bearing small median rostrum; lateroventral margin forming setulose lobate outgrowth (not figured). Posterior processes absent. Most sensilla on cephalic shield branched.

Rostrum ( Fig. 2B): Fused to cephalic shield; small, trapezoid in shape; dorsal surface with paired plumose sensilla subapically; ventral surface with paired, pointed, membranous projections subapically and long median tube-pore.

Somites bearing legs 2–5 ( Fig. 2A): With well-developed pleurotergites forming distinct lateral expansions so that somites are clearly demarcated in dorsal aspect; separated by distinct membranous zones; hyaline frills plain. Somites bearing legs 2–4 with paired, slightly backwardly produced processes dorsally and paired setular tufts lateroventrally ( Fig. 2C); processes relatively short, covered with small denticles and bearing apical sensillum; somites with paired tube-pores dorsolaterally and median tube-pore dorsally.

Original segmentation of genital double-somite indicated by lateral bulbous projections in anterior half and pairwise pattern of tube-pores and sensilla ( Fig. 2A, D); projections ornamented with few spinules and bearing conspicuous apical sensillum; second pair of smaller lateral projections present in posterior half, with apical sensillum; posterior margin with continuous row of setular extensions and pair of closely set tube-pores midventrally ( Fig. 2A, D). Genital field ( Fig. 2D) with medially fused gonopores, opening via common midventral slit covered by genital operculum derived from fused vestigial sixth legs; each leg 6 with one naked seta. Copulatory pore moderately large, flanked by paired tube-pore triplet, immediately posterior to each gonopore.

Second and third abdominal somites: With few spinules midventrally near posterior margin ( Fig. 2D); both somites with paired tube-pores ventrolaterally and with a continuous row of fine setular extensions around hind margin; dorsal surface of second somite with paired tube-pores, that of third somite with single tube-pore and few spinules medially ( Fig. 2A). Anal somite partly cleft medially ( Fig. 2D); with paired tube-pores dorsolaterally and long sensilla arising from socles either side of anal operculum; paired tube-pores and small spinules present around ventral hind margin near bases of caudal rami; anal operculum rounded, furnished with long, fine setules; anal frill deeply incised, forming long setular extensions ( Figs 2A, D, 4A). All sensilla on urosomites sparsely plumose, often giving them a branched appearance.

Caudal rami: Elongate, divergent and slightly bent inwards, cylindrical, slightly shorter than last three urosomites combined ( Figs 2D, 4A); with few spinules around insertion sites of setae I–III ( Fig. 2D), VI and VII ( Fig. 4A); with four tube-pores and seven setae. Setae III–VII arranged around posterior margin of ramus; seta I minute, positioned ventral to seta II (see right inset of Fig. 2D); setae II–III unipinnate; setae IV and VI naked; seta V well developed, ornamentation unconfirmed; seta VII tri-articulate at base and arising from minute dorsal pedestal. Dorsolateral tube-pore positioned in proximal quarter of ramus; remaining three tube-pores arising near ventral posterior margin, outer one much wider than inner ones and represented by flaccid scale-like extension (indicated by * in Fig. 2D).

Antennule ( Fig. 3A): Four-segmented. Dorsal surface of segments 1–3 covered with fine setules. Segment 1 longest, with long, fine spinules along distal half of anterior margin; with bipinnate seta sub-apically. Segment 3 second longest, with aesthetasc (length 135 μm). Segment 4 with apical acrothek consisting of short aesthetasc (length 25 μm) and two slender setae. Armature formula: 1-[1 pinnate], 2-[4 + 3 pinnate], 3-[5 + 1 pinnate + (1 + ae)], 4-[9 + acrothek].

Antenna ( Fig. 3B): Slender and elongate. Coxa represented by well-developed sclerite. Basis and proximal endopod segment fused, forming allobasis; membranous insert halfway along outer margin marking original position of exopod; exopod completely absent; abexopodal margin with few spinules in basal half; with two short, pinnate setae. Free endopodal segment with two distal surface frills and spinule row along distal outer and proximal medial margins; lateral armature consisting of two unipinnate spines and one bare seta; distal armature consisting of two unipinnate spines and three geniculate setae with pinnules around geniculation; outermost geniculate seta with one spinule distally and fused basally to vestigial seta and with tube-pore arising from its base.

Mandible ( Fig. 3C): Coxa robust, with several spinule rows proximally; gnathobase with two multicuspidate teeth and series of thin incised blades; with one unipinnate seta at dorsal corner. Palp well developed, one-segmented; with one bipinnate seta along inner margin (representing basal element), three apical setae (representing incorporated endopod) and one bipinnate seta along outer margin (representing exopod); inner margin with few strong spinules.

Maxillule ( Fig. 3 D): Praecoxal arthrite subrectangular, with two setae on anterior surface and spinule row on posterior surface; distal armature consisting of three pinnate setae and six spines (outermost one unipinnate, others naked); outer margin of praecoxa with few spinules as indicated. Coxa with spinules round outer margin; endite with one unipinnate spine and one bare seta. Basis with three spinule rows; basal endites indistinguishable, represented by one short and one long naked seta and two unipinnate spiniform elements. Rami completely incorporated into basis; exopod represented by one short and one long seta; endopod represented by one bipinnate and two naked setae.

Maxilla ( Fig. 3E): Syncoxa with two groups of strong spinules along outer margin and additonal patches of small spinules as figured; with two endites arising from membranous area; proximal endite with one strong bipinnate spine fused at base to endite and two setae; distal endite with two pinnate spines (distal one fused at base to endite) and one small, unipinnate seta. Allobasis drawn out into claw bearing few strong spinules subdistally; accessory armature consisting of two bare setae and one unipinnate spine. Endopod one-segmented, minute, with two naked setae.

Maxilliped ( Fig. 3F): Subchelate, slender and elongate. Syncoxa with one bipinnate seta surrounded by spinules around its base; with few setules around outer margin. Basis with strong spinules along outer margin, unarmed. Endopod drawn out into long narrow, curved claw; claw smooth with one accessory seta at base.

P1 ( Fig. 4B): Intercoxal sclerite wide and narrow; without ornamentation. Praecoxa represented by well-developed sclerite. Coxa small, trapezoid. Basis transversely elongate, with conspicuous anterior tube-pore near articulation with coxa; anterior surface covered by setules and spinules as figured; with bipinnate outer spine and plumose inner seta. Exopod two-segmented. Exp-1 shortest, with few spinules/setules along outer margin; outer spine long and bipinnate, but shorter than exp-2. Exp-2 with fine setules along outer and inner margins; with four geniculate setae (the innermost one plumose) and one pinnate outer spine; outer distal corner with very long tube-pore. Endopod absent; original position indicated by slightly membranous area (arrowed in Fig. 4B).

P2–P4 ( Fig. 5A–C): Intercoxal sclerites wide and narrow, lacking surface ornamentation. Praecoxae represented by well-developed sclerites (not figured for P2), with fine setules in P3 ( Fig. 5B). Coxae trapezoid, with few spinules anteriorly. Bases transversely elongate; outer margin with long setules in proximal half, spinules in distal half and large, basally reinforced, anterior tube-pore; additional patches of fine setules on anterior surface; outer distal seta bipinnate, arising from a tiny, posteriorly displaced setophore. Exopods three-segmented; outer and inner margins with fine setules as figured; outer spines elongate and bipinnate. P2 endopod absent, position indicated by slightly membranous area (arrowed in Fig. 5A). P3–P4 endopod ( Fig. 5B, C) reduced, two-segmented; enp-1 tiny, unarmed; enp-2 longer with two apical setae, with few setules along inner and outer margins in P3. Armature formula of P2–P4 as in the generic diagnosis.

P5 ( Fig. 4C): One-segmented; original segment boundary between baseoendopod and exopod marked by minute membranous area (arrowed in inset of Fig. 4C). Baseoendopod with long setules along outer margin and large subdistal tube-pore; setophore reduced, fused to baseoendopod, bearing pinnate outer basal seta. Endopodal lobe absorbed into basis, represented by one conspicuous tube-pore and two tiny naked setae. Exopodal lobe long and slender; with fine setules and one subapical tube-pore on anterior surface; inner spine finely serrated; with one bipinnate seta distally and three bipinnate outer setae (proximal and middle ones displaced posteriorly).

Description of male: Distinctly smaller and more slender than ♀. Body length measured from anterior margin of rostrum to posterior margin of caudal rami 373–453 μm (mean = 417 μm; N = 3; dissected paratype = 453 μm). Sexual dimorphism in body size, degree of development of body processes, antennule, P2– P6, urosomal segmentation and caudal ramus length.

Frontolateral horns and body processes on somites bearing P2–P4 relatively smaller than in ♀ ( Fig. 6A). Ornamentation pattern of processes and sensilla essentially as in ♀. Urosome ( Figs 6A, 7B) slender; genital somite without pleural extensions; ornamentation of abdominal somites as in ♀.

Caudal rami ( Fig. 7A, B): Slightly shorter than in ♀; armature and ornamentation as in ♀, including appearance of flaccid scale-like outer tube-pore (indicated by * in inset of Fig. 7B).

Antennule ( Fig. 6B): Six-segmented, geniculation between segments 5 and 6; aesthetasc present on segment 5 (length 160 μm) and as part of apical acrothek on segment 6. Segment 1 longest, with few long spinules along anterior margin. Segment 4 represented by a U-shaped sclerite. Segment 5 not markedly swollen. Armature formula: 1-[1 bipinnate], 2-[2 bipinnate + 5], 3-[4 + 2 vestigial], 4-[1 vestigial], 5-[7 + 1 spine + (1 + ae)], 6-[7 + acrothek]. Apical acrothek consisting of two setae and aesthetasc (length 29 μm).

P1 ( Fig. 6C): As in ♀.

P2–P4 ( Figs 7C, 8A, B): Inner seta of exp-2 much longer than in ♀. Exp-3 with one (P2, P4) or two (P3) plumose inner setae; apical elements longer than in ♀. P3 endopod ( Fig. 8A) three-segmented; enp-1 slightly longer than wide; enp-2 elongate, with sparse spinules along inner and outer margins, anterior distal surface produced into small recurved spinous apophysis; enp-3 with two apical setae, outermost seta proportionally longer than in ♀. Armature formula of P2–P4 as follows:

P5 ( Fig. 7D): Two-segmented: Baseoendopod with large distal tube-pore; setophore reduced, fused to baseoendopod, bearing pinnate outer basal seta. Endopodal lobe absorbed, represented by two conspicuous tube-pores and two minute setae. Exopod completely defined at base, elongate; with fine setules on anterior surface; with finely serrated spine and long subdistal tube-pore along inner margin, one bipinnate spine apically, and three pinnate setae along outer margin (middle one shortest and displaced posteriorly).

P6 ( Fig. 7B): Sixth pair of legs asymmetrical, with only one functional member, represented by reduced membranous flap; other member fused to somite; without armature.

Spermatophore ( Fig. 7B): Ovoid, 40 μm.

Etymology: The species is dedicated to Professor Cheon Young Chang (Daegu University), mentor of the senior author, in recognition of his major contributions to copepod systematics and taxonomy.

R e m a rk s: C o n r o y - D a l t o n (2 0 0 1) p r o p o s e d t h e Ceratonotus group for five genera in the subfamily A n c o r a b o l i n a e, i.e. C e r a t o n o t u s S a r s, 1 9 0 9, Dorsiceratus Drzycimski, 1967 , Polyascophorus George, 1998 , Arthuricornua Conroy-Dalton, 2001 and Touphapleura Conroy-Dalton, 2001 . The group was defined by the following suite of synapomorphies: (1) body somites virtually cylindrical; (2) somites bearing P2–P4 with paired backwardly produced (latero)dorsal processes; (3) rostrum small, without apical elongation anterior to insertion point of sensillae; no sexual dimorphism where males are known; (4) antennulary segment 1 elongate (fused to segment 2 in Ceratonotus , but equivalent portion also elongate); (5) P1–P4 endopods reduced, with armature elements always arranged around apex of terminal segment; (6) P 3 male with three-segmented endopod; apophysis arising from middle segment; and (7) P5 endopodal lobe in both sexes absorbed into protopod; with reduced armature, represented by at most two setae ( Conroy-Dalton, 2001). The Ceratonotus group saw the addition of Dendropsyllus Conroy-Dalton, 2003a , a new genus proposed for two species previously allocated to Ceratonotus , i.e. Ceratonotus antarcticus George & Schminke, 1998 and Ceratonotus magellanicus George & Schminke, 1998 ( Conroy-Dalton, 2003a). Finally, George (2006b) added both Echinopsyllus Sars, 1909 and Pseudechinopsyllus George, 2006b , a course of action subsequently corroborated by a phylogenetic analysis ( Wandeness et al., 2009), although synapomorphies supporting the common ancestry of the remaining members of the Ceratonotus group could not be identified, and the evidence underpinning the sister-group relationship between Echinopsyllus and Pseudechinopsyllus does not appear to be particularly robust.

In their revision of the Ancorabolus group, Conroy-Dalton & Huys (2000) noted a remarkable overall consistency in the number of cephalothoracic sensillae, whereas the number, size and shape of spinous processes on the cephalothorax varied considerably between genera. Analysis of this variation against the background of a conserved sensillar reference pattern unequivocally determined the homology of processes between genera. Likewise, the position, shape and number of horns and processes on the cephalothorax (and the trunk) can be radically divergent between genera of the Ceratonotus group ( Fig. 9). Failure to understand the homology between these processes has resulted in erroneous interpretations of their morphology and/or confusion surrounding the relationships of certain genera. In its most elaborate form (discounting the Echinopsyllus condition from the discussion below), the cephalothorax displays four pairs of outgrowths: (1) frontolateral horns (FLH); (2) posterior laterodorsal processes (CLDP); (3) posterior lateroventral processes (CLVPp); and (4) anterior lateroventral processes (CLVPa). This pattern is fully expressed in Dendropsyllus , Pseudechinopsyllus and at least some members of Ceratonotus and Polyascophorus , whereas in other genera one or more pairs are absent.

Frontolateral horns (FLH) originate from the anterolateral corners of the cephalothorax and invariably bear a sensillum at the apex and typically one or two sensilla and a tube-pore at the base. They can be considered the positional homologues of the first pair of lateral cephalothoracic processes (L1) in the terminology of Wandeness et al. (2009). Horns are moderately developed in Pseudechinopsyllus , completely absent in both Dorsiceratus and Touphapleura , and represented by long processes in the remaining genera of the Ceratonotus group ( Fig. 9). In Arthuricornua , Polyascophorus and Dimorphipodia , the frontolateral horns are practically straight and directed at a virtually right angle to the longitudinal body axis, whereas in Ceratonotus and Dendropsyllus they are typically curved and backwardly directed. In some species of Ceratonotus , a pair of small, pointed or conical projections arise from the frontal margin of the cephalothorax (as in Ceratonotus concavus Conroy-Dalton, 2003a , Ceratonotus steiningeri George, 2006a , Ceratonotus tauroides George, 2006a and Ceratonotus vareschii George, 2006a ). These projections (= anterior horn-like processes sensu Gómez & Díaz, 2017) carry the sensilla typically found on either side of the frontal tube-pore and are therefore rostral in origin. Their presence appears to be associated with species whose rostral margin has secondarily become distinctly concave. Similar sensillate tubercles are present in some Dendropsyllus species (e.g. Dendropsyllus californiensis Gómez & Díaz, 2017 ; Gómez & Díaz, 2017: fig. 8C).

Most members of the Ceratonotus group exhibit a pair of laterodorsal processes (CLDP) arising from the posterior half of the cephalothorax. Exceptions include the genera Touphapleura and Dimorphipodia and two species in the genus Polyascophorus [ Po. gorbunovi ( Smirnov, 1946) and Po. martinezi George, 1998 ]. In some species, such as Dendropsyllus thomasi Conroy-Dalton, 2003a , Dendropsyllus kimi and Pseudechinopsyllus sindemarki George, 2006b , the processes assume a slightly more dorsal position ( Conroy-Dalton 2003a: fig. 9A; George 2006b: fig. 19A; fig. 10A herein). They are relatively short and lack ornamentation in Ps. sindemarki , spinulose along their entire length in members of Dorsiceratus and Arthuricornua and dendroid in representatives of Ceratonotus and Dendropsyllus . Conroy-Dalton (2001) postulated that the processes have migrated from their ancestral laterodorsal position to a lateroventral location in the two Arctic Polyascophorus species ( Polyascophorus gorbunovi and Polyascophorus martinezi ). It was assumed that during this process they had also become apically bifurcate, forming a short anterior and a long posterior branch, and had undergone excessive development, becoming the largest pair of body processes. The recent discovery of Polyascophorus monoceratus George, Wandeness & Santos, 2013 has proved this scenario to be incorrect, because both laterodorsal and bifurcate lateroventral processes are expressed in this species (George et al., 2013). The posterior pair of (latero)dorsal processes are the positional homologues of the second pair of dorsal cephalothoracic processes (DII) in the system devised by Wandeness et al. (2009).

A pair of posterior lateroventral processes (CLVPp), each bearing an apical sensillum, is expressed in Ceratonotus , Dendropsyllus , Pseudechinopsyllus and Polyascophorus , but only in the last genus are they bifurcate. In Dendropsyllus , the processes are very large, being smooth [ Dendropsyllus antarcticus ( George & Schminke, 1998) ] or more commonly dentate (remaining species), whereas in Ceratonotus their size and form vary considerably between species. In Ceratonotus pectinatus Sars, 1909 , Ceratonotus thistlei Conroy-Dalton, 2003 and Ceratonotus vareschii , the lateroventral processes are small and conical ( Conroy-Dalton, 2003a: figs 1C, 5B; George, 2006a: fig. 16). Conversely, in C. concavus ( Conroy-Dalton, 2003a: fig. 7C), C. tauroides ( George, 2006a: fig. 2A) and Ceratonotus elongatus Gómez & Díaz, 2017 ( Gómez & Díaz, 2017: fig. 2A), the conical processes are much larger and clearly discernible in dorsal aspect. In C. steiningeri , the processes are elongate and dentate ( George, 2006a: fig. 10A, C), resembling the typical Dendropsyllus condition. The posterior lateroventral processes correspond to the third pair of lateral cephalothoracic processes (LIII) in the terminology of Wandeness et al. (2009).Their claim that the presence of abdominal somites 1–3; AST4, lateral setulose/spinulose tuft on anal somite; CLDP, cephalothoracic laterodorsal process; CLVPa, cephalothoracic lateroventral process (anterior pair); CLVPp, cephalothoracic lateroventral process (posterior pair); DT1, dorsal sensillate tubercle on genital somite (anterior half of genital double-somite); DT2, dorsal sensillate tubercle on abdominal somite 1 (posterior half of genital double-somite); DT3, dorsal sensillate tubercle on abdominal somite 2; DP1–4, dorsal processes on somites bearing P2–P5; DP5, dorsal process on first abdominal somite (posterior half of genital double-somite); FLH, frontolateral horn on cephalothorax; GST, lateral setulose/spinulose tuft on genital somite (anterior half of genital double-somite); PCST, posterior cephalothoracic setulose/spinulose tuft; TST1–4, lateral setulose/spinulose tufts on thoracic somites 3–6 (somites bearing P2–P5). Habitus drawings adapted from Conroy-Dalton (2001, 2003a), George (1998, 2006a, b), George et al. (2013) and present study.

these processes is a synapomorphy for Echinopsyllus + Pseudechinopsyllus is therefore incorrect.

Some members of the Ceratonotus group have a propensity for developing a second extension of the free lateroventral pleural margins of the cephalothorax, usually in the area around the base of the antenna. In Arthuricornua , Dorsiceratus and Dimorphipodia , this is represented by a lobate expansion, which typically bears a tuft of setules ( Conroy-Dalton, 2001; this study); the condition in Touphapleura is yet to be confirmed. Further extension has resulted in the formation of small, conical protuberances, here referred to as the anterior lateroventral processes (CLVPa). Each conical process has an apical sensillum and two sensilla plus a tube-pore at its base and is often found in close proximity to the posterior lateroventral processes. The presence of such processes is not uniformly distributed throughout the genera Ceratonotus , Dendropsyllus and Polyascophorus . The genus Ceratonotus contains members that clearly lack them, such as C. pectinatus and C. thistlei ( Conroy-Dalton, 2003a: figs 1C, 5B), and others that display them, such as C concavus ( Conroy-Dalton, 2003a: fig. 7C) and Ceratonotus vareschii George, 2006a ( George, 2006a: fig. 16). Within Dendropsyllus , anterior lateroventral processes appear to be absent in De. antarcticus but are either minute, as in De. thomasi ( Conroy-Dalton, 2003a: Fig. 9B), or moderately developed, as in Dendropsyllus magellanicus ( George & Schminke, 1998: fig. 1; George, 2006a: fig. 21A), De. californiensis ( Gómez & Díaz, 2017: fig. 7A) and De. kimi (present study: Fig. 10). Within Polyascophorus , they have been documented only for Polyascophorus martinezi ( George, 1998: fig. 1A). In Pseudechinopsyllus , the processes have undergone extreme development, resulting in the displacement of the basal tube-pore onto the process. The anterior lateroventral processes can be considered the positional homologues of the second pair of lateral cephalothoracic processes (LII) in the scheme of Wandeness et al. (2009). This weakens their claim that the presence of these processes is a synapomorphy supporting the sister-group relationship between Echinopsyllus and Pseudechinopsyllus .

The new genus Dimorphipodia belongs to a lineage of genera that lacks paired dorsal processes on the urosome and both anterior and posterior lateroventral processes on the cephalothorax, including Touphapleura , Dorsiceratus and Arthuricornua , which all have dorsal extensions on the pedigerous somites bearing P2–P4 ( Fig. 9). Within this lineage, it is morphologically similar to Arthuricornua , which was proposed for its type and only species, Arthuricornua anendopodia , collected in the San Diego Trough in the northeastern Pacific ( Conroy-Dalton, 2001). Both genera can be considered sister taxa in the Ceratonotus group, because they share: (1) a cephalothorax, which is bilaterally constricted in its posterior half [other genera that show a similar constriction display it in the anterior half of the cephalothorax, such as Ceratonotus , Dendropsyllus and Pseudechinopsyllus ]; (2) paired elongate, frontolateral horns, which are directed at virtually a right angle to the longitudinal body axis [absent in Touphapleura and Dorsiceratus ; both genera have anterior cephalothoracic setulose/ spinulose tufts (ACST) at the anterior corners, which are lacking in Arthuricornua and Dimorphipodia ]; (3) paired lateral, rounded protuberances (with spinules/ setules) (GST) on the anterior half of genital double-somite ♀ [similar setulose/spinulose tufts are found on the urosome in Touphapleura and Dorsiceratus , but the pattern differs (cf. AST1–2; Fig. 9)]; (4) the complete absence of endopods on P1–P2; (5) an elongate P5 exopod, which is fused to the baseoendopod in the ♀, but free in the ♂ and bears five elements, of which the middle outer spine is reduced and displaced to the posterior surface; and (6) a rounded anal operculum furnished with long, fine spinules.

Dimorphipodia can be differentiated from Arthuricornua by the following characters: (1) cephalothorax without paired laterodorsal processes near posterior margin (vs. present); (2) P2–P4 exp-3 with sexually dimorphic armature, showing no inner setae in the female (022), but with one inner seta in the male on P2 and P4 (122) and two inner setae on P3 (222) (the male condition is therefore identical to that of both sexes in Arthuricornua anendopodia ; Table 2); (3) pedigerous somites bearing P2–P4, with setular tufts on the expanded pleural areas (vs. without); and (4) pedigerous somites bearing P2–P4, with moderately developed dorsal processes (vs. well developed and backwardly directed).