Monocentroptilum, Kluge, 2018

Kluge, Nikita J., 2018, A new Afrotropical genus Monocentroptilum gen. n. (Ephemeroptera: Baetidae: Protopatellata), Zootaxa 4486 (2), pp. 115-128 : 116-118

Monocentroptilum gen. n.

( Figs 1–58 )

Type species. Centroptilum badium KOpelke 1980 .

Etymology. Allusion to the single point of the costal process of hind wing; antonym to the generic name « Dicentroptilum », whose costal process has two points. Neutral gender.

Systematic position. Monocentroptilum belongs to the plesiomorphon Protopatellata Kluge & Novikova 2011; its leg structure is typical for Protopatellata: in larva, patella-tibial suture is present on middle and hind legs ( Fig. 20 ), but absent on fore leg ( Fig. 18 ); in female subimago and imago it is also expressed on middle and hind legs ( Fig. 38 ), but absent on fore leg ( Fig. 37 ) (similarly to male subimago and imago of this taxon and all other Baetidae ). As well as other Protopatellata, Monocentroptilum has following plesiomorphies: fore wing with single marginal intercalary per space ( Fig. 40 ) (in contrast to Baetovectata); larval femur without villopore (in contrast to Baetofemorata); subimaginal tarsi are covered with pointed microlepides ( Fig. 39 ); subimaginal gonostyli buds under cuticle of mature larva are curved by the « Cloeon - type », i.e. with 2nd (the longest) segment directed laterally ( Fig. 44 ).

Diagnosis. Monocentroptilum can be distinguished from other taxa of Protopatellata by combination of the following two characters:

(1)Labial palp of the « Afroptilum -type»: its 2nd segment is long and widened distally, forming a rounded convexity on median side close to base of 3rd segment; 3rd segment small, narrowed distally ( Fig. 7 ).

(2)Costal projection of hind wing is hooked and pointed, not bifurcate ( Fig. 41 ).

The single species of Monocentroptilum has unique autapomorphies, among which is the following:

(3)On femur of each larval leg, most distal setae of the row on outer margin form 2 groups, with 2 setae in each ( Figs 18, 20 ).

Other characters are described bellow, in the species description. As only one species of Monocentroptilum gen. n. is known, it is unclear, which of its characters are species-specific, and which belong to a supra-species taxon.

Comparison. Labial palp of the « Afroptilum - type », besides Monocentroptilum gen. n., is present in Afroptilum , Dicentroptilum Wuillot & Gillies 1994 , Xyrodromeus Lugo-Ortiz & McCafferty 1997b , Afroptiloides Gillies 1990a , Platycloeon Gillies & Wuillot 1997 , Peuhlella Lugo-Ortiz & McCafferty 1998a and some other taxa; probably, such shape of labial palp is initial for Baetidae . It differs both from the «chelate» type of labial palp (i.e. with prominent medio-apical projection of 2nd segment), and from labial palp with widened 3rd segment, which repeatedly appeared in various taxa of Baetidae .

In Baetidae , costal projection of hind wing either has two points, or has one point, or is blunt without points, or is absent; in many baetid taxa hind wings are absent at all. Among Anteropatellata, two-pointed costal projection is not found, and one-pointed is usual. Among Protopatellata, two-pointed costal projection occurs in Afroptilum , Dicentroptilum , Xyrodromeus , Afroptiloides , Platycloeon , Micksiops McCafferty et al. 1997 , Centroptiloides Lestage 1918 and Herbrossus McCafferty & Lugo-Ortiz (in Lugo-Ortiz & McCafferty) 1998a ; according to my unpublished data, costal projection of Peuhlella is also two-pointed, while it was described as having one point.

Among Protopatellata, one-pointed costal projection is present in Crassabwa /g1 (incl. Susua ), Dabulamanzia Lugo-Ortiz & McCafferty 1996a , Rheoptilum Gattolliat 2001 , Nesoptiloides Demoulin 1973 , Guloptiloides Gattolliat & Sartori 2000 (if association of its larvae and imagoes is correct) and in that representatives of Anafroptilum Kluge 2012a and Rhithrocloeoninae Kluge 2012b, which retain hind wings. These taxa differ from the new genus Monocentroptilum gen. n. at least by the following characters: Crassabwa /fg1 differs by «chelate» labial palp and single subapical seta on larval femur ( Kluge et al. 2017). Dabulamanzia and Anafroptilum differ by widened 3rd segment of labial palp. Rhithrocloeoninae differ from all other taxa by peculiar structure of gonostyli and mode of their folding in larva ( Kluge 2015). Larvae of Rheoptilum are highly modified as the « Acentrella - type », and larvae of Nesoptiloides and Guloptiloides are highly modified as carnivorous.

Some taxa have no hind wings, and initial structure of their hind wings is unknown; among Protopatellata these are Potamocloeon Gillies 1990b (= Maliqua Lugo-Ortiz & McCafferty 1997c ) and Indocloeon Müller-Liebenau 1982 ; the same in the genera of unknown systematic position Demoulinia Gillies 1990a and Edmulmeatus Lugo- Ortiz & McCafferty 1997a. Among them, Potamocloeon differs from Monocentroptilum gen. n. by widened 3rd segment of labial palp and other characters; Indocloeon , Demoulinia and Edmulmeatus differ from Monocentroptilum gen. n. by «chelate» labial palp.

Some taxa of Protopatellata have hind wings, but are known only as larvae, so structure of their costal projection is unknown. These are Acanthiops Waltz & McCafferty 1987 , Nesydemius Lugo-Ortiz & McCafferty 1998b , Scutoptilium Gattolliat 2002 and Echinopus Gattolliat 2002 . Among them, Acanthiops has highly modified larval structure. Nesydemius seems to be closely related to Dabulamanzia and differs from Monocentroptilum by widened 3rd segment of labial palp. The genera Scutoptilium and Echinopus , described from Madagascar, are regarded to be related one to another, based on presence of transverse subapical row of setae on their femora ( Gattolliat 2002); in this respect they both differ from Monocentroptilum gen. n. However, Echinopus has some similarities with Monocentroptilum badium : similar structure of mouth parts with elongated mandibles ( Gattolliat 2002: Figs 28–32 ), claws with reduced posterior row of denticles and two subapical setae (ibid., Fig. 34 ) and tergalii of the unusual «inverted» shape (ibid., Fig. 35 ) (see description of M. badium below).

Distribution. Afrotropical (known from Congo and Uganda).

Composition. One species , Monocentroptilum badium (Kopelke 1980) comb. n.

Figures

FIGURES 1–4. Larva Of Monocentroptilum badium. 1, Lateral view (arrOws shOw prOtuberances On mesOnOtum; 2, exuviae Of right half Of prOnOtum and mesOnOtum; 3, exuviae Of abdOminal sterna and terga; 4, subimaginal sterna and terga extracted frOm mature larva (tO shOw hypOdermal cOlOratiOn).

FIGURES 5–9. Larva Of Monocentroptilum badium. 5, labium; 6, maxilla (dOrsal view); 7, labium (at left ventral view, at right dOrsal view); 8–9, left and right mandible. AbbreviatiOns: ds1–ds3, dentisetae.

FIGURES 10–27. Larva Of Monocentroptilum badium. 10–16, tergalii Of I–VII pairs; 17, margin Of tergalius; 18, fOre leg; 19, claw (view frOm anteriOr side); 20, hind leg; 21, setae On apex Of its tibia; 22, claw (view frOm inner side); 23, exuviae Of half Of prOnOtum and mesOnOtum (thick line shOws area enlarged On Fig. 28); 24, setae On mesOnOtum; 25, seta On paired prOtuberances; 26, hind prOtOpterOm (the same scale as Fig. 23); 27, part Of head with clypeus, bases Of antennae, median Ocellus and frOntal suture.

FIGURES 28–31. Larval exuviae Of Monocentroptilum badium. 28, fragment Of mesOnOtum (Outlined On Fig. 23); 29, fragment Of cercus; 30, fragment Of tergum VIII; 31, paraprOct (all at the same scale).

FIGURES 32–39. Monocentroptilum badium. 32, anteriOr part Of male imagO with subimaginal exuviae; 33, head and thOrax Of male imagO; 34, abdOmen Of male imagO (spread On slide); 35, had and thOrax Of female imagO; 36, female imagO; 37–38, exuviae Of fOre and hind legs Of female subimagO; 39, exuviae Of hind tarsus Of female subimagO.

FIGURES 40–43. Monocentroptilum badium. 40–41, fOre and hind wings; 42, head and mesOnOtum Of male imagO; 43, subimaginal exuviae Of left pOstsubalar sclerite and laterOpOstnOtal crest.

FIGURES 44–47. Male genitals Of Monocentroptilum badium. 44, develOping subimaginal genitals, fOlded under larval cuticle; 45, subimaginal exuviae Of gOnOstyli; 46, imaginal genitals Of the same specimen (gOnOduct shOwn by dOtted lines, muscles shOwn by interrupted lines, internal parts Of penis shOwn by interrupted lines and dOtted); 47, its left unistyliger, tO shOw muscles. AbbreviatiOns: 1–3, segments Of gOnOstylus; gv, gOnOvectis; m.sg, median sternO-styligeral muscle; pgs, larval prOtOgOnOstylus; usg, unistyliger.

FIGURES 48–52. Male imaginal genitals Of Monocentroptilum badium. 48–49, specimen with prOtracted gOnOvectes: 48, with fOcus On internal parts, including gOnOvectes; 49, with fOcus On ventral surface, including unistyligers and median styligeral sclerite; 50–51, specimen with retracted gOnOvectes: 50, with fOcus On gOnOvectes and penial bridge; 51, with fOcus On median styligeral sclerite and median sternO-styligeral muscle; 52, gOnOstyli.

FIGURES 53–58. Eggs Of Monocentroptilum badium.