Dichotomius (Cephagonus) Luederwaldt 1929

Nunes, Rafael V. & Vaz-de-Mello, Fernando Z., 2019, Taxonomic revision of Dichotomius (Cephagonus) Luederwaldt 1929 and the taxonomic status of remaining Dichotomius Hope 1838 subgenera (Coleoptera: Scarabaeidae: Scarabaeinae: Dichotomiini), Journal of Natural History 53 (37), pp. 2231-2351 : 2247-2259

publication ID

https://doi.org/ 10.1080/00222933.2019.1692088

DOI

https://doi.org/10.5281/zenodo.3671956

persistent identifier

https://treatment.plazi.org/id/C740D609-2A73-BB58-FE87-E5F2E697288D

treatment provided by

Valdenar

scientific name

Dichotomius (Cephagonus) Luederwaldt 1929
status

 

Dichotomius (Cephagonus) Luederwaldt 1929 new status

( Figures 1 – 2 View Figure 1 View Figure 2 ı 4 – 47)

Pinotus ı Harold 1869 ı p. 1009

Dichotomius (selenocopris) Martínez 1951 ı p. 140

Dichotomius (selenocopris) Vaz-de-Mello 2000 ı p. 193

Dichotomius (selenocopris) Vaz-de-Mello et al. 2011 ı p. 5

Dichotomius (selenocopris) Nunes & Vaz-de-Mello 2016.

Type species. Pinotus fissus Haroldı 1867 ı here designated. Luederwaldt (1929) did not assign a type species for Cephagonus ı howeverı he placed all species in the subgenus close to D. fissus based on their clypeo-genal angle. Luederwaldt kept positioning new species of Cephagonus close to D. fissus ı in what he was followed by Vernalha (1952); Pereira and D ’ Andretta (1955) and Vulcano et al. 1976. Our designation of D. fissus as type species of Cephagonus is based on three reasons: 1) the constant use of this name to refer to Dichotomius with clypeal genal angle; 2) both males and females have clear and easily observable diagnostic characters common to all Cephagonus and 3) to fix the name usage.

Diagnosis. Lamellate antennae ( Figure 7 View Figure 7 (f))ı mandible lacking sclerotised incisory teeth ( Figure 7 View Figure 7 (a)) and clypeus expanded (covering mouth parts and with many types of shapes and modifications) place Cephagonus in Scarabaeinae subfamilyı Scarabaeidae family of Coleoptera order of insects. Among the Scarabaeinaeı the following combined characters: lacking of visible scutellum; lacking of trocantofemoral pit; meso and meta tibiae strongly enlarged towards apex and all tarsi bearing tarsal claws place Cephagonus in tribes Coprini or Dichtomiini s. str.ı according to Montreuil (1998) and Tarasov and Génier (2015) respectively. Among both tribal definitionsı Cephagonus is separated of the other Dichotomius subgenera by the following combined characters: clypeal ventral process transversely carinateı strongly bifurcate at apex ( Figure 7 View Figure 7 (e)); clypeus with two acute and conspicuous teeth; clypeal or genal external border straight; nine antenna segments ( Figure 7 View Figure 7 (f)); anterior margin of mesepisternum ending in an acute angle reaching the pseudoepipleuron ( Figure 8 View Figure 8 (a)); pro-tibiae inner angle acute or spiniform; meso- and metatibiae lacking transverse carina; abdominal ventrites 2 to 6 with ocellate punctures along anterior margin and with groups of setae concentrated on both sides and females sixth abdominal ventrite bearing modifications at medial portion ( Figures 8 – 10 View Figure 8 View Figure 9 View Figure 10 ) and/or pygidium swollen. Cephagonus is Neotropicalı with species occurring from Panama to Argentina ( Figure 11 View Figure 11 ).

Description ( Figures 1–2 View Figure 1 View Figure 2 ). Dorsal colour dark brown to blackı having copper or blue reflections on an elytral basis. BL: 9 – 24 mm. PW: 5 – 13 mm. Head (dorsal): anterior margin of clypeus strongly emarginate medially producing two acute teeth. Scatteredı short setae present along the clypeal marginı more abundant on clypeal teeth. Clypeal teeth curved upwards in lateral view. Clypeo-genal suture is distinct. Eyes present dorsallyı inter-ocular space having at least 6x the eye diameter. Gena posterior angle obtuse; genae not expanded in relation to clypeal margin. Head (ventral and mouth parts) ( Figure 4 View Figure 4 (a-d)): head margin bearing short scattered setae throughout its extension. Ventral clypeal process carinateı strongly bifurcate apically ( Figure 7 View Figure 7 (e)). Antenna 9-segmentedı 1st segment bearing the combined length of 2nd to sixth segmentsı 2nd segment with a medial constrictionı at least one setae present at the base of each segment. Antenna club lamellateı light beige to brown tumescence. Lamella larger at the baseı getting narrower towards the apex (lamellae 2 and 3) ( Figure 7 View Figure 7 (f)). Mouth parts with abundant setaeı longer than clypeal margin setae. Mandibles with largely extended membranous incisor lobes. Molar lobe bearing very a small tooth on its border ( Figure 7 View Figure 7 (a)). Maxillae with galea covered with spurs. Lacinia with abundant setae. Palpiger bearing long setae equally spacedı setae longer than those on lacinia. Maxillary palpus glabrousı four-segmentedı apical segment length equal to segments 1 – 3 combined ( Figure 7 View Figure 7 (b)). Ephypharinx (ventral view) strongly sclerotisedı the medial portion covered of tuberclesı anterior margin-lacking emargination ( Figure 7 View Figure 7 (c)). Labrum with abundant setaeı ‘ U ’ -shaped emargination on anterior portionı first labial palpomere three times wider and larger than second and third palpomere combined ( Figure 7 View Figure 7 (d)). Pronotum: borders carinateı folded upwards and flattened near the anterior angle. Medio-lateral fovea smoothı lacking setaeı punctures or striations. Hypomeron: bearing ocellate setigerous puncturesı anterior margin carinate. Portion under pro-femur (in regular position) smooth and glabrous. Prosternum: triangular shapeı bearing ocellate setigerous punctures – setae having at most 1/fourth of the length of the hypomeron setae. Mesonotum: anterior margin widely emarginatedı medially with abundant setae and lacking microsculpture at medial portion. Mesosternum: medially glabrousı laterally bearing setigerous ocellate puncturesı setae having at most 1/fourth of the length of hypomeron setae ( Figure 1 View Figure 1 ). Mesepimeron: with ocellate setose punctures equally spaced; hair denseı usually concealing the structure. Mesepisternum: bearing ocellate punctures (setigerous or not)ı superior margin ending in an acute angle reaching the pseudoepipleuron ( Figure 8 View Figure 8 (a)). Metasternum: mesometasternal suture weakly defined. Anterior lobe twice longer than wideı setigerous punctures restricted to the borders and encroaching to the middle of anterior lobe. Longitudinal groove feebly markedı ending in a weak concavity. Metasternum sides bearing ocellate puncturesı setigerous or not and evenly spaced ( Figure 8 View Figure 8 (a)). Posterior border medially emarginate. Fine puncture (viewed under 15x magnification) present near concavity. Legs: inner pro-tibiae angle acute or spiniform. Ventral surface of pro-femur bearing a medial row of punctures (setigerous or not)ı ventral surface of meso- and meta femur bearing similar marginal punctures only near anterior margin and apex. Pro-tibiae bearing shortı scattered setae following tibial teeth both ventrally and dorsallyı a cluster of larger setae concentrated in the inner angle. Ventral surface of pro-tibiae bearing a longitudinal ventral carinaı which is glabrous. Pro-tarsi 5 segmentedı apical segment having the length of the third and fourth tarsomeres combined. Pro calcar spiniformı strongly bent downwards on malesı straight in females. Meso- and metatibiae strongly enlarged towards apexı both rounded at internal and external bordersı lacking transverse carinas or tubercles. Setae following internal and external metatibial borders. Meso and metatibial apex sinuatedı bearing scattered setae similar to a brush along the apical margin. Each meso-tibia bearing two calcarı both with truncated apex. Meta tibiae bearing a single calcarı bifurcate in malesı truncate at apex in females. Meso and metatarsi with abundant setaeı tarsomere greatly enlarged towards the apex. Elytra: bearing nine striaeı eighth striae never reaching elytra basis. Hindwing (macropterous) ( Figure 7 View Figure 7 (g)): bearing folding articulation and complete costalı subcostalı intercostalı cubital and anal veinsı usually with 1.5 to 2 times he elytra length. Hindwing (brachypterous) ( Figure 7 View Figure 7 (h)): bearing folding articulation. Basal sclerites glabrous. Subcostal vein intersecting costal axis at its basal quarter. Medial vein extending to the folding articulation. Distinct setae present on basal third of costal axis and at folding articulation. Cubital vein presentı anal vein absent. Smallı developed membranous portion apical to folding articulation with incomplete or weakly marked venationı usually equal to the elytral length or shorter. Abdomen: with visible 6 ventritesı anterior margin of ventrite 2 – 6 bearing ocellate punctures but always glabrous ( Figures 8 – 10 View Figure 8 View Figure 9 View Figure 10 ). 1st ventrite usually glabrous bur may have 4 – 7 setae on each side. Male sixth ventrite constricted medially. Females sixth abdominal ventrite three times larger than the fifth ventrite and usually having modifications at the central portion ( Figures 8 – 10 View Figure 8 View Figure 9 View Figure 10 ). Pygidium: glabrousı with fine punctures ( Figure 8 View Figure 8 (b)). Apically excavate or not. Swollen or flat. Phalobasis ( Figures 2 View Figure 2 ı 12): cylindrical; symmetricalı sides positioned parallel to each other; basal area with one tubercle on each side; ventral part presentı distinctly sclerotised; opening smallı restricted to basal area. Paramera ( Figure 2 View Figure 2 ): symmetricalı having from 1/3 to 2/3 of the phalobasis length; long and thinı with rounded or acute apex; lacking or having basal and/or longitudinal excavations; subgenital plate present in ventral viewı apex and base roundı acute and/or emarginated; baseı at junction with phalobaseı produced in a membranous excavation or sclerotised – if sclerotisedı having grooves or excavations. Endophalus (Internal sac) ( Figure 4 View Figure 4 ): sclerites localised along the internal sac extension; lamella copulatrix positioned anterior to axialı SAı FLP and SRP scleritesı which remain in the same plan at basal portion; axial sclerite cylindrical; SA sclerite with medial expansion and acute ends; FLP sclerite smallı ‘ C ’ shapedı superior apical portion indistinctly sclerotised; SRP semicircular. Female genitalia ( Figure 5 View Figure 5 ): vaginaı bursa copulatrix and ovaries membranous sac-like; spermatheca heavily sclerotisedı ‘ C ’ shaped with one acute end and sclerotised ‘ wing-link ’ (allae) projections near spermatic duct insertion; glandula inserted on wide excavation at medial portion.

Morphological variation. In this sectionı we describe how structures shared by all Cephagonus species vary morphologically. This following description can also be applied to Dichotomius and related genera in most of the cases with exceptions pointed in the descriptions and diagnosis. Dorsal and ventral surfaces of the integument may be smooth ( Figure 13 View Figure 13 (a-b))ı striated ( Figure 13 View Figure 13 (c-e))ı or chagrinated ( Figure 13 View Figure 13 (f-g)). Puncturesı both on dorsal and ventral surfacesı may be fine ( Figure 14 View Figure 14 (a))ı ocellate ( Figure 14 View Figure 14 (b))ı elliptical ( Figure 14 View Figure 14 (c))ı ocellate type II ( Figure 14 View Figure 14 (d)) (another kind of ocellate punctures that is found in few single species). Those punctures may be weakly impressed (distinguishable only beyond) (viewed under 20x magnification) or deeply impressed (distinguishable by naked eye). Each puncture may have single setaeı also called setigerous punctures. Setae may be very shortı long or long with a curved apex. Head horn may be lacking a knob ( Figure 33 View Figure 33 (a))ı conical ( Figure 35 View Figure 35 (f)) or produced in a cephalic carina ( Figure 39 View Figure 39 (i)). When it is conicalı it strongly varies in sizeı curvature and may have a round (Fig.) or bifurcate apex. Cephalic carina may be longer than wide ( Figure 19 View Figure 19 (a)) or wider than long ( Figure 23 View Figure 23 (a)). In both casesı it may have a medial emargination ( Figure 23 View Figure 23 (a))ı may produce tubercles on each apex ( Figure 19 View Figure 19 (a)) andı in a few casesı produces a blade-like central tooth ( Figure 32 View Figure 32 (g)). Both on head horns and carinası punctures and striations described as above may appear at the base. Pronotal lobes may be absent (usually associated with the absence of an anterior declivity and excavation) ( Figure 33 View Figure 33 (a))ı have a single-rounded central lobe ( Figure 33 View Figure 33 (i)) or two ( Figure 37 View Figure 37 (i)) or four rounded lobes ( Figure 24 View Figure 24 (a)). Elytral interstriae may be convex or flattened. In the paramera descriptionı we considered the ventral part as the one which bears the subgenital plate ( Figure 2 View Figure 2 (c)).

Distribution. Panama to Argentina. The majority of the species inhabits many types of forest habitats in their distribution ranges ( Figure 11 View Figure 11 ).

Representatives. Five groups are defined according to external morphology and geographic distributionı as follows:

● Group 1: Dichotomius (Cephagonus) ascanius (Harold) species group;

● Group 2: D. (C.) fissus species group;

● Group 3: D. (C.) quadraticeps species group;

● Group 4: D. (C.) ingens species group;

● Group 5: D. (C.) spadiceus species group.

PW

Paleontological Collections

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Coleoptera

Family

Scarabaeidae

Genus

Dichotomius

Loc

Dichotomius (Cephagonus) Luederwaldt 1929

Nunes, Rafael V. & Vaz-de-Mello, Fernando Z. 2019
2019
Loc

Pinotus

Erichson 1847
1847