Taxonomic revision of the South American subgenus Canthon ( Goniocanthon ) Pereira & Martínez , 1956 ( Coleoptera : Scarabaeidae : Scarabaeinae : Deltochilini )

In this article, the subgenus Canthon (Goniocanthon) Pereira & Martínez, 1956 is diagnosed within the tribe Deltochilini Lacordaire, 1856 and redefined with three species: 1) C. (Goniocanthon) bicolor Castelnau, 1840, from the Guyanas and northern South America, included for the first time in this subgenus; 2) C. (G.) smaragdulus (Fabricius, 1781), including two subspecies, C. (G.) smaragdulus smaragdulus, senior synonym of Canthon speculifer Castelnau, 1840 (neotype here designated), from the southern portion of the Atlantic Forest and C. (G.) smaragdulus subviridis Schmidt stat. rev. (lectotype here designated) from the northern portion of the Atlantic Forest; 3) C. (G.) fulgidus Redtenbacher, 1868, which includes three subspecies, C. (G.) fulgidus fulgidus from the southern Amazon (lectotype here designated), C. (G.) fulgidus martinezi subsp. nov., from the central and southern Amazon and C. (G.) fulgidus pereirai subsp. nov., from the western Amazon.

Goniocanthon was originally described as a genus, including Scarabaeus smaragdulus Fabricius, 1781, which was designated as type species, and Canthon fulgidus Redtenbacher, 1868. Subsequently, Halffter & Martínez (1977) downgraded Goniocanthon to subgeneric level under Canthon.Since then, Canthon (Goniocanthon) has been considered as belonging to the tribes of Canthonini or Deltochilini because of the following character combination: dorsal surface (pronotum and elytra) smooth with colourful metallic sheen and lacking tubercles, metasternum anterior lobe and pygidium convex (Pereira & Martínez 1956;Halffter & Martínez 1977;Vaz-de-Mello et al. 2011).Four names are currently recognized: C. smaragdulus (Fabricius, 1781), C. speculifer Castelnau, 1840, C. speculifer subviridis Schmidt, 1922 stat. rev. andC. fulgidus Redtenbacher, 1868.Both C. smaragdulus and C. fulgidus have a noticeable dorsal colour variation related to their geographic distribution.Individuals of Canthon smaragdulus from the northeastern Atlantic Forest in Brazil have a green colour, in contrast to blue-coloured individuals from the southern Atlantic Forest.Canthon fulgidus also exhibits chromatic variation in the Amazon: a green phenotype occurs in Colombia, Ecuador, Peru and Brazil (only in Amazonas State) and the species is commonly misidentified both in collections and in publications as C. smaragdulus (e.g., Pessôa & Lâne 1941;Blackwelder 1944;Vulcano & Pereira 1964;Medina et al. 2001;Ratcliffe et al. 2015).
The aim of this work is to reassess the taxonomic problems related to Goniocanthon through a taxonomic revision of the subgenus.This revision provides a better and clearer delimitation of the subgenus and its species through descriptions, diagnoses, identification key, distribution maps and illustrations.

Material and methods
Specimens from the following institutions were examined (curator in parentheses): NHMUK = The Natural History Museum, London, United Kingdom (Max Barclay).The code "BMNH" is used on the specimen labels.CMN = Canadian Museum of Nature, Ottawa, Canada (François Génier).The code "CMNC" is used on the specimen labels.UFMI = Setor de Entomologia da Coleção Zoológica da Universidade Federal de Mato Grosso, Cuiabá, Brazil (Fernando Z. Vaz-de-Mello).The code "CEMT" is used on the specimen labels.FAUN = Colección Entomológica de La Universidad de Nariño, Pasto, Colombia (Mauricio Rodríguez).The code "CEUN" is used on the specimen labels.HMUG = The Hunterian Museum, Glasgow, United Kingdom (examined in Oxford through a loan to Darren Mann) RBINS = Institut royal des Sciences naturelles de Belgique, Brussels, Belgium (Alain Drumont).
The code "ISNB" is used on the specimen labels.= Oxford Museum of Natural History, Oxford, United Kingdom (Darren J. Mann).The code "OUMNH" is used on the specimen labels.ZMHU = Museum für Naturkunde der Humboldt-Universität, Berlin, Germany, (Joachim Willers and Johannes Frisch).The code "ZMHB" is used on the specimen labels.
Lists of examined material were separated into type material and non-type material.For type material, labels are transcribed ipsis litteris and are separated by "/", with species names in italics.After the information from each type's labels, label colour or main characteristics are briefly explained in parentheses.In non-type material lists, information retrieved from labels was organized as follows: country names, or geographical extent of countries located in other continents, in capital letters (e.g., BRAZIL); department or state names are separated by an n-dash; the number of males (♂ or ♂♂) and females (♀ or ♀♀); municipality and/or locality (when available); coordinates, collection techniques, environment/ecological information, date (e.g., 3 Mar. 1986 means March 3 rd , 1986) and collector (leg.).
When available, collection techniques or other details were transcribed in the original language found on the label.The collection where the material is deposited is given in brackets (e.g., (CEMT) means deposited in CEMT collection).
Behavioural and ecological data described for C. fulgidus were obtained in Rondônia state localities between 2011 and 2015.
legs.Protibiae three-toothed, dorsal surface with two tufts of setae present on each tibial tooth.Protibial spur truncate, wider than long and apically emarginated, forming two spines.External border of protibia serrated.Profemur ventral surface black, smooth, glabrous, with a distal tooth on its anterior border.Ventral surface of meso-and metatibiae smooth (Fig. 1A).Meso-and metatrochanter with a hair tuft near femur articulation.
Paramera.On lateral view (Fig. 1G).Flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.On dorsal view (Fig. 1H): membranous portion wider at central portion and narrower near apex and basis.Apex rounded.internal saC (Figs 5,9).FLP involving A, forming a central duct with spiniform apex.SA lateral to FLP + A complex.MP distal to A, semicircular, widely emarginated; FLP + A complex involved by MP.SRP with lateral prolongation.

Morphological variation
BL: 9-14 mm, PW: 6-9 mm.Colouration of dorsal surface metallic sheen may vary from green to blue metallic colouration (Fig. 2A-B) (in both natural or artificial light).Female protibial spur as wide as long with a U-shaped emargination.Pygidium and metasternum flatter in females than in males.

Remarks and requirements for neotype designation according to Article 75 of The Code
Canthon speculifer was described by Castelnau (1840: 68).From this description it is possible to confirm that Castelnau referred to a blue-to-green Goniocanthon, mainly because he cited the gibbose metasternum, unique among Canthon.Evenhuis (2012) stated that part of Castelnau's syntype collection was incorporated into the Smithsonian Institute in Washington, and destroyed in a fire on January 24 th , 1865.Canthon speculifer was probably among these type specimens because successive searches in European and American museums did not yield the type series of C. speculifer.However, Castelnau had visited Brazil on a different occasion in the company of Eugêne d'Osery.They arrived in Rio Janeiro on June 17 th , 1843 to acquire information about Brazilian geography and history, as well as specimens for the French Academy of Sciences (Papavero 1971).Among these is a historical specimen deposited at MNHN in 1844 and identified by Castelnau as C. speculifer.This specimen, which we now propose as neotype, is not part of the syntypic series because it was collected some time after the description of C. speculifer; however, it was Castelnau himself who identified and labelled it only shortly after his original description, thus he probably maintained a clear vision of C. speculifer.The comparison of the designated neotype with the lectotype of C. smaragdulus reveals that C. speculifer and C. smaragdulus are synonyms.This neotype designation fixes the name C. speculifer according to Castelnau's original concept and allows us to establish the synonymy with C. smaragdulus.

Distribution
Brazilian Atlantic Forest and Paraná river forest (states of Mato Grosso do Sul, Paraná, Santa Catarina, São Paulo and Rio de Janeiro).Also in the Argentinian province of Misiones and the Paraguayan department of Guairá (Fig. 8).

Diagnosis
In the subgenus, C. (G.) smaragdulus subviridis stat.rev. is separated by the following combination of characters: ventral surface of meso-and metafemora smooth (Fig. 1A); dorsal surface of pronotum and elytral disc with similar metallic green colouration (Fig. 2B); metasternum anterior lobe strongly convex (Fig. 1B); profemur with a tooth on its anterior border.Paramera: on lateral view (Fig. 1G): flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.Internal sac (Fig. 5): FLP involving A forming a central duct with spiniform apex.SA lateral to FLP + A complex present.MP distal to A, not divided, semicircular, widely emarginated; FLP + A complex involved by MP.

Taxonomic remarks
Canthon smaragdulus subviridis stat.rev.was described as a variety of C. speculifer (Schmidt 1922).It was also listed as a variety of Goniocanthon smaragdulus in a catalogue, but Vulcano & Pereira (1964) did not explicitly treat this as a taxonomic act, nor did they consult the type material.Finally, this taxon is also treated as a variety of C. smaragdulus in a catalogue by Vaz-de-Mello (2000).Redtenbacher, 1868 Figs 1D-F, I-J, 3, 7-8, 10
legs.Protibiae three-toothed, dorsal surface with two tufts of setae present on each tibial tooth.Protibial spur truncated, wider than long and apically emarginated, forming two spines.External border of protibia serrated.Profemur ventral surface black, glabrous, with a distal tooth on its anterior border.Ventral face of meso-and metatibiae rugose on posterior half (Fig. 1D).Meso-and meta-trochanter with a hair tuft near femur articulation.
Pygidium.Convex.Basal line delimiting pygidium from pro-pygidium.Metallic sheen pattern similar to those of pronotal disc.
Paramera.In lateral view (Fig. 1I): flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.On dorsal view (Fig. 1J): membranous portion wider at central portion and narrower near apex and basis.Apex rounded.
internal saC (Fig. 7).FLP involving A forming a central duct with spiniform apex.SA lateral to FLP + A complex.MP distal to A, semicircular, widely emarginated; FLP + A complex involved by MP.SRP with lateral prolongation.

Morphological variation
BL: 8-16 mm, PW: 5-10 mm.Dorsal surface metallic sheen may vary between green, golden or red metallic colouration (Fig. 3A-C).Protibial spur of females as wide as long, with apical U-shaped emargination.Pygidium and metasternal anterior lobe less protuberant in females than in males.

Diagnosis
In the subgenus, C. (G.) fulgidus fulgidus is separated by the following combination of characters: mesoand metafemora ventral surface rugose on its posterior half (Fig. 1D); dorsal surface of pronotum and elytral disc with similar golden metallic colouration (Fig. 3A); metasternum anterior lobe weakly convex (Fig. 1E); profemur with a tooth on its anterior border.Paramera in lateral view (Fig. 1I): flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.Internal sac (identical to Canthon (G.) fulgidus martinezi subsp.nov., see Fig. 7): FLP involving A forming a central duct with spiniform apex.SA lateral to FLP + A complex present.MP distal to A, not divided, semicircular, widely emarginated; FLP + A complex involved by MP.

Distribution
Brazil, state of Mato Grosso, covering Amazon-Cerrado transitions including semi-deciduous and gallery forests (Fig. 8).

Natural history remarks
This subspecies and C. fulgidus pereirai subsp.nov.(described later in this paper) are found in Amazonian primary and secondary forests as well as in semideciduous and gallery forests in the states of Mato Grosso and Rondônia.However, both subspecies are especially abundant in várzea forest environments, where individuals of C. fulgidus are easily found perching on larger leaves exposed to sunlight in forest understory between 0.50 m and 2.5 m high (Fig. 10).Both males and females can wait up to 30 minutes on the same leaf, usually in the warmer hours of the day (between 10 am and 4 pm), only moving the antennae, probably trying to capture some odoriferous plume as described in Louzada (1998) for similar species.We have observed several times that, after perching, the individuals fly in the direction of some kind of primate faeces, including human.When manipulated, individuals of both subspecies release an odour of rotten or fermented fruit.

Diagnosis
In the subgenus, C. (G.) fulgidus martinezi subsp.nov. is separated by the following combination of characters: meso-and metafemora ventral surface rugose on its posterior half (Fig. 1D); dorsal surface European Journal of Taxonomy 437: 1-31 (2018) of pronotum and elytral disc with similar metallic green metallic colouration (Fig. 3B); metasternal anterior lobe slightly convex (Fig. 1E); profemur with a tooth on its anterior border.Paramera in lateral view (Fig. 1I): flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.Internal sac (Fig. 7): FLP involving A forming a central duct with spiniform apex.SA lateral to FLP + A complex present.MP distal to A, not divided, semicircular, widely emarginated; FLP + A complex involved by MP.

Taxonomic remarks
This subspecies is cited for Colombia (Medina et al. 2001) and Peru (Ratcliffe et al. 2015) as Canthon (Goniocanthon) smaragdulus because of its green metallic sheen, which allows it to be confused with the northern subspecies C. (G.) smaragdulus subviridis stat.rev.(diagnosed above).This subspecies is cited as Canthon fulgidus for Satipo province, Peru (Balthasar 1951).

Diagnosis
In the subgenus, C. (G.) fulgidus pereirai subsp.nov. is separated by the following combination of characters: meso-and metafemora ventral surface rugose on posterior half (Fig. 1D); dorsal surface of pronotum and elytral disc with similar metallic red colouration (Fig. 3C); metasternal anterior lobe slightly convex (Fig. 1E); profemur with a tooth on its anterior border.Paramera in lateral view (Fig. 1I): flattened; apex truncated; upper angle rounded; lower angle acute, forming a spine or tooth.Internal sac (identical to Canthon (G.) fulgidus martinezi subsp.nov., see Fig. 7): FLP involving A forming a central duct with spiniform apex.SA lateral to FLP + A complex present.MP distal to A, not divided, semicircular, widely emarginated; FLP + A complex involved by MP.

Diagnosis
In the subgenus, C. (G.) bicolor Castelnau, 1840 is separated by the following combination of characters: ventral surface of meso-and metafemora smooth (Fig. 4B); dorsal surface of pronotum and elytral disc with different colours, pronotum with light green metallic sheen and elytra with dark green metallic sheen (Fig. 4A).Metasternal anterior lobe flat (Fig. 4B).Profemur without teeth on anterior margin.Paramera, in lateral view (Fig. 4F): flattened; apex semicircular; upper angle rounded; lower angle triangular.In dorsal view (Fig. 4G).Internal sac (Fig. 9): FLP not completely involving A forming two duct with spiniform apex.SA lateral to FLP + A complex absent.MP distal to A, divided in MP 1 and MP 2, MP 1 semicircular, MP 2 fishhook-shaped with two hook; FLP + A complex involved by MP 1.

Remarks on the lectotype designation
The specimen designated herein as lectotype has a label with Pierre François Marie Auguste Dejean's handwriting indicating that François Louis Nompar de Caumont Laporte, the Comte of Castelnau, is the author of bicolor and the collector of that specimen.We are aware that Castelnau sold or donated his collections, but there is no evidence to state that all syntypes of Castelnau were sold to a single collection or went to a single place.

Redescription
male.Dorsal surface pronotum and elytra disc with different colours, pronotum with light green metallic sheen and elytra with dark green metallic sheen (Fig. 4A).
legs.Protibiae three-toothed, dorsal face with two tufts of setae present on each tibial teeth.Protibial spur truncated, larger than tall and apically emarginated, forming two spines (Fig. 4D).External border of protibia serrated.Profemur ventral face brown, glabrous, without a distal tooth on its anterior border.Ventral face of meso-and metatibiae rugose on posterior half (Fig. 4B).Meta-trochanter having a hair tuft near femur articulation.
abdomen.Ventrites glabrous, lacking punctures and not narrowed medially.internal saC (Fig. 9).FLP not completely involving A forming duct with spiniform apex.MP distal to A, divided in MP 1 and MP 2, MP 1 semicircular, MP 1 fishhook-shaped with two hook; FLP + A complex involved by MP 2. SRP with lateral prolongation.

Distribution
North of the Amazon forest, in Venezuela, Guyana, Surinam, French Guiana and Brazil (state of Amapá) (Fig. 8).

Taxonomic remarks
This is the first time in the taxonomic history of Canthon that C. bicolor is considered part of the subgenus Goniocanthon.The following character combination supports this decision: metafemora not claviform, hypomeron lacking transverse keel and pygidium strongly convex, an exclusive character of Goniocanthon among the genus.The latter character was already cited by some authors for C. bicolor (e.g., Harold 1868;Schmidt 1922;Balthasar 1939).In a preliminary phylogenetic analysis, Medina et al. (2003) place this species close to the subgenera Goniocanthon and Peltecanthon, mainly due to male internal sac sclerites.The main morphological difference of C. bicolor among Goniocanthon is the flat metasternum anterior lobe and the sclerite in the internal sac, which is divided in two structures (MP1 and MP2, Fig. 9).The relationship with Peltecanthon should be investigated with a more comprehensive phylogenetic analysis.

Discussion
Extensive taxonomic work dealing with Canthon and allied genera has been published in the last 50 years or so, when taxonomic knowledge of the Canthonini tribe (Deltochilini sensu Bouchard et al. 2011) was summarized.The subgenera of Canthon were the last defined (Halffter & Martínez 1967, 1977).The division of species of Canthon is arranged into subgenera and incertae sedis species groups.Larger subgenera, such as Canthon s. str., Glaphyrocanthon and incertae sedis species groups, are difficult to diagnose and certainly need urgent taxonomic revisions.On the other hand, smaller subgenera such as Boreocanthon, Francmonrosia, Peltecanthon, Pseudepilissus and Goniocanthon have better morphological definitions.Even so, some of them still have taxonomic problems to be solved.
A convex metasternal anterior lobe and, most importanty, a strongly convex pygidium, are exclusive to Goniocanthon in the genus Canthon.Therefore, it should not be difficult to separate Goniocanthon from other subgenera of Canthon.The head margin, clypeal teeth, pronotal disc and dorso-ventral colour pattern of Goniocanthon resemble those of Peltecanthon and of some species of Canthon s. str.such as C. angularis Harold, 1868.However, none of them have a convex pygidium or metasternal anterior lobe.If Goniocanthon and Peltecanthon were sympatric, they would have similar chromatic variation European Journal of Taxonomy 437: 1-31 (2018) patterns, as is the case with other genera such as Dichotomius and Canthidium observations).The tooth on the anterior border of the profemur is shared with Francmonrosia (Medina et al. 2003), although it is absent in C. bicolor.Since the genus Canthon is evidently polyphyletic (Medina et al. 2003), we still cannot draw major conclusions on the phylogenetic relationships of Goniocanthon and other groups of Canthon.
The dorsal surface colouration of Goniocanthon may be problematic for the identification of subspecies, especially when separating Canthon fulgidus martinezi subsp.nov.and C. smaragdulus subviridis stat.rev.(Pessôa & Lâne 1941;Blackwelder 1944;Vulcano & Pereira 1964;Medina et al. 2001;Ratcliffe et al. 2015).In this case, one should examine the ventral surface of the meso-and metafemora (rugose in subspecies of C. fulgidus, smooth in C. smaragdulus) and the convexity of the metasternal anterior lobe (stronger in subspecies of C. smaragdulus than in C. fulgidus).Besides, C. fulgidus is Amazonian while C. smaragdulus occurs in the Atlantic Forest.For practical subspecies differentiation, one should associate dorsal colouration with geographic distribution.Even the internal sac sclerites do not provide this separation in subspecies, only showing interspecific variation between C. fulgidus, C. smaragdulus and C. bicolor.
The distribution of subspecies of C. smaragdulus follows a similar pattern of that of other Atlantic Forest taxa, which have distributions influenced by the Doce River (Cabanne et al. 2007;Carnaval & Moritz 2008;Colombi et al. 2010).Canthon smaragdulus smaragdulus tends to occur south of the Doce River, while C. smaragdulus subviridis stat.rev.tends to occur in the northern portion of the Atlantic Forest (Morrone 2014).However, this separation is not absolute since both subspecies occur in close proximity in the states of Rio de Janeiro and São Paulo.
The distribution of subspecies of Canthon fulgidus seems to be influenced by the interfluves of major Amazon rivers (Fig. 8).The distribution of C. fulgidus martinezi subsp.nov. is similar to that of other taxa from the Imerí, Napo, Ucayali and Rondônia biogeographic provinces described by Morrone (2014).Canthon fulgidus pereirai subsp.nov.occurs in the states of Pará and Amazonas, distributed throughout the northern region of Madeira and Xingu-Tapajós Provinces.The distribution of C. fulgidus fulgidus covers the northern part of the state of Mato Grosso, corresponding to the southern part of the Madeira and Xingu-Tapajós Provinces according to Morrone (2014).Canthon bicolor occurs in the Guyana Shield, distributed throughout the Guianan Lowlands (Morrone 2014).
The perching behavior of C. fulgidus fulgidus (Fig. 10) shows how much this species is adapted to várzea forest habitats, which are annually flooded (Nunes-da-Cunha et al. 2015).Our observations corroborate two hypotheses of Louzada (1998) for perching in Scarabaeinae.The first one is related to perching for body temperature regulation, where C. fulgidus has been observed basking in the sun on larger leaves.The second hypothesis is related to resource foraging: after perching, many individuals located some kind of faecal mass, or followed us in the field while we installed baited traps with human faeces.

Conclusions
This work dealt with the taxonomic revision of Canthon (Goniocanthon) Pereira & Martínez, 1956.We introduced C. bicolor and clarified the differentiation between C. fulgidus and C. smaragdulus, defining three and two subspecies for them, respectively.In this work, we proposed the hypothesis that body colour is influenced by geographic distribution.However, we strongly believe that our hypothesis needs the following tests: 1) collection of more geographical records and consequently morphological data to determine if species separation follows distribution and 2) comparison of morphological and molecular data to determine if the latter corroborates the morphological-geographical separation.Both approaches may lead to interesting future studies.