Rhizotrogus ruzzantei Sabatineli, Cillo & Bazzato, 2025

Sabatinelli, Guido, Cillo, Davide & Bazzato, Erika, 2025, Rhizotrogus ruzzantei, a new species from southwestern Sardinia (Italy), with biogeographic considerations on the Sulcis-Iglesiente subregion and Scarabaeoidea endemics of Sardinia (Coleoptera: Scarabaeidae: Melolonthinae: Rhizotrogini), Zootaxa 5665 (2), pp. 256-270 : 260-265

Rhizotrogus ruzzantei Sabatineli, Cillo & Bazzato , sp. nov.

( Figs 2, 3, 5–7 , 8–14 )

Type locality. Italy, Sardinia region, South Sardinia province, Domus de Maria municipality, Punta su Pisu locality, located about 55 kilometres southwest of Cagliari .

Type material. Holotype ♂ ( MCNG): Italy, Sardegna (Ca) / Domus de Maria, P. ta [Punta] su Pisu / 25 m, 30˚53’N 8˚61’E / 11.XII.2010, G.Ruzzante leg. // HOLOTYPUS / Rhizotrogus ruzzantei Sabatinelli, Cillo & Bazzato, 2025 (red label). Paratypes: Italy, Sardinia, “ Sud Sardegna ” province: Domus de Maria, Punta su Pisu , 25 m , 12.I.2014, G.Ruzzante leg., 1 ♂ AMMC , 15 ♂ 1 ♀ MHNG , 2 ♂♂ JMCH ; 14.II.2016, G.Ruzzante leg. 20 ♂♂ LFCC ; 19-20.III.2011, G.Ruzzante leg. 4 ♀♀ LFCC ; 14.II.2016, G.Ruzzante leg. 25 ♂♂ DCCC , 2 ♂♂ DPCR , 2 ♂♂ FFCP , 2 ♂♂ RRCC , 2 ♂♂ DSCC , 2 ♂♂ PLCC ; 14.III.2011, G.Ruzzante leg. 11 ♂♂ DCCC ; 19/ 20.IV.2011, G.Ruzzante leg. 4 ♂♂ LFCC ; 22.I.2011, G.Ruzzante leg. 2 ♂♂ AMMC ; 22.II.2015, G.Ruzzante leg. 4 ♂♂ LFCC ; 23.I.2011, G.Ruzzante leg. 5 ♂♂ LFCC ; 23.I.2011, G.Ruzzante leg. 6 ♂♂ AMMC ; 23.II.2015, G.Ruzzante leg. 3 ♂♂ LFCC ; 28.I.2011, G.Ruzzante leg. 11 ♂♂ DCCC ; 29.I.2011, G.Ruzzante leg. 44 ♂♂ LFCC ; 29.I.2012, G.Ruzzante leg. 2 ♂♂ UNSS ; 29.I.2012, 25m, G.Ruzzante leg. 36 ♂♂ 5 ♀♀ DCCC ; 30.I.2011, G.Ruzzante leg. 2 ♂♂ AMMC . Isola di Sant’Antioco , env. Sant’Antioco , 14.III.2007, D.Cillo leg., 1 ♂ DCCC ; 16.XII.2007, E.Bazzato leg. 4 ♂♂, EBQE . Teulada, 23.XI.2020, L.Fancello leg., 2 ♂♂ LFCC . “ Città Metropolitana di Cagliari ” province: Villa San Pietro , 04.I.2016, S.Macis leg., 13 ♂♂ DCCC ; 20.III.2015, E.Bazzato and S.Macis leg. 3 ♂♂ DCCC ; II.2015, S.Macis leg. 12 ♂♂ EBQE ; II.2015, E.Bazzato and S.Macis leg. 26 ♂♂ DCCC ; XII. 2015, S.Macis leg. 1 ♂, EBQE ; Santa Margherita di Pula , I.2019, M.Massi leg. 2 ♂♂ FFCP . All Paratypes with red label: PARATYPE ♂ or ♀ / Rhizotrogus ruzzantei / Sabatinelli, Cillo & Bazzato, 2025.

Diagnosis. Integument reddish-brown. Antennomeres II–X bear fine, inconspicuous setation; the longest setae on antennomeres VII–X are markedly shorter than the width of antennomere III (approximately 0.3×). Elytra with intervals 3 and 5 wrinkled but not elevated. Wings well developed both in male and female. Protibia tridentate, with a developed basal tooth lacking a medial tibial carina; the medial tooth is well-developed and bears a dorsal carina. The most striking morphological differences between R. ruzzantei sp. nov. and other Mediterranean Rhizotrogini and in particular with sympatric R. genei is the significantly longer protarsi in R. ruzzantei sp. nov. (average 6.00 mm vs. 4.82 mm in R. genei ). Moreover, the sides of the pronotum are generally uniformly reddish-brown and, in contrasts with R. genei , in which the lateral margins of the pronotum are typically broadly and distinctly yellowish ( Fig. 4 vs. 5). Parameres are not diagnostic when compared to those of other known species within the genus.

Description. Holotype male. Habitus as in Fig. 2 . Measurements in mm: body length from anterior margin of clypeus to apex of pygidium 15.9, body maximal width 9.1, ratio body length/maximal width 1.7, antennal club length 2.4, II-VII antennomeres length 2.1 mm, scapum length 1.6, clypeus maximal width 2.3, clypeus medial length 1.9, front width at base 2.2, pronotum medial length 4.24, pronotum maximal width 6.8, scutellum length 1.8, scutellum width at base 1.4, anterior tibiae length 3.9, anterior tarsi length 6.8, median tibiae length 4.2, median tarsi length 6.6, posterior tibiae length 5.1, posterior tarsi length 6.8, pygidium medial length 3.1, pygidium width at base 3.1, in lateral view phallobase length 2.7 and paramera length 2.4. Body. Integuments rather uniformly reddish brown, shiny, underside and legs lighter ( Fig. 2 ). Head. Clypeus sub-trapezoidal, anterior angles not visible, 1.2x as wide as long at the midline; margin slightly reflexed all along its length, and almost flat at the posterior ends, above eyes, anterior margin of the clypeus with medial sinuation; surface smooth, quite shining, punctures strong and dense on most of the surface, uniformly distributed. Fronto-clypeal suture straight, well visible all along its length. Frons with strong, dense, punctures, similar to those of the postero-medial part of the clypeus and even denser on vertex. Postero medial part of head with by flat elevation on vertex and extended to the posterior part of clypeus, glabrous. Canthus with a row of dense, long, thick setae. Clypeus and frons glabrous. Pronotum. 1.93x as wide as long, with maximum width slightly at the middle. In dorsal view, surface regularly convex. Anterior angles broadly obtuse, well-marked, posterior angles comparatively more obtuse and smooth. Margins bordered all along the perimeter. Anterior border thicker than others. Anterior margin with short erected setae. Lateral margins with some long, thick, erect yellow setae emerging only from the dorsal side of the border, especially near anterior half producing a series of carinulae. Dorsal surface glabrous, shining, with sparse, irregularly punctures, denser on discus. Elytra. Glabrous, except for inconspicuous micro-setae emerging from punctures and for setae on epipleura. Surface covered with slightly wrinkled punctures, rather weak and sparse, slightly denser towards sides. Only the first (sutural) and second stria are well recognizable, signs of the others are barely perceivable among the punctation. Interval 1 well marked, almost completely void of punctures but covered with wrinkles. Intervals 3 and 5 barely recognisable as feebly longitudinal stripes with less dense punctation, not significantly raised. Epipleura delimited by a carina reaching the apex, bearing a row of thin setae, longer and sparse in the distal third, very sparse and short in the remaining part. Scutellum. Triangular, glabrous, shiny, with few very sparse punctures. Basal third covered by a tuft of long setae inserted below the posterior margin of pronotum. Pygidium. Microreticulate, looking overall glabrous, with few setae near the apex, Punctures round, moderately incised, irregularly sparse. Ventral side. Thorax covered by dense and long fluffy setation, masking the integument. Abdominal ventrites with short, adpressed, scattered setae, especially present in the central part of ventrites. Antenna. 10-segmented, antennal club 1.4x as long as antennomeres II–VII, antennomeres III–V non-disjointed along the posterior border ( Fig. 8 ). Legs. Protibia 3-toothed, proximal tooth developed but without medial carina, medial tooth well developed, marked by a developed medial carina connected to the dorsal tibial carina. Femora with dense setae long and thin, similar to those of ventral side of thorax. In addition, few thick, stiff setae on meso- and metafemora, along the posterior margin, especially in the proximal area. Meso-metatibia with internal sidelong setose, external side glabrous, except for long setae emerging from a carina, at about 2/3 of the length. Dorsal surface of metatibae with scattered puntures.

Wings. Well developed ( Fig. 7 ): length 18.3 mm; maximum width 6.6 mm; ratio body length/wing length 0.87.

Aedeagus. In lateral view, the parameres are shorter than the phallobase, with a length ratio of approximately 0.89. The parameres are ventrally fused, with a partially sclerotized dorsal surface and a large medial membranous area ( Fig. 11, 13 ). This membranous region expands medially and tapers toward the apex. The apices are blunt and nearly closed on the ventral side. Internal structures of the endophallus include inconspicuous raspulae (Fig. 15), tigillum robust ( Fig. 14 ), V-shaped, and exceeds half the length of the endophallus.

Variability of paratypes males. Body length ranges from 13 to 16 mm; maximum body width from 7.4 to 8.8 mm. Some specimens exhibit partial non-disjunction of antennomeres III–V, resulting in an antenna that appears 9-segmented. In a few individuals, the lateral sides of pronotum are slightly lighter in coloration compared to the rest of the pronotal surface.

Description of female. Measurement in mm: body length 14.3; maximum body width 8.9, with a length/width ratio of 1.6. Antennal club length 0.8; funicle 1.6; scape 0.9. Wing length 12.6; maximum wing width 4.6 ( Fig. 6 ); body length/wing length ratio 1.1. The females have an ovoid body shape compared to males (see body ratio) ( Fig. 3 ). Vaginal sclerites inconspicuous, as in Fig. 12 .

Etymology. The species is named in honor of the late Giampaolo Ruzzante, who collected and generously shared specimens of this species with colleagues. He was also the first to recognize its morphological differences from the sibling species Rhizotrogus genei Blanchard, 1851 .

Distribution and ecological notes. Among the approximately 450 specimens of the R. genei / ruzzantei complex examined in this study, R.ruzzantei sp. nov. appears to be restricted to the southern part of Sulcis, specifically in the areas of Domus de Maria, Sant’Antioco, and Villa San Pietro ( Fig. 18 ). This agrosilvopastoral zone is characterized by environments dominated by degraded garrigue and low Mediterranean scrub, typically ranging from sea level to about 50 meters above sea level. The species occurs in degraded garrigue habitats with sparse vegetation, primarily composed of Pistacia lentiscus , Euphorbia dendroides , Olea europaea sylvestris , Genista corsica and Juniperus phoenicea . Larvae are most probably rhizophagous and feed on the roots of various native herbaceous plants.

Adults are active from late autumn to early spring (23 November to 20 April), even under low temperatures and light rainfall. Males were mainly collected while flying and attracted to artificial lights operating from dusk to dawn, or found beneath stones in short winter grass lawns. Females were rarely collected (10 females among 256 males), despite possessing well-developed wings ( Fig. 6 ). Only one female was observed in flight; others were collected under stones or found crawling near artificial light sources.

Discussion. Table 1 presents the minimum and maximum values, average, and standard deviation for each character in both species, revealing several noteworthy patterns in their morphological variation.The PERMANOVA analysis ( Table 2), revealed a statistically significant overall morphological divergence between R. genei and R. ruzzantei sp. nov.; a significant main effect of species was detected (F=9.52, p ≤ 0.01), indicating consistent interspecific morphological differences across individuals. The main effect of character was highly significant (F=4092.1, p<0.001), reflecting substantial inherent variation among the eight measured morphological characters. Notably, the Character × Species interaction was also highly significant (F=25.24, p<0.001), accounting for 8.76% of the total morphological variation. This interaction indicates that morphological differences between species are not uniform across characters but are instead trait-specific, suggesting that the studied morphological features are particularly informative for species delimitation. Post-hoc pairwise comparisons using the PERMANOVA t statistic ( Table 3) revealed that the most pronounced and statistically supported differences observed in tarsal lengths, particularly in the length of the protarsus length and in the protarsus/protibia ratio (t = 16.24, p ≤ 0.001) which showed the highest discriminatory power in the analysis. Further significant differences were detected in mesotarsus and metatarsus lengths, reinforcing the pattern of longer tarsi in R. ruzzantei sp. nov. Body size also contributed to interspecific differentiation, with R. genei being generally larger in body length and maximum width, although these differences are less pronounced in relative terms (6–7%) and show some degree of overlap in value ranges ( Table 1, 3 and Fig. 16 ). In addition to the longer anterior tarsi in R. ruzzantei sp. nov. than in R. genei , the species can also be distinguished by pronotal coloration: R. ruzzantei sp. nov. exhibits a nearly uniform reddish-brown pronotum ( Fig. 5 ), while R. genei shows lighter lateral margins contrasting with a darker discal area ( Fig. 4 ). Together, these two morphological characters strongly supports the taxonomic separation of two species and provide reliable diagnostic characters for distinguishing the species, even in regions of sympatry and potential intermixing in southern Sulcis. To rule out conspecificity with the synonyms of Rhizotrogus genei Blanchard , we examined the type series of R. sardous ( Burmeister, 1855) housed in ZNSH while we excluded R. insularis Reiche, 1862 from consideration, as it was described from Corsica, a location far outside the known distribution range of ruzzantei sp. nov.

Figures

FIGURES 1–7. Habitus of 1) Rhizotrogus genei Blanchard, 1851 ♂ specimen from Cagliari; 2) R. ruzzantei sp. nov. holotype ♂; 3) R. ruzzantei paratype ♀. Pronotum lateral view: 4) R. genei ♂; 5) R. ruzzantei ♂. Left wing: 6) R. ruzzantei ♀; 7) R. ruzzantei ♂ (scale line = 2.5 mm).

FIGURES 8–14. Rhizotrogus ruzzantei sp. nov.: 8) antenna of ♂; 9) of ♀ (scale line = 0.750 mm). Aedeagus 10) lateral view; 11) dorsal view (scale line = 0.5 mm). 12) Female genital sclerites (scale line = 0.5 mm). 13)Aedeagus with everted endophallus (scale line = 1 mm); 14) details of tigillum (scale line = 0.5 mm); 15) details of endophallus membrane with raspulae (scale line = 0.01 mm).

FIGURES 16–20. 16) Graphical representation of morphometric differences between Rhizotrogus genei Blanchard, 1851 and R. ruzzantei sp. nov. 17) Labels of R. genei syntype in MHNG. 18) Distribution map in Sardinia of R genei Blanchard, 1851 and R. ruzzantei sp. nov. Spatial relations between Northern Sardinian bloc and Sulcis-Iglesiente bloc (yellow line) in 19) Langhian Stage (Miocene); 20) Tortonian Stage.