Polynoncus seymourensis ( Mutchler, 1925 )

Costa-Silva, Vinícius, Strümpher, Werner P., Thyssen, Patricia J. & Vaz-de-Mello, Fernando Z., 2024, Taxonomic revision of the South American genus Polynoncus Burmeister, 1876 (Coleoptera: Scarabaeoidea: Trogidae), Journal of Natural History 58 (1 - 4), pp. 14-166 : 151-152

Polynoncus seymourensis ( Mutchler, 1925)

( Figures 30 , 64 )

Trox seymourensis Mutchler, 1925: 229 (original description); Blackwelder 1944: 219 (checklist); Van Dyke 1953: 124 (notes of Galapagos’ specimens); Vaurie 1962: 131 (redescription); Linsley and Usinger 1966: 152 (list of Galapagos species); Franz 1985: 96 (list of Galapagos species)

Trox (Polynoncus) seymourensis : Scholtz 1982: 16 (catalogue)

Polynoncus seymourensis : Scholtz 1986a: 362 (systematics); Scholtz 1990: 1446 (redescription); Zidek 2013: 16 (checklist); Zidek 2017: 108 (checklist)

Type specimen examined (through detailed photographs). HOLOTYPE. ( AMNH – Figure 64 ) First label [white, aged, typeset]: ‘ South Seymour / Galapagos / 23 April 1923 ’. Second label [white]: ‘ Williams Galapagos Exped., / Dept. of Tropical Research , / N. Y. Zoological Society, / William Beebe, Director’. Third label [red, typeset]: ‘TYPE’ ( Figure 64c ). Type locality: ‘ South Seymour’ (also named Isla Baltra), Galapagos Islands, collected by Charles William Beebe (1877–1962), an American naturalist.

Differential diagnosis. Polynoncus seymourensis is most similar to P. galapagoensis and P. sallei . It can be distinguished from the latter species by having medial edges and basal tubercles of pronotum fused, which are distinctly separated in P. sallei . Also, P. seymourensis has the humeral callus prominent, with tubercles in the same elytral costae slightly separated (sometimes forming a poorly raised continuous ridge); and notable intercostal punctures. Polynoncus galapagoensis has the lateral margin of elytral arched, with humeral callus obsolete; odd-numbered costae (with exception of sutural margin), with tubercles covered with tomentum and slightly spaced, forming an interrupted and raised elytral costae.

Geographic distribution. Polynoncus seymourensis was reported only for the Galapagos ( Isla Fernandina, Isla Isabela [also called “Albemarle Island and Cowley Island], Isla Santa Cruz, Isla Española, Isla Seymour [type], Isla Floreana, Isla Genovesa, Isla Pinta and Isla Baltra), being historically treated as endemic to the Archipelago since its description (eg Van Dyke 1953; Vaurie 1962; Scholtz 1982, 1986a, 1990; Zidek 2013, 2017).

In the course of this study, we found three specimens of P. seymourensis (2♂ and 1♀) collected on the mainland ( Ecuador and Peru), being the first record of this species outside of Galapagos Islands ; therefore, it is no longer endemic to the Archipelago ( Figure 30 ).

Examined non-type material (32 specimens). ECUADOR: Galápagos, Darwin Is ., 1968, no collector (3 BMNH); Isabela Is ., Siera Negra, Pampas , 1000 m, February 1987, S . Abedrabbo leg . (1 BMNH); Isabela Is ., Villamil , 20 August 1906, F .X . Williams leg . (2 BMNH); Marchena Is ., Pta . Espejo , 11–24 March 1992, Bursera grove, carrion trap, S . Peck leg . (1 BMNH); Santa Cruz Is ., 3 km S Bellavista , 150 m, 1–29 February 1989, S . Peck and B . Sinclair leg . (2 BMNH); Santa Cruz Is ., 6 March 1995, N . Criollo leg . (1 CVMD); Santa Cruz Is ., 6 March 1995, N . Criollo leg . (1♀ CEMT); Santa Cruz Is ., Charles Darwin Research Station ( CDRS), 10 m, 17–30 January 1989, UV light, S . Peck and B . Sinclair leg . (2 BMNH); Santa Cruz Is ., Los Gemelos , 610 m, 1–28 February 1989, FIT, Scalesia Forest, S . Peck and B . Sinclair leg . (2 BMNH); Santa Cruz Is ., Puntudo , 650 m, 1–29 February 1989, FIT, Scalesia Forest, S . Peck and B . Sinclair leg . (1 BMNH); Santa Cruz Is ., without specific locality, December 1968, R .D . Sievers leg. (6 BMNH). Loja, Loja , no date or collector (1♀ CVMD) . Manabí, Manta, San Juan , bosque seco [dry forest], 8 January 2010, William Chamorro leg . (1♂ CVMD) . PERU: Piura, Suyo , 24 January 1977, R . Garcia leg . (1♂ CVMD) .

Figures

Figure 30. Distribution map of Polynoncus galapagoensis (red circle) and P. seymourensis (green triangles) in Galapagos Islands, South America. The records with a black dot in the centre indicate the type locality of the respective species.

Figure 64. Holotype of Trox seymourensis Mutchler, 1925 (now Polynoncus seymourensis): habitus in a, dorsal and b, lateral view; c, labels. Photos by Lee Herman (AMNH). Length of specimen: 10.5 mm.