A new genus and two new species of Opilioacaridae (Acari: Parasitiformes) from Amazonia, Brazil with a key to world genera Author Vázquez, Ma. Magdalena Author Araújo, Marcel Santos De Author Feres, Reinaldo José Fazzio text Zootaxa 2014 3814 2 151 176 journal article 45562 10.11646/zootaxa.3814.2.1 e5919f1b-8545-40c8-908b-e87fb8c2f1ea 1175-5326 224993 453ACE3C-0977-4F8F-B4A7-3EF93508472B Amazonacarus Vázquez, Araújo & Feres n. gen. Diagnosis. Palp tarsus with 10 foliate setae. Palp tibia with 21–26 elongate, serrate setae, 2–6 of which extend to the base of the claws ( Fig. 10 ). Preanal segment with 4–6 dorsal and 2 ventro-lateral, setae ( Figs. 15–16 ). Ovipositor of the “complex type ”, i.e., with 2 pairs of thick, sclerotized spiny projections, a pair of glands connected by long, thin channels, plus 2–4 long, thin, fine, acutely-tipped genital setae visible under cuticle close to genital opening ( Fig. 20 ). Sensillum with a “crown-like” tip on tarsus I large, distinctly distal to the main group of sensory sensilla ( Fig. 21 ). Comparative notes. The new genus differs from most Old World genera by the presence of 2 pairs of eyes and With’s organ membranous and discoid (3 pairs of eyes and With’s organ biramous and setiform in Paracarus and Siamacarus ); the absence of setae on the main opisthosomal segments in all instars (with numerous setae in tritonymphs and adults of Panchaetes , Salfacarus and Vanderhammenacarus ) (Hammen 1977; Leclerc 1989 ); and the presence of setae on the penultimate segment (segment XVII) (absent in Adenacarus ) ( Hammen 1969 ). It differs from Opilioacarus , Phalangiacarus , Indiacarus , and Neacarus by the presence of more than 7 foliate setae on the palp tarsus ( Grandjean 1936 ; Das & Bastawade 2007 ). The presence of many foliate setae on the palp tarsus, each with multiple (>6) thin lobes, and the position of the sensillum with a crown-like tip on tarsus I are shared with Caribeacarus , the genus that is most similar to Amazonacarus . Amazonacarus can be differentiated from that genus by the presence of distinctly modified setae on the palp tibia, the presence of more than 3 setae on the penultimate segment (some undescribed Neacarus from Brazil also have>3 setae on that segment), and the presence of distinct internal sclerites in the ovipositor (all absent in Caribeacarus ). The elongate setae on the palp tibia appear to be unique. They may function to protect the foliate ( d - type ) setae on the palp tarsus. In Amazonacarus these setae are much longer than positionally similar setae in Caribeacarus or Neocarus ( Figs. 47–53 ).