<i>Myolaimus ibericus</i> sp. n. (Nematoda, Rhabditida, Myolaimidae) from southern Iberian Peninsula, with a key to species of the genus.

A new species of the genus Myolaimus is described from agricultural areas in the southeast of the Iberian Peninsula. Myolaimus ibericus sp. n. is characterized by its 560-783 μm long body in females and 526-731 μm in males, cuticle often appearing swollen and baggy, lateral field with one longitudinal wing, lip region with six amalgamated lips having ten (6 + 4) setiform papillae, stoma consisting of a wider anterior chamber (cheilo-gymnostom) and a tubular posterior part (stegostom) separated by a well developed dorsal tooth and two small, lateral (one right and another left) teeth, glottoid-like apparatus structure appearing at metastom, pharyngeal corpus 1.7-2.6 times the isthmus length, excretory pore and deirids located at metacorpus level, deirids pore-like in females and seta-like in males, female reproductive system monodelphic-prodelphic with antidromous ovary, post-uterine sac 1.7-2.7 times the corresponding body diameter long, V = 50-56, female rectum 1.3-2.0 times the anal body diameter long, female tail conical-elongate (54-70 μm, c = 9.9-13.1, c' = 4.4-5.8) often enveloped by the baggy cuticle, male tail conoid (8-10 μm, c = 58.4-73.1, c' = 1.1-1.4) and ventrally constricted at its middle, bursal structure with seven (4+1+2) pairs of genital papillae. This is the first record of the genus from the Iberian Peninsula. Description, measurements and illustrations, including SEM photographs are provided. An illustrated compendium of the posterior ends of males in Myolaimus species is also presented.