Systematic nematode surveys for criconematids in the coastal sand dunes of southern Spain and on the Atlantic coast of Florida, USA, revealed the presence of three populations of sheathoid nematodes identified as Hemicriconemoides promissus, H. ortonwilliamsi and H. wessoni. All of them belong to the fourth group proposed by Decraemer and Geraert (1992) as they are characterised by wide body annuli ca ≥ 5 μm wide and a stylet ca 50 μm long, although all have a distinctly different female tail shape. Comparative SEM studies on H. cocophillus, H. mangiferae, H. brachyurus and H. promissus were done. SEM studies from paratype material and female specimens of a newly discovered population from Spain, confirmed the absence of lateral vulval flaps for both H. promissus populations, justifying the rejection of the synonymy proposed by Germani and Anderson (1991), and the re-establishment of H. promissus as a species distinct from H. brachyurus. The present records of H. promissus and H. ortonwilliamsi extend their geographical distribution from Italy to an additional Mediterranean country and constitute the first reports of both species in Spain. Additional morphometric data and illustrations of a Pensacola, FL, USA, population of H. wessoni, the type species of the genus, are also presented.