Martenseya, Shear, 2021

Shear, William A., 2021, Additions to the millipede family Caseyidae. II. Martenseya, a new genus of miniature, blind millipedes from California (Diplopoda, Chordeumatida Striariidea, Striarioidea, Caseyidae), Zootaxa 4984 (1), pp. 108-113 : 110-111

Martenseya new genus

Type species. Martenseya minutocaeca n. sp.

Diagnosis. Distinct from all other caseyid genera in the lateral two metazonital setae set on a distinct swelling, and in the gonopods, which consist of two narrow coxites and lack flagellocoxites. Unlike all other species so far described, the third legs of Martenseya minutocaeca n. sp. do not have enlarged, elongated coxae. The type species is by far the smallest known caseyid, at 3.2 mm long in males. The two species of caseyid previously ranked as smallest, Metopiona sheari Gardner & Shelley, 1989 and Speoseya grahami Causey, 1963 , at 8–10 mm long are two or three times larger than Martenseya minutocaeca n. sp.

Etymology. I am delighted to name this unusual new genus in honor of Prof. Dr. Jochen Martens, my esteemed friend and colleague, on the occasion of his 80th birthday. To avoid homonymy, the suffix − eya, as in Caseya and Speoseya , is added to the name. The name is feminine in gender.

Description. See below, as for the type and only known species, Martenseya minutocaeca n. sp.

Distribution. Presently known only from Marin County, California, USA.

Notes. The divergence from the general plan of the Caseyidae of the single included species mandates the establishment of the new genus. Martenseya minutocaeca n. sp. lacks long gonapophyses on the second legs, and the third legs, rather than having elongate coxae and reduced telopodites, are unmodified and exactly like the following legs. The tenth legs have coxae that are only slightly enlarged and lack lobes and processes.

The simple gonopods are not unlike those of Metopiona sheari Gardner & Shelley, 1989 in having only anterior and posterior angiocoxites (though quite different inn form), a large sternum, and no flagellocoxites. However, M. sheari has the typical pregonopodal leg modifications that are lacking in Martenseya n. gen. Metopiona sheari is easily twice the size of Martenseya minutocaeca n. sp., and has 10 ommatidia. The other known small caseyid is Speoseya grahami Causey, 1963 which is eyeless but even larger (10 mm) than M. grahami . I have studied the holotype male of S. grahami and found the gonopod pattern very close to that of Opiona , not at all similar to Metopiona or Martenseya n. gen. Finally, I have seen two species of another undescribed genus from Washington state in the size range of M. minutocaeca n. sp., but with two black ommatidia on each side of the head and a gonopod pattern that is completely different, again resembling that of Opiona .