Lineagona culmenicola, Shear, 2024

Shear, William A., 2024, Lineagona, a new millipede genus (Diplopoda, Chordeumatida, Cleidogonidae) from Texas, USA, and Nuevo León, México, Zootaxa 5397 (2), pp. 283-290 : 287

Lineagona culmenicola , new species

Figs 1–6

Type: Male holotype from 20 km west of Hwy. 85 and Cercado on Hwy. 20. Parque Nacional de Cumbres de Monterrey, N25.347°, W-100.182°, elev. 1260 M asl., Nueva Léon, México, collected 10 November 2005 by Casey Richart (collection number CHR 1228). Gonopods and male ninth legs are mounted on SEM stub WS29-12. All materials deposited in Virginia Museum of Natural History, Martinsville, Virginia, USA .

Etymology: “ cumbre ” in Spanish means “summit;” in Latin, “ culmen”. Hence “ culmenicola ” or “summitdwelling.”

Diagnosis: Differs from the only congener L. chisosi in being much larger (16 mm vs. 9 mm in length), and in the subdivided lateral (posterior) branch of the gonopod angiocoxite, which is set with tiny, curved filaments ( Figs 1–4 ) vs. in L. chisosi . The male ninth legs have five podomeres ( Fig. 5 ) vs two, with sometimes two additional tiny ones in L. chisosi ; the ninth leg coxae are elongate and bear a blunt, terminal, median apophysis set with coarse, triangular teeth ( Fig. 6 ); in L. chisosi these modifications are missing.

Description of male holotype: 30 rings. Length in alcohol ca. 16 mm, greatest width ca 1.5 mm. 25–28 ommatidia in well-developed triangular eyepatch. Rings smooth dorsally, with low, rounded shoulders. Legpairs 4–7 encrassate; legpairs 1–7 with tarsal papillae. Gonopods ( Figs 1–4 ): sternum (s, Figs 1–3 ) broad, well sclerotized anteriorly, membranous posteriorly ( Fig. 2 ). Coxae (cx, Figs 1–3 ) large, laterally cupped, with prominent knob bearing 10–12 long setae, with small posterior pores (cp, Fig. 2 ). Angiocoxites divided into anterior and posterior branches, the posterior branches subdivided into three rami. Anterior angiocoxite branches (aac, Figs 1–3 ) basally broad, evenly curved posteriad, tapering to acute tip. Posterior angiocoxite branches (pac, Figs 1–3 ) with three rami, the distalmost long, thin, separated from two basal rami by distinct gap; basal two rami broad-based, closely appressed, only slightly curved. All parts of posterior angiocoxite branch densely covered with fine, long, curving cuticular filaments ( Fig. 4 ). Colpocoxites (cc, Figs 1–3 ) small, blunt, not distally expanded. Male ninth legs ( Fig. 5 ) with enlarged, elongate coxae, their posterior surface roughened (cx, Fig. 5 ), distally coxae bear a strong, medially directed apophysis with recurved triangular teeth ( Fig. 6 ). Legpair 10 with coxae slightly enlarged, bearing eversible glands. Legpair 11 unmodified walking legs.

Females unknown, not collected.

Notes: The specimen was collected from an oak forest. The species present included Mexican Red Oak ( Quercus canbyi ), Mexican White Oak ( Q. polymorpha ), and Loquat Leaf Oak ( Quercus rysophylla ).

One of the features of the gonopods in this species is the presence of an apparent coxal pore (cp, Fig. 2 ). This raises an interesting question, since the colpocoxite is considered homologous to the extruded coxal gland of the eighth leg. If the pore seen here is in fact the pore of the coxal gland, the homology of the colpocoxite and the extruded coxal gland is not correct. I have not observed such a pore on the gonopods of any chordeumatidan I have examined. This observation also adds a new bit of data to the distribution of coxal glands in Nematophora. In Callipodida, the sister group to Chordeumatida , nearly all the legs may have coxal glands or they may be restricted to a series of legs on the anterior part of the body. In Chordeumatida , the distribution has been restricted to either the tenth and eleventh legs or to only the tenth legs. However, careful examination often detects small, perhaps vestigial pores on the male ninth legs. If these pores are the outlets of glands, the glands themselves are not extrusible, as they are on the tenth and eleventh legs. The observation recounted above is, in my experience, the first observation of such pores on the gonopods (eighth legs).

Figures

FIGURES 1–2. Lineagona culmenicola, n. sp., holotype male. 1. Gonopods, ventral view. 2. Gonopods, posterior view. Abbreviations: aac, anterior branch of angiocoxite; cc, colpocoxite; cp, coxal pore; cx, coxa; pac, posterior branch of angiocoxite; s, sternum.

FIGURES 3–6. Lineagona culmenicola, n. sp., holotype male. 3. Gonopods, oblique lateral view. 4. Posterior branch of angiocoxite, showing the many fine filaments. 5. Legpair 9, posterior view. 6. Coxal process of right legpair 9, showing teeth. Abbreviations: aac, anterior branch of angiocoxite; cc, colpocoxite; cx, coxa; pac, posterior branch of angiocoxite; s, sternum.