Conotylidae Cook, 1896

Shear, William A., Richart, Casey H. & Wong, Victoria L., 2020, The millipede family Conotylidae in northwestern North America, with a complete bibliography of the family (Diplopoda, Chordeumatida, Heterochordeumatidea, Conotyloidea), Zootaxa 4753 (1), pp. 1-78 : 7-8

Family Conotylidae Cook, 1896

Conotylidae Cook, 1896:8 . Verhoeff 1932:500. Shear 1971:58; 1972:268; 1976:4.

Idagonidae Buckett & Gardner 1967:117 .

Japanosomidae (recte: Japanosomatidae), Mauriès 1978:63, 1982:180 (nomen translatum from Japanosominae Verhoeff 1914).

Macromastidae Loomis & Schmitt 1971:126.

Members of the family Conotylidae are the only heterochordeumatideans except for species of Adritylidae Shear, 1971 to occur in North America. Both families are distinct as the only chordeumatidans native to the continent with the mentum of the gnathochilarium undivided and having males with coxal glands on legpair 10. All known conotylids have 30 trunk rings (collum + 28 podous rings + telson). There is very little variation in somatic characters, except for size and the degree to which metazonital dorsolateral shoulders are developed; these range from nearly absent to extensions resembling polydesmidan paranota. Hence we are left with characters of the gonopods to discern species, genera and even subfamilies. Fortunately, these structures are complicated, rich in characters, and highly invariable within species (though there are exceptions to this latter rule).

The anterior gonopods (modified eighth legpair) of conotylids may be simple or complex, but always consist of a single article probably homologous to the coxa, partially or completely fused to a transverse sternite with strong lateral lobes. The important features of this article are very likely formed from the rim of the former coxal gland of the podomere, and thus can be called angiocoxites, though this term is rarely applied since the anterior gonopods are unitary. In many of the species, there is a deep pit posteriobasal on the gonopod which we consider homologous to the gland opening of the eighth coxa. Frequently a channel runs from this pit or pore to near the tip of the gonopod. Elaborations of the distal gonopod may include both basal and posterior branches and fimbriate, nodular or excavated regions.

The ninth leg modifications in males of heterochordeumatidean species are distinctive, with a complex coxal process and a free prefemur (which may be slightly modified), but the rest of the podomeres are coalesced into (or reduced to) a single cylindrical, clavate or ovoid article (though perhaps homologous just to the femur) that never bears a vestigial claw (in the conotylid subfamily Idagoninae , however, the telopodites of the ninth legs are entirely absent). The coxites are often complex and obviously play a role in spermatophore transfer, and for this reason can properly be called posterior gonopods. Again, it is likely that the coxal process (or coxite) is an angiocoxite, though in the past it has sometimes been characterized as a colpocoxite, a process derived from the extruded and sclerotized coxal gland, rather than its rim. Our evidence for this parallels that for the anterior gonopod: the presence of a well-defined gland pore, often seen with exudate, either at the posterior base or midlength posteriorly in many species. The details of gonopod structure of the various genera covered in this paper is discussed under each of them, below.

In many conotylid genera such as Brunsonia there is a tendency for the anterior gonopods to be strongly reduced and for the coxites of the posterior gonopods to be enlarged and complicated. In the related Megalotylidae , in fact, the anterior gonopods are reduced to small spikes fused to a small discoid sternum. This suggests that the posterior gonopods may, in many cases, have usurped the sperm transfer function of the anterior gonopods. On the other hand, species of the conotylid genus Idagona have the posterior gonopods virtually vestigial and without telopodites, making it hard to recognize anterior gonopod reduction as a phylogenetic trend throughout the family. There exist no systematic or comprehensive studies on how sperm or spermatophores are transferred from male to female in conotylids.

Conotylids can be separated from adritylids by the presence of profoundly modified tenth legs in the males of the latter, which have greatly enlarged coxae and tiny, 2-jointed telopodites (see Shear 1971 for illustrations). More difficult to discern, generally only by digesting the anterior gonopods to remove muscle tissue, is that the adritylid anterior gonopods are cheirites, structures which are bilaterally separated, but in which the gonopod, half the sternite and its associated tracheal apodeme are inseparably fused (see Shear 1971). In conotylids the glandular tenth coxae may be somewhat swollen, but telopodites of normal length are always present ( Fig. 83 ). Invariably in conotylids, prefemora 11 bear mesobasal, dorsally directed apophyses ( Figs. 84 , 261 ). This character is shared with adritylids and at least some megalotylids. In the field (particularly in northwestern North America) conotylids may be quickly separated from other chordeumatidan families by being 4–20 mm in length, with prominent metazonite shoulders or even paranota, and long, curved segmental setae. For a key to previously described conotylid genera and a discussion of the characters of each, see Shear (1976).

Superficially, conotylids could be confused with members of the North American endemic Trichopetalidae (Cleidogonoidea) , an unrelated taxon that occurs from Oklahoma eastward and is absent from the Rocky Mountains and Pacific coast states (a few trichopetalids are found in caves in central and eastern Mexico). Trichopetalids also have segments with prominent shoulders and long segmental setae. In fact, conotylids have sometimes been described as trichopetalids (i.e., Loomis & Schmitt 1971). However, trichopetalids have a divided mentum; in males, the ninth leg telopodites of trichopetalids are two-segmented rather than three-segmented and sometimes bear a vestigial claw; trichopetalids have coxal glands on legpair 11 as well as 10—but conotylids have the glands only on the tenth coxae. For more information on trichopetalids, see Shear (2003, 2010).

The genera of conotylids are presently a bit difficult to clearly separate, and for generic and species identification, readers are directed to the diagnoses and illustrations provided here. The plethora of species and genera in northwestern North America leaves little doubt that, pending the discovery of other centers of diversity (perhaps in the mountains of northwest or southwest China) this part of the world is home to the most diverse fauna of conotylids, and may be the region of origin for the family.

In eastern North America ( Shear 1971, 1972), as well as in Japan ( Shear & Tsurusaki 1995) conotylids seem to be most active in the colder, wetter part of the year, and in the southern Appalachians occur at higher altitudes, associated with the northern hardwood or coniferous (spruce-fir) biomes, or are found in caves. Even in more northerly regions, for example the northern Mississippi Valley or central and northern New York, there is a definite tendency for species to prefer cave habitats. With specific ecological reference to northwestern North America, the careful reader will note that nearly every collection from northern California northward was made between November and March, indicating the adaptation of the conotylids to activity in the cooler, wetter winter weather of the region. From central California south, collections have mostly been made in spring as damper weather comes in from the Pacific Ocean, or at higher altitudes, or from caves. In one extreme example, Complicatella neili , n. gen., n. sp., the only known population was collected in a cave at 2660 meters in elevation atop a barren limestone peak surrounded by sagebrush desert in the Humboldt Mountains of Nevada. This species shows modest troglobiotic adaptations. These chorological and microhabitat observations indicate that conotylid diversity may well be seriously underestimated, due to the fact that not much collecting is done in the winter months. The rich haul brought in by William P. Leonard, CHR and their associates by recognizing the importance of winter collecting supports this prediction.

Figures

FIGS. 68–84. Calityla spp. Figs. 68–74. Calityla essigi. Fig. 68. Left posterior gonopod coxite, posterior view. Fig. 69. Tip of left posterior gonopod coxite, posterior view. Figs. 70–74. Male legs 3–7, respectively. Figs. 75–85. Calityla humboldtensis. Fig. 75. Anterior gonopods, posterior view. Fig. 76. Posterior gonopods, posterior view. Fig. 77. Tip of left posterior gonopod coxite, posterior view. Figs. 78–82. Male legs 3–7, respectively. Fig. 83. Male leg 10. Fig. 84. Male leg 11. Fig. 85. Femoral knob of male leg 7.

FIGS. 258–261. Lophomus shelleyi. Fig. 258. Anterior gonopods, anterior view. Fig. 259. Right posterior gonopod, posterior view. Fig. 260. Tips of filaments making up flagellum. Fig. 261. Coxa, trochanter and prefemur of leg 11.