Dinematocricus aff. bionus Chamberlin, 1920

Golovatch, S. I., Mauriès, J. P. & Akkari, N., 2021, On the collections of Indo-Australian Spirobolida (Diplopoda) kept in the Zoological Museum of the Moscow State University, Russia. 3. Some Rhinocricidae, Arthropoda Selecta 30 (1), pp. 3-27 : 6-8

Dinematocricus aff. bionus Chamberlin, 1920

Figs 10–31 .

Dinematocricus bionus Chamberlin, 1920: 195 , original description from the ♀ holotype from Bio Island , Solomon Islands.

“ Dinematocricus” bionus — Jeekel, 2001: 39.

MATERIAL. 1 ♂, 3 ♀♀ fragments ( ZMUM), Solomon Islands, Isabel Province, Bio Island , S7°31′49.3″, E158°41′0.1″, on litter surface, 23.XII.1977, Yu.I. Chernov leg.

DESCRIPTION. The only complete specimen (♂) ca. 85 mm long, 11.5 mm wide, with 32p+T segments. ♀ fragments up to 11.5–12.0 mm wide. Colouration rather uniformly dark grey- to black-brown, mostly deep olive, only labrum and prozonae red-brown, legs grey- to reddish brown, and eye patches blackish ( Figs 10–14 ).

All characters as in Propodobolus sp. , except as follows.

Tegument smooth, finely leathery, mesozonae mostly shining, metazonae almost dull. Interantennal isthmus ca. 2x diameter of antennal socket. Collum broadly and regularly rounded laterally, anterior, lateral and even caudolateral margins clearly, but narrowly bordered. Midbody segments/ rings very faintly striolate, apparently strongly obliterate, more densely and clearly so ventrad, dorsum fully smooth; striolations on metazonae longitudinal and visible only in ventral 1/3 (= well below ozopore level), on mesozonae slightly oblique, directed dorsad and extending up to ozopore level, but on both zonae still traceable even above ozopore ( Figs 10–14 ), more clearly so and less strongly obliterate in ♀ fragments. Scobinae present starting with ring 8: inconspicuous, paramedian, narrow, lunular pits separated from each other by their own width, devoid of posterior fields and placed just at anterior margin of prozona. Ozopores small, inconspicuous disks, starting with ring 6, each pore lying upon line/suture both just before metazona and longitudinal line. Rather numerous light and irregular spots/ sigilla on internal surface of meso- and metazonae ( Fig. 11 ).

Gonopods ( Figs 15–18 ). Anterior gonopods with a very strong, long, median, spear-shaped, apically rounded, sternal process (s), the latter only slightly longer than both coxa (cx) and telopodite (t) with its small, apical, rounded, laterally directed process (tp); cx stout, with a strong, mesal, subtriangular, apically acuminate projection (mp), t more slender than cx. Posterior gonopods consisting of a short, stout, subcylindrical coxa and a slender, much longer, bipartite telopodite; apicolateral branch (lb) the longest, ca. 3x as long as a similarly flagelliform solenomere (sl).

REMARKS. According to Chamberlin [1920], the holotype of Dinematocricus bionus was ca. 145 mm in length and 11.5 mm in width, and the body with 60 segments. As nothing was said about the antennae, Jeekel [2001] assigned this species to Dinematocricus with but reservations, referring to the genus in quotation marks.

The original, purely verbal description of D. bionus disagrees with our account in a few, but quite important details. The holotype is much larger in length, but the same in width; the number of body segments is strikingly greater (obviously 59+ T, vs. 32+ T); the tegument is finely coriaceous and micropunctate (vs. coriaceous and impunctate); the scobinae are supplied with finely striolate, triangular, posterior fields (vs. devoid of posterior fields); and the collum is narrowly rounded laterally (vs. broadly and regularly rounded).

The above strictly topotypic material from Bio Island in the ZMUM contains also 1 ♂ and 1 ♀ which are even smaller in size: length ca. 54 mm, width 6 mm, 58+1+T (♂) or length ca. 80 mm, width 8 mm, 59+T (♀); scobinae present on rings 8 to 31. Both smaller specimens fully agree in every detail to the larger subsample described above, thus allowing all ZMUM material to be considered as likely conspecific. The smaller ♂ and ♀ are only a little lighter than the larger ones, the striations on the body are less strongly obliterate and more clearly visible, while the gonopods are almost identical ( Figs 19–31 ). Given the remarkable size variations, could the ZMUM material belong to the same species D. bionus? We tend to answer positively. The main type of anamorphosis in Spirobolida being hemianamorphosis, very considerable size variations in adult conspecific Rhinocricidae have long been noted, while the gonopods grow gradually and either remain unchanged or get at least somewhat modified from one stadium to the next [ Mauriès, 1980; Enghoff et al., 1993; Bond et al., 2003]. The above variations in D. bionus seem best to be accounted for by hemianamorphosis.

However, before the holotype of D. bionus is properly revised, we refrain from definitely labeling our samples.

In addition to D. bionus , there are at least a few other congeners, e.g. D. carinatus (Karsch, 1881) , D. lanceolatus Brölemann, 1913 , D. repandus Attems, 1914 and D. strobilus Attems, 1914 , in which the anterior gonopods show a similarly conspicuous and spear-shaped central sternal process [ Brölemann, 1913; Attems, 1914], all of them from New Guinea and/or adjacent archipelagos [ Jeekel, 2001]. Thus, a syntype of D. repandus is illustrated here to show the remarkable similarities to D. bionus in gonopodal structure ( Figs 32–35 ). Another sample that clearly belongs to the same species group and identified as D. philistus Attems, 1914 is available in the ZMUM collections, as follows.

Figures

Figs 10–14. Dinematocricus aff. bionus Chamberlin, 1920, larger # from Bio Island. 10, 11 — anterior part of body, lateral and ventral views, respectively; 12 — middle part of body, dorsal view; 13 — midbody segment enlarged to show scobinae, dorsal view; 14 — caudal part of body, lateral view. Pictures by K.V. Makarov, taken not to scale. Рис. 10–14. Dinematocricus aff. bionus Chamberlin, 1920, более крупный # с острова Био. 10, 11 — переднЯЯ часть тела, соответственно сбоку и сниЗу; 12 — cреднЯЯ часть тела, сверху; 13 — увеличенный среднетуловиЩный сегмент со скобинами, сверху; 14 — ЗаднЯЯ часть тела, сбоку. Фотографии К.В. Макарова, снЯты беЗ масШтаба.

Figs 15–18. Dinematocricus aff. bionus Chamberlin, 1920, larger # from Bio Island. 15, 16 — anterior gonopods, anterior and posterior views, respectively; 17, 18 — right posterior gonopod, anterior and posterior views, respectively. Designations explained in text. Pictures by K.V. Makarov, taken not to scale. Рис. 15–18. Dinematocricus aff. bionus Chamberlin, 1920, более крупный # с острова Био. 15, 16 — передние гоноподы, соответственно спереди и сЗади; 17, 18 — правый Задний гонопод, соответственно спереди и сЗади. ОбЪЯснениЯ обоЗначений в тексте. Фотографии К.В. Макарова, снЯты беЗ масШтаба.

Figs 19–27. Dinematocricus aff. bionus Chamberlin, 1920, smaller # from Bio Island. 19, 20 — anterior part of body, lateral and ventral views, respectively; 21 — middle part of body, lateral view; 22 — midbody segment enlarged to show scobinae, dorsal view; 23 — caudal part of body, lateral view; 24, 25 — anterior gonopods, anterior and posterior views, respectively; 26, 27 — left posterior gonopod, anterior and posterior views, respectively. Designations explained in text. Pictures by K.V. Makarov, taken not to scale. Рис. 19–27. Dinematocricus aff. bionus Chamberlin, 1920, более мелкий # с острова Био. 19, 20 — переднЯЯ часть тела, соответственно сбоку и сниЗу; 21 — cреднЯЯ часть тела, сверху; 22 — увеличенный среднетуловиЩный сегмент со скобинами, сверху; 23 — ЗаднЯЯ часть тела, сбоку; 24, 25 — передние гоноподы, соответственно спереди и сЗади; 26, 27 — левый Задний гонопод, соответственно спереди и сЗади. ОбЪЯснениЯ обоЗначений в тексте. Фотографии К.В. Макарова, снЯты беЗ масШтаба.

Figs 28–31. Dinematocricus aff. bionus Chamberlin, 1920, larger (28, 29) and smaller (30, 31) ## from Bio Island. 28, 30 — anterior gonopods, anterior view; 29, 31 — right posterior gonopod, posterior view. Рис. 28–31. Dinematocricus aff. bionus Chamberlin, 1920, более крупный (28, 29) и более мелкий (30, 31) ## с острова Био. 28, 30 — передние гоноподы, спереди; 29, 31 — правый Задний гонопод, сЗади.

Figs 32–35. Dinematocricus repandus Attems, 1914, # syntype from Gazelle Peninsula, East New Britain Province, Bismarck Archipelago, Papua New Guinea; slide NHMW 4027. 32, 33 — anterior gonopods, anterior and posterior views, respectively; 34, 35 — both posterior gonopods, mesal and lateral views, respectively. Scale bars: 1.0 mm. Рис. 32–35. Dinematocricus repandus Attems, 1914, синтип # иЗ Gazelle Peninsula, East New Britain Province, Bismarck Archipelago, Papua New Guinea; микропрепарат NHMW 4027. 32, 33 — передние гоноподы, соответственно спереди и сЗади; 34, 35 — оба Задних гонопода, соответственно иЗнутри и сбоку. МасШтаб: 1,0 мм.