amnestorhacus, a new genus in the neotropical ...

Richard L. Hoffman & Daniella Martínez-Torres AMNESTORHACUS, A NEW GENUS IN THE NEOTROPICAL DIPLOPOD FAUNA, BASED ON THE FORGOTTEN SPECIES ARCIDESMUS OLOGONA SILVESTRI, 1898 (POLYDESMIDA, PLATYRHACIDAE)

Estratto dagli Annali del Museo Civico di Storia Naturale “G. Doria” Vol. 104 - 20 Settembre 2012

Genova 2012

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Richard L. Hoffman * & Daniella Martínez-Torres **

AMNESTORHACUS, A NEW GENUS IN THE NEOTROPICAL DIPLOPOD FAUNA, BASED ON THE FORGOTTEN SPECIES ARCIDESMUS OLOGONA SILVESTRI, 1898 (POLYDESMIDA, PLATYRHACIDAE)

The Colombian platyrhacid described by Filippo Silvestri in 1898 under the name Arcidesmus ologona has remained an intriguing mystery down to the present day. The original account was merely a single paragraph that briefly stated the salient peripheral features of the male syntype, closing with the remark “Organum copulativum articulo ultimo integro apice parum attenuato flexo ita ut angulum rectum formes”. The gonopod was not illustrated. The expression “integro” [entire, simple] certainly deserved a commentary that Silvestri never provided, inasmuch as in all other known Neotropical platyrhacids the gonotelopodite terminates in a distal process supplementing the solenomere. A. ologona was apparently something quite different, an alien element in the New World fauna. Subsequent authors were necessarily terse on the subject, having little of substance to work with. Attems (1899) only stated that the species belonged with those few in which the gonopods are simple and unbranched. Carl (1914) listed the species in his treatment of Colombian millipeds, referring it to the genus Platyrrhacus. Attems (1938) gave an abridged version of the original description, and placed ologona in the subgenus Haplorhacus of Platyrhacus, along with six Asiatic species having supposedly similar genitalic attributes. There seem to be no further published referen * Virginia Museum of Natural History, Martinsville, Virginia 24112, USA. E-mail: [email protected] Deceased on June 10, 2012. ** Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Edificio 425, Oficina 105, Bogotá, Colombia. E-mail: [email protected]

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ces. For all practical purposes the name ologona has been forgotten for over 70 years. It was customary for Silvestri (and many of his contemporaries) to retain a part of the type series (if greater than a single specimen) of the species they described. He therefore kept the female syntype of ologona, and presumably sent the male back to Dr. O. Bürger (his liaison with the Göttingen University Museum) after which it dropped out of sight, for unknown reasons. When J. Carl was preparing his monograph on the diplopods of Colombia, he took the precaution of borrowing many of the Silvestri types from Göttingen to redescribe and illustrate. But ologona was not among the number; in fact Carl did not account for any of the platyrhacids then known to occur in Colombia. Dr. Gert Tröster searched the existing material of Diplopoda housed at Göttingen, and confirmed the absence of anything named ologona. Thus the uncertainty about the status and identity of Arcidesmus ologona seemed to be unresolvable in the lack of any knowledge of its gonopod structure. However, in a completely unexpected and serendipitous turn of events, this obstacle was recently overcome. In requesting the loan of another Silvestri type specimen from the Genova Museum, an inquiry about A. ologona elicited the response from Dr. Maria Tavano, in charge of the Myriapoda collection, that only the female was represented. In the hope that at least some taxonomic insights might be derived from inspection of the female, it was obtained on loan and in removing the specimen from its housing vial, a small square scrap of paper was noticed adhering to its legs. Immediate inspection revealed that it was a tiny folded envelope, containing a gonopod that expressed the character stipulated by Silvestri for ologona, obviously abstracted from the male holotype. Thanks to Silvestri’s surreptitious precaution it is now possible to lift the veil that has obscured this enigmatic species after 112 years of anonymity. It represents a singular and distinctive element in the Neotropical fauna, and as it must be excluded from its position in Arcydesmus, a new generic name is herewith proposed to accommodate it.

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Family Platyrhacidae A m n e s t o r h a c u s n. gen. T y p e s p e c i e s : Arcidesmus ologona Silvestri, 1898. N a m e . A neologism composed of the Greek elements “amnestos” (forgotten) + “-rhacus” (a combining element often utilized in the formation of generic names in this family), bestowed to denote that the type species was essentially forgotten for many decades. D i a g n o s i s . A genus of Neotropical platyrhacids in which the telopodite of the gonopod terminates in an acuminate, flat blade, turned dorsomesad at a right angle to the basal (“prefemoral”) region (Fig. 4). Ozopores small, removed from paranotal edge by about 6X their diameter. Dorsal side of epiproct with two conspicuous divergent polished ridges. R a n g e . Known only from that of the type species, on the eastern slopes of the Cordillera Oriental, east of Bogotá, Colombia (Fig. 6). S p e c i e s . Only the type species is known. C o m m e n t a r y . The original description contains not a single word of commentary about the generic selection. Presumably Silvestri must have resorted to Cook’s 1896 key to American genera of this family, in which Arcydesmus occupied a place in the eighth, and last, couplet. This selection was inauspicious, since the gonopods of the generic type species, Arcydesmus comptus Cook, terminate in “rami” [branches] would exclude A. ologona with its “entire” telopodite. Examination (RLH, 1964) of the holotype of comptus in the Berlin collection (ZMB 950) showed the gonopod to be so similar to that of Barydesmus kerri Cook (the older name by one page) that these two names can only be regarded as synonymous (they were already merged in the 1980 “classification” on the basis of that discovery). In other known Neotropical platyrhacid genera, the solenomere is invariably smaller than the apical lamina. Perhaps the most parsimonious interpretation of the structure in Amnestorhacus would favor simple merger of the two elements rather than the actual loss of the solenomere with its function transferred to the remaining part. “Loss characters” frequently represent ambiguities in the sense of a trait being secondarily lost or never existing to begin

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with. In this particular case, peripheral character systems provide few insights vis-à-vis the nearest relative of A. ologona. Amnestorhacus ologona (Silvestri, 1898), n. comb. (Figs. 1-6) Arcidesmus ologona Silvestri, 1898: 67 (• and • syntypes from Villavicencio, Departamento Meta, Colombia, O. Bürger leg.). Present location of male unknown (formerly Zoological Museum, University of Göttingen); intact • and associated right gonopod of •, Museo Civico di Storia Naturale “Giacomo Doria”, Genova (MSNG). Platyrrhacus ologona: Attems 1899: 330; Carl 1914: 975. Platyrhacus (Haplorhacus) ologona: Attems 1938: 284.

M a t e r i a l . Right gonopod of male syntype, herein designated as lectotype of this species; female syntype, here designated as paralectotype, in MSNG (Silvestri’s collection). Nontypical series (all Colombia): Dept. Boyacá: Santa Maria, 800 m, November 2000, G. Amat and student group (ICN-MD 151, 1 • / 1 •), also “Vda. La Carbonera”, 600 m, 19 May 2009. E. Flórez & D. Luna (ICN-MD 223, 1 • / 2 ••), also “La Almenara”, 600-1100 m, E. Flórez & student group, (ICN-MD 229, 1 •, and VMNH 1 • / 1 •). Dept. Cundinamarca: Medina, 570 m, I. de Arévalo, October 1989 (ICN-MD 137, 1 •). Dept. Meta: Puerto López, Remolino, 200 m, May 2008, G. Amat (ICN-MD 163, 1 •). Restrepo, 630 m, University student group, 14 October 1994 (ICN-MD 84, 3 ••). Villavicencio, “Bosque Bavaria”, 500-1100 m, 14 May 2012, R. del Valle (ICN-MD 138, 1 • / 1 •), same site, 3 May 2005, C. Rueda (ICN-MD 154, 1 •), same site, 8 October 2005, student group of Universidad Javeriana (ICN-MD 180, 1 •), same site, student group, 14 May 2005, student group (ICN-MD-224, 1 •), Vereda El Carmen, 940 m, 20 Apr 2011, G.A Ballén (ICN-MD 177, 2 •• / 2 ••). D e s c r i p t i o n . • topotype: length ca. 65 mm (body rigidly flexed by preservation), width of collum 7.0 mm, segment 2 = 10.2 mm, segment 4 = 13.0 mm, segments 6-8 = 13.2 mm, segments 10-13 = 13.0 mm, segments 14-16 = 12.8 mm, segment 18 = 10.0 mm. W/L ratio, ca. 20%. Color a dull medium brown, legs, antennae, and outer half of paranota only slightly paler. No trace of yellow or red ornamentation.


Head ca 5.0 mm across genal apices, genal depression wide but shallow, labrum with 7-7 marginal pits, 4-4 submarginal, clypeus with four spherical setiferous granules in two diads; other head surfaces uniformly granular; margin of antennal sockets unmodified, interantennal space 1.0 mm, antennae ca 7.8 mm long, 7th article longest, cylindrical, 6th and 7th articles without sensory modifications. Collum elevated-convex medially, surface tuberculate, lateral ends and anterior margin notably depressed, the latter set off by a shallow transverse depression. Paranota of anterior segments strongly deflexed, continuing convexity of middorsum (if horizontal, width value of segment 2 would increase by as much as 2 mm). Surface of prozona finely asperulate, texture expressed in the form of very fine short longitudinal striae, often anastamosing posteriad; stricture smooth; surface of metaterga dull, ornamented with mostly small rounded polished tubercles, not forming regular transverse rows, slightly more dispersed on paranota. Paranota moderate in size, at midbody slightly declivous, margins straight, very slightly undulate (Fig. 1), anterior and posterior edges very finely microdenticulate; ozopores small, removed by about 6 diameters from lateral edge. Posterior corners obtuse at midbody, thereafter increasing produced, acutely projecting on 14th-18th segments, rounded on 19th. Epiproct (Fig. 2) broadly rounded, dorsal surface smooth with two raised, divergent, paramedian ridges, between which shallowly concave. Paraprocts (Fig. 3) of normal platyrhacid form, without notable modification, hypoproct trapezoidal, paramedian tubercles large, as long as basal width. Sides of metazona densely and finely granulate; stigmata large and prominent, anterior stigma placed in front of coxal cavity with upper end upon the dorsal condyle; posterior stigma placed anterior to coxal cavity and its dorsal condyle. Legs attached to elevated bicruciately impressed podosterna, relatively narrow (1.2 mm at midbody, about equal to length of prefemora), surface glabrous, subcoxal region not produced into spines or tubercles, sterna of segments anterior to gonopods almost in contact (0.3 mm). Legs moderately setose, more profusely so on anteriormost segments, hairs as long as diameter of podomeres. Tibial trichome located at distal third of dorsal surface.

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3 1

2

Figs. 1-3 - Fig. 1: left paranota of segment 10, dorsal aspect; section of anterior edge drawn with higher magnification to show microdenticulation. Fig. 2: epiproct and paranotal lobes of 19th segment, dorsal aspect, showing paramedian ridges. Fig. 3: paraprocts and hypoproct, ventral aspect.

Gonapophysis of 2nd legs short, about as long as broad, cylindrical, apically truncate. Gonopod aperture oval, mostly restricted to the metazonum, all margins elevated, laterally convex and granular, posterior side forming a high incrassate rim that overhangs surface of the sternum between the legs, creating a deep sharply-defined groove. Gonopods: in situ (Fig. 4) with coxae in close contact, telopodites directed anterolaterad with distal half recurved mesad and apices overlapping. Coxae unmodified, with a single dorsal seta adjacent to base of cannula. Telopodite without torsion, efferent groove restricted to mesial surface, setose prefemoral region massive, distal


to curvature becoming thinner and laminate, drawn out into a thin acuminate termination (Fig. 5).

4 5

Figs. 4-5 - Fig. 4: gonopods in situ, ventral aspect. Fig. 5: left gonopod of lectotype, mesal aspect, with two views of telopodite in different aspects.

C o m m e n t . In the small size and placement of the ozopores, this species resembles the still enigmatic Psammodesmus cos (Cook, 1896) more closely than other Neotropical platyrhacids known to us. In the other characters cited for cos in Cook’s succinct diagnosis, there is less concordance, however, and until the status of that species is settled by some arbitrary action, the identity of Psammodesmus must remain uncertain. Ornamentation of the epiproct is unusual in presence of divergent paramedian ridges, but whether this character is of generic or specific significance will be unknown pending discovery of additional species. D i s t r i b u t i o n . The majority of confirmed collection sites depict a fairly limited range of about 60 km along the eastern slopes of the Cordillera Oriental in Boyacá, Cundinamarca, and Meta

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Departments (Fig. 6), at elevations between 400 and 1100 meters ASL. The specimen (ICN-MD 163) from Remolino (Puerto López) on the Rio Meta may represent a case of downstream fluvial transport established at a low elevation on the Meta. Male specimens from that locality will be of interest in confirming the specific identity of that population with the main body of the species.

VENEZUELA BOYACÁ

CUNDINAMARCA

CASANARE

META

ECUADOR BRAZIL

PERU

6

Fig. 6 - Distribution of Amnestorhacus ologona in Colombia. Left side map, location of species’ range (black shading), area enclosed in square shown enlarged in map on right side in greater detail.

ACKNOWLEDGEMENTS

We express our gratitude to Dr. Maria Tavano (Museo Civico di Storia Naturale “G. Doria”, Genova) for making the type material of ologona available for study, and to Dr. Gert Tröster (Institüt für Zoologie und Anthropologie und Zoologisches Museum, GeorgAugust-Universität, Göttingen), for searching for the male type of ologona in the myriapod material in that collection. Prof. Eduardo Flórez-D. (Instituto de Ciencias Naturales, Universidad Nacional de Colombia) kindly facilitated research by the second author on the


diplopod fauna of Colombia, and donated a pair of specimens to the Virginia Museum of Natural History.

REFERENCES Attems C., 1899 - System der Polydesmiden. II Theil - Denkschr. Kaiserl. Akad. Wissensch., Math.-naturw. Classe, Wien, 68: 251-435. Attems C., 1938 - Polydesmoidea 2. Fam. Leptodesmidae, Platyrhacidae, Oxydesmidae, Gomphodesmidae - Das Tierreich, Ed. W. de Gruyter, Berlin & Leipzig, 69: 1-487. Carl J. 1914 - Die Diplopoden von Columbien, nebst Beiträgen zur Morphologie der Stemmatoiuliden - Mém. Soc. neuchât. Sci. nat., Neuchâtel, 5: 821-993. Cook O. F., 1896 - New American Platyrrhacidae - Brandtia, Huntington, N. Y., 12: 51-54. Hoffman R. L., 1980 - Classification of the Diplopoda - Muséum d’Histoire naturelle, Genève, 237 pp. Silvestri F., 1898 - Diagnosticos de nuevos Diplopodos Sudamericanos - Anales Mus. nac. Buenos Aires, 6: 53-79.

ABSTRACT The enigmatic Colombian platyrhacid milliped Arcidesmus ologona has remained unknown for 112 years since its description by Silvestri in 1898, and subsequent loss of the male syntype. The species is redescribed on the basis of topotypic specimens and one of the type gonopods which had been sequestered with the surviving female syntype. Unusual formation of the gonopods mandates proposal of a new genus, Amnestorhacus, to accommodate this species, disjunct among the known Neotropical members of the Platyrhacidae.

RIASSUNTO Amnestorhacus, un nuovo genere nella fauna diplopodologica neotropicale, basato sulla specie dimenticata Arcidesmus ologona Silvestri, 1898 (Polydesmida, Platyrhacidae). L’enigmatico Diplopode colombiano Arcidesmus ologona è rimasto sconosciuto per 112 anni dopo la descrizione che ne diede Silvestri nel 1898 e a seguito della successiva perdita del sintipo maschio. La specie viene ora ridescritta sulla base di un esemplare topotipico, raccolto recentemente, e di uno dei gonopodi del maschio sintipo che era stato accluso al sintipo femmina superstite. L’inusuale morfologia dei gonopodi ha spinto gli Autori a proporre un nuovo genere (Amnestorhacus) per comprendere la specie in esame, che occupa una posizione del tutto isolata nell’ambito dei Platyrhacidae neotropicali sino ad oggi conosciuti.