Two remarkable new species of Penicillata (Diplopoda, Polyxenida) from Table Mountain National Park (Cape Town, South Africa)

Abstract Two new species of the families Polyxenidae and Synxenidae, are described from Table Mountain National Park, South Africa. Propolyxenus squamatus sp. n. (Polyxenidae) has tergites I–X mostly covered by scale–shaped trichomes directed caudally, a character previously known only in Synxenidae. The structure of scale–shaped dorsal trichomes is different to that of the scales in Phryssonotus and Condexenus species. Phryssonotus brevicapensis sp. n. (Synxenidae) is the only known species of the genus Phryssonotus having 11 tergites, (including collum and telson) and 15 pairs of legs, as in Condexenus biramipalpus Nguyen Duy–Jacquemin, 2006. These two species therefore appear to occupy an intermediate position between Phryssonotus (12 tergites) and Polyxenoidea (maximum of 11 tergites).

ethanol. The bulk of this material, including the holotypes and several paratypes, has been deposited in MNHN. For light microscopy, the specimens are mounted on slides in "Baume de Marc André". SEM micrographs were taken using a scanning electron microscope at the Zoology Department, University of Cape Town. Genus Propolyxenus Silvestri, 1948 Propolyxenus Silvestri, 1948Propolyxenus Silvestri, 1948: Nguyen Duy-Jacquemin and Geoffroy 2003: 100. Propolyxenus Silvestri, 1948: Short and Huynh 2010 The genus is typical of the subfamily Polyxeninae, due to the structure of the telson, but shows more than 2 transverse rows of barbate trichomes on each tergite.
Etymology. The specific name refers to the scale-shaped tergal trichomes. Diagnosis. Differs from all other congeners by the position and structure of the tergal trichomes: these flat scale-shaped trichomes cover the tergites and are different from the barbate trichomes of the lateral tufts, pleurites and head. They are observed for the first time in the family Polyxenidae. As in the family Synxenidae, they lie close to the tergites and are all directed caudally, but differ from those of Synxenidae in their shape and structure.
3 trichobothria, arranged in a triangle, with the most internal (near posterior tufts of vertex) smaller than the 2 others (Figs 2C, D, 3F). Surface of labrum ( Fig. 3G) with  numerous small short cuspidate papillae; papillae of anterior 2 to 3 rows larger; 7+8 lamellate teeth on anterior margin (holotype: Fig. 3G), 8+8 (paratype); clypeo-labrum with 9 setae along posterior margin (Fig. 3G). Outer palp of gnathochilarium with 11 or 12 sensilla; middle palp with 19 or 20 sensilla (Fig. 3H). Trunk ( Fig. 2A): On each tergite (except collum, tergite X and telson) the trichomes are arranged in 3 rows and 2 lateral tufts (Figs 2B, 4A, B); each paired tuft connected by posterior and anterior rows of trichomes; middle row with more spaced trichomes (Fig. 4A). There are 2 types of trichomes. The flat trichomes, referred to as scales (sc) of the 3 rows are wider than barbate trichomes of lateral tufts (bt) and their shape and structure are different (Figs 2B, 4B, 5A-C); they look like the scales of Synxenidae by their position: all are directed caudally and cover the tergites I (with only a posterior row) to X (Figs 4A, B). Their structure is different from scales of Synxenidae (Figs 5A-E). The trichomes of the lateral tufts are longer and arranged in a bunch (Figs 2B, 4A, B (bt), C). Lateral protuberance of tergite I with 3 barbate trichomes (Fig. 4A).
Legs: Coxae I with 1 seta and coxae II with 3 setae; all other coxae without setae. All trochanters and prefemora with 1 seta. All tibias (except 11 and 12) have 1 small seta tapered apically; other articles without seta. Telotarsus bearing an anterior process with a spinous projection longer than claw, 2 latero-anterior and posterior spiniform processes; posterior lamellar process thickened and basally pleated.
Head: 6 ocelli on each side. Vertex with 1 pair of posterior tufts of 20+19 trichomes consisting of 3 rows, the middle row with 10 trichomes. Antennal article VI with 3 basiconic sensilla: 1 anterior shorter and thinner than the 2 posterior ones; the more posterior slightly thinner than the other; 1 setiform sensillum between anterior and posterior basiconic sensilla and 1 posterior coeloconic sensillum; antennal article VII with 3 basiconic sensilla, the anterior slightly thinner than the others, 1 setiform sensillum between the 2 posterior basiconic sensilla and 1 posterior coeloconic sensillum. 3 trichobothria, arranged in a triangle, with the most internal smaller than the 2 others. Surface of labrum as in adult females; clypeo-labrum with 10 setae along posterior margin. Outer palp of gnathochilarium with 12 sensilla.
Trunk: Trichomes arranged in 2 lateral tufts with 19 to 25 barbate trichomes connected by 3 rows of scales on tergites III-V and only 2 on other tergites. The tergites II-V have 22 to 31 scales, the collum 12 and the tergite VII 18. Lateral protuberance of tergite I with 3 (left) and 2 (right) barbate trichomes.
Discussion. P. squamatus sp. n. is strongly distinguished from other species of the genus by the shape of the trichomes covering the tergites. Compared with the most closely related species Propolyxenus lawrencei Condé, 1949, from Natal (Champagne Castle, Drakensberg Mountains, alt. 6000 ft.), P. squamatus sp. n. shares the following characters: 6 ocelli; internal trichobothrium shorter than the other 2; number and shape of sensilla on antennal articles VI and VII (Condé 1949(Condé , p. 125-126, 1959; surface of the labrum with numerous papillae, the 2 or 3 anterior rows larger. The new species shows the following important differences from P. lawrencei: Position and structure of trichomes on tergites: on each tergite (except collum and telson) the trichomes are arranged in 3 rows and 2 lateral tufts; each paired tuft being connected by posterior and anterior rows of trichomes; the middle row has more spaced trichomes. In P. lawrencei, the trichomes are arranged in 3 or 4 irregular rows, forming 2 elongated lateral areas, slightly separated by a narrow medial space.
There are two types of trichomes: the trichomes of the three rows are wider and flatter than the trichomes of the lateral tufts, pleurites and head, and their shape and structure are different, being observed in the family Polyxenidae for the first time. They can be compared to the scale-shaped trichomes of Synxenidae: the trichomes of the rows are all directed caudally and cover the posterior half of tergites II-X and their internal structure is reinforced by differently distributed chitinous elements (Figs 5C-E). The lateral trichomes are longer and arranged in lateral tufts. It is remarkable that the barbate trichomes of P. squamatus sp. n. show a progressive transformation into scale-shaped trichomes in the posterior row of the tergite, representing a transition between the two types of trichomes as if, during the course of evolution, the former trichomes had changed into scale-shaped trichomes. These scale-shaped trichomes are thought to protect the animals from desiccation, abundant rain or other environmental disturbances.
In a key of the genus Propolyxenus, P. squamatus sp. n. would be easily distinguished from all other congeners as is only species with scale-like trichomes. The other species of Propolyxenus are more difficult to identify using morphological characters such as the number of ornamental trichomes or coxal glands of the males. For instance, both P. patagonicus (Silvestri, 1903) and P. australis Short and Huynh, 2010, bear four pairs of coxal glands (cf. Condé et Massoud 1974, p. 227 for P. patagonicus) contrary to the first tentative key proposed by Short and Huynh (2010 p. 15). There is a difficulty in the limited nature of keys based (even partly) on characters such as coxal glands, requiring collection of adult males. More appropriate characters need to be determined for a more robust key for the genus. The genus Phryssonotus is characterised by the tergites having dark striated, scaleshaped trichomes directed caudally, all the others being long, dark barbate trichomes; trichomes A and B on head close to trichobothria, one of them being shorter and different from the two others. Etymology. Refers to the shorter body length and development compared to the most closely related species, P. capensis. Diagnosis. 10 ocelli; 5 trichomes B close to the smallest trichobothrium (tc) as in P. capensis. Differing from P. capensis with 10 rings in adults instead of 11 (without telson), 15 leg pairs instead of 17, and the attendant shorter post-embryonic development. Males with 3 pairs of coxal glands on legs 7-9.
Surface of labrum with numerous, small, short cuspidate papillae; papillae of anterior 3 or 4 rows larger, the size of the following papillae decreasing progressively, the smaller ones in the posterior third; about 30 lamellate teeth at anterior margin. Clypeo-labrum with ca. 10 setae, about 3/4 maximum width of labrum. Lateral expan-  sions of gnathochilarium about twice as long as diameter of middle palp, with 21-25 sensilla, middle palp with 26-29 sensilla, of which antero-medial sensilla shorter than the others (Fig. 8F).
Trunk of adults with 11 tergites (including collum and telson) and 15 pairs of legs (Fig. 7A). Collum with 2 medial, separate oval clusters comprising 80-90 barbate trichomes and a lateral group of 8-14 barbate trichomes. Tergites II-X with submedial and posterior rows of scale-shaped trichomes directed caudally (Fig. 7D), the posterior row arranged along the posterior margin of the tergite; 1 area of aligned barbate trichomes at end of each row, except on tergite II where are 35-40 barbate trichomes arranged, on each side, in 2 diagonal lines above the first scale-row; 2 short rows of barbate trichomes at end of submedial scale-row and 4 (sometimes 5 on tergite II and X) short rows of barbate trichomes at end of posterior scale-row. The number of scales by row ranges from 29-62 on tergites II-X.
Legs short (Fig. 9A), with 8 articles except on legs 1, 14 and 15; last 2 pairs (14-15) without telotarsus, tarsus II terminated in palettes (Figs 7B, C; 9E, F); palettes covered by numerous cuticular setae of different types (Figs 7B; 9F); apodeme of palettes (pa) and claws (ca) extending into distal part of trochanter and linked to the flexor unguiculi muscle, which allows a great flexibility of the palette of the leg pairs 14 and 15, as well as to the claws of legs 1-13, in accordance with the description given by Manton (1956) for Polyxenus lagurus. Legs 1-13 with each trochanter, prefemur (Fig. 9B), femur, tibia and tarsus I bearing a single long and very fine seta; seta of second tarsus longer than claw (Fig. 9C). Legs 14 and 15 with only 2 setae on prefemur (Fig. 9E). Telotarsus bearing an anterior process (ap) with spinous projection longer than claw; lamellate process (plp) thickened and basally pleated; claw with 2 subequal, strongly pointed latero-anterior and posterior teeth (Fig. 9C, D).
Female: large vulval sacs elongated, reaching as far as fourth pair of legs and bearing numerous small setae inserted in parallel circles and sparse longer setae.
Male: all areas of penis with usual thin cuticular setae and about 15 longer setae (holotype). Coxal glands on legs 7-9.
Subadults. 1 male, 1 female: Measurements: Body length (without caudal penicil): 3.20 mm (male no. 8) and 3.90 mm (female no. 13); caudal penicil length: 0.90 mm. 14 pairs of legs, the 14th terminating in a palette; 1 pair of appendagebuds on lateral side of anal valves, from which 15th pair of legs will develop, the future adult stadia having the leg pair 15 terminating in palettes. Other characters as in adults, except no scale-row on telson.
Male: Coxal glands on legs 7-9. Female: large vulval sacs elongated, reaching as far as fourth pair of legs.  Discussion. Phryssonotus brevicapensis sp. n. exhibits all the general characters usually present in the family Synxenidae: long and thin dark barbate trichomes all along the body, tergites covered by tergal scale-shaped trichomes that are striated and arranged in 2 transverse rows along all the tergites except the collum; telson subconical; elongated vulvae; and last 2 leg pairs terminating in palettes instead of claws. It also shows the typical structure of the scale-shaped trichomes found in the genus Phryssonotus. Phryssonotus brevicapensis sp. n. differs from other members of the genus in having 11 tergites and 15 pl; the last 2 pairs (14th and 15th) terminating in palettes; and males with 3 pairs of coxal glands on legs 7-9. These differences are strongly related to biology and development, and justify the creation of a new species. All other species of Phryssonotus have 12 tergites and 17 pairs of legs with the last 2 pairs (16th and 17th) terminating in palettes, and males with 3 pairs of coxal glands on legs 9-11. Due to its shorter length and the position of the coxal glands on legs 7-9, it is similar to Condexenus biramipalpus. The elongated vulvae (ovipositors) of the females also resemble those of Condexenus species in reaching as far as the fourth pair of legs, as opposed to sixth at most in other Phryssonotus species.
Following the discovery of Condexenus biramipalpus from Namibia, it is of great interest to add Phryssonotus brevicapensis sp. n. as the second example of reduction of ring and leg number in the family Synxenidae, whose representatives bear the largest number of segments among the Penicillata. This supports the hypothesis of a trend towards a shortened postembryonic development during the course of evolution of Polyxenida (Condé 1969, Nguyen Duy-Jacquemin 2006. The comparison of the pattern of development is emphasised in the improved scheme (Fig. 10), in which the shortest development pattern is seen in Lophoturus madecassus (Marquet et Condé, 1950). The two new species described in the present work strongly support this evolutionary trend among penicillate families.