DIGNATHODONTIDAE, Cook, 1896
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2011.00803.x |
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persistent identifier |
https://treatment.plazi.org/id/8A1EA639-FFB0-5079-FEA7-FA785334BB66 |
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treatment provided by |
Marcus |
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scientific name |
DIGNATHODONTIDAE |
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DIGNATHODONTIDAE View in CoL View at ENA
The epipharynx of Henia vesuviana was regarded by Attems (1929: fig. 200) as a small field lying proximal to an expansive labrum. We instead identify the large field covered with branching spines as the clypeal part of the epipharynx because it has the typical shape of the clypeal part in Geophilidae and Linotaeniidae (i.e. its border with the labral part of the epipharynx concave medially) and because of its relationship to the anterior branch of the fulcrum that consistently envelops the clypeal part and contacts the labral part at its tip ( Fig. 29A, C View Figure 29 , fu). Our interpretation maximizes the correspondences between Henia and Dignathodon , the latter for which the components of the epipharynx have more straightfor- ward identities (e.g. distinct labral mid-piece and side-pieces, Fig. 29C View Figure 29 , as can likewise be discerned in other species of Henia , in particular those formerly classified as Scotophilus such as H. bicarinata or H. illyrica ; see Meinert, 1870: table III, fig. 7; Latzel, 1880: fig. 83; Brolemann, 1930: fig. 152).
Epipharynx: In Henia vesuviana , the labral part of the epipharynx is extremely reduced both medially and laterally, the labrum being represented only by a band of long bristles that are not distinctly differentiated into mid-piece and side-piece elements. The labral bristles are all slender, undulating, and bear short spinules, especially on their distal parts. The clypeal part of the epipharynx is bilobate as in most Geophilidae , most of its surface covered with dense, slender spines except for the proximo-lateral part, which displays an abrupt transition to parallel ridges ( Fig. 29A View Figure 29 , upper inset). These ridges are separated by shallow grooves and taper to their distal tips, and each has numerous sharp spinules on it; the shape of the ridges suggests that they are fused spines. Proximally on the clypeal part of the epipharynx is a lenticular field isolated by a furrow. This field has a smooth surface and bears five sensilla coeloconica arranged as a more or less transverse band ( Fig. 29A View Figure 29 , lower inset).
The labral part of the epipharynx in Dignathodon microcephalus consists of a small mid-piece with either three or four strong, anteriorly directed teeth, and a small, subtriangular side-piece ( Fig. 29C View Figure 29 , lsp). The clypeal part of the epipharynx is reniform in outline, with a shallow, bilobate anterior margin. It is smooth apart from bearing c. 12 sensilla coeloconica distributed in approximate bilateral symmetry on the medial part ( Fig. 29C View Figure 29 , inset). The fulcrum bounds the entire lateral margin of the clypeal part of the epipharynx.
Hypopharynx: The hypopharynx of Henia vesuviana is relatively elongate and slender ( Fig. 29B View Figure 29 ). It tapers slightly along its distal half apart from a distinct expansion at its distal tip, which is markedly bilobate. In lateral aspect the hypopharynx is relatively flat on its frontal surface. Most of the hypopharynx is beset with dense scales that are aligned in regular, concentric bands; these scales are developed as simple spines or birfurcate spines further from the median longitudinal cleft and become more elaborately branching medially, each scale bearing numerous slender, pointed spines with their apices pointed distomedially. Amidst the scales on the lips of the hypopharynx are at least four sensilla coeloconica represented by two bilaterally symmetrical pairs ( Fig. 29B View Figure 29 , arrows and inset). The distal tip of the hypopharynx bears long, dense spines resembling those along the innermost part of the lips (if additional sensilla are present on the distal tip they have not been detected in this mass of spines).
The hypopharynx of Dignathodon microcephalus is relatively shorter than that of Henia vesuviana , but it also has a strongly bilobate distal tip ( Fig. 29E View Figure 29 ). The scales along much of the frontal surface are aligned in concentric bands and have blunt apices, but those in the inner- and distalmost parts have a fringe of spines ( Fig. 29D View Figure 29 ). Indeed, on the distal tip and backside of the epipharynx the spine bands are nearly uninterrupted fringes of slender, sharp spines, the limits of individual scales being difficult to discern. As in Henia vesuviana , four sensilla coeloconica are distributed as two pairs per side amidst the scales on the distal part of the frontal surface.
Mandible: The mandibular gnathal edge in Henia vesuviana bears a single row of c. 25 slender teeth that are nearly parallel-sided along most of their length ( Fig. 30A View Figure 30 , pl). Seen from the inner side, the entire lamina of teeth originates from a common base ( Fig. 30C View Figure 30 ). Nearly the entire outer surface of the gnathal lobe apart from the basalmost part has a dense covering of simple spines ( Fig. 30B View Figure 30 ). The length and robustness of the spines increase abruptly at an arc that runs close to the base of the gnathal lobe on its ventral side (such that long, relatively robust spines are developed along the ventral margin) but short spines extend close to the gnathal edge on the dorsal side. Close to the gnathal edge the long spines are organized as fringes from a common base, with a few such fringes paralleling the teeth aligned on the gnathal edge ( Fig. 30A View Figure 30 ) ( Brolemann, 1930: fig. 168). A condyle is lacking on the gnathal lobe and even a ridge or other such articulatory process is undefined ( Fig. 30B View Figure 30 ). The inner surface of the mandible is covered by scales with fringes of spines oriented towards the gnathal edge; towards the inner proximal base of the gnathal lobe the spines gradually decrease in length and the scales are smoother, taking the form of mere humps.
The mandible of Dignathodon microcephalus has a single pectinate lamella ( Fig. 30E View Figure 30 , pl) with 26 teeth that gradually shorten towards the proximal end of the gnathal edge. The outer surface of the mandible is mostly smooth, with strong scales confined to a band near the ventral margin. These scales bear a few short spines along their distal edge. Spiniferous scales continue onto the inner surface of the mandible ( Fig. 30D View Figure 30 ); most of this surface bears large scales but those closer to the gnathal edge are much smaller. The mandibular condyle is developed as a strong ridge ( Fig. 30E View Figure 30 , co); a lamina condylifera is not delimited.
Epipharynx: Although a labrum cannot be identified in Aphilodon weberi , this is evidently an autapomorphic loss by comparison with other congeners, such as the type species, A. spegazzinii Silvestri, 1898 , in which side-pieces are distinctly defined ( Silvestri, 1909: fig. 9.3).
As described above for Dignathodontidae , the clypeal part of the epipharynx has its lateral margin entirely enveloped by the fulcrum ( Fig. 29F View Figure 29 , fu). The clypeal part is broadly elliptical, its anteromedial part bearing branching scales with the apices of the short spines directed distally, similar to those on the surrounding parts of the clypeus ( Fig. 29F View Figure 29 detail at right). A fine ornament of granules covers the epipharyngeal scales, which have a polygonal shape; the scales in the lateral part mostly lack a fringe of marginal spines. The granulate scales are confined to the anterior two-thirds of the epipharynx, the proximal third having only weakly defined polygonal scutes but wholly lacking granulation, the transition between granulate and nearly smooth fields being abrupt across the width of the epipharynx. A pair of sensilla coeloconica is situated proximo-medially, in the smooth band ( Fig. 29F View Figure 29 , inset at left).
Hypopharynx: The hypopharynx of Aphilodon weberi is quadrate in frontal view and moderately arched across its width ( Fig. 29G View Figure 29 ). The lips and a broad extent lateral to them are densely beset with scales that each bears a fringe of numerous slender spines with their apices directed medially. These scales continue onto the backside of the hypopharynx, where their spines are shorter than those on the distal tip and frontal surface. The scales abruptly terminate such that much of the backside has a smooth, unsculpted surface ( Fig. 29H View Figure 29 ). The distal tip has only slight expression of being bilobate (unlike Dignathodontidae ), and although the studied material is distorted, a median incision is apparently lacking on the backside. Sensilla have not been detected amidst the spiniferous scales on the frontal surface or distal tips; given their general presence in Geophilomorpha this is more likely due to them being few in number or concealed by the density of scales rather than their absence.
Mandible: The mandibles of Aphilodon weberi have been examined by light microscopy only and appear to correspond closely to those described in A. spegazzinii ( Silvestri, 1909: fig. 4). The gnathal edge bears a single pectinate lamella composed of numerous slender and evidently simple teeth.
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