58 



D.G. BROADLEY AND V. WALLACH 



IRSL = Instituit d'Rechereche Scientifique, Lwiro, Democratic 

 Republic of Congo (DRC); UNAZA = Universite National du Zaire, 

 Kisangani, DRC; VW = Van Wallach dissection number (museum 

 deposition of specimen unknown). 



CHARACTER ANALYSIS 



1. Rear maxillary teeth. The three rear maxillary teeth of Thrasops 

 flavigularis (type species) and T. jacksonii are enlarged and sepa- 

 rated from the small anterior teeth by a diastema, they taper from 

 base to tip and have slight ridges anteriorly and posteriorly (Fig. 1 A, 

 Group B dentition of Jackson & Fritts, 1995). The posterior ridge 

 becomes blade-like in some genera, e.g. Heterodon (Kardong, 1979), 

 Thamnophis (Wright, etal, 1979) mdStegonotus (Jackson & Fritts, 

 1995). 



The same teeth in Rhamnophis aethiopissa (Fig. IB) and R. batesi 

 (Fig. 1 C) are curved, with sharp anterior and posterior ridges, but not 

 nearly as well developed as in the 'Dagger-tooth Vine Snake' of the 

 Uluguru Mountains, in which the ridges are broadest midway along 

 the tooth, which is leaf-shaped, narrowing at the base (Fig. IF). In 

 Dispholidus and Thelotornis the three greatly enlarged rear maxil- 

 lary teeth are deeply grooved (Group D dentition of Jackson & 

 Fritts, 1995), but these genera retain a strong ridge on the anterior 

 face of the fangs. In Thelotornis, this ridge arises within the groove, 

 so that the venom canal is divided, before petering out well before 

 the fang tip (Fig. 1G, after Meier, 198 1 , fig 4). In Dispholidus on the 

 other hand, the ridge runs along the anterior edge of the groove (Fig. 

 1H, after Meier, 1981, fig 2). 



With regard to number of maxillary teeth, Rhamnophis aethiopissa 

 (16 to 20 + 3) resembles Thrasops spp. (17 to 18 + 3), but R. batesi 

 (30 to 35 + 3, Fig. 1C) is divergent in this respect. The Dagger-tooth 

 Vine Snake has 14 + 3, thus matching Thelotornis (11 to 16 + III) in 

 actual tooth number. Dispholidus shows a marked reduction in 

 number of anterior teeth to 4 to 8 + III. Counts of maxillary tooth 

 sockets are much higher in the Philothamnini: 1 7^48 in Philothamnus 

 and 20-33 in Hapsidophrys. 



2. Dental (Duvernoys ') gland. This gland is small in Thrasops and 

 Rhamnophis (Kochva, 1978), larger in Thelotornis (but smaller than 

 the orbit), still larger in the Dagger-tooth Vine Snake (subequal to 

 the orbit) and reaches its maximum development in Dispholidus 

 (Kochva, 1978), with a large, purely serous, slightly branched, 

 tubuloacinous Duvernoy's gland, the tubule walls highly folded, 

 increasing the storage space within the gland (Taub, 1967). thus 

 constituting a reservoir (Underwood, 1997). The mechanism of 

 delivery of toxic dental gland secretions by low pressure systems 

 has been demonstrated for Boiga irregularis (Kardong & Lavin- 

 Murcio, 1993) and is effective regardless whether or not the teeth are 

 grooved (Weinstein & Kardong, 1994). 



3. Skull. The Dispholidini were first recognised (as a subfamily) 

 by Bourgeois (1968) on the basis of their similar skull morphology 

 (Fig. 2). She drew attention to the forked ectopterygoid, large optic 

 fenestra and interorbital vacuity (also noted by Underwood, 1967). 

 The ectopterygoid is shallowly forked in Thrasops, Thelotornis and 

 the Dagger-tooth Vine Snake, but is very deeply forked in both 

 species of Rhamnophis and in Dispholidus. Underwood (1967) 

 noted the absence of a Vidian canal in the skulls of Thrasops and 

 Thelotornis, but Vaeth (1982) found a short, but distinct, Vidian 

 canal in the skulls of three Thrasops jacksonii. 



4. Pupil shape. The pupil is round in Thrasops and Rhamnophis 

 (Fig. 3) as in the Philothamnini, but in Dispholidus and the Dagger- 



tooth Vine Snake it may be more pear-shaped, due to an anterior 

 prolongation. Thelotornis is distinguished by its horizontal 'key- 

 hole' shaped pupil (Fig. 4B-D). 



5. Visceral anatomy. The Dispholidini can be characterized by the 

 following visceral characteristics (Tables 2-\): umbilical scar-vent 

 interval 8-12% total ventrals; hyoid short with posterior tips at 7- 

 10% SVL, heart short, 1.5-3.1% (mean 2.4%); right systemic arch 

 reduced to 0.20-0.40 left systemic arch diameter; liver narrow with 

 midpoint at 43^t6% SVL; gall bladder craniad of pancreas and 

 spleen; testes normally unipartite but occasional specimens with bi- 

 or tri-partite organs (the additional segments being small sections 

 separated from the main body either posteriorly or anteriorly); 

 kidneys compact but segmented (15—45 segments); no tracheal 

 lung; trachea with narrow, well-separated cartilages that lack free 

 tips, tracheal membrane expanded to 2.0-4.0 (mean = 2.9) times the 

 circumferential width of the rings; weak development of the cardiac 

 lung to midheart level; tracheal entry into right lung subterminal, 

 right lung with small anterior lobe and small orifice; right lung 

 elongate (69-70% SVL), extending to 94-97% body length, cranial 

 vascular portion 0.15-0.25 lung length, usually with midventral 

 avascular strip, caudal saccular portion long 0.75-0.85 lung length; 

 faveolar parenchyma arranged in 2-3 tiers with pattern of transverse 

 smooth muscle ribs enclosing rows of paired faveoli; semisaccular 

 portion of lung short (0.10-0.20 vascular lung length) with abrupt 

 termination of parenchyma along a transverse border. 



The hemipenes of the genera Thrasops, Dispholidus and 

 Thelotornis appear to be similar, being simple, capitate, with an 

 undivided sulcus. There are large basal spines which diminish in size 

 distally and are replaced by calyces on the distal cap (Bogert, 1940). 

 The organs of the Dagger-tooth Vine Snake show little difference, 

 the nude basal portion has four large hooks, the medial portion is 

 spinose and the apical portion is calyculate. The hemipenes of 

 Rhamnophis have not yet been described. 



6. Dorsal head coloration. The development of complex head 

 patterns may aid in species recognition. All four species of Thrasops 

 have the head uniform olive when subadult, eventually becoming 

 uniform black. Rhamnophis batesii has a uniform brown or black 

 head, while that of/?, aethiopissa is green, with the shields margined 

 with black. A somewhat similar black vermiculation on a yellow or 

 green ground is found in males of some populations of Dispholidus 

 typus, but many have no colour pattern. The Dagger-tooth Vine 

 Snake has dark margins to the head shields and yellow labials. The 

 four species of Thelotornis can be distinguished by the colour 

 pattern of the head (Broadley, 2001 ). The top of the head is uniform 

 green in T kirtlandii (Fig. 4B), T usambaricus and some T. 

 mossambicanus, but blue-green with black and pink speckling in T 

 capensis (Fig. 4D). The temporals are uniform green in T kirtlandii 

 (Fig. 4B) and T usambaricus, brown with black speckling in T 

 mossambicanus (Fig. 4C), and pink margined with black in T 

 capensis (Fig. 4D). The supralabials are uniform or with faint green 

 or grey stippling in T kirtlandii, but the other taxa have black spots, 

 usually including a speckled black triangle on the sixth labial. 



7. Throat pattern. All members of the Dispholidini (and some 

 members of the Philothamnini) can inflate the throat in a threat 

 display, reaching its maximum development in Dispholidus. 

 Chippaux (1999, PI. 17) illustrates this phenomenon in Thrasops 

 flavigularis, where the black dorsum contrasts with the pale throat, 

 but in T. jacksonii the throat often becomes entirely black. 

 Rhamnophis has the dark green dorsal scales bordered with black, 

 the throat is yellowish in R. batesii and green in R. aethiopissa. 

 Dispholidus comes in a wide range of colour patterns, but usually 



