Atheris matildae Menegon, Davenport & Howell

Menegon, Michele, Davenport, Tim R. B. & Howell, Kim M., 2011, Description of a new and critically endangered species of Atheris (Serpentes: Viperidae) from the Southern Highlands of Tanzania, with an overview of the country’s tree viper fauna, Zootaxa 3120, pp. 43-54 : 44-50

Atheris matildae Menegon, Davenport & Howell sp. nov.

( Fig. 1 –3)

Holotype. Adult male, MTSN 9344, collected in a forest fragment in Southern Tanzania, at about 1995 m by Omari Kibure and Obadia Mwaipungu in February 2009; fixed in 70% EtOH, tissue fixed in 90% EtOH.

Paratypes. 2 adult males, MTSN 9399 and MTSN 9418 and an immature MTSN 9417 collected in February 2011 at the same locality as the holotype, by Michele Menegon, Tim Davenport and Sophy Machaga.

Additional material. 10 specimens collected at the type locality between March and April 2011 and being kept alive for conservation purposes. 4 are males, 5 are females and 2 are immatures. Among them there is the adult female individual shown in Fig. 3.

Type locality. Remote fragmented montane forest in Tanzania's Southern Highlands. Precise locality withheld until conservation insurance population secure. Additional information on the locality can be obtained for scientific purposes from the authors upon request. (www.atherismatildae.org)

Diagnosis. Atheris matildae sp. nov. is distinguished from all other members of the genus except A. ceratophora by the presence of two to three very enlarged erect, hornlike, supraciliary scales. It is distinguished from A. ceratophora by the combination of the following morphological and molecular features, based on the data from 69 specimens from all over the known range of A. ceratophora : (1) its larger size, TL of A. matildae type is 643mm (the biggest male A. ceratophora ever recorded does not exceed 510mm TL), (2) higher count of maximum transverse head scales (max. 20 in A. ceratophora , 28 in A. matildae ), (3) four subequal suprarostral scales in A. matildae , the two central ones of the same size and the outer ones double in size in A. ceratophora , (4) marked difference in dorsal scale microdermatoglyphic pattern (irregular smooth surface in A. ceratophora , presence of papillae-like ridges in A. matildae ), (5) in A. matildae , an extensive black marking across the frontal part of the mouth, including part of nasal, rostral, mental and few infralabial scales is often present, the above described colour feature has not been recorded in the examined A. ceratophora specimens and photographs. Genetic divergence of mitochondrial gene cytochrome b between A. ceratophora collected at type locality and A. matildae expressed as actual substitution difference is 3.18% based on uncorrected p-distance of 0.03180.

Paratypes and additional material variation. Details and meristics for the type series are summarized in Table 1 . A total of 13 specimens have been observed, three of them are paratypes. The most significant differences between holotype and paratype specimens are in body colouration (see Fig. 2). The young specimen MTSN 9417 tends to be more greenish, the zigzag ornamentation is more conspicuous and the top of the head is marbled in green/yellow. The two adult individuals, both males, are similar in colouration to holotype, with a back dorsum and a bright yellow zigzag dorsolateral pattern. Ten additional specimens have been recently collected and are being kept alive for conservation purposes. 5 are males, 5 are females, and 2 are young. A black patch around nasal, rostral, mental and first infralabials is present in most of the observed males but also in few females and immature individuals. Males in general tend to be darker with belly suffused with black. Adult females tend to be more yellow, in some cases with immaculate throat and belly; horn-like scales are yellow with black outer edges. Side of the head can be completely yellow or with black patches at the tip of the scales. In preservation the specimen retains the original colouration (see Fig. 1 ).

FIGURE 2. A. matildae paratypes showing body shape, colouration and head details. Top - down: MTSN 9399; MTSN 9418 and MTSN 9417.

FIGURE 3. Illustration showing the variation in colour of the rostral and chin area, The black patches are present in many individuals of both sexes.

A. matildae A. matildae A. matildae A. matildae A. ceratophora

Specimen number MTSN 9344 MTSN 9417 MTSN 9418 MTSN 9399 n = 53 Description of holotype. Adult male preserved in 70% EtOH. Snout-vent length (SVL) 540.7 mm, tail 96.0 mm, rostral width 2.9 mm, rostral height 0.8 mm; eye diameter (vertical) 3.2 mm; snout to eye 3.3 mm. A heavybodied forest viper, sub-quadrangular in cross-section, with a rather thick prehensile tail (SVL/Tail approximately 5.7 times); head pear-shaped, with a very distinct neck, rounded snout and swollen supraorbital region that does bear two/three elongated, horn-like scales; eyes relatively large, laterally placed, and with a horizontal diameter approximately 3/4 of the snout length. Crown of head covered in small scales, slightly larger over the temporal region (maximum transverse head scales—28); they bear a prominent keel and become mucronate over the head; the rostral is flattened, rectangular, about 3.5 times broader than high, contacting first supralabials and four small; unkeeled, roundish, subequal suprarostrals, nasal wider than high, with raised, embossed posterior edge, nostril circular and approximately in the centre of the nasal; internasals 5, all strongly keeled; interorbitals 9, keeled; circumoculars 16–16, not keeled but terminating in black blunt knobs; 1 row of suboculars present; circumoculars separated from nasals by two to three rows of feebly knobbed scales; a row of three irregular scales, bordering supralabials between nasal and lower circumoculars; supralabials 10–10, the first three smaller, and 6–8 with a swollen lower edge; infralabials 10–10, posteriormost with swollen upper edge and first in contact at the midline behind the mental; mental triangular, approximately twice as wide as deep; gulars bordering chin shields feeblykeeled, but prominently keeled towards the rictus; 2 preventrals, first largest; 150 ventrals; 49 undivided subcaudals (including spine); anal entire; 25 rows dorsal scales anteriorly, 26 rows at midbody, 19 rows posteriorly.

FIGURE 4. Dorsal scale microdermatoglyphic pattern of A. matildae (A–B) and A. ceratophora : (C–D). Note in B the papillaelike ridges covering the keratin layers on the scale of A. matildae .

Hemipenes. Both hemipenes are only partially everted. They resemble the A. ceratophora one as described by Emmrich (1997). The sulcus is bifurcate on a typically divided organ. The extreme basal area is naked, followed by an area with enlarged proximal spines, most prominently on the outer side of each lobe. Towards the apex, on the inner side of the sulcus, there are a few smaller scattered spines, while the distal area seems to be characterized by the lack of clearly differentiated ornamentation. A more detailed description of hemipenial morphology will be possible when a fully everted hemipenis becomes available for examination.

FIGURE 6. The forest fragment in the Southern Highlands of Tanzania where A. matildae was collected, and a detail of the forest canopy.

Colouration. Dorsally it appears as a black snake with bright yellow dorso-lateral zig-zag lines. Flanks are marbled in yellow. Dorsum of the head is almost entirely black with scattered yellow scales or groups of scales, sides of the head are mainly yellow with an irregular longitudinal black marking. An extensive black marking across the frontal part of the mouth, including part of nasal, rostral, mental and few infralabial scales is present, by contrast it delimitates an inverted pale triangle. Eyes are light olive green (in life). Throat is yellow; belly is pale yellow to greyish-green, suffused by black speckling; horn-like scales are yellow with black outer edges. In preservation the specimen retains the original colouration (see Fig. 1 ).

Dorsal scale microdermatoglyphics. The surface microstructure of several scales from midbody and the last third of the body of two specimens of A. matildae ( MTSN 9344, 9417) and three specimens of A. ceratophora from Usambara Mountains ( MTSN 5117, 5118, 5121) were examined by scanning electron microscopy, in order to evaluate the intra- and inter-specific differences. Two-dimensional classes of microdermatoglyphics were identified; the coarser one consists of juxtaposed or imbricated layers of keratin with a raised edge, forming a ‘scaly background’. This layer is shared by both A. ceratophora and A. matildae . At greater magnification (4000x) a further pattern of microdermatoglyphics is visible in A. matildae , where papillae-like ridges cover the entire surface of the keratin layer. The latter ornamentation is absent in A. ceratophora specimens from type locality.

Distribution and conservation. Atheris matildae is currently known only from the type series and a few other individuals of both sexes, all collected in a remote montane forest fragment in the Southern Highlands. The site probably represents the remnants of a wider forested landscape, interspersed with plateau grasslands and possibly naturally isolated from other Southern Highland forest blocks. For this reason the forests are of great bio- logical value and now the focus of further exploration and conservation intervention. During the last decade the Southern Highlands have been the subject of extensive biological investigation by the Wildlife Conservation Society. However, this species has not been detected in any other areas. It is therefore probable that A. matildae is a rangerestricted forest species, now relying on just a few forest fragments. A. matildae has an extent of occurrence smaller than 100 km 2 with extent of occurrence, area of occupancy and quality of habitat in continuing decline. According to IUCN guidelines (IUCN 2010) therefore, we propose to list A. matildae as ‘Critically Endangered’ CR B1b(i,ii,iii). Further investigations are being carried out in order to collect more information on this magnificent snake, and a small breeding programme has been established (see www.atherismatildae.org).

Etymology. Atheris matildae is named for TRBD's daughter Matilda Davenport, one of the next generation of herpetologists. We suggest the common name 'Matilda's Horned Viper'.

Figures

FIGURE 1. Comparison of general shape, size and body proportion between A. matildae holotype (left) and a fully grown specimen of A. ceratophora from Udzungwa (MTSN 7506, SVL = 54.2) (right) and an illustration of lateral head scalation.

Tables

TABLE 1. Measurements and scalation of type-series of A. matildae, with data of A. ceratophora for comparison.

Type	Holytype	Paratype	Paratype	Paratype	N/A
Sex	Male	Inmmature	Male	Male	Males only
Head Lepidosis
Suprarostrals (SRO)	4	4	4	4	5–9
Interorbitals (IOS)	12	12	121	12	7–11
Maximum transverse head scales (MTHS)	28	28	27	28	19–20
Circumorbital scales (COS)	16	16	16	162	13–19
Interoculabials (IOL)	1	1–2	1	1–2	0–1
Interocunasals (ION)	3–4	4	4	3–4	2–4
Supralabials (SL)	10	10	10	10	7–11
Infralabials (IL)	11	11	11	11	8–12
Body scalation
Midbody Scale Rows (MSR)	26	27	26	26	19–25
Ventrals	150	142	149	150	136–150
Subcaudals	49	44	50	49	49–58
Max length (SVL+Tail) in mm	643 (547+96)	391 (334+57)	625 (532+93)	631 (538+93)	510 (416+94)
SVL/Tail	5.7	5.85	5.7	5.78	5.4 – 5.8 range