Acanthocercus ceriacoi

Habitat and Natural History notes. In Cangandala National Park and surrounding areas, the species is commonly found dwelling in trees, several meters above ground. The park lies at an approximate elevation of 1000 m and its climate is similar to that of the Angolan central plateau, with vegetation mostly dominated by miombo woodlands (Fig. 7), with Brachystegia wangermeeana, B. floribunda, Julbernardia paniculata, Erythrophleum africanum, Combretum spp., and Rhus spp. growing on the red clay soils of the park (Grandvaux-Barbosa 1970). Some small riverine gallery forests also occur in the park. In Uíge Province, the species was found basking on the ground in open-savannah habitat, in an area particularly devoid of trees (Fig. 8). The habitat of this region mainly comprises a mosaic of Zambezian savannah and coffee plantation forests, dominated by the plant genera Hyparrhenia, Celtis, Albizia, Morus and Ficus (Grandvaux-Barbosa 1970). The female paratype (MHNCUP / REP 860) from Uíge Province, collected in November, was active on the ground around midday. After euthanasia and while preparing the specimen for fixing, three well-developed eggs were found in the abdominal cavity of the specimen.

(Figs. 2 – 8)

Description of the holotype. Adult male (Fig. 2). Measurements: snout – vent length (SVL) 143 mm, tail length (TL) 187 mm, head length (HL) 48 mm, head width (HW) 38 mm, head height (HH) 34 mm. Habitus stout, with a large triangular head distinct from body; nasal scale flat to faintly convex, smooth, oval and situated slightly below canthus rostralis, pierced by round nostril in posterior part of scale, directed laterally. Scales on anterior, lateral, and central parts of head large, but smaller from behind ear opening, half the size of large head scales; head scales unequal in size, not oriented in the same direction, usually smooth, sporadically heavily keeled or with a rough surface, with free anterior margins and only sporadically with sensory pits. Fourteen supralabial scales and twelve infralabial scales on both sides; supraocular scales smooth, twelve scales along the canthus rostralis from nasal to behind the eye; six scales from nasal to anterior margin of eye; parietal shield quadrangular; pineal organ small, visible in posterior part of parietal shield. Ear opening large, but smaller than eye, posterior margin lacking semicircle of spinose mucronate scales; tympanum superficial. No nuchal crest present. Gular scales smooth, flat to faintly convex in the anterior part of the gular area; mucronate and spinose in the posterior part, becoming more spiny and smaller towards gular fold. Dorsal body scales a mix of small and smooth matrix scales, sometimes giving the impression of granular scales, and scattered, pale white-edged, enlarged scales. Large scales keeled, sometimes mucronate or spinose, not arranged in clusters, but rather in seven to eight, very indistinct, transverse rows between limbs. Sixty-four dorsal scales along vertebral column from midpoint of pectoral region to midpoint of pelvic region. Vertebral region covered by a mix of small and large scales, forming a pattern distinct from rest of lateral parts of body, with a large set of vertebral scales strongly keeled to smooth or feebly keeled. Ventral body scales smooth, slightly imbricate at posterior margins, in 89 rows from midpoint of pectoral region to precloacal pores. One hundred twenty-six scale rows around body behind forelimbs; 105 around midbody and 80 around body in front of hind limbs. Precloacal scales in two rows (the more anterior weakly developed), twelve pores in the posterior row and seven pores in the row above. Scales on upper side of forelimb unequal in size and strongly keeled, smooth on underside, upper arm scales somewhat larger than largest dorsal body scales. Relative length of manual digits 4 = 3> 2> 5> 1, subdigital lamellae keeled and mucronate, 21 under left 4 th finger. Scales on upper side of hind limb keeled to smooth, becoming completely smooth on underside; scales on upper thighs unequal in size, a mix of small and scattered enlarged scales that are as large as the enlarged dorsal body scales. Fourth toe longest, relative length of pedal digits 4> 3> 2> 5> 1, subdigital lamellae keeled and mucronate, 23 under left 4 th toe. Tail with indistinct whorls of five scale rings (one ring consists of distinctly smaller scales) in its basal portion, caudal scales keeled and mucronate. First third of tail slightly swollen, scales larger than in other parts of the body, strongly robust and keeled. Distal portion of the tail much thinner and slightly depressed. After formalin fixation and six years of preservation in ethanol (Fig. 2) head dark with some brown to orange scales. Gular region bluish and dark from the mental through the throat, whitish in lateral parts. Black patch on shoulders. Ground color of dorsum grayish to brownish, enlarged scales on upper and lateral parts of body and limbs speckled dirty white. Four to five brownish areola-like markings delimited by white pale circles are visible through the vertebral region. Ventral side of body, limbs and tail dirty grayish, speckled with dark spots. Enlarged scales on upper side of tail base distinctly whitish. Scales becoming more brownish-dirty white striped towards tail tip. Coloration. In displaying males (see Fig. 3), head vibrantly blue; neck, shoulders, body and limbs brownish with a pattern of white and black stripes and speckles; a pale vertebral band from the neck to the tail is present, distinct anteriorly between the flanks, becoming more indistinct and on a brown background posteriorly; enlarged dorsal scales of the lower part of the body yellowish, matrix scales greyish becoming brownish on the hind limbs; first half of the tail yellowish, second half of the tail with dark and lighter blue bands. Ventral parts of the body, limbs and tail dirty whitish with a brown patterning coloration on females in life (see Fig. 5). Shoulders brownish with a black patch, some individuals present a pale blue head. Four dark brown, broad transverse bands between limbs, each interspersed by transverse bands composed of a single row of enlarged yellow scales. Upper and lateral parts of tail with brown and whitish / yellowish bands. Ventral parts of the body, limbs and tail dirty whitish with an extensive dark brown pattern. Gular region of a vibrant blue. Regarding its Angolan congeners, the coloration of displaying males (Fig. 3) is overall more similar to A. cyanocephalus than to A. margaritae. However, in A. cyanocephalus, the blue coloration of the head extends to the neck and shoulders, while in A. ceriacoi sp. nov. the blue is limited to the head. The new species is clearly distinct from A. margaritae, in that the latter species has a blue coloration of the head, forelimbs, flanks of the upper part of the body and second half of the tail (not banded as in A. ceriacoi sp. nov.). Variation. Some variations of the type series are shown in Table 2. Snout-vent length 99 – 143 mm (mean 123 mm); Tail length 125 – 187 mm (mean 162 mm), with the ratio TL / SVL 1.26 – 1.31 (mean 1.32); head length 28 – 48 mm (mean 39 mm); supralabial scales on the left side 12 – 14 (mean 13); supraocular scales on the left side 6; temporal scales on the left side 7; scale rows around fore body 121 – 128 (mean 126); scale rows around hind body 74 – 87 (mean 80); subdigital lamellae under Fi 4 21 – 23 (mean 21); subdigital lamellae under TOE 4 21 – 23 (mean 22); precloacal pores 17 – 20 (mean 18).

Diagnosis. Segmentation of the tail into distinct whorls places the new species in the genus Acanthocercus. Within this genus, heterogeneous body scalation refers it to the cyanogaster / atricollis group and the high density of enlarged trunk scales, in combination with a black patch on the shoulder, place it in the A. atricollis complex. Acanthocercus ceriacoi sp. nov. is a medium sized lizard (mean SVL 122.5 mm [99 – 143 mm]; mean total length 285 mm [224 – 330 mm]) for its genus and overall is very similar in morphology to A. cyanocephalus. However, it may be distinguished from all other species of the complex by its meristic characters. The new species has lower scale counts when compared to other species of the A. atricollis complex group (mean scale rows around midbody 108, mean dorsal scale rows 64, mean ventral scale rows 85). In life, displaying males are characterized by a blue coloration of the head; neck, shoulders, body and limbs brownish with a pattern of white and black stripes and speckles; and a pale vertebral band from the neck to the tail, distinct anteriorly between the flanks, becoming more indistinct along a brown background posteriorly.

Comparison with other close related Acanthocercus species. Acanthocercus ceriacoi sp. nov. can be distinguished from other taxa of the A. atricollis complex by the following characters (see Table 2): (a) Acanthocercus atricollis has a larger SVL (mean 129 mm vs. 123 mm) and total length (mean 302 mm vs. 285 mm). It has higher mean counts of scale rows around midbody (112 vs. 108), dorsal scales (67 vs. 63), and ventral scales (87 vs. 85) than A. ceriacoi sp. nov.. The mean number of precloacal pores is higher in A. atricollis than in A. ceriacoi sp. nov. (22 vs 18). Acanthocercus atricollis presents a blue or green head and ventral surface, in some individuals extending to the body, while in A. ceriacoi sp. nov. the blue is limited to the head. (b) Acanthocercus branchi has a smaller SVL (mean 109 mm vs. 123 mm) and total length (mean 262 mm vs. 285 mm). It has higher mean counts of scale rows around midbody (117 vs. 108), dorsal scales (73 vs. 63), and ventral scales (88 vs. 85) than A. ceriacoi sp. nov.. The ranges of these characters largely overlap in both species, although they are higher in A. branchi than in A. ceriacoi sp. nov.. The mean number of precloacal pores is higher in A. branchi than in A. ceriacoi sp. nov. (20 vs 18). (c) Acanthocercus cyanocephalus has a larger SVL (mean 138 mm vs. 123 mm) and total length (mean 334 mm vs. 285 mm). It is morphologically very similar to A. ceriacoi sp. nov. and its meristic differences are subtle. Acanthocercus cyanocephalus has a higher mean dorsal scale count (68 vs. 63), and a lower mean number of ventral scales (80 vs. 85) than A. ceriacoi sp. nov.. The mean number of precloacal pores is higher in A. cyanocephalus than in A. ceriacoi sp. nov. (22 vs 18). The major difference between these two species is the coloration of displaying males, which in A. cyanocephalus is characterized by the blue coloration of the head extending to the neck and shoulders, whereas in A. ceriacoi sp. nov. the blue is limited to the head. (d) Acanthocercus cyanogaster has a smaller SVL (mean 101 mm vs. 123 mm) and total length (mean 255 mm vs. 285 mm). It has lower mean counts of ventral scales (76 vs. 85) than A. ceriacoi sp. nov.. The ranges of this character slightly overlap in the two species, although they are higher in A. ceriacoi sp. nov. than in A. cyanogaster. The mean number of precloacal pores is much higher in A. cyanogaster than in A. ceriacoi sp. nov. (38 vs 18). [A. cyanogaster is not a part of A. atricollis group but is included here due to its morphological similarity and because of the historical use of the name to describe this population]. (e) Acanthocercus gregorii has a smaller SVL (mean 119 mm vs. 123 mm) but greater total length (mean 291 mm vs. 285 mm). A. gregorii has lower mean counts of scale rows around midbody (104 vs. 108) than A. ceriacoi sp. nov.. The ranges of these characters are higher in A. ceriacoi sp. nov. than in A. gregorii. The mean number of precloacal pores is higher in A. gregorii than in A. ceriacoi sp. nov. (22 vs 18). In displaying adult males, A. gregorii are characterized by their bluish-green head and a uniform greenish-blue throat, with a uniform blue body (Klausewitz 1957; Wagner et al. 2018), whereas in A. ceriacoi sp. nov. the blue of the male is limited to the head. (f) Acanthocercus kiwuensis has a smaller SVL (mean 111 mm vs. 123 mm) but greater total length (mean 290 mm vs. 285 mm). A. kiwuensis has lower mean counts of scale rows around midbody (87 vs. 108) and ventral scales (67 vs. 85) than A. ceriacoi sp. nov.. The ranges of this character largely overlap in the two species, although they are higher in A. ceriacoi sp. nov. than in A. kiwuensis. Moreover A. kiwuensis does not possess transverse rows of enlarged scales (Wagner et al. 2018). The mean number of precloacal pores is lower in A. kiwuensis than in A. ceriacoi sp. nov. (10 vs 18). (g) Acanthocercus margaritae has a smaller SVL (mean 112 mm vs. 123 mm) and total length (mean 258 mm vs. 285 mm). It has higher mean counts of scale rows around midbody (136 vs. 108), dorsal scales (103 vs. 63), and ventral scales (101 vs. 85) than A. ceriacoi sp. nov.. The ranges of these characters are lower in A. ceriacoi sp. nov. than in A. margaritae. The mean number of precloacal pores is lower in A. margaritae than in A. ceriacoi sp. nov. (14 vs 18). (h) Acanthocercus minutus has a smaller SVL (mean 101 mm vs. 123 mm) and total length (mean 234 mm vs. 285 mm). It has higher mean counts of dorsal scales (79 vs. 63), and lower mean counts of ventral scales (78 vs. 85) than A. ceriacoi sp. nov.. The mean number of precloacal pores is higher in A. minutus than in A. ceriacoi sp. nov. (26 vs 18). (i) Acanthocercus ugandaensis has a smaller SVL (mean 103 mm vs. 123 mm) and total length (mean 275 mm vs. 285 mm). A. ugandaensis has lower mean counts of scale rows around midbody (94 vs. 108) and ventral scales (73 vs. 85) than A. ceriacoi sp. nov.. The ranges of these characters are higher in A. ceriacoi sp. nov. than in A. ugandaensis. The mean number of precloacal pores is higher in A. ugandaensis than in A. ceriacoi sp. nov. (24 vs 18).

Distribution. Currently, Acanthocercus ceriacoi sp. nov. is only known from the central and northwestern regions of Angola, from central Malanje to Bengo Province in the west and Uíge Province in the north (Fig. 6). It is likely that the species may also be present in the neighboring provinces of Kwanza-Norte and Zaire, as well as in southern Democratic Republic of the Congo.

Etymology. The species is named after the Portuguese zoologist Luis Miguel Pires Ceríaco (1987 – present), head of collections and research at the Museu de História Natural e da Ciência da Universidade do Porto, Porto, Portugal, and invited curator of herpetology at the Museu Nacional de História Natural e da Ciência, Lisbon, Portugal. Luis M. P. Ceríaco has been a major force comprising the new wave of Angolan herpetological studies and a dedicated supervisor to a new generation of Portuguese and Angolan herpetologists. The name is formed in the genitive masculine singular. We propose the English common name of Ceríaco’s Tree Agama, and the Portuguese common name of Sardão Arborícola de Ceríaco.

Holotype. CAS 258430 (field number JVV 9152; Figs. 2 – 3), adult male from Cangandala National Park headquarters [- 9.819417 ° N, 16.653861 ° E, 1089 m a. s. l.], Malanje Province, Angola, collected by Mariana P. Marques, Luis M. P. Ceríaco, Suzana A. Bandeira, Edward L. Stanley and Jens V. Vindum on 14 September 2015. Paratypes. Five specimens, all from Angola: CAS 258429 (field number JVV 9099) adult male from the vicinity of Cangandala National Park headquarters [- 9.818917 ° N, 16.6541 ° E, 1106 m a. s. l.], Malanje Province, same collectors as the holotype on 13 September 2015; CAS 258431 (field number JVV 9460) adult female with the same collecting data as the holotype; CAS 258433 (field number JVV 9261) and CAS 258434 (field number JVV 9262), two adult males, respectively, both from the vicinity of Cangandala National Park headquarters [- 9.818583 ° N, 16.654028 ° E, 1089 m a. s. l.], Malanje Province, same collectors as the holotype on 18 September 2015; MHNC- UP / REP 860 (field number GJ 04564, Figs. 4 – 5), an adult female from near Zulumongo village [- 7.207669 ° N, 15.167342 ° E, 1184 m a. s. l.], Uíge Province, collected by Luis M. P. Ceríaco, Gregorius Jongsma, Stuart Nielsen and Ilola Jorge on 28 November 2019. Additional material. 42 specimens: Malanje Province: CAS 258428, 258432 258435 (field number JVV 9098, 9218, 9440) three adult males from the same locality and collectors as holotype, on 13, 17 and 22 September 2015, respectively; CAS 258436 (field number JVV 9298), an unsexed juvenile from 13.67 km southwest by road of Cangandala National Park headquarters [- 9.819222 ° N, 16.654139 ° E, 1086 m a. s. l.], collected by the same collectors as the holotype on 20 September 2015; NHMUK 1866.6.11. 1 adult male from Duque de Bragança (currently Kalandula) [- 9.1 ° N, 15.95 ° E, 1010 m a. s. l.], collected by Francisco Pinheiro Bayão in 1866 [specimen noted by Bocage (1866) and Boulenger (1885)]; NHMUK 1904.5.2. 26 adult male from Pungo Andongo [- 9.66667 ° N, 15.58333 ° E, 1220 m a. s. l.], collected by William John Ansorge in June / July 1903 [specimen noted by Boulenger (1905)]; NHMUK 1904.5.2. 25 adult male from Bange N’Gola [- 8.433300 ° N, 16.56667 ° E, 723 m a. s. l.], collected by William John Ansorge in the end of 1903 [specimen noted by Boulenger (1905)]; NHMUK 1904.5.2.17 – 24 eight specimens from Quanza River (most likely Duque de Bragança), collected by William John Ansorge at the end of 1903 [specimen noted by Boulenger (1905)]; ZMB 10027 adult male from Malanje [- 9.55 ° N, 16.35 ° E, 1147 m a. s. l.], collected by Friedrich Wilhelm Alexander von Mechow between 1879 and 1881 [specimen noted by Peters (1881)]; MNHNL / Rep / A / Ag 108 – 126, 25 specimens from Capanda Dam area [- 9.72841 ° N, 15.34585 ° E, 859 m a. s. l.], collected by Ana Lavres between January and April 2003 [specimens noted by Ceríaco et al. (2014)]. Bengo Province: AMNH R 48179 adult female from Dande [- 8.47279 ° N, 13.361224 ° E, 45 m a. s. l.], collected by Rudyerd Boulton and Herbert Lang (Vernay-Lang expedition to Angola) on 4 August 1925 [specimen noted by Wagner et al. (2018)]. The records from Cassange [- 9.583330 ° N, 17.866670 ° E, 955 m a. s. l.], Malanje Province, noted by Bocage (1895), as well as those from Duque de Bragança [- 9.1 ° N, 15.95 ° E, 1010 m a. s. l.], Malanje Province, noted by Ferreira (1903) cannot be confirmed, as these specimens were destroyed in the fire that engulfed the Lisbon Museum in 1978. However, due to their geographic proximity and similar habitat, they are here tentatively identified as the newly described species.