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| Laodracon gen. nov. Brakels, Sitthivong, Wang, Nguyen & Poyarkov Laodracon carsticola Sitthivong, Brakels, Xayyasith, Maury, Idiiatullina, Pawangkhanant, Wang, Nguyen et Poyarkov, 2023 |
Abstract
We describe a unique new species and genus of agamid lizard from the karstic massifs of Khammouan Province, central Laos. Laodracon carsticola gen. et sp. nov. is an elusive medium-sized lizard (maximum snout-vent length 101 mm) specifically adapted to life on limestone rocks and pinnacles. To assess the phylogenetic position of the new genus amongst other agamids, we generated DNA sequences from two mitochondrial gene fragments (16S rRNA and ND2) and three nuclear loci (BDNF, RAG1 and c-mos), with a final alignment comprising 7 418 base pairs for 64 agamid species. Phylogenetic analyses unambiguously place the new genus in the mainland Asia subfamily Draconinae, where it forms a clade sister to the genus Diploderma from East Asia and the northern part of Southeast Asia. Morphologically, the new genus is distinguished from all other genera in Draconinae by possessing a notably swollen tail base with enlarged scales on its dorsal and ventral surfaces. Our work provides further evidence that limestone regions of Indochina represent unique “arks of biodiversity” and harbor numerous relict lineages. To date, Laodracon carsticola gen. et sp. nov. is known from only two adult male specimens and its distribution seems to be restricted to a narrow limestone massif on the border of Khammouan and Bolikhamxai provinces of Laos. Additional studies are required to understand its life history, distribution, and conservation status.
Keywords: Biodiversity, Endemism, Indochina, Karstic landscape, Laodracon carsticola, Phylogeny, Southeast Asia, Taxonomy
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| Comparison on the diagnostic characters on tails between Diploderma and Laodracon carsticola gen. et sp. nov. A, B: Tail basis of D. splendidum (A: Kunming Institute of Zoology 040155) and Laodracon carsticola gen. et sp. nov. (B: National University of Laos R.2022.01, holotype) is shown in dorsolateral (1) and ventral (2) views. Photographs by Kai Wang (A), and Nathanaël Maury (B). |
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| Holotype of Laodracon carsticola gen. et sp. nov. (NUOL R.2022.01), adult male, in life A: General lateral view; B: General ventral view; C: General dorsal view; D: Head in lateral aspect; E: Head in ventral aspect; F: Head in dorsal aspect; G: Tail base in ventral aspect; H: Tail base in dorsal aspect; I: Volar aspect of right foot; J: Opisthenar aspect of left foot; K: Volar aspect of left hand; L: Opisthenar aspect of right hand. Scale bar equals to 10 mm for A–C, to 5 mm for D–L. Photographs by Nathanaël Maury. |
Laodracon gen. nov. Brakels, Sitthivong, Wang, Nguyen & Poyarkov
Diagnosis: A genus of the subfamily Draconinae characterized by the following characteristics: body size moderate (male SVL 94.5–101.6 mm); tail base distinctively swollen at base; tail scales at swollen base distinctively enlarged dorsally and ventrally, heterogeneous dorsally and laterally, but homogeneous ventrally, all keeled and protruding with keels mostly misaligned; tympanum exposed; dorsal scales heterogeneous, strongly keeled, enlarged scales arranged in somewhat irregular dorsolateral series close to vertebral crest; nuchal and dorsal crest scales relatively short and thick, not elongated into lanceolate spines; post-occipital and post-orbital spines absent; gular scales mostly homogeneous in size, not decreasing in size medially; scales on the lateral surfaces of jaws subequal in size across gular region; no preanal or femoral pores.
Distribution: To date, Laodracon Gen. nov. is known only from a single limestone outcrop at the Rock Viewpoint tourism concession area within Nam Sanam-Phou Pha Marn PPA., Khounkham District (hereafter Dist.), Khammouan Province, Laos (Figure 1). This limestone massif represents the northernmost portion of the larger Central Indochina Limestone landscape which extends from southern part of Bolikhamxai Prov. in the north-west and extends into Phong Nha-Ke Bang National Park, Quang Binh Prov., Vietnam, in the south-east. Therefore, it is possible that Laodracon Gen. nov. also occur in other karst area within this landscape in central Laos and adjacent areas of Vietnam.
Etymology: The generic name “Laodracon” is a Latinized noun in masculine nominative singular form, which gives reference to its area of occurrence in central Laos. The word “dracon” is derived from Greek “δράκων” (drakon) meaning “dragon” or a “basilisk” and refers to mythological serpents; it is widely used as a part of genus-level names within the subfamily Draconinae. We recommend the name “Laos Karst Dragons” as common name of the new genus in English.
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| Paratype of Laodracon carsticola gen. et sp. nov. (NUOL R.2022.02), adult male, in life. A: General dorsal view; B: General ventral view; C: Head in lateral aspect; D: Head in ventral aspect; E: Head in dorsal aspect; F: Volar aspect of left foot; G: Volar aspect of right hand; H: Tail base in ventral aspect; I: Partially everted hemipenial structures; Scale bar equals to 10 mm for A–B, to 5 mm for C–I. Photographs by N. Maury |
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| Natural habitat of Laodracon carsticola gen. et sp. nov. in Nam Sanam-Phou Pha Marn PPA., Khounkham Dist., Khammouan Province, central Laos A: Macrohabitat of the new species on karst pinnacles. B: A specimen of Laodracon carsticola gen. et sp. nov. in situ (not collected) showing disruptive camouflage that hides the lizard while it perches on limestone. Photographs by Santi Xayyasith. |
Laodracon carsticola sp. nov.
Diagnosis: The new species is defined by a combination of generic characters of Laodracon Gen. nov. listed above, and additionally is characterized by the following combination of morphological traits: tail long, TAL/SVL 2.11; head robust, HW/HL 0.77; hind limbs thin, long, HLL/SVL 0.73; transverse scale rows around midbody 34; subdigital lamellae under fourth finger 15/15; subdigital lamellae under fourth toe 28/28; gular pouch present; transverse gular fold present, distinct; scales on ventral, lateral and dorsal surfaces of head and body strongly keeled; dorsal background coloration black, with three white cross-bands formed by a series of large blotches and irregular white spots; gular with thin, dark gray reticulated patterns and a median blue gular spot.
Etymology: The specific epithet “carsticola” is a noun in the nominative case singular used in apposition, derived from German “Karst” (originally from Latin “carsus”) used for “limestone landscapes” and “cola”, a Latin word meaning “resident”, “inhabiting” or “dwelling in”. The name is given in reference to the limestone mountain habitat of the new species. We recommend the names “Khammouan Karst Dragon” and “Chi Pom Pou Hin Poun Khammouane” for the common names of the new species in English and Lao languages, respectively.
ກະປອມພູຜາມ່ານ, ກິປອມ ພູຫີນປູນຄຳມ່ວນ
ພູຜາມ່ານ ເມືອງຄູນຄຳ ແຂວງຄຳມ່ວນ
Saly Sitthivong, Peter Brakels, Santi Xayyasith, Nathanaël Maury, Sabira Idiiatullina, Parinya Pawangkhanant, Kai Wang, Tan Van Nguyen and Nikolay A. Poyarkov. 2023. Hiding on Jagged Karst Pinnacles: A New microendemic Genus and Species of A Limestone-dwelling Agamid Lizard (Squamata: Agamidae: Draconinae) from Khammouan Province, Laos. Zoological Research. 44(6); 1039-1051. DOI: 10.24272/j.issn.2095-8137.2023.062
