Vertebrates (pdf)

	Preserving a gentle reef fish giant
	Newcomers to the local fish list, or unwelcome exotics!
	The South China Cascade Frog, Amolopis ricketti, found in Hong Kong
	The occurrence of Sphenomorphus incognitus in Hong Kong with notes on its diagnostics features and distribution

The occurrence of Sphenomorphus incognitus in Hong Kong with notes on its diagnostic features and distribution (pdf)

The skink Sphenomorphus incognitus is very similar to Sphenomorphus indicus, a widely distributed species from South Asia to Indochina and northward to south and central China. The only clear-cut difference is the presence of a patch of enlarged scales at the back of the thigh in S. incognitus (Zhao et al., 1999). Sphenomorphus incognitus is also slightly larger in size but the adult snout-vent length overlaps between the two species (see tables in Zhao et al., 1999). Various researchers also report differences in general body colour and the shape of the lateral stripe (Zhao et al., 1999) but colour markings of these wide-ranging skinks are quite variable and there is no consensus as to how to separate the two species based on colour markings alone. There is also a difference in life-history in which S. incognitus is oviparous while S. indicus is ovoviviparous (Zhao et al., 1999), but this has limited use as an identification character. Sphenomorphus incognitus is endemic to China and, until recently, has only been recorded from Fujian, Taiwan, Hubei, Guangxi, Yunnan and Hainan (Zhao & Adler, 1993; Zhao et al., 1999). This skink was discovered in Guangdong during the rapid biodiversity surveys carried out Kadoorie Farm and Botanic Garden (2002a) and was subsequently found in Wutongshan just across the border (Kadoorie Farm and Botanic Garden, 2002b). [See Addendum Page 31]

It is likely that this species also occurs in Hong Kong and has been confused with S. indicus. Romer (1975) did report a Sphenomorphus skink with enlarged scales at the back of thigh from the Shek Kong area. However, he decided that more specimens were needed to draw a conclusion. To address this, Sphenomorphus specimens collected by the author from Hong Kong over the years and those in the St. Louis School and Kadoorie Farm & Botanic Garden collections were examined to determine their identity based on the scalation. Their markings, in particular the lateral stripes, coloration and snout-vent length were also noted to see if there is a consistent difference.

Both Sphenomorphus incognitus and S. indicus have been collected from Hong Kong. Some of the older specimens of S. incognitus were mis-identified as S. indicus. Adult S. incognitus is generally larger than S. indicus and the snout-vent length can exceed 90 mm (see Table 1). However, this is not be a good character for differentiating juvenile S. incognitus from S,. indicus. The colour pattern also shows a slight difference; the upper edge of the dark lateral stripe in S.incognitus is jagged while in S. indicus, it is smooth. Dorsally, S. incognitus is bronze in colour speckled with light and dark spots. Sphenomorphus indicus is more or less uniform brown. The picture of ‘S. indicus’ in Karsen et al (1998) actually depicts a typical S. incognitus. There is also some difference in habitat preference, with S. incognitus favouring riparian forests and often seen basking on stream banks while S. indicus is more frequently found in forests and often encountered along forest paths. However, both species are sympatric in good forests in the central New Territories like Tai Po Kau and Shing Mun.

Table 1: Measurements of Sphenomorphus incognitus and Sphenomorphus indicus from Hong Kong.

Due to the confusion of the two species in the past, earlier records of S. indicus from Hong Kong should be treated with caution. Re-examination of the available specimens and recent observations suggest that S. incognitus has a wide distribution in the New Territories covering the north-east, central and the western part. It also occurs in the Sai Kung Peninsula. Sphenomorphus indicus seems to be restricted to the Tai Mo Shan massif in central New Territories. With forests becoming more mature, it is likely that the latter species will spread to other parts of the New Territories.

Kadoorie Farm and Botanic Garden. (2002). Report of a Rapid Biodiversity Assessments at Qixingkeng Nature Reserve, Southwest Guangdong, 29 April to 1 May and 24 November to 1 December, 1998. South China Biodiversity Survey Report Series: No. 4. KFBG, Hong Kong SAR.

Kadoorie Farm and Botanic Garden. (2002). Report of a Rapid Biodiversity Assessment at Wutongshan National Forest Park, Shenzhen Special Economic Zone, China, 16 to 17 May 2001.

Karsen, S.J., Lau, M.W.-N. & Bogadek, A. 1998. Hong Kong Amphibians and Reptiles – 2^nd Edition. Provisional Urban Council, Hong Kong.

Romer, J.D. (1975). Annotated checklist with keys to the lizards of Hong Kong. Memoirs of the Hong Kong Natural History Society 1o: 1-13.

Zhao, E.M. & Adler, K. (1993). Herpetology of China. Society for the Study of Amphibians and Reptiles, Oxford (Ohio).

Zhao, E.M., Zhao, K.T. & Zhou, K.Y. (1999). Lacsertilia, Vol. 2 of Reptilia, Fauna Sinica. Science Press, Beijing.