Biology Forum Evolution Subspecies comparison of the Genus: Corucia

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      Brian – LCRC


      Courtesy of POLYPHEMOS (2006)

      Subspecies comparision of the Genus: Corucia

      Brian L. Schnirel and Sherri L. Jones
      Leeway Corucia Research Center (LCRC)
      Blenheim, S.C. 29516 U.S.A.



      Detailed measurements and observations differentiating the two
      subspecies of Corucia zebrata (underlined), Corucia zebrata zebrata(underlined) and Corucia zebrata alfredschmidti (underlined), are described including new material not previously documented.

      Key words: Corucia, Sclera, Parietal, Prefrontal, Rostral, Nasal


      Corucia zebrata zebrata (underlined) described and named (Gray, 1855) and Corucia zebrata alfredschmidti (underlined) described and named (Kohler, 1997) represent the two subspecies of Corucia zebrata (underlined) – the prehensile tailed monkey skink.

      The common monkey skink (Corucia zebrata zebrata) hails from the larger islands of the Solomon archipelago southeast of Buka and Bougainville. This includes Choiseul, Guadalcanal, Isabel, Malaita, Nggla, New Georgia, Santa Ana, San Cristobal, Shortlands, and Ugi (Balsai,1995). The North Solomon monkey skink (Corucia zebrata alfredschmidti) hails from the North Solomons which are comprised of Bougainville and Buka (Kohler,1997).

      Bougainville is by far the largest island in the archipelago and being on the northeast fringe of these islands, supported the establishment of peripheral isolates evolving into the subspecies alfredschmidti. This is supported by the sheer number and larger distribution of the subspecies
      zebrata in the southeastern islands. The core population of Corucia zebrata zebrata (underlined) appears to be from Quadalcanal (Balsai, 1995). The allopatric subspeciation of the Genus: Corucia reveals
      a larger size of Corucia zebrata alfredschmidti compared to Corucia zebrata zebrata. Indeed, a semi-Wallace line appears to exist between Bougainville and Choiseul. "There is an affinity along the lines of Bougainville – Choiseul, separated by the Bougainville strait, in which the
      faunal differences are relatively distinct (faunal differences 86%)" (Green/Slade,1968). Other animals show a size differential with the populations on Bougainville being generally larger than that on Choiseul. The monkey faced flying fox (Pteralopex anceps) on Bougainville is also
      larger (255-280 mm). On Choiseul, next to Bougainville, the population is smaller (160-275mm) (E. Bowen-Jones 1997).

      The differences between Corucia zebrata zebrata and Corucia zebrata alfredschmidti are described here in detail which should aid in better appreciating the comparative differences between the two subspecies. As such, identification will achieve a faster result. However, once one has seen both Corucia zebrata zebrata and Corucia zebrata alfredschmidti, the visual difference in size and body coloration alone is readily apparent, even from a distance.

      Snout/Vent Length (SVL) & Length Overall (LOA)

      common monkey skink
      Corucia zebrata zebrata (underlined)


      Average: Males = 250 mm

      Females = 270 mm

      Range: Males = 230 – 270 mm

      Females = 260 – 280 mm


      Average: Males = 550 mm

      Females = 582.5 mm

      Range: Males: = 520 – 580 mm

      Females: = 560 – 605 mm

      North Solomon monkey skink
      Corucia zebrata alfredschmidti (underlined)


      Average: Males: = 320 mm

      Females: = 330 mm

      Range: Males: = 290 – 340 mm

      Females: = 270 – 330 mm


      Average: Males: = 660 mm

      Females: = 670 mm

      Range: Males: = 630 – 680 mm

      Females: = 640 – 690 mm

      Number of individuals of equal proportions used in study: 96.

      A noticable difference in size of neonates is also in evidence: (LOA)

      Corucia zebrata zebrata (underlined) averages about 11 1/2" (Langerwerf, 2006, Schnirel, 2001)

      Corucia zebrata alfredschmidti (underlined) averages just under 15" (Schnirel, 2004)

      Czz / Cza neonate comparison:

      Corucia zebrata zebrata LOA = 289 mm

      Corucia zebrata alfredschmidti LOA = 370 mm

      Note: Both subspecies of Corucia zebrata (underlined) reproduce by viviparous matrotrophy with the birth of a single very large neonate. Occasionally, twins are produced, there is one documented case of triplets (Langerwerf, 2003).

      Weight (Average)

      Adult Neonate

      Common monkey skink = 500 Grams 81 Grams
      Corucia zebrata zebrata

      North Solomon monkey skink = 845 Grams 173 Grams
      Corucia zebrata alfredschmidti

      Number of adult Corucia used in study : 96. , Number of neonate Corucia used in study : 39.

      common monkey skink

      Corucia zebrata zebrata (underlined)



      Smaller size than Northern Solomon monkey skink
      (Corucia zebrata alfredschmidti (underlined)).
      Average adult: LOA = 572mm (22"), SVL = 262mm


      Scalation: The original description by Kohler indicates that common
      monkey skinks possess five parietal scales. The
      arrangement has, from left to right-head facing
      observer, parietal scale one and two larger and less
      cramped in width than comparable parietal scales in the
      North Solomon monkey skink (width/length ratio-
      parietal scale one = 9/13, parietal
      scale two = 18/27). Parietal scales encompass nearly
      the entire left side of the region (front facing away from
      observer) of the upper head. Parietal
      scale three is positioned centrally comparable in position
      to parietal scale four in the Northern Solomon
      subspecies. It is larger (length ratio Czz/Cza = 9/7,
      Width ratio Czz/Cza = 7/5). Parietal scale three is
      triangular with the tapered point directed towards the
      rear of the head (width/length ratio
      = 7/24). Parietal scale four is right of center. It is
      more round in shape (length ratio Czz/Cza = 5/8, width
      ratio Czz/Cza = 7/9, width/length ratio = 7/8).
      Parietal scale five is on the right edge of the head and
      positioned more to the rear than the other four parietals
      (width/length ratio = 13/30). Unlike the Northern
      Solomon subspecies, the common Solomon monkey
      skink has no number six and seven parietal scales.
      The parietal description is a guide however, and
      should not be taken as absolute except for the total
      number. In practice, the head scales are as varied
      as fingerprints in size and shape. The prefrontals of
      Corucia vary in size and number. Common
      monkey skinks possess two to three.

      Scalation: Dorsal and ventral scales are in a different ratio.
      Common monkey skinks are more elongated with a
      length/width dorsal scale ratio of 4/9.
      Northern Solomon skinks have a length/width dorsal
      scale ratio of 6/9. Length/width ventral scale ratio for
      the common subspecies is 3/7. The
      Northern Solomon subspecies length/width ratio = 1/2.


      Sclera: A consistent distinquishing feature separating the two
      Corucia subspecies is scleral color. Corucia zebrata
      zebrata (underlined) has a white sclera. Corucia
      zebrata alfredschmidti (underlined) has a black sclera.

      Iris: The iris color can vary from dark green, green,
      greenish yellow, orange, and jet-black. A green
      background iris can be stippled with brown or black
      pigment. The green or yellow-green pigmented iris
      could be autosomal dominant as is with a brown-black
      pigmented iris in humans. This
      means only one copy of this gene from a parent is
      needed in order for a green-yellow pigment to be
      manifested in the individual. For a total
      black pigmented iris in a Corucia (which is the least
      seen); this would signify the black pigmented gene
      would have to be contributed by both
      parents to achieve this color phase. Unlike the
      Northern Solomon subspecies, there is no
      establishment of iris color linked to specific islands
      or cooresponding phenotypes with the common


      Description: The classic holotype description by John Edward Gray
      describes Corucia zebrata zebrata (underlined) as
      having prominent banding. The bands
      are alternating dark brown-black/ green. The green
      portion can be of various shades. The mid body
      bands are vertical to a twenty degree forward slope
      as compared to Corucia zebrata alfredschmidti
      (underlined) with a fifty degree
      forward slope. Gray also described a play of colors
      effect from the body scales, hence the origin of the
      scientific name. The Genus name Corucia derives
      from the latin coruscus – definition: shimmering.
      zebrata is a latinized form of the word zebra;
      pertaining to the zebra-like banding. Black
      spots are varied throughout the body. The green in
      the body is often blended with brown. The locus
      typicus of gray’s work with
      Corucia was on San Cristobal.

      Phenotypes: Unfortunately, not enough research has been done
      on wild populations on specific islands with Corucia
      zebrata zebrata (underlined).
      Certain phenotypes may correspond to separate
      islands. The Leeway Corucia
      Research Center has found that different phenotypes
      within Corucia zebrata zebrata (underlined) will
      breed with complete success. In other words, there
      appears to be no genetic drift towards speciation to
      the point of non-viability
      of the embryo. All phenotypes can have black spot
      pigmentation throughout the body
      in various sizes, numbers, and patterns. The spots
      may overlap. Dark green
      body coloration may occur with little or no black
      pigmentation. This may coincide with the report of
      the darkest individuals coming from Malaita (McCoy, 1980). There are individuals having
      incomplete banding. The incomplete banding
      consists of blotches. The blotches are green to
      greenish aqua. Some will have no banding or
      blotches period. One phenotype from this category
      is an army green color often with
      little or no black spots. Often, as previously
      indicated, the body is flushed with patches of light
      brown at various parts of the body but
      in addition, there can be brick red around the head.
      Yellow is generally less
      prominent in Corucia zebrata zebrata (underlined)
      than with Corucia zebrata alfredschmidti
      (underlined. Some yellow can be seen usually in the
      throat or spotted only on parts of the head compared
      to cases of almost full yellow on
      the head of the North Solomon subspecies. In one
      documented case, a highly pigmented (light and dark
      spots) female (LCRC/Czz/34) exhibits yellow
      spots on the tail. To date, this is the only Corucia
      seen with this color pigmentation in the tail region.
      Some common monkey skinks have
      white on the head and throat (i.e.LCRC/Czz/36).
      The nasal and rostral scales of all types are
      generally darker in color in Corucia zebrata zebrata
      than with Corucia zebrata alfredschmidti. North
      Solomon monkey skinks have a distinctive yellowish-
      cream color to the nasal and rostral scales which
      appears striking in contrast to the generally turquoise

      North Solomon monkey skink

      Corucia zebrata alfredschmidti (underlined)



      Size: Larger size than the common monkey skink (Corucia
      zebrata zebrata).

      Average LOA = 690mm (27"), SVL = 335mm (13").

      Scalation: As based on Kohler, North Solomon monkey skinks
      possess seven parietal scales. The arrangement has,
      from left to right-head facing observer, parietal scale
      one and two smaller and more cramped in width
      than comparable parietal scales in the common
      monkey skink (width/length ratio: parietal scale one = 4/6, parietal scale two = 13/25). Parietal scale

      three is smaller in length and width (width/length ratio = 13/16) than

      comparable scale in Corucia zebrata zebrata (pointed towards the rear of

      the skull). Parietal scale four is centralized and elongated with a bottleneck

      appearance near vertical center (narrowest point width/length ratio = 2/19,

      total width variation ratio = 4/17,). However, the original description of the

      holotype and paratypes has no mention of parietal scale four ever pinched-

      off completely rather than bottlenecked. The illustration in Salamandrae gives

      the impression that the bottleneck configuration is standard. Head scales

      actually vary in size and shape as much as the black pigment spots on the

      body. In common observation, most specimens of Corucia zebrata

      alfredschmidti have the pinced-off version. Parietal scale five is just right of

      center rather than at the dextral edge as in the common monkey skink

      (width/length ratio = 13/17). Parietal scale five is also more symmetrical in

      shape and squarer than parietal scale five in the common monkey skink.

      Parietal scale six (not found in Corucia zebrata zebrata) is comparable in size

      and shape to parietal scale three (width/length ratio = 12/17). Parietel scale

      seven (not found in Corucia zebrata zebrata) is elongated and more pointed

      to the front of the skull (width/length ratio = 7/12). Parietal scale seven is at

      the dextral edge of the head. Prefrontal scalation varies from two to four

      compared to two-three in the common monkey skink.

      In summation, head scales are not the best indicator of Corucia

      subspecies classification. It takes a trained eye and much close up viewing to

      get an accurate determination. The unwavering criteria to utilize is that

      Corucia zebrata alfredschmidti has 2 more parietals (six and seven) than with

      Corucia zebrata zebrata.

      Scalation: North Solomon monkey skinks have been described as
      having larger ventral and dorsal scales than the common
      monkey skink (Kohler,1997). The scales are larger in
      general due to the larger ultimate size of this

      subspecies of Corucia. However, in a ratio comparison of width/length,

      there is a difference as noted in the common monkey skink section.

      LCRC research data shows that in a width/length ratio of dorsal scales,

      North Solomon monkey skinks have a ratio of 6/9. Common monkey

      skinks have a ratio of 4/9. The ventral width/length ratio is 1/2 for the

      Northern Solomon monkey skink and 3/7 for the common monkey skink.

      Sclera: As noted earlier, Corucia zebrata alfredschmidti
      (underlined) has a black sclera and Corucia zebrata
      zebrata (underlined) has a white sclera. This is

      Iris: The iris color of Corucia zebrata alfredschmidti
      does not seem to vary as much as in Corucia
      zebrata zebrata. The color is almost always a
      green-yellow mix – at least in Corucia zebrata
      alfredschmidti from Bougainville.
      However, Corucia zebrata alfredschmidti from Buka
      appear to have a more intense green iris.
      Besides the striking head color and larger ultimate
      size, the eyes of Corucia zebrata alfredschmidti
      (underlined)are another very prominent and
      stunning attribute of this subspecies. The yellow-
      green iris coloration surrounded by the black sclera
      makes this so.

      Coloration: The top of the head in the North Solomon Monkey skink
      is a striking

      turquoise often suffused with yellow. This concurs with the holotype

      description by Kohler. Most of the yellow is prominent in the throat and

      chin region but may occur on top of the head as well in several areas including

      the region around the ear openings. There has not been observed in Corucia zebrata alfredschmidti, a yellow spotted individual in the tail region like the

      LCRC / Czz /34 specimen. From imports of highly questionable legal

      passage but traced and personally seen, it appears that North Solomon

      Corucia that hail from Buka differ from the main pennisula contingent in that

      the Buka contingent of Corucia shows a light brownish component overlaying

      the bright turquoise on the head. In addition, as mentioned, the iris is an

      intense green. Otherwise, all other aspects of Buka Corucia zebrata

      alfredschmidti are germane to that of Bougainville Corucia zebrata alfredschmidti. It would appear, that the Buka Corucia are a polytypic

      variant but would not constitute a separate subspecies classification.

      As with the common monkey skink, North Solomon monkey skinks

      are found with and without banding. The banded individuals have central

      bands that slope at a 50 degree angle. Common monkey skinks have a

      0 – 20 degree angle to the transverse torso of the body. This has also been

      noted by Burt Langerwerf of Agama International. The bands on the

      North Solomon monkey skinks are a consistent light brown whereas

      common monkey skinks are darker brown to black. The lighter brown

      banding in contrast to the aqua bands gives a more faded appearance to the

      North Solomon subspecies compared to the common subspecies. Blotched

      North Solomon individuals are occasionally encountered. Both banded and

      unbanded North Solomon monkey skinks may have black spots. Northern

      Solomon monkey skinks have the light brown tone mentioned in the bands

      often intermixed with the aqua of the body. Common monkey skinks often

      have a brown wash with the green/aqua color of the body but the brown is

      usually darker. All North Solomon monkey skinks have a distinctive

      yellowish-cream color to the nasal and rostral scales in contrast to a darker

      color in common monkey skinks as noted in the common monkey skink section.

      The cream color of these scales also shows a significant contrast to the turquoise

      color of the head of the North Solomon subspecies.

      Kohler lists the holotype of Corucia zebrata alfredschmidti as holotypes SMF 77587 with locus typicus being the island of Bougainville (Mekamuri or North Solomons). The Holotype resides in the Senckenberg Museum, Frankfort Germany (Museum Franfort Senckenberg an lage 25 60325 Frankfort am main D.

      Germany tel +49 06917542-0 fax ++90691746238). The holotype is described as being an adult Male.

      The Paratype of Corucia zebrata alfredschmidti is listed as MTKD – 39481. The paratype resides in the Staatiches Museum Fur tierkunole Augustus strasse 2 Dresden Germany. The Paratype is described as being unknown in gender.

      The Leeway Corucia Research Center (LCRC) Studbook classification system is as follows:

      LCRC / Czz / 34

      LCRC = Corucia Research Center of individual

      Czz = Subspecies classification Czz = Corucia zebrata zebrata

      Cza = Corucia zebrata alfredschmidti

      34 = Individual number at research center


      Although Genetic drift of the peripheral isolates of the
      Corucia population resulted in the subspeciation of Corucia zebrata alfredschmidti (underlined), the ecological niche in this subspecies remained constant. This is based on a pattern in the Scincidae where the more arboreal the species, the proportionally longer the digits. A smooth, non-varying, numerical progression can be seen from species of various niches based on anterior foot length (the junction of the ulna / radius carpal bones to longest digit) divided by the snout to vent length (SVL)(Schnirel, 2004). In the case of Corucia, both subspecies occupy a high canopy arboreal niche with the same numerical value.

      Although no viable cross subspeciation has been documented resulting in ‘whatticles’ (Jones, 1984), being subspecies, it is theoretically possible to cross North Solomon Corucia with common Corucia. Balsai (1995) has theorized that common Corucia from various islands have been genetically apart enough based on miscarriages that have occurred in captivity. However, many breeding centers have had great success rates in breeding of this species of different phenotypes. The South Florida Corucia Research Center had a 100% success rate of over thirty births. Agama International also shows a positive record. Other factors may be the reasons for the miscarriages resulting in slugs (miscarriages) or stillbirths other than genetic incompatibility that need to be explored. For instance, improper environmental conditions (humidity, temperature, diet, etc.), stress, disease, exposure to toxins, the possibility of too much genetic closeness if the mated pair came from the same island canopy and were closely related, etc. Other than Corucia zebrata zebrata (underlined) and Corucia zebrata alfredschmidti (underlined, there appear no other candidates for subspecies classification. As such, genetic incompatibilty between the common subspecies of Corucia is a topic that requires further research. Although common Solomon monkey skinks may not exhibit miscarrages due to genetic drift, it would be logical to conclude that between subspecies (Corucia zebrata zebrata (underlined) and Corucia zebrata alfredschmidti(underlined)), they could be enough apart that breeding between the two
      would result in genetic misfires to some degree. This, of course, would be
      based on the time honored rule of distinct speciation depending on a species being unable to produce a viable species with another. Whether or not the two subspecies straddle the fence of genetic compatibilty is also a future topic of research.

      To distinquish Corucia subspecies in summation, if one cannot see the
      two subspecies in comparison or a photograph, look for the following. In
      Corucia zebrata alfredschmidti(underlined), two extra parietal scales, or
      up to two extra pre-frontal scales, a black sclera, bright turquoise head (in most cases), and in banded individuals, a 50 degree slope in banding. In a visual comparison, look for a reduced ratio in dorsal and ventral
      scale ratios of width/length of Corucia zebrata alfredschmidti (underlined) compared to Corucia zebrata zebrata (underlined). A larger size of approximately 17%, a lighter brownish coloration – especially a faded
      appearance in the banded individual, and a noticeable contrast between body coloration and nasal and rostral scales – with the scales having a distinctive yellow cream coloration.


      The color, banding, blotches and spots mentioned are adaxial in general for both subspecies. The abaxial area (lower chest and belly region to vent) is void of bands and spots. It is generally a solid green or aqua.


      Balsai, Michael J.; 1995. Husbandry and breeding of the Solomon
      islands prehensile-
      tailed skink (Corucia zebrata). The Vivarium,
      California, U.S.A. pp. 4-11.

      Bowens, E.; Jones; 1997. Flying foxes on Choiseul (Solomon islands) –
      the need for
      conservation. Oryx, Volume 31, July, Cambridge, U.K.
      page 309.

      Coburn, John; 1996. Prehensile tailed skinks. T.F.H. Publications
      Inc. Neptune
      City, New Jersey, U.S.A. 64 pages.

      De Vosjoli, Phillippe
      1993. The general care and maintainence of
      prehensile tailed skinks.
      Advanced Vivarium Systems Inc.,
      Lakeside, Cailfornia, U.S.A.
      57 pages.

      Kohler, G.; 1997. Eine neue unterart des wickelshwanz
      skinkes Corucia zebrata
      von Bougainville, Papua Neuguinea –
      Salamandrae, Germany
      Volume 33, Issue 1, pp. 61-65.

      Green, Slade; 1968. Island patterns in the Solomon islands bird
      fauna. Evolution,
      Volume 11-Number 4, December, London,
      U.K. pp. 751-761.

      Langerwerf, Burt; 2003. Agama International; Personal

      McCoy, Michael; 1980. Reptiles of the Solomon islands. Wau
      Ecology Institute,
      Handbook No. 7:30. Papua New Guinea.

      Parker, F.; 1983. The prehensile tailed skink (Corucia
      zebrata) on Bougainville
      island, Papua New Guinea. Advances in
      herpetology and
      evolutionary biology, Museum of
      Comparative Zoology,
      Cambridge, Massachusetts, U.S.A. pp. 435-

      Schnirel, Brian L. 2004. Seni biometric analysis on the extinct
      Scincidae species:
      Macroscincus coctei. Underlined)
      Polyphemos, Volume 2, Issue 1,
      May, Florence, South Carolina, U.S.A. pp.

      Last edited by Brian – LCRC on Thu Aug 03, 2006 6:31 am; edited 4 times in total [/b]

    • #87932

      Bert Langerwerf and I both wrote articles for a special Corucia edition of the Southwestern Herpetologists Society publication "Herpetology" earlier this year. Before the papers went to publication, Bert and I corresponded a bit about C.z. alfredschmidti, because I thought he had some erroneous information on his website (which states that alfredschmidti are *smaller* than zebrata, and have yellow irises).

      I did some research, and got hold of a copy of Köhler’s original 1997 paper (in German) describing the alfredschmidti subspecies. In that paper, he does indeed describe Corucia zebrata alfredschmidti as *smaller* than C. z. zebrata (maximum body length, not including tail, of 310 mm vs. 340 mm for zebrata), and as having bright yellow irises. They also have more parietal scales than zebrata (>7 vs. 5-6 for zebrata).

      So the type you have been calling alfredschmidti (which are significantly *larger* than zebrata, and have black sclera) are NOT alfredschmidti as described by Köhler (1997). It is possible that this larger type is a third distinct subspecies. But I don’t know how to tell that. :-/

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