Overview

Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range extends from south-central British Columbia to northwestern Baja California, from the Pacific coast to western Montana, Idaho, eastern Utah, and north-central Arizona, including various islands off the west coast of California and Baja California (Grismer 2002, Stebbins 2003). Elevational range is from sea level (California) to about 2,530 meters (8,300 feet) (southern Utah, southern Nevada, northern Arizona) (Tanner 1988, Stebbins 2003).

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Range Description

The range of this species extends from south-central British Columbia in Canada, through the western United States to northwestern Baja California in Mexico. In the United States it ranges from the Pacific coast to western Montana, Idaho, eastern Utah, and north-central Arizona, including various islands off the west coast of California and Baja California (Grismer 2002, Stebbins 2003). In Mexico, its range extends possibly as far south as el Rosario. Its elevational range is from sea level (California) to about 2,530 m (8,300 feet) (southern Utah, southern Nevada, northern Arizona) (Tanner 1988, Stebbins 2003).
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Continent: Middle-America North-America
Distribution: Canada (S British Columbia) USA (Washington, Oregon, Idaho, California, Nevada, Montana, Utah), Mexico (N Baja California, Los Coronados Islands, Todos Santos Islands, Ensenada, San José, Rancho San José, Alcatraz, San Pedro Mártir Mountains, Arroyo Encantada, San Quintín)  
Type locality: Oregon. Restricted to “The Dalles” by SMITH & TAYLOR 1950.
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Physical Description

Size

Length: 24 cm

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Type Information

Holotype for Plestiodon skiltonianus
Catalog Number: USNM 3168
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: No Further Locality Data, California, United States, North America
  • Holotype: Hallowell. 1859. Reports of Explorations and Surveys......for a Railroad from the Mississippi River to the Pacific Ocean, vol. 10, part 4. 10.
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Lectotype; Syntype for Plestiodon skiltonianus
Catalog Number: USNM 3172
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: No Further Locality Data, California, United States, North America
  • Lectotype: Taylor, E. H. 1935. The Kansas University Science Bulletin. 23: 424.; Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6 (2): 69.; Syntype: Taylor, E. H. 1935. The Kansas University Science Bulletin. 23: 424.; Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6 (2): 69.
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Paralectotype for Plestiodon skiltonianus
Catalog Number: USNM 279373
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: No Further Locality Data, California, United States, North America
  • Paralectotype: Taylor, E. H. 1935. The Kansas University Science Bulletin. 23: 424.; Baird, S. F. & Girard, C. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6 (2): 69.
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Ecology

Habitat

Montana Valley and Foothill Grasslands Habitat

This taxon can be found in the Montana valley and foothill grasslands ecoregions, along with some other North American ecoregions. This ecoregion occupies high valleys and foothill regions in the central Rocky Mountains of Montana in the USA and Alberta, Canada. The ecoregion the uppermost flatland reaches of the Missouri River drainage involving part of the Yellowstone River basin, and extends into the Clark Fork-Bitterroot drainage of the Columbia River system. The ecoregion, consisting of three chief disjunctive units, also extends marginally into a small portion of northern Wyoming. Having moderate vertebrate species richness, 321 different vertebrate taxa have been recorded here.

The dominant vegetation type of this ecoregion consists chiefly of wheatgrass (Agropyron spp.) and fescue (Festuca spp.). Certain valleys, notably the upper Madison, Ruby, and Red Rock drainages of southwestern Montana, are distinguished by extensive sagebrush (Artemisia spp.) communities as well. This is a reflection of semi-arid conditions caused by pronounced rain shadow effects and high elevation. Thus, near the Continental Divide in southwestern Montana, the ecoregion closely resembles the nearby Snake/Columbia shrub steppe.

A number of mammalian species are found in the ecoregion, including: American Pika (Ochotona princeps), a herbivore preferring talus habitat; Bighorn Sheep (Ovis canadensis), Black-tailed Prairie Dog (Cynomys ludovicianus), who live in underground towns that may occupy vast areas; Brown Bear (Ursos arctos); Hoary Marmot (Marmota caligata), a species who selects treeless meadows and talus as habitat; and the Northern River Otter (Lontra canadensis), a species that can tolerate fresh or brackish water and builds its den in the disused burrows of other animals.

There are six distinct anuran species that can be found in the Montana valleys and foothills grasslands, including: Canadian Toad (Anaxyrus hemiophrys); Western Toad (Anaxyrus boreas); Northern Leopard Frog (Lithobates pipiens); Plains Spadefoot Toad (Spea bombifrons); Columbia Spotted Frog (Rana luteiventris), an anuran that typically breeds in shallow quiet ponds; and the Boreal Chorus Frog (Pseudacris maculata).

Exactly two amphibian taxa occurr in the ecoregion: Long-toed Salamander (Ambystoma macrodactylum), a species who prefers lentic waters and spends most of its life hidden under bark or soil; Tiger Salamander (Ambystoma tigrinum).

Reptilian species within the ecoregion are: Milk Snake (Lampropeltis triangulum), an adaptable taxon that can be found on rocky slopes, prairie and near streambeds; Painted Turtle (Chrysemys picta); Western Plains Garter Snake (Thamnophis radix), a taxon that can hibernate in the burrows of rodents or crayfish or even hibernate underwater; Yellow-bellied Racer (Coluber constrictor); Spiny Softshell Turtle (Apalone spinifera); Western Terrestrial Garter Snake (Thamnophis elegans); Rubber Boa (Charina bottae); Western Skink (Plestiodon skiltonianus); and the Western Rattlesnake (Crotalis viridis).

The ecoregion supports endemic and relict fisheries: Westslope Cutthroat Trout (Oncorhynchus clarki lewisi), Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri), and fluvial Arctic Grayling (Thymallus arcticus), a relict species from past glaciation.

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Palouse Grasslands Habitat

This taxon is found in the Palouse grasslands, among other North American ecoregions. The Palouse ecoregion extends over eastern Washington, northwestern Idaho and northeastern Oregon. Grasslands and savannas once covered extensive areas of the inter-mountain west, from southwest Canada into western Montana in the USA. Today, areas like the great Palouse prairie of eastern  are virtually eliminated as natural areas due to conversion to rangeland. The Palouse, formerly a vast expanse of native wheatgrasses (Agropyron spp), Idaho Fescue (Festuca idahoensis), and other grasses, has been mostly plowed and converted to wheat fields or is covered by Drooping Brome (Bromus tectorum) and other alien plant species.

the Palouse historically resembled the mixed-grass vegetation of the Central grasslands, except for the absence of short grasses. Such species as Bluebunch Wheatgrass (Elymus spicatus), Idaho Fescue (Festuca idahoensis) and Giant Wildrye (Elymus condensatus) and the associated species Lassen County Bluegrass (Poa limosa), Crested Hairgrass (Koeleria pyramidata), Bottlebrush Squirrel-tail (Sitanion hystrix), Needle-and-thread (Stipa comata) and Western Wheatgrass (Agropyron smithii) historically dominated the Palouse prairie grassland.

Representative mammals found in the Palouse grasslands include the Yellow-bellied Marmot (Marmota flaviventris), found burrowing in grasslands or beneath rocky scree; American Black Bear (Ursus americanus); American Pika (Ochotona princeps); Coast Mole (Scapanus orarius), who consumes chiefly earthworms and insects; Golden-mantled Ground Squirrel (Spermophilus lateralis); Gray Wolf (Canis lupus); Great Basin Pocket Mouse (Perognathus parvus); Northern River Otter (Lontra canadensis); the Near Threatened Washington Ground Squirrel (Spermophilus washingtoni), a taxon who prefers habitat with dense grass cover and deep soils; and the Northern Flying Squirrel (Glaucomys sabrinus), a mammal that can be either arboreal or fossorial.

There are not a large number of amphibians in this ecoregion. The species present are the Great Basin Spadefoot Toad (Spea intermontana), a fossorial toad that sometimes filches the burrows of small mammals; Long-toed Salamander (Ambystoma macrodactylum); Northern Leopard Frog (Glaucomys sabrinus), typically found near permanent water bodies or marsh; Columbia Spotted Frog (Rana luteiventris), usually found near permanent lotic water; Pacific Treefrog (Pseudacris regilla), who deposits eggs on submerged plant stems or the bottom of water bodies; Tiger Salamander (Ambystoma tigrinum), fossorial species found in burrows or under rocks; Woodhouse's Toad (Anaxyrus woodhousii), found in arid grasslands with deep friable soils; Western Toad (Anaxyrus boreas), who uses woody debris or submerged vegetation to protect its egg-masses.

There are a limited number of reptiles found in the Palouse grasslands, namely only: the Northern Alligator Lizard (Elgaria coerulea), often found in screes, rock outcrops as well as riparian vicinity; the Painted Turtle (Chrysemys picta), who prefers lentic freshwater habitat with a thick mud layer; Yellow-bellied Racer (Chrysemys picta); Ringneck Snake (Diadophis punctatus), often found under loose stones in this ecoregion; Pygmy Short-horned Lizard (Phrynosoma douglasii), a fossorial taxon often found in bunchgrass habitats; Side-blotched Lizard (Uta stansburiana), frequently found in sandy washes with scattered rocks; Southern Alligator Lizard (Elgaria multicarinata), an essentially terrestrial species that prefers riparian areas and other moist habitats; Pacific Pond Turtle (Emys marmorata), a species that usually overwinters in upland habitat; Western Rattlesnake (Crotalus viridis), who, when inactive, may hide under rocks or in animal burrows; Night Snake (Hypsiglena torquata); Western Skink (Plestiodon skiltonianus), who prefers grasslands with rocky areas; Western Terrestrial Garter Snake (Thamnophis elegans), found in rocky grasslands, especially near water; Rubber Boa (Charina bottae).

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Comments: Habitats include grassland, chaparral, pinyon-juniper woodland, open pine or pine-oak woods, and rocky areas near streams (Stebbins 2003); the species is partial to open wooded foothills and is usually associated with rocks, under which it takes shelter (also digs burrows in soil). Eggs are laid in burrows or areas excavated by the female under rocks and stones.

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Habitat and Ecology

Habitat and Ecology
Habitats include grassland, chaparral, pinyon-juniper woodland, open pine or pine-oak woods, and rocky areas near streams (Stebbins 2003); the species is partial to open wooded foothills and is usually associated with rocks, under which it takes shelter. It also digs burrows in soil. Eggs are laid in burrows or areas excavated by the female under rocks and stones.

Systems
  • Terrestrial
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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: Feeds on a wide variety of insects (crickets, beetles, grasshoppers, flies, etc), spiders and earthworms.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 - 300

Comments: This species is represented by a arge number of occurrences or subpopulations. For example, Tanner (1988) mapped nearly 200 collection sites rangewide. Nussbaum et al. (1983) mapped even more localities than did Tanner for the Pacific Northwest portion of the range. The secretive habits of this skink suggest that it occurs in many more localities than have been so far documented.

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Global Abundance

10,000 - 1,000,000 individuals

Comments: Total adult population size is unknown but surely exceeds 10,000 and probably exceeds 100,000. The species is locally common in many areas. Like most skinks, it is secretive and much more numerous than visual observations would suggest.

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General Ecology

Secretive. Life history not well known.

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Life History and Behavior

Cyclicity

Comments: Inactive in cold winter weather; duration of inactive period varies with local climate.

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Reproduction

In Utah, mates in May or June, lays eggs in July, eggs hatch in August. Clutch size 2-6 (Nussbaum et al. 1983). Female guards eggs and stays with hatchlings until they disperse from nest.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Plestiodon skiltonianus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 6
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N1 - Critically Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: T5 - Secure

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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Intrinsic Vulnerability: Moderately vulnerable

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Hammerson, G.A. & Hollingsworth, B.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, tolerance of a broad range of habitats, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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Global Short Term Trend: Relatively stable (=10% change)

Comments: Trends are undocumented, but extent of occurrence, area of occupancy, number of subpopulations, and population size are large and probably relatively stable.

Global Long Term Trend: Increase of 10-25% to decline of 30%

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Population

Population
This species is represented by a large number of occurrences or subpopulations. For example, Tanner (1988) mapped nearly 200 collection sites rangewide. Nussbaum et al. (1983) mapped even more localities than did Tanner for the Pacific Northwest portion of the range. The secretive habits of this skink suggest that it occurs in many more localities than have been so far documented. The total adult population size is unknown but surely exceeds 100,000 and is probably in the millions. The species is locally common in many areas. Like most skinks, it is secretive and much more numerous than visual observations would suggest. Population trends are undocumented, but its extent of occurrence, area of occupancy, number of subpopulations, and population size are large and probably relatively stable.

Population Trend
Stable
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Threats

Degree of Threat: Low

Comments: No major threats have been identified. Reductions from habitat loss appear to be minimal.

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Major Threats
No major threats have been identified. Reductions from habitat loss appear to be minimal.
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Management

Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: This lizard occurs in many national parks and other protected areas.

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Conservation Actions

Conservation Actions
This lizard occurs in many national parks and other protected areas. No direct conservation measures are currently needed for this species as a whole.
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Wikipedia

Western Skink

The western skink (Plestiodon skiltonianus) is a species of small, smooth-scaled lizard with relatively small limbs. It measures about 100 to 210 mm (about 4 to 8.25 inches) in total length (body + tail). It is one of five species of lizards in Canada. Western skinks are very adaptable. They spend much of their day basking in the sun. Their diet ranges widely, including spiders and beetles. Western skinks will bite if grasped and will flee if they feel threatened. It is a common but secretive species whose range extends throughout Washington, Oregon, Nevada, Utah, and Wyoming and into western Montana and northern Arizona.[3] It is widespread in northern California but restricted to the coast in central and southern California. Found in a variety of habitats, this lizard is most common in early successional stages or open areas of late successional stages. Heavy brush and densely forested areas are generally avoided.[4] Western skinks are found from sea level to at least 2,130 m (7,000 ft).[5] This diurnal reptile is active during the warm seasons.[4]

Taxonomy[edit]

Tetrapoda: Amniota: Reptilia: Squamata: Scincidae

Baird and Girard described Skilton's skink in 1852 and named it in honor of Dr. Avery J. Skilton, who had sent them specimens. Tanner (1957) identified the subspecies interparietalis and utahensis.

Coronado skink
(Plestiodon skiltonianus interparietalis)

There are three recognized subspecies, including the nominotypical subspecies:[2]

  • Great Basin skink, P.s. utahensis (W. Tanner, 1957)
    Occurs in Utah.
  • Skilton's skink, P.s. skiltonianus Baird & Girard, 1852

The most common is Skilton's skink, which occurs throughout the western United States west of the Rocky Mountains and in southern British Columbia, Canada.

Together with Gilbert's skink (P. gilberti), the San Lucan skink (P. lagunensis), and the four-lined Asiatic skink (P. quadrilineatus), the western skink belongs to the so-called "skiltonianus group". The exact taxonomy within this group is being questioned and may need revision following DNA analysis research.

Behavior[edit]

The western skink is a secretive and very agile lizard that forages actively through leaf litter and dense vegetation, preying upon small invertebrates including spiders,a variety of insects and sow bugs.[3] Crickets, beetles, moths, grasshoppers, and other arthropods have been found in the stomachs of skinks.[6] Prey is sometimes stalked and cannibalism has been reported.[7] It is a good burrower and sometimes constructs burrows several times its own body length.

Habitat[edit]

Found in a variety of habitats from sea level to at least 2,130 m (7,000 ft), the western skink is commonest in early successional stages or open areas within habitats in which it occurs. Heavy brush and densely forested areas are generally avoided. The western skink seems to prefer a somewhat moist environment, although it can also be found on dry hillsides. Frequents grassland, broken chaparral, pinon-juniper and juniper-sage woodland, and open pine-oak and pine forests.[8] The soil of its nest chambers is invariably moist. Standing water is apparently not required.

Juvenile western skink
Juvenile western skink

Description[edit]

Aside from fading with age, color pattern of adults varies little. Broad brown stripe down back, edged with black and bordered on each side by conspicuous whitish to beige dorsolateral stripe that begins on nose and extends over eye and back alongside body onto tail. Pale dorsolateral stripes on joined halves of 2nd and 3rd scale rows. A second pale stripe, starting on upper jaw, occurs low on each side and is separated from the first by a broad dark brown or black band originating on side of head and usually extending well out onto tail. Tail dull blue (in juveniles) or gray. In the breeding season reddish or orange color appears on side of head and chin and occasionally on sides, tip, and underside of tail. Usually 7 upper labials and 4 enlarged nuchals. Young exhibit a striped pattern more vivid than in adult and tail bright blue. Dark lateral stripe usually extends well out on side of tail.[8]

Geographic range[edit]

Western skinks can be found from southern British Columbia, Canada, to the tip of Baja California, and throughout most of Great Basin to extreme Northern Arizona; central Utah to the Pacific Coast. The species is apparently absent from the floor of San Joaquin Valley, central Sierra Nevada (except a few scattered locations in the foothills were they are very common), and lowland deserts of California. In Northern Baja, California the species occurs in the northwestern part at least as far south as Colonia Guerro and in the south in the cape and Comondu regions, Santa Agueda, and San Francisco de la Sierra. On Santa Catalina, Los Coronados, and Todos Santos Island off the coast of California.[8]

Defensive behavior[edit]

Young western skinks have a bright blue tail with color that fades with age. If seized by a predator its tail is deliberately cast and wriggles violently attracting attention while the lizard may escape.[8] The tail will grow back with time but is often darker in color and misshapen. It will play dead, but this behavior is rarely seen.

Life History[edit]

This skink is diurnal during the period of warm-season activity. During summer most activity is concentrated in the morning and late afternoon. Where summer temperatures are not extreme, activity extends throughout the day. Adult skinks usually become inactive by early fall but juveniles extend their period of activity several weeks.

The reproductive season for this species varies geographically and from year to year depending on local conditions. Mating probably occurs in the spring soon after emergence. Males turn orange on the underside when they are breeding. Females lay 2-6 eggs during June and July. Western skink females construct nest chambers that are several centimeters deep in loose moist soil. Typically these chambers are located under surface objects, especially flat stones, logs, and sometimes in or near rock outcrops.[4]

Young western skinks probably hatch in late summer, and sexual maturity may occur at 2 years of age, but most individuals probably do not reproduce until they are 3 years old. Western skinks can reach an age of up to 10 years.

References[edit]

  1. ^ Hammerson, G.A. & Hollingsworth, B (2007). "plestiodon skiltonianus". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature. Retrieved May 10, 2014. 
  2. ^ a b The Reptile Database. www.reptile-database.org.
  3. ^ a b Stebbins, R.C. 1985. A Field Guide to Western Reptiles and Amphibians, Second Edition, Revised. Houghton Mifflin. Boston, Massachusetts. 336 pp.
  4. ^ a b c Tanner, W.W. 1957. A Taxonomic and Ecological Study of the Western Skink (Eumeces skiltonianus). Great Basin Naturalist 17 (3-4): 59-94.
  5. ^ Zeiner, D.C.; W.F. Laudenslayer, Jr.; K.E. Mayer; and M. White; eds. 1988. California's Wildlife. Vol. 1. Amphibians and Reptiles. Calififornia Dept. of Fish and Game. Sacramento, California. 272 pp.
  6. ^ Taylor, E.H. 1936. A Taxonomic Study of the Cosmopolitan Scincoid Lizards of the Genus Eumeces with an Account of the Distribution and Relationship of its Species. Univ. Kansas Sci. Bull. 23: 1-643.
  7. ^ Zweifel, R.G. 1952. Notes on the lizards of the Coronados Islands, Baja California, Mexico. Herpetologica 8: 9-11.
  8. ^ a b c d Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians, Third Edition. Peterson Field Guide Series ®. Houghton Mifflin Company. Boston and New York. xii + 533 pp. ISBN 0-395-98272-3. (Eumeces skiltonianus, pp. 312-314 + Plate36 + Map 110.)

Further reading[edit]

  • Baird, S.F., and C.F. Girard. 1852. Characteristics of some New Reptiles in the Museum of the Smithsonian Institution. Proc. Acad. Nat. Sci. Philadelphia 6: 68-70. (Plestiodon skiltonianum, p. 69.)
  • Boulenger, G.A. 1887. Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume III. Lacertidæ, Gerrhosauridæ, Scincidæ,... Trustees of the British Museum (Natural History). (Taylor and Francis, printers.) London. xii + 575 pp. + Plates I.- XL. (Eumeces skiltonianus, p. 373.)
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Names and Taxonomy

Taxonomy

Comments: In a phylogenetic analysis of Eumeces based on morphology, Griffith et al. (2000) proposed splitting Eumeces into multiple genera, based on the apparent paraphyly of Eumeces. Smith (2005) and Brandley et al. (2005) formally proposed that all North American species (north of Mexico) be placed in the genus Plestiodon. This was accepted by Crother (2008) and Collins and Taggart (2009).

Recent phylogenetic analyses using DNA data indicate that the E. gilberti morphotype (generally large-bodied and uniformly colored, versus the small-bodied and striped E. skiltonianus morphotype) has arisen independently at least three times (three clades) and that two of the three clades are nested within the geographically more widespread E. skiltonianus (Richmond and Reeder 2002). Eumces lagunensis of southern Baja California is also nested phylogenetically within E. skiltonianus (Richmond and Reeder 2002). Subspecies of E. skiltonianus as currently circumscribed do not correspond with the boundaries of haplotype clades based on mtDNA (Richmond and Reeder 2002). A taxonomic revision is warranted, but further study is needed before the species limits within this group can be definitively determined (Richmond and Reeder 2002). Stebbins (2003) treated E. lagunensis of southern Baja California as a subspecies of E. skiltonianus whereas Grismer (2002) recognized E. lagunensis as a distinct species.

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