Wednesday, February 22, 2012

Lab 5: Lepidosauria Part 1: Sphenodontida and Sauria (Kelly and Maggie)

Sauria, lizards, are found within the clade Lepidosauromorpha. There are several synapomorphies which unite Lepidosauria: 
1. Transverse cloacal vent
2. Notched tongue
3. Full-body ecdysis
4. Imperforate columella
5. Teeth attached to jaws
6. Pelvic bones fused in adults
7. Fracture planes or septa within caudal vertebrae. 

Together Sauria and Serpentes form Squamata. There are over 8,000 species within Squamata, Sauria is comprised of around 5,000 of the species.

L to R: Varanid skull (dorsal), Anolis skull (dorsal), Varanid skull (ventral)

Squamata is defined by over 50 synapomorphies and characteristics from their skeletal and soft anatomy. Some of these include: 
1. Fused premaxillae
2. Fused parietals
3. Reduced nasals
4. Lack of vomerine teeth
5. Well-developed hemipenes
6. Saccular ovaries
7. Jacobson’s organ
8. Femoral and pre-anal glands
9. Egg tooth at hatching.

Varanid skull with bones labeled

The systematics of defining Sauria are at this time controversial.  Based on morphological data and molecular data, as well as combinations of the two, there have been many evolutionary hypotheses prosposed. Currently there are at least 19 families within Sauria, but there may be as many at 36. A lot of these debates have been whether or not to elevate subfamilies to family-level status.

In lab we had nine families to observe: Agamidae, Anguidae, Chamaeleonidae, Gekkonidae, Helodermatidae, Iguanidae, Scincidae, Teidae, and Varanidae. We learned the number of genera, distribution, some characteristics, and some biology of each of these families.

Number of genera: Agaminae = 52; Leiolepidinae = 2
Distribution: Africa, Asia, and Australia
Characteristics: Small to large lizards (45-350 cm adult SVL); covered dorsally and ventrally by overlapping scales or granular; juxtaposed scales; no osteoderms dorsally or ventrally on the trunk; all species limbed; long tail; and the tongue is covered dorsally with reticular papillae and lacks lingual scales; the foretongue is nonretractable.
Class specimen: Subfamily: Agaminae; Genus: Draco
Distribution: Africa, Asia, and Australia
Characteristics: Large lacrimal foramina and epiotic foramina.
Biology: Terrestrial and semiarboreal; slender and long-limbed; diurnal, extension of the ribs for gliding (airfoil); oviparous; predominately carnivorous; acrodont teeth.

Number of genera: Anguinae = 3; Anniellinae = 1; Diploglossinae = 3; Gerrhonotinae = 6
Distribution: Disjunct, Americas, Europe, Southwest Asia, and southern Asia  
Characteristics: Small (55-70 mm) to very large (500-520 mm); limbed to limbless lizards; all are heavily armored with largely overlapping scales; a longitudinal ventrolateral groove of fold separates the dorsal and ventral scale armor in some taxa; tails are very short to very long; caudal autonomy in common; and the foretongue retracts into the hind tongue.
Class Specimen: Subfamily: Anguinae
Distribution: North America and Eurasia
Characteristics: Robust, elongate, limbless lizards; long tail, typically twice the length of the body; and have pleurodont teeth.
Biology: Diurnal; consume arthropods, and small vertebrates; and some are viviparous.

Number of genera: 6
Distribution: Africa, the Middle East, Madagascar, southern Spain, Sri Lanka, and India 
Characteristics: Laterally compressed bodies; prehensile tails; head casques covering necks; xygodactylous feet; projectile tongues; independently movable eyes with muffler-like lids; most species have skin of small, juxtaposed scales; no osteoderms; all species are limbed; and have acrodont teeth
Biology: Largely, but not exclusively arboreal; stalkers, walking along narrow branches with a slow, jerky gait; adjust their body colors to their background; and both viviparous and oviparous.

Number of genera: Diplodactylinae = 20; Eublepharinae = 6; Gekkoninae = 79; Pygopodinae = 7
Distribution: Pantropic on all landmasses   
Characteristics: Most species are covered dorsally and ventrally by small, granular scales; no osteoderms occur dorsally, but are ventral on some; most species are distinctly limbed; caudal autonomy is common; and pleurodont dentition.

Eublepharinae: Eublepharis
Class specimen: Subfamily: Eublepharinae; Genus: Eublepharis
Distribution: Disjunct in southwestern North America and northern Central America, and sub-Saharan Africa and southern Asia
Characteristics: Body not elongate or snake-like; limbs are well developed; skin is soft with numerous small juxtaposed scales; and the eye lacks a spectacle cover and usually contains 20 or more sclerotic ossicles.
Biology: Most are terrestrial; all are nocturnal insectivores; large tail looks like head to confuse predators, and is used for fat and water storage.

Gekkoninae: Hemidactylus
Class specimen: Subfamily: Gekkoninae; Genus: Hemidactylus
Distribution: Pantropic and temperate Eurasia
Characteristics: Body not elongate or snake-like; limbs are well developed; skin is soft with numerous small juxtaposed scales; and the eye is covered by a spectacle and contains 14 sclerotic ossicles.
Biology: Greatest species richness of all lizard groups; most are nocturnal; most are rupicolous or arboreal; most are insectivorous; and all are oviparous.

Number of genera: 1
Distribution: Southwestern North America, from the Sonoran Desert southward along the Mexican Pacific coast to Guatemala 
Characteristics: Large lizards (300-500 mm adult SVL); only lizards with well-developed venom glands; broad, flattened heads; robust bodies; short well-developed limbs; heavy tails; thick skin with rows of rounded scales circling the body, giving a beaded appearance; scales are somewhat tuberculated; caudal autonomy does not occur, and pleurodont dentition.
Biology: Daily activity patterns vary with the season; surface activity only takes place in order to find mates and forage; and can consume large prey, which has to pass through their large pectoral girdle, unlike snakes.

Number of genera: Corytophaninae = 3; Crotaphytinae = 2; Hoplocercinae = 3; Iguaninae = 8; Oplurinae = 2; Phrynosomatinae = 10; Polychrotinae = 8; Tropidurinae = 11
Distribution: Throughout the Americas, Madagascar, and west-central Pacific islands 
Characteristics: Many covered dorsally and ventrally with large, keeled, overlapping scales, and other with small, granular scales; no osteoderms dorsally or ventrally; tail long; many have caudal autonomy; and have pleurodont dentition.

Corytophanine: Basiliscus

Class specimen: Subfamily: Corytophaninae; Genus: Basiliscus
Distribution: Southern Mexico to northern South America
Characteristics: Males lack femoral pores.
Biology: Some arboreal, but basilisks are low-level forest inhabitants; can run bipedally, this can be across the surface of water; casque-headed, slender-bodied, long-limbed, and long-tailed lizards; and oviparous.

Iguaninae: Ctenosaura
Class specimen: Subfamily: Iguaninae; Genera: Iguana; Ctenosaura
Distribution: Americas from southwestern United States to Paraguay and southern Brazil, West Indies, Galapagos, and west-central Pacific islands
Characteristics: Males have femoral pores.
Biology: Predominately terrestrial; typically herbivores; and all are oviparous.

Phrynosomatinae: Sceloporus (Male-left, female-right)
Class specimen: Subfamily: Phrynosomatinae; Genus: Sceloporus
Distribution: Southern half of North America to western Panama
Characteristics: Males have femoral pores.
Biology: Dominant iguanid lizards of North America and Mexico; largely arid-adapted species; predominately moderate sized lizards; and typically oviparous, but some are oviparous. 

Polychrotinae: Amolis

Class specimen: Subfamily: Polychrotinae; Genus: Anolis
Distribution: Southeastern United States through Central America and the West Indies to nearly the southern tip of South America
Characteristics: Males lack femoral pores.
Biology: Most specious iguanid lizards; predominately arboreal; most are sexually dimorphic, with larger males; all are diurnal; and anoles have continual egg production.

Number of genera: Acontinae = 4; “Scincinae” = 133
Distribution: Nearly worlwide
Characteristics: Nearly always covered dorsally and ventrally by overlapping scales; osteoderms underlie the scales dorsally and ventrally on the trunk; strong limbed to no external limbs; and caudal autonomy is common.
Class specimen: Subfamily: “Scincinae”; Genera: Eumeces; Plestiodon; Scincella
Distribution: Nearly worldwide but not extending much above 60° N latitude, and absent from Antarctica
Characteristics: Limbs are usually present, although limb reduction has evolved independently many times.
Biology: Highly diverse group, taxonomically, ecologically, behaviorally, and in terms of reproductive diversity; most have cylindrical body and tail short limbs, and smooth scales; most are diurnal; some herbivorous, but most carnivorous; and most are oviparous, but many are also viviparous.
L to R: Plestiodon, Scincella, Eumeces (all Scincinae)

Number of genera: Teiinae = 6; Tupinambinae = 4
Distribution: Americas, from northern United States to Chile and Argentina
Characteristics: Dorsal and lateral body scales are usually small and granular, whereas the ventral scales are typically larger and juxtaposed; no osteoderms dorsally or ventrally on the trunk; all have well-developed limbs; tail is autonomous; and have pleurodont dentition.
Teiinae: Cnemidophorus

Class specimen: Subfamily: Teiinae; Genus: Cnemidophorus
Distribution: Southern North America to northern Argentina
Characteristics: Nasal process on the maxillary.
Biology: Streamlined body, long whip-like tail, and long hindlimbs; active foragers, use vision and chemical cues to detect prey; tend to avoid insects with chemical defenses; and all are oviparous.

Number of genera: Lanthanotinae = Monotypic; Varaninae = 1
Distribution: Warm temperate and tropical Africa, Asia, and Australia
Characteristics: Generally large lizards; thick skin with numerous rows of small, rounded scales; ventral scales are slightly larger than dorsal; dorsal portion of the trunk lacks osteoderms; monitors have well-developed limbs; and have pleurodont dentition.

Varaninae: Varanus
Class specimen: Subfamily: Varaninae; Genus: Varanus
Distribution: Sub-Saharan Africa eastward through Asia to Australia and islands in the southwestern Pacific
Characteristics: Have parietal eye; and have hemibaculum (cartilaginous strut in each hemipenis).
Biology: Relatively small heads, long necks, robust bodies, well-developed limbs, and long, muscular tails; most are active predators; conically recurved teeth; and all are oviparous.

Sceloporus undulates garmani (Northern Fence Lizard)
Scincella lateralis (Ground Skink)
Eumeces fasciatus (Five-Lined Skink)
Eumeces laticeps (Broad-Headed Skink)
Eumeces anthracinus anthracinus (Northern Coal Skink)


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