Wednesday, February 22, 2012

Lab 5: Lepidosauria part 1: Sphenodontida and Sauria (Michele and Brad)

Lepidosauria: Sphenodontida and Sauria
Glass Lizard (Family: Anguidae Genus: Ophisaurus )

Sphenodontida & Sauria are within the major lineage Lepidosauromorpha. Some of the synapomorphies that are present within this lineage are a transverse cloacal vent, a notched tongue (along with lingual prehension to capture prey), full-body ecdysis, an imperforate columella, teeth that are attached to the jaws, adults with fused pelvic bones, and fracture planes or septa within caudal vertebrae. Sphenodontida and squamates diverged in the early Late Triassic.


Squamates have many derived features, including well developed hemipenes, saccular ovaries, Jacobson's organ, femoral and preanal glands, and an egg tooth for hatching. Lizards and their snake descendants are the only non-extinct squamates. Excluding snakes, there are about 4450 species of lizards within approximately 19 families (there may be as many as 36 families). Controversy surrounds the number of lizard families there actually are, because many scientists believe many subfamilies should be raised to family status, especially within the Iguanidae. For this lab, we examined the anatomy of a Varanus skull. we had unknown lizards on our tables and identified them to family and looked at some of their major features.

Varanus skull anatomy

Some of the bones in Dorsal View:

Light Green = Septomaxilla
Grass Green = Jugal
Orange = Nasal
Dark Green = Quadrate
Pink = Maxilla
Light Blue= Premaxilla
Yellow = Parietal

Ventral View

Purple = Basisphenoid
Pink = Maxilla
Blue = Post orbital/post frontal
Dark Green = Quadrate
Red = Pterogoid
Yellow = Palatine

Representatives from selected lizard families
(Identified unknowns from lab):

Family: Agamidae
Subfamilies: Agaminae (52 genera), Leiolepidinae (2 genera)

Distribution: Old world - Africa, Asia, Australia

Characteristics of family: Acrodont dentition, highly arboreal, and feed on arthropods. This amazing genus is able to glide using dorsal skin flaps supported by elongate ribs, and control the direction of their gliding.

Subfamily pictured: Agaminae
Genus: Draco

Family: Anguidae

Subfamilies: Anguinae (3 genera), Anniellinae (1 genus), Diploglossinae (3 genera), Gerrhonotinae (6 genera)

Characteristics of family: Limbed to limbless lizards, heavily armored with non-overlapping scales, osteoderms underlie the ventral and dorsal scales on the trunk, interclavical is absent or cruciform, pleurodont dentition.

Distribution: Americas, Europe, southwest Asia and southern Asia.

Subfamily in lab: Anguinae

Family: Chamaelionidae

Pictured below: Genus: Chamaeleo
Genera: Bradypodion, Brookesia, Calumma, Chamaeleo, Furcifer, Rhampholeon

Characteristics of family: Xygodactylous feet, head casques covering their necks, projectile tongues, independently moving eyes, prehensile tail, acrodont dentition.

Distribution: Africa, Middle East, Madagascar, southern Spain, Sri Lanka, India

Family: Gekkonidae

Subfamilies: Diplodactylinae (20 genera), Eublepharinae (6 genera), Gekkoninae (79 genera), Pygopodinae (7 genera)

Distribution: On all continents, widespread

Family Characteristics: Second most speciose family of lizards, behind skinks, covered by small, granular scales interspersed with tubercles, no osteoderms dorsally, pleurodont dentition. The Leopard gecko, Eublepharus macularius, (pictured to the left) has extra fat and water stored in the tail, which is believed to confuse predators into believe their tail is actually their head.

Below is Hemidactylus frenatus, the Common House gecko. Originally from southeastern Asia and now an invasive in America.

Family: Helodermatidae

Genus: Heloderma

Family Characteristics: Large bodied (300 - 500 mm SVL), the only lizards with venom glands, broad & flattened heads, robust bodies, thick skin with rows of rounded scales that look like beads (see the picture to the right). Pleurodont teeth.

Distribution: Southwestern North America, along the pacific coast to Guatemala.

Mexican beaded lizard: Heloderma horridum

Family: Iguanidae

Pictured Below:
Northern Fence Lizard (Sceloporus undulates garmani), male has dark pattern on belly, female does not.
Subfamilies: Corytophaninae (3 genera), Crotaphytinae (2 genera), Hoplocercinae (3 genera), Iguaninae (8 genera), Oplurinae (2 genera), Phrynosomatinae (10 genera), Polychrotinae (8 genera), Tropidurinae (11 genera).

Family Characteristics: Covered dorsally and ventrally by large, keeled, overlapping scales, others with small granular scales, tail is usually long, dentition is pleurodont.

Distribution: Americas, Madagasca, west-central Pacific islands

Subfamily: Iguaninae, Iguana iguana

Subfamily: Corytophaninae Genus:Basiliscus

Subfamily: Iguaninae Genus: Ctenosaura

Family: Scincidae

Subfamilies: Acontinae (4 genera), Scincinae (133 genera)

Family Characteristics: The most diverse family of lizards, covered with overlapping scales dorsally and ventrally, osteoderms underlie the scales, body forms range from strong limbed to no external limbs, autotomous caudal vertebrae have a fracture plane anterior to the transverse process, pleurodont dentition.

Distribution: Nearly worldwide.

Pictured above (starting from top): Eumeces fasciatus - Five-Lined Skink, Eumeces laticeps - Broad-Headed Skink, Scincella lateralis -Ground Skink (displaying a tail lost due to caudal autotomy)

Family: Teiidae

Subfamilies: Teiinae (6 genera), Tupinambinae (4 genera), Chamopsinnae (extinct clade), Polyglyphanodontinae (extinct clade)

Family characteristics: Dorsal and lateral scales are small and granular, but ventral scales are large, juxaposed, and arranged in transverse rows, no osteoderms, tail is autotomous and usually long, pleurodont dentition.

Distribution: Americas, United states to Argentina and Chile

Cnemidophorus tesselatus (subfamily: Teiinae)

Family: Varanidae

Subfamilies: Lanthanotinae (1 genus: Varanus), Varaninae (1 species: Lanthanotus borneesis)

Family Characteristics: Generally large, thick skin with rows of small, rounded scales circling the body, pectoral girdle has a t-shape, tail is very long, pleurodont dentition.

Distribution: Warm temperature and tropical Africa, Asia, and Australia

Subfamily: Varaninae Genus: Varanus

Species of lizards found in Ohio:
Family: Iguanidae
Sceloporus undulates garmani - The Northern Fence Lizard
Family: Scincidae
Scincella lateralis -Ground Skink
Eumeces fasciatus - Five-Lined Skink
Eumeces laticeps - Broad-Headed Skink
Eumeces anthracinus anthracinus - Northern Coal Skink

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