Friday, March 2, 2012

Lab #5: Lepidosauria Part 1: Jeff Walker and Alex Valigosky

A representative of Iguanidae.

Lepidosauria Part 1. 
The group Lepidosauria is defined by several synapomorphies. Some that were observed in lab were  transverse cloacal orientation, teeth attached to jaws, and a notched tongue. Other synapomorphies were not readily visible and include derived skeletal structures and full body ecdysis. For this lab we focused specifically on several families of Saurus, the true lizards. (Squamata minus Serpentes, the snakes).

Varanid Skull Anatomy (skulls typical of members of Family Varinidae)

The exact number of lizard families is still under debate (however, there are no less then 19); in this lab, we focused on eight prominent families: 

Agamidae - Genus Draco showing the rib-supported airfoils used to glide.
Agamidae - This family contains a total 54 genera.  Their range includes Africa, Asia, and Australia.

Anguidae - This family has 4 subfamilies. Very characteristic of the family is reduction of limbs, making some Anguids look like snakes. To identify as Anguids and not snakes, you have to look for the presence of eyelids and earholes, which snakes would not have. Another characteristic that helps one differentiate from snakes is the presence of a longitudinal groove running the length of the body that separates the dorsal and ventral regions.  This family also has large armored scales, caudal autotomy, and osteoderms on the trunk.
Chamaeleonidae exhibiting xygodactyly (right) and the parietal shield (left).

Chamaelionidae - This family is composed of 6 genera with 6 species. The most distinguishing characteristic is the xygodactyly of their limbs. They are mainly arboreal and this adaption helps with tree-climbing. They have acrodont teeth arrangement and a special projectile tongue. They are sharp predators and use independently moving eyes coupled with a ridge on their face that assists in visual aim to snap up prey with their tongue. Other bodily characteristics include a parietal shield at the back of the skull that effectively protects the neck and a laterally compressed body.

Gekkonidae - This family is incredibly species and has 4 subfamilies. he family exhibits small granular scales interspaced with tubercles.  Similarly, some have scansors or lamellae. A unique adaption is the storage of fat or water in the tail. This makes the tail look like a head in shape, which can confuse many predators.
Helodermatidae - Heloderma horridum or the Mexican beaded lizard. 

Helodermatidae - One genera, Heloderma,  with two species, horridum (Mexican beaded lizard) and suspectum (Gila Monster). Their range includes Southwestern US south along the pacific through Mexico to Guatemala. They are pluerodonts and have distinctly rounded and beaded scales. On the trunk, there are many non-articulated osteoderms. They do not exhibit caudal autotomy and are the main group of lizards with dedicated venom glands.

Members of subfamilies of Iguanidae. From left: Polychrotinae, Phrynosomatinae, Corytophaninae, and Iguaninae. 
Iguanidae - This family is split into 8 subfamilies, some of which are the Polychrotinae, Phrynosomatidae, Corytophaninae,  and Iguaninae.  Many Iguanids have caudal autonomy, all are pleurodonts, and all have keeled overlapping scales. The Polychrotinae contain the Anolis and Norops along with 6 other genera. They are semi arboreal and males lack femoral pores, but have a gular flap. The Phrynosomatidae contains ten genera including fence lizards and Sceloperis, which has a representative in the Ohio reptiles. They are likewise semi arboreal but have conspicuous femoral pores in males. 
Members of Scincidae. All pictured are Ohio natives. 

Scincidae - Scincidae is a well distributed family present almost everywhere. The genera contains some 1200 species. They exhibit caudal autotomy and overlapping cycloid scales throughout the trunk. 


Teidae - Teids have large, rectangular ventral scales and smaller, similar dorsal scales. This family contains 38 genera. 

Different scale size in a monitor lizard (Varanidae, left) and Teidae (right). 
Varanidae - This family has two subfamilies , one being Varaninae which contains one genus. Within this family is all lizards commonly called monitors, and the Komodo dragon, another example of a lizard with venom glands. Their scales are small and rounded dorsally with similarly rounded but larger scales ventrally. They are pluerodonts.

Varanidae - a common monitor 

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