Lab #5: Lepidosauria Part 1: Shenodonta and Sauria

Lab #5: Lepidosauria 

Part 1: Shenodonta and Sauria

Introduction 

Eureptilia contains two extant lineages of reptiles, which are sister taxa.  These two extant lineages are Archosauromorpha and Lepidosauromorpha,  Some of the most iconic reptiles known to humans are contained within Lepidosauromorpha, which include:

• Sphenodontida (Extant Tuatara and Rhynchocephalian) 
• Sauria (Lizards)
• Serpentes (Snakes)

Lepidosauria all exhibit the following synapomorphies:

1.  Transverse cloacal aperture (vent)
2. Notched tongue (- lingul prehension)
3. Full-body ecdysis
4. Imperforate columella 
5. Teeth attached to jaws
6. Pelvic bones fused in adults
7. Fracture planes on septa within caudal vertebrae

Squamata

• Comprised of Sauria and Serpentes
• Contains over 8,000 species (5,019 species within Sauria alone)
• Inhabit all contents but Antarctica
• Found in hot and cold climates
• Found in high and low elevations 
• Found in dry and wet environments
• Found in freshwater and marine habitats
• Greatest diversity found in semiarid habitats 
• Characterized from their skeletal and soft anatomy 
• Defined by more than 50 synapomorphies

The following is a list of 12 reviewed synapomorphies discussed in lab exhibited by Squamates:

1. Fused premaxillae
2. Fused parietal
3. Reduced nasals
4. Lack of volmerine teeth
5. Specialized joints between ulna-ulnare and radius-radiale
6. Specialized ankle joints
7. WEll developed hemipenes
8. Saccular ovaries
9. Jacobson's organ (vomeronasal organ) seperate from nasal capsule
10. Lacrimal duct joining the vomeronasal duct
11. Femoral and pre-anal glands
12. Egg tooth at hatching

Anatomy of Skull in Varanus

Diversity Among Lepidosuaria

There are currently 19 extant families that have been recognized within Sauria, but may be as many as 36 families.  The greatest issue of debate over the number of families contained in Sauria pertains to the disagreement as to how large some families are and how inclusive family-level groups should be.  Ultimately there remains considerable debate over whether or not to elevate many lizard subfamilies to family-level status.  There is current consensus that the subfamilies within the family, Iguanidae, should be broken down into families.        

YELLOW ARE THE FAMILIES WE DISCUSSED IN LAB

Families Represented in Lab (alphabetical order):

Agamidae
(Angleheads, Calotes, Dragon Lizards, and Allies)

Classification: Squamata; Toxicofera; Iguania; Acrodonta; Agamidae.

Sister taxon: Chamaeleonidae.

Two Subfamilies: Agaminae and “Leiolepidinae.” 

Distribution: Africa, Asia, Australia, and Tasmania 

Droco volans 

-Have airfoil formed from ribs which is used gliding 

Anguidae

Alligator Lizards, Glass Lizards, and Allies

Classification: Squamata; Toxicophora; Anguimorpha; Anguidae.

Nine Genera: Abronia, Anguis, Barisia, Colop- tychon, Elgaria, Gerrhonotus, Mesaspis, Ophisaurus, and Pseudopus

Ophisaurus -glass lizard

no limbs 

           longitudinal fold

                                                            Chamaeleonidae

Chameleons

Classification: Squamata; Toxicofera; Iguania; Acrodonta; Chamaeleonidae.
Sister taxon: Agamidae.

Content: Ten genera, Bradypodion, Brookesia, Calumma, Chamaeleo, Furcifer, Kinyongia, Nadzikambia, Rhampho- leon, Rieppeleon, and Trioceros, with 186 species. Distribution: Africa, the Middle East, Madagascar, south- ern Spain, Sri Lanka, and India

• Acrodont teeth
• laterally compressed bodies
• prehensile tails
• head casques covering their necks 
• zygodacty- (feet fusion of sets of two and three digits, form-ing opposable, two-digited mitten-like fore and hind feet; manus fusion 1–2–3 and 4–5, pes 1–2 and 3–4–5) 
• projectile tongues
• independently movable eyes 

Gekkota

Eublepharidae
Eyelid Geckos
Classification: Squamata; Gekkota; Gekkomorpha; Eublepharidae.
Sister taxon: The ((Gekkonidae+Phyllodactylidae) Sphaerodactylidae) clade.
Content: Six genera, Aeluroscalabotes, Coleonyx, Eublepharis, Goniurosaurus, Hemitheconyx, and Holodac- tylus,  Distribution: Disjunct in southwestern North America and northern Central America, and sub-Saharan Africa and southern Asia 

Key Characteristics 

LACK TOE PADS

HAVE EYELIDS

     

Sphaerodactylidae

Dwarf Geckos
Classification: Squamata; Gekkota; Gekkomorpha; Sphaerodactylidae.

Sister taxon: The clade (Gekkonidae + Phyllodactylidae). Content: Twelve genera, Aristelliger, Chatogekko, Coleo- dactylus, Euleptes, Gonatodes, Lepidoblepharis, Pristurus, Pesudogonatodes, Quedenfeldtia, Saurodactylus, Sphaero- dactylus, and Teratoscincus     

-Small like their common name suggests(dwarf gecko)

-Have spectacles

Gekkonidae
Wall-Climbing Geckos
Classification: Squamata; Gekkota; Gekkomorpha; Gek- konidae.
Sister taxon: Phyllodactylidae.
Content: Fifty genera, Afroedura, Afrogecko, Agamura, Ailuronyx, Alsophylax, Asiocolotes, Blaesodactylus, Calodac- tylodes, Chondrodactylus, Christinus, Cnemaspis, Colopus, Crossobamon, Cryptactites, Cyrtopodion, Dixonius, Ebena- via, Elasmodactylus, Geckoella, Geckolepis, Gehyra, Gekko, Goggia, Hemidactylus, Hemiphyllodactylus, Heteronotia, Homopholis, Lepidodactylus, Luperosaurus, Lygodactylus, Matoatoa, Nactus, Narudasia, Pachydactylus, Paragehyra, Paroedura, Perochirus, Phelsuma, Pseudogekko, Ptenopus, Ptychozoon, Rhinogecko, Roptropella, Rhoptropus, Stenodac- tylus, Tropiocolotes, Urocotyledon, and Uroplatus, with 885+ species.
Distribution: Pantropic including islands. Introduced in temperate North and South America 

Most diverse group, they are large in size.
Have no eye lids but do have 14 sclerotic ossicles

Helodermatidae
Gila Monster and Mexican Beaded Lizard
Classification: Squamata; Toxicophora; Anguimorpha; Helodermatidae.
Sister taxon: The clade Xenosauridae + (Anguidae + Dip- loglossidae + Anniellidae).
Content: One genus, Heloderma, with 2 species. Distribution: Southwestern North America, from the Sonoran Desert southward along the Mexican Pacific coast to Guatemala

• large lizards (300– 500 mm adult SVL). 
• only lizards with well- developed venom glands. 
• thick skin with rows of rounded scales circling ----the body, giving them a beaded appearance
• pleurodont, and pterygoid teeth are present 
• synoptic fusion of dermal bones to skull table

Phrynosomatidae (North American Spiny Lizards) 

Classification: Squamata; Toxicofera; Iguania; Pleurodonta; Phrynosomatidae.

Sister taxon: All other Pleurodonta

Nine genera: Callisaurus, Cophosaurus, Hol- brookia, Petrosaurus, Phrynosoma, Sceloporus, Uma, Urosaurus, and Uta

Distribution: Southern half of North America to western Panama

Characteristics:

• Moderately sized lizards 
• Arid-adapted species
• Robust spiny-scaled body 
• Terrestrial and Semi-terrestrial 
• Occur in seasonal environments (reproduction strongly seasonal)

Iguanidae (Iguanas and Allies)

Classification: Squamata; Toxicofera; Iguania; Pleurodonta; Iguanidae                                Sister taxon: Crotaphytidae                                                                                                                 Eight Genera: Amblyrhynchus, Brachylophus, Conolophus, Ctenosaura, Cyclura, Dipsosaurus, Iguana, and Sauromalus                                                                             Distribution: Americas from southwestern United States to Paraguay and southern Brazil, West Indies, Galápagos, and west-central Pacific islands (Neotropics)

Characteristics:

• Typically large lizards
• Predominantly terrestrial
• Rarely descend into ground 
• Exclusively herbivorous

Corytophanidae (Casque-Head or Helmeted Lizards)

Classification: Squamata; Toxicofera; Iguania; Pleurodonta; Corytophanidae.
Sister taxon: Dactyloidae
Three genera: Basiliscus, Corytophanes, and Lae- manctus
Distribution: Southern Mexico to northern South America 

Characteristics: 

• Arboreal lizards 
• Casque-headed
• Slender bodies
• Long limbed
• Rarely ascend to ground, except to lay eggs, and forage

Dactyloidae (True Anoles)

Classification: Squamata; Toxicofera; Iguania; Pleurodonta; Dactyloidae.

Sister taxon: Polychrotidae.
One Genus: Anolis
Distribution: Southeastern United States through Central America and the West Indies to tropical and subtropical South America

Characteristics:

• Most speciose pleurodontan lizards
• Arboreal species, specialized foot morphology 
• Sexual dimorphism, males are larger
• Sit and wait predators on arthropods

Scincidae (Skinks)

Classification: Squamata; Scinciformata; Scincimorpha; Scincidae.
Sister taxon: Xantusiidae
Two subfamilies: Acontinae and “Scincinae”
Distribution: Nearly worldwide

Characteristics ("Scincinae"):

• Highly diverse group 
• Cylindrical bodies and tails
• Conical head
• well developed moderately short limbs
• Shiny, smooth scales 
• Others are short and robust with heavily keeled scales 
• Many are active foragers

Teiidae (Whiptail, Tegus, and Allies)

Classification: Squamata; Laterata; Lacertiformes; Teiidae.
Sister taxon: Gymnophthalmidae.
Two Extant Clades: Teiinae and Tupinambinae
Two Extinct Clades: Chamopsiinae and “Polyglyphanodontinae.”
Distribution: Americas, from northern United States to Chile and Argentina

  Characteristics:

• Small, granular dorsal and lateral body scales
• Rectangular, large, juxtaposed, transverse rows of ventral scales
• Many are terrestrial and forage on forest ground

Varanidae (Monitors and Goannas)

Classification: Squamata; Toxicophora; Anguimorpha; Varanidae.
Sister taxon: Lanthanotidae.
One Genus:Varanus
Distribution: Warm temperate and tropical Africa south of the Sahara, eastward through Asia to Australia and islands in the southwestern Pacific 

Characteristics:

• Large in size
• Thick skin with numerous rows of small, rounded scales circling body
• Ventral scales larger than dorsal scales
• Rectangular scales on ventral surface
• Very snake-like tongue 
• Relatively small heads with long necks and large robust bodies 
• Well enveloped limbs
• Long muscular tails 

Ohio Diversity within Lepidosauria

Within Ohio there are few native species of lizards.  the sate only contains two families and five species.  

1) Family: Iguanidae

Sceloporus undulates garmani (Northern Fence Lizard)

2) Family: Scincidae (Skinks)

Scincella lateralis (Ground Skink)

Plestiodon fasciatus (Five-Lined Skink)

Plestiodon laticeps (Broad-Headed Skink)

Plestiodon anthracinus (Northern Coal Skink)

Laboratory 6: Lepidosauria (Sphenodontida and Squamata)

Lizard families within Sauria, specimens from underlined families were investigated in lab. 

Introduction

There are two sister lineages within Eureptilia, Archosauromorpha (Lab 3 & 4) and Lepidosauromorpha.

Lepidosauria synapomorphies:
1)      Transverse cloacal aperture (vent)

      2)      Notched tongue

      3)      Full body ecdysis

      4)      Imperforate columella (stapes)

      5)      Teeth are attached to the jaws

      6)      Pelvic bones fused in adults

      7)      Fracture planes or septa within caudal vertebrae

Within Lepidosauria are the Sphenodontida, made up of extant Tuatara & Rhynchocephalians; and the Squamata, made up of Sauria (lizards) and Serpentes (snakes).

Squamata is a very numerous and diverse group of reptiles. It consists of over 8,000 species that are found on every continent in the world (except Antarctica) and on most sub tropical and tropical islands. Because these reptiles are so widely spread throughout the world, they have each developed their own unique behaviors and characteristics to adapt to environments that are either hot or cold, wet or dry, freshwater or saltwater, etc.

Squamata synapomorphies:

  1)      Fused premaxillae

  2)      Fused parietals

  3)      Reduced nasals

  4)      Lack of vomerine teeth

  5)      Specialized joints between ulna-ulnare and radius-radiale

  6)      Specialized ankle joints

  7)      Well developed hemipenes

  8)      Saccular ovaries

  9)      Jacobson’s organ separated from nasal capsule.

  10)    Lacrimal duct joining the vomeronasal duct

  11)    Femoral and pre-anal glands

  12)    Egg tooth at hatching

  

Phylogeny & Diversity

  The history of lizard systematics is a very controversial topic. Many argue over how large the families of the clade are, how inclusive family-level groups should be, whether or not to elevate some sub-families into families (for instance the subfamilies of Iguanidae), etc.  As a result hypotheses have been presented based on molecular, morphological, and behavioral evidence and many different arrangements of the reptilian clade have been put forth.  As of now, at least 19 families have been recognized, but there may be as many as 36.

“From an evolutionary perspective, it shouldn’t matter whether we recognize a group as a sub family or family, so long as we understand that the clades are real and that the relationships among them are real”

For Step 1 during lab, the anatomy of the skull in Varanus was observed. A handout was provided by Dr. Sheil which the dorsal, ventral, and lateral views for this genus. Observe the figure below and note the particular bones associated within each of the three views. This figure is for the species Varanus griseus.

See which bones you can identify on this varanid lizard skull.

Lizard Families

 We should note that there are many families of lizards for the squamates. Although not all of these families were covered in lab, Step 2 examines the following families of lizards that were present in lab. For each family, make sure that you take note of the distribution along with some of their distinct characteristics which are presented below.

Agamidae

Distribution: Africa, Asia, Australia, and Tasmania

Draco volans, a gliding agamid

Characteristics: Small to large lizards which are covered by overlapping scales or granular, juxtaposed scales dorsally and ventrally. No osteoderms are present dorsally and ventrally on the trunk region. These species are limbed, where the pectoral girdle is t-shaped. Their tail is usually long and the tongue is covered dorsally with reticular papillae. The skull possesses paired nasals, postorbitals, squamosals, frontal, and parietal; the parietal foramen usually perforates the frontoparietal suture. They possess acrodont dentition.

Anguidae

(Looks like a snake when limbless, but this anguid is not a snake!)

Do you see the eyelids on this limbless Ophisaurus?

Distribution: Americas, Europe, Southwest Asia

Characteristics: These lizards can either be limbed or limbless which have tails that can be twice the length of their body. All of them are heavily armored with largely nonoverlapping scales and contain osteoderms on the trunk dorsally and ventrally. Ventrolateral folds are well developed in most anguidswhich allows for body expansion for breathing, feeding, and reproduction. The tongue bears papillae and lacks lingual scales which are associated near the tongue. The skull can have present or absent squamosals along with a fused parietal; the parietal perforates the parietal foramen. They possess pleurodont dentition.

Chamaelionidae

Note the acrodont teeth in this chameleon

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

Characteristics: Chameleons are unique for their laterally compressed bodies, prehensile tails, head casques covering their necks, and Xygodactylous feet where sets of digits are fused forming opposable fore-and hind feet. All of these species are limbed where the specialized pectoral girdle lacks an interclavicle and clavicles. Their tails are moderately short to long and the tongue is covered with reticular papillae dorsally.

Gekkota

  The geckos examined in lab today involved three families in the subfamily Gekkota. Note the characteristics for each of these three families.

An example of a eublepharid gecko

Eublepharidae: Known as the eyelid geckos since they possess eyelids rather than spectacles! In particular, their feet lack modifications allowing them to climb.

Sphaerodactylidae: Known as the dwarf geckos, they possess well-developed limbs along with tiny juxtaposed scales. Adults are no larger than 60mm SVL Their eye is covered by a spectacle cover and do not possess eyelids.

One member of Sphaerodactylidae (top) and two members of Gekkonidae (middle and bottom)

Gekkonidae: Known as the house geckos, they possess well-developed limbs, and their eyes contain 14 scleral ossicles. They do not possess eyelids but do possess spectacle covers.

 Helodermatidae

Distribution: Southwestern North America

Characteristics: Helodermatids are large lizards and are the only lizards with well-developed venom glands. The have broad, flattened heads along with robust bodies, short limbs, and heavy tails. They have thick skin, and their scales are slightly larger and squarish ventrally. Ventrally, the trunk contains osteoderms; the tongue bears papillae, and the parietal foramen is absent. They possess pleurodont dentition.

Skull cast displaying pleurodont dentition and synostotic fusion of dermal bones to skull

 Pleurodonta

These lizards have been historically grouped into one large family named Iguanidae. This clade has recently been elevated to Pleurodonta and the historical subfamilies have been elevated to family level.

Inguanidae (prev. Iguaninae): In their skull, the lacrimal foramen is not enlarged, the jugal and squamosal are not in broad contact, Meckel’s cartilage in the mandible is fused. To determine sex, note that males possess femoral pores where the females do not.

Distribution: Americas from southwestern United States to south Brazil, West Indies, and west-central Pacific islands

Femoral pores on male iguanid

Corytophanidae: These lizards have pterygoid teeth, but no palatine teeth. Males have no femoral pores and adults are usually 90-200mm SVL.

Distribution: Southern Mexico to Northern South America

The long toes on the hind limb of this Basciliscus enable it to run on water.

Dactyloidae:  This is the most speciose family within Pleurodonta, most species range between 40-80mm SVL. Males lack femoral pores and are usually larger than females. 

Distribution: Southeastern US through Central South America and throughout West Indies

Scincidae

Distribution: Worldwide
Characteristics: The skinks are always covered with overlapping scales dorsally and ventrally. They can either possess limbs or be limbless externally. Their interclavicle is absent, so the clavicles are angular. Their tails are moderately long; tongue bears papillae; pleurodont dentition.

 Teiidae

Distribution: The Americas (from northern U.S. to Chile and Argentina)
Characteristics: This family of whiptail lizards, tegus, and allies are small to large lizards that possess smaller scales on the dorsal and lateral views of the body compared to the ventral view. All of the species within this family have well-developed limbs along with a long, autonomous tail. The posterior edges of the lingual scales are smooth; teiids possess pleurodont dentition.

Two teiid lizards (top and middle) compared to a varanid lizard (bottom) 

 Varanidae

Distribution: Warm temperate and tropical Africa south of the Sahara
Characteristics: Family of the Kamoto Dragon (Varanus), most are moderate to large in size with thick skin containing numerous rows small scales circling the body. Their ventral scales are slightly larger than the dorsal scales. Varanids possess pleurdont dentition and a hemibaculum, a cartilaginous strut in each hemipenis.


Ohio Diversity

 The final step in lab dealt with the Ohio diversity of lizards. Ohio only has two families and five species. Make sure you know the following families and species in Ohio for the exam!

Family: Phrynosomatidae

Sceloporous undulates garmani (Northern Fence Lizard)

 THE DIFFERENCE BETWEEN MALE AND FEMALE PHRYNOSOMATIDS IS THAT MALES POSSESS FEMORAL PORES. NOTE THE DIFFERENCES FROM THE PICTURE SHOWN BELOW. (A = MALE, C= FEMALE)

Family: Scincidae (skinks)
            Scincella lateralis (Ground Skink)

            Plestiodon fasciatus (Five-Lined Skink)

           Plestiodon laticeps (Broad-Headed Skink)

         Plestiodon anthracinus (Northern Coal Skink)