Herpetology Notes

Caecilians Characteristics

  • Segmented 

  • No limbs 

  • No pelvic girdle 

  • Tail highly reduced in size or absent 

  • Highly reduced eye, in some cases it is covered by bone 

  • Sensor tentacles 

  • Compact skull (strong as it is very bony) 

  • Relatively large teeth, two rows in upper jaw  

  • Cloaca of males is eversible (intromittent organ), known as phalloduem 

  • Bony Scales may be present between annular rings 

  • 60-290 vertebrae 

  • Size range: 10.2 cm to 152 cm (5 ft) 

  • Highly specialized for burrowing, some are entirely aquatic 

Caecilian Phylogeny/zoology

  • Difficult to study due to political issues around the world.  

  • Moist environments, can get to high densities but difficult to track 

Tentacles

  • Used for picking up large organic scent molecules from surface of the environment 

  • Small volatile scent molecules detected using olfactory cells associated with the nasal epithelium  

Feeding and jaw structure 

  • Sharp teeth and strong jaws, will do a death roll sometimes 

Skull morphology 

  • Having a big head and strong bite is great for a predator, but not so good for burrowing. 

  • To open mouth: Contract depressor mandibulae, skull goes up, lower jaw stays in place.(think handles of bolt cutters) 

  • To close mouth: 1) Interhyodeus muscle contracts, 2) capitis longus contracts, 3) adductor muscles contract 

Subdermal scales and mucous glands 

Subdermal scales embeded in skin 

Body morphology: Movement and locomotion 

  • Two sets of muscles: One set just under skin, second wrapped around spinal column 

  • Mechanics of movement: exterior part of animal is ½ wavelength out of phase with spine. Completely unique among vertebrates. 

  • Reciprocating locomotion: used in burrowing 

Caecilian reproductive modes 

  • All species use internal fertilization (as far as we know) 

  • Approx 25% of species w/ free-living larval stage 

  • 25% direct development 

  • 50% viviparous 

Reproduction II: Dermatophagy 

  •   Skin sloths off in a milky substance for young to eat 

Reproduction III: Matorphagy  

  • Fetal dentition: transitory non-pedicellate teeth 

  • Juveniles graze on rapidly proliferation endometrium 

  • Offspring may eat their mothers weight in mass every 2-3 weeks 

  • When consumption > than proliferation, birth occurs 

Salamander Characteristics 

  • 12-40 trunk vertebrae, 20 – 80 caudal vertebrae (Note: caecilians may have hundreds of vertebrae) 

  • Limbs reduced in some (Sirens, and amphiuma) 

  • Fertilization external or internal via spermatophore 

  • Aquatic larval stage present or absent 

  • Paedogenesis common 

  • Mostly New World distribution (only one species in New World tropics 

Reproduction 

  • Majority of salamander families have internal fertilization via spermatophore 

Metamorphosis 

  • Split habitat resources: 

    • aquatic vs. terrestrial 

  • Larvae completely carnivorous 

    • suction feeding mechanism 

    • do not have pedicellate teeth 

  • Neuromast organs: sensory and orientation Larvae lack poison glands of adult 

  • Alteration of skeletal elements in skull 

Salamander Feeding specializations 

  • Two patterns: 

    • Ancestral: wide spread in majority of families 

    • Derived: only present in Plethodontids (esp. Bolitoglossines) 

  • Urohyal may be present or absent 

  • Circumglossus gone 

  • Genioglossus gone 

  • Epibranchials are really long 

Parental care 

  • Trait probably evolved independently several times in salamander lineages.  

  • One sex guards clutch  

  • Role of fungicides and bacteriocides  

Internal retention of eggs 

  • Occurs in only two genera of salamandrids 

    • Two patterns: 

      • Several eggs ovulated but only one or two eggs hatch in oviduct. Larvae consume yolk of unfertilized eggs. 

      • 1. Eggs hatch, larvae begin to consume eggs and eventually each other. 

      • 2. In both cases, young are born fully formed, up to 2/3 size of adult. 

      • Gestation 1.5-2 yrs. 

Ecological implications of cutaneous versus pulmonary ventilation 

  • Lungless salamanders: have miniscule home ranges (e.g. 0.4 - 0.7 m2 )  

    • Home range size decreases with body size  

  • Lunged salamanders: long range migrations of several hundred meters to breeding ponds common (e.g. one Ambystoma tigrinum individual moved 162 m in a single night!) 

Anuran Characteristics 

  • 5-9 trunk vertebrae 

  •  Several caudal vertebrae fused forming urostyle located between ilia  

  • Skull large and broad with frontal and parietal bones fused  

  • Pelvic girdle very long, and hind limbs much longer than forelimbs  

  • Carnivorous as adults 

Anuran Taxonomy 

  • Highly specialized larval and adult morphologies (under largely independent selective regimes)  

  • Age (> 200 mya) 

  • Tremendous species diversity (e.g. 9 anuran families have only 1-3 species each) 

Morphological and zoogeographic characteristics used 

  • Tongue structure: present absent, two modes of protrusion  

  • Pectoral girdle  

  • Vertebrae, anatomy and number  

  • Zoogeography (it’s a rat’s nest of relics and convergence)  

  • Larvae: four recognizable forms 

Phylogeny of anuran families 

  • Neobatrachia: True, or “higher” frogs. Group contains 95% of extant frog species., presence of firmisternal pectoral girdle.  

  • Pelobatoidea (Mesobatrachia): historically named because its position representing an intermediate lineage between primitive (Archaeobatrachia) and true (Neobatrachia) frogs. Shows a mosaic of derived and primitive traits. + +  

  • Archaeobatrachia: “primitive” frogs, ribs are not fused to vertebrae, presence of arciferal pelvic girdle.  

Larvae 

  • Initially limbless, often with horny beak Surrounded by pad covered with horny denticles  

  • Gills internal, covered by large chamber with one or two openings Most herbivorous or suspension feeders  

  • Abdomen filled with very long spiral intestine  

  • Metamorphosis of larvae into adults most extreme of all vertebrates  

  • Direct development in a few species, none are neotenic 

Larval Stage 

  • Exploit high primary productivity from temporary bodies of water  

  • Most are herbivorous or suspension feeders, a few species are carnivorous Tadpole rasps surface and food floats free  

  • Food is drawn into mouth and particles become caught in mucous net overlaying the gills  

Metamorphosis 

  • Tadpoles have little or no bone, so bone formation must occur in adult frogs.  

  • Changes: Horny beak falls off Palatoquadrate shortens, becomes vertically oriented while at the same time mandible elongates  

  • Antorbital process and ethmoid cartilage fuse Kidneys: ammonia to urea Brain “re-wired”  

  • Gene-expression differences: larvae versus adult 

Reproduction 

  • Eggs and larvae in water  

  • Eggs on land, larvae in water  

  • Direct development  

  • Parental care  

  • Internal development of tadpoles  

  • Viviparity (at least 9 species)  

  • Mostly external fertilization, however there are several independent origins of internal fertilization  

Reptiles

  • Defining Characteristics  

    • Elongate, armored bodies with osteoderms, long snout and relatively broad laterally compressed tails 

    • Akinetic, flat skulls, modified diapsid type 

    • Thecodont dentition – tooth has root imbedded in jaw (like us) 

    • Legs relatively short with webbed feet 

    • Aquatic 

    • Eye with nictitating membrane 

    • Lung ventilation via hepatic piston pump 

    • multi cameral lung- multiple chambers 

    • Four chambered heart 

    • Lingual salt glands- except American alligator 

    • All species oviparous with maternal care of eggs 

    • Lack urinary bladder 

    • Vertical cloaca 

    • Egg tooth caruncle 

    • Dome pressure receptors 

  • Geographic Distribution 

    • Alligatoridae 

      • Southeast NA 

      • Central and SA  

      • Small part of eastern China (Alligator sinensis) 

    • Crocodylidae 

      • Central America and very top of SA 

      • Everywhere but the Sahara and South Africa, in Africa 

      • India, Indonesia and Malaysia and top of Australia 

    •  Gavialidae 

      • Splotchy areas with water in India, Gavialis gangeticus 

      • Malay Peninsula, Borneo and Sumatra, Tomistoma schlegelii 

  • Mechanics of feeding 

    • DEATH ROLLLLLLL 

    •  

  • Diving adaptations 

    • Submerged breathing 

      • Closed throat, but internal naris allows for air to come through.  

    • Cardiovascular 

      • Cardiovascular adaptations 

        • Blood flow can bypass lungs during a dive and a majority of blood is directed to the body (right to left shunt) 

        • This happens because of vasoconstriction of lung blood vessels  

      • A) crocodilians have divided ventricles 

      • B) During steady air breathing, there is low pressure in right ventricle and high pressure in L. ventricle. Right ventricle has a valve that stays closed during this, it connects to the foramen of Panizza 

      • C) During diving or breath-holding, both valves are open and both ventricles have same pressure. (Free flow) 

    • Lung ventilation 

      • Hepatic (liver)  piston pump 

        • The muscles attached to the pelvic girdle moves the liver back, increasing the volume in chest, causing negative pressure to suck air into the lungs 

  • Reproduction 

    • TSD 

    • Complex parental care 

      • Alligators and caimans generally construct above ground nests with vegetations, while crocodiles and Gahriels construct nests in soil 

    • Young use vocalization to communicate with mother 

    • Complex courtship behaviors as well 

  • Bellowing 

    • Audible bellow 'water dance' 

    • Sub audible vibrations initiate pressure waves that are propagated through water 

      • Head slaps, which can indicate location of male, sub audible vibrations may indicated size 

  • Tool use 

    • Mugger crocodile in stick displaying behavior, lure for birds 

  • Similarity with birds 

    • Territorial 

    • Vocalization and communication 

    • Nest construction 

    • maternal care

  • Alligator mississippiensis 

  • Range: South east USA, doesn't go further north than Virginia or south than Texas  

  • Interesting Biological Traits 

    •  Thermoregulation: evaporative cooling, basking with their mouth open 

  • Do alligators have determinant growth 

    • Used growth rings on alligator long bones to determine growth rates 

    • Determined that alligators and probably other crocodilians have determinant growth.  

  • Generalist feeding strategy 

    • Fish, turtles, reptiles, and mammals 

  • Reproduction 

    • Eggs are laid in a vegetation made mound by mothers, always in a dry area but near water 

    • Salt water influx can destroy nests as freshwater is needed instead 

    • Females use limbs and jaws to construct a nest mount 

    • On average 3-5 ft in diameter, 2-3 feet in height   

    • Up to 60 eggs deposited in each 

    • Microbes eating vegetation and sun beating down heat the nest 

    • Eggs are calcified and rough, ( sand paper) 

    • When newly laid, they will form an opaque calcified band around the center of the egg if fertile 

      • Up to 3 sires for each nest recorded 

    • Nest attendance 

      • Ecosystem engineers- animals that modify the environment in a way that is enhancing, they create wallows and little tracks and runways throughout the marsh 

      • Some alligator mothers are better than others, will attend the nest consistently and leaving only occasionally to eat, drink or cool off. Others may leave more often, and this opens up an opportunity for nest predation. 

      • Most predation occurs about 24-48 hours after being laid, so if they live that long, more chance of hatching. 

      • Guard holes often dug by female during nest construction 

      • Usually within sight of nest, connected by a run. 

      • Defense of nest and young 

        • Maternal female alligators are extremely defensive of their young and will defend their nest sites and their young 

      • Hatchlings 

        • Pattern fades as young grow older 

        • Chirping/vocalization 

          • Call for mother 

          • Often from within nest mounds indicating for mother to open the nest 

        • Egg tooth 

      • How are they ecosystem engineers? 

        • Create wet and dry conditions throughout the marsh 

          • Holes 

          • Trails 

          • Nests 

        • Their pathways allow for movement of other species, nests are used by many nest associates 

      • Final Thoughts 

        • Nuisance alligators are individuals that are at least 5 feet in length that pose a threat to pets, livestock, or humans 

        • Nuisance alligators are created by humans feeding and/or harassing alligators 

          • Alligators may be curious but they should not approach you 

          • They have an innate fear of humans, once that fear is lost they pose a threat to both themselves and to you 

Phylogenic position of Lepidosauria 

  • Divulged later in time than turtles and crocs 

Major Anatomical differences between Lepidosaurs and Archosaurs 

Trait 

Archosaurs 

Lepidosaurs 

Antorbital Fenestra 

Yes, secondarily lost in crocs 

No antorbital fenestra 

Dentition 

Thecodont 

Pleurodont or acrodont 

Egg tooth 

Caruncle (CaCO3 toothlike structure) 

Fused to premaxilla 

Heart 

4 chambers (2 atria completely divided ventricle) 

3 chambers (single ventricle) some mixing of oxygenated and deoxygenated blood 

Cloaca 

Longitudinal 

Transverse 

Male Intromittent organ 

Single 

Eversion of cloaca in sphenodon, paired hemipenes in squamates 

Order Rhynchocephalia: Genus Sphenodon 

  • Current distribution in New Zealand, normally on coastal islands, used to be on mainland but humans and their pets have pushed them through 

  • Used to be found everywhere, but this is the only place found now 

  • Efforts to reintroduced to the main island, surrounded by a wall to keep predators out to allow the population to grow. 

  • Sphenodon punctatus and Sphenodon guntheri 

Characteristics: 

  • Unmodified diapsid skull 

  • Complete jugal bar prevents free movement of quadrate 

  • Premaxilla forms beak (much more in fossil forms) 

  • Dentition acrodont, with premaxillary egg tooth present at hatching 

  • One ro of teeth on btotom, two rows on top, not replaced if lost 

  • Body generalized, limbs not specialized 

  • 23-35 trunk vertebrae 

  • Transvers cloacal opening 

  • No male intromittent organ, copulation by cloacal apposition as in birds 

Ecology 

  • Nocturnal, forages for insects at amazingly low body temp of 6-13 degrees Celsius 

  • By day, shares burrows with shearwaters 

    • Shear waters have a high Tb= 40 degrees Celsius, so provide warmth to sphenodon sharing burrows, KLEPTOTHERMY 
       

    • Reproduction: oviparous w/ TSD, 6-10 eggs deposited in nests in the soil during autumn and overwinter in nests Hatchlings emerge in spring 

      • Possible advantage of fall oviposition & spring hatchlings is that offspring emerge at a time of abundant recourses (dipause) 

 Major Subgroupings 

Ascalobota 

Autarchoglossa 

Iguanids 

Scincids 

Chameleonids 

Teiids 

Geckkonidds 

Lacertids 

Pygopodids 

Anguids 

 

Varanids-monitor lizards 

Xantusiids (night lizards) may be transitional between ascalobotan and autarchoglossan 

  • Division is based on ecological and anatomical/structural characteristics 

Anatomical 

  • Rectus superficialis muscle: absent in ascalobotans but present in  autarchoglossan (except Xantusiidae) 

  • Osteoderms- common in autarchoglossa, rare or absent in ascalobota 

  • Scale rows/scale shape and margins 

Ascalabota: Two 'cats' of scale type       Autarchoglossan 

 

 

 

 

 

 

 

 

  • Surface of hemipenes 

  • Tongue: Necessary for food manipulation and drinking, but also for detection of non-volatile chemical compounds 

  • DIAGRAMS:  

                    Ascalobota                                                                                                                                                    Autarchoglossan  

Used primarily for drinking, tasting,                   

And food manipulation and secondary olfaction 

                                Ridges on tongue aid in food  

manipulation 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ecological and behavioral differences 

  • Ascalobotan 

    • Visually oriented 

    • Sexual dimorphism (color, sometimes size) 

    • May have bright color 

    • Ambush predator 

    • No reduction of limb or toes 

  • Autarchoglossan 

    • Chemoreception (tend to be active foragers) 

    • Color no, size yes 

    • Cryptic or fossorial 

    • Smell 

    • Reduction of limb/toes common 

  • Skull Morphology: Cranial Kinesis 

 

 

 

 

 

 

 

  • Lizards show skull reduction and other modifications for three basic reasons: 

    • Swallowing large prey 

    • Compression 

    • Burrowing 

  • Skull morphologies 

    • Typical: Unspecialized (Generalist diet) 

 

  • Highly Kinetic: 

  • Solid, akinetic: 

  • Burrowing: 

  • Archless: gekkotan 

  •  

  • Reduced or fused arches heavy osteoderms: 

  • Fossoriality and Limb loss 

    • Most highly adapted fossorial lizards are autarchoglossans. 

    • Limb loss seems to happen in the same way in every group: 

      • Overall reduction in limb size 

      • Lose components of hand 

      • Lose components of forearm 

      • Reduction of pelvic girdle and pectoral girdle: Note: pelvic girdle may be entirely missing but pectoral girdle has most elements remaining but reduced in size. 

  • Defining features of Serpentes 

    • No pectoral girdle 

    • Features of the eye 

    • Reduced left lung 

    • Elongate body form 

    • Unique skull characteristics 

      • Parietal bone and later wall of skull reduced or absent 

      • Highly mobile jaw elements (most) 

  • Snake evolution 

    • Historical predicted ecological associations: 

      • Aquatic, subterranean, dense grasslands 

    • Most likely ecological associations 

      • Evolved from aquatic, possibly marine ancestors, burrowed in soft muddy environments 

      • Ex: Lanthanotus borneensis (Lanthanotidae). Primitive lizard, likely an intermediate between helodermatids and varanids. 

  • Broad taxonomic categories 

    • Infraorder Scolecophida 

    • Infraorder Henophidia 

    • Infraorder Caenophidia 

  • The Ophidian eye 

    • Snakes: No ciliary body, no ciliary muscles, no fovea, no conus, no scleral ossicles. Eye lens yellow, color from oil droplets 

    • Lizards: yellow pigmentation in photoreceptors 

  • Method of accommodation 

    • Snakes: contraction of iris muscles moves lens forward 

    • Lizards: ciliary muscle acting on ciliary process compresses lens, alters curvature, similar to that of other terrestrial vertebrates including mammals 

  • Families 

    • Anomalepididae 

    • Gerrhopilidae 

    • Leptotyphlopidae 

    • Typhlopidae 

    • Xenotyphlopidae 

  • All fossorial, active burrowers, or use tunnel systems of ants and termites on whose larvae and pupae they feed. 

  • Taxonomy 

    • Monophyletic group based on highly conserved morphological and ecological characteristics. Current taxonomy recognized five families 

    • Recent molecular analyses suggest that the family Anomalepididae should not be included with Scoelcophidia. If so, Anomalepididae is either the sister lineage to all snakes (Scolecophidia and Alethinophidia or the sister lineage to Alethinophidia only. Either way these data suggest that the common ancestor of all snakes had a terrestrial scolecophidian phenotype. 

  • Defining Characteristics 

    • Small, 10 to no more than 95 cm in length 

    • Smooth scales, lack enlarged ventral scutes, typical of most snakes 

    • Tail short, often tipped with small spine, head blunt with reduced eyes 

    • Retain elements of pelvic girdle 

    • Skull highly modified for burrowing 

    • Limited gape, teeth modified for slashing exoskeleton of soft-bodied prey 

    • Left oviduct may be reduced or absent in some taxa 

  • Species diversity 

    • Anomalepididae: Central and South America on the coasts 

    • Leptotyphlopidae: North, Central, and South America, Africa and some parts of the middle east 

      • Rena humilis: Southern areas of California and Arizona 

    • Gerrhopilidae: Indonesia and Malaysia 

    • Xenotyphlopidae: Madagascar 

    • Typhlopidae: Central and South America, Africa and Mediterranean, Southeast Asia and Australia (Gondwana) 

  • Feeding 

    • Specialize on soft-bodied prey (larvae, pupae, or eggs) sometimes consume adult termites or ants 

    • Often gorge themselves when feeding, unlike most snakes which consume one or a few prey items at each feeding. 

    • Some species spread cloacal secretions on body that mimics pheromones of ants or termites 

    • Can push scales up, thrash, secret a smell from skin glands to ward off predators 

  • Skull Morphology 

    • Skulls generally adapted for consuming ant larvae, termite larvae and other soft-bodied prey via mandibular "raking". One species (Acutotyphlops subocularis) feeds on earth worms.

      Families 

      • Acrochordidae 

      • Colubridae 

      • Elapidae 

      • Viperidae 

      • Atractaspididae 

       

      Acrochordidae 

      • Acrochordus arafurae - File Snake 

      • Characteristics 

        • Extremely large quadrate 

        • Approx. 5% females become pregnant each year, 30 neonates per litter 

        • Can reach high population densities 

        • Seems to have a mix of caenophidian and henophidian characteristics 

        • Ecological refugees, found in SE Asia and Northern Austrailia 

        • Unique gape and suction feeding 

        • Low mas-specific metabolic rate 

        • Viviparous 

        • Maxilla changes with venom delivery 

        • Ligament connects the bottom jaws, therefore they can move independently 

       

      Feeding 

      • Neck and body muscles used to push itself around prey. No ability to pull prey inside 

      • Sequence: Upper jaw forward, then lower jaw in "walking motion" over prey 

      • Teeth curved, helps to anchor jaw in place while eating 

      • Copious amounts of saliva produced 

      • JAWS DO NOT UNHINGE 

      Evolution of venom delivery 

      • Duvernoy's gland: present in 30-40% of colubrid snakes 

        • Produces mucopolysaccharides 

        • Digestive enzymes 

        • Amines 

        • Antibiotic Function 

      • Opens into ducts near back of enlarged maxillary teeth 

      • Many if not majority of "Harmless" colubrid snakes are venomous as far as prey is concerned 

      • Likely tremendous advantages to poisoning prey items 

      Phylogeny 

      Venom Delivery Systems 

      Venom 

      • Elapids: Neurotoxic (amines, pre and post synaptic blocking agents 

      • Viperidae: Fewer neurotoxic components, increase lysozymes 

      • Elapids: Specialize for feeding on ectotherms 

      • Viperidae: Specialize for feeding on endotherms 

        • There are exceptions to both these generalizations 

       

      Infra-red photoreception 

      •   

      Rear Fanged Snakes 

      • Ophisthoglyphous 

      • Family Colubridae 

      • Fixed or limited mobility, fangs : proteroglyphous fangs are fixed in place, relatively short 

      • Derived condition found in mambas , where fangs can fold (limited) on roof of mouth (elapidae) 

      • Folding fangs(solenglyphous) long, retractable fangs 

      • Laterally deployed fangs, they are sythe shaped 

    Data 

    • Approximately 8000 venomous snake bites each year in the US 

    • On average mortality rate > 10 individuals per year 

    • Of fatal bites, 95% are due to rattlesnakes 

    • In the American South, most common snake is from the copperhead (Agkistrodon contortrix) 

    • North Carolina is the state incidence of snakebite 

    • Bites from coral snakes (Micruroides and Micrurus) 

            Symptoms 

    Pit Viper 

    Elapid 

    Hemotoxic (generally) 

    Neurotoxic 

    Intense pain 

    Minimal Pain 

    Edema 

    Pstosis (droopy eyelid) 

    Numbness, tingling 

    Paresthesia 

    Rapid Pulse 

    Diplopia 

    Muscle twitching 

    sweating 

    paresthesia 

    Sweating 

    Metallic taste 

    salivation 

    vomiting 

    hyporeflexia 

    confusion 

    Respiratory depression 

    Bleeding disorders 

    paralysis 

    If untreated, or in severe cases bite may lead to intravascular coagulation, renal failure and or hypovolemic shock 

    If untreated, or in severe cases, envenomation may lead to respiratory paralysis and death 

     

    Emergency treatment best practices: 

    • For bites of pit-vipers 

      • DO NOT add tourniquet or other device to restrict blood flow 

      • DO NOT "cut and suck" venom from bite site 

    • DO immobilize bitten extremity 

    • DO keep victim calm and avoid activity 

    • DO transport to hospital ASAP 

      • Often snake bites are "dry", that is, no venom is injected. For this reason, snake bites should be evaluated by medically-trained personnel before any invasive treatments are given 

     

    Medical Treatment 

    • CroFab (Crotalidae Polyvalent Immune Fab) anti-venom is the current treatment for all North American pit-vipers. 

      • Anti-pitviper antibodies are generated in sheep. Antibodies generated in sheep result in reduced probability of allergic response compared to anti-sera generated from horse.  

      • Multiple vials (3-4) typically required for treatment at a total cost of about $4,000 to $5,000 per vial 

      • Anti-inflammatory drugs (epinephrine and anti-histamines) also given 

    Characteristics 

    • Fossorial diapsid reptiles 

    • Skull: Jugal, post-orbital and squamosal bones absent 

    • Strong jaws, large teeth 

    • Heterodont teeth: Extremely unusual for reptiles 

    Grouped with lepidosaurs on basis of sharing 

    • Transverse cloacal aperture 

    • Paired hemipenes 

    • Premaxillary egg tooth 

    • Acrodont or pleurodont dentition 

    Differ from rhynchocephalians and squamates in: 

    • Akinetic skull 

    • Left lung functional (unlike snakes) 

    • Skull with a marked craniofacial angle 

    • Frontal bone forms lateral wall of brain case 

    • Middle ear apparatus modified by association of epihyal cartilage and stapes 

    • Teeth reduced in number but large in size 

      Pseudocopulation: false copulation behavior that is known to occur in Aspidoscelis to allow for ovulation for parthenogenesis. 

      Distribution of parthenogenesis in squamates 

      • Relatively wide occurrence in lizards and less commonly in snakes 

      • Best studied group are whiptail lizards (genus Aspidoscelis): At least 17/45 species are parthenogenesis 

      • Old world genus Lacerta 30/60 parthenogenic species 

      • Also some geckos, xantusiids, iquanids, varanids, chameleons, agamids, and a few snakes including pit vipers 

      • Ramphotyhlops braminus (Flower pot snake): all specimens found so far are female 

      Mechanism 

      • Where genetic mechanisms are known, parthenogenesis results from extra premeiotic endoduplication of chromosomes followed by normal meiosis 

      • Result: egg with two maternal chromosome compliments initiating development without fertilization 

      • Sometimes resulting child can mate with a male of either parental species, then you get a triploid 

      How hybridize? 

      • Origin of hybridization seems to be associated with habitat disturbance including anthropogenically induced habitat destruction. 

      Some origins of viviparity are ancient (e.g. boas). Age makes it difficult to determine the selective cause of viviparity in these groups 

       

      Lizards have more recent origins of viviparity, so we can test hypotheses as to what selective agents, cause viviparous reproduction 

       Reptiles and amphibians are in decline worldwide 

      • Habitat loss/Alteration 

      • Climate change temperature, moisture (rainfall patterns), sea level rise 

      • Poaching, collecting 

      • Disease:  

      • Amphibians: Chytrid Fungus- can be an important source of mortality in some populations 

      • Snakes: Ophidiomyceces- produces/results in snake fungal disease