reptiles lecture

Lepidosauria Synapomorphies

1. transverse cloacal slit

2. tongue notched distally

3. breakage planes in tail (CAUDAL AUTONOMY)

4. ecdysis (skin shedding) synchronous

Subclass Lepidosauria (taxonomy)

• order Sphenodontida- Tuatara (1 species)

• order Squamata (12, 194 species)

  • suborder Lacertilla (Sauria)- lizards

  • suborder Amphosbaenia- worm lizards (nested within lizards)

  • suborder Serpentes (Opidia)- snakes (nested within lizards)

order Rhynchocephalia (Tuataras of New Zealand)

family Spenodontidae

• 1 genus, 2 species

• New Zealand

• fully diapsid skull

• gastralia

• acrodont dentition

• no intromittant organ

• low metabolic rate and slow growth

• known as fossils from Cretaceous

order Squamata Synapomorphies

1. paired copulatory organ (hemipenes)

2. egg tooth

3. limb reduction (multiple origins), 3 major clades exhibit it

6 major Squamate clades

• Gekkota

• Dibamidae

• Schincoidea

• Anguimorpha

• Lacertoidea

• Iguania

what 2 clades of squamates branches off early in history?

Gekkota and Dibamidae

Gekkota

• 7 families

• >100 genera, 2252 species

• found almost worldwide, but absent in some temperate areas

• most have lizard like body but one family (Pygopotidae) contains snake like species

• all carnivorous, few supplement w nectar

• most nocturnal, few diurnal

• many arborea, several terrestrial, rock dwellers, or burrowing

• range in size ~30 m to ~500 mm, include some of worlds smallest lizards (Sphaerodactylus)

• probably sister group to all other squamates, along w Dibamidae

• have many derived and unusual characteristics

• most active only at night (nocturnal) which has many impacts on other aspects like their lack of bright coloration, most communicate vocally

  • most other lizards diurnal and active during heat of day and brightly colored

  • “gecko” comes from sound made by one species from SE Asia (Tokay gecko, Gekko gecko)

  • vocalization consists of barks, chirps, and clicks

• most have large eyes (captures more light) w vertical, slit like pupils

• most lack moveable eyelids

• clean eye using tongue

• unusual in that they have clutch sizes of only 1-2 eggs, whereas other lizards have many more (20 -40 in some)

• many thrive alongside humans and are found alongside fluorescent lights outside houses at night

  • therefore are most introduced geckoes in US found in SoFlo (has 10+ introduced, 1 native species)

  • Mediterranean gecko, Hemidactylus turcicus is most widespread introduced gecko in US from southern Europe

Gecko toes

• most arboreal (living in trees) and have toe pads that let them climb on almost anything

• feet have lamella, lamellae have setae, setae have spatula (smaller bristles)

• setae (1/10 diameter human hair) and cling through intermolecular forces (Van der Walls)

  • angle is critical in forming and breaking bonds

Dibamidae

• snake like, short tailed burrowers

• males have tiny external limbs, females legless

• 2 genera, 1 genus w 1 species (Anelytropsis) in NE Mexico

• other genus (Dibamus) has 24 species in SE Asia

Iguanidae

• 48 genera, 1260 species

• 12 families

• new world, galapagos, fiji, madagascar

• visually oriented and diurnal, some arboreal

• herbivores, insectivores, carnivores

• simple tongue prehensile

• box like skull w lateral temporal arch

• pleurodont tooth attachment

• external pineal eye

Iguania- Agamidae

• 64 genera, 567 species, 6 subfamilies

• warmer parts of old world

• simple tongue- prehensile (capable of grasping)

• visually oriented and diurnal

• arboreal or terrestrial

• box like skull w lateral temporal arch

• external pineal eye

• acrodont tooth attachment

• osteoderms absent

• limbs never reduced

• draco: elongated, highly mobile ribs support thin membrane of skin- used for gliding flight

Iguania- Chamaeleonidae

• 12 genera, 222 species

• africa, madagascar, arabia, india

• boxlike skull w bony casque, acrodont teeth

• large eyes w small pupils move independently

• zygodactylus feet, mostly arboreal

• laterally compressed body

• tail usually prehensile

• projectile tongue, insectivores

• change color

Scincoidea- Cordylidae

• some species heavily armored

• armadillo girdled lizard (Ouroborus cataphractus) bites tail and makes itself into ball when attacked

• evolution of limb reduced and snake like forms in africa

Scincoidea- Scincidae

• common name among “skinks”`

• 1 of largest families of lizards along w geckoes (>159 genera, 1741 species)

• found all over the world

• typically small, diurnal, terrestrial, carnivorous

  • some giant herbivores like Corucia zebrata (prehensile- tailed skink) from Solomon Islands

• about 45% species lie bearing (viviparous)

• almost all have round, shiny, overlapping scales underlain by bones called “osteoderms)

• have reduced limbs and snake like body

• most of ~20 origins of short tailed snake like burrowing ecomorph are within skinks

• Australia has incredible diversity of skinks including giant blue tongues skink which includes shingleback

Lacertoidea- Teiidae

• 9 genera, 125+ species

• found in N, middle, and S America and W Indes

• small to relatively large

• pleurodont dentition

• most species active, diurnal, heat loving, terrestrial, and carnivorous

• Tegus- giant South American teiids, look like monitor lizards

• 1/3 of 47 Aspidocelis species are all female parthenogenetic species

all female whiptails

• all female species formed through hybridization of bisexual species (similar to ambystomatid salamanders)

• all female species typically diploid (produce unreduced, 2N eggs)

• in some cases diploid parthenogen will mate w bisexual species and form new triploid parthenogenetic species

• these species not more successful bc deleterious mutations accumulate in asexual lineages- '“Muller’s Ratchet” and sexual reproduction keeps deleterious mutations at low frequency and produces novel gene combinations

Lacertoidea- Lacertidae

• 25 genera, ±250 species

• body covered w small granular scales and large, square or rectangualr ventral

• usually w osteoderms (bony plates or scales under skin) under head scales

• several parthenogenic forms known

• pleurodent dentition

• old world

Lacertoidea- Amphisbaenia

• small, usually legless burrowers

• no external ear openings

• eyes covered w skin

• few large teeth, eat insects, grubs, worms, termites, etc

• africa, SW Asia, central and S america

• 1 eastern US species, Rhineura floridana

Anguimorpha- Anguidae

• glass lizards, alligator lizards, and relatives

  • glass lizard (Ophisaurus)- long tailed grass swimmer found in NA, europe, asia

  • all other anguid genera restricted to new world

• mostly terrestrial, diurnal, carnivores

• many viviparous species

• coolest alligator lizard: genus Abronia, live in bromeliads in cloud forests in Mexico and Guatemala

Anguimorpha- Helodermatidae

• 1 genus (Heloderma), 5 species

• considered only dangerously venomous lizards

• Gila Monster (Heloderma suspectum)- southwestern US and N Mexico in deseets

• mexican beaded lizard (Heloderma horridum)- found from NW mexico to guatemala, in dry tropical forests

Anguimorpha- Varanidae

• monitor lizards

• 1 genus (Varanus), 83 species

• asia, africa, australia (most species)

• includes worlds largest living lizard (komodo dragon, Varanus komodoensis)

• most terrestrial, some arboreal and semi squatic

• carnivorous, may eat relatively large prey, few species eat fruit

• have some development of venom

Serpentes synapomorphies

1. pectoral girdle absent

2. pelvic girdle absent or rudimentary

3. body elongated by adding vertebrae (usually 120-240)

4. 5 points of articulation in vertebrae

5. left lung absent or reduced, right lung dominant

6. genetic sex determination

7. no external ear or tympanum but can hear vibrations

8. carnivorous

Serpentes teeth categories

• aglyphous- non venemous species, no specialized teeth

• solenoglyphs- movable hollow fangs located on front of maxllae; vipers, pit vipers

• proteroglyphs- grooved fangs partially or completely closed over; fixed on front of maxillae- elapids (including hydrophiids)

• opisthoglyphs- posterior pair of teeth, on maxilla enlarged, usually grooved, aid in passage of venom but often ineffective, rear fanged colubrids (Heloderma)

solenoglyphs

movable hollow fangs located on front of maxllae; vipers, pit vipers

proteroglyphs

• grooved fangs partially or completely closed over; fixed on front of maxillaee

  • elapids (including hydrophiids): family of snakes characterized by their permanently erect fangs at the front of the mouth

opisthoglyphs

posterior pair of teeth, on maxilla enlarged, usually grooved, aid in passage of venom but often ineffective, rear fanged colubrids (Heloderma)

aglyphous

non venemous species, no specialized teeth

venoms

• elapid: neurotoxins

• viperid: hemolytic and cytolytic, except neurotoxins in some populations of 10 rattlesnake species

  • `hemolytic: can cause the destruction of red blood cells (hemolysis), leading to various complications, including anemia

  • process of cell destruction or lysis, occurs when cells are damaged or killed, leading to their breakdown and release of their contents

• colubrid venoms???

Scolecophidia- blind snakes

• Typhlopidae

• Leptotyphlopidae

• Anomalepidae

Typhlopidae

• 6 genera, 200 species

• central america and s america

• maxilla arranged transversely w teeth

• body covered w overlapping shiny scales

• eyes covered w scales but visible

• ventral scales not enlarged

• premaxillae without teeth

• dentaries without teeth

• oviparous (producing young by means of eggs that are hatched after they have been laid by the parent)

Alethinophidia- normal snakes

• about 15 family level groups

more basal groups

• Boidae (Boinae, Erycinae, Charininae, …)

• Pythonidae

Boidae

• 14 genera, 67 species, 7 subfamilies

• new world, central and E africa, middle east, oceania, madagascar

• no teeth on premaxillae

• maxillae oriented longitudinally w teeth

• dentary (the anterior bone of the lower jaw) w teeth

• viviparous (bringing forth live young that have developed inside the body of the parent) except 1 or 2 burrowing forms

• limb and girdle vestiges and spurs present

• both oviducts well developed

Boinae

• premaxillae without teeth

• relatively massive involvement of frontal in jaw support

• coronoid

• jaw relatively mobile

• elaborate vomeronasal organ and vomer bones

Pythonidae

• 11 genera, 38 species

• warmer parts of old world, australia

• teeth on premaxillae

• maxillae oriented longitudinally w teeth

• dentary w teeth

• oviparous and most females attend nests

• limb and girdle vestiges and spurs present

• both oviducts well developed

• labial pits- infrared detectors

• jaw suspension intermediate between aniliids and caenophidians

• coronoid

• limb vestiges present in musculature

• spurs extend to exterior as spurs (claws), usually larger in males

modern groups

• viperidae

• colubridae

• elapidae

• atractaspidae

Viperidae

• 41 genera, over 386 species, 3 subfamilies

• worldwide except australia, antarctica, madagascar, and some islands

• no teeth on premaxillae

• solenoglyphs- blocklike maxillae carry tubular fangs and rotate forwards for envenomation

• hind limb vestiges absent

• both oviducts well developed

• oviparous and viviparous lineages

• small to moderately large size

Colubridae

• >211 genera, 2093 species, 8 subfamilies

• 52% of all snakes

• cosmopolitan

• hind limb vestiges absent

• no teeth on premaxillae

• maxillae aglyphous, opithoglyphous, or proteroglyphous

• both oviducts well developed

• oviparous and viviparous forms

• small to moderate size

• upper jaws very loosely attaches to braincase, highly mobile

• maxillae without fangs or w enlarged grooved teeth or anterior fangs

Elapidae

• 54 genera, 398 species, 2 subfamilies

• warmer, wetter parts of world

• no teeth on premaxillae

• all venomous, most relatively harmless to humans

• maxillae w anterior, erect, grooved, or hollow fangs

• hind limb vestiges absent

• both oviducts well developed

• oviparous (eggs hatched after being laid) or viviparous (develop inside body of parent)

• small to large in size

• sea snakes and kraits (marine elapids)

  • sea snakes: 9 genera in Hydrophiinae

  • sea kraits Laticauda- in Elapinae

  • venemous

  • adaptations to marine enviro include: flattened paddle like tails, lung longer than other snakes, valved nostrils, sublingual salt glands, skin more impermeable to salt

Atractaspidae

• 13 genera, over 57 species, 2 subfamilies

• sub saharan africa and coastal arabia

• no teeth of premaxillae

• hind limb vestiges absent

• small to large fangs, which are semi erect

• left lung absent or vestigial, tracheal lung present or absent

• some dangerously venomous species

• both oviducts well developed

• oviparous and viviparous forms

• small to moderate size

• short and rotatable maxilla bears very long hollow fangs, rest of jaw suspension very thinly built

• head indistinct from body, venom glands elongate and may extend well onto body

• tail short