Herpetology- Introduction and Classifications

Herpetology

Study of amphibians and reptiles

• “Herpeton” = “crawling things”

• “Logos” = “reason or knowledge”

Phylogeny Basics

• Node = common ancestor

• Along each branch = unique evolutionary history

• Sister = all share a common ancestor or share the most recent common ancestor

Classification of Reptiles and Amphibians

• Egg Type

  • Anamniotic Egg

  • Amniotic Egg

• Skull Type

  • Anapsid

  • Synapsid

  • Diapsid

• New Discoveries

  • Discovered turtles were diapsid 

  • Initially thought to be anapsid

  • Ancestors had diapsid skulls

• Notes of Interest

  • 1- fish and amphibians separated by amniotic eggs 

  • 2- mammals separated by synapsid skull 

  • 3- crocs and bird separated by 4 chambered hearts and only living Archosauria

Anamniotic Egg

Simple, shell-less egg that must be laid directly in water

Amniotic Egg

Specialized waterproof egg that allowed animals to reproduce on dry land without needing water

Anapsid

No holes in the skull

Synapsid

One hole in the skull

Diapsid

Two holes in the skull

External vs Internal Fertilization

• External Fertilization- reproductive process where a male’s sperm fertilizes a female’s egg outside the female’s body

• Internal Fertilization- reproductive process where a male’s sperm fertilizes a female’s egg inside the female’s body

Direct vs Indirect Development

• Direct Development- biological process where an animal is born/hatches as a miniature version of the adult without going through larval state or metamorphosis

• Indirect Development- biological process where an animal hatches from an egg in a larval form that looks very different from the adult

Class Amphibia, Order Anura

Frogs and toads

• General

  • 85% of amphibians

  • External fertilization

  • Indirect development

  • Fused head/trunk- can’t move head super well

  • Modified limbs- often for jumping

• Families

  • Family Ranidae- true frogs

  • Family Hylidae- toe pads; tree frogs and their allies

  • Family Bufonidae- true toads

  • Family Brevicipitidae- round, burrowing frogs

  • Family Centrolenidae- translucent skin; glass frogs

  • Family Dendrobatidae- aposematic coloration, toxicity; poison dart frogs

Class Amphibia, Order Caudata

Salamanders and newts

• General

  • “Cauda” = tail

  • N. America has ~⅓ of species

    • Disproportionate share of the world’s biodiversity

    • True hotspot, especially Appalachian Mountains 

  • Internal/External fertilization- primarily internal, rarely external

  • Indirect and direct development

• Families

  • Family Plethodontidae- lungless salamanders

    • Most genetically and species diverse

    • Unique among terrestrial vertebrates in lacking lungs and breathing through skin instead

      • Pretty common across all amphibians but necessary in plethodons  

    • Includes red-backed salamanders

  • Family Ambystomatidae- mole salamanders

    • Includes spotted and tiger salamanders

  • Family Cryptobranchidae- giant salamanders

  • Family Sirenidae- fully aquatic salamanders

  • Family Salamandridae- true salamanders and newts

Class Reptilia, Order Squamata

Snakes and lizards

• General

  • 2nd largest vertebrate order

  • Paired hemipenes

  • Internal fertilization

  • Direct development 

• Families

  • Family Colubridae

  • Family Scincidae- skinks

  • Family Viperidae- venomous pit vipers

    • Includes rattlesnakes, copperheads, vipers

  • Family Chamaeleonidae- chameleons

  • Family Anguinae- legless lizards

  • Family Gekkonidae- geckos

Class Reptilia, Order Testudines

Turtles

• General

  • Shell (bony or cartilaginous)

  • Internal fertilization

  • Direct development

• Families

  • Family Chelydridae- snapping turtles

  • Family Emydidae- pond and marsh turtles, terrapins

  • Family Trionychidae- softshell turtles

  • Family Testudinidae- tortoises

  • Family Cheloniidae- modern sea turtles

  • Family Podocnemididae- aquatic side-necked turtles

Class Reptilia, Order Crocodilia

Crocodiles, alligators, and caiman

• General

  • 4 chambered heart

  • Dermal, bony plates

  • Thecodont teeth- set in individual bony sockets within the jawbone

• Families

  • Family Crocodylidae- crocodiles

  • Family Alligatoridae- alligators and caiman

  • Family Gavialidae- ghariels