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Home , Agalychnis callidryas, Amphiuma tridactylum, Arthroleptidae, Bombinatoridae, Brachycephalidae, Brachytarsophrys

Characteristics, , and Evolution

Goal of the Lecture

To familiarize students with characteristics of the Class Amphibia, the diversity of extant , and the record of amphibians.

Reading Assignments:

1) Handouts (Zardoya and Meyer 2001, Laurin 2002)

2) Duellman and Trueb: pp. 424-443

Lecture Outline

Class Amphibia Characteristics

Extant Amphibia Families

Amphibian Fossil Record

1 What are Amphibians?

Ectothermic that have a biphasic life cycle consisting of anamniotic (often aquatic) and a terrestrial adult stage.

Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Amphibia (amphibios: “double life”) Subclass: Orders: •Anura () • () • ()

Amphibia Characteristics

1) Cutaneous Respiration

•Oxygen and CO2 Transfer (moist) •Family Plethodontidae (lungless salamanders) • (larvae, few adult salamanders), 2 Lungs (adults) Plethodon dorsalis

2) Skin Glands •Mucous Glands (cutaneous respiration, antibiotic properties) •Glanular Glands (toxic secretions - neurotoxins, alkaloids) ¾Paratoid Glands •Other glands (not in all ) •Nuptial •Wax

Amphibia Characteristics

3) Modifications of middle and inner ear • Middle ear consists of 2 elements •Stapes (columella) •Operculum

• Inner ear consists of 2 sensory epithelial patches •Papilla bassilaris (>1000 Hz) •Papilla amphibiorum (≤1000 Hz)

2 Amphibia Characteristics

4) Green Rods in Retina (excluding caecilians) •Involved in hue discrimination (433 nm = blue light) •Other Light Receptors: red rods, single and double cones

5) Focus by changing position of lens •Levator bulbi underlying the eye control elevation

6) Bicuspid Pedicellate Teeth •Crown (above gum), Pedicel (connected to jawbone) •New Crown Emerges from Pedicel

7) Reductions in bones •General trend associated with paedomorphosis (phenotypic change in which adults retain juvenile traits)

Modern Orders of Amphibia

•Gymnophiona (caecilians) 9% 3% ƒ 167 species Caudates Caecilians

88% Anurans

Ichthyophis kohtaoensis 280 Species in U.S. (86 Species in TN) •Caudata (salamanders)

•Anura (frogs) Dendrobates tinctorius ƒ 5,420 species

Plethodon shermani ƒ 559 species

Gymnophiona Characteristics: •Tropical Distribution •Limbless (pectoral & pelvic girdles absent) •Elongate and annulated bodies •Degenerate (covered with skin or bone) • (phallodeum) •Tentacle between eye and nostril •Left lung reduced or absent •6 Families •Some with dermal scales •Distinct •Stegokrotaphic versus Zygokrotaphic

3 Gymnophiona Families: 1) Caeciliidae (Common Caecilians) 2) ( Caecilians)

•95 species (57%) mexicanus •38 species (23%) •Primary Annuli •Primary Annuli w/ •Most Fossorial Secondary & Tertiary •True tail •No true tail •Stegokrotaphic Skull •Stegokrotaphic Skull •Females attend eggs kohtaoensis

3) Typhlonectidae (Aquatic Caecilians) 4) (Beaked Caecilians)

•14 species (8%) •9 species (5%) •Primary Annuli •Primary Annuli w/ •No true tail Secondary & Tertiary •Zygokrotaphic Skull Grooves •Strongly Aquatic indistinctum •True tail •Viviparous •Zygokrotaphic Skull

Gymnophiona Families:

5) (Tropical Caecilians) 6) Uraeotyphlidae (Indian Caecilians)

•6 species (4%) •5 species (3%) •Primary Annuli •Primary Annuli w/ •No true tail Secondary Grooves •Zygokrotaphic Skull •True tail •Calcified spines on •Stegokrotaphic Skull phallodea •Some are viviparous

Gymnophiona phylogeny

Beaked

Fish

Indian

Tropical

Common

Aquatic

4 Caudata Characteristics: •Tails and superficially segmented bodies •Mostly Temperate Distribution •Well-developed limbs (except aquatic) •Internal Fertilization (most) •Larval Development External (most) •Pheromones (mucous glands) •Lack Tympanum & Middle Ear Families: •10 Families 1) Plethodontidae (Lungless Salamanders) 2) Salamandridae (True Salamanders)

•378 species (68%) •74 species (13%)

•U.S. & Neo-tropics •U.S., , SE Asia QuickTime™ and a TIFF (Uncompressed) decompressor •Cutaneous respiration •Lungs are needed to see this picture. •Nasolabial groove •Skin toxic and brightly (chemoreception) colored •Reduced skull •Free-swimming larvae •Eggs usually guarded Plethodon shermani (most) Triturus cristatus

Caudata Families: 3) Hynobiidae (Asian Salamanders) 4) Ambystomatidae (Mole Salamanders) •51 species (9%) •32 species (6%) •Asia • •External fertilization •Highly Terrestrial (most) •Reduced lungs (some) •Primarily Winter Breeders •Aquatic courtship •Teeth are in patches Hynobius chinensis •Hydridization (J+BS) Ambystoma tigrinum 5) (Mudpuppies & Waterdogs) 6) Sirenidae (Sirens) •6 species (1%) •4 species (0.7%) •Eastern US & Europe •Southern US (Still water) •Obligate Paedomorphic •Obligate Paedomorphic •External Fertilization •Depressed body, external (lack spermathecae) gills •Lack pelvic girdles, eye •Necturus prefer crayfish lids, pedicellate teeth Necturus maculosus •Pre-maxillary beak Siren intermedia

Caudata Families: 7) Rhyacotritonidae(Torrent Salamanders) 8) Dicamptodontidae (Giant Salamanders) •4 species (0.7%) •4 species (0.7%) •Coastal Pacific NW •Coastal NW and Canada •Semi-aquatic •Large living terrestrial •No operculum or op. muscle salamanders (20 cm SVL) •Reduced Lungs •Vomerine Teeth (M) •Bright yellow abdomen Rhyacotriton kezeri •Larvae develop 2-5 yrs Dicamptodon ensatus 9) Amphiumidae () 10) Cryptobranchidae (Hellbenders)

•3 species (0.5%) •3 species (0.5%) •Eastern U.S. & China •SE •Obligate Paedomorphic •Obligate Paedomorphic •No external gills, slits •No external gills, gill slits •Excessive skin (respiration) •Spermatophore directly •External Fertilization deposited into spermatheca tridactylum •Lidless eyes, no tongue pad Cryptobranchus •Number of Toes alleganiensis

5 Caudata phylogeny

Movie

Anura Characteristics: •Shortened Presacral (usually 8) •Global Distribution Saltatorial • are reduced or absent (2nd or 4th) 2-10X BL •Presacral Vertebrae Firmly Articulated •Large Hind Limbs, No tail (except 1 family)

Video •External Fertilization (usually) •Flat heads and Large Mouths (usually) •Vocal Sacs in Males (usually) •29 Families Families: 1) (Southern Frogs) 2) (Tree Frogs)

•1283 species (24%) •835 species (15%) N •Neo-tropics & subtropics •Global Distribution •Male broods eggs •Toes disks •Foam nest •Good climbers, jumpers •, direct dev., or •Free swimming tadpoles viviparious Eleutherodactylus coqui (most) callidryas

Anura Families: 3) Ranidae (True Frogs) 4) Bufonidae (True ) •799 species (14.7%) •493 species (9%) •Global (Bufo most spp.) •Global (, Asia most) •Cutaneous Glands •Well-developed legs & •Teeth nearly absent webbed feet •Bidder’s Organ •Free swimming tadpoles Rudimentary Ovary on Testes (most) Rana catesbeiana Bufo cognatus 5) (Narrow-mouthed Frogs) 6) (Asian Tree Frogs)

•449 species (8%) •288 species (5%)

•Mostly Tropical, Sub- •Africa, , SE Asia tropical •Hanging Foam Nest •2-3 Palatal Folds •“Flying Frogs” •Breviceps Secretions • Convergent with hylids Stick to Female’s Back carolinensis reinwardtii

6 Anura Families: 7) (African Tree Frogs) 8) Dendrobatidae (Poison Arrow Frogs) •261 species (4.8%) •252 species (4.7%) •Central & •Africa, , Seychelles •Brightly colored, toxic skin •Pupil vertically elliptical •Most very small (<1 inch) •Toe disks; brightly colored •Males wrestle for dominance •Some fold leaves over eggs vermiculatus •Tadpoles ride on males back Dendrobates tinctorius

9) (Mantellas) 10) Centrolenidae (Glass Frogs)

•165 species (3%) •143 species (2.6%) •Madagascar only •Central & South America •Brightly colored, toxic skin •Transparent Skin (no ribs) •Most very small (<1 inch) •Most very small (<1 inch)

•Converged Evolutionarily with •Eggs guarded Dendrobatidae by males over madagascariensis stream Centrolene prosoblepon

Anura

Families: montana 11) (Cryptic Frogs) 12) (Water Frogs) •138 species (2.5%) •126 species (2.3%) M •Asia & (streams) •New Guinea, , and Tasmania •Leaf-like Appearance •Foam Nests in Water •Poor Jumpers •Unique brooding •Nocturnal •Tadpoles: Surface Foragers carinensis •Rheobatracus (extinct) dumerilii 13) (Squeakers) 14) (Tongueless Frogs) •51 species (0.9%) •31 species (0.6%) •Africa and South America •Sub-Saharan Africa •Fully Aquatic Frogs •Previously a part of Ranidae •Webbed feet, long fingers •Direct development (some with keratinized tips tadpoles) M •Eyes dorsal and no tongue aureoli laevis

Anura Families: 15) Astylosternidae (Astylosternids) 16) Discoglossidae (Disc-tongued frogs) •29 species (0.5%) •12 species (0.2%) A •Sub-Saharan Africa •Northern Africa, SW Europe •Often combined with #13 •Male carries eggs on hind legs •Differ from #13: horizontal •Females vocalize some pupils & toe discs •-like (terrestrial & life •Hairy Trichobatrachus robustus in burrows) Alytes obstetricans 17) Pelobatidae (Spadefoots) 18) (Pumpkin Toads)

•11 species (0.2%) •11 species (0.2%) •SE Brazil •United States, , Europe and Eastern Asia •All direct development •Xeric environments •Reduced digits •Most bright orange •Explosive breeding M •B. didactylus: smallest Scaphiopus couchii •Fast developing larvae in southern Brachycephalus ephippium (cannibalistic phenotype) Hemisphere (3/8”)

7 Anura Families: (Fire-bellied Toads (Shovel-nosed frogs) 19) & Barbourulas) 20) Hemisotidae •10 species (0.2%) •9 species (0.17%) A •Europe; East Asia •Sub-Saharan Africa •Burrows head first •Toxic Skin (unken reflex) •Lay eggs in burrow •Barbourulas: Rocky streams •Females dig ditch or Bombina orientalis transport tadpoles Hemisus marmoratus 21) Heleophrynidae (Ghost Frogs) 22) (Seychelles Frogs) •6 species (0.1%) •29 species (0.5%) •Southern Africa •Madagascar •Fast-flowing streams •Inguinal (only Neobatrachid ) •Well-developed toe discs, spines, sucker-like oral disc •Secretive: litter and rocks (tadpoles) •Direct development & pipilodryas • Gorge: Cape Town Heleophryne regis tadpoles on back

Anura Families: 23) Leiopelmatidae (Leiopelmatids) 24) (Parsley Frogs) •4 species (0.1%) •3 species (0.1%) A •Black & Caspian M •New Zealand Seas, S. Europe •Primitive group •Bulging Eyes; Parsley •Do not call (no T, ME, VS) Color •Inscriptional ribs •Females reported Pelodytes punctatus archeyi vocalizing when amplexed (Mouth-brooding 25) Ascaphidae (Tailed Frogs) 26) Frogs) •2 species (<0.1%) •2 species (<0.1%) •Southern South •NW United States, A M British Columbia America (Chile) •Fast moving streams •Tadpoles Develop in •Tail: Cloacal Extension Vocal Sac (male) •Internal fertilization •“Rhinoceros nosed” •Most primitive extant family Ascaphus montanus darwinii (don’t call, 7 yrs to maturation)

Anura Families: 27) Allophrynidae (Ruthven’s Frog) 28) Nasikabatrachidae () •1 species (<0.1%) •1 species (<0.1%) •NE South America •India (discovered 2003) •Centrolenidae (related?; •Fossorial foot muscle morphology) •Explosive breeders •Little known about its •Little known ecology Allophryne ruthveni sahyadrensis 29) ()

•1 species (<0.1%) •Costa Rica to Rio Grande •Fossorial •Explosive breeders • and specialists M •No teeth Rhinophrynus dorsalis

8 Anura Phylogeny

Evolutionary history of Amphibians

Events in Geologic History

Fish to Tetrapods

Tetrapods to Amphibians

Fossil Record of Amphibians

Modern Amphibians (late ) 250 MYA

Carboniferous First Amphibians Mississippian 350 MYA

9 Evolutionary transitions First tetrapods appeared in the (400 MYA) Tropical/subtropical latitudes Primitive plants and arthropods

Pangaea

Why did fish emerge on land? 1. Find food or evade predators 2. Low oxygen levels 3. Periodic droughts

Fish to Tetrapods Sarcopterygian (lobe-finned ) -Pelagic -Long snout -Internal nostrils -Dorsal eyes -Distinct , ulna, and radius and -Reduced median fins , tibia, and fibula

Tiktaalik -More developed limbs with wrist and finger bones (body postures) -Robust cage -Lungs and gills -Neck separated from body

Fish to Tetrapods Greenland Acanthostega

1 m 0.6 m

•Piscivorous •Piscivorous •Limbs likely used •Fish-like for navigating •Limbs likely used •Tail for balance for paddling •Skeletal structure •Skeletal structure ¾forelimbs ¾Elbow could not bend •Lungs •Gills and Lungs

•8 digits

10 Fish to Tetrapods

Evolutionary Gap

30 million year gap in the fossil record for tetrapods

Relationships between Devonian and tetrapods obscured

Temnospondylous Amphibians Carboniferous and Permian Periods •1.5-2 m long •Bicuspid pedicellate teeth

•Lungs & Cutaneous Respiration •Likely piscivorous

•Engulfed prey megacephalus •Not a strong swimmer or fast tetrapod (likely hunted by stealth or opportunity)

•Shoulder disconnected from skull

11 Lepospondylous Amphibians Carboniferous and Permian Periods Nectridia •Mostly Aquatic •Resembled (flat tails) •“Small Lizard” •Terrestrial and fossorial •Some with triangular heads

•Small fish and aquatic

0.5-1 m No larval forms known •Elongate body •Diminutive limbs •Fenestrated skulls

Phylogenetic Hypotheses

(Zardoya and Meyer 2001, Laurin 2002)

Fossil Record of Lissamphibia Probably Triassic, and Periods for All Orders 2) Salamanders 1) Anurans 3) Caecilians Video Paleobatrachus

14 massinoti Karuaus sharovi Apodops pricei •Origin: Madagascar •Origin: Kazakstan •Origin: Gondwanaland (SA) • (230 mya) • (170 mya) •Late Cretaceous (100 mya)

12 Historical Biogeography

Alfred Wegener Continental drift

Historical Biogeography

Continental drift and Caecilians

Lecture summary

General characteristics of amphibians

Characteristics of extant amphibian orders

Diversity of extant amphibian orders

Evolutionary history of amphibians

13