sign in sign up
<<
Home , Afrixalus, Arthroleptis, Atelopus cruciger, Bolitoglossa, Boulengerula, Boulengerula boulengeri

The diversity and evolution of Amphibia: What are they and where did they come from?

Lecture goal

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

Reading assignments: Wells: pp. 1-15, 41-58, 65-74, 77-80

Supplemental readings on taxa: Wells: pp. 16-41, 59-65, 75-77

Lecture roadmap

Characteristics of amphibians

Extant amphibian orders

Characteristics of amphibian orders and diversity

Amphibian fossil record and evolution

1 What are amphibians?

These foul and loathsome are abhorrent because of their cold body, pale color, cartilaginous skeleton, filthy , fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terrible venom; and so their Creator has not exerted his powers to make many of them.

Carl von Linne (Linnaeus) Systema Naturae (1758)

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: Lissamphibia Orders: •Anura () • () • ()

Amphibia characteristics

1) Cutaneous

Oxygen and CO2 Transfer Family Plethodon dorsalis (larvae, few adult salamanders), 2 (adults)

2) Skin glands Mucous glands Granular glands

2 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)

Amphibia characteristics

4) Green rods in retina (excluding caecilians) Involved in hue discrimination (433 nm = blue light)

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

6) Bicuspid pedicellate teeth Crown (above gum), Pedicel (connected to jawbone)

7) Reductions in skull bones

General trend associated with paedomorphosis

Modern Orders of Amphibia

1. Gymnophiona (caecilians) 9% 3% . 176 Caudates Caecilians

88% Anurans

Ichthyophis kohtaoensis 280 Species in U.S. 2. Caudata (salamanders) (86 Species in TN) . 576 species

3. Anura (frogs) Dendrobates tinctorius . 5,695 species

Plethodon shermani

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

Caecilian families

1) Caeciliidae (Common Caecilians)

•95 species (57%) •Primary Annuli fischeri •Most Fossorial •No true tail •Stegokrotaphic skull Gegeneophis danieli •Can reach 5 ft in length

Dermophis mexicanus Gegeneophis mhadeiensis

Caecilian families

2) ( Caecilians)

•38 species (23%) •Primary annuli with secondary & tertiary annuli •True tail •Females attend eggs •Stegokrotaphic skull •Primitive family

Ichthyophis kohtaoensis Ichthyophis kohtaoensis

4 Caecilian families

3) (Aquatic Caecilians)

•14 species (8%) compressicauda •Primary annuli •No true tail •Strongly aquatic •Zygokrotaphic skull •Viviparous

Chthonerpeton indistinctum

Chthonerpeton indistinctum

Caecilian families

4) (Beaked Caecilians)

•9 species (5%) •Primary annuli with secondary & tertiary annuli •True tail •Oviparous •Zygokrotaphic skull •Primitive family

Rhinatrema bivittatum bicolor

Epicrionops bicolor

Caecilian families

5) Scolecomorphidae (Tropical Caecilians) •6 species (4%) •Primary annuli Scolecomorphus vittatus •No true tail •Some are viviparous •Zygokrotaphic skull •Calcified spines on phallodea

6) Uraeotyphlidae (Indian Caecilians) •5 species (3%) •Primary annuli with secondary annuli •True tail •Stegokrotaphic skull Uraeotyphlus

5 Caecilian phylogeny

Primitive

Rhinatrematidae

Ichthyophidae 4 Uraeotyphlidae

Scolecomorphidae

1 2 3 4 Caecilidae

Loss of tail Loss of secondary annuli Typhlonectidae Viviparous/Direct Development Stegokrotaphic skull Derived

Caecilian morphology and ecology

Some other topics to explore on your own

1. Modes of locomotion

2. Burrowing

3. Sensory systems

Caudata (Salamanders) Characteristics: Mostly Temperate Distribution •Tails and superficially segmented bodies •Well-developed limbs (except aquatic) •Internal fertilization (most) •Larval development external (most)

•Pheromones (mucous glands) 10 Families •Lack tympanum & middle ear •Regenerate lost limbs

6 families

Thorius papaloae 1) Plethodontidae (Lungless salamanders)

•378 species (68%) •Found in the US and New World Tropics •Cutaneous respiration bellii •Nasolabial groove (chemoreception) •Reduced skull •Eggs usually guarded Movie

Hydromantes supramontis adspersa gracilis

Salamander families shanjing

2) (True salamanders)

•74 species (13%) •Found in the US and SE Asia •Lungs •Toxic skin with bright coloration •Free-swimming larvae in most species

Neurergus kaiseri

Neurergus crocatus Triturus pygmaeus Triturus dobrogicus

Hynobius tsuensis Salamander families

3) Hynobiidae (Asian salamanders) Batrachuperus pinchonii •51 species (9%) •Found in Asia •External fertilization •Reduced lungs in most species •Teeth are in patches

Salamandrella keyserlingii Ranodon sibiricus Onychodactylus japonicus

Pachyhynobius shangchengensis

7 Salamander families

4) Ambystomatidae (Mole salamanders) Ambystoma mavortium

•32 species (6%) •Found in North America •Highly terrestrial adults •Primarily winter and spring breeders

•Aquatic courtship Ambystoma cingulatum •Hybridization common Specimen (Jefferson’s and Blue-Spotted)

Ambystoma annulatum Ambystoma jeffersonianum

Ambystoma opacum

Salamander families 5) Proteidae (Mudpuppies and Waterdogs) •6 species (1%) •Found in eastern US and Europe •Obligate paedomorphs Necturus maculosus •Depressed body and external gills •Cave dwelling species Proteus anguinus

6) Sirenidae (Sirens) Siren intermedia intermedia •4 species (0.7%) •Found in southern US (still water) •Obligate paedomorphs •External gills •External fertilization (lack spermatheca) •Lack pelvic girdles, eye lids, and pedicellate teeth

•Pre-maxillary beak Pseudobranchus striatus

Salamander families

7) Rhyacotritonidae (Torrent Salamanders) •4 species (0.7%) •Found in costal NW US Rhyacotriton variegatus •Semi-aquatic •No operculum or opercular muscle •Reduced lungs Rhyacotriton kezeri •Bright yellow abdomen

8) Dicamptodontidae (Giant Salamanders) •4 species (0.7%)

•Found in costal NW US and Canada Dicamptodon ensatus •Large terrestrial salamander (20 cm SVL) •Vomerine teeth (shape of M) •Larvae develop for 2-5 years

Dicamptodon aterrimus

8 Salamander families Amphiuma tridactylum 9) Amphiumidae (Amphiumas) •3 species (0.5%) Amphiuma means •Found in SE US •Obligate paedomorphs •No external gills or slits •Spermatophore directly deposited into spermatheca •Toe number used for species ID

10) Cryptobranchidae (Hellbenders) •3 species (0.5%) •Found in eastern US, China & Japan •Obligate paedomorphs •No external gills, excessive skin folds •External fertilization •No eye lids or tongue pad Andrias japonicus

Salamander phylogeny

Plethodontidae Derived

Amphiumidae Rhyacotritonidae

Ambystomatidae Dicamptodontidae

Salamandridae

Proteidae Sirenidae

Hynobiidae

Cryptobranchidae Primitive

Salamander morphology and ecology

Some other topics to explore on your own

1. Adaptations

2. Paedomorphosis

3. Evolution of lunglessness

9 Anura (Frogs and ) Characteristics:

•Shortened presacral vertebrate (usually 8)

•Ribs are reduced or absent (2nd or 4th) Saltatorial Video •Presacral vertebrae firmly articulated 2-10X BL •Large hind limbs, no tail (except 1 family) •External fertilization (usually) •Flat heads and large mouths (usually)

•Vocal sacs in males (usually) Global Distribution

29 Families

Anuran families

1) (Southern Frogs) Eleutherodactylus coqui

•1283 species (24%) •Found in the New World Tropics •Males brood eggs •Foam nests •Varied life history (tadpoles, direct dev., viviparous)

•Eggs usually guarded thaul

Leptodactylus mystacinus

Telmatobius culeus

Ceratophrys ornata Lithodytes lineatus

Anuran families

2) (Tree Frogs)

•835 species (15%) •Global distribution •Toe discs Anotheca spinosa •Good climbers and jumpers •Free swimming tadpoles (most)

Dendropsophus berthalutzae garbei Pachymedusa dacnicolor Cruziohyla calcarifer Hylomantis lemur

Triprion petasatus

10 Anuran families

3) Ranidae (True Frogs)

•799 species (14.7%) •Global distribution (Africa and Asia most)

•Well-developed legs and webbed feet Pyxicephalus adspersus •Free swimming tadpoles (most) saxicola Platymantis vitiensis

Rana warszewitschii

Ceratobatrachus guentheri

Staurois natator Tomopterna tuberculosa

Anuran families

4) Bufonidae (True )

•493 species (9%) •Global distribution Nectophrynoides asperginis •Cutaneous glands

•Teeth nearly absent Melanophryniscus stelzneri •Bidder’s organ

Bufo superciliaris

Crepidophryne chompipe Pedostibes hosii cruciger

Anuran families

Phrynomantis bifasciatus 5) (Narrow-mouthed Frogs)

•449 species (8%) •Mostly tropical and subtropical •2-3 palatal folds •Stout hind legs, short snouts, and globose bodies •Breviceps - males produce secretions to stick to females

Relictivomer pearsei

Scaphiophryne madagascariensis Rhombophryne testudo

Myersiella microps

11 Anuran families

6) (Asian Tree Frogs)

•288 species (5%) pictus •Africa, , SE Asia •Hanging foam nests •“Flying Frogs” •Flash coloration on inner thigh Specimen

Rhacophorus reinwardtii

Theloderma corticale otilophus

Polypedates cruciger

Anuran families

7) (African Tree Frogs)

•261 species (4.8%) •Africa, Madagascar, Seychelles vermiculatus •Pupil vertically elliptical •Toe discs •Brightly colored

Hyperolius marmoratus

Heterixalus tricolor Kassina kuvangensis

Afrixalus fornasini

Anuran families

8) Dendrobatidae (Poison Arrow Frogs) •252 species (4.7%) •Found in Central and South America Dendrobates tinctorius

•Brightly colored and toxic skin Dendrobates imitator •Most very small (<1 inch) •Males wrestle for dominance Video •Tadpole ride on males back

Laliostoma labrosum 9) (Mantellas) Mantella madagascariensis •164 species (3%) •Madagascar only •Brightly colored and toxic skin •Most very small (<1 inch) •Some convergent with Dendrobatidae

Tsingymantis antitra

12 Anuran families

10) Centrolenidae (Glass Frogs) •143 species (2.3%)

•Central and South America Cochranella spinosa buckleyi •Transparent skin, no ribs •Most very small (<1 inch) •Males guard eggs

Centrolene ilex

11) (Cryptic Frogs) •138 species (2.5%) •Asia & (streams) Brachytarsophrys carinensis •Leaf-like appearence •Nocturnal and poor jumpers •Tadpoles feed at surface

Megophrys nasuta Brachytarsophrys intermedia

Anuran families Lechriodus fletcheri 12) Myobratrachidae (Water Frogs) •126 species (2.3%) •New Guinea, Australia, & Tasmania •Foam nests in water Limnodynastes dumerilii •Unique brooding (pouch, mouth) •Lack toe discs •Rheobatrachus (extinct)

13) (Squeakers) •51 species (0.9%)

•Sub-Saharan Africa () Arthroleptis reichei •Direct development (some tadpoles)

Cardioglossa gracilis Cardioglossa aureoli

Anuran families

14) (Tongueless Frogs) •31 species (0.6%) •Africa & South America Pipa parva •Fully aquatic (webbed feet, lateral line system) •Pipa (eggs embedded on female) •Xenopus (tadpoles with barbs)

•Eyes dorsal and no tongue Xenopus laevis Xenopus muelleri 15) Astylosternidae (Astylosternids) Leptopelis kivuensis •29 species (0.5%) •Sub-Saharan Africa (forests) •Often grouped with Arthrolepidae •Toe discs •Hairy projections •“Claws” Trichobatrachus robustus

13 Anuran families 16) Discoglossidae (Disc-tongued Frogs) 17) Pelobatidae (Spadefoots)

•12 species (0.2%) •11 species (0.2%) •SW Europe; Northern Africa •US, , Europe, Eastern Asia •Females vocalize some •Xeric environments Alytes cisternasii •Toad-like •Explosive breeders •Fast developing larvae •Terrestrial and life in burrows (cannibalistic larvae)

Pelobates cultripes

Discoglossus sardus 18) (Pumpkin Toads) •11 species (0.2%) •SE •All direct development •Reduced digits Brachycephalus ephippium •Bright orange (tetrodotoxin) •B. didactylus: smallest in Brachycephalus nodoterga southern hemisphere (3/8”)

Anuran families 19) 20) Hemisotidae (Shovel-nosed Frogs) (Fire-bellied Toads & Barbourulas) •9 species (0.17%) •10 species (0.2%) •Sub-Saharan Africa •Europe; East Asia •Burrows head first •Toxic Skin (unken reflex) •Lay eggs in burrow Hemisus marmoratus •Barbourulas: Rocky •Females dig ditch or transport tadpoles streams Bombina orientalis

21) Heleophrynidae (Ghost Frogs) 22) (Seychelles Frogs) •6 species (0.1%) •29 species (0.5%) •Southern Africa •Madagascar •Well-developed toe discs, spines, sucker- •Inguinal amplexus (only Neobatrachid ) like oral disc (tadpoles) •Secretive: litter and rocks •Fast-flowing streams •Direct development & tadpoles on back

Heleophryne regis Sooglossus pipilodryas

Anuran families 23) Leiopelmatidae (Leiopelmatids) 24) Pelodytidae (Parsley Frogs)

•4 species (0.1%) •3 species (0.1%) •New Zealand •Black & Caspian Seas, S. Europe •Primitive group •Bulging Eyes; Parsley Color •Do not call (no T, ME, VS) •Females reported vocalizing when amplexed •Inscriptional ribs archeyi

Pelodytes punctatus 25) Ascaphidae (Tailed frogs) 26) Rhinodermatidae (Mouth-brooding frogs)

•2 species (<0.1%) •2 species (<0.1%) •NW US, British Columbia •Southern South America (Chile) •Fast moving streams •Tadpoles Develop in Vocal Sac (male) •Tail: Cloacal Extension •“Rhinoceros nosed” •Internal fertilization Ascaphus montanus •Most primitive extant family darwinii (don’t call, 7 yrs to maturation)

14 Anuran families

27) Allophrynidae 28) Nasikabatrachidae

•1 species (<0.1%) •1 species (<0.1%) (Purple Frog) •NE South America •India (discovered 2003) •Centrolenidae (related?; foot muscle morphology) •Fossorial •Explosive breeders •Little known about its ecology •Little known Allophryne ruthveni

(Ruthven’s ) Nasikabatrachus sahyadrensis

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

Anuran phylogeny Primitive Derived

Anuran morphology and ecology

Some other topics to explore on your own

1. associations of adult anurans

2. Body size and ecology of adult anurans

3. Adaptations for different life styles

15 Evolutionary history of Amphibia

Events in Geologic History

Fish to Tetrapods

Tetrapods to Amphibians

Geologic history

Alfred Wegener Continental drift

Events in geologic history

Modern Amphibians (late ) 250 MYA

Carboniferous First Amphibians (Mississippian) 350 MYA

16 Ecological history

First tetrapods appeared in the (400 MYA) What were the conditions at this time? • Tropical/subtropical latitudes - relatively warm and stable • Primitive plants and

Pangaea

Fish to tetrapod transition

Sarcopterygian (lobe-finned )

Eusthenopteron Tiktaalik -Pelagic -More developed limbs with wrist and finger bones (body postures) -Internal nostrils -Robust rib cage -Distinct humerus, ulna, and radius and femur, tibia, and fibula -Lungs and gills -Neck separated from body Panderichthys -Long snout -Dorsal eyes -Reduced median fins -Flattened bodies

Fish to tetrapod transition Greenland Ichthyostega Acanthostega

1 m 0.6 m

•Piscivorous •Piscivorous

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

•8 digits

17 Fish to tetrapod transition

Evolutionary gap

30 million year gap in the fossil record for tetrapods

Relationships between Devonian and tetrapods obscured

Age of amphibians

Carboniferous (360-300 MYA)

Many species were large and protected by armor (diversity in form and habitat)

Probably lacked cutaneous respiration but well developed lungs

Retained aquatic reproduction

Pangaea starting to split apart

Amphibian lineage split from lineage 360 MYA

18 Temnospondylous amphibians

•1.5-2 m long •Bicuspid pedicellate teeth •Lungs & Cutaneous Respiration •Likely piscivorous •Engulfed prey •Not a strong swimmer or fast tetrapod (likely hunted by stealth or opportunity) •Shoulder disconnected from skull

Eryops megacephalus

Lepospondylous amphibians

Nectridia •Mostly aquatic Microsauria •Resembled (flat tails) •“Small Lizard” •Terrestrial and fossorial •Some with triangular heads

•Small fish and aquatic invertebrates

0.5-1 m

No larval forms known Lysorophia •Elongate body •Diminutive limbs

•Fenestrated skulls

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

Paleobatrachus

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

19 Lecture summary

General characteristics of amphibians

Characteristics of extant amphibian orders

Diversity of extant amphibian orders

Evolutionary history of amphibians

20