Amphibian and Reptiles

Phylum Chordata Amphibians and reptiles share the same developmental characteristics as other chordates Gill slits Dorsal nerve cord Notochord or vertebral column

Transitional Organisms Amphibians and reptiles act as a transitional form between aquatic and land organisms Many of the characteristics of mammals and other land organisms begin to be seen in these types of organisms.

Comparison of Vertebrate “Class” Traits Class TetrapodEgg typeDevelopment Agnatha/Chondricthyes/ Osteichthyes NoAnamnioticIndirect (larva to adult) AmphibiaYesAnamnioticIndirect ReptiliaYesAmnioticDirect (juvenile to adult) MammalsYesAmnioticDirect

Leg development Legs are developed for the first time forming what is called the tetrapod (four appendages) body plan, allowing organisms to escape predators by walking on land.

Anamniotic egg Jellylike (unshelled; must develop in water) Small-sized (lack large membranes to nourish embryo and store waste) Amphibian egg mass

Amniote Egg Embryonic membranes Large egg Shell (absent in livebearers)

Comparison of Vertebrate “Class” Traits (continued) Class RespirationBody temperature regulation Body covering Agnatha/Chondricthyes/ Osteichthyes GillsEctothermyScales AmphibiaGills, lungsEctothermySkin (smooth or warty) ReptiliaLungsEctothermyScales MammalsLungsEndothermyHair

1 st amphibians 1 st reptiles 1 st Homo sapiens Amphibians and Reptiles evolved around the same time and far before the appearance of mammals.

Evolutionary Relationships Amphibia Amniota Anapsida Diapsida Testudines (turtles) Mammalia Aves and other Dinosauria Squamata (snakes, lizards) Sphenodonta Crocodylia Synapsida Osteichthyes

1 st Amphibians (Devonian Period; mya) Eusthenopteron (a sarcopterygian fish) could be the ancestor of amphibians) Krohne (2000) Amphibians are thought to have evolved from lobe finned fish

1 st Amphibians (Devonian Period; mya) Acanthostega (a sarcopterygian fish) could be the ancestor of amphibians

Modern Amphibians CaudataAnura

Evolutionary Relationships Amphibia Amniota Anapsida Diapsida Testudines (turtles) Mammalia Aves and other Dinosauria Squamata (snakes, lizards) Sphenodonta Crocodylia Synapsida Osteichthyes

Reptile lineages (based on temporal openings in skull) Anapsida: turtles Diapsida: dinosaurs, birds, snakes, lizards Synapsida: mammals

1 st Reptiles (Pennsylvanian Period; mya) Hylonomus (oldest known reptile; 30 cm long) Seymouria (amphibian or reptile?) Forey (1988) ?

Modern Reptiles Order Testudines (turtles) Order Squamata (lizards, snakes)

Prairie wetland ecosystem Wetland Ecosystems will have a combination of reptiles and amphibians

Upland prairie ecosystem Most prairies or dry ecosystems will only contain reptiles