early mesozoic era - university of northern...
TRANSCRIPT
Earth History, Ch. 16 1
Early Mesozoic Era
Jurassic
System
Triassic
System
Late
Early
Early
Middle
Middle
Late
142
206
251
Jurassic System named
in early 1900’s for classic
exposures in the Alps.
Triassic System named
in 1834 by von Alberti
in Germany. Triassic is
bounded by mass extinc-
tions above and below.
Earth History, Ch. 16 2
Today’s outline
• Life in the Early Mesozoic (aftermath of the
end-Permian mass extinction)
– Marine realm
• Benthic life forms
• Pelagic life forms
– Terrestrial realm
• Plants
• Animals
Earth History, Ch. 16 3
Early Mesozoic marine life
• End-Permian mass extinction wiped out:
– Corals, fusulinids, blastoids, trilobites, most crinoids,
most brachiopods, most bryozoans
• Paleozoic invertebrate faunas were dominated by
sessile, filter-feeding organisms
• End-Permian mass extinction caused a complete
reorganization of marine communities
Earth History, Ch. 16 4
Early Mesozoic marine life
• Earliest Mesozoic marine realm was
dominated by mobile, predatory mollusks
– Ammonoids (radiated from 1 to 100 genera in
early Triassic)
– Bivalves
– Gastropods
Earth History, Ch. 16 5
Sepkoski’s three faunas
(marine invertebrate world)
Earth History, Ch. 16 6
Earth History, Ch. 16 7
Earth History, Ch. 16 8
Earth History, Ch. 16 9
Early Mesozoic marine life
• Reef communities were decimated by the end-Permian mass extinction
• No reefs in early Triassic
• Middle Triassic reefs resembled late Permian ones (sponges, algae)
• New coral reefs (hexacorals) appeared in middle Triassic (small, deep-water reefs)
• By late Triassic, large, shallow water reef structures were forming
Earth History, Ch. 16 10
Triassic hexacorals
Hexacorals probably are not
related to Paleozoic corals,
but evolved indepently from
sea anemonies.
Explosive adaptive radiation
started in late Triassic time.
Earth History, Ch. 16 11
Hexacoral
radiation
Note: No early
Triassic corals
Earth History, Ch. 16 12
Early Mesozoic marine realm
• Planktonic microrganisms diversified in Jurassic time
– Dinoflagellates (algae)
– Calcareous nannoplankton (coccoliths)
• Swimming organisms rebounded
– Ammonoids, belemnoids (fossil cigars)
– Conodonts (became extinct at end-Triassic)
– Bony fishes and sharks
Earth History, Ch. 16 13
Pelagic organisms
Calcareous
nannoplankton
Ammonoids and belemnoid
Earth History, Ch. 16 14
Early Mesozoic marine realm
• Swimming reptiles (a curious return to aquatic habitats) diversified in Triassic time
– Nothosaurs (early Triassic, seal-like)
– Placodonts (turtle-like)
– Plesiosaurs (middle Triassic, giant, up to 40 feet long)
– Ichthyosaurs (dolphin-like)
– Crocodiles
Earth History, Ch. 16 15
Nothosaur
Earth History, Ch. 16 16
Placodont
Earth History, Ch. 16 17
Plesiosaurs
Earth History, Ch. 16 18
Ichthyosaur
Earth History, Ch. 16 19
Early Mesozoic terrestrial realm
• Triassic flora was dominated by ferns and seed ferns
• Early Mesozoic trees were dominantly gymnosperms
– Cycads
– Cycadeoids
– Conifers
– Ginkos
Earth History, Ch. 16 20
Early Mesozoic gymnosperms
modern Ginko leaf Jurassic Ginko leaves
Earth History, Ch. 16 21
Cycadeoid (palm-like fern)
Earth History, Ch. 16 22
Early Mesozoic terrestrial
animals
• Therapsids (mammal-like reptiles) barely
survived end-Permian mass extinction
– Then gave rise to true mammals in late
Triassic time
• Earliest mammals were small and
inconspicuous
– No larger than a house cat
Earth History, Ch. 16 23
Origin of the dinosaurs
• Thecodonts were small early Triassic
reptiles that gave rise to earliest dinosaurs
• Early dinosaurs were small, but by end of
Triassic some reached up to 20 feet in
length
• By early Jurassic time, many kinds of huge
dinosaurs existed
Earth History, Ch. 16 24
Thecodonts and early mammal
Earth History, Ch. 16 25
Allosaurus
(Jurassic)
Earth History, Ch. 16 26
Dinosaur phylogeny
thecodont
Earth History, Ch. 16 27
Origin of the
dinosaurs
thecodonts
Bird-hipped dinosaurs
were all herbivorous
Reptile-hipped dinosaurs
were both herbivorous
and carnivorous
Earth History, Ch. 16 28
Dinosaur pelvises
Saurischian pelvis Ornithischian pelvis
Earth History, Ch. 16 29
Jurassic dinosaurs
• Morrison Formation (extends from
Montana to New Mexico) has best
assemblage of Jurassic dinosaurs in world
• Dinosaur collecting wars
– Cope vs. Marsh feud
– Gun battles and railroad cars full of bones!!
Earth History, Ch. 16 30
Earliest Flight
• Pterosaurs (late
Triassic reptiles)
were earliest flying
animals
• Probably clumsy
upon take-off and
landing, but well
suited for soaring
through the air
Earth History, Ch. 16 31
Earliest birds
• First true birds
appeared in late
Jurassic time
(evolved from
saurischian
dinosaurs)
• Last of the
vertebrate classes
to originate
Earth History, Ch. 16 32
Archaeopteryx from Solnhofen
Limestone (Germany)