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Dinosaurian turnover events



With regards to a previous posting on extinctions during the Mesozoic:

A better way to look at dinosaurian history is "turnover" events, which
includes both extinction of old forms and origination of new forms.  Below
is a general view of dinosaurian turnover events, from oldest to youngest:

Late Triassic:  appearance of Eoraptor, Herrerasauridae, Coelophysoid
ceratosuars, prosauropods, basal ornithischians (Pisanosaurus)

Triassic-Jurassic boundary: extinction of herrerasaurids (& many
nondinosaurian forms)

Early Jurassic: appearance of Heterodontosaurids, new forms of
coelophysoids and prosauropods, ?first sauropods?, first Thyreophorans
(armored dinosaurs)

Early-Middle Jurassic boundary: extinction of prosauropods, coelophysoids,
heterodontosaurids

Middle Jurassic: first Megalosauridae, Allosauridae, Coelurosauria, diverse
sauropod groups, first stegosaurians, ankylosaurians, hypsilophodontids

Middle-Late Jurassic boundary: no apparent extinction above the
species/genus levels

Late Jurassic: first Maniraptora (incl. Archaeopteryx), many groups
flourishing (Ceratosauridae, Megalosauridae, Sinraptoridae, Allosauridae,
Cetiosauridae, Brachiosauridae, Camarasauridae, Euhelopidae, Diplodocidae,
Dicraeosauridae, Stegosauridae, Polacanthidae, Hypsilophodontidae,
Iguanodontia (Dryosaurus, Camptosaurus)), first Titanosauria, possible
first Troodontidae, Tyrannosauridae?

Jurassic-Cretaceous boundary: extinction of Ceratosauridae, Megalosauridae,
Sinraptoridae, some extinction above the generic but below the family level

early Early Cretaceous (known primarily from Europe, U.S., South America):
first Ornithomimosauria, Dromaeosauridae, flourishing Allosauridae,
Titanosauridae, Andesauridae, Brachiosauridae, Camarasauridae,
Dicraeosauridae, Polocanthidae, Nodosauridae, Hypsilophodontidae,
Iguanodontia (Iguanodon), earliest Marginocephalia (Stenopleix).

early Early - middle Cretaceous boundary: no extinction above the generic
level

middle Cretaceous: first definite Abelisauridae, Troodontidae,
Ankylosauridae, Psittacosauridae, pesistance of early Early Cretaceous
lineages (at different relative abundance than before)

middle-late Late Cretaceous boundary: extinction of Allosauridae, maybe
Andesauridae, Polacanthidae, Psittacosauridae, non-hadrosaurid Iguanodontia

late Late Cretaceous: appearence of Oviraptorosauria, Tyrannosauridae,
Elmisauridae, Hadrosauridae, Pachycephalosauria, Neoceratopsia (and various
subdivisions thereof).

Cretaceous-Tertiary boundary: extinction of all non-avian dinosaurs

Of course, there are subtle changes within each time period (especially
during the last 12 million years of the late Late Cretaceous, where various
subfamilies within each major group die off before the others), as well as
differences between regions.
                                     
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092

email:  tholtz@geochange.er.usgs.gov 
Phone:  703-648-5280
FAX:            703-648-5420