Chapter 5 Outline
HISTORY OF DINOSAURIA
- SIR RICHARD OWEN
- CREATED "DINOSAURIA" IN 1842 TO ENCOMPASS A GROUP OF EXCEEDINGLY
LARGE, PACHYDERMOUS REPTILES FROM THE SECONDARY AGE (MESOZOIC ERA)
- Iguanodon , Megalosaurus & Hylaeosaurus
were the first members
- DINOSAURS THE MESOZOIC UNNATURALS
- H. G. SEELEY CONCLUDED IN 1887 THAT DINOSAURIA WAS NOT MONOPHYLETIC
- Saurischian (lizard hipped) dinosaurs had a separate
origin among the "Thecodontia" from Ornithischian
(bird hipped) dinosaurs according to Seeley
- F. VON HUENE CONTINUED & EMBELLISHED SEELEY'S CONCEPT INTO THE
1960'S
- Among saurischians, sauropods and theropods had separate
origins, and among ornithischians, ankylosaurs and other
ornithischians had separate origins, among the "Thecodontia"
according to von Huene
- A. J. CHARIG CARRIED ON VON HUENE'S IDEAS INTO THE 1970'S
- DINOSAURIA IT'S A NATURAL
- ROBERT T. BAKKER AND P. M. GALTON IN 1974 RESURRECTED DINOSAURIA AS
A MONOPHYLETIC TAXON, AND INCLUDED BIRDS WITHIN DINOSAURIA
- Met with great resistance, as did speculation by J. F. Bonaparte
in 1976 that Dinosauria is a clade
- CLADISTIC ANALYSIS OF ARCHOSAURIA COMMENCED IN 1984 ALONG 4 RESEARCH
FRONTS
- Disbanding of "Thecodontia"
- Origin of Dinosaurs
- Relationships within Saurischia and Ornithischia
- Relationship of Birds to Dinosaurs
- J. A. GAUTHIER IDENTIFIED MORE THAN 10 DERIVED FEATURES THAT ESTABLISHED
THE CLADE DINOSAURIA (SEE FIGS. 5.4 AND 5.5) IN 1986
- Herrerasaurus and Staurikosaurus are
the most basal dinosaurs, but not members of Saurischia or Ornithischia
according to Gauthier
- Herrerasaurus and Staurikosaurus , plus
Eoraptor ( a new dinosaur) are members
of Saurischia and are Theropods according to newer research by Paul
C. Sereno & co-workers
- DINOSAURIA IS A WELL-SUPPORTED MONOPHYLETIC CLADE ACCORDING TO DINOSAUR
PALEONTOLOGISTS NOW
ORIGINS
- CLOSEST ARCHOSAURIAN RELATIVES
- ACCORDING TO GAUTHIER AND KEVIN PADIAN = PTEROSAURIA
- Pterosauria + Dinosauria = Ornithodira
- Ornithodira + Lagosuchus = Ornithosuchia
- LAGOSUCHUS = SMALL (<1 M), LONG-LEGGED BIPEDAL CARNIVORE
OR INSECTIVORE
- ACCORDING TO SERENO = LAGOSUCHUS + LAGERPTON + PSUEDOLAGOSUCHUS
- LAGOSUCHUS + LAGERPTON + PSUEDOLAGOSUCHUS
+ Dinosauria = Dinosauromorpha
- Dinosauromorpha + Pterosauria = Ornithodira
- ACCORDING TO THE SERENO PHYLOGENY, DINOSAURS WERE PRIMITIVELY OBLIGATE
BIPEDS
- All quadrapedal dinosaurs (like Apatosaurus , Triceratops
, Ankylosaurus and Stegosaurus ) secondarily evolved
(reevolved) their quadrupedal stance [the primitive stance for archosaurs
is quadrupedal]
- REMNANT OF BIPEDAL ANCESTRY - BACK LEGS OF STEGOSAURS AND CERATOPSIANS
MUCH LONGER THAN FRONT LEGS
THE RISE OF DINOSAURS: SUPERIORITY OR LUCK
- EARLY TRIASSIC PERIOD (245 - 240 MILLION YEARS AGO)
- LAND FAUNA WAS DOMINATED BY THERAPSIDS
- Sleek, dog-like predators
- Rotund, beaked and tusked herbivores (see Color Plate IA)
- MIDDLE & FIRST PART OF LATE TRIASSIC PERIOD (240 - 225 MILLION
YEARS AGO)
- LAND FAUNA WAS DOMINATED BY COMBINATION OF THERAPSIDS & ARCHOSAUROMORPHS
- Herbivorous archosauromorphs (rynchosaurs)
- Carnivorous crocodile-like archosaurs (see Fig. 15.3)
- LAST PART OF LATE TRIASSIC PERIOD (225 - 208 MILLION YEARS AGO)
- LAND FAUNA WAS DOMINATED BY COMBINATION OF DINOSAURS (newly-evolved)
& ARCHOSAUROMORPHS FOLLOWING EXTINCTION OF MOST SYNAPSIDS (except for
newly-evolved mammals)
- Herbivorous archosaurs (aetosaurs) and prosauropod &
ornithischian dinosaurs
- Carnivorous crocodile-like archosaurs and theropod dinosaurs
- LATE TRIASSIC RISE OF DINOSAURS ATTIBUTED EITHER TO EVOLUTIONARY
ADVANTAGE (COMPETITIVE EDGE) OR TO OPPORTUNISTIC REPLACEMENT FOLLOWING
MASS EXTINCTION
- CHARIG SUGGESTS FULLY ERECT POSTURE OF DINOSAURS (Allowed longer stides
and more effective walking & running ability) IS THE COMPETITIVE EDGE,
WHILE BAKKER SUGGESTS "WARM-BLOODEDNESS" OF DINOSAURS IS THE
COMPETITIVE EDGE
- M. J. BENTON, P. E. OLSEN AND H.-D. SUES ARGUE THAT A MASS EXTINCTION
~225 MILLION YEARS AGO ALLOWED THE OPPORTUNISTIC REPLACEMENT OF THE THERAPSID
- ARCHOSAUROMORPH LAND FAUNA BY DINOSAURS
- some archosauromorphs, most synapsids and several
major groups of predatory archosaurs were decimated at this time
- also coincides with major extinction of the Dicroidium
flora (seed ferns, horsetails, ferns and gymnosperms)
- BENTON SUGGESTS THAT CLIMATE CHANGE (FROM MOIST & EQUABLE TO ARID
& HOT) ALTERED THE FLORA WHICH AFFECTED THE HERBIVORES AND THEN THE
PREDATORS
- OLSEN & COLLEAGUES SUGGEST THAT AN ASTEROID IMPACT CAUSED THE MASS
EXTINCTION ~225 MILLION YEARS AGO
- Manicouagan crater in northern Quebec is about the right age and
big enough (70 km in diameter)
- IN ANY EVENT, DINOSAURS SUPPLANTED SYNAPSIDS AS THE DOMINANT LAND
ANIMALS, A DOMINANCE THEY HELD FOR 160 MILLION YEARS, UNTIL THEIR OWN EXTINCTION