Chapter 12 Outline
INTRODUCTION TO THEROPODA (BEAST FOOT)
- DISTINCTIVE & INSTANTLY RECONIZABLE
- OBLIGATORY BIPEDS
- MOST HAVE ENLARGED HAND CAPABLE OF FLEXIBILITY AND GRASPING
- MOST HAVE SHARP & SERRATED TEETH
- Most are irredeemable carnivores
- LESS THAN A METER TO 14 METERS IN LENGTH; ~5 KILOGRAMS UP TO 5-7 THOUSAND
KILOGRAMS
- Note: your book on page 281 mistakenly says 40 meters
- GEOLOGICAL RANGE & DIVERSITY
- LATE TRIASSIC TO LATE CRETACEOUS (~230 - 65 MILLION YEARS)
- MAXIMUM DIVERSITY - AT LEAST 39 GENERA DURING THE LATE CRETACEOUS
- At least 87 genera throughout their time on earth
- FOUND ON ALL CONTINENTS (MOSTLY NORTH AMERICA & ASIA)
HISTORY OF THEROPOD DISCOVERIES
- 19TH CENTURY
- EUROPE
- Megalosaurus - one of the three original members
of Owen's Dinosauria
- FOUND IN 1819 BY REVEREND WILLIAM BUCKLAND; NAMED IN 1824; MIDDLE JURASSIC
IN AGE
- Composognathus (late 1850's)
- STUDIED BY T. H. HUXLEY IN HIS QUEST TO UNDERSTAND BIRD ORIGINS; LATE
JURASSIC IN AGE
- NORTH AMERICA
- Two genera from Late Cretaceous beds of Montana and of the eastern
U.S. (1850's, 1860's)
- Allosaurus & Ceratosaurus and 1 other genus from
Late Jurassic Morrison Formation (1870's, 1880's)
- ALLOSAURUS & CERATOSAURUS ALSO FOUND AT TENDAGURU
- Coelophysis from Late Triassic beds of New Mexico (1889)
- One other genus from Late Cretacous beds of the eastern U.S.
(1890)
- 20TH CENTURY
- EUROPE (1980'S)
- One genus from Early Cretaceous beds in England
- NORTH AMERICA
- Albertosaurus &Tyrannosaurus & 1 other genus
from Late Cretaceous beds in the Western Interior of North America (1900's)
- Three genera from Late Cretaceous beds in Alberta (1910's, 1920's)
- One genus from Early Cretaceous beds in Oklahoma & Texas
(1940's)
- Deinonychus from Early Cretaceous beds in Montana & Wyoming
(1969)
- Dilophosaurus from Early Jurassic beds in Arizona (&
later in China); Dromiceiomimus & 1 other genus from Late
Cretaceous beds in Alberta and 4 other genera from Late Jurassic Morrison
Formation (1970's)
- One genus from Late Triassic beds in Texas (1990's)
- ASIA
- Oviraptor &Velociraptor & 2 other genera from
Late Cretaceous beds in the Gobi Desert (1920's)
- Tarbosaurus from Late Cretaceous beds in Mongolia (1955)
- Deinocheirus & 4 other genera from Late Cretaceous beds
in Mongolia & China; 1 genus from Late Cretaceous beds in Central
Asia and 1 genus from Late Jurassic beds in China (1970's)
- Eight genera from Late Cretaceous beds and 1 genus from Early Cretaceous
beds in Mongolia (1980's)
- Two genera from Middle Jurassic beds, 1 genus from Early
Cretaceous beds and 1 genus from Late Cretaceous beds in Mongolia &
China (1990's)
- AFRICA
- One genus from the Late Jurassic beds in Tendaguru and 3 other genera
from Cretaceous beds in Egypt (Pre-WWI)
- One genus from Early Jurassic beds in Zimbabwe (1969)
- One genus from Early Cretaceous beds in the Sahara (1990's)
- SOUTH AMERICA
- Herrerasaurus from Late Triassic beds in Argentina
(1960's)
- One genus from Middle Jurassic beds in Argentina (1970's)
- Carnotaurus from Early Cretaceous beds and 2 other genera
from Late Cretaceous beds in Argentina (19780's)
- Eoraptor from Late Triassic beds in Argentina (1990's)
- ANTARCTICA
- One genus from the Early Jurassic beds (1994)
- NOTE: THIS IS A LITTLE MORE THAN 70% OF THE GENERA LISTED IN YOUR TEXT
(INCLUDING CHAPTER 12 AFTER THE "HISTORY OF THEROPOD DISCOVERIES"
SECTION & IN CHAPTER 15)
THEROPOD DIVERSITY
- SEVERAL CLADES OF THEROPODS
- BASAL FORMS
- LATE TRIASSIC FORMS 1-4 M LONG
- HERREROSAURUS & EORAPTOR FROM ARGENTINA
- ALL OTHER THEROPODS DIVIDED INTO 2 MAJOR CLADES - CERATOSAURIA &
TETANURAE
- CERATOSAURIA
- SMALL TO MEDIUM DINOSAURS, ABOUT 2-8 M LONG, IN EXISTENCE FROM THE
LATE TRIASSIC TO THE LATE CRETACEOUS
- COELOPHYSIS , DILOPHOSAURUS & AT LEAST 2 OTHER GENERA
FORM THE LATE TRIASSIC - EARLY JURASSIC COELOPHYSOIDEA
- CERATOSAURUS , CARNOTAURUS & AT LEAST 2 OTHER GENERA
FORM THE LATE JURASSIC - LATE CRETACEOUS NEOCERATOSAURIA
- TETANURAE (STIFF TAIL)
- SMALL TO LARGE DINOSAURS, LESS THAN 1 TO 14 M LONG, WITH THE BACK HALF
OF THE TAIL STIFFENED BY INTERLOCKING ZYGOPOPHYSES (FORE-AND-AFT PROJECTIONS
FROM THE NEURAL ARCHES), IN EXISTENCE FROM THE MIDDLE JURASSIC TO THE LATE
CRETACEOUS
- CONSISTS OF BASAL FORMS PLUS THE VERY DIVERSE AVETHEROPODA
- AVETHEROPODA
- SO NAMED BECAUSE OF THE BIRDLIKE FEATURES OF MANY OF ITS MEMBERS
- DIVIDED INTO MEGALOSAURUS (THE BASAL FORM), ALLOSAURIDAE &
COELUROSAURIA
- ALLOSAURIDAE
- LARGE LATE JURASSIC TO EARLY CRETACEOUS FORMS, INCLUDING ALLOSAURUS
- CEOLUROSAURIA
- AT LEAST 36 GENERA IN EXISTENCE FROM THE LATE JURASSIC TO THE LATE
CRETACEOUS
- At least 27 genera come from the late Cretaceous
- EVEN MORE BIRDLIKE FORMS THAT SHARE A NUMBER OF TRAITS, ESPECIALLY
A SEMILUNATE CARPAL, INCLUDING COMPSOGNATHUS (THE BASAL FORM) &
MANIRAPTORA
- MANIRAPTORA
- DIVIDED INTO 2 CLADES - THE FIRST CONSISTS OF OVIRAPTORIDAE (INCLUDES
OVIRAPTOR ), ELMISAURIDAE, TYRANNOSAURIDAE (INCLUDES TYRANNOSAURUS,
ALBERTOSAURUS & TARBOSAURUS ), TROODONTIDAE AND ORNITHOMIMOSAURIA
(INCLUDES DROMICEIOMIMUS & PERHAPS DEINOCHEIRUS ) [THESE
LAST 2 ARE PLACED IN A CLADE CALLED BULLATOSAURIA BECAUSE OF THEIR RELATIVELY
LARGE BRAINS]; THE SECOND CONSISTS OF DROMEOSAURIDAE (INCLUDES DEINONYCHUS
& VELOCIRAPTOR ) AND BIRDS
- Tyrannosauridae consists of large theropods
- The other families consist of small forms
- Oviraptorids have bizzare skulls
- Troodontids have sickle claws on their feet, as do the dromeosaurids
- Ornithomimosaurs have lost most of their teeth and have very long
arms
- Dromeosaurids have a pubis rotated downward or down & back,
like birds (& ornithischians)
THEROPOD PALEOBIOLOGY AND PALEOECOLOGY
- GEOGRAPHY
- THEROPODS ARE FOUND FROM THE PALEOEQUATOR TO HIGH-PALEOLATITUDES LIKE
THE TRANSANTARCTIC MOUNTAINS, ANTARCTICA
- Tetanurans are found only in the Laurasian continents
- Most ceratosaurs are restricted to the Gondwanan continents
- THEROPODS ARE FOUND IN A WIDE RANGE OF DEPOSITIONAL SETTINGS
- River channels, levees & floodplains to lakes to sand
dunes
- MOST THEROPOD SKELETONS ARE FOUND IN ISOLATION & DISARTICULATED
- However, several mass accumulations of single theropod species have
been found, including several hundred individuals of Coelophysis
at Ghost Ranch, New Mexico, and of Allosaurus at
the Cleveland-Lloyd Quarry, Utah
- THEROPODS AS LIVING ORGANISMS
- LARGE THEROPODS DWARFED PREY BY 35% OF BODY LENGTH
- May be due to abundance and rpaid turnover of the large herds of
rapidly growing, abundantly reproducing hadrosaurids and ceratopsids
- OBLIGATORY BIPEDS
- Body balanced over pelvis
- Vertebral column held nearly horizontally
- Hind legs were held close to the body based on trackways
- SOME TRACKWAYS SHOW ONE FOOT IN FRONT OF, RATHER THAN BESIDE, THE OTHER
- Walked on toes
- TOES TERMINATED WITH CLAWS
- SPEED
- Smaller theropods have short femora compared to the great length
of the rest of the hindlimb
- MADE FOR POWERFUL AND LONG STRIDES WHILE RUNNING
- SPEEDS WERE PROBABLY 40-60 KPH (25-37.5 MPH)
- WEAPONRY
- Dromeosaurids & Troodontids had sickle-shaped claws on their
second toe
- RAISED ABOVE THE GROUND DURING NORMAL WALKING AND RUNNING
- COULD SWING THROUGH A LARGE ARC OF MOTION
- WHEN LOWERED DURING A KICK AT A PREY ANIMAL'S ABDOMEN, WOULD DISEMBOWEL
THE ANIMAL IN ONE STROKE
- Powerful forelimbs equipped with strong, grasping hands
- Exceptional balance
- SMALL AND HIGHLY AGGRESSIVE THEROPODS, ESPECIALLY DROMEOSAURIDS LIKE
DEINONYCHUS AND VELOCIRAPTOR , USED THEIR STIFFENED TAIL
AS A DYNAMIC COUNTERBALANCING DEVICE AGAINST THE MOTIONS OF THE LONG ARMS
AND GRASPING HANDS
- Tiny forelimbs of Tyrannosaurus and Carnotaurus
- PERHAPS TO BALANCE THE EXCEPTIONALLY LARGE HEAD
- ALTHOUGH SMALL, THE ARM OF TYRANNOSAURUS COULD LIFT 200 KILOGRAMS
(440 POUNDS)
- MAYBE USED TO CATAPULT AN ANIMAL UP FROM A BELLY-DOWN SLEEPING POSITION
- Skulls
- RATHER PRIMITIVE WITH FEW SPECIALIZATIONS THAT SUGGEST MUCH FOOD PROCESSING
- WELL-ROUNDED OCCIPITAL CONDYLE & ARTICULATION WITH NECK VERTEBRAE
SUGGEST THE HEAD WAS HIGHLY MOBILE ON THE NECK
- SMALLER THEROPODS HAD SKULLS HINTING AT ACUTE VISION COUPLED WITH SERIOUS
BRAIN POWER
- TEETH
- Sharply pointed, often recurved and serrated
- SMALLER THEROPODS TEETH FUNCTIONED AS "GRIP-AND-RIP"
- TYRANNOSAURID TEETH WERE BANANA-SHAPED AND USEFUL FOR CRUNCHING RATHER
THAN TEARING
- POCKETS AT THE BASE OF SERRATIONS MAY HAVE HARBORED COLONIES OF BACTERIA,
AS IS THE CASE OF THE LIVING KOMODO DRAGON, RESULTING IN BACTERIAL INFECTIONS
FROM A THEROPOD BITE THAT WAS NOT IMMEDIATELY FATAL
- At least 2 groups of non-avian theropods have lost many or all of
their teeth
- ORNITHOMIMOSAURS - EARLY FORMS LOST UPPER TEETH BUT RETAINED A FEW
LOWER FRONT TEETH WHILE LATER FORMS HAD NO TEETH
- May have had beaks like birds for eating insects, small vertebrates,
eggs and fruit
- OVIRAPTORIDS - TOOTHLESS WITH 2 PEGLIKE PROJECTIONS IN THE MIDDLE OF
THE PALATE
- Strong jaw muscles; may have eaten bivalves by crushing shells
- SENSES
- Theropods needed to have keen vision, and so had large eyes
- ORNITHOMIMOSAURS HAD EXCEPTIONALLY LARGE EYES
- TYRANNOSAURIDS AND TROODONTIDS HAVE MORE FORWARD-LOOKING EYES, PERHAPS
FOR BINOCULAR VISION
- Theropods needed good hearing
- ORNITHOMIMOSAURS AND TROODONTIDS HAD ENLARGED MIDDLE-EAR CAVITIES,
SUGGESTING THEY WERE ABLE TO HEAR LOW-FREQUENCY SOUND
- TROODONTIDS HAD A PNEUMATIC CHANNEL PASSING THROUGH THE BASE OF THE
BRAINCASE THAT CONNECTED THE EARS & THE ASYNCHRONOUS PERCEPTION OF
A SINGLE SOUND AT THE TWO EARS WOULD HAVE ALLOWED THE DIRECTION OF THE
SOUND TO BE DETERMINED QUICKLY
- PREY
- Direct evidence
- COELOPHYSIS PRACTICED CANNIBALISM BASED ON JUVENILES IN ADULT
ABDOMENS
- COMPSOGNATHUS HAS A LIZARD SKELETON IN ITS ABDOMEN
- VELOCIRAPTOR WITH ITS HIND FEET JUTTING HALF INTO THE BELLY
OF A PROTOCERATOPS AND ONE HAND GRASPING THE FRILL AND THE OTHER
HAND IN THE MOUTH
- Faunal assemblages of herbivorous dinosaurs and theropods
- Sophistication of hunting
- THEROPODS HAD RELATIVELY LARGE BRAINS, WITH TROODONTIDS HAVING BRAINS
RELATIVELY LARGE AS BIRDS, SUGGESTING FAIRLY COMPLEX PERCEPTUAL ABILITY
AND MORE PRECISE MOTOR-SENSORY CONTROL, ALONG WITH HIGH ACTIVITY LEVELS
AND PERHAPS SOPHISTICATED INTER- AND INTRASPECIFIC BEHAVIOR
- PACK HUNTING MAY HAVE BEEN THE EXPRESSION OF INTRASPECIFIC BEHAVIOR,
PARTICULARLY FOR THE SMALL THEROPODS
- Three Deinonychus found in association with an ornithopod
- LARGER THEROPODS MAY HAVE PRACTICED SHARKLIKE HIT-AND-RUN ATTACKS OR
THEY MAY HAVE SEIZED THE SNOUT OR NECK IN THEIR LARGE MOUTHS AND SUFFOCATED
THEIR PREY, LIKE MODERN BIG CATS
- SKULL ADORNMENTS
- Several Theropods sport cranial crests, including Carnotaurus
, Ceratosaurus , Dilophosaurus and Oviraptor
and several other Theropods have elevated upper margins on the snout and
raised and roughened excrescences over the eyes, probably covered
with hornlets, including Allosaurus and the Tyrannosaurids
- SEXUAL DIMORPHISM AMONG THEROPODS
- Coelophysis and Tyrannosaurus
among others exhibit sexual dimorphism
- LARGER FORM IS THOUGHT TO BE FEMALE
- GROWTH
- Little is known
- Coelophysis bonebed indicates a 10- 15-fold increase in
size from hatchling to adult
- Tarbosaurus and Albertosaurus are thought to exhibit
similar growth in size
- Eggs thought to belong Protoceratops are now attributed
to Oviraptor based on embryos in eggs, the first for theropods,
recovered during the early 1990's by paleontologists from the American
Museum of Natural History during expeditions to the Gobi
- VOCALIZATIONS
- Bellows from Tarbosaurus and Albertosaurus
- Higher-frequency screeches from Troodon and Dromiceiomimus