Lesson 1: Appearance and Anatomy Flashcards
What is paleontology?
the study of dinosaurs is a subdivision of the branch of science known as paleontology
it is the study of prehistoric life
a paleontologist’s knowledge of prehistoric life comes primarily from fossils
What is a fossil?
a fossil is any persevered evidence left behind by a prehistoric organism
means “dug up”
fossils are usually objects or structures found buried in ancient rock formations
dinosaur fossils include footprints, eggshells, coprolites (fossil poop), and in rare instances even skin and feather impressions
most dinosaur fossils are bones
Why are most fossils comprised of bones?
bones are partially made of minerals, which do noy decay as easily as flesh and other soft tissues
for this reason, bones have a much greater chance of being preserved as fossils
How can the sizes of dinosaurs be compared to modern animals?
although birds are the smallest dinosaurs that we know of, we still have many examples outside this group of living dinosaurs that were no larger than a house cat
Why is it hard to accurately estimate the weight of dinosaurs?
dinosaurs filled with air sacs like birds so it’s hard to estimate weight
What are adaptations?
traits that have evolved because they serve specific functions
How are bones adaptations that help an animal survive?
bones passively resist gravity and maintain an animal’s form
bones provide a ridged framework for muscle attachment
bones provide protection and can also be major components of horns and other robust weapons
bones store mineral reserves
What are vertebrates?
are animals that have two special kinds of skeletal adaptations: skulls and vertebrae
fish, amphibians, turtles, snakes, birds, and mammals are all examples of vertebrates
What are vertebrae?
structures made primarily of bone and cartilage that surround a portion of the spinal nerve cord
together, vertebrae interlock with each other in a series and form the vertebral column
What are invertebrates?
animals that lack vertebrae
include animals like insects, spiders, snails, squids, clams, jellyfish, and worms
Why are vertebrates more numerous when it comes to species of large animals?
this success is probably related to the vertebral column’s ability to passively support weight and to anchor enlarged muscles
What is the skull?
the skull is not a single bone
rather, the skull is made up of many bones that are tightly locked together
What are the upper and lower jaws in the skull?
the upper and lower jaws may contain teeth and/or include a beak, and they are critical for interpreting what a dinosaur was adapted to eat
What is the brain case?
is a hollow chamber formed by multiple skull bones that houses the brain
there are many small openings into the brain case
nerves pass through these opening and connect to the brain
the size and shape of a brain case can indicate the size and shape of the brain case can indicate the size and shape of the brain that it housed, and , therefore, can provide clues to a dinosaur’s mental capabilities
What are the nares openings in the skull?
the nares are the pair of openings for the nostrils
What are the orbit openings in the skull?
the orbits are the pair of openings for the eyes
What are the fenestrae openings in the skull?
additional skull openings
behind each orbit, dinosaurs have two fenestrae
What are the laterotemporal fenestrae in the skull?
fenestrae on the lateral sides of the skull
What are the supratemporal fenestrae in the skull?
fenestrae on the top of the skull
What is the function of the laterotemporal fenestrae and supratemporal fenestrae?
provide extra room for large jaw muscles
What are the antorbital fenestrae in the skull?
between each orbit and naris
the function is unclear
they may have simply been adaptations that made dinosaurs skulls lighter, or they may have also housed large sinus cavities that helped warm the air that dinosaurs breathed
What is the vertebral column?
is comprised of a series of interlocking vertebrae that begins with the first vertebra in the neck and ends with the last vertebra in the tail
What is the centrum?
spool or disk shaped body on the vertebra
What is the neural arch?
above the centrum
covers the neural canal
What is the neural canal?
is the opening in each vertebra through which the spinal nerves run
What are vertebral processes in the vertebra?
extending from the centrum or neural arch
provide attachment surfaces for muscles and sometimes provide articulation surfaces for ribs
What are transverse processes in the vertebra?
extend from the lateral sides of the vertebrae
What are spinous processes in the vertebra?
extends upwards from the neural arch
What are cervical vertebrae?
vertebrae in the neck
often have extra-large openings for blood and nerve channels and are adapted to support the weight of an animal’s head
What are dorsal vertebrae?
vertebrae in the back
dorsal vertebrae often have tall spinous processes and large rib articulation surfaces
What are sacral vertebrae?
vertebrae in the hips
because the pelvic bones in terrestrial vertebrates serve as solid anchors for powerful leg muscles, the pelvic bones are fused to the sacral vertebrae
What is the sacrum?
to further increase the strength of the hips, the sacral vertebrae are also fused with one another and form a single solid bone structures called the sacrum
What are caudal vertebrae?
vertebrae in the tail
What are chevrons?
underneath caudal vertebrae are bones called chevrons
chevrons protect a large blood and nerve channel and provide support for tail muscles
In dinosaurs, how do the vertebrae support the ribs?
cervical, dorsal, sacral, and caudal vertebrae may all support ribs
the largest ribs are those that connect to the dorsal vertebrae and form the ribcage
in dinosaurs, all dorsal vertebrae connect with ribs
What are gastralia?
“belly ribs”
small ribs positioned across a dinosaur’s underbelly, underneath the ribcage
What are tetrapods?
animals that evolved from an ancient ancestor with four feet and four limbs
most tetrapods still have four feet and limbs, although some, like humans, have hands instead of front feet and some, like snakes, have lost their limbs altogether
What are limb girdles?
the limbs of a tetrapod are connected to the rest of the skeleton by limb girdles
What is the pectoral girdles?
the forearms connect to the pectoral girdle
What is the scapula?
is the largest bone in each side of the pectoral girdle
What is the pelvic girdle?
the hindlimbs connect to the pelvic gridle
each side of the pelvic gridle is composed of three bones that are tightly connected to one another
What is the ilium?
the upper hip bone
it is to the ilium that the sacral vertebrae are fused
below the ilium are the pubis and the ischium
What is the pubis?
is positioned in front of the ischium, nearer the belly
What is the ischium?
is positioned behind the pubis, nearer the tail
What is the acetabulum?
is teh depression or (as in dinosaurs) the hole in the pelvic girdle into which the hind limb articulates
What is the humerus?
between the shoulder and elbow is the largest bone in the forelimb, the humerus
What are the radius and ulna?
between the elbow and wrist are two parallel bones, called the radius and ulna
in most tetrapods, the radius is the thinner of the two
What are carpals?
the bones in the wrists
What are the metacarpals?
the bones between the wrist and fingers
What are phalanges?
finger bones
What is the femur?
between the hip and knee is the largest bone in the hindlimbs, called the femur
What are the fibula and tibia?
between the knee and the ankle are two parallel bones, called the fibula and tibia
What is the tibia?
the bone that forms our shin
the thinner of the two lower leg bones
What are the tarsals?
bones in the ankles
What are the metatarsals?
bones between the ankle and toes
What are Saurischian dinosaurs?
those that share an evolutionary ancestor and had a pubis that extended downwards and forwards, towards the ribcage
What are Ornithischian dinosaurs?
those that share an evolutionary ancestor that had both a special beak-forming bones in the upper jaw (called the predentary) and a pubis that extended downwards and backwards, towards the tail
What are the two major groups of saurischians?
sauropodomorphs and theropods
What are sauropodomorphs?
were large herbivores with elongated necks and relatively small heads
What are prosauropods?
were an early group of sauropodomorphs and were the first group of large-bodied herbivorous dinosaurs to evolves
What are sauropods?
were a later group of sauropodomorphs
many sauropods attained truly gigantic size, and the group includes the largest animals to ever walk the earth
they stood on four robust and column-like legs
sauropod vertebrae (particularly the cervical vertebrae) are filled with complex air sacks, which helped reduce weight
the teeth of sauropods are usually simple and peg-like
What are theropods?
were bipedal saurischian dinosaurs that shared a carnivorous ancestor
many theropods were carnivorous and have serrated blade-like teeth and sharp hooked claws, but some were herbivorous and a few lack teeth altogether
birds are a kind of theropod, making theropods the only group of dinosaurs that is not completely extinct
How is the backwards extending pubis found in ornithischians an adaptation?
created more space in the ribcage
this extra space was probably filled by extra-large digestive organs
What are the characteristics of ornithischians?
plant matter is much harder to digest than meat, and most herbivores need larger stomachs and intestines than do carnivores
all known ornithischian dinosaurs are thought to have been primarily herbivorous
the beaks are also herbivorous adaptations that helped ornithischians to chop off large mouthfuls of vegeation
What are the five major groups within ornithischians?
ornithopods
pachycephalosaurs
ceratopsians
stegosaurs
ankylosaurs
What are ornithopods?
include a wide range of dinosaurs that lack armor and that either walked bipedally all the time or assumed a bipedal stance when running
many ornithopods are small antelope-sized dinosaurs, but some, like the iguanodonts and hadrosaurs, grew to be multi-ton giants
What are iguanodonts?
are large ornithopods with a spike-shaped claw on each hand
What are hadrosaurs?
“duckbilled dinosaurs”
hadrosaurs evolved late in the history of dinosaurs, but were highly successful
some hadrosaurs have elaborate boney crests, and all hadrosaurs have strikingly large beaks in the front of their mouths and dense, tightly packed rows of small teeth in the rear of their mouths
together, these teeth form large chewing surfaces and are collectively referred to as dental batteries
What are pachycephalosaurs?
were bipedal with short arms, unusually stout and strong tails, and armored skulls
some pachycephalosaurs have thick, domed skull roofs and backwards pointing horns
they may have rammed predators or have butted heads with each other in competitions for territory or mating rights
have sharp conical teeth in the front of their mouths, behind their beaks, and leaf-shaped teeth in the rear
these front teeth have led to the hypothesis that they might have been omnivores
What are Ceratopsians?
are another group that evolved late in the history of dinosaurs
have large parrot-like beaks and skulls that are greatly expanded in the rear
this rear skull expansion is taken to an extreme and a large boney frill, or neck shield, is present
have large horns and also possess dental batteries
Triceratops is easily the most famous of the ceratopsians and is one of the largest
most were quadrupedal and have short tails
What are stegosaurs?
are a group of quadrupedal dinosaurs with rows of projecting osteoderm plates down their backs and long osteoderm spikes on their tails
some stegosaurs also have osteoderm spikes on their backs and over their shoulders
front limbs are much shorter than their hind limbs
heads are small relative to their bodies and their snouts are narrow
What are osteoderms?
bones that develop within the skin and are a common component of animal armor
What are ankylosaurs?
the most heavily armored of all dinosaurs
are quadrupedal with short legs and wide ribcages
the backs and skulls of most ankylosaurs are covered in spikey protective osteoderms
some ankylosaurs also have large osteoderms on the ends of their tails, forming a mace or “tail club”
unlike their relatives, the stegosaurs, most ankylosaurs have short snouts and broader, rounded beaks
What is integument?
body covering
How can skin impressions be preserved in fossils?
skin impressions from other regions of a dinosaur’s body can be preserved if a dinosaur was covered by mud shortly after it died and before its flesh rotted away
direct fossilization of skin and other soft parts is also possible, but such instances are exceedingly rare
Why is the scaly skin of dinosaurs more likely to be perserved?
the scaly skin of dinosaurs has a slightly better chance of being fossilized than would our own skin, because scales are coved by a substance called keratin
What is keratin?
is a tough but flexible material that also composes hair, feathers, fingernails, and the outside of claws, beaks, and horns
What was the major breakthrough in the study of dinosaur integument in 1996?
a small therapod specimen with fossil feathers was discovered in Liaoning, China
this little carnivorous dinosaur called Sinosauropteryx
the feathers had been preserved, because the dinosaur’s body was buried suddenly by extremely fine ash from a volcano
What aremelanosomes?
pigment cells within a feather
under microscopic examination, melanosomes can be observed in some fossil feathers, and they give clues to a dinosaur’s true colors
black and gray colors results from long and narrow melanosomes
brown and reddish colors come from short and wide melanosomes
white feathers have no melanosomes
How can the muscles of dinosaurs be interpreted from fossils?
one of the major functions of bones is to provide attachment surfaces and a rigid frame work for muscles
the shapes of bones often correspond to particular muscle shapes
muscles often leave behind scars on the surfaces of bones where they are attached
