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65 Cards in this Set

  • Front
  • Back

Clade Ornithischians

-Toothless predentary bone on the lower jaw


-Teeth set in front from the margin of the jaw, accommodating cheeks


-In primitive ornithischians, there is a supraorbital bone

Ornithopod

-Subgroup of Ornithischians


-Distinct because they had an obturator process on the ischium that linked it to the pubis


-Bipedal herbivores


-The jaw joint was below the tooth rows, and the vertebral column characteristically had a network of ossified tendons



Thyreophoran

-Meaning has armor


-Includes two groups; Thyreophora, and Ankylosaurus.

Stegosaurs

-In the group Thyreophora


-Ostroderm (armored external layer)


-Quadruped Herbivores


-One or two rows of spikes or plates on the back, and multiple spikes on the end of a flexible tail


-Plates likely for thermoregulation


-Very small walnut-sized brain

Ankylosaurs

-In the group Thyreophora


-Ostroderm (armored external layer)


-Quadruped Herbivores


-Fused dorsal vertebrae and a broadly flared, subhorizontal ilium (for muscle attachment and protection)


-A sharp-edged cropping beak for harvesting vegetation, but the teeth were unimpressive, i.e. they were not efficient grinders


-Continuous plates of armor (more likely for protection)


-Club like tail

Pachycephalosaurs

-Cretaceous


-Lacking osteoderms, and by having a ridge or shelf of bone at the rear margin of the skull; they comprise the Marginocephalia


-Bipedal Herbivores


-"Dome-headed" (or "fat-headed") dinosaurs

Ceratopsians

-Cretaceous


-Triceratops


-With horns as weapons and frills as neck protectors


-Great masses of muscle to move the jaw, and in McLoughlin’s extreme reconstruction, elevate/control the huge skull (likely not the case because the skull balanced on it's own fairly well)


-Last use for horns might have been with ritual combat for “territorial defence and establishing dominance hierarchies

The Flaming Cliffs

-mammals and dinosaurs in the Cretaceous rocks of the “flaming cliffs” of Mongolia; returning in 1923, they recovered over 100 specimens of Protoceratops over the next few years


-eggs in clutches/nests, in concentric circles


- originally thought to be oviraptors stealing eggs


- more eggs, one with an ossified embryonic skeleton that turned out to be Oviraptor, not Protoceratops


- velociraptor perhaps the actual egg stealer

Iguanodontids

-Part of the Ornithopods


-many were large (up to 10 m), with heavily built shoulders and forelimbs, suggesting they were part time quadrupeds


- the most famous is Iguanodon, one of the first scientifically (although inaccurately) described dinosaurs

Hadrosaurs

-Part of Ornithopods


-Duck billed dinosaurs


-somewhat reduced forelimbs, great dental batteries (dozens of tooth positions), and a modified pelvis


-they were upland grazers, eating tough, dry plant



Homeotherms

-maintain a nearly constant body temperature.

Poikilotherms

-body temperature fluctuates with ambient temperature.

Endotherms

-an internal heat source (usually a high metabolic rate) raises the body temperature

Ectotherms

-external heat source raises the body temperature

Euoplocephalus

-Type of Ankylosaur


-their conclusion was that this long passage, in a short skull, with mucus membrane but without turbinates, was a means to two ends: conserve moisture and regulate temperature


-Could have also been for acoustics

Coelurosaurs

-Brain level of birds and mammals

Thermostat Structures

-in lizards (also the tuatara), a thermostatic function is performed by the pineal foramen, described: an opening in the skull that exposes the pineal gland for temperature sensing


-Dinosaurs lack this feature, but so do some reptiles (snakes)

Stance/Posture/Gait

- all modern bipeds are endotherms

Circulatory System

- calculations for dinosaurs, based on the vertical drop from the brain to the heart,overlap values of other groups, noted: endotherm values, as well as the higher values for lizards


-ornithopod heart found with four chambers like mammals, rather than a two chamber like heart of reptiles

Level of Activity/Agility

-in general, endotherms have high levels of activity compared to ectotherms


-dinosaurs were primarily built for agility and speed

Predator:Prey Ratios

- endotherms require proportionately much more prey bodymass than ectotherms do, to support their higher metabolic rate


-the ratio of dinosaur predators to dinosaur prey is consistent with endotherm predators

Bone Histology and Growth

-the growth of the long bones in young birds and mammals is rapid, and facilitated by a certain feature: cartilaginous growth plates at the ends


-rapid growth fueled by endothermy


-Large numbers of haversian canals which is typically seen in dinosaur bones


-the presence of vascularized bone in most dinosaurs is suggestive but not diagnostic of endothermy; it may relate simply to large body size

Structure of Nasal Passages

-nasal cavity or passages is relatively much larger in endotherms than ectotherms, require greater quantities of 02


-99% of endotherms support turbinates


-Debate about whether or not dinosaurs had turbinates, as well as the function of turbinate like stuctures (cooling, or acoustics?)



Brain Size and Configuration

-High levels of brain sophistication leans towards endothermy


-Dinosaur brains were vastly in line with reptiles

Relatives

-the argument goes that birds are endotherms, and descended from coelurosaurs, so why not endothermic dinosaurs?


-endothermy was clearly derived at some point, but when?

Geochemistry of Teeth and Eggshells

- compared to contemporaneous crocodile fossil teeth, some dinosaur teeth show elevated levels of 16O compared to 18O, which is the expected effect when temperature is isolated as a variable controlling the incorporation of oxygen; higher temperatures favour 16O




-Some egg shells were comparable to endotherms, some comparable to exotherms. Possibly mesothermy

Latitudinal Spread

- rich and diverse dinosaur faunas have been recovered from Alaska (paleolatitude >70( N) and Australia (paleolatitude 80( S) in Cretaceous rocks


-Current ectotherms are confined to latitudes below 60N


-However, climate was different back then and might have simply been a means of migration

Inertial Homeothermy – Gigantothermy

-When growing, volume increases faster than surface area, so when growing from small to large like some sauropods, it creates a problem


-to summarize, if all dinosaurs were endotherms, the sauropods in particular would have had problems (“too hot”), and if all dinosaurs were ectotherms, then juveniles and small adults would have had problems (“too cold”); this may have favoured development of feathers as insulation in relatively small, active theropods (“just right”)

Mesotherms

-such organisms (e.g. tuna, leatherback sea turtle, echidna) characterized: have a significant internal metabolic heat source, but do not maintain a constant body temperature (“endothermic poikilotherms”)


-Dinosaurs might very well have fallen into this category, with slight overlap in values for high ectotherms and low endotherms

euryapsid reptiles

-A single high temporal opening


-derived from diapsid stock, in one of two fashions as described: either by closure of the lower temporal opening, or the low temporal opening may simply lack bone across the bottom to surround it and make a hole

Placodonts

-Triassic


-Low temporal opening closed in


-these had a stout, broad body with conventional limbs (not paddles), and an uncompressed tail


-skull and teeth: was stout, compact, and well-supported on a short neck; it had heavy, broad crushing teeth, as well as spatulate front teeth for dislodging prey


-adapted for crushing shellfish

Ichthyosaurs

-Triassic to Middle cretaceous


-a rather slender shape, and not much of a bend to the caudal vertebrae; dorsal processes on these vertebrae supported the smallest of dorsal flukes


-Sinusoidal flexing of the body for swimming


-Similarities to dolphins and sharks, fast swimmer and likely shallow water "shelf" habitat


-Living birth

Nothosaurs

-Triassic


-Lepidosauromorphs


-Limbs were reduced in size but not substantially modified; they were not graviportal


-Swimming in sinusoidal motion

Plesiosaurs/Pliosaurs

-Middle Triassic to late cretaceous


-Lepidosauromorphs


-typically small head and very long neck, as well as heavily modified limbs as paddles for propulsion


-Rigid body with large, fused, plate-like pectoral and pelvic girdles


-pliosaurs had larger heads and shorter necks, whereas plesiosaurs had smaller heads and longer necks, with as many as 76 cervical vertebrae in the extreme





Mosasaurs

-Late cretaceous


-Lepidosauromorphs


-These were shallow marine predators with reduced, paddlelike limbs for steering or lift rather than propulsion, and the tail was laterally compressed; swimming was sinusoidal; total number of vertebrae was high

Coelurosauravids

- these were primitive diapsids with the first 4 ribs normal (accommodating the heart and lungs); the latter 20 or so ribs were elongate, flat, and light, to support a membrane approximately 30cm wide


- the ribs were jointed to allow folding and the vertebrae were elongate to accommodate the folding as well


- Long spinal truck and short limbs; tree climber and gliding

Kuehnosaurids

- the ribs were longest near the shoulder and progressively reduced in length along the trunk, probably supporting a gliding membrane; the limbs apparently were not involved in the gliding membrane

Sharovipteryx

- known by a single specimen from Kazakhstan


- it did not have expanded ribs, but the limbs were evidently involved with the gliding membrane

Longisquama

- also from Kazakhstan, it reveals long, flat bones with curved tips; these articulated on, or were attached to, or were extensions of, the vertebral column


- they have been variously interpreted as gliding membrane supports (ribs). or as a support for a thermoregulatory organ (as in Dimetrodon), or as display features (aggressive?)


-Least likely to be a glider

PTEROSAURS

- these were diapsid reptiles with an antorbital fenestra, and therefore belonging to archosaurs, and at the same rank as thecodonts, crocodiles and dinosaurs


- the primary feature that distinguishes pterosaurs is the highly elongate fourth digit


- a less obvious but very important feature is the pteroid bone (not a thumb/digit), directed forwards from the wrist, that supported a membrane that connected with the base of the neck.


- one also notes the extraordinarily thin-walled bones, and the foot, with a long, clawless fifth digit

Rhamphorhynchoids

-first group of pterosaurs to appear


-they were relatively small with wingspans less than 2m


- the tail was long, comprising 25-40 caudal v. that were heavily reinforced, with ossified tendons beyond the fifth or sixth vertebra; some species had a vertical vane or rudder



Pterodactyloids

-Second group of pterosaurs to appear


- these were derived pterosaurs, with shortened tails usually comprising no more than 16 caudal vertebrae that exhibited a simple reduction in size and length toward the tip of the tail


-additionally, they often had more elongate or heavily modified skulls, at least exhibiting merging of the nostril [nares] and antorbital fenestra, and enlargement of the brain case



First Bird

-Protoavis - no


-Archaeopteryx ?


-Eosinopteryx brevipenna ?

Archaeopteryx

- the outstanding feature is the full preservation of feather impressions for the forelimbs and tail; without these feathers, the specimens would be recognized as something else: a small coelurosaur


-Pulvis directed slightly towards the rear and not fused with ischium





Archaeopteryx vs Birds

i. it did not possess pneumatic bones that are lightweight and connected to the respiratory system


ii. it had no sternum [features seen in the restoration are dermal scales in a chevron pattern], implying this: it lacked powerful flight muscles; it would have been a weak flier at best


iii. the wishbone [furcula] was solidly built, and therefore not able to perform certain functions noted: an efficient spring to act as a brace for the shoulder girdle or to store elastic energy


iv. it lacked the opening at the apex of the shoulder girdle that allows something unusual in birds: ventral muscles to pull on the dorsal surface of the humerus, raising the wing


v. it lacked fusion of the pelvis, skull, forelimb, and digits that characterizes birds, and also lacked fusion and reduction of the caudal (tail) vertebrae to form a particular feature: the pygostyle; in fact, the tail of Archaeopteryx would have been a drag for flight

Archaeoraptor liaoningensis

-originally touted as a clear missing link between dromaeosaurs and birds


-it turned out to be not only a composite specimen but a forgery, and an embarrassing mistake for all involved

Arboreal Hypothesis

-protobirds: tree climbers that used feathers as an aid to gliding/parachuting


- the most likely conclusion is that these animals were tree-dwelling (arborescent) gliders who deployed forelimbs and hindlimbs as a kind of parachute to control movement to other trees, or descent to the ground

Cursorial Hypothesis

- supposed they were runners (classic theropod configuration of hind limbs), aided by the lift provided by feathers; from here it would have been a "simple" transition to short gliding, then flight

Wing-Assisted Incline Running

-Wings were developed to help run up inclines as much as 105 degrees

Wing fighting hypothesis

- many birds engage in ritual combat that is forelimb- and ground-oriented; the suggestion is that aggressive beating of feathered forelimbs would produce lift, aiding the fighting posture and making for a more impressive display


- this might account for the long, feathered tail which is useless for flight, and the fact that the first fossil feathers are seen on a weak- to non-flier

Confusciusornis sanctus

-first recovered in 1994, from China, with 100s of specimens since, its significance described: it is regarded as the earliest known good flier (unlike achaeopteryx)


- it was magpie-sized, with a few features in common with Archaeopteryx: with long fingers and claws like archaeopteryx , but had a horny, toothless beak; it had a wishbone and other bird-like features, and the male [?] had long tail feathers like a fork-tailed flycatche

Anchisaurus

- prosauropod, which has derived characters that unite it with theropods, and also shares those characters (enumerated: jaw joints below tooth rows, double breastbone or sternum, and an unusual twist to the thumb or inner claw on the forelimb) with a very early ornithischian

Compsognathus

-possible Archaeopteryx ancestor


-it is now understood to be a contemporary of, rather than ancestor to, archaeopteryx


- it has been described as the smallest dinosaur, at 3-3.5 kg estimated live weight, and bears a strong resemblance to Archaeopteryx; may have been a primitive theropod, without definite carnosaur vs. coelurosaur affinity, or it may be directly related to birds


- it had a forward-directed pubis, but a manus with only two digits, a character which is considered to be derived; if this was a bird ancestor, it must have regained a digit as well as acquired other bird characteristics; the greater probability is that it and Archaeopteryx share a common ancestor

Deinonychus

-possible Archaeopteryx ancestor


- from the Lower Cretaceous of Montana, this dinosaur had a distinctive hind foot (with "sickle claw"), a rather heavily built skull, and a tail reinforced by ossified tendons, all of which differ from Archaeopteryx, although one feature was remarkably similar: the forelimbs were remarkably similar


- the evaluation of it as an ancestor given: on the whole it is too derived to be considered ancestral, though it could be related

Psittacosaurus

-Ceratopsian


-Early Cretaceous, east Asia


- briefly characterized: this was a bipedal herbivore, with a short snout, high-placed nostrils, a cropping "beak", and rearward expansions of the skull

Protoceratopsids

-Ceratopsian


-Late Cretaceous, east Asia and North America


- briefly characterized: these were quadruped herbivores, with a assive skull, cropping beak, enlarged rear frill, but no horns

Ceratopsids

-Ceratopsian


-Late Cretaceous, North America


- the great variety of various features noted: of skull, frill, and horn configurations, the skulls ranging from 1 to 2.4m in length

Cynodonts

-Part of therapsid group


i. the apparent immediate ancestor of mammals, and


ii. the only therapsid group to survive the end-Triassic mass extinction

Lower Jaw

- the configuration and relative proportions of the constituent bones change, as noted: the major one being the enlargement of the dentary bone (the one with teeth) and reduction of the post-dentary bones


- jaw articulation in reptiles is between the articular [on the jaw] and quadrate [on the skull] bones, but in the most advanced cynodonts, this progressed toward, but did not quite achieve, the defining mammalian characteristic of the dentary bone articulating on the squamosal bone


-allowed for stronger chewing and stronger muscles

Ears

- in the development of mammal-like reptiles, the quadrate and articular bones are attached but not sutured to the dentary


- this reduced pair of bones eventually form the malleus ("hammer") and incus ("anvil") of the middle ear of mammals, to transmit vibrations; reptiles have the stapes (“stirrup”) in common with mammals


-trend is to simplify the jaw, while the ear becomes more complex

Teeth

i. the teeth characterized in general terms: are heterodont (differentiated) even in pelycosaurs ; there are incisors, canines, and multicusped, complex teeth which are shaped and arranged for occlusion with opposing teeth


ii. tooth replacement characterized: the teeth were initially replaced many times, but in alternating waves; eventually, cynodonts replaced teeth in just a few episodes




= better chewing

Secondary Palate

- simultaneous performance of both functions (breathing and chewing) is made possible by a particular feature: the development of a secondary palate, an extra shelf below the original roof of the mouth, that serves to separate air and food entrances


- suggestions of a soft secondary palate are seen in Late Permian cynodonts, and a solid, bony version appeared in the Early Triassic

Limbs/Stance

-the feet pointed forward, not sideways, although the stance was still sprawling; in the development of therapsids, hind limbs acquired an erect stance (even the earliest mammals still had some forelimb sprawl)


-undulatory (up and down), not sinusoidal (side to side)

Ribs - Metabolism

- a muscular diaphragm aids respiration by facilitating filling and emptying of the lungs; what this requires in terms of the skeleton: this requires the absence of abdominal ribs, a characteristic seen in later therapsids which implies (does not prove) the presence of a diaphragm

Mammals

-First appeared in late Triassic


- they are identified as mammals on the basis of a few skull and jaw features, namely


i. jaw joint is between dentary and squamosal bones


ii. incisors, canines, and premolars were replaced only once during ontogeny


iii. molar teeth had two roots, and no replacement


- the earliest are presumed to have been egg-layers


- THUS a mammal is recognized as such on the basis of certain features: skeletal features, not metabolism mode of birth/reproduction