Anatomy Lecture 4 Flashcards
➢ List the four classes of tetrapods and recognize examples and characteristics of each class.
o Amphibia
o Reptillia
o Aves
o Mammalia
Identify the group of Carboniferous tetrapods that is presumed to have given rise to modern amphibians
o Temnospondyl
➢ List the three orders of modern amphibians and list major characteristics of each order.
o Caudates (urodeles):
• Name implies that they have a tail
• Includes modern salamanders
• Earliest salamander is Karurus from Upper Jurassic
o Anurans:
• Name implies that they lack a tail
• Includes modern frogs and toads
• Earliest frog ancestor is Triadobatrachus from Lower Triassic
• Earliest known frog is Vieraella from early Jurassic
• Triadobatrachus was similar to that of modern frogs, but Similar to modern frogs but vertebral column was longer and hind legs were shorter
o Apodans (caecilians)
• Name implies that they lack limbs
• Includes modern caecilians
• Earliest caecilian is Apodops from Paleocene
• Wormlike, externally segmented, burrowing, subterranean amphibians
Define Anapsid, Synapsid, Diapsid, and Euryapsid
➢ Term “apsid” refers to the arch ➢ Anapsid (no arch) skulls: o Have no additional opening other than nasal and orbital ➢ Diapsid (two arches) skulls: o Have two additional openings ➢ Synapsid skulls: o Have one additional opening ➢ note that the term “euryapsid” has been used in older classification schemes and refers to a skull with one additional opening but its nw thought to be am modified diapsid skull
➢ Name the two groups of anapsids and indicate which one is the stem reptile for all other reptiles and list its characteristics
o Two groups: Cotylosaurs and Chelonia (turtles). However, it is now thought that turtles have a modified diapsid skull in which both openings have been lost. Therefore, turtles are probably not direct descendants of the cotylosaurs.
o Cotylosaur (Diadactomorph) is the one that stem reptiles for all other repitles
• Characteristics:
• Stem reptiles for all other reptiles
• Resembled seymourian tetrapods
• May have been several feet in length
• Had considerable dermal amour
• Skulls more laterally flattened rather than dorsoventrally flattened as in amphibians.
• NO additional skull opening behind orbits
o Temporalis muscles are the major jaw closing muscles and run between the medial side of the lower jaw and the lateral side of the braincase
o Additional openings would allow for more muscle expansion and amore powerful bite and more efficient chewing
• Earliest cotylosaurs were the captorphinids
o First appeared in the Carboniferous period
o Relatively small and sleneder
o Probably insectivorous
➢ Describe the distinguishing feature between the two groups of dinosaurs
o Two groups of dinosaurs are: Ornithischians (bird-hipped dinosaurs) and Saurischians (lizard-hipped dinosaurs).
• Book says the two groups are classified according ot their pelvic girdle
o Bird hipped dinosaurs (Ornithischians)
• Have a tetraradiate pelvic girdle that resembles that of birds. IN this type of pelvis, the pubis extends both anteriorly and posteriorly paralleling the ischium
• Both groups include quadrupedal and bipedal forms (they move on either 4 or two limbs)
• Include groups such as hadrosaurs, stegosaurs, triceratops
o Lizard-hipped dinosaurs (Saurischians):
• Have a triradiate pelvic girdle similar to modern lizards, in which the pubis extends only anteriorly while the ischium extends posteriorly.
• Both groups include quadrupedal and bipedal forms
• Includes Apatosaurus, allosaurus, and tyrannosaurus
➢ List the three subgroups of modern lepidosaurs and compare their skull type with regard to lateral, postorbital openings
o Three modern groups are: Sphenodons, snakes, and lizards
• Sphenodon:
• Has a true diapsid skull and a primitive pectoral girdle
• The shoulder girdle or pectoral girdle is the set of bones which connects the arm to the axial skeleton on each side
• Snakes:
• Snakes have lost both bars (or arches)
• Lizards: Modern lizards have lost the lower bar (arch)
• Remember each opening is bounded by a bony bar (or arch)
➢ Explain why dinosaurs form a paraphyletic group
o Birds are generally their own class but may be thought of as feathered dinosaurs. Also note that the term “dinosaurs’ refers to a paraphyletic group, because it includes the ancestor of birds and dinosaurs, but it does not include the birds. o A paraphyletic group is a group of organisms that includes an ancestor but not all of its descendants.
➢ List reptilian characteristics found in early birds such as Archaeopteryx
• Upper Jurassic (Time)
• Bony tail (modern birds have replaced bony tail with feathers)
• Separate fingers with claws (Birds have reduced digits without claws)
• Teeth (modern birds lack teeth)
o Later, better preserved fossils showed the presence of feathers. This indicated that Archaeopteryx was a bird, but not the first bird (who cares).
o There is a gap in the bird fossil record until the Cretaceous, when a few fossils of birds similar to modern aquatic birds were found.
• Hesperornis is a foot propelled diving bird with some reptilian characteristics, including teeth
➢ Describe theories on the origin of flight in birds
o Birds probably evolved from a bipedal archosaur (probably a saurischian)
• This transition is not in the fossil record
• Neither is any evidence as to why flight might have evolved. But here are some theories that I don’t give a shit about:
• May have evolved as a means of thermal insulation
• May have evolved as an insect catching net
• May have allowed for better pursuit of prey or escape from predication
• May have allowed early archosaurs to roost in trees at night
➢ Identify the earliest group of synapsids
o Earliest synapsids were the pelycosaurs.
➢ Identify the characteristics shared by mammals and advanced therapsids
- Secondary palate consisting of premaxillary, maxillary, and palatine bones
- Pterygoid bones solidy fused to braincase
- Enlarged dentary bone
- Differentiation of teeth into incisors, canines, and cheek teeth
- Considerable regional differentiation of ribs and vertebrae
- Legs pulled in
- Ilium extended forward
- Elongated sacrum
- Feet well developed
- Jaw articulation pattern:
- Mammalian jaw articulation occurs between temporal bone and mandible
- Reptilian jaw articulation occurs between quadrate and articular bones
➢ Identify mammalian characteristics
o Live birth (except egg-laying mammals)
o Endothermy
o Respiratory diaphgram
o Four chambered ehart with completely divded ventricle
o Neocortex:
• Multiple layer of neurons covering cerebral lobes of brain
o Double occipital condyle
o Mandible consisting of a single bone (dentary)
o Bony secondary palate
o Loss of interclavicle (except in egg laying mammals)
o Hair/fur
o Possess mammary glands
➢ Identify the earliest group of mammals and describe their dentition
o Earliest group of mammals were the morganucodonts. Heterodont dentition with triconodont molars
➢ List and describe some of the requirements for terrestrialism
1) Changes in organs for special sense
2) secretion of nitrogenous wastes
3) changes in reproduction
4) Resistance to Gravity
5) Desiccation (Extreme dryness) control
