Selected Figures from EEE 338 Lectures:

Hypothesis of phylogenetic relationships among the Tetrapoda

Lists of shared derived characters (synapomorphies) at each node:

A

• internal nares*
• labyrinthodont teeth*
• flattened skull with elongate snout
• eyes on top of head
• absence of separate medial fins
• identifiable frontal bones in skull

  *also found in other lobe-finned fishes

B Tetrapoda

• presence of phlanges combined with ankle & wrist joints
• loss of connection of pectoral girdle with skull
• freedom of movement of head and freedom of head from jarring when walking
• well developed pelvis (ischiac ramus of pelvis and pubic symphysis) and specialization of the part of the vertebral column that articulates with the pelvis
• presence of stapes
• fenestra ovalis, an opening in the lateral wall of the auditory capsule through which the stapes communicates with the inner ear

C Reptiliomorpha

• narrow premaxillae
• vomers taper forward
• phalangeal formulae of foot (2.3.4.5.4-5)

D Batrachomorpha

• flat skull
• no cranial kinesis
• less than 4 fingers

E

• pedicellate teeth
• biphasic life cycle
• 26 or fewer presacral vertebrae
• lack of intertemporal bone
• large orbit
• large otic notch
• maxilla articulates with quadratojugal
• paired occipital condyles

F Lissamphibia

• two types of skin glands (mucous & granular)
• fat bodies associated with gonads
• double-channeled sensory papillae in inner ear
• green rods ( a special type of visual cell (unknown in caecilians--perhaps lost?)
• ribs do not encircle body
• ability to elevate the eye (with levetator bulbi muscle)
• forced pump respiratory mechanism
• extreme reduction of skeletal elements in skull
• paired occipital condyles

G

• supraoccipital present
• sacrum with two vertebrae

H Amniota

• frontals contact orbit
• rounded occipital condyle
• tibiale, intermedium, and centrale of lower tetrapods fused to form the astragalus
• amniotic (cleidoic) egg
• two sacral vertebrae (and ribs)
• two extra pairs of cranial nerves (11th & 12th axial nerves incorporated into skull)

Hypothesis of phylogenetic relationships among the Reptiliomorpha

Lists of shared derived characters (synapomorphies) at major nodes:

Reptilia

• tabular (when present) small
• suborbital foramen present in palate
• large post-temporal fenestra
• parasphenoid wings absent

  Anapsida

  • large lateral foramen on maxillae
  • quadratojugal expanded dorsally
  • jaw articulation in front of occiput
  • illliac blade expanded dorsally

  Diapsida

  • upper and lower temporal fenestrae
  • suborbital fenestra
  • ossified sternum
  • complex tibio-astragalar joint

    Archosauria

    • antorbital fenestra in snout wall between nostril and orbit
    • laterally flattened teeth with serrations
    • lateral mandibular foramen in posterior lower jaw bones

    Lepidosauria

    • lacrimal reduced or absent
    • supratemporal absent
    • postparietal and tabular absent
    • pelvic girdle fenestrate
    • fused astragalus and calcaneum
    • loss of centrale
    • loss of distal tarsals 1 & 5
    • regular ecdysis
    • transverse cloacal slit

Hypothesis of phylogenetic relationships among the extant Anapsida

Hypothesis of phylogenetic relationships among the extant Diapsida

Rhynchocephalia

• acrodont teeth with regional specialization
• teeth present on palatine bones
• both upper and lower temporal arches complete

Squamata

• high degree of skull kinesis
• nasals reduced
• squamosal reduced or absent
• quadratojugal absent
• lower temporal bar absent
• ribs single headed