Xenarthra

Question 1

“edentate”

Answer 1

Cuvian term, refers to armadillos, sloths, anteater, plus aardvarks and pangolins
Initially interpreted as being related

Question 2

Xenarthra groups

Answer 2

Cingulata (armadillos), 29 spp. - fossoriality
single, open rooted molars with elliptical cross sections, suggesting they have sustained and continuous growth in life (similar to Fruitafossor and aardvarks)
Pilosa (sloths, 5 spp. and anteaters, 3 spp.)
All new world, mostly South America

Question 3

Xenarthra characters

Answer 3

no enamel in teeth (reduced)
entotympanic auditory bulla
anteaters have no teeth
Xenarthrous vertebrae (extra intervertebral articulations in addition to zygopotheses), either throughout whole column or restricted to parts
adaptation to fossoriality, as makes vertebral column rigid to restrict force in digging stroke
Elongate acromion and metacromion in scapula
Infraspinatus spine and scapula spine
ischio-sacral fusion in pelvis
heavily ossified pelvis
enlarged olecranon process on ulna, allows for insertion of large triceps muscle, aids parasagittal digging

Question 4

Fruitafossor windsheffeli

Answer 4

Morrison formation, Upper Jurassic
Crown mammal, between australosphenidans and eutriconodonts on tree (stem therian)
Convergent evolution of xenarthry
Plus forelimbs and cranium suggest fossorial lifestyle

Question 5

Eurotamandua jonesi

Answer 5

Middle Eocene, Messel, Germany
Lacks xenarthry
Lacks metacromiun and infraspinatus spine
possesses ischial-sacral articulation
has xenarthran cranial adaptations

but likely similaries are adaptations for same food source (myrmecophagy and digging)

Question 6

Xenarthra fossil record

Answer 6

Undisputed record purely American, except for fragmentary possible anteater and sloth fossils in Antarctica
Armadillos from Palaeocene of Brazil
Glyptodonts and pilosan from oligocene onwards