Afrotheria Flashcards
(26 cards)
Afrotheria groups
Chrysochloridae (golden moles) Macroscelididae (sengis) Tubulidentata (aardvarks) Tenrecidea (tenrecs) Proboscidea (elephants) Sirenia (sea cows) Hyracoidea (hyraxes)
Afrotheria restricted to Africa
Chrysochloridae
Macrosclididae
Tubulidentata
Tenrecidae (mainly Madagascar)
Afrotheria with distributions out of Africa
Proboscidae - S. Asia
Sirenia - coastal India, Atlantic, and Pacific tropics
Hyracoidea - eastern Mediterranean
Ungulate grade
Elephants, sirenians, hyraxes large body size herbivorous 4-cusped upper cheek teeth unguligrade (walk on tips of digits) hooves: flattened terminal digits
Faunivore grade
tenrecs and golden moles small body size faunivorous 3-cusped upper cheek teeth walk on ankles/wrists narrow terminal digits
Paengulata
Simpson, 1945
Elephants, sea cows, hyraxes
Sirenia
Sea Cows Manatees: Tropical margins, Atlantic ocean No tusks Trichechus genus- 3 species
Dugongs:
Dugong dugong
tropical margins, Indian Ocean
with tusks
Stellar’s sea cow:
Hydrodamalis gigas
extinct in 18th Century
northern Pacific Ocean
Sirenians shared characters
anteriorly situated orbit
dorsally situation external nares
anterior projection on mandible in front of alveolar part of dentary
anteriorly extensive premaxilla
dense, pachyostotic ribs (allows neutral buoyancy)
Trichechus has continuous eruption of supernumerary molars (lost diphyodonty)
crypt at back of teeth, push rest forwards- horizontal conveyor belt
Sirenian fossil record
Prorastomus and Pezosiren portelli- Jamaica, early Eocene
several sirenian apomorphies in skull (characteristic jaw)
well-developed weight-supporting hind limb
pachyostotic ribs
Hyracoidea
Hyraxes restricted to Afro-Arabia Dendrohyrax - tree hyrax, 3 spp. Heterohyrax - yellow spotted hyrax, 3 spp. Procavia capensis - rock hyrax
mastoid completely occluded by squamosal
pi-shaped upper molar ectoloph (convergent w perissodactyla)
squamosal surrounds external auditory meatus
serial carpus taxeopody (as in proboscideans)- carpel bones aligned with respective digits
Hyracoidea fossil record
Diversity best documented at Fayum locality, northern Egypt, Eo-Oligocene boundary
Antilohyrax - similar to springbok, edentulous upper premaxilla, vegetation cropping structure broad hyper-pectinate combing incisor on lower jaw cursorial femur (bovid-like)
Titanohyrax ultimus- exceeded 2 tonnes
Tublidentata
Aardvarks
Faunivore-ungulate intermediate
sub-Saharan Africa
Evidence in N. America and Southern Europe from Miocene onwards eg. Orycteropus
mymercophagy
fossorial capacity
large body size
unguligrade locomotion
dual-lobed teeth, lacking enamel (have columnar shaped dentine)
cotylar fossa on astragalus for medial malleolus of tibia (deep Afrotherian character)
Macroscelidae
Sengis 4 genera, just over a dozen species, most sub-Saharan Africa except Petrosaltor rozeti in northwest Africa small body size faunivorous narrow terminal digits quadritubercular cheek teeth (modified to provide shearing in occlusion) unguligrade locomotion termination of ulna proximal to wrist
Tenrecidae
Tenrecs
most diverse Afrotherian clade
~30 species, mostly on Madagascar, 3 spp. on mainland:
Micropotamogale ruwenzorrii
Micropotamogale lamottei
Potamogale velox
all semi-aquatic
Potamogale maybe only mammal that swims using bilateral undulations of tail w little/no use of feet
zalambdodonty (upper molars “V” shaped w main cusp paracone at bottom of V)
lower molars show reduced/absent talonid basin
Chrysochloridae
Golden moles ca. 21 spp., 9 genera fossorial non-functional eyes covered w skin large fore-claws medially directed proximal ulna hypertrophied medial humeral epicondyle ossified flexor tendon cochleas highly coiled - reliance on terrestrial hearing limits capacity to adapt to aquatic environments lower jaw angle to form bony connection to hyoid bone (unique) digit III enlarged parasagittal digging zalambdodont lower molars show reduced/absent talonid basin
Eremitalpa granti
Golden mole species
eats mostly termites, which represent only 0.2% arthropods in the desert
find without visual or olfactory queus, navigates through sand by sound
greatly enlarged malleus enhances lever arm effect
malleus bones very dense, helps hearing low frequency sounds (ear ossicle hypertrophy) (also in a couple of Chrysochloris spp.)
Evidence for Afrotheria
Group identified by genomic means, most shared phenotypes lost
Morphological characteristics:
Testicondy- non-descent of male gonads in development, stay by kidney
in macroscelidids, elephants, sirenia, hyraxes, at least some hyraxes and golden moles
descended by ascrotal in aadvarks, tenrecs (plus xenarthrans, lipotyphlans, microbats, non-equid perissodactlys, cetaceans)
descended and scrotal in most nonaquatic euarchontoglires and laurasiatherian
also have increased number of thoracolumbar vertebrae: 20-30 across clade (hyraxes reach 30)
less than 20 in other mammals
placenta has rare shape and pattern of blood supply
increased variation in vertebral count (shared w xenarthrans)
delayed eruption of adult dentition- elephants, manatees and hyraxes share eruption of cheek teeth well past sexual maturity
chrysochloridae and other small afrotheres grow first then erupt cheek teeth
sengis- M1 doesn’t erupt until full dult size, P1 may be the only permanent tooth erupted at weaning and sexual maturity
but not unique to afrotheres, civets, cingulates (Dasypus), artiodactyla, perissodactyla
Proboscidean features
Tusks, trunk, horizontal tooth eruption, premolars not replaced, high pneumatised skull, coronoid 90 degrees from long axis of dentary, upper diastema, anterior orbit, external auditory meatus bound by squamosal, teeth with enamel plates in multiple rows of lophs
Living proboscidean genera
Loxodonta - African elephant
Elephas - Asian elephant
Difference between African and Asian elephants
African- tooth lamellae thicker, have more consistent diamond shaped teeth
2 “fingers” on trunk-one either side of end
Asian- sexual dimorphism, only males have visible tusks
1 “finger” at top of trunk
Phospthatherium escilliei
basal Eocene, Morocco (50-55mya)
anterior orbit
coronoid 90 degrees from long axis of dentary
EAM bound by squamosal
small- fox sized
lacks lower diastema
know it is proboscidean due to dense series of intermediates in fossil record leading up to elephants, within which this
Mastodon
Mammut not crown proboscidean 90 degree coronoid process, tusks, trunk very large skull, pneumatized different teeth, not lamellar but more primitive cuspiform, bilophodont teeth similar to Gomphotherium
Eritreum melakeghebrekristoi
late Oligocene
oldest proboscidean with horizontal tooth replacement
(can tell because vertical would occlude jaw joint- tooth in crypt in fossil)
Phiomia serridens
vertical tooth replacement
lower tusks, smaller upper tusks
small, non pneumatized skull
