Proboscideans, Hyracoideans, Sirenians

clan

group of 50+ elephant

hyrax societies

-head male stands guard while feeding -polygamous mating structure, ~17 females & juveniles per one male -offspring disperse once grown -male signals start of breeding season

elephant dentition

28 total teeth throughout life; 3 in each side of the jaw at a time 1.0.3.3/0.0.3.3 horizontal tooth replacement; lophodont; loxodont very old elephants who have ground down their last set of teeth will feed on soft marshy grass; after last set is lost, starvation

Paenungulata

Unranked taxon that groups Proboscideans, Sirenians, Hyracoideans, Embrithopods, and Desmostylians

cold stress syndrome

symptoms related to manatee exposure to water temp below 68F

Which of the five paenungulate orders is the most ancient (or primitive)?

Hyraxes (Order Hyracoidea); followed by the Embrithopods

Family Trichechidae

1 genus, 2 species of manatees in the Order Sirenia

Sirenia

Order containing manatees and dugongs

Of all mammals, which animal has the longest length of gestation?

Elephant - 22 months

Elephant sexual selection

female look for minimum tusk lengths; will not mate with males with short tusks

joint family (proboscidean)

other families add to the stable family unit

manatee sexual selection

sperm competition; females may mate with as many as 20 males, often at the same time (mating herds)

congregation

two or more clans (100+)

stable family unit (proboscidean)

~10 elephants; one or two adult cows with their offspring

hyraceum

-large, communal piles of dung and urine which congeals into sticky mass -used in medicine to treat epilepsy, convulsions and women's disorders -has an affinity for the GABA-benzodiazepine receptor, a neurologic receptor site related to those disorders

internal nares - proboscidean

-possible reason for cyclops myth -nasal opening in the skull; located high on forehead, indicated by plate-size circle of skin

Condylarthra

-primitive ancestor of proboscideans, sirenians, and hyracoideans -evoled in the paleocene about 65 MYA -branch of Afrotheria that evolved to exploit low quality vegetation

juvenile/sub-adult period (Proboscideans - Four stages of Elephant Social Development)

infantile patterns disappear and adults patterns such as sexual behavior appear

Stellar's Sea Cow

member of Sirenia that is now extinct; could reach lengths of 8 meter and weight 8 tons; found on coasts of North Pacific

milk teeth in proboscideans

milk precursors to the tusks (incisor); fall out quickly and are replaced by the adult tusks by one year of age

Elephantidae

the only extant Family in Proboscidea

dugong dentition

-no incisors, 2 canines (tusks) which erupt after puberty -2.0.3.3/0.0.3.3

features of hyrax digestive systems

-stomach has three sections -stomach has cranial outpocketing -one large cecum and two small ceca -hind-gut fermenting allows hyraxes to eat leaves, twigs, fruit, bark, grass...

Tethytheria

-unranked grouping that contains Sirenians, Desmostylians and Proboscideans -more closely group than with hyraxes of embrithopods -lived on the shores of the prehistoric Tethys Seas (separated Europe and Eurasia) 50MYA

Superorder Afrotheria

mainly African mammals includes Paenungulata (proboscidea, sirenia, hyracoidea, embrithopods and desmostylians) but also: -Afrosiricida (tenrecs and golden moles) -Macroscelida (elephant shrew) -Tubulidentata (aardvarks)

pleura

each of a pair of serous membranes lining the thorax and enveloping the lungs in humans and other mammals

Sirenian lungs

lungs are unlobed; lungs and diaphragm extend the length of the entire vertebral column; each lung has its own hemi-diaphragm

What are elephant tusks?

modified upper second incisors with open-rooted pulp cavity (continuous growth)

Dentition of Hyracoidea, Procaviidae

-1.2.4.3/2.0.4.3 -no canines -diastema -upper incisors are pointed and tusk-like with no enamel on posterior surface -rubbery feet pads capable of sweating

Pachyostosis

Negative buoyancy in sirenians (remains in position; will neither float nor sink) -ribs and other long bones lack marrow, which means that manatee has a dense relatively heavy skeleton to counteract the buoyancy of the blubber

pneumatic cavities

air cavities within the skull bones that reduce the weight of the elephant's head; sponge-like or honey comb appearance

embrithopods

rhinocerous-like, herbivorous mammals with plantigrade feet

Key differences between manatess and dugongs

-manatees have rounded paddle tails; dugongs have dolphin-like flipper tails -dugongs are strictly marine; manatees utilize fresh water -manatees have shorter snouts -dugongs are exclusively benthic (only feed from bottom) -dugong teeth are not replaced via horizontal tooth replacement

manatee dentition

-no incisors, no canines -undifferentiated cheek teeth only -teeth replaced horizontally -tooth replacement continuous - polyphydont -0.0.3.3/0.0.3.3

proboscidean social organization

intimate matriarchal groups of females and calves; males are solitary or form loose bands; based off memory and recognition of others, familial history

Hyracoidea

-hyraxes; Family Procaviidae (Not rodent family) -comes from Greek/Dutch meaning for "shrewmouse" or "rockbadger" -small tails, short legs, small round ears

pleura cavity

space between a double membrane (the visceral and parietal pleurae) that completely covers lungs; prevents injury to lung due to friction during inspiration and expiration

neonatal period (Proboscideans - Four stages of Elephant Social Development)

stage 1; complete dependence of infant on mother

transition period (Proboscideans - Four stages of Elephant Social Development)

stage 2; some adult locomotor and feeding patterns develop

peer socialization (Proboscideans - Four stages of Elephant Social Development)

stage 3; much of the contact is with members of the group other than their mother

Moeritherium

an early elephant which we now know had an amphibious hippo-like lifestyle; very likely that proboscis was adapted for snorkeling (based on lungs and thoracic cavity physiology) and that elephant used to be semi-aquatic

Procaviidae

-Family of Hyraxes in the Order Hyracoidea -means "before caviids" (caviids = guinea pigs)

Why don't hyraxes need to consume large amounts of water?

-Low MR -low urine volume -sweat from feet?

Are hyraxes really relatives of elephants and sirenians?

Although relatively closely related, not all scientists support the proposal that hyraxes are the closest living relative of the elephant. Recent morphological and molecular based classifications reveal the sirenians to be the closest living relatives of elephants, while hyraxes are closely related but form an outgroup to the assemblage of elephants, sirenians, and extinct orders like Embrithopoda and Desmostylia.

Explain the physiology of the elephant's lungs that allow their lungs to handle pressures of snorkling.

-Normally delicate pleurae replaced with dense connective tissue and pleural cavity is replaced by loose connective tissue (instead of fluid), allowing more sliding movement. Otherwise, pressure differences in the thorax from snorkeling could rupture the small blood vessels of the pleura -(The elephant is the only mammal whose pleural space is obliterated by connective tissue) -diaphragm is much thicker than expected -respiratory movements are solely dependent on chest musculature (no mechanism of inflating lungs by negative pressure)

What are the commong characteristics amongst Proboscideans, Hyraxes, and Sirenians?

-all lack clavicles -all have short nails on their digits -females have 2 pectoral mammae (hyraxes also have 2 inguinal pairs) -females have bicornate uterus -males have abdominal testes and no bacullum -hind gut fermenting herbivores, prominant cecum

proboscis

-an elephant's trunk which is a fusion of the nose and upper lip -most important and versatile appendage; strong yet sensitive -used to ASSIST in drinking, but not for the actual consumption like a straw -used as snorkel when swimming

Sirenian GI features

-enlarged hind gut -cardiac gland: digestive gland which protects secretory cells -intestines up to 40m; passage time ~7days

Family Dugongidae

1 genus, 1 species of dugongs in the Order Sirenia

Desmostylians

-hippo-like -amphibious -tooth wear indicates they browsed on terrestrial plants -posture similar to hooved animals

Hyraxes were once the primary terrestrial herbivore in Africa. What pushed out the hyraxes?

competition from the newly-developed bovids during the Miocene

Traits of all Sirenians

-large fusiform bodies -valvular nostrils -no pinnae -horizontal tail -no external hind limbs -flipper-like forelimbs -prehensile upper lip

graviportal

-pillar-like legs of elephants, bones are large and stacked -elephants walks on toes & spongy heel pad (shock absorber) which becomes smaller when weight is removed -elephants needs less muscular power to stand because of its straight legs and large round, pad-like feet; can stand without tiring, rarely lie down

unique features of hyraxes

-scent gland on back used for territoriality and sexual cues -grooming claw on inner toe of back feet -upper incisors are pointed and tusk-like with no enamel on posterior surface

What are some of the key differences between African and Asian elephants?

1. Africans: bigger, larger ears, more complex trunk, diamond-shaped lophs on teeth, concave spinal line, two-lipped trunk; feeds on twigs, leaves, bark, some fruit 2. Asians: smaller, bi-lobed head shape, rectangular lophs, convex spinal line and single trunk-lip; feeds on grasses, leaves and fruit (softer food)

What charactertistics do proboscideans and sirenians share that they do not share with hyracoidea?

1. Elephants and sirenians have only two mammae in their pectoral region. Hyraxes have four more (two pairs) in the inguinal region. 2. Elephants and sirenians have horizontal molariform tooth replacement.

Deinotherium

extinct species of Proboscideans with tusks in the lower jaws, also 2nd incisors (in modern elephants these teeth disappear early without ever erupting)