Eutherian Diversity

Question 1

define a eutherian

Answer 1

placental mammals, eutherians constitute one of the three major extant lineages of the Mammalia

eutherians possess a unique jaw articulation between the dentary and the squamosal - reflected in a middle ear composed of three bones formerly involved in the jaw joint -

a body covered in insulating hairs (unless secondarily lost),

and mammary glands, which produce milk used to feed developing offspring.

Question 2

what are the synamorophies in eutherians

Answer 2

presence of a chorioallantoic placenta.

Optic foramen not confluent with the orbital fissure.

Foramen ovale (round window) located within alisphenoid.

Absence of the os caruncula, or egg tooth. This is present in the offspring of non-eutherian groups such as birds, lizards, and monotremes, used to break open the egg during hatching

Question 3

what is a chorioallantoic placenta

Answer 3

This is an organ attached to the wall of the uterus that allows repiratory, nutritional, and excretory exchange between the circulatory system of the mother and the offspring. It has convergently evolved in bandicoot marsupials (order Peramelemorphia) .

Question 4

edentata

Answer 4

sloths, armadillos, anteaters, and pangolins.

Question 5

Insectivora

Answer 5

moles, hedgehogs, shrews, and relatives.

Question 6

Primates

Answer 6

lemurs, monkeys, apes, and relatives.

Question 7

Dermoptera

Answer 7

flying lemurs, or colugos.

Question 8

Chirodeta

Answer 8

bats

Question 9

Pholidota

Answer 9

pangolints

Question 10

Rodentia

Answer 10

rodents (mice, guinea pig, beavers)

Question 11

lagomorpha

Answer 11

rabbits, hares, pikas

Question 12

cetacea

Answer 12

whales and dolphins

Question 13

carnivoras

Answer 13

cats dogs bears seals weasels hyaenas and relatives

Question 14

tublilidentata

Answer 14

aardvarks

Question 15

hyracoidea

Answer 15

hyraxes.

Question 16

sirenia

Answer 16

dugongs and manatees

Question 17

proboscidea

Answer 17

elephants and their extinct relatives.

Question 18

Artiodactyla -

Answer 18

even-toed hoofed mammals.

Question 19

Perissodactyla

Answer 19

odd-toed hoofed mammals

Question 20

what happened in the gregory 1910 study

Answer 20

an episodic emergence of a ‘morphological tree’ for placental mammals

Question 21

what 6 majors groups of placental mammals are there

Answer 21

Xenarthra, Lipotyphla, Anagalida, Archonta, Ferae, and Ungulata

Question 22

xenartha

Answer 22

the basal most clade of placental mammals.

Containing sloths, anteaters, and armadillos, this American grouping included almost all members of the traditional Edentata

Question 23

lipotyphyla

Answer 23

first epitherian group to diverge was the order Lipotyphla.

Question 24

anagalida

Answer 24

Rodentia (mice, rats, guinea pigs, and relatives), Lagomorpha (rabbits, hares, and pikas), and Macroscelidea (elephant shrews). Within the Anaglida, Rodentia and Lagomorpha were recognised as sister taxa in the clade Glires

Question 25

archonta

Answer 25

Archonta was proposed as a clade containing the orders Scandentia (tree shrews), Primates (lemurs, monkeys, apes and relatives), Dermoptera (flying lemurs, or colugos), and Chiroptera (bats).

Question 26

ungulata

Answer 26

Unguiculata consisted of two large sister clades, the Anaglida and the Archonta. The former contained three orders: Rodentia (mice, rats, guinea pigs, and relatives), Lagomorpha (rabbits, hares, and pikas), and Macroscelidea (elephant shrews).

Question 27

exeption case of edentata

Answer 27

Pangolins (Pholidota) - the remaining “edentates” - were shown to be more closely related to carnivorans (such as dogs and cats) - and indeed many other eutherians - than to the other “edentates” on the basis of shared morphological features, and so the Edentata is now considered a polyphyletic grouping, rendering it obsolete.

Question 28

examples of studies over the past year that redefined animal clades

Answer 28

Over the past two decades, a wealth of molecular phylogenetic studies that compare DNA sequence data between taxa have yielded insights into eutherian phylogeny that are opposed to those inferred using morphological characteristics.

Some early molecular studies proposed seemingly radical hypotheses, such as the statement “the guinea pig is not a rodent” (D’Erchia et al., 1994), a close affinity between whales and hippopotamids (Irwin & Arnason, 1996), or that bats are more closely related to ungulates than to primates (Pumo et al., 1998).

Question 29

what are the superorders

Answer 29

Afrotheria, Xenarthra, Euarchontoglires, and Laurasiatheria.

Question 30

afrotheria

Answer 30

members of the Afrotheria are thought to be descended from an African ancestor from this fragmentation event,

Question 31

afrotheria

Answer 31

members of the Afrotheria are thought to be descended from an African ancestor from this fragmentation event,

Proboscidea - elephants
Sirenia - sea cows
Hyracoidea - hyraxes
Tubulidentata - aardvark
Macroscelididae - elephant shrews
Tenrecidae - tenrecs
Chrysochloridae - golden moles

Question 32

vicariance event.

Answer 32

This type of divergence, where movement of a landmass causes an evolutionary split to produce two independently evolving lineages (cladogenesis) is called a vicariance event.

Question 33

xenartha

Answer 33

The Xenarthra are a clade of American origin, today almost completely confined to South America (one species of armadillo is present in North America). Containing two orders - Cingulata (armadillos) and Pilosa (anteaters and sloths)

Xenarthra and Afrotheria are now thought to form a clade, collectively known as the Atlantogenata

Xenarthrous articulations (from which they take their name) between the lumbar vertebrae, which function as extra zygapophysis-like processes to brace this part of the skeleton when burrowing, digging or climbing (Rose & Emry, 1993)

Question 34

euarchontoglire

Answer 34

scadentia (trees shrews)

primates

rodentia

lagomorpha (hare)

dermoptera (flying lemurs)

The Euarchontoglires is thought to have split from its sister taxon Laurasiatheria approximately 100-90 million years ago

colugos, primates, tree shrews, rodents, and lagomorphs all share an 18 amino-acid deletion in the SCA1 protein that is unique to them among mammals

Question 35

lauriasiatheria

Answer 35

chiroptera (bats)

cetartiodactyla (cetecea + artiodactyla; whales, cows, pigs, hippos, deer)

carnivora

pholidota (pangolins)

euliptophyla (shrews and moles)

the Laurasiatheria originated 77 – 85 million years ago (Ma), before the Cretaceous-Tertiary (K/T) boundary (approx. 65.5 Ma)

no morphological synapomorphies supporting Laurasiatheri

the supercontinent formed of North America and Eurasia

Question 36

certatiodactyla

Answer 36

Cetacea (whales and dolphins). Note that while extant cetaceans clearly do not walk on the tips of their digits - indeed they swim! - there is convincing fossil evidence to demonstrate that their ancestors were, in fact, unguligrade, and were closely related to artiodactyls. Indeed, some research, both molecular and morphological, proposes that the cetaceans actually evolved from artiodactyl ancestors, and thus the orders are often merged to form the Cetartiodactyla.

Question 37

when did afrotheria evolve

Answer 37

These morphologically diverse clades evolved from a single African ancestor during the mid Cretaceous

Question 38

definition of afrotheria (synanomoprhies)

Answer 38

there is no single unambiguous morphological synapomorphy defining the Afrotheria

all afrotherians share a 9-bp deletion in the BRCA1 gene

morphologically; probably reflect parallel evolution in response to the similar ecological specialisations of each species:

Long snout (although short in sirenians, but enlarged and used for grasping vegetation)
Tactile snout (excluding hyraxes)
Mobile snout (excluding tenrecs)

Question 39

Proboscidea - elephants

Answer 39

The order Proboscidea now exists only as a single family, Elephantidae, containing three living species of elephant in two genera.

These animals are the largest living terrestrial animals, and also have the longest gestation period of any animal.

African forest elephant - Loxodonta cyclotis
African bush elephant - Loxodonta africana - the largest living terrestrial animal.
Asian elephant - Elephas maximus

Question 40

african elephant

Answer 40

African elephant - occur in 37 countries in sub-Saharan Africa; some areas of large continuous range still present, however ranges are becoming increasingly fragmented. They dwell in a wide variety of African habitats, including dense forest, grassland, open and closed savanna, arid deserts, ocean beaches, and mountain slopes.

Question 41

asian elephant

Answer 41

Asian elephant - found in isolated populations in 13 different countries within the Indian subcontinent and Southeast Asia. They are grassland- and forest-dwelling generalist herbivores. They can survive in many types of forest, ranging from tropical evergreen and semi-evergreen, to dry thorn forest, as well as moist and dry deciduous.

Question 42

sirenia

Answer 42

Phylogenetic interrelationships within the Paenungulata have also been the subject of scientific debate.

Traditionally, morphological studies placed the sirenians as the extant sister group to the probiscideans in the clade Tethytheria - which also contains the extinct aquatic Desmostylia as sister group to the Probiscidea - united by the following shared derived characteristics (synapomorphies):

Rostral displacement of the orbits.
Early signs of bilophodont dentition - double crested teeth.
Laterally expanded zygomatic process of the squamosal

Trichechus manatus - West Indian manatee.
Trichechus senegalensis - West african manatee.
Trichechus inunguis - Amazon manatee.
Dugongidae (dugongs) - containing the dugong, Dugong dugon..

extant sirenians are large animals (adults usually 3-4 m head-tail) with stout bodies. They are fully aquatic, possessing appropriate specialisations, including broad paddle-like forelimbs and a horizontal tail fluke. The pelvic skeleton and hindlimbs are highly reduced, present only as vestiges embedded within the trunk musculature.

Sirenians are herbivorous - a unique feature among living aquatic mammals. They swim along the ocean floor, and graze on the grasses and other aquatic plants that they can crop with the two muscular lip-like projections flanking the mouth. These projections are equipped with stiff, sensory bristles, which afford sirenians a high level of tactile sensitivity. In contrast, the eyes are relatively small, as are the ear openings and the nostrils

Question 43

ceteceans

Answer 43

Cetacea is the name for the monophyletic clade that comprises the whales, dolphins and porpoises. For more information on the origins of the Cetacea, as well as their phylogenetic position within Cetartiodactyla,

Traditionally, the two mammalian orders Artiodactyla and Cetacea were classified as distantly related lineages, the former containing the even-toed ungulates while the latter comprised whales and dolphins

0th Century pointed towards an affinity between cetaceans and artiodactyls, based on the vestigial hindlimbs of Eocene whales such as Basilosaurus, exhibiting a paraxonic arrangement - an ‘even-toed’ morphology characterised by a plane of symmetry between digits III and IV - shared with artiodactyls and the extinct mesonychids