Eutherian Diversity Flashcards
define a eutherian
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.
what are the synamorophies in eutherians
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
what is a chorioallantoic placenta
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) .
edentata
sloths, armadillos, anteaters, and pangolins.
Insectivora
moles, hedgehogs, shrews, and relatives.
Primates
lemurs, monkeys, apes, and relatives.
Dermoptera
flying lemurs, or colugos.
Chirodeta
bats
Pholidota
pangolints
Rodentia
rodents (mice, guinea pig, beavers)
lagomorpha
rabbits, hares, pikas
cetacea
whales and dolphins
carnivoras
cats dogs bears seals weasels hyaenas and relatives
tublilidentata
aardvarks
hyracoidea
hyraxes.
sirenia
dugongs and manatees
proboscidea
elephants and their extinct relatives.
Artiodactyla -
even-toed hoofed mammals.
Perissodactyla
odd-toed hoofed mammals
what happened in the gregory 1910 study
an episodic emergence of a ‘morphological tree’ for placental mammals
what 6 majors groups of placental mammals are there
Xenarthra, Lipotyphla, Anagalida, Archonta, Ferae, and Ungulata
xenartha
the basal most clade of placental mammals.
Containing sloths, anteaters, and armadillos, this American grouping included almost all members of the traditional Edentata
lipotyphyla
first epitherian group to diverge was the order Lipotyphla.
anagalida
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
archonta
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).
ungulata
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).
exeption case of edentata
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.
examples of studies over the past year that redefined animal clades
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).
what are the superorders
Afrotheria, Xenarthra, Euarchontoglires, and Laurasiatheria.
afrotheria
members of the Afrotheria are thought to be descended from an African ancestor from this fragmentation event,
afrotheria
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
vicariance event.
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.
xenartha
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)
euarchontoglire
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
lauriasiatheria
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
certatiodactyla
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.
when did afrotheria evolve
These morphologically diverse clades evolved from a single African ancestor during the mid Cretaceous
definition of afrotheria (synanomoprhies)
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)
Proboscidea - elephants
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
african elephant
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.
asian elephant
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.
sirenia
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
ceteceans
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
