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If all domestic dogs were to go extinct but we could save a single breed, the breed that should be saved is the Pembroke Welsh Corgi. Corgis are often thought of as “big dogs on short legs” because although they average a height of between 25 and 30cm, they have personalities reminiscent of bigger dog breeds. Corgis are playful and energetic, yet not so energetic that they are impossible to tire out, which—along with their smaller stature—makes them a versatile breed that could be suited to a wide range of owners. They are also highly adaptable, and can live in a variety of housing arrangements provided that they are able to get a moderate amount of exercise. Corgis were originally bred to be herding dogs, so they are intelligent and independent, and are easily trainable with some patience. Because of their herding origins, Corgis are highly alert and aware of their surroundings, and will usually react to any changes in their surroundings by barking, which makes them good watch dogs.

Cetaceans are split into two main Suborders: S.Mysticeti and S.Odontoceti. Suborder Odontoceti contains all the toothed whales, and there are features common to all families in the suborder. These include the presence of teeth, an asymmetrical skull (likely used in echolocation), a single external nares, and a melon. The melon is an oil-filled structure most evident in sperm whales that is thought to be used to focus sound during echolocation. Odontocetes also have an ear bone (petrosal) that is surrounded by sinuses and entirely disconnected from the skull, which serves to reduce the vibrations passing into the bones of the skull. In Mammalogy lab we looked at four of the families of Odontocetes: F. Delphinidae (dolphins), F. Phocoenidae (porpoises), F. Monodontidae (belugas and narwhals), and F. Physeteridae (sperm whales and pygmy sperm whales). F. Delphinidae have a beak-like snout, conical teeth, a skull that is concave from the tip of the premaxillary bone to the nasals, and flippers that are shaped like sickles. F. Phocoenidae on the other hand have spade-like teeth, a blunt rostrum, and flippers that are paddle-shaped. F. Monodontidae have skulls that in profile look flat or convex, forward-pointing conical teeth, and do not have a dorsal fin. F. Physeteridae have the most asymmetrical skull of all the Odontocetes and do not have teeth in their upper jaw.

Today in Mammalogy lab, we looked at Order Cetacea, which is in the Superorder Cetartiodactyla. Order Cetacea is one of the most highly specialized orders of mammals, as it contains whales and dolphins, which are completely aquatic. All cetaceans share distance features: they all have telescoping skull bones, which is the stretching and overlapping the skull bones that occurs when the nasals are at the top of the skull; they all have external nares on the top of the skull; they all have compressed cervical vertebrae; they all have dorso-ventrally flattened tails with horizontal flukes; and they all live in the Oceanic zone, which—broadly speaking—is all open oceans. The two suborders in Order Cetacea are Suborder Mysticeti (baleen whales) and Suborder Odontoceti (toothed whales). The main difference in these two Suborders is that, unlike Odontoceti, Mysticeti have no teeth; instead they have a filter-feeding system called a baleen, which they use to filter plankton out of the water to eat. We looked at two families within S. Mysticeti, F. Balaenidae and F. Balaenopteridae. F. Balaenidae are the right whales and bowheads, and are distinguishable by their long baleen and stock bodies, their smooth throats, and their lack of a dorsal fin. F. Balaenopteridae on the other hand are the humpback whales, mink whales, rorquals etc. These have a short baleen, a long and streamlined body, grooves on their throats, and a small dorsal fin.

As of 2015, Mustela nigripes (black-footed ferret) has been classified as endangered by the International Union for Conservation of Nature. A previous assessment in 1996 declared it “Extinct in the Wild”, but since then there have been huge efforts to reestablish wild populations. From early 2015 there have been approximately 295 wild-born individuals released into reestablished populations, however these populations are very small and restricted, and only a few of the populations at the sites where the species has been reintroduced are viable (Belant et al. 2015). As of 2015 there were 206 mature individuals existing in “self-sustaining, free-living populations” (Belant et al. 2015), but that number was continually decreasing. M.nigripes was formerly widespread in central North America, but declined to near extinction in the 20th century. This was a result of actions taken to control prairie-dog (Cynomys) populations, which the black-footed ferret is highly dependent on (Biggins and Godbey 2003, as cited by Belant et al. 2015 ), as well as the spread of canine distemper and sylvatic plague caused by Yersinia pestis (Biggins and Godbey 1995, Biggins et al. 1998, as cited by Belant et al. 2015). Black-footed ferrets are directly affected by disease through infection, and indirectly through the infection and mortality of the prairie-dogs that make up the ferrets’ entire prey base. The conversion of grasslands for agricultural uses and commercial development is also a major threat to M.nigripes, as is the decrease in genetic diversity which, along with the “concomitant increase in inbreeding” (Bronson et al. 2007, as cited by Belant et al. 2015) may lead do a decrease in the fitness of black-footed ferrets through—among other things—“immune system dysfunction and reduced reproductive success” (Bronson et al. 2007, as cited by Belant et al. 2015).

Modern horses have evolved to be adapted for environments very different to those the first equines lived in, and horses as we know them today look nothing like their earliest ancestors did when they first appeared. The first horse-like creature lived in North America and Europe about 54 million years ago, during the Eocene. Unlike modern horses, Hyracotherium boreale (also called Eohippus) was adapted for life in the woodlands and forests that dominated the Eocene. Hyracotherium was much smaller than the modern horse, and it had an arched back and raised hindquarters, a short snout, and a small cranium. It had short legs that ended in padded feet, four-toed forefeet and three-toed hind feet, and a functional hoof on each toe. Hyracotherium was a browsing animal that fed on shrubs, leaves, and branches, as evidenced by its low-crowned teeth and distinctive molars that were designed for grinding.

During the Oligocene, environmental changes occurred that started to change the local flora, and so about 33 million years ago Mesohippus bairdi appeared. Although also a forest browser, Mesohippus had a longer face and snout than Hyracotherium did, and had developed premolars that were more complex and had defined cusps. Mesohippus had three toes on both its fore and hind feet, as the fourth toe previously found on Hyracotherium was reduced to a vestigial nub, and unlike Hyracotherium Mesohippus had longer legs and a relatively straight and stiff spine that enabled it to run over hard ground.

Horses as we know them today look nothing like their earliest ancestors did when they first appeared. The first horse-like creature lived in the Nearctic and Palearcitc zones during the Eocene period, about 54 million years ago. Unlike modern horses, Hyracotherium boreale (also called Eohippus) was adapted for life in the woodlands and forests that dominated the Eocene. Hyracotherium was much smaller than the modern horse, with an arched back, a short snout, and a small cranium. Its legs were short, and ended in padded four-toed forefeet and three-toed hind feet with a functional hoof on each toe. Hyracotherium was a browsing animal that fed on shrubs, leaves, and branches, as evidenced by its low-crowned teeth and distinctive molars built for grinding. As environmental changes began to occur, Mesohippus bairdi emerged in the Oligocene approximately 33 million years ago. While also a forest browser, Mesohippus had a longer face and snout than Hyracotherium did, and developed more complex premolars with defined cusps. Mesohippus had three toes on both its fore and hind feet, as the fourth toe that Hyracotherium had was reduced to a vestigial nub, and unlike Hyracotherium, Mesohippus had longer legs and a relatively straight and stiff spine that allowed it to run over hard ground.

Rapid environmental change in the Miocene saw the coevolution of abrasive siliceous grasses and the herds of long-legged ungulates that were adapted to eat them. One such ungulate was Merychippus sejunctus, which emerged about 15 million years ago. Merychippus was taller than Mesohippus and its head morphology was much different, as Merychippus was adapted to a diet of tough grasses instead of leaves: it had an elongated muzzle with deeper jaws, and eyes that were set further back in its head to accommodate the large roots of its ever-growing teeth. In addition, to enable it to survive on its diet of abrasive grasses, Merychippus had high-crowned teeth with distinctive cusps and cement between the cusps. It was also adapted for rapid running across grasslands: the two bones in its forearm were fused to eliminate arm rotation, and although it was three-toed the outer toes were reduced while the center toe developed a large, convex hoof.

One of the last equids native to North America was Equus scotti, which lived during the Pleistocene and most resembled today’s horses. Equus scotti had a single hoof on each foot, with side ligaments to prevent twisting, and the remnants of the side toes found in earlier equines were retained as splint bones. Like Merychippus, it had high-crowned, ever-growing with complex cusps, and was well-suited for life in open grasslands.

If a skull belongs to O. Diprotodontia one way to immediately separate out two families from the rest is to look at the size of the skull: F. Petauridae and F. Acrobatidae are both types of flying-squirrel-like creatures that have the smallest skulls out of all the diprotodont orders we looked at in lab. The difference between them is that F. Petauridae has a squamosal bone (back part of the zygomatic arch) that has honeycomb-like holes in it, whereas F. Acrobatidae does not. To identify the rest of the order, looking at the angular process can help narrow down what family a skull belongs to: although most marsupials have a reflected angular process, there is one family that does not. This family is F. Phascolarctidae (koalas) which also has a long paroccipital process and selenodont teeth to accommodate its herbivorous diet. If the angular process is reflected, a possible next step is to look at the gap between the incisors and the molar row. This is called the diastema, and if it is large then it could belong to one of two families; either F. Macropodidae (kangaroos and their ilk) or F. Vombatidae (wombats). What distinguishes the two, aside from skull shape, is the fact that F. Vombatidae has 1/1 incisors—meaning that it only has one incisor on each side of its head both on the lower and upper jaw—while F. Macropodidae has 3 upper incisors that are blade-like and angled for cutting. This leaves three families, F. Pseudoceiridae, F. Phalangeridae, and F. Potoroidae, which all have similar skull shapes and sizes. F. Pseudocheiridae is the smallest, while F. Phalangeridae is the largest. F. Potoroidae and F. Phalangeridae both have enlarged premolars, however they differ in each family as they are angled outwards in F. Phalangeridae and in line with the molar row in F. Potoroidae. This leaves  F. Pseudoceiridae, which has no enlarged premolars and instead can be distinguished by its selenodont teeth.

Once identified as polyprotodont there are several ways determine what order and, subsequently, what family a skull belongs to. One way is to look at dental formula: of the polyprotodont orders we are looking at in lab, two have 4 upper incisors and 3 lower incisors on each side of their skulls(4/3), and one has 5 upper incisors and 4 lower incisors on each side of its skull (5/4) . The order that has 5/4 incisors is O. Didelphimorphia, which includes only one family, F. Didelphidae. Distinguishing between the remaining two orders can be done by looking at the canines: O. Dasyuromorphia has large canines, whereas O. Peramelemorphia has very small canines. They can also be differentiated by their sizes, as O. Dasyuromorphia is much larger than O. Peramelemorphia. Based on the families we studied in lab, if the skull belongs to O. Dasyuromorphia then it is in F. Dasyuridae, and if the skull belongs in O. Peramelemorphia then it is in F. Peramelidae.

The first step in identifying which order and family a skull in Subclass Theria belongs to is to identify its infraclass. There are two characteristics that almost all metatherians share that set them apart from eutherians: they have distinctive openings on the underside of the top part of their skulls called palatal vacuities, and the angular process (a projection at the back on the base of the mandible) is reflected, which means that it is angled inwards. In eutherians the angular process is in line with the other features of the back of the mandible (the coronoid process and the mandibular condolyte) and there are no palatal vacuities. If these features are present, the next step is to look at the teeth and identify what type of dentition is present. There are two possibilities: polyprotodont dentition and diprotodont dentition. In polyprotodont dentition, the mandible is not shortened and the lower incisors are small and unspecialized, whereas in diprotodont dentition the mandible is shortened and the first pair of lower incisors are enlarged and jut forward to meet the upper incisors. If the dentition if diprotodont the skull belongs to Order Diprotodontia, but if it is polyprotodont it could belong to Order Dasyuromorphia, Order Didelphimorphia, or Order Peramelidae.

Class Mammalia has two subclasses: Subclass Prototheria and Subclass Theria. Subclass Prototheria has only one order, Order Monotremata (monotremes), which has only two extant families. These families are F. Tachyglossidae—echidnas—and F. Ornithorhynchidae—platypuses. The second subclass, Subclass Theria, is made of up of two infraclasss: Infraclass Metatheria, which are all the marsupial mammals and Infraclass Eutheria, which includes all the placental mammals. There are in total 7 orders in Infraclass Metatheria, but in Mammalogy lab we are not including O. Paucituberculata (shrew opossums) and O. Notoryctemorphia (marsupial moles), as we have no available specimens. The orders we are focusing on are O. Diprotodontia, O. Peramelemorphia, O. Didelphimorphia, and O. Dasyuromorphia. These mammalian orders are all found in the Australian zone, with the exception of O. Didelphimorphia, which lives in the Nearctic & Neotropical zones. The seventh order is O. Microbiotheria, which only has a single species that lives in the Neotropical zone. O. Diprotodontia includes the diprotodont and syndactylous marsupials and the other three orders are polyprotodont and didactylous, with the exception of O. Peramelemorphia whose family (F. Peramelidae) are the only marsupials that are both polyprotodont and syndactylous.