Modern Animal- European Rabbit Palaeolagus Haydeni
Palaeolagus Haydeni also known as "ancient hare" is an animal that is an extinct genus of order of Lagomorpha in the family of Leporidae which closely resembles a modern day European Rabbit. Palaeolagus is around 25 centimeters (10 inches) long. The Palaeolagus fossils found are distinct under the late Eocene or Oligocene period which translate that this animal roamed the planet around 34- 24 million years ago. However, due to the size and the fragility of the Palaeolagus fossils thus currently there are only two complete bodies found in the Oligocene period of North America and Asia.

This animal is known as its bionomial name Palaeolagus Haydeni or more commonly known as a Palaeolagus which means 'ancient hares'. Its bionomial name refers to it being the ancestor of the modern- day rabbits and living during ancient times.

Palaeolagus Fossil- Source:
Palaeolagus Fossil- Source:
Scientific Classification

Labelled Diagram of The Paelaolagus Haydeni
Paelaeolagus Haydeni- Source:
Paelaeolagus Haydeni- Source:

Vertebrae of Palaeolagus Fossil- Source:
Vertebrae of Palaeolagus Fossil- Source:

Different bone structures of Palaeolagus Haydeni
Side view of Palaeolagus Fossil- Source:
Side view of Palaeolagus Fossil- Source:

21st century view of Savanna Grassland- Source:
Unlike the modern European rabbit, the Palaeolagus species did not have a distribution on all parts of the world. According to the location of most of their fossil found they are most likely to populate in savanna woodlands of the North America continent. A savanna woodland is a large and spacious area covered with grass with some trees interspersed. It has a opened canopy and usually characterized as "intermediate between grasslands and forests". Furthermore, it is predicted that the Palaeolagus species lived in a temperate climate with sufficient amount of rainfalls (wet summer, dry winter) hence the formation of grasslands accommodating to the species' main diet. Also, without the covered canopy the grassland has a full exposure to sunshine which can promise a healthy growth for the grass. However, this rich grassland can cause the Palaeolagus species to be less agile because it can be difficult for them to travel with their short hind legs which are incapable of hopping.

The Palaeolagus are found in the late Eocene or Oligocene period around 34-24 million years ago. During that period
Palaelagus inhabited today's North American continent- Source:
of Eocene the temperature generally rose nonetheless in the Oligocene period when most Palaeolagus lived marked a new cooling period. Tropics from the previous era all diminished giving way to cooler grasslands and woodlands which is the species' most possible habitat. This may also be one of the crucial factors that the modern-day European Rabbits prefers to live under a cooler environment. Today's grasslands in the North American continent has an average temperature of 17 degrees Celsius throughout the year with approximately 760 mm to 1270 mm of rainfall. Due to the fact that the Palaeolagus species lived mostly in the Oligocene period, it was most likely to be cooler than it would be today.

The Oligocene period was described by many scientists as a connector between 'the archaic world of the Eocene and a more modern ecosystem'. In the 21st century of today, many animals inhabit in the grasslands such as African Lion, American Bison, warthog and many more. It is to be believed that many of these modern animals or their ancestors existed 34 - 24 million years ago. Nonetheless, an animal that the Palaeolagus certainly have encountered is the extinct Sabertooth Cat (Smilodon) whom similarly inhabits the North American grasslands.

Just like the modern day European Rabbit, they accommodate the terrestrial ecology and habitat. But due to factors such as global
warming, compared to the European Rabbit, the Palaeolagus species live in a much cooler climate which may lead to the encounter of a very different set of animals.

In conclusion, the Palaeolagus lives in a much cooler environment than the modern day European Rabbit hence some of their unique adaptation have evolved throughout the long period of time within.

Structural Adaptation

Short Body
Compared to the modern day European Rabbit, the Palaeolagus is much smaller in size standing at only 25 cm hence its
corresponding body length is much shorter too. This structural adaptation would help the animal to live in its grassland environment helping it to survive where larger animals such as ancestors of lions, bisons and warthogs may have lived.
Being so small it gives an advantage of being capable to travel swiftly through the rich grasslands despite its short hind legs which leads to its incapability of hopping. Also its small size makes it hard to spot within the grasslands with grass growing up to 3 meters tall, if it was any larger it may simply become an easy target for larger predators especially those that roams in the sky. Their sizes promise a decrease in chance to be spotted, consequently means it has an increase of chance for better survival and assure the survival of the Palaeolagus species. Furthermore, because its body is so close to ground level it is easy to chew on the root of the grass. The environment pressure of this adaptation is mostly due to its grassland habitat, being around so many variety of predators its small size gives it an advantage of being less likely to be spotted and higher chance of survival.

Short Hind Legs
One of the most significant difference between the modern day European Rabbit and the Palaeolagus species is the hind legs. The European Rabbits' hind legs is the most important part of their body, helping it in every aspect of their daily life such as travelling (hopping), digging burrows etc... However the Palaeolagus species' short hind legs is incapable of hopping instead they ran on all on its four limps just like a rodent in a creeping fashion much like the ground squirrel. Being so close to the ground level, the Palaeolagus species was very agile and was able to travel swiftly through the grasslands. When they are being chased by predators, they tend to press their bodies against the ground as close as possible to enable their run to be smoother dashing through the grasslands. Also, because of their short hind legs carrying its corresponding small body they tend to outrun their predators enabling them to find a place to hide (eg. burrows) before the predators could get to it. In short, their short hind legs' advantage is allowing it to run swiftly through the grasslands before their predators could launch attack. The environment pressure would be the disadvantage of the Palaelagus being so small and under threat by other large animals that roam the grasslands hence having short hind legs allow them to run swiftly and increase the chance of survival.

Behaviour Adaptation

Social Interaction
Compared to other varieties of animals such as the Common Vampire Bats, the Palaeolagus species lived in a much smaller group however several colonies may live in the same burrows. Living in burrows not only provided warmth but provided them especially the youth with protection and a sense of security. This is crucial because just like its descendants, the Palaeolagus species are very careful animals. Due to the fact that newborn babies can only start taking care of themselves at four months old hence during that period of time their parents (usually the doe) has a difficult time to find sufficient amount of food and take care of its youth at the same time. In result of the close bonding developed by social interaction, another doe may take over as the ‘mother’ role and look after the babies while the rabbit can search for food and her babies will be secured back at the burrow. Furthermore, being in a group can allow the Palaeolagus species to find food in a safer environment. Although they have sensitive hearing, they also have poor vision thus it cannot efficiently acknowledge the presence of a potential threat but if they find food in a small group and once an individual sense danger it will begin to thump their hind legs. Upon hearing the thumping, the rest of the group will know there is danger around and quickly run for shelter. The environment pressures are the need for an animal to eat in order to maintain healthy and fit for survival and also the nature of youth needing the care of parents.

Nocturnal; Active at Night
Like the Common Eel, the Palaeolagus is a type of nocturnal animal meaning it is active at night and sleeps during daytime. Being very careful animals, the Palaeolagus only came out during nighttime to eat and hides in their burrows most of the time limiting the possibilities to encounter any threat or potential danger. This would be a very useful adaptation because generally a larger variety of animals are active in the daytime than in the dark. Also, small creatures such as the Palaeolagus species were hard to spot in the pitch dark environment and their size allowed the advantage of being able to run swiftly among the bushes away from its predators. Moreover, because of their poor vision the light was not much of an aid hence they depended greatly on their sensitive ears, carefully listening to any potential danger in the distance and giving it information about the shape, size and direction. On top of that, the Palaeolagus species may enjoy the cool temperature and the still air allowed them to pick up scents of predators or food source. The environment pressure would be the key to survival, being in the dark allowed the Palaeolagus species to feed/ eat in a less dangerous environment with the dark helping it to camouflage. Basically it helps to increase the chance of survival for the species.

Psychological Adaptation

Warm- Blooded
The Palaeolagus species just like the European Rabbits were classified under the mammals category hence it also means that it is a type of warm-blooded animal. In more specific terms, the Palaeolagus were endothermic homeotherms which state that they were capable of maintaining constant internal warm body temperature. Like all other warm-blooded animals, they need to eat a large amount of food to convert the energy into warmth. Most of the food consumed is to be used to maintain body warmth and only a small amount is converted into body mass. Being a warm blooded animal, the self-generated heat helps it to keep warm and maintain body temperature to survive in the extreme cold weather. Furthermore, warm blooded animals are known to have a greater stamina because their metabolism has to regenerate at a quick speed to accommodate the energy supplies. Also, being able to keep warm and prevent heat loss at all times the Palaeolagus can easily search for food during nighttime while competing cold blooded animals will not be able to afford to move around. The environment pressure is the need for the species to self-generate and maintain body heat to keep warmth in order to compete for food in the wild. Also, another factor may be living in the wild the species' small size is very much at disadvantage hence finding food may be difficult thus being warm can also help with conserving energy allowing the animal to decrease the needs of finding food.

Extinction Pressures
After the Oligocene Epoch, the geological epoch of Miocene followed. During the Miocene Epoch, scientists acknowledged that many varieties of animals were fairly modern and well-developed and also within the period of time was when the event of Middle Miocene disruption occurred. Scientists believed that in this occurrence, a large number of land and aquatic species were swiped and some even reckoned up to approximately 30% of animals uniquely from the genus of mammalia have disappeared. Although the scientists do not know what is the significant reason why the Palaeolagus species became extinct however during this period of time (15 million years ago) Earth encountered a sudden decrease of temperature reflected by the increase of ice caps in Antarctica. The extreme cold climate affected life from the land and aquatic environment and may also be the most well-documented reason for the extinction of Palaeolagus species and many others. The animals were not able to adapt to the rapid fluctuation in temperature.
The environment pressure would be the key to survival, being in the dark allowed the Palaeolagus species to feed/ eat in a less dangerous environment with the dark helping it to camouflage. Basically it helps to increase the chance of survival for the species.

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