Scientists Explain the Evolution of Large Dinosaur

Scientists have developed computer models of the bodies of sauropod dinosaurs to examine the evolution of their body shape. Scientists of the University of Liverpool have developed computer models of the bodies of sauropod dinosaurs to examine the evolution of their body shape.

Sauropod dinosaurs include the largest land animals to have ever lived. Some of the more well-known sauropods include Diplodocus, Apatosaurus and Brontosaurus. They are renowned for their extremely long necks, long tails as well as four thick, pillar-like legs and small heads in relation to their body.

To date, however, there have been only limited attempts to examine how this unique body-plan evolved and how it might be related to their gigantic body size. Dr. Karl Bates from Department of Musculoskeletal Biology and his colleagues used three-dimensional computer models reconstructing the bodies of sauropod dinosaurs to analyze how their size, shape and weight-distribution evolved over time.

Source: Science Daily

Decline of Early Crocodile Helped the Early Marine Turtle

Marine turtles experienced an evolutionary windfall thanks to a mass extinction of crcodyliforms around 145 million years ago. 

Crocodyliforms comprise modern crocodiles and alligators and their ancient ancestors, which were major predators that thrived on Earth millions of years ago. They evolved into a variety of species including smaller  ones that lived on land through to mega-sized sea-swimming species that were up to 12 metres long. However, around 145 million years ago crocodyliforms, along with many other species, experienced a severe decline -- an extinction event during a period between two epochs known as the Jurassic/Cretaceous boundary. 

During this boundary up to 80 percent of species on land and in marine environments were wiped out . This decline was primarily due to a drop in sea level, which led to a closing off of shallow marine environments such as lagoons and coastal swamps. These were the homes and primary hunting grounds for may crocodyliforms. The decimation of many marine crocodyliforms may also have laid the way for their ecological replacement by other large predatory groups such as modern shark species  and new types of plesiosaurs. Plesiosaurs were long-necked, fat-bodied and small headed ocean-going creature with fins, which later went extinct around 66 million years ago.

Other factors that contributed to the decline of marine crocodyliforms included a change in the chemistry of ocean water with increased sulphur toxicity and a depletion of oxygen. While primitive crocodilyform species on land also suffered major declines, the remaining species diversified into new groups such as  the new extinct notosuchians, which were much smaller in size at around 1.5 metres in length. Eusuchians also came to prominence after the extinction which led to today's crocodiles.

For this research work the researchers analyzed almost 1,200 crocodyliforms fossil records.

Source: Biological Science

Most Big Animals Tried Grass but Many Switched Diet or Extinct

As grasses grew more common in Africa, most major mammal group tried grazing on them at times during the past four million years, but some of the animals went extinct or switched back to browsing on trees and shrubs.

Jurassic Saw the Fastest Evolution of Mammals

A report of a research published in Current Biology says that the fastest mammal evolution occurs in the Jurassic period.

Early mammals lived alongside dinosaurs during the Mesozoic Era (252 - 66 Million years ago). They were thought to be exclusively small, nocturnal and insect-eaters but fossils discoveries of the past decades, especially from China and South America, shows that they developed diverse adaptation for feeding and locomotion, including gliding, digging and swimming. 

To find the how rapidly the evolution happens they did a large-scaled analysis of the skeleton and dental changes of the Mesozoic mammals. By calculating, the researchers found the evolution reaches its peak at the Jurassic period (200-145 million years ago).

The team comprised researchers from Oxford University and Macquarie University. Dr. Roger Close of Oxford University is the lead author of this report.  

lower-oxygen oceans will shift marine habitats

Warming temperatures and decreasing levels of dissolved oxygen will act together to create metabolic stress for marine animals. Habitats will shift to places in the ocean where the oxygen supply can meet the animals' increasing future needs. 

 

University of Washington researchers and collaborators have found that the same principle will apply to marine species under global warming. The warmer water temperatures will speed up the animals' metabolic need for oxygen, as also happens during exercise, but the warmer water will hold less of the oxygen needed to fuel their bodies, similar to what happens at high altitudes.

The study, published June 5 in Science, finds that these changes will act together to push marine animals away from the equator. About two thirds of the respiratory stress due to climate change is caused by warmer temperatures, while the rest is because warmer water holds less dissolved gases.

The study centered on four Atlantic Ocean species whose temperature and oxygen requirements are well known from lab tests: Atlantic cod that live in the open ocean; Atlantic rock crab that live in coastal waters; sharp snout seabream that live in the subtropical Atlantic and Mediterranean; and common eelpout, a bottom-dwelling fish that lives in shallow waters in high northern latitudes.

Deutsch used climate models to see how the projected temperature and oxygen levels by 2100 due to climate change would affect these four species' ability to meet their future energy needs. If current emissions continue, the near-surface ocean is projected to warm by several degrees Celsius by the end of this century. Seawater at that temperature would hold 5-10 percent less oxygen than it does now.

Results show future rock crab habitat would be restricted to shallower water, hugging the more oxygenated surface. For all four species, the equator-ward part of the range would become uninhabitable because peak oxygen demand would become greater than the supply. Viable habitats would shift away from the equator, displacing from 14 percent to 26 percent of the current ranges.

The four animals were chosen because the effects of oxygen and temperature on their metabolism are well known, and because they live in diverse habitats. The authors believe the results are relevant for all marine species that rely on aquatic oxygen for an energy source.

Previously, marine scientists thought about oxygen more in terms of extreme events that could cause regional die-offs of marine animals, also known as dead zones.

Source: Science Daily

Fossil of huge 'walking' bat discovered in New Zealand

The new species, Mystacina miocenalis, was described today in the journal PLOS ONE, and is related to another bat, Mystacina tuberculata, which still lives in New Zealand's old growth forests.

Mystacina tuberculata foraging on South Island, New Zealand.

The fossils were found near Central Otago on South Island, in sediment left over from a vast prehistoric body of water known as Lake Manuherikia, which was part of warmer subtropical rainforest during the early Miocene era, between 16 and 19-million-years-ago.

Bats, belonging to the Mystacina genus, were believed to have an ancient history in New Zealand, but until now, the oldest fossil of a Mystacina bat in New Zealand was from a cave in South Island, dating to 17,500 years ago. This latest discovery forces a rethink of when these peculiar, walking bats first crossed the ditch, arriving from what is present-day Australia.

The new species has similar teeth to its contemporary relative, suggesting a broad diet that included nectar, pollen and fruit, as well as insects and spiders. Limb bones found in the deposit also showed similar structures specialised for walking.

Where they differ is body size: at an estimated 40 grams, the fossil bat is roughly three times heavier than its living cousin, and the average weight of more than 900 living bat species.

The research team also found a diverse array of plant, animal and insect fossils at the site, which shows that the 16-million-year-old subtropical ecosystem bore resemblance to the more temperate one that exists today.

Source: Science Daily