![]() body size increases), but others only slowly (jaw structure and function).įinally, we were surprised that whilst mammals were hit hard by the K/Pg mass extinction event (many species and whole subgroups became extinct) they nonetheless maintained their jaw disparity. We think this means that evolution can make some changes rapidly (e.g. Second, extinction of the dinosaurs allowed them to expand beyond this, but only slowly compared to the speed with which they increased their body size range and species numbers. They were restricted to small body sizes, from mouse- to badger-sized, but they really ruled the roost at those sizes, perhaps doing much of what they do today. Firstly, we think this shows that mammals from the times of dinosaurs were actually very disparate. We proposed several take-home messages from this. Indeed, mammals waited much longer, around 15 million years, during an interval of time known as the Eocene, before their disparity of jaws expanded beyond what was seen in the age of dinosaurs. So this formative burst of mammalian evolution had occurred, but from the perspective of jaws and diets, little had changed. And early relatives of key living groups appeared. Large-bodied mammals appeared for the first time. Mammals dramatically increased their species counts and abundance in ecosystems. Why were we surprised? Well, because many other things did change in this time. Indeed, we were surprised to find that mammalian jaw disparity did not increase at all during the first 10 million years after the extinction of dinosaurs. Our analyses showed that mammals had quite high disparity during the times of dinosaurs. Jaws work like levers or beams, and she chose measurements that describe mechanical advantage, bending strength, and other key functional properties with close relationships to how mammals eat. To answer these questions, Dr Benevento measured jaws from a few hundred species. But how much disparity was present among mammals from the times of dinosaurs? And what happened to mammal jaws after the extinction of dinosaurs? Did mammals expand their disparity of jaw types (and, by implication, their disparity of diets)? By how much? And how quickly? Today’s mammals, and their jaws, show lots of disparity. We call this variation ‘disparity’, and use it as a way of inferring how much variation in dietary ecologies there might have been among species in the past. More variation in fossil jaws equals more variation in ancient diets. Jaws are important to the business of being a mammal: their structure can tell a lot about the foods that are eaten, and the amount of variation in jaw structure among species relates to the amount of variation in diets among these mammals. She studied the jaw structure of mammal species spanning a large chunk of their early evolution: from about 200 million years ago up to 50 million years ago. This week, my former DPhil student, Dr Gemma Benevento published a study that aims to understand this, in collaboration with myself and our colleague Matt Friedman. They also ate a wide range of different foods, including insects, plants, and other vertebrates, and some even ate dinosaurs! So how different really were they to the mammals of today? These showed that these early mammals actually had a wide range of ecologies: They included mole-like diggers, beaver-like swimmers, climbers, gliders and others. Fossil discoveries of the past decade included whole skeletons from several continents, and especially from China. ![]() For a long time, mammals from the age of dinosaurs were known almost solely from teeth. However, nothing is ever simple, and quantitative studies have a great potential to answer questions about evolutionary history. Artwork by Julius CsotonyiĪll of this seems well known. © Oxford University Museum of Natural History. ![]() St Edmund Hall Association Show submenu for St Edmund Hall AssociationĪn example of a mammal from the age of the dinosaurs.Keep in Touch Show submenu for Keep in Touch.Get Involved Show submenu for Get Involved.Support the Hall Show submenu for Support the Hall.Conferences, Meetings and Summer Schools.Weddings, Civil Ceremonies and Receptions.Conferences and Weddings Show submenu for Conferences and Weddings.Oxford Chinese Economy Programme (OXCEP).Global Public Seminars in Comparative and International Education.Conversations in Environmental Sustainability: beyond greenwashing.Explore Teddy Hall Show submenu for Explore Teddy Hall.Creative Writing Show submenu for Creative Writing.Our Community Show submenu for Our Community.College Life Show submenu for College Life.Visiting Students Show submenu for Visiting Students.Postgraduate Study Show submenu for Postgraduate Study.Undergraduate Study Show submenu for Undergraduate Study.
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