DOCSLIB.ORG

An Explosion of Fossil Finds Is Allowing Our Early Mammal Ancestors to Leap out of the Shadow of the Dinosaurs

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
An Explosion of Fossil Finds Is Allowing Our Early Mammal Ancestors to Leap out of the Shadow of the Dinosaurs Feature This rat-sized Liaoconodon hui is one of many fossils from northern China that are sharpening the picture of how mammal traits evolved. THE MAKING OF MAMMALS An explosion of fossil finds is allowing our early mammal ancestors to leap out of the shadow of the dinosaurs. By John Pickrell ight is falling in the early Jurassic dug up the block and shipped it back to the cusp of mammalhood — and researchers say 185 million years ago, and the Kay- laboratory for safekeeping. It wasn’t until that it provides crucial insights into which traits entatherium is tending to her newly nine years later that a specialist preparing the define mammals and which were present in hatched brood. Heavy rains pum- fossil for study noticed something startling: their earlier relatives. mel the bank above her den as she embedded in the block were tiny teeth, and Kayentatherium’s skeleton is mammal-like looks over her dozens of tiny young. jawbones just 1 centimetre in length. “Immedi- in many ways, but the fossil suggested that it She is about the size of a large cat ately they stopped the preparation and thought still reproduced very much like a reptile, giving and could easily pass for a mammal, about ways of non-destructively examining birth to large litters of small-brained offspring. Nbut her large jawbone, characteristic teeth and the babies,” says Eva Hoffman, at Texas with By contrast, “mammal moms invest a lot in a lack of external ears give her away: she is a cyno- Rowe at the time and now a palaeontologist smaller number of babies, each of which has dont, a member of the group from which mam- at the American Museum of Natural History a better chance of surviving”, says Hoffman. mals evolved. At some point without warning, in New York City. Instead of breaking into the Mammal babies spend longer under their the sodden bank collapses, entombing the rock, Hoffman and Rowe digitally extracted parents’ care, developing relatively large hatchlings and their mother in mud. the bones with a microcomputed tomography brains, whereas these fossil hatchlings had There they remained until the summer of (microCT) scanner, which uses X-rays to create well-developed bones and teeth, hinting that 2000, when a fossil-hunting crew led by Tim- fine-grained 3D images. they could fend for themselves and were not othy Rowe at the University of Texas at Austin What they found inside the rock were the first nourished by milk, as all mammals are today. 2011 , 181–185; 472 chanced upon their scattered bones among known babies of mammals or their relatives The find is among a mass of discoveries rocks of the Kayenta Formation in northern from the Jurassic — and not just one, but 38 of in the past 10–20 years that are illuminating Arizona. them, placing this among the most significant milestones in mammalian evolution. Although ET AL. NATURE That initial encounter with the fossils did discoveries related to mammal origins made major finds are emerging all over the world, 1 little to impress the palaeontologists. They in the past decade . Kayentatherium is at the the largest number are coming out of China; J. MENG 468 | Nature | Vol 574 | 24 October 2019 ©2019 Spri nger Nature Li mited. All ri ghts reserved. ©2019 Spri nger Nature Li mited. All ri ghts reserved. together, they have overturned the now dated interested in understanding the evolution of belong to long-extinct subgroups, says Meng. belief that dinosaur-era mammals were small, the mammalian ear, for instance. In contrast to the panoply that existed in the unremarkable insectivores, eking out a life in The finds overturned previous dogma. “We Mesozoic, mammals today come in just three the shadows of the giant reptiles. used to say that during the time of dinosaurs, varieties: placentals, which make up the major- The fossils have revealed that early mammals mammals were totally unspectacular. That they ity of species and include humans; marsupials, were ecologically diverse and experimenting were just these little mousey things scamper- such as kangaroos and koalas, in which gesta- in gliding, swimming, burrowing and climbing. ing around in the shadows,” says Brusatte. But tion in the womb is brief and development The discoveries are also starting to reveal the these animals “were undergoing their own continues in a pouch; and the egg-laying mono- evolutionary origins of many of the key traits evolutionary explosion”, he says. tremes, represented only by the platypus and of mammals — such as lactation, large brains Mammals first appeared at least 178 million several echidnas. “But in geological history, and superbly keen senses. years ago, and scampered amid the dinosaurs there were many other groups such as multitu- “The explosion of early-mammal discover- until the majority of those beasts, with the berculates, triconodonts and haramiyids,” says ies, particularly from China, over the last two exception of the birds, were wiped out 66 mil- Meng. “Mammals were actually very diverse in decades has been eye-opening, mind-numbing lion years ago. But mammals didn’t have to wait the Jurassic.” and absolutely dazzling,” says David Krause, for that extinction to diversify into many forms Some, such as the shrew-like Juramaia — a vertebrate palaeontologist at the Denver and species. “These new discoveries document described by Luo’s team in 2011 and dated to Museum of Nature and Science in Colorado. a huge, hitherto-undreamed-of ecological 160 million years ago — are among the earliest This avalanche of discovery is also stirring up diversity,” says Richard Cifelli, a palaeontolo- placental mammals and therefore have the debate: some researchers disagree over which gist at the University of Oklahoma in Norman. potential to be our ancestors11. fossil groups are true mammals and the shape Among the first innovations that researchers And a few dinosaur-era mammals were of the mammal family tree. “We want to under- began to find in fossil form were those to much bigger than suspected, too. Repe- stand our early history in the language of evolu- do with locomotion. In 2006, Meng’s team nomamus was 12–14 kilograms, and the tionary biology, and that’s what fires me up,” says reported the first gliding mammal3, 164-mil- racoon-sized Vintana weighed in at 9 kg. “It’s Zhe-Xi Luo, a palaeontologist at the University lion-year-old Volaticotherium, which had wing exciting that we kind of busted the old myths of Chicago in Illinois. “That’s why this entire membranes made of furry skin, like today’s that early mammals came from a very humble field is so interesting, because the fossil record flying squirrels. In 2017, Luo’s team added generalized ancestor,” says Luo. is getting better and better, and we are starting Vilevolodon and Maiopatagaium4,5, which The finds are not solely from China. Important to really tackle some of these questions.” fossils are also coming from the United States, Spain, Brazil, Argentina, Madagascar and Mon- Out of the shadows golia. Some of the most intriguing and oldest In 1824, at the Geological Society of London, “THESE NEW fossils — as well as the biggest gaps in our knowl- naturalist William Buckland presented bones DISCOVERIES edge — relate to the southern continents, where from one of the first known dinosaurs, Megalo- only five genera of Mesozoic mammals and their saurus. At the same talk, he revealed tiny mam- DOCUMENT A relatives are known, compared with more than malian jaws that had been found in the same 70 genera from northern latitudes. In the past fossil deposit. Their presence suggested that HUGE, HITHERTO- two decades, Brazil has yielded several Trias- mammals had a very deep history, but as would sic fossils that are more than 200 million years happen repeatedly, the dinosaur discoveries UNDREAMED-OF old. Guillermo Rougier, a palaeontologist at the completely overshadowed the mammal ones. University of Louisville in Kentucky, describes The slow trickle of mammal finds from ECOLOGICAL DIVERSITY. them as “incredible discoveries” that are right around the world continued for 150 years. Then on the cusp between mammals and their cyno- in 1997, researchers described the first ancient dont ancestors. “These forms really show a very mammal from the fossil-rich rocks of Liaoning transitional progression from things that are in northeastern China2, and the floodgates lived at around the same time and belonged typically non-mammalian, to things that pretty opened. Since then, 50 or more near-complete to a group called the haramiyids. These animals much have all the features of early mammals.” and “beautiful specimens” have been found swooped between the trees alongside some there, according to Jin Meng, a palaeontologist of the first flying dinosaurs, taking advantage Mammal must-haves at the American Museum of Natural History. of previously unexploitable food resources. The latest finds are also offering clues to Like the dinosaur fossils, they are dug up by Researchers found other specializations the evolution of key mammal features. For local farmers and sold on to museums. that they assumed had evolved only later: instance, the keen hearing of mammals is But the dinosaurs continued to get the vast Agilodocodon could climb trees and gnawed partly down to tiny bones in the middle ear — majority of the attention, says palaeontologist into bark to feast on sap6; the platypus-sized the malleus, incus and ectotympanic. But in the Steve Brusatte at the University of Edinburgh, river-dweller Castorocauda had webbed feet reptilian ancestors of mammals, these bones UK. “It’s only that very recently, through and a beaver-like tail for swimming7; and Doco- were part of the jaw, and were used for chewing the work of Luo, Meng and others, that the fossor had paws and claws for digging, and instead of hearing.
Load more

Recommended publications
  • Reptile-Like Physiology in Early Jurassic Stem-Mammals
    bioRxiv preprint doi: https://doi.org/10.1101/785360; this version posted October 10, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Title: Reptile-like physiology in Early Jurassic stem-mammals Authors: Elis Newham1*, Pamela G. Gill2,3*, Philippa Brewer3, Michael J. Benton2, Vincent Fernandez4,5, Neil J. Gostling6, David Haberthür7, Jukka Jernvall8, Tuomas Kankanpää9, Aki 5 Kallonen10, Charles Navarro2, Alexandra Pacureanu5, Berit Zeller-Plumhoff11, Kelly Richards12, Kate Robson-Brown13, Philipp Schneider14, Heikki Suhonen10, Paul Tafforeau5, Katherine Williams14, & Ian J. Corfe8*. Affiliations: 10 1School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, UK. 2School of Earth Sciences, University of Bristol, Bristol, UK. 3Earth Science Department, The Natural History Museum, London, UK. 4Core Research Laboratories, The Natural History Museum, London, UK. 5European Synchrotron Radiation Facility, Grenoble, France. 15 6School of Biological Sciences, University of Southampton, Southampton, UK. 7Institute of Anatomy, University of Bern, Bern, Switzerland. 8Institute of Biotechnology, University of Helsinki, Helsinki, Finland. 9Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland. 10Department of Physics, University of Helsinki, Helsinki, Finland. 20 11Helmholtz-Zentrum Geesthacht, Zentrum für Material-und Küstenforschung GmbH Germany. 12Oxford University Museum of Natural History, Oxford, OX1 3PW, UK. 1 bioRxiv preprint doi: https://doi.org/10.1101/785360; this version posted October 10, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 13Department of Anthropology and Archaeology, University of Bristol, Bristol, UK. 14Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK.
    [Show full text]
  • O Esqueleto Pós-Craniano De Exaeretodon Riograndensis Abdala Et Al
    Rev. bras. paleontol. 10(2):79-94, Maio/Agosto 2007 © 2007 by the Sociedade Brasileira de Paleontologia O ESQUELETO PÓS-CRANIANO DE EXAERETODON RIOGRANDENSIS ABDALA ET AL. (CYNODONTIA, TRAVERSODONTIDAE), TRIÁSSICO DO BRASIL TÉO VEIGA DE OLIVEIRA, CESAR LEANDRO SCHULTZ & MARINA BENTO SOARES Instituto de Geociências, UFRGS, Avenida Bento Gonçalves, 9500, 91501-970, Porto Alegre, RS, Brasil. [email protected], [email protected], [email protected] RESUMO – Pela primeira vez, elementos pós-cranianos de Exaeretodon riograndensis, um cinodonte traversodontídeo da Cenozona de Rhynchosauria da Formação Santa Maria, Neotriássico do sul do Brasil, são descritos e comparados com E. frenguellii e outros cinodontes não-mamalianos. O material inclui parte da coluna vertebral, radio, ulna e elementos da cintura pélvica. As diferenças mais significativas em relação a E. frenguellii estão na morfologia e nas dimensões do arco neural do atlas, na presença de intercentros em vértebras cervicais posteriores ao áxis e na ausência da dilatação do ápice do espinho neural das vértebras truncais. A morfologia da região sacral da coluna, do rádio, da ulna e da cintura pélvica são concordantes com o observado em E. frenguellii. A comparação com outros táxons de cinodontes não-mamalianos permite a observação da nítida evolução em mosaico do esqueleto pós-craniano destes animais: E. riograndensis mostra alguns caracteres similares a outros Cynognathia (grupo ao qual pertence), enquanto outros são mais próximos aos observados em alguns Probainognathia (incluindo mamíferos), como a natureza mais avançada do complexo atlas-áxis. Palavras-chave: Triássico, Brasil, Formação Santa Maria, Traversodontidae, Exaeretodon riograndensis, pós-crânio. ABSTRACT – THE POSTCRANIAL SKELETON OF EXAERETODON RIOGRANDENSIS ABDALA ET AL.
    [Show full text]
  • Recent Advances in Studies on Mesozoic and Paleogene Mammals in China
    Vol.24 No.2 2010 Paleomammalogy Recent Advances in Studies on Mesozoic and Paleogene Mammals in China WANG Yuanqing* and NI Xijun Institute of Vertebrate Paleontology and Paleoanthropology, CAS, Beijing 10004, China ike in other fields of paleontology, research in from the articular of the lower jaw and the quadrate of the paleomammalogy mainly falls into two aspects. cranium following the process of reduction and detachment LOne is related to the biological nature of fossil from the reptilian mandible, are new elements of the bony mammals, such as their systematics, origin, evolution, chain in the mammalian middle ear. The appearance of phylogenetic relationships, transformation of key features mammalian middle ear allows mammals to hear the sound and paleobiogeography, and the other is related to the of higher frequencies than reptiles do. Generally speaking, geological context, involving biostratigraphy, biochronology, a widely accepted hypothesis is that mammals originated faunal turnover and its relations to the global and regional from a certain extinct reptilian group. The formation and environmental changes. In the last decade, a number of development of the definitive mammalian middle ear well-preserved mammalian specimens were collected from (DMME) has thus become one of the key issues in the study different localities around the country. Such discoveries have of mammalian evolution and has drawn the attention from provided significant information for understanding the early many researchers for many years. evolution of mammals and reconstructing the phylogeny of Developmental biological studies have proven the early mammals. function of the Meckel’s cartilage and its relationship to Studies of Chinese Mesozoic mammals achieved the ear ossicles during the development of mammalian remarkable progress in the past several years.
    [Show full text]
  • Mammalian Origins Major Groups of Synapsida
    Mammalogy 4764 9/16/2009 Chapter 4 “Reptile” Mammalian Origins Early mammal Carnivore Amniota Herbivore Feldhamer Table 4.1 Savage and Long 1986 Major Fig. 3.2, Vaughn, Fig. 4.1, Feldhamer groups Mammalian Origins of Dimetrodon Overview Synapsida Synapsids Pelycosaurs and Therapsids First Mammals Mesozoic Era appear Feldhamer Fig. 4.2 Cenozoic Era radiate Savage and Long 1986 Pelycosaur Skull, jaw musculature, and teeth Cynodontia -- Advanced, predaceous therapsids Pelycosaur Scymnognathus Cynognathus Therapsid Early Cynodont Derived Therapsid/Mammal Primitive Late Cynodont Fig. 3.2, Vaughn Thrinaxodon Fig 4.3 & 4, Feldhamer 1 Mammalogy 4764 9/16/2009 Skeletal transition Extinction of Cynodonts Possibly competition from dinosaurs Pelycosaur Early Cynodonts were dog-size, last surviving were squirrel sized Fig. 4.15 Mammals that survived while Cynodonts went extinct (contemporary) were mouse-sized. Cynodont Thrinaxodon Modern Mammal Fig. 3.5, Vaughn Fig. 4.16c, Early Cynodont Early mammals Changes in land masses Feldhamer 4.11 200 - 250 million years ago Derived characters: Dentary/squamosal jaw articulation Diphyodont dentition 200 MYA 180 MYA Mammary glands Secondary palate Early Mid- Viviparity (loss of eggshell) When? Jurassic Jurassic 65 MYA 135 MYA Early Early Cretaceous Cenozoic Feldhamer 4.5, 4.9 Skull and teeth of mammals 2 Mammalogy 4764 9/16/2009 Teeth and Dentition of Mammals Teeth Heterodont teeth with different functions Differentiated on the basis of function, resulting in increased One of the major keys efficiency acquiring and digesting food. to success of mammals Teeth occur in 3 bones of skull: Teeth of mammals are premaxilla, maxilla, dentary extremely variable with different diets -- more than other taxa Feldhamer et al.
    [Show full text]
  • Femur of a Morganucodontid Mammal from the Middle Jurassic of Central Russia
    Femur of a morganucodontid mammal from the Middle Jurassic of Central Russia PETR P. GAMBARYAN and ALEXANDER 0.AVERIANOV Gambaryan, P.P. & Averianov, A.O. 2001. Femur of a morganucodontid mammal from the Middle Jurassic of Central Russia. -Acta Palaeontologica Polonica 46,1,99-112. We describe a nearly complete mammalian femur from the Middle Jurassic (upper Bathonian) from Peski quarry, situated some 100 km south east of Moscow, central Rus- sia. It is similar to the femora of Morganucodontidae in having a globular femoral head, separated from the greater trochanter and reflected dorsally, fovea capitis present, both trochanters triangular and located on the same plane, distal end flat, mediolaterally expanded, and somewhat bent ventrally, and in the shape and proportions of distal condyles. It is referred to as Morganucodontidae gen. et sp. indet. It is the first representa- tive of this group of mammals in Eastern Europe from the third Mesozoic mammal local- ity discovered in Russia. Exquisite preservation of the bone surface allowed us to recon- struct partial hind limb musculature. We reconstruct m. iliopsoas as inserting on the ridge, which starts at the lesser trochanter and extends along the medial femoral margin for more than half of the femur length. On this basis we conclude that the mode of loco- motion of the Peski morganucodontid was similar to that of modern echidnas. During the propulsive phase the femur did not retract and the step elongation was provided by pronation of the femur. Key words : Mammalia, Morganucodontidae, femur, anatomy, locomotion, Jurassic, Russia. Petr P. Gambaryan [[email protected]] and Alexander 0.
    [Show full text]
  • I Found a Baby Mammal Now What?
    I Found a Baby Mammal Now What? To Find a wildlife Is baby animal hurt or sick rehabilitator in your area, (bleeding, shivering, vomiting; contact No was attacked by cat/dog?) •Your state wildlife agency •Humane Society Yes Can you find the nest or den? •Audubon Society Is it intact? •Wild bird stores •City Animal control officer •Veterinarian (wildlife/exotic) Yes No Call a wildlife rehabilitator. •Coast Guard or Marine Patrol •US Fish & Wildlife Service Place baby in Place baby in •Wildlife Rehab Info Directory: nest/den. shallow box close to (wildliferehab.virtualave.net) where it was found. Keep it warm but out of Unable to reach a wildlife rehabilitator? sun. Call your state wildlife agency or a wildlife Veterinarian. A baby’s Watch for mother for best chance 4-6 hours. for survival Stay completely out of sight. is its mother Mothers won’t return if any people or pets are present. If you are unable to reach any of the Above, see instructions on back of this page: “How to rescue Baby Mammals” Did the Mother return? Yes No Leave the area. Call a wildlife Baby is OK. rehabilitator. If you find a seal pup or fawn: If you find baby bunnies: •Mothers normally leave their babies to feed. •If their nest has been damaged it can be repaired. Look for a •If baby looks cold, hungry, diseased, or shallow depression lined with grass/fur. Place babies in nest with confused, or if dogs, other animals, or people light layers at grass to hide them. Leave the area, or the mother threaten its safety, call a wildlife rehabilitator won’t return.
    [Show full text]
  • Evolution of the Mammalian Fauces Region and the Origin of Suckling
    Evolution of the mammalian fauces region and the origin of suckling The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Crompton, Alfred, Catherine Musinsky, Jose Bonaparte, Bhart- Anjan Bhullar, and Tomasz Owerkowicz. Evolution of the mammalian fauces region and the origin of suckling (2018). Citable link https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37364482 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA 1 Evolution of the mammalian fauces region and the origin of suckling Alfred Crompton1†, Catherine Musinsky1, Jose Bonaparte2, Bhart-Anjan Bhullar3, Tomasz Owerkowicz4 1: Harvard University, Organismic and Evolutionary Biology Department, Museum of Comparative Zoology, 26 Oxford St, Cambridge, MA 02138 USA 2: Museo Municipal de C. Naturales "C. Ameghino", 6600 MERCEDES – BS. AS. Argentina 3: Department of Geology & Geophysics, Yale University, PO Box 208109, New Haven, CT 06520- 8109 USA 4: Department of Biology, California State University in San Bernadino, 5500 University Pkwy, San Bernardino, CA 92407 USA †corresponding author: ORCID 0000-0001-6008-2587, [email protected], 617-495-3202 Acknowledgments Thanks to Dr. Edgar Allin for his comments on an early draft of this paper. Thanks to the Museum of Comparative Zoology, its Director, Professor James Hanken, and to the Center for Nanoscale Systems at Harvard University for providing the facilities and finances for this research.
    [Show full text]
  • The History of the World in Comics
    TABLE OF CONTENTS Earth Is Born 6 THE CENOZOIC 43 On the Prairies 44 THE PRECAMBRIAN 7 In the Trees 45 The Cradle of Life 8 Little Horses 46 The First Cells 9 The New Giants 47 A World of Microbes 10 Walking Whales 48 Upheavals 1 1 Swimming Whales 49 The First Faunas 12 Trumpeters 50 Island America 5 1 THE PALEOZOIC 13 The Rise of the Ruminants 52 The Explosion of Life 14 The Giraffe’s Neck 53 Pincers of the Sea 15 Teeth in the Sea 54 Conquering the Continents 16 Teeth on Land 55 Jaws of the Sea 17 The Hominids 56 The March of the Fish 18 On Four Feet 19 THE QUATERNARY 57 The Great Forest 20 The Ice Ages 58 Born on Land 2 1 Megafauna of the Tundra 59 The First Giants 22 The Reunion of the Americas 60 Reptiles Unlike the Others 23 An Island Continent 6 1 The Great Extinction 24 The First Humans 62 Conquering the World 63 THE MESOZOIC 25 Mini-Elephants of the Islands 64 The Time of the Crocs 26 Cro-Magnon 65 The First Dinosaurs 27 The Great Warming 66 The First Mammals 28 The Pterosaurs 29 THE TIME OF THE HUMANS 67 The Jurassic Sea 30 The Agricultural Revolution 68 Sea Monsters 3 1 Cows, Pigs, Poultry 69 The Ornithischians 32 The Industrial Revolution 70 The Epic of the Stegosaurs 33 The Sixth Extinction 7 1 The Sauropods 34 Living Planet 72 The Theropods 35 Life in the Universe 73 Dinosaurs with Feathers 36 Wings and Teeth 37 Geologic Time Scale 74 Rivals of the Dinosaurs 38 Fur Balls 39 Glossary 76 Flowers for the Dinosaurs 40 The End of a World 4 1 Index 78 Night of the Cretaceous 42 by Jean-Baptiste de Panafieu • illustrated by Adrienne Barman NEW YORK Triassic: 252 to 201 million years ago THE FIRST DINOSAURS Marasuchus feeds on Some of the archosaurs insects and small animals.
    [Show full text]
  • Mammal Evolution
    Mammal Evolution Geology 331 Paleontology Triassic synapsid reptiles: Therapsids or mammal-like reptiles. Note the sprawling posture. Mammal with Upright Posture From Synapsids to Mammals, a well documented transition series Carl Buell Prothero, 2007 Synapsid Teeth, less specialized Mammal Teeth, more specialized Prothero, 2007 Yanoconodon, Lower Cretaceous of China Yanoconodon, Lower Cretaceous of China, retains ear bones attached to the inside lower jaw Morganucodon Yanoconodon = articular of = quadrate of Human Ear Bones, or lower reptile upper reptile Auditory Ossicles jaw jaw Cochlea Mammals have a bony secondary palate Primary Palate Reptiles have a soft Secondary Palate secondary palate Reduction of digit bones from Hand and Foot of Permian Synapsid 2-3-4-5-3 in synapsid Seymouria ancestors to 2-3-3-3-3 in mammals Human Hand and Foot Class Mammalia - Late Triassic to Recent Superorder Tricodonta - Late Triassic to Late Cretaceous Superorder Multituberculata - Late Jurassic to Early Oligocene Superorder Monotremata - Early Cretaceous to Recent Superorder Metatheria (Marsupials) - Late Cretaceous to Recent Superorder Eutheria (Placentals) - Late Cretaceous to Recent Evolution of Mammalian Superorders Multituberculates Metatheria Eutheria (Marsupials) (Placentals) Tricodonts Monotremes . Live Birth Extinct: . .. Mammary Glands? Mammals in the Age of Dinosaurs – a nocturnal life style Hadrocodium, a lower Jurassic mammal with a “large” brain (6 mm brain case in an 8 mm skull) Were larger brains adaptive for a greater sense of smell? Big Brains and Early Mammals July 14, 2011 The Academic Minute http://www.insidehighered.com/audio/academic_pulse/big_brains_and_early_mammals Lower Cretaceous mammal from China Jawbones of a Cretaceous marsupial from Mongolia Mammal fossil from the Cretaceous of Mongolia Reconstructed Cretaceous Mammal Early Cretaceous mammal ate small dinosaurs Repenomamus robustus fed on psittacosaurs.
    [Show full text]
  • Mesozoic: the Dark Age for Mammals!
    Ed’s Simplified History of the Mammals Note progression from Pelycosaurs (1) to Therapsids and Cynodonts (2) in Triassic. Stem mammals appeared in Late Triassic and Early Jurassic (3). Relationships among the Middle Jurassic forms (4) are controversial (see handout). Therian clade, identified by the tribosphenic molar (5), emerged at the end of the Jurassic, Early Cretaceous. A slightly more detailed version… in case you like something that looks more slick From Pough et al. 2009. Vertebrate Life, 8th ed. Pelycosaurs Dominated the late Permian, gave rise to therapsids Therapsids Rapid radiation in late Permian, around 270 MYA Still “mammal-like reptiles” The mass extinction at the end of the Permian was the greatest loss of diversity ever with >80% of all known genera and about 90% of all species going extinct, both terrestrial and marine. Cynodonts Late Permian to mid Triassic Last remaining group of therapsids, survived mass extinction at the end of the Permian. Persisted well Only 1 lineage of into Triassic and developed cynodonts survived many features associated through the late Triassic, with mammals. and this group became ancestors of mammals. Mesozoic: the Dark Age for Mammals! multituberculate Morganucodon, one of the earliest mammals (What else was happening in the Late Triassic and Jurassic Hadrocodium that may have contributed to mammals becoming small and Most were very small with nocturnal?) conservative morphology ...but new fossil finds indicate more diversity than we thought Repenomanus Still, largest known mammal during Mesozic Most were shrew to is no larger than a mouse sized, for 125 woodchuck million years! Some Mesozoic events and mammals you should know 1.
    [Show full text]
  • SUPPLEMENTARY INFORMATION: Tables, Figures and References
    Samuels, Regnault & Hutchinson, PeerJ Evolution of the patellar sesamoid bone in mammals SUPPLEMENTARY INFORMATION: Tables, Figures and References Supplementary Table S1: Mammaliaform patellar status$ Inclusive clades Genus and Stratigraphic age of Patellar Comments# (partial) species (and taxon, and location(s) state reference(s) used for 0/1/2 patellar status) (absent/ ‘patelloid’/ present) Sinoconodonta Sinoconodon Jurassic, China 0 Patellar groove absent, suggests no rigneyi (Kielan- patella Jaworowska et al., 2004) Sinoconodon is included on our phylogeny within tritylodontids. Morganucodonta Megazostrodon Late Triassic, southern 0 rudnerae (Jenkins Africa & Parrington, 1976) Morganucodonta Eozostrodon sp. Late Triassic, Wales 0 Asymmetric patellar groove, (Jenkins et al., specimens disarticulated so it is hard 1976) to assess the patella but appears absent Docodonta Castorocauda 164 Mya, mid-Jurassic, 0 Semi-aquatic adaptations lutrasimilis (Ji et China al., 2006) Docodonta Agilodocodon 164 Mya, mid-Jurassic, 0 scansorius (Meng China et al., 2015) Docodonta Docofossor 160 Mya, China 0 brachydactylus (Luo et al., 2015b) Docodonta Haldanodon 150-155 Mya, Late 0 Shallow patellar groove exspectatus Jurassic, Portugal (Martin, 2005b) Australosphenida Asfaltomylos Mid-Jurassic, South ? Postcranial material absent patagonicus America (Martin, 2005a) Australosphenida Ornithorhynchus Extant 2 Platypus, genome sequenced Monotremata anatinus (Warren, Hillier, Marshall Graves et (Herzmark, 1938; al., 2008) Rowe, 1988) Australosphenida Tachyglossus
    [Show full text]
  • Does the Jurassic Agilodocodon (Mammaliaformes, Docodonta) Have Any Exudativorous Dental Features?
    DOES THE JURASSIC AGILODOCODON (MAMMALIAFORMES, DOCODONTA) HAVE ANY EXUDATIVOROUS DENTAL FEATURES? JOHN R. WIBLE and ANNE M. BURROWS Wible, J.R. and Burrows, A.M. 2016. Does the Jurassic Agilodocodon (Mammaliaformes, Docodonta) have any exudativorous dental features? Palaeontologia Polonica 67, 289–299. Obligate exudativory, including active wounding of bark to acquire gum and/or sap, is rare among extant mammals and does not show a consistent dental signature. A recently de- scribed Middle Jurassic docodont Agilodocodon was reconstructed as an exudativore based on proposed similarities of its lower anterior dentition to some extant New World monkeys, specifically marmosets, spider monkeys, and howler monkeys. Oddly enough, of these, only marmosets are exudate-feeders. In our reinvestigation, we did not find any significant resemblance in the lower (and upper) anterior dentition between the Middle Jurassic fossil and these extant New World monkeys. The marmosets, the only obligate platyrrhine exuda- tivores, have lower and upper incisors that are distinguished from Agilodocodon and other New World monkeys by having enamel restricted to the labial surface. Differential wear between the enamel and softer dentine maintains a chisel-like tooth that marmosets use in gouging bark. Additional comparisons of the anterior dentition of Agilodocodon and other extant mammals were conducted. The lower and upper anterior teeth of Agilodocodon were found to be most similar to some elephant shrews and South American marsupials, which have a primarily insectivorous diet. Agilodocodon does not show any dental adaptations found in extant mammals for exudativory. Key words: Docodonta, Agilodocodon, marmosets, exudativory, incisors, gums. John R. Wible [[email protected]], Section of Mammals, Carnegie Museum of Natural History, 5800 Baum Boulevard, Pittsburgh, PA 15206, USA.
    [Show full text]