Tag Archives: Morphology and Diet

Prehistoric Mammals by Don Prothero: Review of excellent new book

The Princeton Field Guide to Prehistoric Mammals ,by Donald R. Prothero, is the first extinct animal book that you, dear reader, are going to give to someone for the holidays.

screen-shot-2016-11-15-at-11-31-25-amThis book is an interesting idea. Never mind the field guide part for a moment. This isn’t really set up like a field guide, though it is produced by the excellent producers of excellent field guides at Princeton. But think about the core idea here. Take every group of mammal, typically at the level of Order (Mammal is class, there are more than two dozen living orders with about 5,000 species) and ask for each one, “what does the fossil record look like.” In some cases, a very few living species are related to a huge diversity of extinct ones. In some cases, a highly diverse living fauna is related to a much smaller number of extinct ones. And each of these different relationships between the present and the past is a different and interesting evolutionary story.

If you looked only at the living mammals, you would miss a lot because there has been so much change in the past.

The giant sloths may be extinct, but Don Prothero himself is a giant of our age among fossil experts. His primary area of expertise includes the fossil mammals (especially but not at all limited to rhinos). I believe it is true that he has personally handled more fossil mammalian material, in terms of taxonomic breath and time depth, across more institutional collections, than anyone.

Don has written several different monographs on fossil mammal groups, and recently, a general fossil book for the masses, that have, I think added to his expertise on how to produce a book like this. Illustrations by Mary Persis Williams are excellent as well.

screen-shot-2016-11-15-at-11-31-36-amA typical entry focuses on an order, and the orders are arranged in a taxonomically logical manner. A living or classic fossil representative is depicted, along with some boney material, in the form of drawings. Artist’s reconstructions, photographs, maps, and other material, with phylogenetic charting where appropriate, fills out the overview of that order.

The text is expert and informative, and very interesting. the quality of the presentation is to notch. The format of the book is large enough to let the artistry of the production emerge, but it is not a big too heavy floppy monster like some coffee table books are. This is a very comforatable book to sit and read, or browse.

It turns out that if you combine living and fossil forms for a given group, you get a much bigger picture of the facts underlying any one of a number of interesting evolutionary stories.

In addition to the order by order entries, front matter provides background to the science of paleontology, including phylogenetic method, taphonomy, etc. There is a bit of functional anatomy, and extra detailed material on teeth because, after all, the evolutionary history of man mammal groups is known primarily by analysis of (and discovery almost exclusively of) teeth.

The end matter includes a discussion of mammalian diversification, extinction, and an excellent index.

screen-shot-2016-11-15-at-11-31-46-amIf you wold like some background on how a scientist like Don Prothero writes a book like this, you can listen to this interview, in which we discuss this process in some detail.

One of the most important things about this book is that it is fully up to date, and thus, the only current mammalian evolutionary overview that is available, to my knowledge. In some areas of fossil mammal research (including in our own Order, Primates) there has been a lot of work over recent years, so this is important.

I highly recommend this excellent book.

The book as 240 pages, and 303 illustrations.

For your reference, I’ve pasted the TOC below.


  • Preface 6
  • 1 The Age of Mammals 7
  • Dating Rocks 8
  • Clocks in Rocks 10
  • What’s in a Name? 11
  • How Do We Classify Animals? 12
  • Bones vs Molecules 15
  • Bones and Teeth 15
  • 2 The Origin and Early Evolution of Mammals 20
  • Synapsids (Protomammals or Stem Mammals) 20
  • Mammals in the Age of Dinosaurs 23
  • Morganucodonts 23
  • Docodonts 25
  • Monotremes (Platypus and Echidna) and Their Relatives 27
  • Multituberculates 30
  • Triconodonts 31
  • Theria 34
  • 3 Marsupials: Pouched Mammals 37
  • Marsupial vs Placental 37
  • Marsupial Evolution 38
  • Ameridelphia 39
  • Australiadelphia 41
  • 4 Placental Mammals (Eutheria) 47
  • The Interrelationships of Placentals 50
  • 5 Xenarthra: Sloths, Anteaters, and Armadillos 51
  • Edentate vs Xenarthran 51
  • Order Cingulata (Armadillos) 53
  • Order Pilosa (Anteaters and Sloths) 55
  • 6 Afrotheria: Elephants, Hyraxes, Sea Cows, Aardvarks, and Their Relatives 58
  • Tethytheres and Afrotheres 58
  • Order Proboscidea (Elephants, Mammoths, Mastodonts, and Their Relatives) 60
  • Order Sirenia (Manatees and Dugongs, or Sea Cows) 67
  • Order Embrithopoda (Arsinoitheres) 72
  • Order Desmostylia (Desmostylians) 73
  • Order Hyracoidea (Hyraxes) 75
  • Order Tubulidentata (Aardvarks) 77
  • Order Macroscelidia (Elephant Shrews) 78
  • Order Afrosoricida 79
  • 7 Euarchontoglires: Euarchonta Primates, Tree Shrews, and Colugos 80
  • Archontans 80
  • Order Scandentia (Tree Shrews) 82
  • Order Dermoptera (Colugos, or Flying Lemurs) 82
  • Order Plesiadapiformes (Plesiadapids) 84
  • Order Primates (Euprimates) 86
  • 8 Euarchontoglires: Glires Rodents and Lagomorphs 94
  • Chisel Teeth 94
  • Order Rodentia (Rodents) 95
  • Order Lagomorpha (Rabbits, Hares, and Pikas) 101
  • 9 Laurasiatheria: Insectivores Order Eulipotyphla and Other Insectivorous Mammals 103
  • Order Eulipotyphla 103
  • Extinct Insectivorous Groups 107
  • 10 Laurasiatheria: Chiroptera Bats 112
  • Bat Origins 114
  • 11 Laurasiatheria: Pholidota Pangolins, or Scaly Anteaters 117
  • Order Pholidota (Pangolins) 118
  • Palaeanodonts 120
  • 12 Laurasiatheria: Carnivora and Creodonta Predatory Mammals 122
  • Carnivores, Carnivorans, and Creodonts 122
  • Order Creodonta 124
  • Order Carnivora 127
  • 13 Laurasiatheria: Ungulata Hoofed Mammals and Their Relatives 146
  • Condylarths 147
  • 14 Laurasiatheria: Artiodactyla Even-Toed Hoofed Mammals: Pigs, Hippos, Whales, Camels, Ruminants, and Their Extinct Relatives 151
  • Artiodactyl Origins 153
  • Suoid Artiodactyls 154
  • Whippomorpha 160
  • Tylopods 169
  • Ruminantia 175
  • 15 Laurasiatheria: Perissodactyla Odd-Toed Hoofed Mammals: Horses, Rhinos, Tapirs, and Their Extinct Relatives 186
  • Equoids 187
  • Tapiroids 191
  • Rhinocerotoids 196
  • Brontotheres, or Titanotheres 199
  • 16 Laurasiatheria: Meridiungulata South American Hoofed Mammals 203
  • Order Notoungulata (Southern Ungulates) 205
  • Order Pyrotheria (Fire Beasts) 206
  • Order Astrapotheria (Lightning Beasts) 207
  • Order Litopterna (Litopterns, or Smooth Heels) 207
  • 17 Uintatheres, Pantodonts, Taeniodonts, and Tillodonts 209
  • Order Dinocerata (Uintatheres) 209
  • Order Pantodonta (Pantodonts) 212
  • Order Taeniodonta (Taeniodonts) 214
  • Order Tillodontia (Tillodonts) 216
  • 18 Mammalian Evolution and Extinction 218
  • Why Were Prehistoric Mammals So Big? 218
  • Where Have All the Megamammals Gone? 219
  • How Did Mammals Diversify after the Dinosaurs Vanished? 222
  • What about Mass Extinctions? 228
  • The Future of Mammals 229
  • Illustration Credits 231
  • Further Reading 232
  • Index (with Pronunciation Guide for Taxonomic Names) 234
  • A Remarkable Convergence of Species: The Deadliest Sea Snake

    ResearchBlogging.orgSea snakes are true snakes that look a little like eels because of their horizontally flattened rudder-like tails, and they spend a lot of time…for most species, their entire lives…in the ocean. Only one species seems to be able to move on land at all. They seem to all be venomous, some extremely so. They are all tropical or near-tropical, and there are numerous species distributed among about 15 genera.

    One species is Enhyrina schistosa, known as the Beaked Sea Snake, or the Hook-Nosed Sea Snake. It lives in the waters near Indonesia and Australia. This is known to be the most venomous of all of the sea snakes, and a certain number of people are bitten by them. In fact, most people who die of sea snake bites were bitten by Enhyrina schistosa. How many people get bitten by them? Hard to say. In Australia, between 1942 and 1950, 56 people died from sea snake bites. What is the meaning of that number? Hard to say; it is just one of those esoteric bits of information one finds in Wikipedia. These snakes probably don’t bite very many people, but when they do, you have a problem.

    The Beaked Sea Snake feeds mainly on spiny catfish and blow fish, and as such benefits from have a large gape. Selection for the large gape has altered the morphology of this snake in a way that probably contributes to it’s beaked nose and a couple of other features that are used to distinguish it from other sea snakes and thus identify it to species. The problem is, this selection pressure seems to have caused two distinctly different groups of snakes (actually, three … see below) to converge on a single morphology. So, what we have been calling Enhyrina schistosa, the beaked sea snake, is clearly two distinct species that look enough alike to have been confused as one. This is destine to be a classic example of evolutionary convergence.

    This is all being reported in a paper due out soon in Molecular Phylogenetics & Evolution by Kanishka D.B. Ukuwela, Anslem de Silva, Mumpuni, Bryan G. Fry, Michael S.Y. Lee and Kate L. Sanders. Caroline Bird of the University of Queensland Communications Office provided some background and the great snake picture.

    From the abstract of the paper:

    We present a striking case of phenotypic convergence within the speciose and taxonomically unstable Hydrophis group of viviparous sea snakes. Enhydrina schistosa, the ‘beaked sea snake’, is abundant in coastal and inshore habitats throughout the Asian and Australian regions … Analyses of five independent mitochondrial and nuclear loci for populations spanning Australia, Indonesia and Sri Lanka indicate that this ‘species’ actually consists of two distinct lineages in Asia and Australia that are not closest relatives. As a result, Australian ‘‘E. schistosa’’ are elevated to species status and provisionally referred to Enhydrina zweifeli. … Our findings have important implications for snake bite management in light of the medical importance of beaked sea snakes and the fact that the only sea snake anti-venom available is raised against Malaysian E. schistosa.

    Have a look at this diagram:

    Fig. 4. Bayesian multi-locus coalescent species tree. Asian and Australian Enhydrina schistosa lineages form separate and distantly-related clades (each with affinities to geographically proximate taxa). Nodes with Bayesian posterior probability >0.9 are indicated. Outgroup Hemiaspis damelii is not shown. (Scale bar = substitutions per site).

    You can see the two populations, from Australia (top) and Southeast Asia (bottom), separated by numerous other species that look very different. And, if you look at just the Southeast Asian group, they cluster into two subgroups as well. Apparently this genetic divergence and grouping was not noticed by prior researcher dividing the snakes up into species and genera on the basis of morphology. Having said that, it is also true that the sea snakes are a bit dicy in their overall phylogeny, and are understudied. This, apparently, is being rectified.

    There are other potential explanations for this pattern that should be considered, involving the genetics. It is possible to come up with a genetic tree that inaccurately represents the actual phylogeny of the species at hand. This study, however, used multiple methods and multiple DNA sites, involving both mitochondrial and nucleic DNA, so the species tree you see here is probably reasonably close to accurate, and the conclusion that Enhydrina schistosa consists of two groups that are not monophyletic is strong.

    “This mixup could have been medically catastrophic, since the CSL sea snake antivenom is made using the venom from the Asian snake based on the assumption that it was the same species,” noted Bryan Fry, one of the study’s authors. “Luckily, the antivenom is not only very effective against the Australian new species but actually against all sea snakes since they all share a very stream-lined fish-specific venom.”

    Wear a wet suit!

    Ukuwela, K., de Silva, A., Mumpuni, ., Fry, B., Lee, M., & Sanders, K. (2012). Molecular evidence that the deadliest sea snake Enhydrina schistosa (Elapidae: Hydrophiinae) consists of two convergent species Molecular Phylogenetics and Evolution DOI: 10.1016/j.ympev.2012.09.031

    Get the latest news about Sungudogo, the science fiction adventure story set in the Congo, which serves as a new Origin Story for the modern Skeptics Movement, HERE.

    Two chimps walked into a bar …

    … and made a real mess of the place when one of them spotted the jar of pickles on the counter. They fought over it until one of them had almost all the pickles and the other one had a number of bruises and a tiny fragment of one pickle that the other chimp dropped by accident.

    That would be the way it would happen if two chimps walked into a bar. Or imagine two chimps, and each finds a nice juicy bit of fruit out in the forest. And instead of eating the fruit, because they are not hungry, they carry it around for a while (this would never happen, but pretend) and then accidentally run into each other. What would happen? Same thing. Event though neither chimp actually needed the fruit and each chimp had its own fruit, the dominant chimp (between the two) would end up with both pieces of fruit.

    This is why chimps could not possibly cooperate in any effort to scour the forest for various edible items, bring them all back to a central place, share and then cooperatively process the food items, and ultimately produce a meal that is eaten by all of the chimps on an as needed basis. Humans do that but chimps can’t. Explain this and you explain one of the major features of human evolution…
    Continue reading Two chimps walked into a bar …

    Why the Hobbits of Flores Were Probably Not Broken People

    There is a new paper out suggesting that the Flores hominids, known as Hobbits, were “human endemic cretins.”From the abstract of this paper:

    … We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including enlarged pituitary fossa, and that distinctive primitive features of LB1 such as the double rooted lower premolar and the primitive wrist morphology are consistent with the hypothesis. We find that the null hypothesis (that LB1 is not a cretin) is rejected by the pituitary fossa size of LB1, and by multivariate analyses of cranial measures. We show that critical environmental factors were potentially present on Flores, how remains of cretins but not of unaffected individuals could be preserved in caves, and that extant oral traditions may provide a record of cretinism.

    Continue reading Why the Hobbits of Flores Were Probably Not Broken People

    The Potato and Human Evolution

    ResearchBlogging.orgFallback foods are the foods that an organism eats when it can’t find the good stuff. It has been suggested that adaptive changes in fallback food strategies can leave a more distinct mark on the morphology of an organism, including in the fossil record, than changes in preferred food strategies. This assertion is based on work done by the Grants and others with Galapagos Island finches, by Richard Wrangham and me with hominids, and by Betsy Burr and me with rodents. Continue reading The Potato and Human Evolution

    What did the immediate ancestor of chimps and humans look like?

    Comparing living chimpanzees to living humans, in reference to the species that gave rise to these two closely related species, is one way to frame questions about the evolution of each species. Continue reading What did the immediate ancestor of chimps and humans look like?

    The Flores Hominid and the Evolution of the Shoulder

    Blogging on Peer-Reviewed Research

    Homo floresiensis more widely known as the “Hobbit,” may have had arms that were very different from those of modern humans.

    A paper in the current issue of the Journal of Human Evolution explores the anatomy of H. floresiensis. To explore this we first have to understand the concept of “Humeral torsion.” Humeral torsion is the orientation of the humeral head relative to the mediolateral axis of the distal articular surface. Don’t bother reading that sentence again, I’ll explain it.

    Continue reading The Flores Hominid and the Evolution of the Shoulder

    Life history trade-offs and human pygmies

    Blogging on Peer-Reviewed Research

    Every few years a paper comes out “explaining” short stature in one or more Pygmy groups. Most of the time the new work ads new information and new ideas but fails to be convincing. This is the case with the recent PNAS paper by Migliano et al.

    From the abstract:

    Continue reading Life history trade-offs and human pygmies

    Human Evolutionary Rate Study

    There seems to be some interesting things going on with the recently reported study of rates of evolution in humans. We are getting reports of a wide range of rather startling conclusions being touted by the researchers who wrote this paper. These conclusions typically come from press releases, and then are regurgitated by press outlets, then read and reported by bloggers, and so on. Here is, in toto, the press release from the University of Wisconsin, where John Hawks, one of the authors of the study, works. I reproduce the press release here without further comment. Continue reading Human Evolutionary Rate Study

    Study Suggests Increased Rate of Human Adaptive Evolution

    There is a new paper, just coming out in Proceedings of the National Academy of Sciences, that explores the idea that humans have undergone an increased rate of evolution over the last several tens of thousands of years. Continue reading Study Suggests Increased Rate of Human Adaptive Evolution

    Evolution of Birds: New Evidence for Foraging Behavior

    Birds evolved during the Mesozoic, during the various “Ages” of the dinosaurs, as a subset of those dinosaurs. Many researchers believe that these early birds were different from their then very close dinosaur cousins because of their flight adaptations, and some have linked this idea to flight-based or tree- based foraging.

    Today, most birds fly (counting by species) and their flight is linked to their primary dietary adaptation. Some birds actually feed on the wing, while others fly to food sites and once there do not locomote very much. Other birds forage on the ground habitually. The difference between these two kinds of birds should be evident in the morphology of their feet.

    If you examine bird feet today and can successfully characterize these feet in a way that links reliably to mode of foraging, then you should be able to look at Mesozoic bird (and dinosaur) feet and say something about how they foraged. In this way, you can test the hypothesis that early birds were flight- and tree-foragers rather than foot-foragers.

    A paper in Current Biology does this.Blogging on Peer-Reviewed Research
    The first thing the researchers had to do was to deconstruct commonly held conceptions of bird locomotion and positional behavior. In other words, they noticed that the way we characterize birds … as “ground-dweller” vs “percher” vs “climber” … requires “summarisation of potentially disparate aspects of behaviour and morphology … with emphasis on the ‘ability/inability’ to perch. However, many ‘perchers’ visit the ground and some ‘ground-dwellers’ can perch.”The authors re-categorized the birds into groups that were both finer than those normally used, and based on a better set of observations of bird behavior, focusing not on how birds cling (or fail to cling) to various arboreal surfaces, but rather, how they use their feet to forage.They then measured “claw angle” .. the angle between key physical landmarks on the third toe … which they believe varies in relation to mode of foraging.

    These data separated out by category of foraging very nicely:i-0f92c0147baff15faecba3c915caa16f-BirdForagingAndClaw.jpegTo someone who studies the relationship between morphology and behavioral adaptations, this graph is a real wet dream. One wonders if they made up the data. But they didn’t.The top part of this graph shows the claw angle (Y-axis) increasing from left to right across the foraging categories into which the authors placed the birds. Ground foraging birds are on the left, others towards the right.

    This is done for two phylogenetically distinct groups of birds and shows the same pattern for both of these large taxa.This is very nice work. In and of itself this morphological pattern is an important contribution. But there is more.The lower right part of the graph shows the claw angle measurements for Mesozoic genera. They appear to be mostly ground foragers. The horizontal line in this graph is the cutoff point that seems to work for living birds (lower than 100 degrees = ground forager, higher = varying degrees of tree foraging). One Mesozoic specimen is above this line, which does not mean much … it could be an outlier.In other words, it is reasonable to conclude that ground foraging was the predominant behavior among the Mesozoic birds.In particular the hypothesis that Mesozoic bird evolution involved flight-and tree based foraging is not supported by this analysis. This forces evolutionary biologists to change their thinking about early bird evolution. Science marches on


    GLENN, CHRISTOPHER L. BENNETT, MICHAEL B.(2007): Foraging modes of Mesozoic birds and non-avian theropods. Current Biology, 17, R911-R912.