In the United States wealthy tycoons funded fossil-hunting expeditions and new natural history museums to display their discoveries. Dinosaurs from the Western states dramatically transformed the way the ascent of life could be represented because they were quite unlike any living reptiles and confirmed that the ‘tree of life’ had many more branches, some of which had disappeared completely. There was increasing evidence of relatively abrupt transitions in the earth’s history, forcing geologists and evolutionists to reconsider their impression that change had been more or less continuous. As the tree of life became more complex, the assumption that the human species was the inevitable outcome of progressive evolution became less plausible. Although non-Darwinian theories were retained by some authorities, the new vision of evolution came to seem more compatible with Darwin’s vision of an open-ended and less predictable process.

This chapter compares work done by Hugh Hamshaw Thomas (1885–1962) in two domains. First, in palaeobotany; second, in military intelligence in the First and Second World Wars. In each, Thomas investigated landscape processes using fragmentary visual evidence: plant evolution from fossils, enemy behaviour from aerial photographs. I propose we understand the connection between those domains by drawing together two, largely separate, scholarly discussions: (i) on the construction and evidential use of photographic archives; (ii) on evidence and causal explanations in the historical sciences. Through analysis of Thomas’s palaeobotanical and military work I situate narrative as the central and unifying principle of a practice in which neither evidence collection nor explanatory accounts were prior. This unifying ‘narrative practice’ was reticulate, multi-scalar and dynamic, as revealed by contemporary figures of speech that sought to describe it (working ‘like Sherlock Holmes’, ‘reading the book of nature’, thinking ‘like a river’).

Eurasian Miocene snake taxa, localities, stratigraphy, palaeogeography, and palaeoenvironment are reviewed. Palaeogeographic evolution of Paratethys facilitated communication between European and Asiatic faunas since the early Oligocene, with at least two main routes from Asia or Africa into Europe. The early Burdigalian saw spreading of non-erycid Booidea and the first ‘Oriental vipers’ in Europe, which dispersed substantially within Eurasia during late Ottnangian warming. This warm climate, culminating as the Miocene Climatic Optimum, was associated with the middle Burdigalian first appearance of highly thermophilic Naja and Python in Europe. Python disappeared in Europe at the end of the Langhian due to rapid cooling, but Naja and ‘Oriental vipers’ persisted until the late Pliocene and early Pleistocene, respectively. Communication among mid-latitude Asian and European assemblages occurred across the early–middle Miocene, but this Eurasian fauna was heterogeneous, at least since the middle Miocene. Miocene S and SE Asian snakes resemble those of today. Increasing end-Miocene aridity and Eurasia–Africa connection facilitated invasion into Eurasia of African and SW Asian taxa.

The origin and early evolution of snakes has long been studied, but little research has focused on soft-tissue organs such as the brain. I report data from dissections and 3D reconstructions of the endocasts of diverse species, including the Cretaceous stem snake Dinilysia patagonica in order to provide a comparative evolutionary framework for the snake brain. Snakes are a special case among reptiles because the braincase almost entirely encloses the whole brain, so endocasts provide realistic representations of brain size and shape. Diversity of brain gross anatomy among snakes is remarkable, encompassing two major cerebrotypes occurring in surface-dwelling and burrowing species. The repeated acquisition of the burrowing cerebrotype in different and phylogenetically distant snake clades suggests that brain gross anatomy is surprisingly evolutionary labile in snakes. Brain gross anatomy and other features such as body size and the absence of any unequivocal osteological feature related to burrowing is interpreted as evidence that D. patagonica was surface-dwelling, and that at least some of the early history of snakes occurred above ground.

Sea-serpent sightings were popular subjects of nineteenth century fictional tales. One of the most famous sightings, the 1817 appearance in the harbor of Gloucester (Massachusetts), generated a report published by the Linnean Society of New England. In 1869, ED Cope introduced a new reptilian order, Pythonomorpha, comprising large Upper Cretaceous marine lizards (mosasaurs) that he thought rather well captured in historical depictions of sea-serpents. The name Pythonomorpha emphasized the many striking features that Cope found mosasaurs to share with snakes. Cope’s Pythonomorpha was resurrected in the late 1990s, as a clade including mosasaurs plus snakes. This was supported by the placement of mid-Cretaceous marine snakes with well-developed hindlimbs as evolutionarily intermediate between mosasauroids and snakes. Critics pointed to features indicating that those fossil snakes are instead evolutionarily advanced, which would imply that hindlimbs of these fossil snakes re-developed from rudiments such as occur in pythons. Recent molecular developmental studies confirmed that the embryonic limb bud of the python hindlimb conserves the genetic program to generate a complete limb.

We give a review of all published Palaeogene snake taxa from all localities worldwide. Several conceptual and material advances in the past two decades—a focus on apomo+P31rphies, greater attention to variation, quantification of morphology, and new fossil discoveries—have vivified the fossil record. Particularly noteworthy have been new fossils from Gondwanan continents and complete, articulated skeletons. Species known only from vertebrae are unlikely to be placed precisely phylogenetically, but a high number of vertebrae is a strong indication that cranial remains are present, which in turn allow more precise phylogenetic placement. Extrapolations of snake palaeodiversity are of the same order of magnitude as rough calculations of cumulative lineage diversity in the Palaeogene, raising the prospect that palaeontological morphospecies may more closely approximate biological species than is commonly conceived. As their interrelationships become better known, Palaeogene fossils will increasingly help elucidate the early evolution of snakes.

This brief chapter introduces the book. The rationale, scope, and coverage are summarized, including mention of topics that are not covered. Aspects of debate, disagreement, and consensus in the field are summarized before the chapter is concluded with a look to future potential progress.

The Cretaceous fossil record of snakes demonstrates the origin and evolution of the snake body and the early ecological and biogeographic history of the clade during the first 80 million years of their history. Consisting primarily of isolated vertebrae as well as a small number of mostly complete specimens, the record shows the elongate body of snakes evolved no earlier than approximately 100 million years ago. Stem snakes are present in terrestrial and marine palaeoenvironments throughout the Late Cretaceous of northern and southern continents. Conversely, the oldest records of living clades are restricted to the Campanian of South America, Africa, and possibly North America, which requires episodes of dispersal, or unrealistically long ghost lineages extending back to tectonically-mediated vicariance, to explain geographic distributions. Most Maastrichtian-aged stem and primary living clades extend into the Paleogene, indicating that the K-Pg extinction event had little visible effect on the evolution of snakes, whereas major diversifications of crown clades are constrained from middle Paleogene to Neogene.

Snakes have distinct body plans that can be traced to the origin of the clade. It remains unresolved whether ancestral snakes were adapted to terrestrial environments as burrowers, or to marine environments as swimmers. Recently, new approaches have been used to infer fossorial and aquatic specialists in the early evolution of snakes, using virtual CT models of the ear of fossils. This chapter reviews variation in the osseous part of the ear of major snake lineages. Vestibules are relatively large in fossorial species and small in aquatic snakes. Using quantitative analyses of bony labyrinth geometry, it has been suggested that putative stem snakes, such as Dinilysia patagonica, were fossorial. Improvements to testing correlations between bony labyrinth morphology and ecology can be made in the refinement of quantitative approaches to capturing and analysing shape variations, as well as better classifications of ecology. Using inner and middle ear morphology to improve the accuracy and precision of inferences of the ecology of the ancestral snake will depend also upon robust, well-resolved phylogenies for extinct and extant taxa, and denser taxonomic and ecomorphological sampling.

This chapter assesses morphological characters proposed to support the Pythonomorph Hypothesis— a purported close relationship between snakes and mosasaurians. With an emphasis on early diverging (non-mosasaurid) mosasaurians and mosaurids, new morphological data (including from high-resolution CT) for well-preserved dolichosaurid and mosasaurid fossils are presented. Details of the skull and mandibles are interpreted as supporting the monophyly of Mosasauria as the proximal outgroup of Varanoidea, to the exclusion of snakes. However, mosasaurians do deviate from the typical varanoid condition in aspects of their infraorbital foramen, ventral part of the lacrimal and its relationship with the prefrontal, anterior ramus of the ectopterygoid and its contact with the maxilla and jugal, lack of plicidentine, and (at least in early diverging mosasaurians) anguinoidean tooth replacement. We consider most characters previously reported as supporting the Pythonomorph Hypothesis to be problematic, because of incomplete fossil preparation, artefacts of taphonomy, limited comparisons, misinterpretations of anatomy, incomplete taxon sampling, or inadequate character formulation and/or scoring.

Mosasaurian phylogenetics has been one of the most controversial topics in squamate systematics, with various studies and authors arguing in favor of a varanoid affinity (the Varanoid Hypothesis), a snake affinity (the Pythonomorph and Ophidiomorph Hypotheses) or only distant affinities to these lineages (the Stem-scleroglossan Hypothesis). We review the classification history of mosasaurians over the past two centuries, focusing on non-mosasaurid mosasaurians (dolichosaurs and aigialosaurs). A reappraisal is provided based on a new phylogenetic analysis. Our results clearly support the Varanoid Hypothesis. The Pythonomorph and Ophidiomorph Hypotheses are reviewed, and characters traditionally inferred to support these hypotheses are discussed and reinterpreted. Taxonomic sampling and fossil completeness likely play a major role—our (hopefully improved) phylogenetic hypothesis being based on denser taxon sampling and more complete character scoring resulting from additional studies, including the application of modern imaging techniques. Based on current data, our interpretation is that a particularly close phylogenetic relationship between mosasaurians and snakes can be rejected.

Pachyophiidae fossils are among the most complete known for snakes, and include the earliest snakes with fully developed hindlimbs. Pachyophiids have been historically seen as suitable morphological intermediates between lizards and extant snakes, supporting the hypothesis that snakes originated in a marine setting from a macrophagous common ancestor with mosasaurian lizards. Pachyophiids have been subject to conflicting interpretations of their anatomy, fuelling renewed debate on snake origins and early diversification. We revisit pachyophiid cranial anatomy, providing additional evidence from new preparations, high resolution CT scans, and Synchrotron images. We address challenges posed by fossil (in)completeness to the study and interpretation of these specimens, and reassess phylogenetic affinities. We critically reassess morphological evidence supporting the Marine Hypothesis, concluding that (i) snakes are not especially closely related to mosasaurians, and (ii) pachyophiids are relatively deeply nested within the snake crown, so that they are of greater importance for understanding early crown-snake evolutionary history than they are for understanding snake origins.

Squamata, the group that comprises lizards, snakes, and amphisbaenians, is the largest and most diverse major group of living reptiles. Although most recent estimates place their divergence from Rhynchocephalia in the early Triassic, the first unequivocal records of squamates currently date from the Middle Jurassic, and the first crown squamates, representing Scincoidea, Anguimorpha, and possibly Gekkota, are known from the Late Jurassic. The record then improves substantially in the Early Cretaceous, with squamate fossils recorded from most major continents and showing evidence of expansion into a diversity of specialist niches. Despite recent claims to the contrary, the earliest unequivocal snake fossils also date from this period, with fragmentary remains from the Aptian-Cenomanian of North Africa and North America, followed by a more substantial global record from the Cenomanian onwards. The re-interpretation of the Middle Jurassic to Early Cretaceous parviraptorids as snakes was based on a misinterpretation of the original material, as shown by new associated specimens from the Middle Jurassic of Scotland.

In “Extinction,” Timothy Sweet explores how species extinction and the ultimate specter of human extinction shape modern literature and theory. The chapter begins with an overview of the Sixth Extinction crisis, which was first recognized by scientists in the 1980s and has since become a matter of public concern in journalism and memoir. The chapter then focuses on the history of the concept of extinction from its establishment as geohistorical fact in the late eighteenth century to its role in the development of evolutionary theory. An important archive for the chapter is the repository of megafaunal remains from Big Bone Lick, Kentucky. Alternative explanations for these extinctions and other fossil remains circulated in American Indian traditions, and later versions adapted Darwinian theory to traditional ends. The chapter ends with examination of literary and artistic works such as Barbara Kingsolver’s Flight Behavior that grapple with the problems of representing the extinction of animals and humans.

In this chapter I show that although hypothetical ancestors largely lost their epistemic power as deliberately constructed phylogenetic tools after the spread of modern phylogenetics, narrative phylogenetic reasoning persists. A conspicuous and widespread example of employing narrative shortcuts in evolutionary storytelling today is the attempt to use the phylogenetic position of taxa to predict the presence of ancestral character states. In close analogy to the historical use of the label ‘lower’ to designate taxa that are presumed primitive, modern authors use a range of evocative adjectives to promote the presumed presence of ancestral character states in their favoured taxa. ‘Basal’ is the most frequently used label, and many authors think that its link to the phylogenetic position of taxa gives it predictive power over whether these are likely to have retained ancestral states. I explain that phylogenetic and evolutionary theory provide no convincing rationale for this argument, and argue instead that basal taxa can be especially misleading about the nature of their character states. Proper lineage thinking can help one avoid this conceptual mistake.

In this chapter I take a close look at the early lineage thinking of paleontologists and their attempts to infer evolution from stratigraphic sequences of fossils. Linear thinking with fossils emerged as a core component of the traditional paleontological method in the second half of the nineteenth century. It was taken to extremes by orthogeneticists, and I use the late-nineteenth-century debate between Franz Hilgendorf and Alpheus Hyatt about the famous freshwater Miocene Steinheim snails as a case study for looking at competing forms of lineage thinking. But it was in fact the straight-thinking orthogeneticist Othenio Abel who helped resolve the conundrum of how branching evidence can shed light on the evolution of linear lineages.

Pressing geological questions emerged during the early nineteenth-century exploration of the Himalaya, especially around fossils, volcanoes and glaciers. This chapter considers the place of East India Company employees and travellers on the fringes – both geographically and socially – of rapidly evolving debates. The chapter argues that overlapping political frontiers, topographical barriers and ‘cultural borderlands’, all shaped geological practices. The chapter begins with a group of fossils sold by Bhotiyas under the name of bijli ki har or ‘lightning bones’, which reveal tensions between specimens that were both scientifically and cosmologically significant. The chapter also considers the important roles of brokers in locating and transporting fossils, especially by discussing the career of Pati Ram. This is followed by a broader assessment of how these material remains fit into discussions about the upheavement of the Himalaya and notions of a universal deluge. Expanding from fossils, the chapter concludes by examining glaciers (especially debates over their existence in the Himalaya, and evidence of their retreat over both long timescales and within the memories of Himalayan peoples).