Susan E. Evans

Susan E. Evans
University College London | UCL · Department of Cell and Developmental Biology

PhD University of London

About

292
Publications
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Introduction
Susan E. Evans currently works at the Department of Cell and Developmental Biology, University College London. Susan does research in Anatomy, Evolutionary Biology and Paleobiology. Their current BBSRC project is 'The Role of Soft Tissues in Cranial Biomechanics - An Investigation Using Advanced Computer Modelling Techniques', but Susan is also working with collaborators in Japan, China, Egypt, the USA, Spain and the UK on a range of other anatomical and palaeontological projects relating to reptiles and amphibians
Additional affiliations
January 2011 - present
January 2008 - present
January 1998 - December 2013
University College London

Publications

Publications (292)
Article
Many reptiles reinforce the dermis with discrete mineralized organs known as osteoderms. Among lizards, osteoderms demonstrate species-specific differences in size, shape, and distribution across the body. Whether osteoderms also vary in details of tissue composition, including the organization of the fibrillar matrix, remains unclear. Here, we inv...
Article
Vertebrate skin is a remarkable organ that supports and protects the body. It consists of two layers, the epidermis and the underlying dermis. In some tetrapods, the dermis includes mineralised organs known as osteoderms (OD). Lizards, with over 7,000 species, show the greatest diversity in osteoderm morphology and distribution, yet we barely under...
Article
Monitor lizards (genus Varanus ) are today distributed across Asia, Africa and Australasia and represent one of the most recognizable and successful lizard lineages. They include charismatic living species like the Komodo dragon of Indonesia and the even larger extinct Varanus prisca ( Megalania ) of Australia. The fossil record suggests that livin...
Article
Full-text available
We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). This new taxon is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The scleral ossicles and eyelid are also visible, and the specimen exhibits pristine detai...
Article
Full-text available
The extinct freshwater choristoderan reptiles Champsosaurus and Simoedosaurus are characterised by large body size and an elongated snout. They have often been considered as eco‐analogues of crocodilians based on superficial similarities. The slender‐snouted Champsosaurus has been described as a ‘gavial‐like reptile’, which implies it feeds underwa...
Preprint
Full-text available
We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site in Myanmar. This new taxon, Retinosaurus hkamtiensis gen. et sp. nov., is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The ocular skeleton (scleral ossicles) and ey...
Article
Full-text available
Osteoderms (OD) are mineralised dermal structures consisting mainly of calcium phosphate and collagen. The sheer diversity of OD morphologies and their distribution within the skin of lizards makes these reptiles an ideal group in which to study ODs. Nonetheless, our understanding of the structure, development, and function of lizard ODs remains li...
Article
The earliest known crown‐group lepidosaurs are known from the Middle Triassic; however, their stem group is poorly sampled, with only a few representative fossils found. This is partly due to the small size and delicate bones of early stem‐lepidosaurs (= non‐lepidosaurian lepidosauromorphs), which make both preservation in the fossil record and sub...
Article
Lepidosaurs include lizards, snakes, amphisbaenians and the tuatara, comprising a highly speciose evolutionary radiation with widely varying anatomical traits. Their stem-lineage originated by the late middle Permian 259 million years ago, but its early fossil record is poorly documented, obscuring the origins of key anatomical and functional trait...
Article
Full-text available
Osteoderms are mineralised structures consisting mainly of calcium phosphate and collagen. They form directly within the skin, with or without physical contact with the skeleton. Osteoderms, in some form, may be primitive for tetrapods as a whole, and are found in representatives of most major living lineages including turtles, crocodilians, lizard...
Article
Vertebrate segmentation, the process that generates a regular arrangement of somites and thereby establishes the pattern of the adult body and of the musculoskeletal and peripheral nervous systems, was noticed many centuries ago. In the last few decades, there has been renewed interest in the process and especially in the molecular mechanisms that...
Article
Choristoderes are freshwater diapsid reptiles that are distributed through Laurasia in Jurassic–Miocene deposits. The group shows great diversity in the Early Cretaceous of Asia, with all recognized morphotypes recorded from that region. However, there is then a substantial gap in the Asian record until choristoderes are reported from the Paleocene...
Article
Full-text available
Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanic...
Article
A fragmentary diapsid left maxilla from the Bathonian Peski locality in Moscow Region, previously referred to Choristodera, is identified as Lepidosauromorpha indet. This specimen represents the first fossil record of basal lepidosauromorphs in the Middle Jurassic of European Russia. Among basal lepidosauromorphs, the maxilla from the Peski localit...
Article
Full-text available
Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted narial openings, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed...
Article
Full-text available
Cranial morphology in lepidosaurs is highly disparate and characterized by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we seek to determine how the overall cr...
Article
The chondrocranium is the cartilage component of the vertebrate braincase. Among jawed vertebrates it varies greatly in structure, mineralisation, and in the extent to which it is replaced by bone during development. In mammals, birds, and some bony fish, most of the chondrocranium is replaced by bone whereas in lizards, amphibians, and chondrichth...
Article
Albanerpetontids are tiny, enigmatic fossil amphibians with a distinctive suite of characteristics, including scales and specialized jaw and neck joints. Here we describe a new genus and species of albanerpetontid, represented by fully articulated and three-dimensional specimens preserved in amber. These specimens preserve skeletal and soft tissues...
Preprint
Full-text available
Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted osseous nares, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed s...
Article
The Kilmaluag Formation on the Isle of Skye, Scotland, provides one of the richest Mesozoic vertebrate fossil assemblages in the UK, and is among the richest globally for Middle Jurassic tetrapods. Since its discovery in 1971, this assemblage has predominantly yielded small-bodied tetrapods, including salamanders, choristoderes, lepidosaurs, turtle...
Article
Tarentola annularis is a climbing gecko with a wide distribution in Africa north of the equator. In the present paper, we describe the development of the osteocranium of this lizard, from the first appearance of the cranial elements up to the point of hatching. This is based on a combination of histology and cleared and stained specimens. This is t...
Article
Choristoderes are a small clade of freshwater aquatic reptiles known from deposits of Jurassic–Miocene age. They show their greatest diversity in the Early Cretaceous of Asia, with seven recorded genera including longirostrine and brevirostine taxa, long- and short-necked taxa, and representatives of both neochoristoderes and non-neochoristoderes....
Article
The lizard genus Yabeinosaurus is a common and relatively well-known member of Chinese Lower Cretaceous Jehol Biota, found in both the Yixian and Jiufotang formations of north-eastern China. Previous research on Yabeinosaurus has revealed information on its morphology, phylogenetic position, colouration, diet, and viviparous reproductive strategy....
Article
Full-text available
Osteoderms are hard tissues embedded in the dermis of vertebrates and have been suggested to be formed from several different mineralized regions. However, their nano architecture and micro mechanical properties had not been fully characterized. Here, using electron microscopy, µ-CT, atomic force microscopy and finite element simulation, an in-dept...
Article
Full-text available
We describe the histological appearance of the osteoderms (ODs) of Heloderma suspectum and Varanus komodoensis using multiple staining and microscopy techniques to yield information about their morphology and development. Histological analysis showed that the ODs of H. suspectum are composed of three main tissue types, a superficial layer, herein i...
Article
The Early Cretaceous lizard Yabeinosaurus is well-represented in the Jehol Biota of northeast China, with specimens yielding information on ontogenetic development, reproductive strategy, and diet, as well as skeletal morphology. However, a large, well-preserved, new specimen of Yabeinosaurus robustus from the Lamadong locality, Liaoning, provides...
Article
Full-text available
The eggs of fish, amphibians, and many invertebrates are soft, delicate structures that are only rarely preserved in the fossil record. Here we report egg masses preserved as inclusions in mid-Cretaceous amber deposits of Myanmar. Of five specimens recovered, three of the egg masses probably pertain to insects, but the other two appear different. O...
Article
The Jurassic record of lizards in eastern Asia is poor by comparison with that of the Cretaceous. In China, to date, the only confirmed records from this period are an armoured lizard from Shishugou, Xinjiang Uygur Autonomous Region, of probable Oxfordian age, and two unnamed juvenile specimens from the slightly older, Callovian-Oxfordian, Daohugou...
Article
Full-text available
Non‐avian reptiles are good models to investigate structural and developmental differences between amniotes. Investigations of craniofacial development in a complete series of embryos from oviposition up to hatching are still relatively rare. Consideration of a complete series can reveal developmental events that were previously missed, and thus co...
Article
Full-text available
For most fossil taxa, dietary inference relies primarily on indirect evidence from jaw morphology and the dentition. In rare cases, however, preserved gut contents provide direct evidence of feeding strategy and species interaction. This is important in the reconstruction of food webs and energy flow through ancient ecosystems. The Early Cretaceous...
Article
Khurendukhosaurus is an enigmatic genus of choristodere, recorded from the Lower Cretaceous of East Asia, Mongolia, and Siberian Russia. Until now, it was known only from isolated skull and postcranial elements, limiting comparison with other genera. Three major morphotypes have been recognised within Choristodera: longirostrine neochoristoderes wi...
Article
A small fauna of vertebrates is recorded from the Insect Limestone, Bembridge Marls Member, Bouldnor Formation, late Priabonian, latest Eocene, of the Isle of Wight, UK. The taxa represented are unidentified teleost fishes, lizards including a scincoid, unidentified birds and the theridomyid rodent Isoptychus . The scincoid represents the youngest...
Article
Choristodera are freshwater aquatic reptiles known from the Middle Jurassic to the Miocene. Their fossil record shows a peak in diversity in the Early Cretaceous of eastern Asia, most notably in the Jehol Biota of China but also in Japan and Mongolia. However, until now, the only Jurassic records from Asia have been rare disarticulated elements fro...
Article
Full-text available
Anurans have a long fossil record, spanning from the Early Jurassic to the Recent. However, specimens are often severely flattened, limiting their inclusion in quantitative analyses of morphological evolution. We perform a two‐dimensional morphometric analysis of anuran skull outlines, incorporating 42 Early Cretaceous to Miocene species, as well a...
Article
In vivo bone strain data provide direct evidence of strain patterns in the cranium during biting. Compared with those in mammals, in vivo bone strains in lizard skulls are poorly documented. This paper presents strain data from the skulls of Anolis equestris, Gekko gecko, Iguana iguana and Salvator merianae during transducer biting. Analysis of var...
Article
The falx cerebri and the tentorium cerebelli are two projections of the dura mater in the cranial cavity which ossify to varying degrees in some mammalian species. The idea that the ossification of these structures may be necessary to support the loads arising during feeding has been proposed and dismissed in the past, but never tested quantitative...
Conference Paper
The falx cerebri and the tentorium cerebelli are two membranous projections of the dura mater in the cranial cavity which are ossified to varying degrees in certain mammalian species. The hypothesis that ossification of these structures may be necessary to support the loads arising during feeding has been the subject of debate, but never assessed q...
Article
Full-text available
The vertebral column is segmented, comprising an alternating series of vertebrae and intervertebral discs along the head-tail axis. The vertebrae and outer portion (annulus fibrosus) of the disc are derived from the sclerotome part of the somites, whereas the inner nucleus pulposus of the disc is derived from the notochord. Here we investigate the...
Article
Full-text available
Lepidosauria is a speciose clade with a long evolutionary history, but there have been few attempts to explore its taxon richness through time. Here we estimate patterns of terrestrial lepidosaur genus diversity for the Triassic–Palaeogene (252– 23 Ma), and compare observed and sampling-corrected richness curves generated using Shareholder Quorum S...
Article
The lizard genus Bainguis was originally described from the Upper Cretaceous of Mongolia and attributed to Anguimorpha. The same genus was later reported from the Upper Cretaceous of Bayan Mandahu, Nei Mongol, China on the basis of a partial skeleton showing some similarities in osteoderm morphology. Re-examination of this specimen with the aid of...
Conference Paper
Full-text available
Normal cranial growth and development rely on appropriate tissue interactions. Soft tissues like the brain and eyes develop first, becoming enclosed by fibrous capsules (e.g. periosteum, dura) within which the skeletal units develop, and are maintained and shaped. However, with the exception of the jaw muscles, most biomechanical models do not take...
Article
Full-text available
Albanerpetontids are an enigmatic fossil amphibian group known from deposits of Middle Jurassic to Pliocene age. The oldest and youngest records are from Europe, but the group appeared in North America in the late Early Cretaceous and radiated there during the Late Cretaceous. Until now, the Asian record has been limited to fragmentary specimens fr...
Data
PAUP analysis of the full matrix run without the hypothetical ancestor. Left, Bootstrap Analysis; right, 70% Majority Rule Tree of 53 individual trees. (TIF)
Data
Bootstrap analysis using PAUP of the limited matrix. There is less resolution with respect to Wesserpeton and the Uña taxon. (TIF)
Data
Strict consensus of 53 trees run in PAUP using the full matrix, with the hypothetical ancestor as outgroup. This tree topology matches that recovered from the TNT analysis shown in Fig 34. Of the 53 individual MPTs, 15% placed Shirerpeton as the sister taxon to a monophyletic Albanerpeton; 45% placed it as the sister taxon to A. arthridion; and 40%...
Data
Characters and data matrix used in the phylogenetic analysis. (DOCX)
Conference Paper
Full-text available
Osteoderms (ODs) are bone-like-rich organs found in the skin of many reptiles. The underlying mechanisms of their formation is not well-known. However, it is likely that biomechanical forces may contribute to the formation of osteoderms. The aim of this study was to develop a finite element model of a reptile skull (with osteoderms) and to investig...
Article
Full-text available
The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the...
Preprint
The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle describ...
Article
Full-text available
Of the nearly 6,800 extant frog species, most have weak jaws that play only a minor role in prey capture. South American horned frogs (Ceratophrys) are a notable exception. Aggressive and able to consume vertebrates their own size, these "hopping heads" use a vice-like grip of their jaws to restrain and immobilize prey. Using a longitudinal experim...
Conference Paper
Full-text available
The lizard species Salvator 'Tupinambis' merianae and Varanus ornatus evolved independently in South America and Africa but share similar ecology and feeding behaviour, despite having notable differences in their skull structure. Tupinambis has a compact, relatively short and wide snout, whereas that of Varanus is more slender and narrow. In additi...
Preprint
The lizard species Salvator ‘ Tupinambis ’ merianae and Varanus ornatus evolved independently in South America and Africa but share similar ecology and feeding behaviour, despite having notable differences in their skull structure. Tupinambis has a compact, relatively short and wide snout, whereas that of Varanus is more slender and narrow. In addi...
Chapter
Today, Lepidosauria encompasses more than 9,000 species of lizards, snakes, and amphisbaenians (Squamata), as well as the New Zealand Tuatara, Sphenodon (Rhynchocephalia). In many lizards, an efficient tympanic middle ear and an effective inner-ear compensatory mechanism permit acute hearing across a range of frequencies. Sphenodon lacks a tympanic...
Article
Yabeinosaurus was the first lizard genus described from the Early Cretaceous Jehol Biota of China. The holotype of the type species, Y. tenuis, is an immature skeleton but it has been lost for decades. A second species, Y. youngi, was erected based on another immature skeleton and is distinguished by its longer, more gracile limbs. In 2001, a juven...
Article
Segmentation of the vertebrate body axis is established in the embryo by formation of somites, which give rise to the axial muscles (myotome) and vertebrae (sclerotome). To allow a muscle to attach to two successive vertebrae, the myotome and sclerotome must be repositioned by half a segment with respect to each other. Two main models have been put...
Article
The presence of a palatal dentition is generally considered to be the primitive condition in amniotes, with each major lineage showing a tendency toward reduction. This study highlights the variation in palatal tooth arrangements and reveals clear trends within the evolutionary history of tetrapods. Major changes occurred in the transition between...
Article
Full-text available
Although the Late Cretaceous lizard fauna of China and Mongolia is relatively well-known, information on Paleocene lizards from the same region is currently limited. Several species of lizards have been reported from the Paleocene Wanghudun and Doumu formations of Qianshan Basin on the basis of fragmentary specimens, namely Agama sinensis Hou, 1974...
Article
Full-text available
Polydactyly and other malformations such as supernumerary limbs are relatively common in extant salamander populations. They generally result from biotic or abiotic disruption of normal regeneration following non-lethal predator or conspecific bite injury. Here, we record, for the first time, similar malformations in a fossil salamander. Fourteen s...
Article
Choristoderes are a group of extinct freshwater reptiles that were distributed throughout Laurasia from the Middle Jurassic to the Miocene. They are inferred to have had a lifestyle similar to that of extant gavialid crocodiles, but they differed from crocodiles in retaining an extensive palatal dentition. All choristoderes had teeth on the vomers,...