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Journal articles on the topic 'Amniote'

Author: Grafiati

Published: 4 June 2021

Last updated: 30 January 2023

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1

Sanger, Thomas J., Marissa L. Gredler, and Martin J. Cohn. "Resurrecting embryos of the tuatara, Sphenodon punctatus , to resolve vertebrate phallus evolution." Biology Letters 11, no. 10 (2015): 20150694. http://dx.doi.org/10.1098/rsbl.2015.0694.

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The breadth of anatomical and functional diversity among amniote external genitalia has led to uncertainty about the evolutionary origins of the phallus. In several lineages, including the tuatara, Sphenodon punctatus , adults lack an intromittent phallus, raising the possibility that the amniote ancestor lacked external genitalia and reproduced using cloacal apposition. Accordingly, a phallus may have evolved multiple times in amniotes. However, similarities in development across amniote external genitalia suggest that the phallus may have a single evolutionary origin. To resolve the evolutionary history of amniote genitalia, we performed three-dimensional reconstruction of Victorian era tuatara embryos to look for embryological evidence of external genital initiation. Despite the absence of an intromittent phallus in adult tuataras, our observations show that tuatara embryos develop genital anlagen. This illustrates that there is a conserved developmental stage of external genital development among all amniotes and suggests a single evolutionary origin of amniote external genitalia.

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2

Piñeiro, Graciela, Pablo Núñez Demarco, and Melitta D. Meneghel. "The ontogenetic transformation of the mesosaurid tarsus: a contribution to the origin of the primitive amniotic astragalus." PeerJ 4 (May 17, 2016): e2036. http://dx.doi.org/10.7717/peerj.2036.

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The hypotheses about the origin of the primitive amniotic tarsus are very speculative. Early studies argued that the origin of the astragalus, one of the largest proximal bones in the tarsus of basal amniotes, was produced by either the fusion of two, three, or even four of the original tarsal bones, the intermedium, the tibiale and the proximal centralia (c4 and c3), or that the intermedium alone transforms into the primitive astragalus. More recent studies have shown that the structure of the tarsus inCaptorhinussupports the former hypothesis about a fusion of the intermedium, the tibiale, the proximal centrale (c4) and eventually c3, producing a purportedly multipartite structure of the amniotic astragalus, but the issue remained contentious. Very well preserved tarsi of the Early Permian aquatic amnioteMesosaurus tenuidensGervais, 1864–1865, which represent the most complete ontogenetic succession known for a basal amniote (the other exceptional one is provided by the Late Permian diapsidHovasaurus bouleiPiveteau, 1926), suggest that there is more than one ossification center for the astragalus and that these fuse during late embryonic stages or maybe early after birth. A non-hatchedMesosaurusin an advanced stage of development shows that the tarsus is represented by a single bone, most probably the astragalus, which seems to be formed by the suturing of three bones, here interpreted as being the intermedium, the tibiale, probably already integrated to the c4 in an earlier stage of the development, and the c3. An amniote-like tarsal structure is observed in very basal Carboniferous and Permian tetrapods such asProterogyrinus, Gephyrostegus, the diadectidsDiadectesandOrobates, some microsaurs likeTuditanusandPantylusand possiblyWestlothiana, taxa that were all considered as true amniotes in their original descriptions. Therefore, the structure of the amniotic tarsus, including the configuration of the proximal series formed by the astragalus and the calcaneum, typically a pair of enlarged bones, could have been established well before the first recognized amniote walked on Earth. Accordingly, the tarsus of these taxa does not constitute specialized convergences that appeared in unrelated groups, they might be instead, part of a transformation series that involves taxa closely related to the early amniotes as some hypotheses have suggested.

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3

Smithson, T. R., R. L. Carroll, A. L. Panchen, and S. M. Andrews. "Westlothiana lizziae from the Viséan of East Kirkton, West Lothian, Scotland, and the amniote stem." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 84, no. 3-4 (1993): 383–412. http://dx.doi.org/10.1017/s0263593300006192.

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ABSTRACTWestlothiana lizziae is known from the Brigantian of East Kirkton, Scotland. The skull resembles that of later amniotes in the large size of the parietal, the apparent loss of the intertemporal, and the absence of a squamosal notch, palatal fangs and labyrinthine infolding of the marginal teeth, but is primitive in the absence of a transverse flange of the pterygoid. The individual trunk vertebrae resemble those of amniotes; large intercentra are retained, but the neural arch is fused to the centrum. A surprising feature is the presence of 36 presacral vertebrae, as is the relative size of the very small but highly ossified limbs. The humerus is much shorter than the femur, but similar in configuration to that of early amniotes. There are three proximal tarsals as in primitive tetrapods, but an amniote phalangeal count. The presence of massive dorsal as well as ventral scales is a more primitive feature than that of most anthracosaurs.Westlothiana is ‘reptiliomorph’, and is judged to be a stem-group amniote on features of the skull roof, the absence of an otic notch, the gastrocentrous vertebrae and the pedal phalangeal formula. It has not, however, reached the amniote condition in the structure of the tarsus, and the palate is more primitive than that of both early amniotes and the ‘diadectomorphs’.

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4

Martinez-Garcia, Fernando. "The origin of the amniote sensory and motor cortices." Behavioral and Brain Sciences 26, no. 5 (2003): 561–63. http://dx.doi.org/10.1017/s0140525x0331012x.

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A rigorous cladistic analysis of the dorsal pallium of amniotes indicates that the stem amniote lacked sensorimotor areas. Reptiles apparently acquired a visual cortex by parcellation from the multimodal, hippocampal-like mediodorsal pallium of stem amniotes. The high number of sensory areas of the mammalian isocortex might derive from the specific properties it shows, such as growth-promoting influence on thalamic axons.

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5

Singchat, Worapong, Syed Farhan Ahmad, Nararat Laopichienpong, et al. "Snake W Sex Chromosome: The Shadow of Ancestral Amniote Super-Sex Chromosome." Cells 9, no. 11 (2020): 2386. http://dx.doi.org/10.3390/cells9112386.

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Heteromorphic sex chromosomes, particularly the ZZ/ZW sex chromosome system of birds and some reptiles, undergo evolutionary dynamics distinct from those of autosomes. The W sex chromosome is a unique karyological member of this heteromorphic pair, which has been extensively studied in snakes to explore the origin, evolution, and genetic diversity of amniote sex chromosomes. The snake W sex chromosome offers a fascinating model system to elucidate ancestral trajectories that have resulted in genetic divergence of amniote sex chromosomes. Although the principal mechanism driving evolution of the amniote sex chromosome remains obscure, an emerging hypothesis, supported by studies of W sex chromosomes of squamate reptiles and snakes, suggests that sex chromosomes share varied genomic blocks across several amniote lineages. This implies the possible split of an ancestral super-sex chromosome via chromosomal rearrangements. We review the major findings pertaining to sex chromosomal profiles in amniotes and discuss the evolution of an ancestral super-sex chromosome by collating recent evidence sourced mainly from the snake W sex chromosome analysis. We highlight the role of repeat-mediated sex chromosome conformation and present a genomic landscape of snake Z and W chromosomes, which reveals the relative abundance of major repeats, and identifies the expansion of certain transposable elements. The latest revolution in chromosomics, i.e., complete telomere-to-telomere assembly, offers mechanistic insights into the evolutionary origin of sex chromosomes.

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6

Laurin, Michel, and Robert R. Reisz. "A new study of Solenodonsaurus janenschi, and a reconsideration of amniote origins and stegocephalian evolution." Canadian Journal of Earth Sciences 36, no. 8 (1999): 1239–55. http://dx.doi.org/10.1139/e99-036.

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A restudy of the holotype and other known specimens of Solenodonsaurus, a Late Carboniferous relative of amniotes, suggests that this taxon did not have a tympanum. Its teeth lack labyrinthine infolding, and the frontal did not reach the orbit. A new phylogenetic analysis of stegocephalians suggests that Solenodonsaurus is an anthracosaur, and that it is the sister group of Cotylosauria. It also shows that the problematic taxon Westlothiana may not be an anthracosaur (not a stem-amniote). A recent suggestion that diadectomorph cotylosaurs laid amniotic eggs is shown to be based on tenuous evidence, although this remains a possibility. The evolution of the otic region is studied using parsimony to determine whether the emargination present in Solenodonsaurus and in some diadectomorphs is a primitive or a secondary character, but this procedure yields equivocal results.

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7

Modesto, Sean P., Diane M. Scott, Mark J. MacDougall, Hans-Dieter Sues, David C. Evans, and Robert R. Reisz. "The oldest parareptile and the early diversification of reptiles." Proceedings of the Royal Society B: Biological Sciences 282, no. 1801 (2015): 20141912. http://dx.doi.org/10.1098/rspb.2014.1912.

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Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Carboniferous Period, and that the diversity of end-Carboniferous reptiles is 80% greater than suggested by previous work. Latest Carboniferous reptiles were still half as diverse as synapsid amniotes, a disparity that may be attributable to preservational biases, to collecting biases, to the origin of herbivory in tetrapods or any combination of these factors.

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8

Birchard, G. F., and C. L. Reiber. "A COMPARISON OF AVIAN AND REPTILIAN CHORIOALLANTOIC VASCULAR DENSITY." Journal of Experimental Biology 178, no. 1 (1993): 245–49. http://dx.doi.org/10.1242/jeb.178.1.245.

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Oviparous amniotes exchange respiratory gases across a specialized vascular membrane, the chorioallantois. Although many investigations into the physiology of amniote eggs, particularly those of the chicken, have been carried out, there is no comparative information about the chorioallantoic membrane. Given the differences in size and phylogeny, it might be expected that significant morphological differences exist in this gas-exchange organ.

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9

Christ, Bodo, Ruijin Huang, and Martin Scaal. "Amniote somite derivatives." Developmental Dynamics 236, no. 9 (2007): 2382–96. http://dx.doi.org/10.1002/dvdy.21189.

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10

Müller, Johannes, Torsten M. Scheyer, Jason J. Head, et al. "Homeotic effects, somitogenesis and the evolution of vertebral numbers in recent and fossil amniotes." Proceedings of the National Academy of Sciences 107, no. 5 (2010): 2118–23. http://dx.doi.org/10.1073/pnas.0912622107.

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The development of distinct regions in the amniote vertebral column results from somite formation and Hox gene expression, with the adult morphology displaying remarkable variation among lineages. Mammalian regionalization is reportedly very conservative or even constrained, but there has been no study investigating vertebral count variation across Amniota as a whole, undermining attempts to understand the phylogenetic, ecological, and developmental factors affecting vertebral column variation. Here, we show that the mammalian (synapsid) and reptilian lineages show early in their evolutionary histories clear divergences in axial developmental plasticity, in terms of both regionalization and meristic change, with basal synapsids sharing the conserved axial configuration of crown mammals, and basal reptiles demonstrating the plasticity of extant taxa. We conducted a comprehensive survey of presacral vertebral counts across 436 recent and extinct amniote taxa. Vertebral counts were mapped onto a generalized amniote phylogeny as well as individual ingroup trees, and ancestral states were reconstructed by using squared-change parsimony. We also calculated the relationship between presacral and cervical numbers to infer the relative influence of homeotic effects and meristic changes and found no correlation between somitogenesis and Hox-mediated regionalization. Although conservatism in presacral numbers characterized early synapsid lineages, in some cases reptiles and synapsids exhibit the same developmental innovations in response to similar selective pressures. Conversely, increases in body mass are not coupled with meristic or homeotic changes, but mostly occur in concert with postembryonic somatic growth. Our study highlights the importance of fossils in large-scale investigations of evolutionary developmental processes.

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11

Briscoe, Steven D., and Clifton W. Ragsdale. "Homology, neocortex, and the evolution of developmental mechanisms." Science 362, no. 6411 (2018): 190–93. http://dx.doi.org/10.1126/science.aau3711.

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The six-layered neocortex of the mammalian pallium has no clear homolog in birds or non-avian reptiles. Recent research indicates that although these extant amniotes possess a variety of divergent and nonhomologous pallial structures, they share a conserved set of neuronal cell types and circuitries. These findings suggest a principle of brain evolution: that natural selection preferentially preserves the integrity of information-processing pathways, whereas other levels of biological organization, such as the three-dimensional architectures of neuronal assemblies, are less constrained. We review the similarities of pallial neuronal cell types in amniotes, delineate candidate gene regulatory networks for their cellular identities, and propose a model of developmental evolution for the divergence of amniote pallial structures.

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12

Company, Verónica, Juan Antonio Moreno-Bravo, Ariadna Perez-Balaguer, and Eduardo Puelles. "The Amniote Oculomotor Complex." Anatomical Record 302, no. 3 (2018): 446–51. http://dx.doi.org/10.1002/ar.23827.

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13

Berman, David S. "Origin and early evolution of the amniote occiput." Journal of Paleontology 74, no. 5 (2000): 938–56. http://dx.doi.org/10.1017/s0022336000033114.

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Reinterpretation of cranial materials of the diadectomorphs Limnoscelis and Diadectes has prompted a reconsideration of the origin and early evolution of the amniote occiput. The basic approach is a phylogenetic study of major groups of Paleozoic tetrapods based on the occiput and closely associated elements of the skull roof. A lack of adequate anatomical data has forced the elimination of only a few relevant higher-level taxa from consideration, and, using Acanthostega as the reference outgroup, a cladistic analysis of the interrelationships of the Lepospondyli, Temnospondyli, Seymouriamorpha, Baphetidae (= Loxommatidae), Anthracosauria, Diadectomorpha, Synapsida, and Reptilia has produced the following results: 1) the ingroup taxa exhibit a basal dichotomy in which one division consists of the unresolved relationships of Lepospondyli, Temnospondyli, and Seymouriamorpha; 2) the pattern of relationships of the second division of the ingroup taxa is a series of nested clades, terminating with the Diadectomorpha and Synapsida as sister taxa sharing a more recent common ancestor than either does with Reptilia. This relationship requires assignment of Diadectomorpha to Amniota; and 3) the Anthracosauria and Baphetidae are progressively more distant clades or sister taxa. On the basis of the cladistic analysis, the attainment of the amniote occiput is described as passing through four morphological grades of organization. Each grade of the series is characterized by a set of derived character states that defines the progressively more-derived nodes and from which branch a clade containing the unresolved trichotomy of Lepospondyli, Temnospondyli, and Seymouriamorpha; the Baphetidae clade; the Anthracosauria clade; and the Diadectomorpha + Synapsida and Reptilia clades, respectively.

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14

Roman-Trufero, Monica, Constance M. Ito, Conrado Pedebos, et al. "Evolution of an Amniote-Specific Mechanism for Modulating Ubiquitin Signaling via Phosphoregulation of the E2 Enzyme UBE2D3." Molecular Biology and Evolution 37, no. 7 (2020): 1986–2001. http://dx.doi.org/10.1093/molbev/msaa060.

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Abstract Genetic variation in the enzymes that catalyze posttranslational modification of proteins is a potentially important source of phenotypic variation during evolution. Ubiquitination is one such modification that affects turnover of virtually all of the proteins in the cell in addition to roles in signaling and epigenetic regulation. UBE2D3 is a promiscuous E2 enzyme, which acts as an ubiquitin donor for E3 ligases that catalyze ubiquitination of developmentally important proteins. We have used protein sequence comparison of UBE2D3 orthologs to identify a position in the C-terminal α-helical region of UBE2D3 that is occupied by a conserved serine in amniotes and by alanine in anamniote vertebrate and invertebrate lineages. Acquisition of the serine (S138) in the common ancestor to modern amniotes created a phosphorylation site for Aurora B. Phosphorylation of S138 disrupts the structure of UBE2D3 and reduces the level of the protein in mouse embryonic stem cells (ESCs). Substitution of S138 with the anamniote alanine (S138A) increases the level of UBE2D3 in ESCs as well as being a gain of function early embryonic lethal mutation in mice. When mutant S138A ESCs were differentiated into extraembryonic primitive endoderm, levels of the PDGFRα and FGFR1 receptor tyrosine kinases were reduced and primitive endoderm differentiation was compromised. Proximity ligation analysis showed increased interaction between UBE2D3 and the E3 ligase CBL and between CBL and the receptor tyrosine kinases. Our results identify a sequence change that altered the ubiquitination landscape at the base of the amniote lineage with potential effects on amniote biology and evolution.

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15

Heaton, M. J., and R. R. Reisz. "Phylogenetic relationships of captorhinomorph reptiles." Canadian Journal of Earth Sciences 23, no. 3 (1986): 402–18. http://dx.doi.org/10.1139/e86-042.

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The Captorhinomorpha consists of two families, the Captorhinidae and the Protorothyrididae. The distribution of morphological character states of the skeleton permits reevaluation of currently accepted theories of the relationships of captorhinomorph reptiles. Identification of characters states that are primitive for reptiles (amniotes) has been made through outgroup comparison. The Captorhinidae, Protorothyrididae, and Diapsida form a natural group that share such derived characters as reduced supratemporal, reduced tabular, narrow supraoccipital with anteriorly directed crista alaris, loss of supratemporal–postorbital contact, loss of opisthotic–tabular contact, and loss of the medial centralia pedis. These shared derived character states indicate that captorhinomorphs are not the sister taxon of all other reptiles but are advanced relative to pelycosaurs, pareiasaurs, and procolophonids. Protorothyridids share with diapsids such derived characters as short postorbital region of the skull, keeled anterior presacral pleurocentra, slender limbs, and long, slender feet. This distribution of character states indicates that protorothyridids are more closely related to diapsids than either of these taxa is to captorhinids.The morphological pattern of small, lightly built, agile insectivores, represented by protorothyridids and early diapsids, is no longer considered to be the primitive amniote condition. Available evidence indicates that the most primitive amniote adaptation was, instead, that of a small, relatively slow carnivore that probably fed on primitive, terrestrial annelids and arthropods.

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16

Delgado, S., M. Ishiyama, and J. Y. Sire. "Validation of Amelogenesis Imperfecta Inferred from Amelogenin Evolution." Journal of Dental Research 86, no. 4 (2007): 326–30. http://dx.doi.org/10.1177/154405910708600405.

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We used the evolutionary analysis of amelogenin (AMEL) in 80 amniotes (52 mammalian and 28 reptilian sequences) to aid in the genetic diagnosis of X-linked amelogenesis imperfecta (AIH1). Out of 191 residues, 77 were found to be unchanged in mammals, and only 34 in amniotes. The latter are considered crucial residues for enamel formation, while the 43 residues conserved only in mammals could indicate that they play new, important roles for enamel formation in this lineage. The 5 substitutions leading to AIH1 were validated when the mammalian dataset was used, and 4 of them with the amniote dataset. These 2 sequence datasets will facilitate the validation of any human AMEL mutation suspected of involvement in AIH1. This evolutionary analysis also revealed numerous residues that appeared to be important for correct AMEL function, but their role remains to be elucidated.

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17

Purnell, Beverly A. "Shaping the early amniote embryo." Science 367, no. 6476 (2020): 401.8–402. http://dx.doi.org/10.1126/science.367.6476.401-h.

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18

Wilkinson, M., and R. A. Nussbaum. "Caecilian viviparity and amniote origins." Journal of Natural History 32, no. 9 (1998): 1403–9. http://dx.doi.org/10.1080/00222939800770701.

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19

Montiel, Eugenia E., Daleen Badenhorst, Ling S. Lee, Robert Literman, Vladimir Trifonov, and Nicole Valenzuela. "Cytogenetic Insights into the Evolution of Chromosomes and Sex Determination Reveal Striking Homology of Turtle Sex Chromosomes to Amphibian Autosomes." Cytogenetic and Genome Research 148, no. 4 (2016): 292–304. http://dx.doi.org/10.1159/000447478.

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Turtle karyotypes are highly conserved compared to other vertebrates; yet, variation in diploid number (2n = 26-68) reflects profound genomic reorganization, which correlates with evolutionary turnovers in sex determination. We evaluate the published literature and newly collected comparative cytogenetic data (G- and C-banding, 18S-NOR, and telomere-FISH mapping) from 13 species spanning 2n = 28-68 to revisit turtle genome evolution and sex determination. Interstitial telomeric sites were detected in multiple lineages that underwent diploid number and sex determination turnovers, suggesting chromosomal rearrangements. C-banding revealed potential interspecific variation in centromere composition and interstitial heterochromatin at secondary constrictions. 18S-NORs were detected in secondary constrictions in a single chromosomal pair per species, refuting previous reports of multiple NORs in turtles. 18S-NORs are linked to ZW chromosomes in Apalone and Pelodiscus and to X (not Y) in Staurotypus. Notably, comparative genomics across amniotes revealed that the sex chromosomes of several turtles, as well as mammals and some lizards, are homologous to components of Xenopus tropicalis XTR1 (carrying Dmrt1). Other turtle sex chromosomes are homologous to XTR4 (carrying Wt1). Interestingly, all known turtle sex chromosomes, except in Trionychidae, evolved via inversions around Dmrt1 or Wt1. Thus, XTR1 appears to represent an amniote proto-sex chromosome (perhaps linked ancestrally to XTR4) that gave rise to turtle and other amniote sex chromosomes.

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20

Maddin, Hillary C., and Robert R. Reisz. "The morphology of the terminal phalanges in Permo-Carboniferous synapsids: an evolutionary perspective." Canadian Journal of Earth Sciences 44, no. 2 (2007): 267–74. http://dx.doi.org/10.1139/e06-076.

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Morphological features of the terminal phalanges of extinct tetrapods can be used to infer whether or not keratinous claws were present even though these structures are not preserved in the fossil record. Such features as dense vascularization grooves and foramina, and a general claw-like morphology, are present in some of the earliest fully terrestrial tetrapods, the Permo-Carboniferous synapsids. Early synapsids are represented by a rich fossil record that preserves the detailed anatomy of the terminal phalanges and allows for an examination of the early evolution of these structures in a well-resolved phylogenetic context. The pattern of change in the morphology of the terminal phalanges of five basal synapsids, Cotylorhynchus romeri, Varanops sp., Edaphosaurus boanerges, Haptodus garnettensis, and Dimetrodon limbatus, reveals a clear trend from a broad, flat, and spatulate morphology in the basal taxa to a tall, narrow, and curved structure. This trend in overall shape change does not reflect changes in feeding behaviour. The size and shape of the flexor tubercle appears to be a factor of size and function, rather than possessing a phylogenetically informative signal. The osteological features used to infer the presence of a keratinous sheath in the synapsids are also observed in the non-amniote taxon Diadectes absitus. This indicates that claws were not an amniote innovation and that they instead originated somewhere outside the crown group Amniota.

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Melstrom, Keegan M., Kenneth D. Angielczyk, Kathleen A. Ritterbush, and Randall B. Irmis. "The limits of convergence: the roles of phylogeny and dietary ecology in shaping non-avian amniote crania." Royal Society Open Science 8, no. 9 (2021): 202145. http://dx.doi.org/10.1098/rsos.202145.

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Cranial morphology is remarkably varied in living amniotes and the diversity of shapes is thought to correspond with feeding ecology, a relationship repeatedly demonstrated at smaller phylogenetic scales, but one that remains untested across amniote phylogeny. Using a combination of morphometric methods, we investigate the links between phylogenetic relationships, diet and skull shape in an expansive dataset of extant toothed amniotes: mammals, lepidosaurs and crocodylians. We find that both phylogeny and dietary ecology have statistically significant effects on cranial shape. The three major clades largely partition morphospace with limited overlap. Dietary generalists often occupy clade-specific central regions of morphospace. Some parallel changes in cranial shape occur in clades with distinct evolutionary histories but similar diets. However, members of a given clade often present distinct cranial shape solutions for a given diet, and the vast majority of species retain the unique aspects of their ancestral skull plan, underscoring the limits of morphological convergence due to ecology in amniotes. These data demonstrate that certain cranial shapes may provide functional advantages suited to particular dietary ecologies, but accounting for both phylogenetic history and ecology can provide a more nuanced approach to inferring the ecology and functional morphology of cryptic or extinct amniotes.

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22

Ruta, Marcello, and Jennifer A. Clack. "A review of Silvanerpeton miripedes, a stem amniote from the Lower Carboniferous of East Kirkton, West Lothian, Scotland." Transactions of the Royal Society of Edinburgh: Earth Sciences 97, no. 1 (2006): 31–63. http://dx.doi.org/10.1017/s0263593300001395.

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ABSTRACTPreviously described and new specimens of the anthracosaur Silvanerpeton miripedes from the Scottish Viséan of East Kirkton yield important new data which allow us to provide a more complete reconstruction of the skull roof, palate, braincase and lower jaw. A stout sacral rib and an incompletely ossified tarsus with a subquadrangular intermedium are also recorded for the first time. A remarkably well preserved humerus in extensor view shows similarities with humeri of immature specimens of the embolomere Proterogyrinus. A new cladistic analysis, built from combining characters used in two recent matrices, places Silvanerpeton in a basal position relative to embolomeres and more derived stem amniotes. Data from Silvanerpeton inform character polarity near the base of the amniote total group. We discuss some morphofunctional implications of character changes at the root of total group amniotes, acquisition of terrestrial habits, and patterns of early disparity in this clade.

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Lambertz, Markus, Kristina Grommes, Tiana Kohlsdorf, and Steven F. Perry. "Lungs of the first amniotes: why simple if they can be complex?" Biology Letters 11, no. 1 (2015): 20140848. http://dx.doi.org/10.1098/rsbl.2014.0848.

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We show—in contrast to the traditional textbook contention—that the first amniote lungs were complex, multichambered organs and that the single-chambered lungs of lizards and snakes represent a secondarily simplified rather than the plesiomorphic condition. We combine comparative anatomical and embryological data and show that shared structural principles of multichamberedness are recognizable in amniotes including all lepidosaurian taxa. Sequential intrapulmonary branching observed during early organogenesis becomes obscured during subsequent growth, resulting in a secondarily simplified, functionally single-chambered lung in lepidosaurian adults. Simplification of pulmonary structure maximized the size of the smallest air spaces and eliminated biophysically compelling surface tension problems that were associated with miniaturization evident among stem lepidosaurmorphs. The remaining amniotes, however, retained the multichambered lungs, which allowed both large surface area and high pulmonary compliance, thus initially providing a strong selective advantage for efficient respiration in terrestrial environments. Branched, multichambered lungs instead of simple, sac-like organs were part and parcel of the respiratory apparatus of the first amniotes and pivotal for their success on dry land, with the sky literally as the limit.

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LAURIN, MICHEL, and ROBERT R. REISZ. "A reevaluation of early amniote phylogeny." Zoological Journal of the Linnean Society 113, no. 2 (1995): 165–223. http://dx.doi.org/10.1111/j.1096-3642.1995.tb00932.x.

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25

Deakin, Janine E., and Tariq Ezaz. "Tracing the evolution of amniote chromosomes." Chromosoma 123, no. 3 (2014): 201–16. http://dx.doi.org/10.1007/s00412-014-0456-y.

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26

Sumida, Stuart S., and R. Eric Lombard. "The atlas-axis complex in the late Paleozoic genus Diadectes and the characteristics of the atlas-axis complex across the amphibian to amniote transition." Journal of Paleontology 65, no. 6 (1991): 973–83. http://dx.doi.org/10.1017/s002233600003328x.

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The atlas-axis complex in the Early Permian diadectomorph Diadectes is shown to be similar to those of a variety of primitive amniotes. Diadectes does not possess elements in addition to the standard complement seen in advanced batrachosaurs and primitive amniotes as previously thought. Characteristics of the complex include: paired, well-developed proatlases and atlantal neural arches, lack of atlantal neural spines, an extremely robust atlantal intercentrum, fusion of the atlantal pleurocentrum and axial intercentrum, a large anterior projection of the axial intercentrum, exclusion of the atlantal pleurocentrum from ventral exposure, fusion of axial neural arch and pleurocentrum, and a robustly developed axial neural spine. An analysis of the transformations of the atlas-axis complex in advanced anthracosaurs and primitive amniotes indicates that many of the characteristics of the complex previously thought to be definitive of amniotes or reptiles appear to be conditions common to Diadectes plus Amniota.

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Irmis, Randall B., and William G. Parker. "Unusual tetrapod teeth from the Upper Triassic Chinle Formation, Arizona, USA." Canadian Journal of Earth Sciences 42, no. 7 (2005): 1339–45. http://dx.doi.org/10.1139/e05-031.

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Two teeth collected from the Upper Triasssic Chinle Formation of northeastern Arizona are described here and named Kraterokheirodon colberti gen. et sp. nov. These teeth are novel in having an occlusal ridge with six cusps and a posterior shelf lacking dentine. Evidence for thecodont implantation of the root suggests amniote affinities for these teeth. They do not match any teeth known for basal vertebrates or basal tetrapods. Although the teeth display some affinities with "traversodont" cynodonts, there are significant differences that preclude a referral to this group. These teeth most probably represent an unknown tetrapod clade and document the presence of a large amniote previously unknown from Late Triassic terrestrial faunas.

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KEAR, BENJAMIN P., and GRAHAM E. BUDD. "New perspectives on ancient marine reptiles." Geological Magazine 151, no. 1 (2013): 5–6. http://dx.doi.org/10.1017/s0016756813000873.

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Amniotes first invaded saline lagoons and coastal seaways towards the end of the Palaeozoic (Early Permian, ~ 280 Ma: Piñeiro et al. 2012), but by the dawn of the Mesozoic (Early–Middle Triassic, ~ 250–235 Ma: Rieppel, 2002; McGowan & Motani, 2003) they had achieved a diversity of specialized body-forms requisite for an obligate oceanic lifestyle. Such an explosive ecomorphological radiation paved the way for amniote dominance of large-bodied aquatic carnivore/omnivore niches over the next 185 Ma, with some lineages (e.g. dyrosaurid crocodylomorphs and bothremydid turtles: Gaffney, Tong & Meylan, 2006; Barbosa, Kellner & Sales Viana, 2008) even persisting on into the Palaeogene (until ~ 50 Ma), and diversifying (i.e. chelonioid sea turtles: Hirayama, 1997) alongside emergent marine mammals through the Neogene (from ~ 23 Ma) and up until today.

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29

Elinson, Richard P., and James R. Stewart. "The corn snake yolk sac becomes a solid tissue filled with blood vessels and yolk-rich endodermal cells." Biology Letters 10, no. 1 (2014): 20130870. http://dx.doi.org/10.1098/rsbl.2013.0870.

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The amniote egg was a key innovation in vertebrate evolution because it supports an independent existence in terrestrial environments. The egg is provisioned with yolk, and development depends on the yolk sac for the mobilization of nutrients. We have examined the yolk sac of the corn snake Pantherophis guttatus by the dissection of living eggs. In contrast to the familiar fluid-filled sac of birds, the corn snake yolk sac invades the yolk mass to become a solid tissue. There is extensive proliferation of yolk-filled endodermal cells, which associate with a meshwork of blood vessels. These novel attributes of the yolk sac of corn snakes compared with birds suggest new pathways for the evolution of the amniote egg.

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30

Waters, Paul D., and Jennifer A. Marshall Graves. "Monotreme sex chromosomes - implications for the evolution of amniote sex chromosomes." Reproduction, Fertility and Development 21, no. 8 (2009): 943. http://dx.doi.org/10.1071/rd09250.

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In vertebrates, a highly conserved pathway of genetic events controls male and female development, to the extent that many genes involved in human sex determination are also involved in fish sex determination. Surprisingly, the master switch to this pathway, which intuitively could be considered the most critical step, is inconsistent between vertebrate taxa. Interspersed in the vertebrate tree there are species that determine sex by environmental cues such as the temperature at which eggs are incubated, and then there are genetic sex-determination systems, with male heterogametic species (XY systems) and female heterogametic species (ZW systems), some of which have heteromorphic, and others homomorphic, sex chromosomes. This plasticity of sex-determining switches in vertebrates has made tracking the events of sex chromosome evolution in amniotes a daunting task, but comparative gene mapping is beginning to reveal some striking similarities across even distant taxa. In particular, the recent completion of the platypus genome sequence has completely changed our understanding of when the therian mammal X and Y chromosomes first arose (they are up to 150 million years younger than previously thought) and has also revealed the unexpected insight that sex determination of the amniote ancestor might have been controlled by a bird-like ZW system.

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31

Jeffery, Jonathan E., Olaf R. P. Bininda-Emonds, Michael I. Coates, and Michael K. Richardson. "Analyzing evolutionary patterns in amniote embryonic development*." Evolution and Development 4, no. 4 (2002): 292–302. http://dx.doi.org/10.1046/j.1525-142x.2002.02018.x.

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32

Wu, Xiao-Chun, Zhan Li, Bao-Chun Zhou, and Zhi-Ming Dong. "A polydactylous amniote from the Triassic period." Nature 426, no. 6966 (2003): 516. http://dx.doi.org/10.1038/426516a.

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33

Wu, Ping, Lianhai Hou, Maksim Plikus, et al. "Evo-Devo of amniote integuments and appendages." International Journal of Developmental Biology 48, no. 2-3 (2004): 249–70. http://dx.doi.org/10.1387/ijdb.15272390.

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34

Gauthier, Jacques, Arnold G. Kluge, and Timothy Rowe. "AMNIOTE PHYLOGENY AND THE IMPORTANCE OF FOSSILS." Cladistics 4, no. 2 (1988): 105–209. http://dx.doi.org/10.1111/j.1096-0031.1988.tb00514.x.

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35

Costantini, Maria, Gonzalo Greif, Fernando Alvarez-Valin, and Giorgio Bernardi. "TheAnolisLizard Genome: An Amniote Genome without Isochores?" Genome Biology and Evolution 8, no. 4 (2016): 1048–55. http://dx.doi.org/10.1093/gbe/evw056.

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36

Hedges, S. Blair, and Linda R. Maxson. "Re: Molecules and Morphology in Amniote Phylogeny." Molecular Phylogenetics and Evolution 6, no. 2 (1996): 312–14. http://dx.doi.org/10.1006/mpev.1996.0079.

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37

Scaal, Martin. "Development of the amniote ventrolateral body wall." Developmental Dynamics 250, no. 1 (2020): 39–59. http://dx.doi.org/10.1002/dvdy.193.

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38

Singchat, Worapong, Thitipong Panthum, Syed Farhan Ahmad, et al. "Remnant of Unrelated Amniote Sex Chromosomal Linkage Sharing on the Same Chromosome in House Gecko Lizards, Providing a Better Understanding of the Ancestral Super-Sex Chromosome." Cells 10, no. 11 (2021): 2969. http://dx.doi.org/10.3390/cells10112969.

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Comparative chromosome maps investigating sex chromosomal linkage groups in amniotes and microsatellite repeat motifs of a male house gecko lizard (Hemidactylus frenatus, HFR) and a flat-tailed house gecko lizard (H. platyurus, HPL) of unknown sex were examined using 75 bacterial artificial chromosomes (BACs) from chicken and zebra finch genomes. No massive accumulations of microsatellite repeat motifs were found in either of the gecko lizards, but 10 out of 13 BACs mapped on HPL chromosomes were associated with other amniote sex chromosomes. Hybridization of the same BACs onto multiple different chromosome pairs suggested transitions to sex chromosomes across amniotes. No BAC hybridization signals were found on HFR chromosomes. However, HFR diverged from HPL about 30 million years ago, possibly due to intrachromosomal rearrangements occurring in the HFR lineage. By contrast, heterochromatin likely reshuffled patterns between HPL and HFR, as observed from C-positive heterochromatin distribution. Six out of ten BACs showed partial homology with squamate reptile chromosome 2 (SR2) and snake Z and/or W sex chromosomes. The gecko lizard showed shared unrelated sex chromosomal linkages—the remnants of a super-sex chromosome. A large ancestral super-sex chromosome showed a correlation between SR2 and snake W sex chromosomes.

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Ahmad, Syed, Worapong Singchat, Maryam Jehangir, Thitipong Panthum, and Kornsorn Srikulnath. "Consequence of Paradigm Shift with Repeat Landscapes in Reptiles: Powerful Facilitators of Chromosomal Rearrangements for Diversity and Evolution." Genes 11, no. 7 (2020): 827. http://dx.doi.org/10.3390/genes11070827.

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Reptiles are notable for the extensive genomic diversity and species richness among amniote classes, but there is nevertheless a need for detailed genome-scale studies. Although the monophyletic amniotes have recently been a focus of attention through an increasing number of genome sequencing projects, the abundant repetitive portion of the genome, termed the “repeatome”, remains poorly understood across different lineages. Consisting predominantly of transposable elements or mobile and satellite sequences, these repeat elements are considered crucial in causing chromosomal rearrangements that lead to genomic diversity and evolution. Here, we propose major repeat landscapes in representative reptilian species, highlighting their evolutionary dynamics and role in mediating chromosomal rearrangements. Distinct karyotype variability, which is typically a conspicuous feature of reptile genomes, is discussed, with a particular focus on rearrangements correlated with evolutionary reorganization of micro- and macrochromosomes and sex chromosomes. The exceptional karyotype variation and extreme genomic diversity of reptiles are used to test several hypotheses concerning genomic structure, function, and evolution.

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40

Plöger, Ruben, and Christoph Viebahn. "Expression patterns of signalling molecules and transcription factors in the early rabbit embryo and their significance for modelling amniote axis formation." Development Genes and Evolution 231, no. 3-4 (2021): 73–83. http://dx.doi.org/10.1007/s00427-021-00677-w.

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AbstractThe anterior-posterior axis is a central element of the body plan and, during amniote gastrulation, forms through several transient domains with specific morphogenetic activities. In the chick, experimentally proven activity of signalling molecules and transcription factors lead to the concept of a ‘global positioning system’ for initial axis formation whereas in the (mammotypical) rabbit embryo, a series of morphological or molecular domains are part of a putative ‘three-anchor-point model’. Because circular expression patterns of genes involved in axis formation exist in both amniote groups prior to, and during, gastrulation and may thus be suited to reconcile these models, the expression patterns of selected genes known in the chick, namely the ones coding for the transcription factors eomes and tbx6, the signalling molecule wnt3 and the wnt inhibitor pkdcc, were analysed in the rabbit embryonic disc using in situ hybridisation and placing emphasis on their germ layer location. Peripheral wnt3 and eomes expression in all layers is found initially to be complementary to central pkdcc expression in the hypoblast during early axis formation. Pkdcc then appears — together with a posterior-anterior gradient in wnt3 and eomes domains — in the epiblast posteriorly before the emerging primitive streak is marked by pkdcc and tbx6 at its anterior and posterior extremities, respectively. Conserved circular expression patterns deduced from some of this data may point to shared mechanisms in amniote axis formation while the reshaping of localised gene expression patterns is discussed as part of the ‘three-anchor-point model’ for establishing the mammalian body plan.

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41

Sakamoto, Manabu, Marcello Ruta, and Chris Venditti. "Extreme and rapid bursts of functional adaptations shape bite force in amniotes." Proceedings of the Royal Society B: Biological Sciences 286, no. 1894 (2019): 20181932. http://dx.doi.org/10.1098/rspb.2018.1932.

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Adaptation is the fundamental driver of functional and biomechanical evolution. Accordingly, the states of biomechanical traits (absolute or relative trait values) have long been used as proxies for adaptations in response to direct selection. However, ignoring evolutionary history, in particular ancestry, passage of time and the rate of evolution, can be misleading. Here, we apply a recently developed phylogenetic statistical approach using significant rate shifts to detect instances of exceptional rates of adaptive changes in bite force in a large group of terrestrial vertebrates, the amniotes. Our results show that bite force in amniotes evolved through multiple bursts of exceptional rates of adaptive changes, whereby whole groups—including Darwin's finches, maniraptoran dinosaurs (group of non-avian dinosaurs including birds), anthropoids and hominins (fossil and modern humans)—experienced significant rate increases compared to the background rate. However, in most parts of the amniote tree of life, we find no exceptional rate increases, indicating that coevolution with body size was primarily responsible for the patterns observed in bite force. Our approach represents a template for future studies in functional morphology and biomechanics, where exceptional rates of adaptive changes can be quantified and potentially linked to specific ecological factors underpinning major evolutionary radiations.

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42

BERMAN, DAVID S. "ORIGIN AND EARLY EVOLUTION OF THE AMNIOTE OCCIPUT." Journal of Paleontology 74, no. 5 (2000): 938–56. http://dx.doi.org/10.1666/0022-3360(2000)074<0938:oaeeot>2.0.co;2.

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43

Starck, J. Matthias, James R. Stewart, and Daniel G. Blackburn. "Phylogeny and evolutionary history of the amniote egg." Journal of Morphology 282, no. 7 (2021): 1080–122. http://dx.doi.org/10.1002/jmor.21380.

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44

Houssaye, Alexandra, Paul Tafforeau, and Anthony Herrel. "Amniote vertebral microanatomy - what are the major trends?" Biological Journal of the Linnean Society 112, no. 4 (2014): 735–46. http://dx.doi.org/10.1111/bij.12311.

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45

Nyakatura, John A., Kamilo Melo, Tomislav Horvat, et al. "Reverse-engineering the locomotion of a stem amniote." Nature 565, no. 7739 (2019): 351–55. http://dx.doi.org/10.1038/s41586-018-0851-2.

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46

Szczygielski, Tomasz, Dawid Surmik, Agnieszka Kapuścińska, and Bruce M. Rothschild. "The oldest record of aquatic amniote congenital scoliosis." PLOS ONE 12, no. 9 (2017): e0185338. http://dx.doi.org/10.1371/journal.pone.0185338.

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47

Salas, Cosme, Cristina Broglio, and Fernando Rodríguez. "Conserved functional organization of the amniote telencephalic pallium." Behavioral and Brain Sciences 26, no. 5 (2003): 568–69. http://dx.doi.org/10.1017/s0140525x03380124.

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The dorsal and medial pallial formations of mammals, birds, and reptiles show overall functional striking similarities. Most of these similarities have been frequently considered examples of convergent evolution. However, a considerable amount of neurobiological comparative evidence suggests the presence of a common basic pattern of vertebrate forebrain organization. This common pattern can support functional conservation.

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48

Gredler, Marissa L. "Developmental and Evolutionary Origins of the Amniote Phallus." Integrative and Comparative Biology 56, no. 4 (2016): 694–704. http://dx.doi.org/10.1093/icb/icw102.

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49

Ouangraoua, Aïda, Eric Tannier, and Cedric Chauve. "Reconstructing the architecture of the ancestral amniote genome." Bioinformatics 27, no. 19 (2011): 2664–71. http://dx.doi.org/10.1093/bioinformatics/btr461.

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50

Wilkinson, Mark, Michael K. Richardson, David J. Gower, and Oommen V. Oommen. "Extended embryo retention, caecilian oviparity and amniote origins." Journal of Natural History 36, no. 18 (2002): 2185–98. http://dx.doi.org/10.1080/00222930110071714.

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