Ben Creisler
Teeth have been broadly maintained across most clades of vertebrates but have been lost completely at least once in actinopterygian fishes and several times in amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.
Chromosome-level assembly of the largest vertebrate genome reported to date
Continuous expansion of transposons contributed to the huge lungfish genome
Genetic changes enhanced respiration, locomotion, and anxiolytic ability
Three genetic innovation steps from bony fishes to lungfishes and then tetrapods
Summary
Lungfishes are the closest extant relatives of tetrapods and preserve ancestral traits linked with the water-to-land transition. However, their huge genome sizes have hindered understanding of this key transition in evolution. Here, we report a 40-Gb chromosome-level assembly of the African lungfish (Protopterus annectens) genome, which is the largest genome assembly ever reported and has a contig and chromosome N50 of 1.60 Mb and 2.81 Gb, respectively. The large size of the lungfish genome is due mainly to retrotransposons. Genes with ultra-long length show similar _expression_ levels to other genes, indicating that lungfishes have evolved high transcription efficacy to keep gene _expression_ balanced. Together with transcriptome and experimental data, we identified potential genes and regulatory elements related to such terrestrial adaptation traits as pulmonary surfactant, anxiolytic ability, pentadactyl limbs, and pharyngeal remodeling. Our results provide insights and key resources for understanding the evolutionary pathway leading from fishes to humans.
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A new species of the actinopterygian fish genus Saurichthys is described on the basis of several specimens from the Sceltrich beds (Meride Limestone Formation) of the UNESCO World Heritage area of Monte San Giorgio. The new species shows among other characters, unsegmented lepidotrichia in all fins and elongated and wide paired fins, suggesting a different adaptation for swimming and catching preys with respect to other Saurichthys species of Monte San Giorgio. Phylogenetic analysis suggests that the new species is closely related to the Saurorhynchus species group. The new finding adds further knowledge to the plasticity and functional adaptations of the genus Saurichthys, which was one of the most successful actinopterygians of the Triassic.
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Some recent non-dino papers:
Eric Buffetaut and Delphine Angst (2021)
Macrornis tanaupus Seeley, 1866: an enigmatic giant bird from the upper Eocene of England.
Geological Magazine (advance online publication)
DOI: https://doi.org/10.1017/S0016756820001466
https://www.cambridge.org/core/journals/geological-magazine/article/abs/macrornis-tanaupus-seeley-1866-an-enigmatic-giant-bird-from-the-upper-eocene-of-england/644A645383E9E2BD2B5DD1654AE3FD30
A large bone from the upper Eocene Totland Bay Formation of Hordle Cliff (Hampshire), originally described by Seeley (1866) as Macrornis tanaupus and interpreted by him as belonging to a 'large Struthious bird', is redescribed and illustrated for the first time. It is not a reptile bone, as previously suggested, but the proximal part of a left avian tibiotarsus. A mass estimate of 43 kg, comparable to that of an emu, suggests that it was flightless. A precise identification is difficult because of the incompleteness of the specimen, and Macrornis tanaupus should probably be considered as a nomen dubium. We exclude Seeleyâs interpretation as a ratite, as well as previous attributions to gastornithids. We tentatively suggest that the specimen may belong to a phorusrhacid, which would extend the stratigraphic record of this group in Europe by a few million years. The presence of a large terrestrial bird in the upper Eocene of Europe may have a bearing on the interpretation of enigmatic footprints of very large birds from the upper Eocene Paris gypsum.
======
Li Li, Hou Shilin, Wang Jingqi & Yu Jia (2020)
Statistics and description of the sternum morphology of Confucius collected in the Liaoning Paleontology Museum.
Journal of Shenyang Normal University (Natural Science Edition) 38(6):
https://tow.cnki.net/kcms/detail/detail.aspx?filename=SYSX202006014&dbcode=CRJT_CJFD&dbname=CJFDAUTO&v=
Confuciusornithids lived about 120-131 Ma years ago,which were the largest number of primitive birds found so far and thousands of fossil specimens have been discovered. 51 fossils of Confuciusornithids kept in the museum were arranged comprehensively and some information on these fossils is documented in detail including the locality,preservation status in this paper. The sternums of Confuciusornithids were observed and described. There are 11 specimens that are preserved with sternums in good status and the shapes are clear among all items. These specimens include items with simple structured sternums without obvious carina sterni; slightly complex structured stermums with carina sterni existing on rear part and length is greater than width; and more complex structured sternums with obvious carina sterni existing on whole sternum and with lateral process. There are 40 specimens preserved without sternums or with incomplete sternums, which infers preliminarily that the absence of sternum might be related to the thick bone slice and undeveloped articulated structure, and all the features reveal the primitiveness of Confuciusornithids. Reference material can be provided for the evolution and extinction of primitive birds in this paper.
Amniote tails display a wide variety of features for adaptation to diverse environments. Each feature originates from its own distinct developmental processes, and these processes in turn attest to an organismâs evolutionary history. In this perspective, we discuss the ontogeny of tails from embryonic to adult stages, amniote tail regeneration, the mechanisms underlying tail length and neural systems, and the benefits of studying tails across vertebrates, in mammals, birds, and nonâavian reptiles.
====
Marco Camaiti, Alistair R. Evans, Christy A. Hipsley & David G. Chapple (2021)
A farewell to arms and legs: a review of limb reduction in squamates.
Biological Reviews
doi: https://doi.org/10.1111/brv.12690
https://onlinelibrary.wiley.com/doi/10.1111/brv.12690
Elongated snakeâlike bodies associated with limb reduction have evolved multiple times throughout vertebrate history. Limbâreduced squamates (lizards and snakes) account for the vast majority of these morphological transformations, and thus have great potential for revealing macroevolutionary transitions and modes of bodyâshape transformation. Here we present a comprehensive review on limb reduction, in which we examine and discuss research on these dramatic morphological transitions. Historically, there have been several approaches to the study of squamate limb reduction: (i) definitions of general anatomical principles of snakeâlike body shapes, expressed as varying relationships between body parts and morphometric measurements; (ii) framing of limb reduction from an evolutionary perspective using morphological comparisons; (iii) defining developmental mechanisms involved in the ontogeny of limbâreduced forms, and their genetic basis; (iv) reconstructions of the evolutionary history of limbâreduced lineages using phylogenetic comparative methods; (v) studies of functional and biomechanical aspects of limbâreduced body shapes; and (vi) studies of ecological and biogeographical correlates of limb reduction. For each of these approaches, we highlight their importance in advancing our understanding, as well as their weaknesses and limitations. Lastly, we provide suggestions to stimulate further studies, in which we underscore the necessity of widening the scope of analyses, and of bringing together different perspectives in order to understand better these morphological transitions and their evolution. In particular, we emphasise the importance of investigating and comparing the internal morphology of limbâreduced lizards in contrast to external morphology, which will be the first step in gaining a deeper insight into bodyâshape variation.
====
Daniel J Paluh, Karina Riddell, Catherine M Early, Maggie M Hantak, Gregory FM Jongsma, Rachel M Keeffe, Fernanda MagalhÃes Silva, Stuart V Nielsen, MarÃa Camila Vallejo-Pareja, Edward L Stanley & David C Blackburn (2021)
=============
Eric Buffetaut and Delphine Angst (2021)
Macrornis tanaupus Seeley, 1866: an enigmatic giant bird from the upper Eocene of England.
Geological Magazine (advance online publication)
DOI: https://doi.org/10.1017/S0016756820001466
https://www.cambridge.org/core/journals/geological-magazine/article/abs/macrornis-tanaupus-seeley-1866-an-enigmatic-giant-bird-from-the-upper-eocene-of-england/644A645383E9E2BD2B5DD1654AE3FD30
A large bone from the upper Eocene Totland Bay Formation of Hordle Cliff (Hampshire), originally described by Seeley (1866) as Macrornis tanaupus and interpreted by him as belonging to a 'large Struthious bird', is redescribed and illustrated for the first time. It is not a reptile bone, as previously suggested, but the proximal part of a left avian tibiotarsus. A mass estimate of 43 kg, comparable to that of an emu, suggests that it was flightless. A precise identification is difficult because of the incompleteness of the specimen, and Macrornis tanaupus should probably be considered as a nomen dubium. We exclude Seeleyâs interpretation as a ratite, as well as previous attributions to gastornithids. We tentatively suggest that the specimen may belong to a phorusrhacid, which would extend the stratigraphic record of this group in Europe by a few million years. The presence of a large terrestrial bird in the upper Eocene of Europe may have a bearing on the interpretation of enigmatic footprints of very large birds from the upper Eocene Paris gypsum.
======
In Chinese:
(I could not find a free pdf link for this one...)
Li Li, Hou Shilin, Wang Jingqi & Yu Jia (2020)
Statistics and description of the sternum morphology of Confucius collected in the Liaoning Paleontology Museum.
Journal of Shenyang Normal University (Natural Science Edition) 38(6):
https://tow.cnki.net/kcms/detail/detail.aspx?filename=SYSX202006014&dbcode=CRJT_CJFD&dbname=CJFDAUTO&v=
Confuciusornithids lived about 120-131 Ma years ago,which were the largest number of primitive birds found so far and thousands of fossil specimens have been discovered. 51 fossils of Confuciusornithids kept in the museum were arranged comprehensively and some information on these fossils is documented in detail including the locality,preservation status in this paper. The sternums of Confuciusornithids were observed and described. There are 11 specimens that are preserved with sternums in good status and the shapes are clear among all items. These specimens include items with simple structured sternums without obvious carina sterni; slightly complex structured stermums with carina sterni existing on rear part and length is greater than width; and more complex structured sternums with obvious carina sterni existing on whole sternum and with lateral process. There are 40 specimens preserved without sternums or with incomplete sternums, which infers preliminarily that the absence of sternum might be related to the thick bone slice and undeveloped articulated structure, and all the features reveal the primitiveness of Confuciusornithids. Reference material can be provided for the evolution and extinction of primitive birds in this paper.
===
Dana J. Rashid & Susan C. Chapman (2021)
The long and the short of tails
Developmental Dynamics (advance online publication)
doi: https://doi.org/10.1002/dvdy.311
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/dvdy.311
The long and the short of tails
Developmental Dynamics (advance online publication)
doi: https://doi.org/10.1002/dvdy.311
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/dvdy.311
Amniote tails display a wide variety of features for adaptation to diverse environments. Each feature originates from its own distinct developmental processes, and these processes in turn attest to an organismâs evolutionary history. In this perspective, we discuss the ontogeny of tails from embryonic to adult stages, amniote tail regeneration, the mechanisms underlying tail length and neural systems, and the benefits of studying tails across vertebrates, in mammals, birds, and nonâavian reptiles.
====
Marco Camaiti, Alistair R. Evans, Christy A. Hipsley & David G. Chapple (2021)
A farewell to arms and legs: a review of limb reduction in squamates.
Biological Reviews
doi: https://doi.org/10.1111/brv.12690
https://onlinelibrary.wiley.com/doi/10.1111/brv.12690
Elongated snakeâlike bodies associated with limb reduction have evolved multiple times throughout vertebrate history. Limbâreduced squamates (lizards and snakes) account for the vast majority of these morphological transformations, and thus have great potential for revealing macroevolutionary transitions and modes of bodyâshape transformation. Here we present a comprehensive review on limb reduction, in which we examine and discuss research on these dramatic morphological transitions. Historically, there have been several approaches to the study of squamate limb reduction: (i) definitions of general anatomical principles of snakeâlike body shapes, expressed as varying relationships between body parts and morphometric measurements; (ii) framing of limb reduction from an evolutionary perspective using morphological comparisons; (iii) defining developmental mechanisms involved in the ontogeny of limbâreduced forms, and their genetic basis; (iv) reconstructions of the evolutionary history of limbâreduced lineages using phylogenetic comparative methods; (v) studies of functional and biomechanical aspects of limbâreduced body shapes; and (vi) studies of ecological and biogeographical correlates of limb reduction. For each of these approaches, we highlight their importance in advancing our understanding, as well as their weaknesses and limitations. Lastly, we provide suggestions to stimulate further studies, in which we underscore the necessity of widening the scope of analyses, and of bringing together different perspectives in order to understand better these morphological transitions and their evolution. In particular, we emphasise the importance of investigating and comparing the internal morphology of limbâreduced lizards in contrast to external morphology, which will be the first step in gaining a deeper insight into bodyâshape variation.
====
Daniel J Paluh, Karina Riddell, Catherine M Early, Maggie M Hantak, Gregory FM Jongsma, Rachel M Keeffe, Fernanda MagalhÃes Silva, Stuart V Nielsen, MarÃa Camila Vallejo-Pareja, Edward L Stanley & David C Blackburn (2021)
Rampant tooth loss across 200 million years of frog evolution.
bioRxiv 2021.02.04.429809 (preprint)
doi:Âhttps://doi.org/10.1101/2021.02.04.429809
https://www.biorxiv.org/content/10.1101/2021.02.04.429809v1
bioRxiv 2021.02.04.429809 (preprint)
doi:Âhttps://doi.org/10.1101/2021.02.04.429809
https://www.biorxiv.org/content/10.1101/2021.02.04.429809v1
Teeth have been broadly maintained across most clades of vertebrates but have been lost completely at least once in actinopterygian fishes and several times in amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.
===
(I posted the Australian lungfish Neoceratodus genome paper from Nature earlier:
Another lungfish genome paper (Protopterus) with tetrapod implications.
Kun Wang, Jun Wang, Chenglong Zhu, Liandong Yang, Yandong Ren, Jue Ruan, Guangyi Fan, Jiang Hu, Wenjie Xu, Xupeng Bi, Youan Zhu, Yue Song, Huatao Chen, Tiantian Ma, Ruoping Zhao, Haifeng Jiang, Bin Zhang, Chenguang Feng, Yuan Yuan, Xiaoni Gan, Yongxin Li, Honghui Zeng, Qun Liu, Yaolei Zhang, Feng Shao, Shijie Hao, He Zhang, Xun Xu, Xin Liu, Depeng Wang, Min Zhu, Guojie Zhang, Wenming Zhao, Qiang Qiu, Shunping He & Wen Wang (2021)
Tracing the genetic footprints of vertebrate landing in non-teleost ray-finned fishes.
Cell (advance online publication)
DOI: https://doi.org/10.1016/j.cell.2021.01.047
https://www.sciencedirect.com/science/article/abs/pii/S0092867421000908
https://www.cell.com/cell/fulltext/S0092-8674(21)00090-8
Highlights
Tracing the genetic footprints of vertebrate landing in non-teleost ray-finned fishes.
Cell (advance online publication)
DOI: https://doi.org/10.1016/j.cell.2021.01.047
https://www.sciencedirect.com/science/article/abs/pii/S0092867421000908
https://www.cell.com/cell/fulltext/S0092-8674(21)00090-8
Highlights
Chromosome-level assembly of the largest vertebrate genome reported to date
Continuous expansion of transposons contributed to the huge lungfish genome
Genetic changes enhanced respiration, locomotion, and anxiolytic ability
Three genetic innovation steps from bony fishes to lungfishes and then tetrapods
Summary
Lungfishes are the closest extant relatives of tetrapods and preserve ancestral traits linked with the water-to-land transition. However, their huge genome sizes have hindered understanding of this key transition in evolution. Here, we report a 40-Gb chromosome-level assembly of the African lungfish (Protopterus annectens) genome, which is the largest genome assembly ever reported and has a contig and chromosome N50 of 1.60 Mb and 2.81 Gb, respectively. The large size of the lungfish genome is due mainly to retrotransposons. Genes with ultra-long length show similar _expression_ levels to other genes, indicating that lungfishes have evolved high transcription efficacy to keep gene _expression_ balanced. Together with transcriptome and experimental data, we identified potential genes and regulatory elements related to such terrestrial adaptation traits as pulmonary surfactant, anxiolytic ability, pentadactyl limbs, and pharyngeal remodeling. Our results provide insights and key resources for understanding the evolutionary pathway leading from fishes to humans.
News:
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Saurichthys sceltrichensis sp. n.
Silvio Renesto, Fabio Magnani & Rudolf Stockar (2021)
A new species of Saurichthys (Actinopterygii: Saurichtydae) from the Middle Triassic of Monte San Giorgio.
Rivista Italiana di Paleontologia e Stratigrafia 127(1): 49-71.
DOI: https://doi.org/10.13130/2039-4942/15143
https://riviste.unimi.it/index.php/RIPS/article/view/15143
Free pdf:
https://riviste.unimi.it/index.php/RIPS/article/view/15143/14006
A new species of Saurichthys (Actinopterygii: Saurichtydae) from the Middle Triassic of Monte San Giorgio.
Rivista Italiana di Paleontologia e Stratigrafia 127(1): 49-71.
DOI: https://doi.org/10.13130/2039-4942/15143
https://riviste.unimi.it/index.php/RIPS/article/view/15143
Free pdf:
https://riviste.unimi.it/index.php/RIPS/article/view/15143/14006
A new species of the actinopterygian fish genus Saurichthys is described on the basis of several specimens from the Sceltrich beds (Meride Limestone Formation) of the UNESCO World Heritage area of Monte San Giorgio. The new species shows among other characters, unsegmented lepidotrichia in all fins and elongated and wide paired fins, suggesting a different adaptation for swimming and catching preys with respect to other Saurichthys species of Monte San Giorgio. Phylogenetic analysis suggests that the new species is closely related to the Saurorhynchus species group. The new finding adds further knowledge to the plasticity and functional adaptations of the genus Saurichthys, which was one of the most successful actinopterygians of the Triassic.
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