Ben Creisler
Some recent non-dino papers:
Pareiasaurs were one of the main clades of large herbivorous tetrapods in Middle-Late Permian continental ecosystems. Despite abundant pareiasaur material, many aspects of their biology remain poorly known. This paper provides a description of ontogenetic changes in long-bone and rib microanatomy/histology of two Upper Permian pareiasaurs from Russia, Deltavjatia rossica and Scutosaurus karpinskii. Analysis of a growth series of bones of Deltavjatia and Scutosaurus revealed rapid and cyclical growth early in ontogeny (as indicated by fast-growing fibrolamellar bone with lines of arrested growth). This was followed by a change in the growth pattern (as indicated by an outer avascular layer of lamellar bone in the cortex) and a decrease in the growth rate after 50% of maximum body size was reached in Deltavjatia and 75% in Scutosaurus (larger body sizes in Scutosaurus were attained through an extended initial period of fast skeletal growth). The study confirms that the bones of all pareiasaurs are histologically and microanatomically uniform [spongious (porous) microstructure and a very thin compact cortex] and indicate a similar growth strategy (a short initial period of rapid and cyclical growth followed by a long period of slow growth). The microanatomical characteristics of pareiasaurs do not provide a clear indication of their lifestyle.
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Free pdf:
Now out in final form (posted earlier):
Free pdf (new url):
http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201905/P020190705562624543520.pdfThe Permian dicynodont records were previously rare in North China, but many dicynodont specimens have been collected from the Naobaogou Formation in Daqingshan area, Nei Mongol since 2009. Among these specimens, seven morphotypes have been identified, and they may represent seven different species: two of them are closely related to Daqingshanodon limbus, three or four are closely related to Jimusaria sinkianensis, and one may be closely related to Turfanodon. This study shows the dicynodonts also have a high diversity at the species level in North China.Â
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Sylvain Darnet, Aline C. Dragalzew, Danielson B. Amaral, Josane F. Sousa, Andrew W. Thompson, Amanda N. Cass, Jamily Lorena, Eder S. Pires, Carinne M. Costa, Marcos P. Sousa, Nadia B. FrÃbisch, Guilherme Oliveira, Patricia N. Schneider, Marcus C. Davis, Ingo Braasch, and Igor Schneider (2019)
Deep evolutionary origin of limb and fin regeneration.
Proceedings of the National Academy of Sciences (advance online publication)
doi:
https://doi.org/10.1073/pnas.1900475116https://www.pnas.org/content/early/2019/07/02/1900475116Significance
Salamanders and lungfishes are the only lobe-finned vertebrates where appendage regeneration after endoskeleton amputation has been demonstrated. Here we show that paired-fin regeneration after endoskeleton amputation occurs in living representatives of all major actinopterygian clades: the American paddlefish (Chondrostei), the spotted gar (Holostei), and in 2 cichlid and 1 cyprinid species (Teleostei). Through comparative transcriptome analysis of blastemas, we demonstrate that axolotl and Polypterus deploy a similar genetic program during regeneration. Furthermore, we show that early blastemas in both species activate a common regeneration-specific genetic program. Collectively, our findings support a deep evolutionary origin of limb and fin regeneration and highlight the strengths of a comparative approach to identify genetic signatures of vertebrate appendage regeneration.
Abstract
Salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of paired appendage regeneration, regardless of the amputation level. Among actinopterygians (ray-finned fishes), regeneration after amputation at the fin endoskeleton has only been demonstrated in polypterid fishes (Cladistia). Whether this ability evolved independently in sarcopterygians and actinopterygians or has a common origin remains unknown. Here we combine fin regeneration assays and comparative RNA-sequencing (RNA-seq) analysis of Polypterus and axolotl blastemas to provide support for a common origin of paired appendage regeneration in Osteichthyes (bony vertebrates). We show that, in addition to polypterids, regeneration after fin endoskeleton amputation occurs in extant representatives of 2 other nonteleost actinopterygians: the American paddlefish (Chondrostei) and the spotted gar (Holostei). Furthermore, we assessed regeneration in 4 teleost species and show that, with the exception of the blue gourami (Anabantidae), 3 species were capable of regenerating fins after endoskeleton amputation: the white convict and the oscar (Cichlidae), and the goldfish (Cyprinidae). Our comparative RNA-seq analysis of regenerating blastemas of axolotl and Polypterus reveals the activation of common genetic pathways and _expression_ profiles, consistent with a shared genetic program of appendage regeneration. Comparison of RNA-seq data from early Polypterus blastema to single-cell RNA-seq data from axolotl limb bud and limb regeneration stages shows that Polypterus and axolotl share a regeneration-specific genetic program. Collectively, our findings support a deep evolutionary origin of paired appendage regeneration in Osteichthyes and provide an evolutionary framework for studies on the genetic basis of appendage regeneration.
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Non-tetrapod, but may be of interest:
Free pdf:
Patrick L. Jambura, Renà Kindlimann, Faviel LÃpez-Romero, Giuseppe MarramÃ, Cathrin Pfaff, Sebastian Stumpf, Julia TÃrtscher, Charlie J. Underwood, David J. Ward & JÃrgen Kriwet Â(2019)
Micro-computed tomography imaging reveals the development of a unique tooth mineralization pattern in mackerel sharks (Chondrichthyes; Lamniformes) in deep time.
Scientific Reports 9, Article number: 9652
DOI:
https://doi.org/10.1038/s41598-019-46081-3https://www.nature.com/articles/s41598-019-46081-3Free pdf:
https://www.nature.com/articles/s41598-019-46081-3.pdfThe cartilaginous fishes (Chondrichthyes) have a rich fossil record which consists mostly of isolated teeth and, therefore, phylogenetic relationships of extinct taxa are mainly resolved based on dental characters. One character, the tooth histology, has been examined since the 19th century, but its implications on the phylogeny of Chondrichthyes is still in debate. We used high resolution micro-CT images and tooth sections of 11 recent and seven extinct lamniform sharks to examine the tooth mineralization processes in this group. Our data showed similarities between lamniform sharks and other taxa (a dentinal core of osteodentine instead of a hollow pulp cavity), but also one feature that has not been known from any other elasmobranch fish: the absence of orthodentine. Our results suggest that this character resembles a synapomorphic condition for lamniform sharks, with the basking shark, Cetorhinus maximus, representing the only exception and reverted to the plesiomorphic tooth histotype. Additionally, âPalaeocarcharias stromeri, whose affiliation still is debated, shares the same tooth histology only known from lamniform sharks. This suggests that âPalaeocarcharias stromeri is member of the order Lamniformes, contradicting recent interpretations and thus, dating the origin of this group back at least into the Middle Jurassic.
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News:
Tracking evolution through teeth: The small-fry ancestor of the great white shark
by University of Vienna
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