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Early mammals prolonged life history + mammaliaform jaw evolution + monotreme evolution + s
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Ben Creisler
Jul 24, 2024, 3:19:35 PM7/24/24
to DinosaurMa...@googlegroups.com
Ben Creisler
Some recent mammal papers:
Elsa Panciroli, Roger B. J. Benson, Vincent Fernandez, Nicholas C. Fraser, Matt Humpage, Zhe-Xi Luo, Elis Newham & Stig Walsh (2024)
Jurassic fossil juvenile reveals prolonged life history in early mammals
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-024-07733-1
https://www.nature.com/articles/s41586-024-07733-1
Living mammal groups exhibit rapid juvenile growth with a cessation of growth in adulthood. Understanding the emergence of this pattern in the earliest mammaliaforms (mammals and their closest extinct relatives) is hindered by a paucity of fossils representing juvenile individuals. We report exceptionally complete juvenile and adult specimens of the Middle Jurassic docodontan Krusatodon, providing anatomical data and insights into the life history of early diverging mammaliaforms. We used synchrotron X-ray micro-computed tomography imaging of cementum growth increments in the teeth to provide evidence of pace of life in a Mesozoic mammaliaform. The adult was about 7 years and the juvenile 7 to 24 months of age at death and in the process of replacing its deciduous dentition with its final, adult generation. When analysed against a dataset of life history parameters for extant mammals, the relative sequence of adult tooth eruption was already established in Krusatodon and in the range observed in extant mammals but this development was prolonged, taking place during a longer period as part of a significantly longer maximum lifespan than extant mammals of comparable adult body mass (156 g or less). Our findings suggest that early diverging mammaliaforms did not experience the same life histories as extant small-bodied mammals and the fundamental shift to faster growth over a shorter lifespan may not have taken place in mammaliaforms until during or after the Middle Jurassic.
Jurassic fossil juvenile reveals prolonged life history in early mammals
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-024-07733-1
https://www.nature.com/articles/s41586-024-07733-1
Living mammal groups exhibit rapid juvenile growth with a cessation of growth in adulthood. Understanding the emergence of this pattern in the earliest mammaliaforms (mammals and their closest extinct relatives) is hindered by a paucity of fossils representing juvenile individuals. We report exceptionally complete juvenile and adult specimens of the Middle Jurassic docodontan Krusatodon, providing anatomical data and insights into the life history of early diverging mammaliaforms. We used synchrotron X-ray micro-computed tomography imaging of cementum growth increments in the teeth to provide evidence of pace of life in a Mesozoic mammaliaform. The adult was about 7 years and the juvenile 7 to 24 months of age at death and in the process of replacing its deciduous dentition with its final, adult generation. When analysed against a dataset of life history parameters for extant mammals, the relative sequence of adult tooth eruption was already established in Krusatodon and in the range observed in extant mammals but this development was prolonged, taking place during a longer period as part of a significantly longer maximum lifespan than extant mammals of comparable adult body mass (156 g or less). Our findings suggest that early diverging mammaliaforms did not experience the same life histories as extant small-bodied mammals and the fundamental shift to faster growth over a shorter lifespan may not have taken place in mammaliaforms until during or after the Middle Jurassic.
News:
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Jin Meng & Fangyuan Mao (2024)
On the earliest evolution of the mammaliaform teeth, jaw joint and middle ear
Clinical and Translational Medicine 14(7): e1768
doi: https://doi.org/10.1002/ctm2.1768
https://onlinelibrary.wiley.com/doi/10.1002/ctm2.1768
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/ctm2.1768
Excerpt:
In two studies published back-to-back in Nature, Mao et al., reported two Jurassic species that are close relatives of mammals, Feredocodon chowi and Dianoconodon youngi, and present new evidence elucidating the earliest tooth diversification of Mammaliaformes (defined as the last common ancestor of Morganucodontidae and Mammalia and all its descendants; Figure 1) and transformation of the reptilian jaw joint to the middle ear apparatus of mammals.
On the earliest evolution of the mammaliaform teeth, jaw joint and middle ear
Clinical and Translational Medicine 14(7): e1768
doi: https://doi.org/10.1002/ctm2.1768
https://onlinelibrary.wiley.com/doi/10.1002/ctm2.1768
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/ctm2.1768
Excerpt:
In two studies published back-to-back in Nature, Mao et al., reported two Jurassic species that are close relatives of mammals, Feredocodon chowi and Dianoconodon youngi, and present new evidence elucidating the earliest tooth diversification of Mammaliaformes (defined as the last common ancestor of Morganucodontidae and Mammalia and all its descendants; Figure 1) and transformation of the reptilian jaw joint to the middle ear apparatus of mammals.
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Free pdf:
Jackson Dann, Zhipeng Qu, Linda Shearwin-Whyatt, Rachel van der Ploeg and Frank Grützner (2024)
Pseudogenization of NK3 homeobox 2 (Nkx3.2) in monotremes provides insight into unique gastric anatomy and physiology
Open Biology 14(7): 240071
doi: https://doi.org/10.1098/rsob.240071
https://royalsocietypublishing.org/doi/10.1098/rsob.240071
Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rsob.240071
The enzymatic breakdown and regulation of food passage through the vertebrate antral stomach and pyloric sphincter (antropyloric region) is a trait conserved over 450 million years. Development of the structures involved is underpinned by a highly conserved signalling pathway involving the hedgehog, bone morphogenetic protein and Wingless/Int-1 (Wnt) protein families. Monotremes are one of the few vertebrate lineages where acid-based digestion has been lost, and this is consistent with the lack of genes for hydrochloric acid secretion and gastric enzymes in the genomes of the platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus) . Furthermore, these species feature unique gastric phenotypes, both with truncated and aglandular antral stomachs and the platypus with no pylorus. Here, we explore the genetic underpinning of monotreme gastric phenotypes, investigating genes important in antropyloric development using the newest monotreme genomes (mOrnAna1.pri.v4 and mTacAcu1) together with RNA-seq data. We found that the pathway constituents are generally conserved, but surprisingly, NK3 homeobox 2 (Nkx3.2) was pseudogenized in both platypus and echidna. We speculate that the unique sequence evolution of Grem1 and Bmp4 sequences in the echidna lineage may correlate with their pyloric-like restriction and that the convergent loss of gastric acid and stomach size genotypes and phenotypes in teleost and monotreme lineages may be a result of eco-evolutionary dynamics. These findings reflect the effects of gene loss on phenotypic evolution and further elucidate the genetic control of monotreme stomach anatomy and physiology.
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News:
Study shows egg-laying mammals are unique, inside and out
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