Mammal radiation before and after K/P extinction + Elephantidae body proportions + mammal hearts + origin of mammals "fair tale"
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Ben Creisler
Oct 18, 2024, 3:24:04 PMOct 18
to DinosaurMa...@googlegroups.com
Ben Creisler
The research in the Wilson Lab aims to understand critical transitions in the deep-time history of life. One of the most captivating of these transitions is the early evolutionary radiation of mammals, which ultimately led to their striking diversity today, from the tiny bumblebee bat to the titanic blue whale. Specifically, we focus on how mammals evolved during the Mesozoic Era (220 to 66 million years ago), when major mammal groups originated, and fundamental changes in the anatomy, physiology, and ecology of mammals occurred. We combine paleontological and geological field work, description and systematic study of fossil specimens, and quantitative analysis of morphology, function, and ecology of extant and extinct taxa. This work elucidates the paleoecology and macroevolution of early mammals in the context of dinosaur-dominated terrestrial ecosystems, the breakup of Pangaea, and the end-Cretaceous mass extinction. In this seminar, I will summarize results from three research areas that span ecological scales from individual taxa to communities and ecosystems. A broader understanding of such ecological dynamics through time is critical to our understanding of the processes that govern ecosystem assembly and maintenance, topics that directly bear on efforts to forecast and mitigate the evolutionary and ecological consequences of our current biodiversity crisis.
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Ruslan I Belyaev, Gennady G Boeskorov, Alexander N Kuznetsov, Mathys Rotonda & Natalya E Prilepskaya (2024)
Comparative study of the body proportions in Elephantidae and other large herbivorous mammals
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.14143
https://onlinelibrary.wiley.com/doi/10.1111/joa.14143
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.14143
In this study, we aimed to achieve three objectives: (1) to precisely characterize the body plans of Elephantidae and other large herbivorous mammals; (2) based on this analysis, to determine whether the body plans of the extinct woolly mammoth (Mammuthus primigenius) and steppe mammoth (M. trogontherii) differ from those of modern-day Elephantidae: the Asian elephant (Elephas maximus), the African bush (Loxodonta africana), and forest (L. cyclotis) elephants; (3) to analyze how the body plans have changed in extant perissodactyls and proboscideans compared with their Paleogene ancestors. To accomplish this, we studied mammoth skeletons from the collections of Russian museums and compared this data with a large number of skeletons of extant elephantids, odd-toed, and even-toed ungulates, as well as their extinct relatives. We showed that three genera of Elephantidae are characterized by a homogeneous body plan, which is markedly different from other large herbivores. Elephantids break the interrelationship, that exists in artiodactyls and perissodactyls, between the total length of the head and neck on one side and the limb's segments on the other. Their limbs are very tall (inferior in this regard among large ungulates only to the giraffe), and, contrary to the other large herbivorous mammals, elongated due to the length of the proximal segments. This allows them to effectively utilize the principle of inverted pendulum (straight-legged walking) in locomotion. The biggest differences in the body plan of mammoths compared with extant elephants are a markedly larger pelvis, elongated fore- and hindlimbs (due to the increased relative length of their proximal segments), and different proportions of the skull. The body plans of plesiomorphic Paleogene proboscideans and perissodactyls differed markedly from their descendants in every body part; these differences are related, on the one hand, to the allometric growth, and on the other hand, to the advancement of the locomotor apparatus in the course of their evolution. The most notable difference in the body plan between Paleogene proboscidean Moeritherium and extant Elephantidae is the ~2-fold increase in relative limb height.
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Some recent mammal-related items:
G. Wilson Mantilla (2024, October 10)
Ecological Radiations of Mammals: Before & After the K/Pg Mass Extinction (seminar video)
36 min.
Ecological Radiations of Mammals: Before & After the K/Pg Mass Extinction (seminar video)
36 min.
doi: 10.52843/cassyni.xg75qh
The research in the Wilson Lab aims to understand critical transitions in the deep-time history of life. One of the most captivating of these transitions is the early evolutionary radiation of mammals, which ultimately led to their striking diversity today, from the tiny bumblebee bat to the titanic blue whale. Specifically, we focus on how mammals evolved during the Mesozoic Era (220 to 66 million years ago), when major mammal groups originated, and fundamental changes in the anatomy, physiology, and ecology of mammals occurred. We combine paleontological and geological field work, description and systematic study of fossil specimens, and quantitative analysis of morphology, function, and ecology of extant and extinct taxa. This work elucidates the paleoecology and macroevolution of early mammals in the context of dinosaur-dominated terrestrial ecosystems, the breakup of Pangaea, and the end-Cretaceous mass extinction. In this seminar, I will summarize results from three research areas that span ecological scales from individual taxa to communities and ecosystems. A broader understanding of such ecological dynamics through time is critical to our understanding of the processes that govern ecosystem assembly and maintenance, topics that directly bear on efforts to forecast and mitigate the evolutionary and ecological consequences of our current biodiversity crisis.
====
====
Free pdf:
Ruslan I Belyaev, Gennady G Boeskorov, Alexander N Kuznetsov, Mathys Rotonda & Natalya E Prilepskaya (2024)
Comparative study of the body proportions in Elephantidae and other large herbivorous mammals
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.14143
https://onlinelibrary.wiley.com/doi/10.1111/joa.14143
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.14143
In this study, we aimed to achieve three objectives: (1) to precisely characterize the body plans of Elephantidae and other large herbivorous mammals; (2) based on this analysis, to determine whether the body plans of the extinct woolly mammoth (Mammuthus primigenius) and steppe mammoth (M. trogontherii) differ from those of modern-day Elephantidae: the Asian elephant (Elephas maximus), the African bush (Loxodonta africana), and forest (L. cyclotis) elephants; (3) to analyze how the body plans have changed in extant perissodactyls and proboscideans compared with their Paleogene ancestors. To accomplish this, we studied mammoth skeletons from the collections of Russian museums and compared this data with a large number of skeletons of extant elephantids, odd-toed, and even-toed ungulates, as well as their extinct relatives. We showed that three genera of Elephantidae are characterized by a homogeneous body plan, which is markedly different from other large herbivores. Elephantids break the interrelationship, that exists in artiodactyls and perissodactyls, between the total length of the head and neck on one side and the limb's segments on the other. Their limbs are very tall (inferior in this regard among large ungulates only to the giraffe), and, contrary to the other large herbivorous mammals, elongated due to the length of the proximal segments. This allows them to effectively utilize the principle of inverted pendulum (straight-legged walking) in locomotion. The biggest differences in the body plan of mammoths compared with extant elephants are a markedly larger pelvis, elongated fore- and hindlimbs (due to the increased relative length of their proximal segments), and different proportions of the skull. The body plans of plesiomorphic Paleogene proboscideans and perissodactyls differed markedly from their descendants in every body part; these differences are related, on the one hand, to the allometric growth, and on the other hand, to the advancement of the locomotor apparatus in the course of their evolution. The most notable difference in the body plan between Paleogene proboscidean Moeritherium and extant Elephantidae is the ~2-fold increase in relative limb height.
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Edward P. Snelling & Roger S. Seymour (2024)
The hearts of large mammals generate higher pressures, are less efficient and use more energy than those of small mammals
Journal of Experimental Biology 227(20): jeb247747
doi: https://doi.org/10.1242/jeb.247747
https://journals.biologists.com/jeb/article-abstract/227/20/jeb247747/362375/The-hearts-of-large-mammals-generate-higher
A prevailing assumption in the cardiovascular field is that the metabolic rate of the heart is a constant proportion of a mammal's whole-body aerobic metabolic rate. In this Commentary, we assemble previously published cardiovascular, metabolic and body mass data from matched terrestrial mammalian species, at rest and during heavy exercise, and reveal scaling relationships that challenge this assumption. Our analyses indicate that the fractional metabolic cost of systemic perfusion compared with whole-body metabolic rate increases significantly with body size among resting mammals, from ∼2.5% in a mouse to ∼10% in an elephant. We propose that two significant body size-dependent effects contribute to this conclusion; namely, that larger species generate higher mean systemic arterial blood pressure and that their myocardium operates with lower external mechanical efficiencies compared with those of smaller species. We discuss potential physiological and mechanical explanations, including the additional energy needed to support the arterial blood column above the heart in larger species, especially those with long necks, as well as the possible sources of greater internal energy losses from the heart of larger species. Thus, we present an updated view of how increasing blood pressure and decreasing efficiency of the myocardium result in an increasing fractional metabolic cost of perfusion as body size increases among resting mammals.
The hearts of large mammals generate higher pressures, are less efficient and use more energy than those of small mammals
Journal of Experimental Biology 227(20): jeb247747
doi: https://doi.org/10.1242/jeb.247747
https://journals.biologists.com/jeb/article-abstract/227/20/jeb247747/362375/The-hearts-of-large-mammals-generate-higher
A prevailing assumption in the cardiovascular field is that the metabolic rate of the heart is a constant proportion of a mammal's whole-body aerobic metabolic rate. In this Commentary, we assemble previously published cardiovascular, metabolic and body mass data from matched terrestrial mammalian species, at rest and during heavy exercise, and reveal scaling relationships that challenge this assumption. Our analyses indicate that the fractional metabolic cost of systemic perfusion compared with whole-body metabolic rate increases significantly with body size among resting mammals, from ∼2.5% in a mouse to ∼10% in an elephant. We propose that two significant body size-dependent effects contribute to this conclusion; namely, that larger species generate higher mean systemic arterial blood pressure and that their myocardium operates with lower external mechanical efficiencies compared with those of smaller species. We discuss potential physiological and mechanical explanations, including the additional energy needed to support the arterial blood column above the heart in larger species, especially those with long necks, as well as the possible sources of greater internal energy losses from the heart of larger species. Thus, we present an updated view of how increasing blood pressure and decreasing efficiency of the myocardium result in an increasing fractional metabolic cost of perfusion as body size increases among resting mammals.
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Charudatta Navare (2024)
A “Scientific Fairy Tale” of Origin of Mammals
Science & Education (advance online publication)
doi: https://doi.org/10.1007/s11191-024-00569-1
https://link.springer.com/article/10.1007/s11191-024-00569-1
The ranking of living beings in a hierarchical order has persisted across different cultures and philosophies for millennia. Aristotle’s “ladder of life” and the mediaeval notion of the “great chain of being” categorised organisms into “higher” and “lower” forms. While a hierarchical view of the living world was dominant in biology until the nineteenth century, modern biological thinking attempts to avoid categorising extant organisms as “higher” and “lower” or “primitive” and “advanced”. However, in this paper, I show that the “ladder of life” persists in subtle ways. Critical discourse analysis of current biology textbooks shows a linear history of life, with the “Age of Amphibians” followed by the “Age of Reptiles” and then the “Age of Mammals”. Textbooks downplay episodes in evolutionary history that seemingly counter this linear history of life, such as the “dominance” of ancient relatives of mammals before the “Age of Reptiles”. I further argue that by terming the ancient relatives of mammals as proto-mammals but dinosaurs as reptiles (not “proto-reptiles”), the “origin” of mammals is delayed, and problematise this terminology. I argue that similar to the origin stories of nations or human groups, the “origin” of taxonomic groups can be powerful tools that give an appearance of purpose for their existence. The origin of mammals as nocturnal creatures during the “age of darkness” when “monstrous” reptiles were “dominating” gives the narrative moral and political undertones. In addition to implicitly justifying the “Age of Mammals”, this linear and hierarchical history of life limits understanding of the diversity and richness of life.
A “Scientific Fairy Tale” of Origin of Mammals
Science & Education (advance online publication)
doi: https://doi.org/10.1007/s11191-024-00569-1
https://link.springer.com/article/10.1007/s11191-024-00569-1
The ranking of living beings in a hierarchical order has persisted across different cultures and philosophies for millennia. Aristotle’s “ladder of life” and the mediaeval notion of the “great chain of being” categorised organisms into “higher” and “lower” forms. While a hierarchical view of the living world was dominant in biology until the nineteenth century, modern biological thinking attempts to avoid categorising extant organisms as “higher” and “lower” or “primitive” and “advanced”. However, in this paper, I show that the “ladder of life” persists in subtle ways. Critical discourse analysis of current biology textbooks shows a linear history of life, with the “Age of Amphibians” followed by the “Age of Reptiles” and then the “Age of Mammals”. Textbooks downplay episodes in evolutionary history that seemingly counter this linear history of life, such as the “dominance” of ancient relatives of mammals before the “Age of Reptiles”. I further argue that by terming the ancient relatives of mammals as proto-mammals but dinosaurs as reptiles (not “proto-reptiles”), the “origin” of mammals is delayed, and problematise this terminology. I argue that similar to the origin stories of nations or human groups, the “origin” of taxonomic groups can be powerful tools that give an appearance of purpose for their existence. The origin of mammals as nocturnal creatures during the “age of darkness” when “monstrous” reptiles were “dominating” gives the narrative moral and political undertones. In addition to implicitly justifying the “Age of Mammals”, this linear and hierarchical history of life limits understanding of the diversity and richness of life.
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Mickey Mortimer
Oct 19, 2024, 5:12:51 AMOct 19
to Dinosaur Mailing Group
"...
by terming the ancient relatives of mammals as proto-mammals but dinosaurs as reptiles (not “proto-reptiles”)
...
"
Er... unlike the relation between non-mammalian synapsids and living mammals, dinosaurs don't include the ancestors of any living classic reptiles, so why would they ever be called proto-reptiles? Proto-reptiles are non-reptilian sauropsids.
Mickey Mortimer
Er... unlike the relation between non-mammalian synapsids and living mammals, dinosaurs don't include the ancestors of any living classic reptiles, so why would they ever be called proto-reptiles? Proto-reptiles are non-reptilian sauropsids.
Mickey Mortimer
Thomas Richard Holtz
Oct 19, 2024, 8:51:03 AMOct 19
to DinosaurMa...@googlegroups.com
That whole paper seems written by someone whose only familiarity with paleontological issues is from reading general biology textbooks. Which is, in fact, the focus of the paper, and likely the cause of some of the clumsier thoughts (such as the one you posted).
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Thomas R. Holtz, Jr.
Email: tho...@umd.edu Phone: 301-405-4084
Principal Lecturer, Vertebrate Paleontology
Office: CHEM 1225B, 8051 Regents Dr., College Park MD 20742
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http://www.geol.umd.edu/~tholtz/
Phone: 301-405-6965
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http://www.geol.umd.edu/sgc
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Thomas R. Holtz, Jr.
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