Synapsids Developed the Diaphragm for Breathing Very Early

A caseian point for the evolution of a diaphragm homologue among the earliest synapsids

Authors:

Lambertz et al

Abstract:

The origin of the diaphragm remains a poorly understood yet crucial step in the evolution of terrestrial vertebrates, as this unique structure serves as the main respiratory motor for mammals. Here, we analyze the paleobiology and the respiratory apparatus of one of the oldest lineages of mammal-like reptiles: the Caseidae. Combining quantitative bone histology and functional morphological and physiological modeling approaches, we deduce a scenario in which an auxiliary ventilatory structure was present in these early synapsids. Crucial to this hypothesis are indications that at least the phylogenetically advanced caseids might not have been primarily terrestrial but rather were bound to a predominantly aquatic life. Such a lifestyle would have resulted in severe constraints on their ventilatory system, which consequently would have had to cope with diving-related problems. Our modeling of breathing parameters revealed that these caseids were capable of only limited costal breathing and, if aquatic, must have employed some auxiliary ventilatory mechanism to quickly meet their oxygen demand upon surfacing. Given caseids’ phylogenetic position at the base of Synapsida and under this aquatic scenario, it would be most parsimonious to assume that a homologue of the mammalian diaphragm had already evolved about 50 Ma earlier than previously assumed.

pop sci write up.

A Juvenile Barosaurs (sauropod) From Jurassic Utah also had an Avian-like Airsac Respiratory System

A juvenile sauropod dinosaur from the Late Jurassic of Utah, U.S.A., presents further evidence of an avian style air-sac system

Authors:

Melstrom et al

Abstract:

Well-preserved, articulated juvenile sauropod dinosaur material is very rare, hindering attempts to understand ontogenetic changes within the clade. Here, we describe an exceptionally preserved partial skeleton of a Barosaurus from the Morrison Formation of Dinosaur National Monument, Utah, U.S.A., that is only about one-third adult size. This small size and the lack of fusion of neurocentral and costovertebral sutures indicate that the individual is a juvenile. Apomorphy-based taxonomic identification of the specimen combined with the excellent preservation of its vertebral column allows documentation of both serial and ontogenetic morphological changes in Barosaurus. Each vertebra underwent substantial morphological change in the relative height of the neural spine and location of the zygapophyseal and diapophyseal articular facets during ontogeny but not in the degree of bifurcation of the neural spines. Pneumaticity in the dorsal vertebrae varies serially: large pneumatic fossae punctuate the centra of dorsal vertebrae 1–4 and 8–9, whereas these spaces are occupied by shallow depressions in dorsal vertebrae 5–7. This represents the first known caudal dorsal pneumatic hiatus in a sauropod dinosaur, which suggests that separate air sacs pneumatized the anterior and posterior regions of the dorsal vertebral column, congruent with the pattern observed in non-avian and avian theropod dinosaurs and the presence of an avian-style lung in sauropods.

Sufficient Oxygen in Paleoatmosphere at the Calymmian/Ectasian MesoProterozoic Boundary for Animals to Breathe

Sufficient oxygen for animal respiration 1,400 million years ago

Authors:

Zhang et al

Abstract:

The Mesoproterozoic Eon [1,600–1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were less than 0.1% of present levels, sufficiently low to have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon−oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels greater than 4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.

pop sci write up here and here.

Now THAT'S Green Power: a Fuel Cell Using Cyanobacteria Respiration and Photosynthesis

Researchers from Concordia University in Montreal are looking to tap into what may be the most plentiful yet overlooked source of power in the world. The group has invented a power cell that harnesses the electricity created during the natural processes of photosynthesis and respiration in blue-green algae.

The microorganisms, also known as cyanobacteria, can be found in just about any ecosystem on the planet, across all latitudes, with respiration and photosynthesis taking place in the organism's cells both involving electron transfer chains.

"By taking advantage of a process that is constantly occurring all over the world, we've created a new and scalable technology that could lead to cheaper ways of generating carbon-free energy," says Concordia engineering professor Muthukumaran Packirisamy.

We've seen algae put to similar use in a building in Germany, and on a smaller scale in algae-powered lamps, but algae is probably better know for its potential to produce energy as a biodiesel feedstock.

The Concordia group's prototype photosynthetic power cell is currently small scale, with the algae being placed in an anode chamber, alongside the cathode and proton exchange membrane that make up the unit. An external load connected to the device extracts the electrons released by the algae to the electrode surface.

According to the paper, the team was able to measure open-circuit voltage as high as 993 millivolts, while a peak power of 175 microwatts was obtained under an external load of 850 ohms. The team claims its Micro Photosynthetic Power Cell (μPSC) could produce a power density of 36.23 microwatts/cm2, a voltage density of 80 millivolts/cm2, and a current density of 93.38 microamps/cm2 under test conditions.

link.

Pterosaur Breathing Like Birds, Crocodiles

Breathing in a box: Constraints on lung ventilation in giant pterosaurs

Authors:

Geist et al

Abstract:

Pterosaurs were the first vertebrates to achieve active flight, with some derived forms reaching enormous size. Accumulating fossil evidence confirms earlier indications that selection for large size in these flying forms resulted in a light, yet strong skeleton characterized by fusion of many bones of the trunk. However, this process also added mechanical constraints on the mobility of the thorax of large pterosaurs that likely limited the options available for lung ventilation. We present an alternative hypothesis to recent suggestions of an avian-like mechanism of costosternal pumping as the primary means of aspiration. An analysis of the joints among the vertebrae, ribs, sternum, and pectoral girdle of large pterosaurs indicates limited mobility of the ribcage and sternum. Comparisons with modes of lung ventilation in extant amniotes suggests that the stiffened thorax, coupled with mobile gastralia and prepubic bones, may be most consistent with an extracostal mechanism for lung ventilation in large pterodactyloids, perhaps similar to a crocodile-like visceral displacement system.

Monitors Breathe Like Birds: How Basal is Unidirectional Airflow in Diapsids???

Air flows mostly in a one-way loop through the lungs of monitor lizards – a breathing method shared by birds, alligators and presumably dinosaurs, according to a new University of Utah study.

The findings – published online Wednesday, Dec. 11 in the journal Nature – raise the possibility this breathing pattern originated 270 million years ago, about 20 million years earlier than previously believed and 100 million years before the first birds. Why remains a mystery.

"It appears to be much more common and ancient than anyone thought," says C.G. Farmer, the study's senior author and an associate professor of biology at the University of Utah. "It has been thought to be important for enabling birds to support strenuous activity, such as flight. We now know it's not unique to birds. It shows our previous notions about the function of these one-way patterns of airflow are inadequate. They are found in animals besides those with fast metabolisms."

But Farmer cautions that because lizard lungs have a different structure than bird and alligator lungs, it is also possible that one-way airflow evolved independently about 30 million years ago in the ancestors of monitor lizards and about 250 million years ago in the archosaurs, the group that gave rise to alligators, dinosaurs and birds. More lizard species, such as geckos and iguanas, must be studied to learn the answer, she says.

Farmer conducted the study with two University of Utah biologists – first author and postdoctoral fellow Emma Schachner and doctoral student Robert Cieri – and with James Butler, a Harvard University physiologist.

link.

Awesome pop write up by Matt Wedel.