TIL thread

[Supercommunist]

Was skimming through wikipedia articles and apparenty tegus and maybe all non-avian reptiles and amphibians have stronger limb bones than similar sized mammals/birds.

Here's the actual study I managed to track down.

Skeletal elements are usually able to withstand several times their usual load before they yield, and this ratio is known as the bone's safety factor. Limited studies on amphibians and non-avian reptiles have shown that they have much higher limb bone safety factors than birds and mammals.

jeb.biologists.org/content/214/15/2616

[Infinity Blade]

TIL there are fur impressions from Diprotodon.

The remains of diprotodons have been found throughout most of Australia. Entire skeletons are known, while at Lake Callabonna in South Australia, trackways (showing the form of the foot pads), remains of the foot pads themselves and the impressions of the fur of the legs have been preserved. Unfortunately, the fur impressions are poorly preserved, but they do indicate that diprotodons were fur-covered, not naked like rhinos and elephants.

Flannery (2002)->

[Infinity Blade]

TIL that Bryde's in Bryde's whale isn't pronounced like "brides". It's pronounced like "BROO-dus" (Scandinavian pronunciation and all).

[Infinity Blade]

This doesn't entirely count, given that I already had some idea about this, but long bones that have to withstand bending and torsional stress have more circular cross sections and thinner bone walls.

Another shape parameter is bone wall thinness. For a given bone tissue area, a section can have thick walls and a small diameter, or thin walls and a large diameter. Torsional resistance is favored in the second case (Alexander, 1968; Swartz et al., 1992) because material is placed at a greater distance from the axis of torsion, thus increasing J [polar moment of area]. The same is true for bending: I [second moment of area] is equally increased by thinner walls (Alexander, 1968). However, as before, pure compressive or tensile resistance is not influenced by wall thinness. Hence, when compared to bones habitually subjected to mixed bending/axial loading, torsion‐resisting bones should theoretically have relatively thinner walls.

Note that these rules hold within certain limits only, because elastic instability (e.g., buckling) occurs with very elongated or very thin‐walled cross‐sectional shapes (Alexander, 1968; Currey, 2002).

(Brackets mine)

Torsion‐resisting features were mainly concentrated in humeri, ulnae, and femora (Figs. 5 and 6). These bones generally comprised mainly laminar tissue, had thinner and more circular cortices, containing more oblique‐to‐transverse collagen fibers.

From Margerie et al. (2004)->

It is well known that the shape of a bone is a significant factor in mediating its strength and stiffness (e.g. Currey 2002), and there is ample evidence that the shapes of many bird bones are associated with optimizing these qualities. For example, the round and thin-walled humeral shafts of birds are an optimal shape for resisting both torsion and bending (Alexander 1983), and fused skeletal elements have been interpreted as increasing force resistance (i.e. stiffness; Buhler 1992). In contrast to the many studies of bone shape in birds, the impact of the material properties of bone tissue on bone strength and stiffness has received little attention. Bone density reflects mineral content and is positively correlated with bone stiffness (Young's modulus, E, the ability to resist deformation) and strength (yield stress, the ability to resist fracture; Currey 2002). It is also negatively correlated with toughness (ductility). Importantly, stiffness and strength scale with positive allometry so that even a small bone can be strong and stiff if it is composed of dense bone tissue.

Dumont (2010)-> (see Fig. 2 for a conceptual diagram)

I wonder if that's why even large theropods had leg bones that weren't necessarily thicker-walled than those of smaller taxa (link->). Given the fact that theropod leg bones are not oriented vertically (like a true graviport's) and accordingly probably dealt with significant amounts of bending and torsional loads during locomotion, having thicker walls with more of the bone tissue closer to the centroid axis would actually have reduced bending and torsional strength.

EDIT 11/13/2021: I found this. It applies to modern birds too.

When compared to mammals, the mass of compact (cortical) bone in birds is distributed relatively far from the long axis, leading to higher second and polar moments of area and greater inferred resistance to bending and twisting...

royalsocietypublishing.org/doi/10.1098/rsos.172067

[Infinity Blade]

TIL that there was an English nun by the name of Joan of Leeds who, in 1318, became tired of living in a monastery and attempted to escape by faking her own death (to live a life of "carnal lust"). She faked illness, created a dummy of her body (with some accomplices), and tricked her fellow nuns into burying that. Joan used this time to escape the monastery, but she was eventually discovered 48 km away living "indecently" with a man. This became a scandal, and the then-Archbishop ordered her to return to the monastery. Whether or not she actually complied with those orders is unknown.

en.wikipedia.org/wiki/Joan_of_Leeds

[elosha11]

^Medieval drama... SMH.

Out of a malicious mind simulating a bodily illness, she pretended to be dead, not dreading for the health of her soul, and with the help of numerous of her accomplices, evildoers, with malice aforethought, crafted a dummy in the likeness of her body... [she had] no shame in procuring its burial in a sacred space...She perverted her path of life arrogantly to the way of carnal lust and away from poverty and obedience. Having broken her vows and discarded the religious habit, she now wanders at large to the notorious peril to her soul and to the scandal of all of her order"

[Infinity Blade]

TIL Mauritius actually had a native predator. It was an owl that reached lengths of ~60 cm. It was the largest carnivore on the island before human settlement, and apparently wasn't affected much by introduced predators.

en.m.wikipedia.org/wiki/Mauritius_owl

[Infinity Blade]

TIL that after Gideon Mantell died, his rival Sir Richard Owen had a section of his spine removed, pickled, and displayed in his museum the Royal College of Surgeons.

This is a sketch of that spine section (Mantell suffered from scoliosis).


Image is in public domain.

[Infinity Blade]

I learned this the other day, but I've only seen pictures today. Black rhinos can sometimes develop three horns.

[theropod]

TIL the concept of the 2000 Watt society.

en.wikipedia.org/wiki/2000-watt_society

Honestly it should not be as unthinkable as many people make it out to be to go back to the amount of energy use we had in the 60s (and most of the world doesn’t reach even to this day), especially considering we’d get much more out of it with more energy-efficient technologies. Yet people will inevitably portray such proposals as "going back to the stone age"

[Infinity Blade]

TIL that in 1999, some paleontologists held a memorial service for the mammoths in Mammoth Springs. One of them (Connie Barlow) actually made a Pleistocene rewilding concluding hymn in the tune of the Beatles' "Let It Be".

thegreatstory.org/mammoth-site.html

[Infinity Blade]

TIL that a while back, someone captioned this image of a Pompeii victim plaster cast as a masturbating man, and it spread around. In reality, the heat of the pyroclastic surge flexed his muscles and bent his arms, so no, no masturbating man.


Image source->

[Ceratodromeus]

what a let down

[Infinity Blade]

So, I had heard a while back that the gorgonopsids actually seem to have gone extinct a bit before the P-T extinction event (Inostrancevia is from the Wuchiapingian age), the age just before the one that ended with the P-T event.

But TIL that they were replaced by therocephalians like Moschorhinus (or also Megawhaitsia).

A description of Moschorhinus.

Moschorhinus skull dimensions range from those of a large monitor lizard to those of a lion. It is a most unusual therocephalian and shows a large temporal fenestra, convex palate, and laterally compressed incisors set in a shallowly curving arcade, in addition to the short, strong snout (Fig. 5.2). The lower jaw has remarkable canines and a symphysis that is expanded more than in any other therocephalian (Jenkins, 2001b). The canines are as long as the sabers of all except the most derived gorgonopsids (Fig. 5.1), but are round in cross-section, resembling the spikes used to secure some railway cross-ties. There is no modern analog for these teeth, the closest perhaps being the hyperelongate canines of the Clouded Leopard (Neofelis nebulosa) (Fig. 8.2). The combination of long, robust canines and flattened incisors in a shallow arcade suggests a felid-like mode of attack (sensu Biknevicius et al., 1996), in which the strong canines would have sustained a long period embedded in prey (Jenkins, 2001b). This is the earliest known instance of this design. Moschorhinus went extinct after gorgonopsids and was a therocephalian occupying a gorgonopsid-like ecological niche (Jenkins, 2001b). The powerful symphysis, robust snout, and extraordinary canines show Moschorhinus to have been a truly formidable predator; why it should have survived when equally powerful and similarly designed gorgonopsids went extinct is probably due to some as-yet-unknown feature of its physiology. Once Moschorhinus had disappeared, the roles of top predators were taken up by cynodonts (Fig. 3).

web.archive.org/web/20131017062835/http://www.yale.edu/ypmip/predation/Chapter_10.pdf

EDIT: More information. Therocephalians shared this top predator position with archosauriforms like Archosaurus.

The most important feature was the disappearance of the pareiasaur–gorgonopian coadaptive pair, which were the dominant large herbivore and carnivore, and the appearance of new top predators (ultimate consumers), the proterosuchids (Fig. 7). The Vyazniki community documents the beginning of the major faunal replacement at the Permian–Triassic boundary and during the Triassic, that is, the replacement of therapsids by archosaurs. In its food chain structure, the Vyazniki terrestrial community (Fig. 5) was the first thecodont–dicynodont one. In this respect, the Vyazniki terrestrial community is more similar to Triassic communities. The anthracosaur Bystrowiana is the first record of bystrowianids, relict chroniosuchians typical of the Triassic. Dvinosaurs, kotlassiomorphs, chroniosuchids, elginiids, therocephalians, and dicynodontids are typical Upper Permian elements of the Vyazniki Assemblage (Golubev, 2000).

www.researchgate.net/profile/Valeriy-Golubev/publication/226590807_Vyazniki_biotic_assemblage_of_the_terminal_Permian/links/0046353121c851aad6000000/Vyazniki-biotic-assemblage-of-the-terminal-Permian.pdf

[creature386]

(Might be more something for the thread on laughable statements, but it fits here, too,)

TIL about the hypothesis of "initial bipedalism". Apparently, some people believe that the way humans walk has been the primordial condition in vertebrates.

Anyway, while the AAH might be well known, have you heard about its most radical variation: the theory of initial bipedalism? According to this little known school of thought, not only do humans owe their anatomy to a direct aquatic ancestry, so do ALL mammals and all other tetrapods. In fact, all vertebrates evolved from aquatic bipedal human-like ancestors like the marine homonculus shown here

web.archive.org/web/20121109160611/http://scienceblogs.com/tetrapodzoology/2008/03/17/initial-bipedalism/
It gets even better. Apparently, fishes descend from human-like creatures:

At the root of the initial bipedalism theory we have Westenhöfer’s argument that, while mammals had their roots in amphibious quadrupeds, humans are the most structurally primitive of all the primates, that apes are descended from human-like forms, and that the unusual features of the human body evolved for life in water (e.g. Westenhöfer 1935). De Sarre (1992, 1997) has reported that he first began to consider the broader question of tetrapod origins after deciding that fishes might not be the aquatic ancestors of tetrapods, but rather that said fishes may just as well be the aquatic descendants of terrestrial tetrapods. So in its extreme, current incarnation, it seems that, to be an ‘initial bipedalist’, you have to reject the idea that humans and other tetrapods descended from fish, and accept the idea that fish are the secondarily aquatic descendants of amphibian-grade tetrapods.