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[theropod]

Because many weapons are derived from the jaws, which in turn are derived from gill-arches, which in turn are derived from the gut…and since the head (i.e. the anterior end of the animal) is where these structures are located, there’s really no alternative to having these weapons (that are inherently tied to the digestive tract) in the head-region of the animal. All a head really is is a concentration of feeding and sensory structures near the front of the animal, and most weapons are feeding structures, so there’s a sort of circularity here. If the animal had its mouth and feeding apparatus anywhere except its head, would it even still be a head?

As for other cranial structures, such as horns, it’s quite likely they evolved there (as opposed to the lower back or the abdomen) simply because being located at the anterior end of the animal on the end of a reasonably muscular and mobile neck is an advantage for using them, while having them in most other places is not. You tend to see weapons located in anatomical regions that facilitate them actually being used, that’s why they are concentrated on the head (teeth, beaks, horns) the limbs (claws, hooves) and the tail (tail spikes, clubs and whips).

Regarding snakes, you can usually also hold them by the end of their tail quite safely (tried and tested that myself…but only with nonvenomous species), as long as the snake isn’t too long and you have sufficient reach to keep it away from your body.


BTW should we perhaps move this to this other thread we have for precisely this purpose→? Since we’ve sort of given up on the "answer a question–ask a question" concept here for the time being.

[Exalt]

Okay, sorry, I wasn't aware, and by nature, I have more questions than answers

[theropod]

No problem, my comment was actually more directed at someone with the moderation powers for this section, maybe they could just move our posts there?

[Exalt]

What are the benefits of uneven limb length in quadrupeds?

[Infinity Blade]

One example I can think of is hyenas, where the forequarters are larger than the hindquarters and they have somewhat of a sloped back. For hyenas, this bestows upon them the ability to carry large pieces of carcasses.

Another example would be quadrupedal ornithischians, where the hindlimbs are longer than the front limbs. However, I don't think this matters as much as people think, as there's evidence that the shoulder blades of these dinosaurs could swing back and forth (meaning they effectively extend forelimb length).

[Exalt]

Can you explain that first one, and would it likely apply to other predators with that trait?

[Exalt]

Two more:

1. Why did photosynthesizing plants survive the KPG event? One of the few consistency besides the gulf coast area being annihilated seems to be that for a years, nothing saw the sun.

2. Why have so few mammals employed venom or poison? There's the platypus and a couple of therapsids, but that's all that I know of.

[Infinity Blade]

Just as some animals were hardy and resilient enough to survive the event, so were some plants. In fact, the K-Pg wasn't even a major mass extinction event for flowering plants, which likely had a number of adaptations to help them get through relatively smoothly (Thompson & Ramírez-Barahona, 2023).

Our results support the resilience of major angiosperm lineages to the K-Pg extinction event, contrasting with phylogenetic evidence for other lineages such as non-avian dinosaurs, conifers [29] and fishes [34], all of which appear to have been impacted by the K-Pg event at higher taxonomic levels. The resilience of major angiosperm lineages to the K-Pg event is likely associated with the acquisition of eco-morphological innovations (e.g. CAM photosynthesis, wind and insect pollination, animal dispersal) and ecological opportunity following the K-Pg [41–45]. We suggest that the wide range of ecological niches occupied by angiosperms since the Late Cretaceous [14,28] likely promoted lineage diversification before the K-Pg and favoured their eventual survival when confronted with major environmental changes triggered by the K-Pg.

Also keep in mind that seeds can remain dormant for some time.

As for toxic mammals, they might have not only been more common in the past, but believe it or not it's even been proposed that venom is an ancestral trait to mammals, as many non-therian mammals have an extratarsal spur (similar to the one the platypus has) that may have been used to deliver venom against predators (Hurum et al., 2006). The reason why it's so uncommon now, however, is because therian mammals constitute the overwhelming majority of mammal species today, but therians secondarily lost this feature (i.e. after earlier mammals evolved the extratarsal spur when their earlier ancestors lacked it, therians then lost it, so that their lineage lacks it again).

[Infinity Blade]

Sept 17, 2023 16:50:01 GMT 5 Exalt said:

Can you explain that first one, and would it likely apply to other predators with that trait?

Keep in mind that hyenas also have some muscular adaptations to help them carry heavy carcass pieces, but even intuitively it makes some sense to have longer forelimbs than hindlimbs for this task. This way, the entire forequarters are elevated somewhat, thereby raising the carcass piece in the mouth by extension. Could you imagine having the front end of your body sloping downwards, and then having to carry some heavy thing over reasonably long distances in your mouth?

[Exalt]

Thanks.

This next question might sound utterly ridiculous depending on what the answer is, but are deer capable of walking forward while looking sideways?

And if you're wondering, this is about male Megaloceros.

[Infinity Blade]

Deer have monocular vision by nature, so they're technically always seeing something from the side no matter where their head is turned. So in that sense, the answer's yes. If you're simply talking about their head being turned to the side, the answer's still yes. Not only is there some field of binocular overlap that lets them see things right in front of their face (even if it's not nearly as much as what a human can see), but the laterally placed eyes still allow it to see what's on the sides.

[Exalt]

So in theory, a male Megaloceros could avoid avoid the clearance problem by shifting it's head?

[Exalt]

How do they estimate the weight of large animals that we can't weigh ourselves? Whales are so big that I don't know if there is a scale large enough, and even if there were, doing so would be a danger to both the whale, and possibly the people doing the weighing. Another example would be sauropods, whose larger members vastly outsized anything else that lived on land, and are, of course, lacking in soft tissue.

[Exalt]

www.theatlantic.com/science/archive/2016/09/humans-are-unusually-violent-mammals-but-averagely-violent-primates/501935/

Why are Carnivorans and Euarchontaglires so murderous? Is it just symptomatic of being social creatures that don't have hive minds?

[theropod]

Sept 18, 2023 22:34:52 GMT 5 Exalt said:

How do they estimate the weight of large animals that we can't weigh ourselves? Whales are so big that I don't know if there is a scale large enough, and even if there were, doing so would be a danger to both the whale, and possibly the people doing the weighing.

Indeed there isn’t really a way to get a giant whale out of the water in order to weigh it, without seriously endangering it and oneself in the process. Which is precisely why people do not do it. Probably the largest cetaceans to be weighed as living animals will be orcas, either while being caught and hauled out of the water to put them in their tanks, or later in captivity when trained to beach themselves onto scales for weighing, but I don’t know for sure what the record holder is. Those of course are quite small by cetacean standards (anything bigger than that isn’t generally able to get out of the water while alive).

Pretty much all the weight measurements that we have for larger whales were taken from dead specimens, either beached or, more commonly, killed by whalers. In some rare cases, these were weighed in one piece, but afaik the heaviest animal ever weighed in this manner was a sperm whale weighing 53 tons. Everything beyond that, all the way up to 200 ton blue whales is weighed piecemeal, after the whale has been cut up. This is still a fairly accurate measurement, but it is important to adjust the result for a certain percentage (usually assumed to be 5-10%) of mass being lost to fluids leaking out when the whale is cut apart.

It’s also quite common for large whales to not have been directly weighed at all, but for the weight to later be back-calculated from the number of barrels of whale oil produced from it. Many of the largest known whales in fact had their weight estimated in this manner.

As for determining the weight of a whale while alive, pretty much the only reliable method for this is a volumetric estimate, using techniques similar to what we tend to use for extinct animals. A good example of this would be Glarou et al. 2023, who used photos to estimate the volume (and mass) of sperm whales based on a variation of a graphic double integration (see below).

Another example would be sauropods, whose larger members vastly outsized anything else that lived on land, and are, of course, lacking in soft tissue.

There are multiple options here, you can mainly break them down into two categories:
Allometric methods use a regression equation that is based on the statistical correlation between body mass and some other measurement that may be more readily available, and for which there are sufficiently large datasets of measurements available. For terrestrial animals, the most commonly used metric is the circumference of the limb bones (esp. humerus and femur), since weight is functionally linked to the thickness of the bones used to support it (see Campione and Evans 2012, Campione et al. 2014 for the most recent and widely used explanations of these methods). For aquatic animals, which don’t have weight-bearing limb bones, it is quite common to use regressions estimating body mass from body length.
These are the most common variations of this concept, but really, an allometric weight estimation method can use any number of different measurements a predictor (for example there are some for mammals that use the dimensions of individual molars), which doesn’t mean they are all equally good at predicting body mass. Also generally, especially if the data are from a sample of various different animals with varying levels of phylogenetic relatedness to the taxon you want to estimate, the error margins of these techniques tend to be very large.

Volumetric methods, by contrast, attempt to use all the morphological information available for a specimen in order to estimate the body volume using some kind of 3D model. These models can be actual, physical sculptures (submerged in water or sand to estimate volume), they can be digital models in a software like Blender, or they can be purely mathematical constructions without any actual, visual model being present anywhere. One of the most widespread of these techniques is called "graphic double integration", and for it you basically take two views of each body part you want to estimate, subdivide them into a number of segments whose diameters you measure in both views, and then calculate their volume as a series of elliptical cylinders with their respective diameters being the ones you measured on the multiview reconstruction. Wedel (2011) gave a very good introduction to this method (and I also gave a brief tutorial on the "Basics"-thread on this forum).
Of course it goes without saying that this is more reliable if the animal in question is a reasonably complete specimen; there is little point making a volumetric estimate from a single toebone or tooth (although you might scale up or down the body mass based on some other, more complete relative that is in turn estimated using a volumetric method), but it makes a lot of sense if you have a complete skeleton, or even a completely preserved animal, that allows you to make a highly reliable reconstruction specifically taking into account that animal’s morphology.

Campione and Evans 2020 gave a solid review of both volumetric and allometric mass estimation techniques in case you’re interested.


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Wedel, M. 2011. Tutorial 11: Graphic Double Integration, or, Weighing dinosaurs on the cheap. URL: svpow.com/2011/01/20/tutorial-11-graphic-double-integration-or-weighing-dinosaurs-on-the-cheap/
Campione, N.E. and Evans, D.C. 2012. A universal scaling relationship between body mass and proximal limb bone dimensions in quadrupedal terrestrial tetrapods. BMC biology 10 (1): 1–22.
Campione, N.E. and Evans, D.C. 2020. The accuracy and precision of body mass estimation in non-avian dinosaurs. Biological Reviews 95 (6): 1759–1797.
Campione, N.E., Evans, D.C., Brown, C.M. and Carrano, M.T. 2014. Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions. Methods in Ecology and Evolution 5 (9): 913–923.
Glarou, M., Gero, S., Frantzis, A., Brotons, J.M., Vivier, F., Alexiadou, P., Cerdà, M., Pirotta, E. and Christiansen, F. 2023. Estimating body mass of sperm whales from aerial photographs. Marine Mammal Science 39 (1): 251–273.