9

Per the comments, the actual paper seems pretty like a pretty straightforward operation of normal science: Somebody noticed something that looked off about one of the bones and decided they'd look into it more carefully. They found that yes, that bone appears to have been an accidental inclusion, and in fact the rest of the skeleton makes more sense without ...


5

I've not read it but this SE question Why don't mammals have more than 4 limbs? though not a duplicate (it asks about mammals not all vertebrates) may have some elements in its answers pertinent to your question. And the question Why are there no vertebrates with more than four limbs? has been asked in Quora where it has 7 answers you may find useful. ...


3

There are several defining morphological characteristics of dinosaurs. Including their ankle structure and perforated acetabulum, Aka the hole in their hip goes all the way through, as well as a few other minor features. These combined makes it literally impossibly for a dinosaur to take on a sprawling pose without breaking hind leg in many places, this is ...


3

Looks like the proximal end of a rib of a large mammal (cow, horse, deer). Without information about how large it is, it is not possible to get closer to an identification. It's not a claw and very likely not a fossil. It just looks old and dirty. Here's a horse rib cage (from https://www.rodnikkel.com/content/saddle-tree-blog-from-shop-and-desk/the-rib-...


3

From Raup (1986). Up to 4 billion species of plants and animals are estimated to have lived at some tlme m the geologic past (2), most of these in the last 600 million years (Phanerozoic time). Yet there are only a few million species living today. Thus, extinction of species has been almost as common as origination. I am not sure how exactly has ...


2

late Maastrichtian is probably it. Part of the problem you are running into is the Triceratops genus is in flux, there is debate about whether certain species belong in the genus. Such as whether triceratops and torosaurus are the same species. The other problem you are running in to is the accuracy of dating methods, many fossils are dated indirectly, ...


2

Short answer Mammalian hearing is unique and amazing. The mammalian ear is unique and highly sensitive with a built in amplification system that means even minute changes in sound can be detected. The bony amplification is also the reason the mammalian (or at least therian) cochlea is huge, every incremental increase yielded markedly more information, it ...


1

There are reptiles that also use urea, and mammals that excrete uric acid. it is likely that urea is the ancestral condition (compared to uric acid) as it occurs in adult amphibians and some fish. But ammonia is even more ancestral than that, occurring in young amphibians and most fish. It is likely uric acid developed alongside terrestrial eggs, as every ...


1

According to the latest discovery, Nature (Published: 29 April 2020), Tail-propelled aquatic locomotion in a theropod dinosaur, Spinosaurus was probably aquatic or at least semi-aquatic. See also this video.


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