Fossil Close to Branching of Dinos, Birds, and Crocs

[BillTre]

Based on leg and ankle structures, a fossil has been described that would seem to be close to the branching of Dinosaurs, Birds, and Crocodile-like creatures.
Here is a Science mag news story on it.

 

[Bystander]

The number of "discoveries" gathering dust in some drawer full of "miscellaneous fragments..."

 

[jim mcnamara]

@Bystander - Hmm. Do you have an idea about the admittedly fuzzy estimates on the number of species that have existed? The only way to make any sense of this enormous mountain of data is through cladistics. News reports turn those research papers into 'common ancestor of animal group X'. Otherwise, who in the non-Biologist population would ever read it and then rightfully stuff it into their version of a black hole storage system?

Got perspective (instead of milk...)?

For Animalia only, 8.7 million extant species as of 2011:
http://www.calacademy.org/explore-science/how-many-species-on-earth

Greater than 99% of all animal species that ever existed are extinct. So we are wading through a mountain of more than 1 billion species. Not trivial.
If you have a better way to deal with this potential mountain of taxonomic data, you can make a real, needed step in Biology. I sure do not. -Note: plants are worse, number-wise.

 

[BillTre]

@jim mcnamara, Couldn't agree more!

Cladistics is a great advance for determining the relationships between different species.

Numbers of species seem to be always changing though.
Going into the past with its lower quality data just makes it more confusing.

There is not a single well agreed upon species definition (many like the biological species definition but it has problems).

Determining how to tell when a single species evolves into a new species over time in a single non-bifurcating lineage is a real problem.

In recently read about a group that wants to sequence the genomes of all eukaryotes. That's a big undefined job, but would certainly be interesting. Kind of a Darwinian dream project.

 

[jim mcnamara]

@BillTre

sequence the genomes of all eukaryotes

Where did you see that? I don't think we even know all of the eukaryotes. But of course sequencing the human genome in the early 2000's was considered hard to do. I help people write programs to mess with pasta-format files (FASTA/PASTA not food pasta) that have sigificant DNA data in a few dozen files. So maybe we will be into sequencing the species du jour at some point soon.
https://wiki.gacrc.uga.edu/wiki/PASTA

 

[BillTre]

It took me a while to find it again but it is here, and I was wrong they don't want to sequence all eukaryotes, they want to sequence all life.
Of course those bacterial/archaeal genomes are relatively small, but more are being discovered all the time!
This does not seem very realistic to me, but time may change my opinion.

On the other hand, I was supplying different species of fish to a lab that would get them sequenced for pretty cheap and they could do comparisons between the complete sequences of several different fish species. A different lab gave them a particular species's genome sequence (something like 30x coverage) on a thumbdrive because they got the sequence a few years before but didn't have time to deal with it properly. Genome sequencing seems to be kind of cheap now.

This is where (I feel) building phylogenies is now going.
They could also show hybridization between different species which resulted in genes from one species ending up in another (Fig. 5 in above link).

 

[rootone]

The situation with viruses remains confusing.
Are they degenerate forms of higher life, or are they just more DNA/RNA doing what it does?

 

[jim mcnamara]

@rootone
Virus and prions - There is no good answer for when they 'happened'.
They form part of the problem of setting boundary definitions in the case of living and not-so-living things. Most biologists take them as non-living. Computer viruses are a good analogy - a virus that attacks some core element in windows XP does nothing with other versions - high host specificity. And.
Requires a functioning system to do its dirty work. Viruses that attack mammals have the same kinds of behaviors and specificity, for example.

https://en.wikipedia.org/wiki/Prion Also google for: spongiform encephalopathy (like mad cow disease or human CJD)

 

[Bystander]

@Bystander - Hmm. Do you have an idea about the admittedly fuzzy estimates on the number of species that have existed?

Back of the envelope calculation: https://www.physicsforums.com/threa...ixth-mass-extinction.12709/page-3#post-150112