It's enough to drive you batty

[rogue06]

Bats have been and remain one of evolution's longest standing puzzles. Prior to the 21st cent. there were few if any fossilized remains to study since they tended to live in forests and jungles -- areas not known for being conducive for fossilization of small creatures.

All of that changed with the discovery of primitive bats such as Onychonycteris finneryi and others, which disclosed numerous transitional features.

For the first time various early extinct species could be compared to their modern ancestors which revealed that the first bats weren't able to echolocate. Instead, like nearly all other terrestrial mammals, they relied on sight, smell and touch to locate food. And while modern bats have a claw only on the equivalent of our thumb, the earlier bats kept some of the additional finger claws inherited from their ancestors (the aforementioned Onychonycteris had a claw at the end of each digit).

And yet, in spite of these major strides, the fact remains that the various specimens that have been unearthed are already easily recognizable as bats. We still haven't discovered exactly how they progressed from terrestrial creatures to airborne ones.

Now it isn't the first time that scientists have been to this rodeo. Until very recently the same problem existed concerning whales, but thanks to several discoveries in places like Egypt and Pakistan, we now have an excellent picture of how a specific group of hoofed land mammals became the largest creatures in the ocean. Similar discoveries provided answers to the origin of other creatures that we had been in the dark about, such as snakes, flatfish, turtles and even birds.

Of course, there are unique problems regarding bats. Aside from largely living in areas notorious for not allowing for much fossilization, unlike say the bones of a whale or their ancestors, the bones from bats can be incredibly fine and delicate. For instance, some of the bones of Icaronycteris index, a neighbor and likely contemporary of Onychonycteris, are as thin as a human hair.

Recently, researchers uncovered two tiny teeth, upper molars, in the Junggar Basin at the far northwest extremity of China that represent the oldest-known fragmentary bat fossils from Asia dating before nearly all the other bat remains so far uncovered. And while that is far from a complete skeleton that could answer so many questions, these two tiny teeth are nevertheless important discoveries.

First, they confirm that these early bats, possibly "proto-bats" were in Asia at this point lending some credence to the idea that they may have originated there. In any case this find should ignite an increase into research looking for early bats.

Second, as the lead author of the study, Matthew Jones of the University of Kansas' Biodiversity Institute and Department of Ecology & Evolutionary Biology, observed:

These teeth look intermediate, in between what we would expect a bat ancestor to look like -- and in fact, what a lot of early Cenozoic insectivorous mammals to do look like -- and what true bat looks like. So, they have some features that are characteristic of bats that we can point to and say, 'These are bats.' But then they have some features that we can call for simplicity's sake 'primitive.'"

FWIU, some of the teeth retained cusps found in a number of early therian mammals but are entirely missing or "atrophied" in bats.

---

Source: Researchers detail the most ancient bat fossil ever discovered in Asia

A new paper appearing in Biology Letters describes the oldest-known fragmentary bat fossils from Asia, pushing back the evolutionary record for bats on that continent to the dawn of the Eocene and boosting the possibility that the bat family's "mysterious" origins someday might be traced to Asia.

A team based at the University of Kansas and China performed the fieldwork in the Junggar Basin -- a very remote sedimentary basin in northwest China -- to discover two fossil teeth belonging to two separate specimens of the bat, dubbed Altaynycteris aurora.

The new fossil specimens help scientists better understand bat evolution and geographic distribution and better grasp how mammals developed in general.

"Bats show up in the fossil record out of the blue about 55-ish million years ago -- and they're already scattered on different parts of the globe," said lead author Matthew Jones, a doctoral student at the KU Biodiversity Institute and Department of Ecology & Evolutionary Biology. "Before this, the earliest bats are known from a couple of places in Europe -- Portugal and southern France -- and Australia. So, when they show up early in the fossil record as these fragmentary fossils they're already effectively worldwide. By the time we get their earliest known full skeletons, they look modern -- they can fly, and most of them are able to echolocate. But we don't really know anything about this transitional period from non-bats to bats. We don't even really know what their closest living relatives are among mammals. It's a really big evolutionary mystery where bats came from and how they evolved and became so specialized."

Jones' co-authors were K. Christopher Beard, senior curator at the KU Biodiversity Institute and Foundation Distinguished Professor of Ecology & Evolutionary Biology at KU; and Qiang Li and Xijun Ni of the Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and the Center for Excellence in Life and Paleoenvironment at the Chinese Academy of Sciences.

The ancient bat teeth were discovered through painstaking fieldwork in the Junggar Basin, where the KU researchers worked at an isolated field site established by their Chinese colleagues, one of two sites in the region the team hope will continue yielding interesting fossils.

"This was concerted effort over a long period of time by our Chinese colleagues," Jones said.

"They suspected that there were fossiliferous deposits from the Paleocene and Eocene, and they spent several years going out there, identifying where to find fossils. Chris was a part of several seasons of fieldwork there. I was a part of one season of fieldwork there. What we did was collect a bunch of sediment to screen wash, which is sort of like panning for gold. You pour a bunch of sediment into a sievelike apparatus and let all the dirt and everything fall out, and you're only left with particles of a certain size, but also fossils."

Beard said the fieldwork was an outgrowth of long-standing relationships between the KU team and its Chinese counterparts.

"We've been fortunate enough to be able to host our Chinese colleagues here in Lawrence for extended research visits, and they've more than reciprocated by hosting us for research and fieldwork in China. This work in the Junggar Basin is really trailblazing work because the fossil record in this part of China is only just barely beginning to emerge, and this area is very removed and isolated. It's just a giant empty place. There are some camels, some snakes and lizards, but you don't see many people there. That remoteness makes the logistics to do fieldwork there quite difficult and expensive because you've got to bring in all your food and water from far outside -- all of that hindered research in this area previously."

Following the challenging fieldwork, the residue left behind from the screen washing at the site was sorted at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

"In 2017, after we got back from the field, Xijun said. 'Hey, one of the technicians picking through this sediment thinks they found a bat,'" Jones said. "Knowing I was interested in bats, they showed it to me. The next year, the other tooth was found -- so there's two teeth."

Through meticulous morphological analysis of the teeth, along with biostratigraphy -- or analyzing the position of layers of fossil remains in the deposits -- the authors were able to date the specimens to the advent of the Eocene, the earliest period when bat fossils have been found anywhere on Earth. Indeed, the presence of these ancient bat fossils in Asia bolsters a theory that bats could have emerged from there in the first place, then distributed themselves worldwide when they later developed flight.

More fieldwork in the area is ongoing, and Jones and Beard said they were hopeful to find even older specimens, perhaps even dating to the Paleocene, the epoch before the Eocene, when researchers believe bats probably originated. Yet the particulars of Altaynycteris aurora remain hazy -- for instance, it's impossible to say from teeth fragments if the animal could fly or echolocate.

"These teeth look intermediate, in between what we would expect a bat ancestor to look like -- and in fact, what a lot of early Cenozoic insectivorous mammals to do look like -- and what true bat looks like," Jones said. "So, they have some features that are characteristic of bats that we can point to and say, 'These are bats.' But then they have some features that we can call for simplicity's sake 'primitive.'"

The researchers said the new fossils help fill in a gap to understanding the evolution of bats, which remains a puzzle to experts -- and could teach us more about mammals in general.

"I can think of two mammal groups that are alive today that are really weird," Beard said. "One of them is bats, because they fly -- and that's just ridiculous. The other one is whales, because they're completely adapted to life in the ocean, they can swim, obviously, and they do a little bit of sonar echolocation themselves. We know a lot about transitional fossils for whales. There are fossils from places like Pakistan that were quadrupedal mammals that looked vaguely doglike. We have a whole sequence of fossils linking these things that were clearly terrestrial animals walking around on land, through almost every kind of transitional phase you can imagine, to a modern whale. This isn't true for bats. For bats, literally you've got a normal mammal and then you've got bats -- and anytime you've got a fossil record that's a giant vacuum, we need work that can fill partly that. This paper is at least a step along that path."


Source

© Copyright Original Source

The entire paper, The earliest Asian bats (Mammalia: Chiroptera) address major gaps in bat evolution, is available online at the hyperlink provided, with the abstract from it posted below

Abstract

Bats dispersed widely after evolving the capacity for powered flight, and fossil bats are known from the early Eocene of most continents. Until now, however, bats have been conspicuously absent from the early Eocene of mainland Asia. Here, we report two teeth from the Junggar Basin of northern Xinjiang, China belonging to the first known early Eocene bats from Asia, representing arguably the most plesiomorphic bat molars currently recognized. These teeth combine certain bat synapomorphies with primitive traits found in other placental mammals, thereby potentially illuminating dental evolution among stem bats. The Junggar Basin teeth suggest that the dentition of the stem chiropteran family Onychonycteridae is surprisingly derived, although their postcranial anatomy is more primitive than that of any other Eocene bats. Additional comparisons with stem bat families Icaronycteridae and Archaeonycteridae fail to identify unambiguous synapomorphies for the latter taxa, raising the possibility that neither is monophyletic as currently recognized. The presence of highly plesiomorphic bats in the early Eocene of central Asia suggests that this region was an important locus for the earliest, transitional phases of bat evolution, as has been demonstrated for other placental mammal orders including Lagomorpha and Rodentia.

rsbl20210185f02.gif
Scale bar is 0.5 mm

[NorrinRadd]

I'm disappointed by the paucity of bats in my area compared to the way things were 30 years ago and earlier. I have not seen *any* so far this year. Back in the day, there were tons. If we played back-yard badminton past dusk, they'd chase the "birdies." We had a pool back then and they'd skim the surface of the water.

[Sparko]

Meanwhile in Wyoming they found a fossil Robin!

https://www.newsweek.com/wyoming-52-...robins-1321857

Biff! Bam!

[rogue06]

Meanwhile in Wyoming they found a fossil Robin!

https://www.newsweek.com/wyoming-52-...robins-1321857

Biff! Bam!

But did they find any coprolites from either? You know, fossilized doo-doo dododododododododo...musical note.gif

[rogue06]

I mentioned something about how the areas they lived (mostly forests and jungles) are not good terrains to try to get fossils from, especially of very small creatures, some of who's bones can be a hair's breadth wide. It should be remembered that fossilization itself is an incredibly rare occurrence when you think of a planet loaded with life for hundreds of millions of years.

To give y'all a better grasp on just how extraordinarily rare it is we can look at just the first stage and not even get into all of the geologic hurdles involved.

This is something I wrote several years back (pre-Crash)

[...]

Almost a century before going extinct in 1914 the passenger pigeon were thought to have comprised somewhere between 25 and 40% of the total number of birds in all of North America and traveled in flocks numbering as many as 2 Billion strong with only the Rocky Mountain Locust flying in larger groups. A large nesting in Wisconsin was reported as covering 850 square miles, with the number of birds nesting there being estimated at 136,000,000. One flock documented in Canada back in 1866, stretched for a mile wide and 300 miles long and took 14 hours to fly by. Other reports state that on some occasions flights often continued from morning until night and lasted for several days.

Yet for creatures that existed in such vast numbers such a short time ago (and being one of the most abundant birds in the world) I challenge you to go out in the wild and find one of their skeletons lying around.

Now, considering the scarcity already in passenger pigeon bones there will be even far fewer that ever get fossilized, and even fewer still that ever could be detected. If they had lived a 1000 years ago or even a bit over 500 years ago rather than a century or so ago there might not be anything left for us to find and know they ever even existed much less that they were around a third of all birds in North America at one time.

Another example is the American bison (or "buffalo") which once roamed over about a third of the entire continent of North America though they especially flourished in the Great Plains regions. In the early 19th century there were an estimated 20 to 30 million bison living here. While not driven into extinction like the passenger pigeon, and being much larger (ranging between 6½ to 11½' long and weighing between 700 and 2200 lbs.) finding any of their remains is exceedingly rare.

The point being fossilization is a rare process because most components of formerly-living things tend to decompose quite quickly after death and the conditions under which fossilization takes place are quite rare. Even the skeleton of an animal as immense as an elephant can be reduced to splinters in a relatively short amount of time as illustrated in The End of the Game by Peter Beard.^[1]

[...]





1. Go to HERE and click “to LOOK INSIDE” and scroll down to see two of a few of the astonishing photographs of this breakdown in action.

Amazon no longer offers the preview, but it depicts multiple photos looking down from a plane of an elephant that had just died. In very short order a creature of that size was picked clean and even it's enormous bonze splintered and breaking apart under the hooves and feet of numerous other animals. This is one of the images from the series that has apparently been made into a print and sold in galleries (he was a famous photographer)

0f191cdc30116a63b280e5063d9c6b4d.jpg