Earliest known skeleton of a Bat discovered

[rogue06]

The exceptionally well-preserved, articulated fossilized remains of what is being called the earliest known bat skeletons found so far, dating from around 52.5 mya. Fossilized teeth from a couple million years earlier have been found in Asia but these are definitely the oldest skeletonized remains, which include the skull and mandibles.

The bat was named Icaronycteris gunnelli, in honor of the late Duke University paleontologist Gregg Gunnell, and was found in a limestone quarry that is part of the Green River Formation (Eocene) Southwestern Wyoming. It is the smallest of the known Icaronycteris line, weighing between 22.5 and 28.9 gms. (0.8-1oz.), which has been described as approximately half the weight of a tennis ball. It's wingspan roughly averages about 7% smaller than its closest relative.

And speaking of which, at this time there was an ongoing analysis of the remains of this other, closely related, ancestral bat, Icaronycteris index, which were plentiful enough that researchers suspected that it might possibly consist of at least two separate species. With the data from the new discovery, they realized that at least one bat (the remains of which appear to be well preserved as well), found in the same quarry in 1884, and currently in Canada's Royal Ontario Museum, was also an Icaronycteris gunnelli.

The primary distinction between Icaronycteris gunnelli and index appears to be structural differences in the wing claws and phalanxes and that the former possessed shorter robuster hind limbs.

Source: Oldest bat skeletons ever found described from Wyoming fossils

Scientists have described a new species of bat based on the oldest bat skeletons ever recovered. The study on the extinct bat, which lived in Wyoming about 52 million years ago, supports the idea that bats diversified rapidly on multiple continents during this time. Led by researchers at the American Museum of Natural History and Naturalis Biodiversity Center in the Netherlands, the study is published today in the journal PLOS ONE.

There are more than 1,460 living species of bats found in nearly every part of the world, with the exception of the polar regions and a few remote islands. In the Green River Formation of Wyoming—a remarkable fossil deposit from the early Eocene—scientists have uncovered over 30 bat fossils in the last 60 years, but until now they were all thought represent the same two species.

"Eocene bats have been known from the Green River Formation since the 1960s. But interestingly, most specimens that have come out of that formation were identified as representing a single species, Icaronycteris index, up until about 20 years ago, when a second bat species belonging to another genus was discovered," said study co-author Nancy Simmons, curator-in-charge of the Museum's Department of Mammalogy, who helped describe that second species in 2008. "I always suspected that there must be even more species there."

In recent years, scientists from the Naturalis Biodiversity Center started looking closely at Icaronycteris index by collecting measurements and other data from museum specimens.

"Paleontologists have collected so many bats that have been identified as Icaronycteris index, and we wondered if there were actually multiple species among these specimens," said Tim Rietbergen, an evolutionary biologist at Naturalis. "Then we learned about a new skeleton that diverted our attention."

The exceptionally well-preserved skeleton was collected by a private collector in 2017 and purchased by the Museum. When researchers compared the fossil to Rietbergen's expansive dataset, it clearly stood out as a new species. A second fossil skeleton discovered in the same quarry in 1994 and in the collections of the Royal Ontario Museum was also identified as this new species. The researchers gave these fossils the species name Icaronycteris gunnelli in honor of Gregg Gunnell, a Duke University paleontologist who died in 2017 and made extensive contributions to the understanding of fossil bats and evolution.

Although there are fossil bat teeth from Asia that are slightly older, the two I. gunnelli fossils represent the oldest bat skeletons ever found.

"The Fossil Lake deposits of the Green River Formation are simply amazing because the conditions that created the paper-thin limestone layers also preserved nearly everything that settled to the lake's bottom," said Arvid Aase, park manager and curator at the Fossil Butte National Monument, in Wyoming. "One of these bat specimens was found lower in the section than all other bats, making this species older than any of the other bat species recovered from this deposit."

While the I. gunnelli skeletons are the oldest bat fossils from this site, they are not the most primitive, supporting the idea that Green River bats evolved separately from other Eocene bats around the world.

"This is a step forward in understanding what happened in terms of evolution and diversity back in the early days of bats," Simmons said.


Source

© Copyright Original Source

The full paper, The oldest known bat skeletons and their implications for Eocene chiropteran diversification can be accessed and read by clicking the hyperlink and I made the abstract available below

Abstract

The Fossil Lake deposits of the Green River Formation of Wyoming, a remarkable early Eocene Lagerstätte (51.98 ±0.35 Ma), have produced nearly 30 bat fossils over the last 50 years. However, diversity has thus far been limited to only two bat species. Here, we describe a new species of Icaronycteris based on two articulated skeletons discovered in the American Fossil Quarry northwest of Kemmerer, Wyoming. The relative stratigraphic position of these fossils indicates that they are the oldest bat skeletons recovered to date anywhere in the world. Phylogenetic analysis of Eocene fossil bats and living taxa places the new species within the family Icaronycteridae as sister to Icaronycteris index, and additionally indicates that the two Green River archaic bat families (Icaronycteridae and Onychonycteridae) form a clade distinct from known Old World lineages of archaic bats. Our analyses found no evidence that Icaronycteris? menui (France) nor I. sigei (India) belong to this clade; accordingly, we therefore remove them from Icaronycteridae. Taken in sum, our results indicate that Green River bats represent a separate chiropteran radiation of basal bats, and provide additional support for the hypothesis of a rapid radiation of bats on multiple continents during the early Eocene.

Can't forget the images

holotype.jpg
The holotype



936ce02f-897e-4949-86cf-d74ed92bc907.jpg
The paratype (found earlier)

[rogue06]

An excellent article by the British Natural History Museum discussing many different aspects of the discovery: Oldest bat skeletons ever found described as new species

[shunyadragon]

Apparently the most important factor in this discovery is that it demonstrated the evolutionary diversity of bats at the time. Before this only one species was found in this area. This bat is more distantly related.

[rogue06]

Apparently the most important factor in this discovery is that it demonstrated the evolutionary diversity of bats at the time. Before this only one species was found in this area. This bat is more distantly related.

It's considered a sister taxon of the one that was known so they're fairly closely related.

[rogue06]

Apparently this bat was already capable of echolocation which probably shouldn't be a surprise since it appears that the ability to echolocate is very old and a lot of mammals have the ability to some degree. Even humans:

Another intriguing possibility is humans – many blind people can find their way around simply by listening to echoes bouncing off surrounding objects, and some expert human echolocators make short high clicks similar to those found in nature

.

[Sparko]

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