Bats: First fly, then echolocation

52.5 million year old fossil as proof of the flight first theory

Onychonycteris finneyi © Royal Ontario Museum, Toronto (Canada)
Read out

Did they first flee or did bats first detect echolocation and then fly into the air? There were different hypotheses among scientists - until now. For now, the oldest bat find has decided the dispute that has lasted for decades in favor of the so-called "flight-first theory".

As flying night hunters with echolocation, today's bats not only provide the template for mystery stories, they also occupy a special position among mammals. For a long time, the development of this extraordinary specialization in science has been controversial. It was the flight-first theory, the echolocation-first theory and the assumption that these, so typical for the animals skills, have developed simultaneously as competing hypotheses for debate.

The new findings presented in Nature by an international team of scientists in favor of the flight-first theory are based on the morphological analysis of 52.5 million year old finds from the Green River Formation in Wyoming (USA). Comparative studies on the 47-million-year-old bats from Senckenberg's German World Natural Heritage Site Pit Messel brought further light into the darkness of the historical past. From the two Eocene sites come the world's oldest, as complete skeletons of fossil surviving bats.

Extended pedigree of bats

The fossil recovered in Wyoming (USA) belongs to Onychonycteris finneyi. Because of the anatomical features of the species, which was first described in 2003, it lies between the comparison groups of previous finds, a new family with the genus Onychonycteris has been set up in the pedigree for these and another fossil bat also recovered in Wyoming.

X-ray of Hassianycteris (fossil bat from Senckenberg supervised world natural pit Messel). © Research Institute Senckenberg

While the species name finneyi honors Bonnie Finney, the discoverer of the first described representative of the new family, the genus name refers to the long pronounced claws that can be found on this find on ten fingers. An anatomical feature that can be found neither in the Messel bats, Archaeonycteris and Hassianycteris, nor in later developed or present specimens. In addition to onychonycteris, all known bats have only two to a maximum of four finger claws. Presumably, this early representative in the family tree of the bats was a skillful climber and - like his descendants - hung in the air. display

Claw Bat captured insects in flight

Onychonycteris finneyi is an important mosaic in the evolution of the bats. With short wings and surprisingly long hind legs, between their toes was a Flugmembran, the find, according to the scientists body proportions that neither in the today occurring vierf igen mammals, even in modern day or any of the previously known fossil bats. The wing skeleton as well as the shape of the ribcage and tail make the researchers conclusively conclude that the oldest bats were able to fly actively and over long distances. The fact that Onychonyctris finneyi has captured insects in flight 52.5 million years ago, can be concluded from the dentition of the new find.

Echolocation compared with ultrasound sounds

High-resolution radiographs of the inner abalone of Messel bats such as Archaeonycteris and Hassianycteris, although less perfected than in most of today's nocturnal hunters, suggest that echolocation was already practiced 47 million years ago Ultrasonic sounds down. The fossil remains of food detected in the stomach area also show that the ancestors of today's bats have fed exclusively on insects.

Although the dentition of Onychonycteris finneyi allows for an insectivore, comparative micro-X-rays exclude echolocation of prey insects by onychonycteris ultrasound sounds, the researchers said. The structures preserved in the new find, such as the very small inner ears, the shape of the Geh rkn chelchen and the weak Aufh ngeapparat of the larynx prove in the oldest find so far the otherwise typical specialization sp Older bats, as they can already be predicted on the basis of examinations in the five and a half million years of recent trade fair finds.

Flying came first

According to the scientists, the findings obtained confirm that the bats have "detected" flying prior to echolocation with the ultrasound sounds that can not be heard by us. With detailed anatomical "equipment", onychonycteris would have been able to detect at worst a rough obstacle detection and avoidance with weak and radar technical very primitive signals,

As always with such sensational discoveries, the scientists involved in the study hope to find Nancy B. Simmons, Kevin L. Seymour, Jørg Habersetzer and Gregg F. Gunnell of the American Museum of Natural History, the Royal Ontario Museum, the Senckenberg Research Institute and the Museum of Paleontology of the University of Michigan on more copies. Simultaneously with the publication of the Nature article, the fossil at the Senckenberg Research Institute is examined in a micro-tomograph using a special procedure to identify further details still hidden in the rock.

(Research Institute Senckenberg, 14.02.2008 - DLO)