Palaeochiropteryx
Encyclopedia
Palaeochiropteryx is an extinct genus
of bat
from the Middle
Eocene
of Europe
. It contains two very similar species
– Palaeochiropteryx tupaiodon and Palaeochiropteryx spiegeli, both from the famous Messel Pit
of Germany
. They are usually found complete and exceptionally preserved, even retaining the outlines of their fur
, ears, and wing membranes.
They are one of the oldest bats known, existing around 48 million years ago. Despite this, they were already quite advanced, showing evidence of the ability to hunt by echolocation
like modern insect-eating bats.
Palaeochiropteryx were small bats, with a wingspan between 25 to 30 cm (9.8 to 11.8 in). Their wings were short but broad, indicating an adaptation for slow but highly maneuverable flight beneath forest canopies and among dense vegetation. They preyed mostly on moth
s and caddisflies and were probably nocturnal.
s of both species of Palaeochiropteryx were first recovered from the Messel Pit
, near the village of Messel
, Germany
in 1917. They were described and named by the Swiss naturalist
Pierre Revilliod. He placed them under their own family
– Palaeochiropterygidae
. The name Palaeochiropteryx means "Ancient hand-wing", from Greek
παλαιός (palaios, "old"), χείρ (kheir, "hand"), and πτέρυξ (pteruks, "wing").
The two species have only been found at Messel. They are quite common and account for three quarters of all bat fossils found there, with Archaeonycteris
, Hassianycteris, and Tachypteron making up the rest. Like other fossils from the locality
, they are often found in remarkable states of preservation, retaining traces of fur, stomach contents, wing membranes, and even ears. The two species belonging to the genus are the following:
Palaeochiropteryx tupaiodon Revilliod, 1917Palaeochiropteryx spiegeli Revilliod, 1917
In 1980, their parent taxon
, Palaeochiropterygidae, was merged with Archaeonycteridae
by the paleontologists Björn Kurtén
and Elaine Anderson
. Authorities specializing in bat fossils, however, maintain the distinction between the two families.
The Messel Pit formation dates from the Lutetian
age of the Middle Eocene. Between 48.6 ± 0.2 and 40.4 ± 0.2 million years ago.
Along with Onychonycteris
, Icaronycteris
, Hassianycteris, and Archaeonycteris; members of Palaeochiropteryx are among the oldest known bats. All are identifiable by more or less complete skeletons. While there are fossils of other older bats such as Australonycteris, these are only recognisable from fragmented examples. Close relatives of Palaeochiropteryx include the Middle Eocene Cecilionycteris, Lapichiropteryx and Microchiropteryx, all recovered from partial remains from Germany
, China
, and India
, respectively.
Both P. tupaiodon and P. spiegeli were small bats. P. speigeli is slightly larger than P. tupaiodon. P. tupaiodon had an estimated body mass of 7 gram and a forearm
length of 39 to 46 mm (1.5 to 1.8 in). P. spiegeli was slightly larger and heavier, with an estimated body mass of 10 gram and a forearm length of 43 to 49 mm (1.7 to 1.9 in). They had wingspan
s between 25 to 30 cm (9.8 to 11.8 in) in length.
The complete dentition
of Palaeochiropteryx is known. They had 38 teeth, composed of four upper and six lower incisor
s, four canine teeth
, twelve premolar
s, and twelve molar
s. Their dental formula is the same as at least three living families of bats, such as bats from the genus Myotis.
as Grube Messel) is one of the most famous and richest fossil sites of the world. The site is renowned for the quality of preservation in the fossils found. Preserved in very fragile bituminous shale
, they often retain exquisite details of the soft parts of animals and plants. As its name suggests, the pit is a dry depression about 60 m (196.9 ft) deep; the surface is around 200 m (656.2 ft) above sea level. It covers an area approximately 1000 m (3,280.8 ft) by 700 m (2,296.6 ft).
48 million years ago, the pit was a small but very deep lake
, originally at least 190 m (623.4 ft) deep. It was located around 10° south of its current location in a tropical and subtropical Eocene
Europe
. Messel Pit was volcanic in origin, probably a caldera
created by a massive volcanic eruption. It remained geologically
and tectonically active
during the Eocene, intermittently releasing puffs of poisonous volcanic gas
es. A virtually stagnant
lake, its low oxygen
levels enabled the types of preservation found in its fossils.
Messel pit was surrounded by a lush tropical jungle
ecosystem
teeming with wildlife. Among these were several bat species, including Palaeochiropteryx. Fossils of Palaeochiropteryx (particularly Palaeochiropteryx tupaiodon) occur in great abundance in the pit. They account for three-fourths of all recovered bat fossils in the area.
The fossils recovered are usually of healthy adults with full stomachs, making the reasons why they ended up at the bottom of a lake a bit of a mystery. They may have been snagged or poisoned by thick algal mat
s on the surface of the lake as they swooped down to drink. Or they may have been knocked out midair by poisonous fumes rising from the lake and subsequently drowned.
The small bodies of Palaeochiropteryx coupled with their relatively broad wingspan indicate that they may have been low level flyers, much like some modern bats with the same body structure. They specialized in hunting close to the ground, beneath the jungle
canopy and among vegetation unlike other bats found in Messel Pit which flew at higher altitude
s (an early evidence of niche partitioning). They had low wing loading
and low aspect ratios
, suggesting that they were relatively slow flyers but were able to maneuver midair quickly – essential for avoiding collisions with the numerous obstacles near the forest floor. This fact may have made them especially vulnerable to the poisonous gases of the former Messel lake, explaining the abundance of their fossils.
The shape of their teeth and the stomach contents of the numerous extremely well preserved fossils of the Messel Pit indicate that Palaeochiropteryx were insectivorous. P. tupaiodon fed almost exclusively on (presumably slow-moving) moth
s of the primitive Microlepidoptera
family. P. spiegeli, on the other hand, also consumed caddisflies (Trichoptera
) in addition to moths. Most members of those insect families are active at night, giving a strong indication that Palaeochiropteryx were also nocturnal, or at best, active during twilight
(crepuscular
).
, Palaeochiropteryx (as well as Archaeonycteris and Icaronycteris) all have enlarged cochlea
e relative to the size of their skull
s. They are still smaller than that of modern echolocating insectivorous bats (Microchiroptera) but they are already larger than that of modern non-echolocating fruit-eating bats (Megachiroptera). Along with their known diets and habits, this is a clear evidence that Palaeochiropteryx was very much capable of echolocation like modern microchiropterans.
Smith (1977) suggested that these taxa represent an extinct clade of early microchiropterans which he dubbed Palaeochiropterygoidea. In contrast, Van Valen (1979) argued that these fossil forms are representatives of Eochiroptera, a primitive grade ancestral to both Megachiroptera and Microchiroptera. Novacek (1987) reanalyzed morphology of Icaronycteris and Palaeochiropteryx and concluded that they are more closely related to Microchroptera than to Megachiroptera. Most recently, Simmons and Geisler (1998) found that Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx represent a series of consecutive sister-taxa to extant microchiropteran bats.
Below is the phylogenetic tree
from Simmons and Geisler (1988) showing the proposed relationships of Palaeochiropteryx (in bold) with other extinct genera and with extant bats.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
from the Middle
Lutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between and . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene subepoch...
Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. It contains two very similar species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
– Palaeochiropteryx tupaiodon and Palaeochiropteryx spiegeli, both from the famous Messel Pit
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. They are usually found complete and exceptionally preserved, even retaining the outlines of their fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
, ears, and wing membranes.
They are one of the oldest bats known, existing around 48 million years ago. Despite this, they were already quite advanced, showing evidence of the ability to hunt by echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
like modern insect-eating bats.
Palaeochiropteryx were small bats, with a wingspan between 25 to 30 cm (9.8 to 11.8 in). Their wings were short but broad, indicating an adaptation for slow but highly maneuverable flight beneath forest canopies and among dense vegetation. They preyed mostly on moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s and caddisflies and were probably nocturnal.
Discovery and classification
FossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of both species of Palaeochiropteryx were first recovered from the Messel Pit
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
, near the village of Messel
Messel
Messel is a municipality in the district of Darmstadt-Dieburg in Hesse near Frankfurt am Main in Germany.The village is first mentioned, as Masilla, in the Lorsch codex.Messel was the property of the lords of Groschlag from ca. 1400 to 1799...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
in 1917. They were described and named by the Swiss naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Pierre Revilliod. He placed them under their own family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
– Palaeochiropterygidae
Palaeochiropterygidae
Palaeochirpterygidae is a family of extinct bats. It was originally erected by the Swiss naturalist Pierre Revilliod in 1917 after discoveries of Palaeochiropteryx fossils from the Messel Pit of Germany. Palaeochirpterygidae was merged into Archaeonycteridae by Kurten and Anderson in 1980, but...
. The name Palaeochiropteryx means "Ancient hand-wing", from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
παλαιός (palaios, "old"), χείρ (kheir, "hand"), and πτέρυξ (pteruks, "wing").
The two species have only been found at Messel. They are quite common and account for three quarters of all bat fossils found there, with Archaeonycteris
Archaeonycteris
Archaeonycteris was a primitive bat genus whose remains were found in Germany, France, England and India.-Species:*Archaeonycteris trigonodon Revilliod, 1917 - Messel Pit , Germany...
, Hassianycteris, and Tachypteron making up the rest. Like other fossils from the locality
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
, they are often found in remarkable states of preservation, retaining traces of fur, stomach contents, wing membranes, and even ears. The two species belonging to the genus are the following:
Palaeochiropteryx tupaiodon Revilliod, 1917Palaeochiropteryx spiegeli Revilliod, 1917
In 1980, their parent taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, Palaeochiropterygidae, was merged with Archaeonycteridae
Archaeonycteridae
Archaeonycteridae is a family of extinct bats. It was originally erected by the Swiss naturalist Pierre Revilliod as Archaeonycterididae to hold the genus Archaeonycteris. It was formerly classified under the superfamily Icaronycteroidea by Kurten and Anderson in 1980...
by the paleontologists Björn Kurtén
Björn Kurtén
Björn Olof Lennartson Kurtén was a distinguished vertebrate paleontologist. He belonged to the Swedish-speaking minority in Finland. He was a professor in paleontology at the University of Helsinki from 1972 up to his death in 1988...
and Elaine Anderson
Elaine Anderson
Elaine Anderson Steinbeck was an American actress and one of the first women to become a theatre stage manager.She was previously known as Elaine Anderson during her acting career...
. Authorities specializing in bat fossils, however, maintain the distinction between the two families.
The Messel Pit formation dates from the Lutetian
Lutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between and . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene subepoch...
age of the Middle Eocene. Between 48.6 ± 0.2 and 40.4 ± 0.2 million years ago.
Along with Onychonycteris
Onychonycteris
Onychonycteris is the most primitive of the two oldest known monospecific genera of bat, having lived in the area that is current day Wyoming during the Eocene period, 52.5 million years ago.-History and description:...
, Icaronycteris
Icaronycteris
Icaronycteris is an extinct genus of microchiropteran bat that lived in the early Eocene, approximately 52.2 million years ago. Four exceptionally preserved specimens are known from the Green River Formation of North America. There is only one thoroughly described species of bat in the genus, I...
, Hassianycteris, and Archaeonycteris; members of Palaeochiropteryx are among the oldest known bats. All are identifiable by more or less complete skeletons. While there are fossils of other older bats such as Australonycteris, these are only recognisable from fragmented examples. Close relatives of Palaeochiropteryx include the Middle Eocene Cecilionycteris, Lapichiropteryx and Microchiropteryx, all recovered from partial remains from Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, respectively.
Description
Palaeochiropteryx differed little from modern bats, a surprising fact given their relative age. Palaeochiropteryx had wings formed from enlarged hands, even though their wings were less advanced than the modern bats. For example, they still possessed a claw in the index finger.Both P. tupaiodon and P. spiegeli were small bats. P. speigeli is slightly larger than P. tupaiodon. P. tupaiodon had an estimated body mass of 7 gram and a forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
length of 39 to 46 mm (1.5 to 1.8 in). P. spiegeli was slightly larger and heavier, with an estimated body mass of 10 gram and a forearm length of 43 to 49 mm (1.7 to 1.9 in). They had wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
s between 25 to 30 cm (9.8 to 11.8 in) in length.
The complete dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
of Palaeochiropteryx is known. They had 38 teeth, composed of four upper and six lower incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s, four canine teeth
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
, twelve premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s, and twelve molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
s. Their dental formula is the same as at least three living families of bats, such as bats from the genus Myotis.
Paleobiology and paleoecology
Messel Pit (known in GermanGerman language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
as Grube Messel) is one of the most famous and richest fossil sites of the world. The site is renowned for the quality of preservation in the fossils found. Preserved in very fragile bituminous shale
Bituminous shale
Bituminous shale is an argillaceous shale impregnated with bitumen, often accompanying coal. It may contain kerogen; in that case it is classified as oil shale. When carbonaceous material is present in large amounts, bituminous shale grades into bituminous coal...
, they often retain exquisite details of the soft parts of animals and plants. As its name suggests, the pit is a dry depression about 60 m (196.9 ft) deep; the surface is around 200 m (656.2 ft) above sea level. It covers an area approximately 1000 m (3,280.8 ft) by 700 m (2,296.6 ft).
48 million years ago, the pit was a small but very deep lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
, originally at least 190 m (623.4 ft) deep. It was located around 10° south of its current location in a tropical and subtropical Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Messel Pit was volcanic in origin, probably a caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
created by a massive volcanic eruption. It remained geologically
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and tectonically active
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
during the Eocene, intermittently releasing puffs of poisonous volcanic gas
Volcanic gas
|250px|thumb|right|Image of the [[rhyolitic]] [[lava dome]] of [[Chaitén Volcano]] during its 2008-2010 eruption.Volcanic gases include a variety of substances given off by active volcanoes...
es. A virtually stagnant
Water stagnation
Water stagnation occurs when water stops flowing. Stagnant water can be a major environmental hazard.-Dangers:Malaria and dengue are among the main dangers of stagnant water, which can become a breeding ground for the mosquitoes that transmit these diseases.Stagnant or Stailment water can be...
lake, its low oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
levels enabled the types of preservation found in its fossils.
Messel pit was surrounded by a lush tropical jungle
Jungle
A Jungle is an area of land in the tropics overgrown with dense vegetation.The word jungle originates from the Sanskrit word jangala which referred to uncultivated land. Although the Sanskrit word refers to "dry land", it has been suggested that an Anglo-Indian interpretation led to its...
ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
teeming with wildlife. Among these were several bat species, including Palaeochiropteryx. Fossils of Palaeochiropteryx (particularly Palaeochiropteryx tupaiodon) occur in great abundance in the pit. They account for three-fourths of all recovered bat fossils in the area.
The fossils recovered are usually of healthy adults with full stomachs, making the reasons why they ended up at the bottom of a lake a bit of a mystery. They may have been snagged or poisoned by thick algal mat
Algal mat
An algal mat is a layer of usually filamentous algae on marine or fresh water soft bottoms. It may be considered one of many types of microbial mats. Algae and cyanobacteria are ubiquitous, often forming within the water column and settling to the bottom. In shallow environments, they are often...
s on the surface of the lake as they swooped down to drink. Or they may have been knocked out midair by poisonous fumes rising from the lake and subsequently drowned.
The small bodies of Palaeochiropteryx coupled with their relatively broad wingspan indicate that they may have been low level flyers, much like some modern bats with the same body structure. They specialized in hunting close to the ground, beneath the jungle
Jungle
A Jungle is an area of land in the tropics overgrown with dense vegetation.The word jungle originates from the Sanskrit word jangala which referred to uncultivated land. Although the Sanskrit word refers to "dry land", it has been suggested that an Anglo-Indian interpretation led to its...
canopy and among vegetation unlike other bats found in Messel Pit which flew at higher altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
s (an early evidence of niche partitioning). They had low wing loading
Wing loading
In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly,...
and low aspect ratios
Aspect ratio (wing)
In aerodynamics, the aspect ratio of a wing is essentially the ratio of its length to its breadth . A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings....
, suggesting that they were relatively slow flyers but were able to maneuver midair quickly – essential for avoiding collisions with the numerous obstacles near the forest floor. This fact may have made them especially vulnerable to the poisonous gases of the former Messel lake, explaining the abundance of their fossils.
The shape of their teeth and the stomach contents of the numerous extremely well preserved fossils of the Messel Pit indicate that Palaeochiropteryx were insectivorous. P. tupaiodon fed almost exclusively on (presumably slow-moving) moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s of the primitive Microlepidoptera
Microlepidoptera
Microlepidoptera is an artificial grouping of moth families, commonly known as the 'smaller moths' . These generally have a wingspan of under 20 mm, and are thus harder to identify by external phenotypic markings than macrolepidoptera...
family. P. spiegeli, on the other hand, also consumed caddisflies (Trichoptera
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
) in addition to moths. Most members of those insect families are active at night, giving a strong indication that Palaeochiropteryx were also nocturnal, or at best, active during twilight
Twilight
Twilight is the time between dawn and sunrise or between sunset and dusk, during which sunlight scattering in the upper atmosphere illuminates the lower atmosphere, and the surface of the earth is neither completely lit nor completely dark. The sun itself is not directly visible because it is below...
(crepuscular
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
).
Echolocation
From the results of radiographic analysisRadiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
, Palaeochiropteryx (as well as Archaeonycteris and Icaronycteris) all have enlarged cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
e relative to the size of their skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
s. They are still smaller than that of modern echolocating insectivorous bats (Microchiroptera) but they are already larger than that of modern non-echolocating fruit-eating bats (Megachiroptera). Along with their known diets and habits, this is a clear evidence that Palaeochiropteryx was very much capable of echolocation like modern microchiropterans.
Taxonomy and phylogeny
The fossil record of bats extends back at least to the early Eocene, and chiropteran fossils are known from all continents except Antarctica. Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx, unlike most other fossil bats, have not been referred to any extant family or superfamily. These Eocene taxa are known from exceptionally well-preserved fossils, and they have long formed a basis for reconstructing the early evolutionary history of Chiroptera.Smith (1977) suggested that these taxa represent an extinct clade of early microchiropterans which he dubbed Palaeochiropterygoidea. In contrast, Van Valen (1979) argued that these fossil forms are representatives of Eochiroptera, a primitive grade ancestral to both Megachiroptera and Microchiroptera. Novacek (1987) reanalyzed morphology of Icaronycteris and Palaeochiropteryx and concluded that they are more closely related to Microchroptera than to Megachiroptera. Most recently, Simmons and Geisler (1998) found that Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx represent a series of consecutive sister-taxa to extant microchiropteran bats.
Below is the phylogenetic tree
Phylogenetic tree
A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics...
from Simmons and Geisler (1988) showing the proposed relationships of Palaeochiropteryx (in bold) with other extinct genera and with extant bats.
See also
- Animal echolocationAnimal echolocationEcholocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
- Bat wing developmentBat wing developmentThe order Chiroptera , comprising all bats, has evolved the unique mammalian adaptation of flight. Bat wings are modified tetrapod forelimbs. Because bats are mammals, the skeletal structures in their wings are morphologically homologous to the skeletal components found in other tetrapod forelimbs...
- Flying primates theoryFlying primates theoryThe flying primates theory conjectures that megabats, a sub-group of Chiroptera , form an evolutionary sister group of Primates. This theory started with Carl Linnaeus, and was again advanced by J.D Smith in 1980...