Pterodactylus

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Pterosauria

Family:Pterodactylidae

Genus:Pterodactylus

Species:Pterodactylus antiquus

Introduction

The pterosaurs were the first known vertebrates to achieve active flight and ranged in size significantly, from tiny species with a wingspan of only 25 centimeters (10 in) to the large Quetzalcoatlus species with a wingspan of more than 12 meters (40 ft). The emergence of pterosaur flight evolved separately from that of other flying vertebrates (birds and bats), displaying an example of convergent evolution. These “winged lizards” are often thought of as the rulers of the sky during the age of the dinosaurs. Although species of pterosaurs lived from the Triassic to the Cretaceous, these creatures are not dinosaurs.

Pterodactylus is a genus of the pterosaurs. Although pterosaur species have been found as early as the Late Triassic (230 million years ago) and as late as the end of the Cretaceous (66 million years ago), Pterodactylus species first emerged during the Late Jurassic.

One of the most common misnomers is the use of the name "pterodactyl" to describe all flying reptiles, frequently used in non-scientific literature. Such an animal does not actually exist in paleontological science. The name pterodactyl is often used to incorrectly describe either a Pterodactylus or Pteranodon, two different genera of pterosaur.

Classification

Current classification of species relies predominately on two systems, the Linnaean system and cladistics. Carolus Linnaeus developed the Linnaean system in the mid 1700s in an attempt to categorize similar organisms by placing them into hierarchical groupings, that is, kingdom, phylum, class, order, family, genus, and species. Cladistics is the second classification system used and is favored by many paleontologists. First introduced in the 1950s, cladistics aims to highlight relationships between organisms in regards to kinship and ancestry, grouping species with common traits and common ancestors into “clades.”

The pterosaurs are classified as flying archosaurian reptiles and are thought to have evolved from a bipedal archosaur species from the Late Triassic period. The pterosaurs comprise two different types: the basal Pterosauria (also known as rhamphorhynchoids) and the pterodactyloids. The basal Pterosauria, distinguished by their long tails, first showed up in the fossil record during the Late Triassic (230 million years ago) before going extinct during the Late Jurassic (163–145 million years ago). Pterodactyloids are the descendents of the basal Pterosauria and are characterized by their short tails and later arrival, first appearing in the Late Jurassic and going extinct at the same time as the last dinosaurs during the K/T extinction event (Cretaceous–Tertiary extinction event), occurring at the end of the Cretaceous Period (66 million years ago).

The species Pterodactylus antiquus is considered the type species of the Pterodactylus genus. Paleontologists have hotly debated the number of Pterodactylus species since the discovery of the first flying reptile fossil in 1874. Some claim there are more than a dozen; others believe there is probably only one (or possibly two) known, P. antiquus and possibly P. kochi, surmising that other specimens are either juveniles of this species or a different genus.

Anatomy

During the Late Jurassic, the pterosaur species underwent a significant shift in anatomy from the basal Pterosauria to the Pterodactyloidea (typified by the Pterodactylus). The long tails were shortened, the forearm bones lengthened, and a short fifth toe emerged.

Pterodactylus species possessed long beaks, filled with widely spaced teeth, long necks, and short tails. Compared to other pterosaurs, however, Pterodactylus was a relatively small-sized animal. Specimens have been found with wingspans ranging from 0.35 to 2.5 meters (1–8 ft).

Although the Pterodactylus looked ungainly, they were well adapted for active, flapping flight. Their bones were light and hollow, filled with air sac structures as an adaptation for flying maneuverability. Their tough, thin-membrane wings (patagium) stretched between the fore and hind legs and the tail. The elongated forearms terminated in fingers, with the fourth finger being very long and forming the end of the wing. Their light bones meant their bodies were also very light, weighing less than 45 kilograms (100 lbs).

A number of pterosaur species had crests on their skull, and the crest on the skull of Pterodactylus was fibrous, light, and lacked bony support. Theories about the function of this anatomical feature suggest either it was used as a type of canard rudder to aid flight, or it was vividly colored and used by males in courtship displays. Some pterosaur species, possibly including Pterodactylus, also had coats made up of hairlike material known as pycnofibers.

Intelligence

Similar to modern-day birds, the brains of pterosaur species had small olfactory bulbs yet large optic lobes. This indicates that vision and motor coordination were much more important than a good sense of smell and were likely adaptations for improved flight and hunting ability.

Reproduction and Population

Although fossils that do exist can provide clues, the process of fossilization is very rare and leads to an incomplete picture of population numbers and behavior of prehistoric animals. This is particularly so for the fragile and light boned pterosaur species, whose fossil record is considered patchy. Although flying reptile species have been found on all continents, population numbers are unknown. Pterodactylus has only been found in Europe (in the Solnhofen Formation in Bavaria, as well as France and England), and fragments in Tendaguru, Tanzania.

Pterosaur fossils do suggest that these species were sexually dimorphic. Larger-sized males, possessing larger head crests, indicates that pterosaurs, such as Pterodactylus, relied on courtship displays for attracting mates. A gregarious social system is also hinted at in the fossil record, with some species of pterosaurs forming possible flocks.

These reptiles were also oviparous, and evidence indicates that females possessed a wider pelvic canal to allow for the passage of large eggs. Immature specimens of pterosaurs indicate that these species initially required parental care and feeding support. Remains of Pterodactylus do suggest, however, that they were capable of hunting and flying during the (probably later) juvenile stage before full maturity.

Diet

By examining dental features such as shape and size, paleontologists are able to gain an understanding of a species’ probable diet. Pterodactylus was carnivorous, like most reptiles. Its long sharp beak and relatively long teeth were well adapted for its diet of primarily fish and small-sized sea-dwelling species such as mollusks and crustaceans. Evidence from fossil tracks suggests this species lived and hunted in coastal areas and in shallow water. Other pterosaurs species fed on insects and fruit, indicating that Pterodactylus may have supplemented its seafood diet with such foods, although this is unproven.

Though Pterodactylus were predators, their relatively small size in comparison with other species that lived at the same time made them vulnerable to predation from other carnivores. Note that dinosaur teeth of Spinosaurus and Velociraptorine have been found in some pterosaur fossils. The ability of Pterodactylus to fly, however, would have afforded them some protection.

Behavior

One of the most significant differences between the basal Pterosauria and the pterodactyloids is the mechanics of their flight. Historical views held that pterosaur species could only manage to glide over relatively short distances. Later evidence has strongly suggested that this was probably true for the basal pterosauria, but some species of pterodactyloids possessed anatomical features that would have allowed them to achieve sustained flight, flying long distances for extended periods.

The study of pterosaur behavior, particularly in regards to terrestrial locomotion, has been controversial. Historical consensus stated that these species were, at most, bipedal in terrestrial environments, much like modern-day birds. However, evidence from Late Cretaceous trackways in Mexico and Late Jurassic trackways in southwestern France have provided very strong evidence to support the theory that Pterodactylus not only were capable of flight, but also they were also quadrupedal.

Another intriguing discovery, based on fossilized swim tracks, is the possibility that some pterosaur species were capable of swimming or floating in water. Some Pterodactylus specimens also show slight webbing between the toes of their hind foot, supporting the idea of swimming ability. Such evidence provides clues to their coastal habitats and fish feeding behavior.

Habitat and Other Life Forms

Most of the Late Jurassic was characterized by a warm and moist climate. Although some arid areas were still present, riparian areas were covered in lush green vegetation including plants such as bennettitaleans, cycad, ferns, ginkgoes, and conifers.

Pterodactylus emerged during the Late Jurassic period some 160 million years ago. These flying reptiles were the rulers of the sky and lived during the time of the dinosaurs. The source of many Pterodactylus finds, in Bavaria, is the site of the Solnhofen Limestones, which, during the Late Jurassic, was a lagoon whose waters were highly saline. Among Pterodactylus's contemporaries in Bavaria were Archaeopteryx, Compsognathus, and Wellnhoferia, along with a significant population of Halecostomi (fish) and other pterosaurs.

The Late Jurassic period was a high period for Pterodactylus; they shared the earth with some of the largest sauropod herbivores that have ever existed, such as Camarasaurus, Apatosaurus, Diplodocus, and Brachiosaurus, and large carnivore species including Allosaurus, Torvosaurus, Marshosaurus, and Ceratosaurus.

Pterodactylus hunted for fish and seafood along coastal areas. During the Late Jurassic, the oceans were alive with plesiosaurs (a carnivorous reptile) and ichthyosaurs (a carnivorous reptile similar in appearance to fish and dolphins).

Research

The first Pterodactylus antiquus fossil was discovered in the Upper Jurassic Solnhofen Limestones in Germany in 1784. Italian scientist Cosimo Alessandro Collini described it and initially believed it was an unknown marine animal or perhaps a type of unusual bat. In 1801, however, French zoologist Georges Cuvier correctly identified it as a winged reptile and named it Pterodactyle. After the initial discovery, many other pterosaur fossils were found in the German limestones, including numerous species of the rhamphorhynchoid and pterodacyloid suborders. Between the 1850s and 1870s, pterosaur bones had also been found in other regions of Europe, including England and France, and Africa. Although the pterosaurs appear to have been distributed globally, Pterodactylus has only been confirmed in Europe and possibly Africa.

The discovery of flying reptiles marked a significant change in the ideas of prehistoric life, and the origin of pterosaur flight continues to be controversial. Many theories have been posited, but three are thought the most likely: the arboreal leaping theory, the arboreal parachute theory, and the running theory. The leaping theory states that arboreal species evolved flight by leaping and gliding from trees. The parachute theory states that ancestor species would parachute from trees to escape predators and hunt, which pushed the evolution of larger membranes and then flight. The running theory states that ancestor bipedal species ran along the ground before leaping into the air to catch insects, forming the foundation to flight.

Much research by the twenty-first century focused on classification, with most previously proposed Pterodactylus species being discarded in favor of P. antiquus. However, some debate continued as to whether P. antiquus and P. kochi, and possibly other species, were one and the same or separate. Broader pterosaur research also found that some species had hairlike pycnofibers coating their bodies, suggesting they may have been warm-blooded. Most reconstructions of Pterodactylus now show it with this kind of furry coat.

Bibliography

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