Archaeopteryx

This article is about archaeopteryx which is also known by its German name Urvogel that means the first bird or original bird that belongs to the genus feathered dinosaur. The palaeontologists believed that archaeopteryx the first primitive archaeopteryx bird from the 19th century till the 21st century by the study of the age of the fossils available and it belongs to the oldest bird group known as Avialae that includes all the theropod dinosaurs that are very closely related to the structure of the bird. During the late Jurassic period that is around 150 million years ago when Europe was an extensive group of islands within a warm shallow tropical sea much closer to the equator than it is now, the archeopteryx originated from a piece of European island that is now known as Portugal and Southern Germany.  The archeopteryx, for a very long period of time, was considered to be the evolutionary species of the tree bird. It is because it had an average size of a common magpie but can grow maximum to a size of a raven.it has a maximum size measuring about 1 foot 8 inches in length. Despite having a smaller body with wide wings and the ability to fly and glide they are considered more as a small Mesozoic dinosaur because of their similarities than that of a bird. They possess a jaw with very sharp teeth, feathers that proves they are warm-blooded, three toes with sharp claws and one hyperextensible toe that is known as killing toe and various other skeleton features that proves that archaeopteryx is the member of the fossil age remains that indicated the presence of two different ancestral groups of non-avens and birds. That is why they are very important for the study of evaluation of birds as well as for the study of dinosaurs. 

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Archaeopteryx Description

Most of the fossils of arkiyopterix dinosaurs (the dinosaurs with wings) were first recovered in 1861 at Solnhofen limestone formation in Bavaria, Germany during the Tithonian stage. Later between the 19th to 21st century, similar bird-like fossils of the same age were discovered in Liaoning deposit situated at Xiaotingia Zhengi, China. Most of the studies and the physician attribute of this extinct species have been confirmed from the well-preserved fossil specimen. The solnhofen limestone is a very fine-grained limestone of the Jurassic age formed in a topical marine environment that is shallow like a coral lagoon. Over the centuries the lime mud silt accumulated slowly over the limestone and allowed it to get well preserved for fossil study. According to the palaeontologists observed that the body length of the real archaeopteryx reaches up to 500 millimetres or 2inches with broad wings that have a rounded edge and a long tail which is more than the length of the body. The total mass of the real archaeopteryx was around 0.8 to 1 kilograms. Though structure and the arrangements of the feathers on the wing were not as elaborated in studies as the other features of the species but the structured arrangement of feathers are quite similar to that of the modern birds that indicate it could fly. Insite of having numerous avian features. The arkiyopterix had a greater resemblance with the non-avian dinosaurs in terms of features like it has small teeth unlike the modern birds with a long bony tail that it had shared with the other dinosaur species. The features such as a wishbone, flight feathers as well as partially reserved toe resemble the avian group. But the ankle bone, the long inverted V-shaped tail, interdental plates and the obturator connected with the ischium greatly resembles the theropod family of the dinosaur. The arkiyopterix had three separate digits that end in a claw at each digit of the forelegs. A diagram comparing the species with the human on a size scale.

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Plumage  

The plumage or the arrangement of the feathers as the outer covering of the archaeopteryx indicates that they were well developed for them to fly but unlike the structure of flight feathers of the modern bird, they were asymmetrical in the case of this dinosaur species. But the archaeopteryx as well as the modern bird having vanes that are the flattened part on either side of a feather provided them stability with the epidermal growth of the feathers that forms a distinctive outer covering arrangement. The tail feathers as compared to the wings were less asymmetrical with firm vanes to give it the structural strength. Even the thumb of this specific avian dinosaur did not possess a movable tuffet of alula. It is documented that on the Berlin specimen that the leg had well-developed strides of feathers where some of them have a basic contoured structure of feather but some there was a lack of barbicels and thus somewhat decomposed. But in some parts of the leg, they were firm and thus were able to support the flight. A speck of pennaceous feathers that ran along the back of the archaeopteryx is very similar to that of the contour feathers of body plumage of the modern birds. These pennaceous feathers were symmetrical but are not as stiff as the feathers that supported the flight. The traces of the feather that was found in the Berlin species comprised of a layer of fine feathers that are found beneath the strong exterior feathers and are fluffy and decomposed and appeared more like fur than like a feather. The studies suggest that the flight pattern of this feathered dinosaur was different as compared to the modern bird. They were capable of taking a powerful short flight to escape from the predators due to the presence of a strong bone to handle low torsional forces rather than high torsional force that required rapid and continuous flapping and soaring of wings. There is no indication of the presence of a feather on the head or neck of the species. The plumage of the archaeopteryx’s fronted tail with the modern bird’s fan tail is illustrated below.

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Colouration 

In 2011, with the help of the energy display X-ray analysis by scanning electron microscopic technology the colouration of the archaeopteryx fossil was studied that indicated the structure of the melanosomes of the isolated specimen that was feathered as per a study published in 1861. The results were then compared with the 87 existing species of birds that are closely related to the archaeopteryx and the calculation suggests that the colour of the species is about 95% black. The study pointed out that the black colouration of the feathers with pigmented distal tip is mostly due to the presence of the dorsal covert that have partly covered the primary feathers of the wings. The journal of the analytical atomic spectrometry that was published in the year 2013 has new studies that point out the colouration characteristics of most archaeopteryx that includes the complex light and dark colour of the plumage with pigmentation on the distal tip as well as vanes. Some of the other studies strengthen the black colouration of the species with the modern flight characteristics of the melanosomes birds that have special structural characteristics as that of the dinosaur species that strengthen the feathers to support the flight. This colour distribution study was completely based on the presence and spread of sulphate in the fossil.

The restoration illustration interpreting the colouration of the archaeopteryx is given below. 

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Archeopteryx Classifications

By various study, the genus Archaeopteryx has been considered in either of the two species by various palaeontologists, namely, A. lithographia and A. siemens. According to a german palaeontologist named Mayer, the category A. lithographia is referred to as single feathered but the taxonomy history of both species is complex. The structural formation of the feather that was described for the original archaeopteryx is not relatable with the structure and function of the flight feathers described for the feathered theropods that include archeopteryx. Thus the winged feathered described in many studies is considered to be present in the contemporary archaeopteryx that belongs to the small species of feathered theropods. Since the feather characteristics have been defined for a particular species of feather theropod, thus the skeleton found was no longer considered as archaeopteryx. Thus there was great confusion in creating a significant international code of zoological nomenclature. 

Species

It was considered that all the specimens belong to the same species of A. lithographia and the difference that exists between the specimens is either due to the difference of ages or because of actual species diversity. For instance, fossils of the Munich, eichstatt, Thermopolis and the solnhofen specimens are different in characteristics that are found in Harlem, London and Berlin species. Either the species when compared was found too small or too large with different proportions of fingers, a more slender and projecting mouth and nose with forwarding pointed teeth and the presence of breast bones that is a long flat bone located in the centre of the chest.

In 2007 with the study of well-preserved species along with the newly discovered species of Thermopolis, the archaeopteryx was categorised into two categories, namely, A. lithographia that includes a specimen of solnhofen and London species and A. siemens includes specimens of Berlin, Munich and Thermopolis. A. lithographia was distinguished from A. siemens on the basis of the following characteristics:-

1. It possesses a high strength flexor retinaculum on the foot claws that is otherwise straight and simple construction on the foot claws of A. siemen specimen.

2. They have a very narrowed and restricted portion of crown in some teeth with a strong and stouter group of bones present between foot and ankle called metatarsus. 

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Flight and Growth

Unlike the wings of the modern bird, the feathers of the wings of archaeopteryx were asymmetrical and the plumage of the tail is comparatively broader. Thus it is presumed that the wings were most probably used to lift the generation but it is still unclear whether they were capable of flying or just gliding over surfaces. Because of the lack of the bony breastbone, it lacks the high flight property and is not the strong flier but flight muscles must have been attached to the boomerang-shaped wishbone and pair of bone present in all the vertebrate at the shoulder assembly which is more like plate-shaped in this species or attached with the cartilage type sternum. Also, there was no sign of the angular arrangement of the dorsal that is found in a modern bird that suggested that it could not go for higher stock as its wings could not lift over its back. As the wings of the species were huge that may have resulted in the reduced stall speed and small turning radius. However, due to the asymmetrical and rounded edge of the wings, it might have helped them fly through the cluttered environment. The asymmetrical flight feathers present on the hind wings might have added to their aerial mobility. A study published in 2006 has suggested that their flying structure has resulted in 12% of the total aerofoil. Thus the stall speed because of the same factor has reduced to 6% and the turning radius by 12%. In 2004, the CT scan of the braincase of one of the archaeopteryx in London was done and it was found that its brain was larger than that of normal dinosaur species indicating that it had the larger brain lobes to support flying. Through a recent study on the geometry of flight feathered barb it is established that the angular large barb present in the trailing vane possessing the feathers that help them in taking strong and high flight are absent in the archaeopteryx that denotes that it had a weak flight structure.

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Growth

A study in 2009 has estimated that the growth of the archaeopteryx is much slower than that of the bird or other dinosaur species because of poor vascularization of the outermost bone of the archaeopteryx and also in the living vertebrates. Thus the poorly vascularized bones resulted in the slow growth rate of the species. The scientists also believed that the skeleton excavated from the sediment fossils are of juvenile archaeopteryx. In order to observe the size of the species in terms of its growth rate as to how long it takes to take a shape of a fully adult archaeopteryx was calculated and the result indicated that it might have taken 970 days that were equivalent to 375 days in late Jurassic year to grown to a maximum length of a foot with a weight near about 0.8 to 1 kg. Thus a graphical representation of the growth rate of archaeopteryx as compared to other dinosaur species of the same age is illustrated below.

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Conclusion

The archaeopteryx is the original revolutionary form of the modern bird through many of its structural features to that of a theropod dinosaur. Thus it falls under the genus of feathered dinosaurs. They originated from Europe in the early Jurassic era when Europe was a warm shallow tropical sea area much nearer to the equator than now and that has been Germany in today’s world map. They fall under the group called Avialae. They were mainly carnivorous in nature and mostly fed on small reptiles, mammals, amphibians and insects. Due to their poor vascularized bone, their growth was much slower than that of the other dinosaur species or bird. They are structurally different from the modern bird and due to asymmetrical feather structure on their forelegs and wings they could not fly very high but could take short flights to defend themselves from the predators but they had gliding characteristics. They are mostly the size of a chicken and weigh around 1lbs. Their colour according to the presence of the melanin-producing and synthesizing glad was assumed predominantly black with pigmentation on the tip of the feathers. They had a slender body with a long tail longer than its body. Most of their fossils that are studied today have been protected by the deposit of the silt over the solnhofen limestone rock that includes the decomposed imprint of the species.