Entomology, Ornithology & Herpetology: Current Research
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Evolution and Classification of Modern Species

Torrey Schoenebeck^{* *}Correspondence: Torrey Schoenebeck, Department of Chemistry, Jamia Millia Islamia University, Jamia Nagar, Okhla, New Delhi, India, Email:

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Description

Birds and ornithischian (bird-hipped) dinosaurs have similar hip structures, if the dinosaurian origin theory is right, birds actually descended from saurischian (lizard-hipped) dinosaurs. Hence, they separately arrived at their hip structure's state. In fact, theropods belonging to the strange family Therizinosauridae also developed the bird-like hip shape a third time.

Many other palaeontologists and experts in the evolution and development of feathers disagree with the alternative theory that birds (including maniraptoran "dinosaurs") evolved from early archosaurs like Longisquama. This theory is supported by a small number of scientists, most notably Larry Martin and Alan Feduccia.

Evolution and modern species

A problematic topic is the evolutionary classification of birds. A seminal work on the classification of birds is Sibley and Ahlquist's Phylogeny and Classification of Birds (1990). (although frequently debated and constantly revised). The majority of contemporary bird orders appear to be strong clades, according to the evidence. However, there is no great agreement among scientists regarding the precise relationships between the orders; evidence from present bird anatomy, fossils, and DNA have all been used to address the issue. The evolution of modern bird orders and their relationships are now well understood because to new fossil and molecular evidence, which was discovered in the middle of the 2000s. As an illustration, the Charadriiformes appear to represent an old and unique lineage.

On the other hand, two things need to be taken into account: Since the fossil record is inherently imperfect, molecular clocks cannot be deemed credible in the absence of appropriate fossil calibration. Second, the time and pattern of lineage separation in reconstructed phylogenetic trees correspond to the evolution of the studied characters (such as DNA sequences, morphological traits, etc.), not to the actual evolutionary pattern of the lineages; although these two should ideally not differ significantly, it is possible that they do in practise.

Given this, it is clear that fossil data, as opposed to molecular data, tends to be more accurate overall but also underestimates divergence times: Morphological traits, being the result of entire developmental genetics networks, typically only start to diverge some time after a lineage split would become apparent in DNA sequence comparison - especially if the sequences used contain many silent mutations.

Classification of modern species

In general, evolution happens at a pace that is much too slow for humans to see. However, compared to any potential speciation or other production of new species, the extinction rate of bird species is currently much higher. A variety of genes are permanently lost when a population, subspecies, or species disappears.

A possible rise in hybridization is another issue with evolutionary ramifications. This could result from habitat changes made by humans allowing overlapping populations of similar allopatric species. Forest fragmentation can connect previously isolated sections of open habitat by forming large open regions. Populations that were isolated for long enough to diverge greatly but not long enough to become sterile may now be interbreeding widely enough to jeopardise the survival of the original species. For instance, the numerous hybrid hummingbirds that can be found in northwest South America may pose a threat to the survival of the individual species.

Conclusion

Even though it is not thought to be a direct ancestor of current birds, the Jurassic-era basal bird Archaeopteryx is well known for being one of the first "missing links" to be discovered in favour of evolution in the late 19th century. Another early adopter, Confuciusornis existed in the Early Cretaceous. Protoavis texensis might be the ancestor of both, although given the fragmentary condition of this fossil, it is highly disputed if it was a bird. Among the other Mesozoic birds are the Confuciusornis, Enantiornithes, Yanornis, Ichthyornis, Gansus, and the Hesperornithiformes, a family of flightless divers that includes grebes and loons-like creatures.