Showing posts with label Transitional Forms. Show all posts
Showing posts with label Transitional Forms. Show all posts

Sunday, 24 November 2024

Refuting Creationism - How Pterosaurs Evolved


AI-generated image.
New fossil discovery reveals key step in the evolution of flying reptiles - Queen Mary University of London

Although creationists insist dinosaurs coexisted with humans before their god launched his genocidal flood, and even twist words like 'behemoth' in the Bible to try to show how the authors of genesis were familiar with dinosaurs (as though there was only one species) what they never explain is why the same authors said nothing at all about the pterodactyls that were contemporaneous with dinosaurs.

The real reason is of course that pterodactyls and dinosaurs lived in that vast expanse of time before 'Creation Week' when 99.9975% of everything that happened on Earth happened.

The evidence for this can be found in any palaeontological article that deals with the evolution of these first flying vertebrates, like this one about the discovery of a new species, Skiphosoura bavarica, which is also helping to understand how these reptiles evolved. It was identified by a team led by Dr David Hone, a palaeontologist from Queen Mary University of London. Early pterosaurs had a wingspan of about 2 meters (6 feet) but they evolved into massive creatures with wing spans up to 10 meters (30 feet). On the ground, some of them may have been at tall as a giraffe!

Pterosaurs, their evolution, and their relationship to dinosaurs. Pterosaurs were a group of flying reptiles that lived during the Mesozoic Era, from the late Triassic (about 228 million years ago) to the end of the Cretaceous (66 million years ago). They were the first vertebrates to achieve powered flight and were remarkable for their diversity in size, morphology, and ecological niches. Here's a detailed overview of pterosaurs, their evolution, and their relationship to dinosaurs:


  1. Evolutionary Origins
    • Pterosaurs belonged to the clade Pterosauria, which is part of the larger group Archosauria, making them close relatives of dinosaurs and crocodilians.
    • Their exact evolutionary origins are debated, but they likely evolved from small, ground-dwelling or arboreal reptiles within the clade Avemetatarsalia, which also includes dinosaurs and birds.
    • Early pterosaurs, such as Eudimorphodon and Dimorphodon, appeared in the late Triassic and already exhibited the characteristic wing structure.
  2. Anatomy and Adaptations for Flight
    • Pterosaurs' wings were formed by a membrane of skin, muscle, and other tissues stretched along an elongated fourth finger, which supported the main wing structure.
    • Other adaptations included:
      • Lightweight skeletons with hollow bones to reduce weight.
      • Keel-like breastbones to anchor powerful flight muscles.
      • Complex cranial crests in some species, possibly for display or aerodynamic purposes.
      • Unique respiratory adaptations with air sacs similar to those in modern birds.
  3. Relationship to Dinosaurs
    • Pterosaurs and dinosaurs share a common ancestor, but they are distinct groups within Archosauria. Pterosaurs are not considered dinosaurs.
    • The distinction lies in their lineage: dinosaurs belong to the clade Dinosauria, while pterosaurs form their own separate clade.
  4. Diversity and Evolutionary Trends
    • Pterosaurs diversified into two main groups:
      1. Rhamphorhynchoids (Early Pterosaurs):
        • Typically small to medium-sized.
        • Long tails with a vane or rudder-like structure at the tip.
        • Examples: Rhamphorhynchus, Dimorphodon.
        • Lived during the Triassic and Jurassic periods.
      2. Pterodactyloids (Advanced Pterosaurs):
        • Larger body sizes, including giants like Quetzalcoatlus with wingspans exceeding 10 meters.
        • Short tails or no tails.
        • Adapted to various ecological roles, such as fish-eating, filter-feeding, and scavenging.
        • Examples: Pteranodon, Istiodactylus, Quetzalcoatlus.
        • Dominated the skies during the Jurassic and Cretaceous periods.
  5. Ecological Roles
    • Pterosaurs occupied diverse ecological niches:
      • Some were piscivores, using long, pointed jaws to catch fish.
      • Others were filter feeders, like Pterodaustro, which had bristle-like teeth.
      • Large pterosaurs may have been scavengers or predators of small terrestrial animals.
      • Their crests may have been used for sexual selection, thermoregulation, or species recognition.
  6. Extinction
    • Pterosaurs went extinct at the end of the Cretaceous period during the mass extinction event 66 million years ago, likely caused by the asteroid impact and subsequent environmental changes.
    • Birds, which evolved from theropod dinosaurs, survived and continued to dominate the skies, taking over many of the ecological niches once held by pterosaurs.
  7. Fossil Evidence
    • Pterosaur fossils are relatively rare due to their fragile skeletons, but significant discoveries have been made worldwide, revealing exquisite details of their anatomy and even soft tissues like wing membranes and pycnofibers (hair-like structures covering their bodies).



Key Distinctions from Dinosaurs
  • Dinosaurs were primarily terrestrial, with a diverse range of locomotion and body plans, whereas pterosaurs were adapted for flight.
  • Birds are considered modern-day dinosaurs (descendants of theropods), but they are not descended from pterosaurs.



Pterosaurs are an incredible example of evolutionary innovation, showcasing how vertebrates conquered the skies long before birds. Their fossils continue to provide insights into the complexity of prehistoric life and the adaptive potential of ancient reptiles.
Dr Hone's team have published their findings in the journal Current Biology and describe it in a Queen Mary University news release:
New fossil discovery reveals key step in the evolution of flying reptiles
A remarkable new fossil discovery is shedding light on how flying reptiles, known as pterosaurs, evolved from their early forms into the later giants that ruled prehistoric skies.
The new species, named Skiphosoura bavarica, was identified by a team led by Dr David Hone, a palaeontologist from Queen Mary University of London. Their findings were published today in the journal Current Biology.

The pterosaurs, close relatives of dinosaurs, were the first vertebrates to achieve powered flight. While early species typically had wingspans of about 2 metres, later pterosaurs evolved into enormous forms with wingspans reaching 10 metres. The discovery of Skiphosoura bavarica provides critical insights into how these transformations occurred.

Hailing from southern Germany, Skiphosoura boasts a rare, nearly complete skeleton preserved in three dimensions—a significant contrast to the often-flattened fossils of its relatives. Measuring about 2 metres in wingspan, the new species’ most striking feature is its short, stiff, sword-like tail, which inspired its name: “sword tail from Bavaria.”

This is an incredible find. It really helps us piece together how these amazing flying animals lived and evolved. Hopefully, this study will inspire more research into this important evolutionary transition.

Dr. David William Elliott Hone, lead author, School of Biological and Behavioural Sciences
Queen Mary University of London, UK.
For two centuries, scientists divided pterosaurs into two major groups: early non-pterodactyloids, characterised by short heads, long tails, and specific wing and toe structures, and the later pterodactyloids, which had larger heads, shorter tails, and other adaptations for efficient flight. Intermediate species, like the Darwinopterus discovered in the 2010s, showed how the head and neck evolved first. Skiphosoura represents a critical step beyond the Darwinopterus. Its head and neck resemble the more advanced pterodactyloids, while its wrist, tail, and foot show transitional features. These traits help trace the gradual adaptations that allowed later pterosaurs to grow to massive sizes. The study also reconstructed the evolutionary family tree of pterosaurs, placing Skiphosoura between Darwinopterus and true pterodactyloids. Additionally, a Scottish pterosaur named Dearc was identified as a key intermediate between early pterosaurs and Darwinopterus. Together, these findings form a near-complete evolutionary sequence for pterosaurs, detailing how their anatomy changed over time. The discovery was made possible through the efforts of an international team. Adam Fitch, from the University of Wisconsin-Madison, highlighted the significance of Skiphosoura:

Pterosaurs have long been symbols of the unique life of the past. Skiphosoura represents an important new form for working out pterosaur evolutionary relationships and how this lineage arose and changed.

Adam Fitch, co-author
University of Wisconsin-Madison UW Geology Museum, Madison, WI, USA.

Having worked on over 60 pterosaurs from the Solnhofen limestone, it became clear during preparation that this fossil displayed features from both major groups of pterosaurs, with the shortened tail being a crucial diagnostic trait.

Stefan Selzer, co-author
Grabenäcker 12, Hemhofen, Germany.

Bruce and René Lauer of the Lauer Foundation, who contributed to the project, underscored the importance of modern techniques such as UV photography in uncovering fine details of the specimen.

We are proud to bring this important specimen to science and further the understanding of pterosaur evolution.

Bruce Lauer, co-author
Lauer Foundation for Paleontology, Science and Education
Wheaton, IL, USA.

With its blend of cutting-edge research, meticulous preparation, and international collaboration, the study of Skiphosoura bavarica offers a significant leap forward in understanding the evolutionary journey of these extraordinary flying reptiles.
Highlights
  • A new pterosaur, Skiphosoura bavarica, is named from the Jurassic of Germany
  • The specimen is much larger than other known forms and is preserved in three dimensions
  • The Skiphosoura helps document the transition from early pterosaurs to the pterodactyloids
  • The tail is short but retains the supporting structures of earlier forms
Summary For over a century, there was a major gap in our understanding of the evolution of the flying Mesozoic reptiles, the pterosaurs, with a major morphological gap between the early forms and the derived pterodactyloids.1 Recent discoveries have found a cluster of intermediate forms that have the head and neck of the pterodactyloids but the body of the early grade,2 yet this still leaves fundamental gaps between these intermediates and both earlier and more derived pterosaurs. Here, we describe a new and large Jurassic pterosaur, Skiphosoura bavarica gen. et sp. nov., preserved in three dimensions, that helps bridge the gap between current intermediate pterosaurs and the pterodactyloids. A new phylogeny shows that there is a general progression of key characteristics of increasing head size, increasing length of neck and wing metacarpal, modification to the fifth toe that supports the rear wing membrane, and gradual reduction in tail length and complexity from earlier pterosaurs into the first pterodactyloids. This also shows a clear evolution of the increasing terrestrial competence of derived pterosaurs. Furthermore, this closes gaps between the intermediates and their ancestors and descendants, and it firmly marks the rhamphorhynchines and ctenochasmatid clades as, respectively, being the closest earliest and latest groups to this succession of transitional forms.
Figure 1 Key elements of Skiphosoura
  1. The anterior part of the skull with the premaxillary crest and large teeth. Also seen is the humerus. Scale bar, 100 mm.
  2. The short caudal vertebrate with long zygapophyses and the elongate chevrons. Scale bar is 10 mm.
ca, caudal vertebra; cn, chevron; dr, dorsal rib; fe, femur; hu, humerus; pb, pubis; pm, premaxilla; wpx 1, wing phalanx 1. See also Figures S1, S2, S7, and S9

Figure 2 Simplified phylogeny of Macronychoptera showing the phylogenetic placement of Skiphosoura bavarica gen. et sp. nov
The new taxon is recovered outside of Pterodactyloidea as a late-diverging member of a grade of non-pterodactyloid monofenestratans. Note that Monofenestrata also lies within an earlier-diverging grade of “rhamphorhynchids” (Dorygnathus to Angustinaripterus) and that “rhamphorhynchines” (Rhamphorhynchini, Dearc, Angustinaripterus) here represent the closest relatives of Monofenestrata. See also Figure S10 and Table S2.
Figure 3 The transition of pterosaur proportions across the transition from early pterosaurs to the pterodactyloids
Upper left: Nopsca curves of the proportions of major elements of the skeleton scaled against the length of the humerus showing the transition of major proportions. Center: simplified phylogeny showing the transition of key characters in the evolution of pterodactyloids from the rhamphorhynchines and “through” the early monofenestratans. Skeletals showing the transition with representational taxa: Rhamphorhynchus, Dearc, Darwinopterus, Skiphosoura, and Pterodactylus. This shows the transitions of multiple features across the tree: (1) the increasing length of the skull and increase of the size of the naris before fusion to form the NAOF, (2) increase in the length of the cervical series, (3) proportional reduction in the length of the wingfinger and increase in the length of the proximal wing, (4) increase in the length of the first wing phalanx to be the longest of the four phalanges, (5) increase in the length of the wing metacarpal, (6) increase in the size of the prepubes, (7) reduction of the fifth toe, and (8) reduction and simplification of the tail. Reconstructions modified from Unwin,15 Wellnhofer,16 and Witton.1 These are not to scale but are all set to a uniform torso length.
See also Figures S1S8 and S11 and Table S1.
As Though to rub salt into creationist wounds, not only is this pterosaur from the Lower Tithonian (i.e. 148-150.8 million years old) but as the palaeontologist explain, it forms part of a transitional sequence of fossils showing how this group of reptiles evolved.

Thursday, 26 September 2024

Refuting Creationism - More Detail on The Evolution of the Mamalian Jaw and Middle Ear Bones - 17 Million Years before 'Creation Week'


Riograndia and Brasilodon
Jorge Blanco
September: Brazilian fossils | News and features | University of Bristol

As I confidently predicted in the conclusion to my last blog post, that might have been that day's casual refutation of creationism, but another would be along shortly.

Of course, I can't claim any credit for such an easy prediction because refutations of creationism are ten-a-penny in scientific literature, occurring often multiple times a day, simply by revealing facts that run counter to creationist claims.

This particular refutation deals with the discovery that the precursor to the mammalian jaw joint and middle ear bones occurred several times with this particular one appearing in the fossil record about 17 million years ago. The mammalian middle ear bones or ossicles are a modification of the reptilian jaw and the single reptilian middle ear bone.

Sunday, 11 August 2024

Refuting Creationism - Early Mammals Lived Longer 200-150 Million Years Before 'Creation Week'


Artist’s impression of Dryolestes on a stegosaur tail spike.
Early Mammals Lived Longer — University of Bonn

New technology has enabled a team of scientists to examine in microscopic detail, the growth rings in the root cement of the fossilised teeth of early mammals, and to make a surprising discovery - the earliest mammals lived considerably longer than equivalent-sized mammals do today, but they took longer to reach sexual maturity.

These growth rings are like those of trees and record the annual growth of the mammal. They can be seen using a technique called synchrotron X-ray tomography in which electrons are accelerated to near light-speed. This means that like x-rays they can penetrate solid objects such as fossils and bone, which do not need to be cut into thin slices, and like an electron microscope, because electrons have such short wave-lengths, they can resolve much finer structures, hence these microscopic growth rings become visible.

Thursday, 23 May 2024

Creationism in Crisis - How Dinosaurs Evolved Feathers


Latest News and Views from University College Cork

Psittacorus (reconstruction)
Artwork by Walter Myers
This paper is enough to send a dedicated creationist disinformation specialist into intellectual summersaults. On the one hand, they hate the fact that dinosaurs lived so long ago and are evidence of life on earth tens and hundreds of millions of years ago, so they bend over backwards to prove they were around just a few thousand years ago, and then, horror of horrors, along come some clever scientists and show evidence that some dinosaurs even evolved into birds!

And now, courtesy of Palaeontologists at University College Cork (UCC) in Ireland , we have evidence of the transition from scales to feathers in pre-avian dinosaurs.


But it gets even worse! Creationists frauds have ben claiming for several years now that 'fossilised' soft dinosaur tissues prove they were just a few thousand years old because, despite the perfectly rational explanation of how 'soft' tissues can be preserved for many millions of years in the right circumstances, like the presence of iron, the evidence of this transition from scales to feathers would found in fossilised soft tissue!

So, a creationist disinformation specialist must now argue that fossilised dinosaur soft tissues don't exist, and when they do, they prove dinosaurs lived recently. One problem they face is that the fossilised skin isn't skin at all, or even the fibrous protein parts of skin; it has been entirely mineralised aa silicate, preserving only the morphology, including the surface patterning - which is where the evidence lies.

The University College Cork scientists have just published their findings, open access, in Nature Communications and in a UCC news release:
Web Analytics