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Age of Animals


Jurassic Period, 201.3 - 145.0 MYA, 2025 Update

Jurassic Period
  • Dinosaurs became dominant, reaching their largest size. The brontosaurus (thunder lizard) was a huge sauropod with length up to 80 feet and a total weight of 30 to 35 tons (see the gigantic beast in Figure 08a). The large size probably helped them to escape predation by carnivorous dinosaurs. In the same picture, the stegosaur protected itself by the elaborate armour. Its small brain was compensated by large ganglia (a mass of never cells) between the shoulders and another one above the hips; those are sometimes referred to as the second brain.
  • The dinosaurs also diversified into water and air - Kuehneosaurus were the gliding reptile, pterosaurs were the flying one, while nothosaurs and ichthyosaurs returned to sea.
  • FA of birds - Archaeopteryx (ancient wing) is the oldest known creature that had feathers. Except for the feathers and the braincase, this crow-sized extinct animal is much more like a small running dinosaur.

Figure 08a Jurassic Period

See 2025 conversation with ChatGPT (in Italic text) about the 1993 film "Jurassic Park"

Feather It was believed that feathers evolved from scale for flight. New evidence from fossils and recent idea in developmental processes indicate that they evolved for some other purpose and were then exploited for a different use. Numerous functions of feathers are plausible, including insulation, water repellency, court-ship, camouflage and defense. The development of such feature can be traced back to the theropods in the Triassic Period. In essence, all feathers start from a tube produced by proliferating epidermis with the nourishing dermal pulp in the center. The evolution involved many

Figure 08b Feathers
[view large image]

stages from an unbranched, hollow cylinder (like the pinfeather) to the asymmetrical flight feather (see Figure 08b).

Avian Evolution Archaeopteryx Characteristics The consequence of recent fossil finds has prompted reconsideration of the biology and life history of the theropod dinosaurs. Birds - modern birds and the group that includes all species descnded from the most recent common ancestor of Archaeopteryx - used to be recongnized as the flying, feathered vertebrates. Now we have to consider them as a group of the feathered theropod dinosaurs that evolved the capacity of powered flight (Figure 08c). Other dinosaurs are very likely to have had feathered skin but were not birds.

Figure 08c Avian Evolution [view large image]

Figure 08d Archaeopteryx Traits [view large image]


For many years the earliest bird fossil has been the Archaeopteryx lithographica, which lived in the Late Jurassic period about 148 MYA. Figure 08d shows the characteristics of the Archaeopteryx. It indicates that Archaeopteryx is at the transitional stage between reptile and bird. The size
Archaeopteryx Huxleyi of Archaeopteryx is about 45 cm, and it fed on insects. It has a long bony tail, three-fingered hands with claws, and jaws with teeth. The claws on its feet and hands suggest that Archaeopteryx could climb trees, and the wings are clearly those of an active flying animal. This bird could fly as well as most modern birds, and flying allowed it to catch prey that were not available to land-living relatives. In effect, it had explored a niche in the air. Figure 08e shows the first Archaeopteryx fossil from Bavaria, southern Germany, and an artist's renderings of the very first birds.

Figure 08e Archaeopteryx and Fossil [view large image]

Figure 08f Oldest Feathered Dinosaur [view large image]


It was only in the 1990's, when more evidences turned up in fossil-rich quarries in northern China. Various dinosaur fossils clearly show fully modern feathers and a variety of primitive feather structures. The dromaeosaurs discovered at Liaoning seems to represent the theropods that are hypothesized to be most closely related to birds but that clearly are not birds. It may be the missing link depicted in Figure 08c. Then a four-winged dinosaur fossil (Figure 08f) was discovered in 2009, the Anchiornis Huxleyi is dated to 151-161 million years ago making it the oldest feathered dinosaur. It has the size of a chicken (less than 50 cm) with long feathers covering the arms and tail, but also the feet. Figure 08g shows some locations of dinosaur fossils in China.

Figure 08h1 shows the 2014 status of ancient birds. The archaeopteryx is no longer the oldest one, the title has gone to the Aurornis Xui which existed about 10 million years earlier. The bird brains are not so small in comparison to their size, and the feathers are used to keep warm initially rather than for flying.

Dinosaurs in China Old Birds Evolution of Birds Figure 08h2 is a 2017 update from Scientific American. It shows the family tree starting from the archosauria about 250 MYA at the beginning of Triassic. Most of the animals in the top food chain perished at the end of Cretaceous period when an asteroid strike causing catastrophic extinction of dinosaurs leaving a few surviving groups including birds and small mammals (see "K-T Extinction")

Figure 08g Dinosaurs in China [view large image]

Figure 08h1 Old Birds [view large image]

Figure 08h2 Evolution of Birds [view large image]


Here is the references from Wikipedia for members in the clade of Archosauria (see Figure 08h2) : Dinosauria, Saurischia, Theropoda, Maniraptora, Paraves, Avialae (birds), Pygostylia, Ornithothoraces, Ornithurae. These references contain lot of information on the dinosaurs and their bird-like relatives although the groupings and namings become confusing at times.

As shown sequentially from right to left in Figure 08i, early chick embryo starts with all 5 digits, then the 1st and the 5th become vestigial, eventually the 2nd, 3rd, and 4th digits emerge together to form the wing. A controversy has developed for more than a century over the
Digits of Bird and Dinosaur relationship between the wing of birds and the digits in theropod dinosaurs when palaeontologists mistakenly identified the dinosaurs' to be the 1st, 2nd, and 3rd. Until now in 2009, analysis of the digits in a Limusaurus fossil shows that those are indeed the 2nd, 3rd, and 4th digits - the same as the modern birds (Diagram d, Figure 08i). This explanation vastly simplifies the current convoluted evolutionary story which, either assumes that birds lost their 1st digit and re-grew their 4th one or that birds descend from another kind of dinosaurs.

Figure 08i Digits of Bird and Dinosaur [view large image]


Meanwhile, the lizard ancestor evolved into an entirely different form as snake (Figure 07i). Evolution of venom was thought to occur around 60 million years ago. It was assumed that venom has evolved independently in each of the three modern families -
Snakes Viperidae (vipers), Elapidae (cobras and coral snakes), and Atractaspididae (stiletto snakes). New research in 2006 suggests that venom evolved in a lizard ancestor before snakes appeared (Figure 08j). Even the supposedly harmless Colubrids such as those sold in pet stores have enough poison in their venom glands to kill a human. Fortunately for the would-be pet owners, they have no front fangs, leaving them with a rather crude venom-delivery system in the back teeth. Snakes such as boas may have lost their venom as they evolved to kill by constriction. It is also found that venom didn't evolve from ever more toxic saliva but from altering cells from other parts of the body including the brain, eye, lung, heart liver, muscle, ovary and testis. Over generations these proteins, usually involved in key biological processes such as blood clotting or regulating blood pressure, were mutated into more potent varieties and concentrated into catastrophic overdoses. The common ancestor had nine such toxins in its venom. Modern snakes have recruited 17 more.

Figure 08j Snakes [view large image]

Half Snake Report in 2007 purported to find the missing link between lizards and snakes. The 95 million years old fossil has greatly reduced forelimbs, a diminished supporting skeletal girdle and an elongated neck (see Figure 08k), as seen today in snakes including pythons and boas. But researchers still cannot conclude that snakes evolved directly

Figure 08k Half Snake [view large image]

from such lizards without other fossils to fill the evolutionary gaps.

A 2014 update on the evolution of snake indicates that losing their legs was the least of the amazing modifications. The major change is on the metabolism. After a big meal, there is a huge change in the mass and size of the internal organs as well as soaring in metabolic rate (see Figure 08l in time scale of 10 days, deeper colors indicate the changes). Actually, they lay dormant between meals (within 2 weeks) keeping the metabolic rate the lowest level known in any vertebrate. It seems that they evolved about 100 million years ago as burrowing lizards. Thus they lost their eyes and recovered part of it when moved back to the surface. They are still having problems in the eyes with blood vessels running in front of the retina and the fused (but transparent) eye lids. They may have poorer eyesight but they can "see" in the infrared (with special heat-
Snake Evolution sensing pits on their faces) and are able to trace scent of the venom left by the bitten preys. To swallow the prey much larger than their head, they developed unusually folded skin around the mouth as well as very flexible jaw muscles. Sometimes the venom serves another function of breaking down the prey's tissues before swallowing it. Study of the 2 genomes sequences belonging to the Burmese python and the king cobra (inserts in Figure 08l) shows that only a few hundred genes among the 7442 genes common to all land vertebrates had been modified. The venom genes have been assembled from 20 families of genes, which had day-to-day housekeeping functions within the cells.

Figure 08l Snake Evolution
[view large image]

The leg genes are still active in the embryos, but the cells in these areas just ignore the signal, so no legs form. They have also eliminated one lung and retained only one lobe of the liver.

Snake, ZRS Gene A research paper published in November 2016 reveals that mutation or loss of the ZRS gene is responsible for the loss of limbs in snakes. It is an enhancer for promoting the transcription of the Shh gene, which regulates limb formation (Figure 08m,b). Such effect is demonstrated by coloring the ZRS proteins blue and watching the development of blue patches in the back of their small budding limbs at day 11.5 (E11.5, Figure 08m,a,f) in embryos of various animals. It is also found that the basal snakes such as boa and python still retain pair of vestigial hindlimbs because they evolved earlier, while the corn snakes such as cobra forgo the limbs completely (Figure 08m,c).

Figure 08m Snake, ZRS Gene Mutation or Loss [view large image]


The effect is confirmed by replacing the ZRS gene in mouse embryos with the snake version to produce legless mouse (Figure 08m,d). The other way is to restore legs to snake by replacing the its ZRS gene with the non-snake version (Figure 08m,e).

The study becomes feasible only with the new gene editing technique of CRISPR, which reduces years of work to just a few months. See a news article on "What a Legless Mouse Tells Us About Snake Evolution".

[2025 Update]



Is the science of dinosaurs presented correctly In the movie Jurassic Park?

ChatGPT said:
The science of dinosaurs in Jurassic Park (1993) is a fascinating mix of accurate concepts, speculative ideas, and outright errors, reflecting the state of paleontological knowledge and artistic liberties at the time. Here's an evaluation of how the movie measures up to modern science:
________________________________________
What Jurassic Park Gets Right
1. Dinosaurs and Birds Connection:
o The movie highlights that dinosaurs are closely related to birds, particularly through Dr. Alan Grant's discussions about Velociraptors and avian behaviors.
o This idea was groundbreaking in the early 1990s and is now widely accepted in paleontology.
2. Cloning Dinosaurs from Ancient DNA:
o The concept of extracting DNA from amber-preserved mosquitoes is creative and grounded in the basic principles of molecular biology. While it's speculative, it introduced audiences to the potential of genetic engineering.
3. Behavior and Intelligence:
o The portrayal of Velociraptors as highly intelligent hunters, coordinating in packs, aligns with the idea that some theropods may have exhibited complex behaviors.
4. Realistic Dinosaur Anatomy (for the time):
o The use of animatronics and CGI to depict dinosaurs was revolutionary, and their anatomy was based on then-current fossil reconstructions.
________________________________________
What Jurassic Park Gets Wrong
1. Velociraptor Size and Appearance:
o The movie's "Velociraptors" are much larger than the actual Velociraptor species (about the size of a turkey). They more closely resemble Deinonychus, a larger dromaeosaurid.
o The movie's raptors lack feathers, which we now know most dromaeosaurs likely had.
2. Tyrannosaurus Rex Vision:
o The claim that a T. rex's vision is based on movement is incorrect. Fossil evidence suggests T. rex had excellent vision, with forward-facing eyes providing depth perception.
3. Cloning Feasibility:
o DNA degrades over time, and the half-life of DNA suggests it would be highly unlikely to find intact dinosaur DNA after tens of millions of years.
o Even if DNA were recoverable, assembling a complete genome and overcoming epigenetic and developmental challenges remains beyond our capabilities.
4. Behavioral Speculation:
o The depiction of dinosaurs behaving like modern animals (e.g., raptors opening doors or T. rex engaging in a specific type of predatory behavior) is speculative and dramatized for entertainment.
5. Dilophosaurus Inaccuracies: o The movie's depiction of Dilophosaurus as a small, venom-spitting dinosaur with a frill is entirely fictional. Real Dilophosaurus was much larger and lacked evidence for these traits. 6. Genetic Reconstruction:
o The inclusion of frog DNA to fill gaps in the dinosaurs' genome is a plausible-sounding plot device but biologically improbable. It would likely cause severe developmental anomalies.
________________________________________
Science Has Advanced Since 1993
Many of the inaccuracies in Jurassic Park are due to the limitations of scientific knowledge at the time. Since then, discoveries have painted a more complex picture of dinosaur biology, including:
" The prevalence of feathers in theropods.
" Insights into dinosaur metabolism, suggesting many were warm-blooded.
" Advances in genetic science that clarify the limits of ancient DNA recovery.
________________________________________
Conclusion
Jurassic Park effectively introduced paleontology and genetic engineering to a global audience, sparking interest and debate. While it takes liberties with science for storytelling, many inaccuracies are forgivable given its pioneering role in pop culture. It remains a classic example of how fiction can inspire scientific curiosity.

Is it suitable to introduce the film to primary school students (ages of 5 to 12) ?

ChatGPT said:
Introducing Jurassic Park to primary school students can be a fun and engaging way to spark their interest in dinosaurs, science, and the natural world, but several factors should be considered to determine its suitability for this age group.
________________________________________
Pros of Introducing the Film to Primary School Students
1. Engagement with Science and Dinosaurs:
o The film can excite kids about dinosaurs, paleontology, and genetic science, fostering curiosity and discussions about Earth's history.
2. Opportunities for Critical Thinking:
o It provides a chance to discuss what's real and what's fictional, encouraging students to critically evaluate information and learn about scientific accuracy.
3. Cinematic Masterpiece:
o The visuals and storytelling are captivating, which can inspire creativity and a love for movies as a form of art and education.
4. Themes of Ethics and Responsibility:
o The movie introduces ethical issues related to science and technology, which can be simplified for young learners as "just because we can, should we?"
________________________________________
Cons and Potential Issues
1. Intense Scenes and Violence:
o The film contains graphic scenes of dinosaurs attacking humans and each other, which might be frightening for younger viewers.
o Examples: The T. rex attack on the cars, the Velociraptor scenes in the kitchen, and the death of some characters.
2. Mature Themes:
o The ethical and scientific dilemmas might go over the heads of younger children, or they may misinterpret the consequences of scientific innovation.
3. Accuracy Concerns:
o Without proper guidance, students might take the fictional aspects of the film as fact, leading to misconceptions about dinosaurs and science.
4. Parental Concerns:
o Some parents might object to exposing their children to a PG-13 film due to violence, intensity, or other content.
________________________________________
How to Make It Suitable for Primary School Students
1. Watch Select Scenes:
o Choose less intense and more educational scenes to show (e.g., the dinosaur tour, the hatching of the baby dinosaur, and the explanations of cloning technology).
o Skip scenes with graphic violence or frightening moments.
2. Prepare Context:
o Before watching, explain that the movie is fiction and point out that not all details are scientifically accurate.
o Introduce real facts about dinosaurs to complement what they see.
3. Follow-Up Discussions:
o Discuss the science of dinosaurs, the ethical implications of cloning, and how movies use artistic license for entertainment.
o Compare the movie dinosaurs to what scientists know today (e.g., feathers, behaviors).
4. Offer Alternatives:
o If the intensity of Jurassic Park feels too advanced, consider other dinosaur-themed educational programs or books, like Dinosaur Train or Walking with Dinosaurs, which are more age-appropriate.
________________________________________

Conclusion
While Jurassic Park can be a thrilling introduction to dinosaurs and science, its PG-13 rating, intense scenes, and mature themes require careful consideration. Tailoring the experience with selected clips and guided discussions can make it a more suitable and enriching activity for primary school students.



The film also misses the dinosaurs' evolution, how they dominated the world, and their extinction.

ChatGPT said:
You're absolutely right-Jurassic Park largely skips over the broader story of dinosaurs' evolution, their dominance during the Mesozoic Era, and their eventual extinction. These omissions are significant if the goal is to provide a comprehensive understanding of dinosaurs' history and their role in Earth's evolutionary story. Here's how the film falls short in these areas and why these topics are essential for primary school students:
________________________________________
What the Film Misses
1. Dinosaur Evolution:
o Jurassic Park focuses on cloning specific dinosaurs but doesn't explain how they evolved from earlier reptiles during the Triassic Period (approximately 230 million years ago).
o It doesn't mention the gradual diversification of dinosaurs into distinct groups like theropods, sauropodomorphs, and ornithischians.
2. Dinosaurs' Dominance:
o The film portrays dinosaurs as isolated creatures but doesn't showcase how they dominated ecosystems for over 160 million years, becoming some of the most successful land animals in Earth's history.
o There's no exploration of their adaptations, such as their varied diets, unique locomotion, and reproductive strategies.
3. Mass Extinction:
o The extinction event that ended the reign of dinosaurs 66 million years ago-likely caused by an asteroid impact and its aftermath-is barely mentioned.
o This extinction is a pivotal story in Earth's history, marking the transition from the Age of Dinosaurs to the Age of Mammals.

See a 36 mins video on "Dino-extinction"
4. Dinosaurs' Legacy:
o While the film briefly mentions the connection between dinosaurs and birds, it doesn't delve into how many theropod dinosaurs gave rise to modern birds, representing an evolutionary success story.
________________________________________
Why These Topics Matter for Students
1. Understanding Evolution:
o Explaining how dinosaurs evolved from early reptiles helps students grasp the basics of evolution, adaptation, and natural selection.
2. Ecosystem Roles:
o Highlighting the diversity of dinosaurs (e.g., herbivores, carnivores, and omnivores) shows how they fit into ancient ecosystems and interacted with other organisms.
3. The Impact of Extinction:
o Learning about the mass extinction event emphasizes the fragility of life on Earth and introduces concepts like climate change and ecological disruption.
4. Connecting Past to Present:
o The idea that birds are living dinosaurs bridges the past with the present, making dinosaurs feel more relatable and real to students.
________________________________________
How to Address These Gaps
1. Pre-Watch Discussions:
o Provide a brief overview of the Mesozoic Era (Triassic, Jurassic, and Cretaceous periods) and key evolutionary milestones before watching the film.
2. Post-Watch Activities:
o Use the movie as a springboard to discuss the broader history of dinosaurs.
o Show educational videos or documentaries that cover these topics, like Prehistoric Planet or Walking with Dinosaurs.
3. Interactive Learning:
o Introduce hands-on activities like creating a timeline of dinosaur evolution, drawing different dinosaur species, or modeling the asteroid impact and its effects.
4. Tie-In Resources:
o Use books or museum visits to fill in the gaps about dinosaur evolution, ecosystems, and extinction.
________________________________________

Conclusion
While Jurassic Park is an exciting movie, it only scratches the surface of the rich history of dinosaurs. Educators or parents should supplement the film with additional materials to provide a fuller picture of how dinosaurs evolved, thrived, and disappeared-helping students appreciate the awe-inspiring story of life on Earth.

[End of 2025 Update]

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