Miscellaneous Notes
February 20, 2023: from Brusatte, key: pelycosaur --> therapsid --> cynodont --> true mammal.
February 19, 2023: recently bought and read The Rise and Reign of the Mammals: A New History From the Shadow of the dinosaurs to Us, Steve Brusatte, c. 2022.
- new: new term in Brusatte's book: pelycosaur. The mammal-reptile split, though that word as a formal term is already losing favor
- cynodont: still the term used for the proto- / ur- mammal.
Splits
as you go through the Dingus and Rowe book below, it seems at ever split --
the split
two sister lineages
one small, inconsequential lineage
side-by-side with the very large sister, very consequential lineage
so, abbreviated
start with veretebrate phylogeny
gnathostomata (all the rest) -- petromyzontida (parasitic lampreys)
jaws lined with teeth inconsequential
osteeichthyes (all the rest) -- chondrichthyes
increased bone density sharks and rays
new anatomy lost virtually all bone
inconsequential
sarcopterygii ---------------------- actinopterygian
the humerus appeared 18,000 species; all ray-finned fishes
then radius, ulna
birds, dinosaurs, humans -- that forearm
choanata ---------------------------------- actinista
20,000 living species a single species deep in ocean
continuous passage from around the Comoros Islands in the Indian Ocean
the nose to the roof of the
mouth known as the choana
350 million years ago
Tetrapoda moved unto land. ---------------Dipnoi
fins to limbs three living species of lungfish, freshwater Africa,
added a series of South America, Australia
interlocking bones that
form the wrists and the ankles
Two major lineages survive today but one is inconsequential
Amniota --------------------------------Amphibia
frogs, salamanders, caecilians (evolution: reduction of limbs
--> total loss of limbs)
frogs: highly evolved
Amniota
Synapsida -------------------Reptilia (diapsids)
humans and
all mammals
Here, a bit different -- we look at the more inconsequential lineage, the Reptilia
Reptilia
Sauria ---- dinosaurs (not lizards) ------------------ Testidines (turtles)
teeth replaced with a beak
primitive birds and primitive turtles: teeth
converged evolution: lots of teeth
Sauria ---------------------------------------dinosauria
lizards, snakes, crocodiles, birds not lizards
Archosauria:
250 mya
25 my before oldest known dinosaur
From Robert Broom's Euparkeria.
Dinosauria
Birds --- Crocodilians -- dinosaurs -- pterosaurs (not dinosaurs)
birds not part of crocodylian hieerarchy
Sauria
Archosauria ----------------Euparkeria: extinct
both: Archosauriformes
CRITICAL
BIRDS
Arcchosauriformes or Thecodont
CRITICAL
Archosauriformas --> ornithodira (experimented with bipedality) -->
pterosauria ---- dinosaurs and birds -- flight arose independently
Dinosauromorpha: bipedal running
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The Original Notes and Updated Notes From The Book
Part I: The Search for the Smoking Gun
Chapter One: The Seductive Allure of Dinosaurs
Chapter Two: Earlier Extinction Hypotheses
Chapter Three: Contrasting Volcanic and Impact Hypotheses
Chapter Four: Enormous Eruptions and Disappearing Seaways
Chapter Five: The Fatal Impact
Page 47: "In both marine and terrestrial rock layers, or sequences, many of the plants and animals that became extinct at or near the end of the Age of Dinosaurs drop out of hte record abruptly as one moves from lower, older rocks documenting the end of the Age of Dinosaurs up into higher, younger rocks representing the beginning of the Age of Mammals. Such an abrupt disappearance of many forms of single-celled plankton in the marine limestones near Bubbio, Italy, led Walter Alvarez and his colleagues to wonder how long these extinctions really took.
"Between the white limestone representing the end of the Age of Dinosaurs and the pink limestore representing the start of the Age of Mammals lies a three-eighths of an inch thick (1 cm thick) bed of clay. Alvarez discussed this problem with his father (Nobel-laureate physicist, Luis Alvarez) and several of his father's associates. In the end, they felt that they might get some idea of how long it took to deposit this layer of clay by looking at the concentration of an element called iridium. Iridium (Ir) is one of the platinum group elements and has an atomic number of 77."Chapter Six: Direct Evidence of Catastrophe
"Throughout the 1980s, the proponents of the impact scenario searched feverishly through geologic data and satellite imagery for the "smoking gun," or, more appropriately, for traces of the "festering wound" inflicted on the Earth's crust by such an impact.
"The Earth has long been bombarded by extraterrestrial objects. Although the rate of impacts appears to have decreased in the last 4.5 billion years since the year first formed, extraterrestrial objects (large enough to pass through the atmosphere without burning up) continue to hit the earth with tremendous force. ... Estimates of the frequency of crater impact suggest that a meteor large enough to leave a crater 6 miles across hits the Earth about once every 100,000 years." -- pp. 67 - 68.
"Another serious candidate was actually discovered as the result of exploration for oil in 1981. However, little attention was paid to the announcement by Glen Penfield and his colleagues because it was before the search for the K-T impact crater had actually begun. In an ironic twist of fate, most of the drilling-core samples that documented the geologic evidence at this site were destroyed by a fire in the warehouse where they were stored. Consequently, the crater's possible existence and relationship to the scenarios involving the K-T extinctions only came to light in the early 1990s. Studies...the site is located near the town of Chicxulub. It lies partly on the northwest corner of the Yucatan Peninsula and extends into the adjacent Gulf of Mexico." -- p. 69
Chapter Seven: Patterns of Extinction and Survival
Chapter Eight: Our Hazy View of Time at the K-T Boundary
Chapter Nine: Living Dinosaurs
Archosauria: "ruling reptiles"Chapter Ten: Dinosaurs Challenge Evolution
dinosaurs
crocodylians
pterosaurs
siblings
"Although the common ancestry of birds and archosaurs was acknowledged, birds were placed in a totally separate class -- Aves -- to signify that, by evolving feathers, flight, and warm-bloodedness, they had traveled across a far greater distance of evolutionary change than the others." -- p. 111
But, to which class, were birds most likely to have evolved from, dinosaurs, crocodilians, or pterosaurs?
Realizing that wings and three-toed feet represented convergent evolution (not lineage) solved many of the problems.
"Euparkeria" -- the primal archosaur, discovered in South Africa, 1910. "Euparkeria" long reigned as the most important discovery of the 20th century in terms of archosaur evolution and the origin of birds. Most students have since been taught that an ancestor such as "Euparkeria," over the vastness of Mesozoic time, birds, crocodilians, pterosaurs, and dinosaurs slowly, independently, and divergently evolved.
Huge gap between "Euparkeria" and the youngest known bird ("Archaeopteryx"?) is 100 million years. What lay between?
"Deinos" Greek for "terrible"
"onxy" Greek for "claw, talon"
If birds evolved from Deinonychus, birds evolved from the "ground up," not from the "tree down." Very, very surprising; hard to explain.
John Ostrom led the debate, favoring the "ground up" theory.
Ostrom began by comparing the oldest known bird, "Archaeopteryx lithographica," with "Deinonychus."
Seven specimens of "Archaeopteryx": one in London, four in Germany, one in the Netherlands; the 7th has vanished.
The "Archaeopteryx" fossil discovered in southern Germany, near Solnhofen, exactly where the technique of lithography was invented in the 18th century. Discovery of the "Archaeopteryx" fossil occurred two years after Darwin's "Origin of the Species" and near the peak of demand for lithography stones. Workers inspected untold thousands of Solnhofen slabs, finding eight specimens of "Archaeopteryx."
"archaios" -- "ancient"
"pteryx" -- "wing"
There are currently eight known "Archaeopteryx" fossils, though the 7th has vanished; the 8th was discovered in 1992. All have been discovered in the same quarry near Solnhofen, Germany. Experts assume a new "Archaeopteryx" will be discovered every decade or so.
Chapter Eleven: Dinosaurs and the Hierarchy of Life
Chapter Twelve: The Evolutionary Map for Dinosaurs
Chapter Thirteen: Death by Decree
Chapter Fourteen: The Road to Jurassic Park
Chapter Fifteen: Crossing the Boundary
Chapter Sixteen: Diversification and Decline
Chapter Seventeen: The Real Great Dinosaur Extinction
Chapter Eighteen: The Third Wave
Epilogue
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