#503 In the studio: Birds . . . evolution and anatomy

BIRD EVOLUTION AND ANATOMY

Birds appeared more than 150 million years ago, during the Jurassic or possibly the Triassic period.
The recent discovery of vast beds of fossil birds and "feathered dinosaurs"  in deposits in northeast China
and central Asia has opened argument about whether birds descended from dinosaurs or earlier
 archosaurs but also clarified an ongoing question:  Birds and two-legged creatures such as
the carnivore, Tyannosaurus rex, are on the same branch of the evolutionary tree.

The earliest known bird was the Archaeopteryz - pronounced arky-OP-tuh-ricks - the word means "ancient wing" in Greek.  A fossil discovered in Bavaria in 1861 shows that the creature who grew to the size of a crow, had feathers, claws, and other features that scientists think is the link to modern birds.   Six specimens of "arky" have been found . . .
all in limestones in southern Germany and all dated between 200 and 140 million years ago.

Below, is a photo of Archaeopteryz . . . "arky" for short.

Although "arky" had many unmistakable bird features, much of its skeleton is akin to those of reptiles.
Scientists think a bird's scaly legs are the last reminders of a reptilian ancestor and that feathers originated as
reptilian scales . . . feathers are made from the same horny substance of which fingernails are made.   

Feathers - not flight - set birds apart from other animals. . . many species, such as ostrich, have evolved with an inability to fly.  The evolution of powered flight required major skeletal modifications to change its early gliding wing movement to flapping flight.  The small,  two-legged, carnivorous dinosaur designed for a life of gliding from tree to tree in a gloomy Jurassic jungle evolved into today's modern bird and Archaeopteryz is the missing link.

Most, but not all birds fly.  The bones are light but remarkably strong, and some contain air sacs connected to the lungs.  Below, is a drawing of a bird skeleton and illustrates a number of modifications that make flight possible.
(1): Heavy teeth have been replaced by a light bill

(2): The bones of the skull are thin.

(3) and (4): The bones of the wings and legs are composed of thin-walled, honey-combed  tubes.
Nature has sluffed off weight to enable flight.

Although the information presented in this post is current . . .  as new discoveries are made,

both in the field and with DNA, scientists will continue to fine-tune,
fill in the details, provide a more complete picture, and debate the evolution of birds.

The fact remains that "arky" was unique for it possessed feathers.
The development of feathers was one of the crucial steps in the evolution of birds.


Blog, text, photos, drawings, and sculpture . . . © Sandy Scott and Trish Smith

   

#416 In the studio: Bird anatomy, con't . . .

Please start this bird anatomy series with post #403, March 10.

Most birds are designed for flight and flying demands a rigid airframe.   The bird's rib cage and backbone are fused together . . . only the neck, tail, and wings are flexible.  The spine of mammals - human and quadruped - is supple.  A bird's spine is rigid . . . 
if it were supple, the bird would lose control and could not fly. 

The bird's bones are hollow, light, and remarkably strong.  For instance, a pelican weighs twenty pounds and the skeleton weighs only twenty-three ounces.  Nature has sluffed off weight to enable flight.  

The skeleton of a bird can be summarized as follows:  
    
    1 - the skull, made up of fused bones  
    2 - the vertebral column; includes 13-25 neck vertebra, fused backbone vertebra, flexible tail vertebra   
    3 - the hip girdle which provides support for the legs and where the leg muscles attach  
    4 - the pygostyle, where the tail feathers attach  
    5 - the sternum or keel, which anchors the wing pectoral muscles of flying birds  
    6 - the wing, includes the humerus, radius/ulna, and hand which anchors the primary flight feathers  
    7 - the leg - includes the femur, tibia, tarsus, and toes  
    8 - the clavicle or wishbone, which keeps the wing joint and coracoid in position as the wing muscles 
         pull downward.

A bird's entire body, except is bill and feet, is usually covered with feathers.  Why is the skeleton important to the bird sculptor?  The bird sculptor must know how the bones are arranged, how they articulate, and the limitations of skeletal movement before attempting to define muscles and feather groups.  

Copyright - Sandy Scott

Below is an etching entitled Dominick - copyright Sandy Scott
The underlying skeleton can be seen above and is also illustrated in post #410

#415 In the studio: Bird anatomy, con't . . .

Please start this bird anatomy series with post #403, March 10.

Like humans and quadrupeds, birds are vertebrates . . . meaning they have a backbone.  Nature has designed just one pattern for all vertebrate mammals.  All mammals, humans, horses, dogs, bears, deer, cats, and interestingly, even giraffes have 7 neck vertebrae.  Birds, on the other hand, have a very flexible neck consisting of 13 - 25 neck vertebrae.

At the other end of the spinal column, humans have a coccyx, mammals have a tail, and birds have a pygostyle.  During the course of evolution, birds have gradually lost the part of the backbone that makes up the tail . . . the tail has been replaced by feathers that are attached to the pygostyle, which is actually a bone structure covered with muscle and flesh.  Look at the supermarket chicken on the right and you will see the pygostyle . . . colloquially known as the "pope's nose."  Upon examining the pygostyle, you will notice the holes on the fleshy shape where the tail feathers emerge and fan out.

Why is this important to the bird artist?   The bird artist must know how the skeleton is arranged, 

how it articulates, and where the tail feather group originates.

Comparison of vertebrates . . . human and quadruped above and bird below

Concept, after Elliot Goldfinger.

Copyright - Sandy Scott

Below is a drawing of a wild turkey.  The magnificent bird has 18 long, stiff tail feathers and a gobbler in full display, 

with tail feathers fanned, is one of nature's most exquisite visual gifts.

Copyright - Sandy Scott

#216 In the field: Brookgreen Gardens Workshop, con't . . .

The bird sculptor must know and understand bird anatomy and how a bird is structured.

Birds, like mammals (including humans) are vertebrates.  

Vertebrates simply means that the animal has a backbone.  

Nature has designed just one basic pattern, with many variations, for all vertebrates.  

The skeleton of the bird's wing is more easily understood when compared to the human arm. 

Comparison between human arm above and bird wing below

Wing drawings, copyright Sandy Scott, from the book Spirit of the Wild Things - The Art of Sandy Scott

sandyscott.com/sandyscottbronzh.html

#213 In the field: Brookgreen Gardens Workshop

Portable clay warming device:
heat lamp and bucket 

Monday morning was the first day of my 3-day 2012  Brookgreen Gardens Bird Anatomy and Sculpture Workshop.  For information about Brookgreen Gardens please refer to brookgreen.org and brookgreenworkshops.com

Teaching bird anatomy and sculpture is a personal discipline and has been rewarding
over the years in that I continue to explore, learn and stay in touch with the basics.
This afternoon will end a 3-day information packed introduction to bird sculpture,
and the 4 "A's":  anatomy, aerodynamics, armature building, and art.

Workshops provide continuing education for adults and an opportunity to learn from a working, professional artist/instructor.  I enjoy working with students of all levels of proficiency; particularly beginners and painters.  We focus on birds in flight  and my teaching method is structured and methodical . . . a step by step "follow me" approach.

For more information about my workshops please refer to Blogs #140 - #145, January 21 - 27, 2012. 

Students  participating in a group critique of  a Common Tern clay block-in sculpture