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Information about Egg Tooth

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A Senegal Parrot chick at about 2 wks from hatching. The egg tooth is near to the tip of its beak on the upper mandible.
An egg tooth is a small protuberance on the beak or nose of vertebrates that are hatched from eggs, i.e., birds and reptiles. Some lizards and snakes develop a true tooth that is shed after use; birds and other reptiles generally develop an analogous epidermal horn that is reabsorbed or falls off. Both varieties of egg tooth assist in the breaking or tearing of the eggshell, a process known as pipping.

Birds

Baby birds have a pipping muscle on the back of their necks. It is this muscle which gives them the strength to force the egg tooth through the inner membrane of the eggshell.

When a baby bird becomes too large to absorb oxygen through the pores of its eggshell, it uses its egg tooth to peck a hole in the air sac located at the flat end of the egg. This sac provides about a few hours' worth of air, during which the baby bird breaks through the eggshell to the outside. The egg tooth falls off several weeks after hatching.

Reptiles

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Borneo Short-tailed Python, Python breitensteini hatching, egg tooth visible
Baby snakes generally hatch from eggs with tough, leathery shells. A baby snake's egg tooth tears a hole directly through the shell, and falls off the first time the snake sheds its skin. Lizards have similarly leathery eggshells.

A baby crocodile has an egg tooth on the end of its snout. It is a tough piece of skin which is totally reabsorbed less than two months after hatching. Crocodile eggs are similar to those of birds in that they have an inner membrane and an outer one. The egg tooth is used to tear open the inner membrane; the baby crocodile can then push its way through the outer shell. If conditions are particularly dry that year, the inner membrane may be too tough for the crocodile to break through, and without assistance it will simply die inside the egg. Generally, however, the mother crocodile is there to help free it.

Development of the Egg Tooth

A 121 million year old fossilized egg, complete with well-developed embryo, was discovered in northeastern China in 2004. The bird has no egg tooth, indicating that they are a more recent innovation. Prior to the development of the egg tooth, baby birds likely used sharp claws to break through their shells.

References

Vertebrata
Cuvier, 1812

Classes and Clades

See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo.
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Aves
Linnaeus, 1758

Orders

About two dozen - see section below

Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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Sauropsida*
Goodrich, 1916

Subclasses
  • Anapsida
  • Diapsida
Synonyms
  • Reptilia Laurenti, 1768
Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class
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Lacertilia*
Günther, 1867

Families

Many, see text.

Lizards are reptiles of the order Squamata, normally possessing four legs, external ear openings and movable eyelids.
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Serpentes
Linnaeus, 1758

Infraorders and Families
  • Alethinophidia - Nopcsa, 1923
  • Acrochordidae- Bonaparte, 1831

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Teeth (singular, tooth) are structures found in the jaws (or mouths) of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense. The roots of teeth are covered by gums.
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eggshell is a term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats.

The generalized eggshell structure, which varies widely among species, is a protein matrix lined with mineral crystals, usually of a calcium compound such as
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egg tooth is a small protuberance on the beak or nose of vertebrates that are hatched from eggs, i.e., birds and reptiles. Some lizards and snakes develop a true tooth that is shed after use; birds and other reptiles generally develop an analogous epidermal horn that is reabsorbed
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Crocodylidae
Cuvier, 1807

Genera
  • Mecistops
  • Crocodylus
  • Osteolaemus
See full taxonomy.
A crocodile is any species belonging to the family Crocodylidae
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China (Traditional Chinese:
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20th century - 21st century - 22nd century
1970s  1980s  1990s  - 2000s -  2010s  2020s  2030s
2001 2002 2003 - 2004 - 2005 2006 2007

2004 by topic:
News by month
Jan - Feb - Mar - Apr - May - Jun
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