Hi spinster,
The platypus (Ornithorhynchus anatinus), only found in Australia is
considered to be one of the world's most unusual animals/mammals.
Populations occur in Tasmania, Victoria, New South Wales and
Queensland to about as far north as Cooktown, and in South Australia
on Kangaroo Island, where a population was introduced,
It is often described as a living fossil - a furry, warm-blooded,
egg-laying mammal which retains some features of reptiles.
From fossils discovered in Argentina, the ancestors of platypus were
found in South America as well as Australia until at least 60 million
years ago - when the two land masses were still joined together as
part of the southern supercontinent Gondwana.
The species is rare and possibly extinct in the wild.
===============================================================================
Early development and embryology of the platypus
http://mustafa.ingentaselect.com/vl=3564701/cl=55/nw=1/rpsv/catchword/rsl/09628436/v353n1372/s5/p1101
"A feature of the pre-embryonic development of the platypus is the
incomplete meroblastic cleavage. A column of fine yolk spheres extends
from beneath the embryonic blastodisc towards the centre of a yolky
vitellus, as seen in birds. The major expansion of extra-embryonic
membranes occurs after the formation of the primitive streak. The
primitive streak develops within an embryonal area as part of the
superficial wall of the yolk-sac, a feature also shared with
marsupials, birds and reptiles. The full-term, subspheroidal,
intrauterine egg of the platypus has a major axis of about 17 mm and
contains a flat, 19 to 20 somite, neurula-stage embryo which has
prominent trigeminal ganglion primordia. The embryo at this stage is
in a period of rapid modelling of the major early organ primordia of
the nervous system, cardiovascular system, excretory system, and
somite-derived components of the body wall. Soon after laying, five
primary brain vesicles are present, the trigeminal ganglia CN5 as well
as CN7, CN8, CN9, CN10, CN11 and CN12 are well developed. The
alimentary system has an expanded stomach, pancreatic primordia and a
gall bladder. Mesonephric tubules are associated with patent
mesonephric ducts, which empty laterally into the cloaca."
[edit]
"The head is bent at an acute angle to the main body axis. The blunt
upturned snout marks the site of the future oscaruncle and on the
maxilla there is a median primordial papilla representing the egg
tooth. The eye is open with a partly pigmented retinal ring. The
forelimbs have partly separated digits, and the hindfeet are paddles.
Just before hatching the upturned snout contains an oscaruncle and a
sharp recurved median egg tooth. Forelimbs are pronated with separate
digits possessing claw primordia. Portions of the highly vascularized
extra-embryonic membranes are attached to the umbilical region and the
flattened vesicular allantois has a distal region fused with the
chorion. Prominent features of the hatchling are the presence of a
bluntly conical oscaruncle and a translucent, horn-like egg tooth.
These structures are thought to enable the hatchling to extricate
itself from the egg shell. At hatching, the forelimbs exhibit clawed
digits and are capable of digitopalmar prehension. Hindlimbs are still
paddles with digital rays. A prominent yolk-sac navel is present. The
newly hatched platypus..."
[edit]
"The unique morphology and function of extra-embryonic membranes in
the platypus defies comparative staging with human development.
Structures adapted for altricial survival of the platypus hatchling
require the acquisition of functional competence at an earlier stage
of organogenesis than seen in eutherians, although they are
reminiscent of those found in new-born marsupials."
===============================================================================
Platypus
http://home.mira.net/~areadman/plat.htm
Reproduction
"Platypus males are larger than females. Mating occurs once a year,
beginning in late June in the warmer northern parts and in October in
the southern part. The female usually lays two eggs ( the soft
leathery egg resembles a reptiles egg) but may lay up to four and
incubates these against her abdomen (by clasping them with its
tail)for about two weeks in a blocked-off nest at the end of a long
breeding burrow. The young "puggle" have no fur when they hatch. The
female has no teats. Milk is produced in large glands under her skin
which oozes out onto a patch of fur and the young Platypus (puggle)
sucks it up."
===============================================================================
Introduction to Creation Biology
http://creationanswers.net/gensci/INTROBIOL2.HTM
"The duck-billed platypus has multiple examples of multiple
convergence. It has a duck-like bill and lays eggs similar to birds
or reptiles. It also has highly developed sonar and detects
electrical currents in water similar to some fish. It has a poisonous
claw similar to a snake’s fang on it’s hind feet as well, similar to
snakes, though the platypus is a mammal and it suckles it’s young.
The platypus has a unique combination of intelligently designed and
fully functional traits, not a haphazard mix of characteristics that
evolved by chance."
===============================================================================
PLATYPUS (Ornithorhynchus anatinus)
http://home.swiftdsl.com.au/~endangered/platypus.htm
===============================================================================
Several more pages provided at:
http://www.platypuscomputing.com/platwhat.html
http://www.platypuscomputing.com/platytas.html
http://library.thinkquest.org/11420/
http://www.totalretail.com/platypus
Google Search:
platypus fertilization hatching
Best regards,
tlspiegel |
