The Cambrian Explosion

[achilles12604]

Besides the apologist answer that God was responsible for this phenomina by some method, does secular science have a theory as to the cause of this sudden explosion of new life all at once? (Remember I do not fall for that God of Gaps theory)

I am looking for science answer to this mystery. Anyone care to enlighten me?

[otseng]

In addition to all the extant phyla originating in the Cambrian Explosion, there are also many extinct animals that originated then.


"Amplectobelua symbrachiata, an Anomalocarid from the Chengiang fauna in China. The fish-like creature, Myllokunmingia, are among the first vertebrates known."
http://www.nsf.gov/news/mmg/mmg_disp.cf ... 0&from=img

The Anomalocarid is a very interesting creature. It is the largest animal in the Cambrian and also one of the most complex morphologically.

Anomalocaris was a swimming creature which possibly used flexible lobes on the sides of its body to propel itself through the water. Its large head had big eyes with multiple lenses and a round mouth. Two large 'arms' with barb-like spikes were positioned in front of the mouth; Anomalocaris probably used these to grab prey and bring it to its mouth.

For the time in which it lived Anomalocaris was a truly gigantic creature, reaching lengths of an already large 60 cm (2 ft) to a staggering 2 m (6 ft 8 in). Essentially it was the Great White Shark of its time, and the top predator of the Cambrian fauna so far discovered.

http://en.wikipedia.org/wiki/Anomalocaris

We have found several types of Anomalocarids so far:









http://www.trilobites.info/background3.html

This fearsome-looking beast is the largest known Burgess Shale animal. Some related specimens found in China reach a length of six feet! The giant limbs in front, which resemble shrimp tails, were used to capture and hold its prey. A formidable mouth on the undersurface of the head had a squared ring of sharp teeth that could close in like nippers to crack the exoskeleton of arthropods or other prey. With those large eyes and a body half flanked with a series of swimming lobes, this must have been an active, formidable predator!

http://www.nmnh.si.edu/paleo/shale/panomal.htm

[otseng]

The Myllokunmingia is the earliest known vertebrate (and also the first known fish).


http://www.sciencenews.org/pages/sn_arc ... 9/fob1.htm

"It is the oldest vertebrate known, found in rocks of the Cambrian period (530 Ma old). It appears to have a skull and skeletal structures made of cartilage (like lampreys, which are also vertebrates)."
http://en.wikipedia.org/wiki/Myllokunmingia

Characters: Neural crest cells, somites, gills with cartilagenous or bone supports (absent in Myllokunmingia, tripartite brain and paired cranial sense organs, cranium with anterior notochord, semi-circular canal(s), 1 heart, kidneys.
http://www.palaeos.com/Vertebrates/Unit ... a/100.html

[otseng]

The relationship of Xidazoon to the known animal groups is ambiguous. The anterior of this animal resembles an agnathan fish known as a pipiscid, but the segmented tail-like posterior is more like that of an invertebrate, such as an arthropod. Because of its enigmatic nature, Xidazoon has at present been assigned to the pseudo-phylum "Problematica". Nevertheless, this animal has great importance in the study of the evolution of the primitive deuterostomes and protostomes.

http://www.gs-rc.org/repo/repoe.htm

[otseng]

This creature with its five eyes is a strange looking one indeed. Wielding a long flexible proboscis tipped with grasping spines, its reconstructed image was greeted with laughter as a pretty good joke when first presented at a scientific meeting in 1972. The strange-looking reconstruction was soon confirmed, and this creature remains one of the oddities of the Burgess Shale fauna. Opabinia is thought to have lived in the soft sediment on the seabed, although it presumably could have swum after prey using its side lobes. On the bottom, the proboscis could have plunged into sand burrows after worms. Sizes ranged up to 3 inches, plus that unique, amazing 1 inch proboscis!

http://www.nmnh.si.edu/paleo/shale/popabin.htm

The animal was segmented and had a soft-shelled exoskeleton. The head carried an array of five, fully functional eyes that would have given their owner a range of vision of almost 360°, and a long, flexible, hose-like proboscis or snout which appears to be in no way homologous to the head appendages of any other known contemporary lifeform. At the end of the proboscis were grasping spines; these are theorised to have served as a grab to catch prey, which would then be brought to the mouth, which was located underneath the head, behind the base of the proboscis.

The body segments each featured a set of gills and a pair of flap-like appendages that are also dissimilar to other known animals of the time, save Anomalocaris. The three rearmost flaps formed the tail. Unlike known arthropods, the head does not appear to be formed from fused segments. The animal was covered with what seems to be a soft, flexible, uncalcified shell with no joints between the segments. Opabinia has no known relatives, except possibly Anomalocaris.

http://en.wikipedia.org/wiki/Opabinia

[otseng]

The 0.5 to 3 cm-long animal is wormlike - that is, long and narrow with a poorly defined blob, or stain, on one end. This "blob" was arbitrarily designated the 'head' even though it had none of the features generally associated with heads: mouth, eyes, or other sensory organs. The animal has seven pincher-tipped tentacles lined up on one side and seven pairs of jointed spines on the other. Six of the tentacles are paired with spines, while one is in front of the spines. There are also six smaller tentacles which may be configured in three pairs behind the seven larger ones. In addition, there is a flexible, tube-like body extension behind the tentacles.

http://en.wikipedia.org/wiki/Hallucigenia

[otseng]

lobster-like creature with a segmented "tail", a body partially covered by a chitinous shell (or carapace), and a number of walking legs with their associated gill flaps tucked under.

http://www.nmnh.si.edu/paleo/shale/pcanadap.htm

Canadaspis was a genus of crustacean or euarthropod, a benthic feeder that moved mainly by walking and possibly used its biramous appendages to stir mud in search of food. The genus is placed within subclass Phyllocarida in class Malacostraca that includes shrimps and lobsters.

http://en.wikipedia.org/wiki/Canadaspis

[otseng]

"The strange head shield had two pairs of large spines curving back over the body. Two pairs of antennae project forward and the body consists of a large number of segments bearing identically shaped limbs."
http://www.nmnh.si.edu/paleo/shale/pmarella.htm

Marrella itself is a small animal, 2 cm or less in length. The head shield has two pairs of long rearward directed spikes. On the underside of the head are two pairs of antennae, one long and sweeping, the second shorter and stouter. Marrella has a body composed of 24-26 body segments, each with a pair of branched appendages. The lower branch of each appendage is a leg for walking, while the upper branch is a long, feathery gill. There is a tiny, button-like telson at the end of the thorax. It is unclear how the unmineralized head and spines were stiffened. Marrella has one too many antennae pair, three too few cephalic leg pairs, and two too few segments per leg to be a trilobite. It lacks the three pairs of legs behind the mouth that are characteristic of crustacea. The legs are also quite different from those of crustaceans.

http://en.wikipedia.org/wiki/Marella

[otseng]

And the most famous animal from the Cambrian are the trilobites.

The name Trilobite--meaning three lobed one--is in reference to the three longitudinal lobes across their heads (cephalon), consisting of a slightly raised central lobe (the axis) and two flatter pleural lobes on either side. The entire bodies were also divided into three: the head (cephalon), thorax (chest) made up to a group of up to 30 segments and the tail (pygidium). Underneath and rarely preserved are three pairs of legs for the head and paired legs for each pleural groove. Trilobites are the earliest known animal to possess vision. Some possessed eyes and some seem to have no eyes at all, while others possessed beautiful compound eyes capable of 360 degree vision.

http://www.trilobite.com/

Trilobites are extinct arthropods in the class Trilobita. They appeared in the Cambrian period and flourished throughout the lower Paleozoic era before slowly declining to extinction. The last of the trilobites disappeared in the mass extinction at the end of the Permian 250 million years ago (m.y.a.).

Trilobites are very well-known, and possibly the second-most famous fossil group after the dinosaurs. They are the most diverse group of animal species preserved in the fossil record, consisting of nine (or possibly ten) orders and over 15,000 species. The trilobites are currently included along with the Chelicerata in the group Arachnomorpha.

Most were simple, small marine creatures that walked along the seafloor and filtered mud to obtain food.

http://en.wikipedia.org/wiki/Trilobite



"Trilobites are the most diverse group of extinct animals preserved in the fossil record. Nine orders of trilobites are recognized, into which 15,000+ species are placed. "
http://www.trilobites.info/

The Cambrian Period was the time when trilobites reached their peak. The period spanned 38,000,000 years and produced thousands of species. The word Cambrian is of Latin origin and means Wales. Scientists first studied exposed cambrian rock around 1835. The largest Cambrian exposures in North America extend from Southern California to British Columbia, Canada. Trilobites died out in great numbers at the end of this period.

http://www.phacops.com/cambrianperiod.html